Background: Upper extremity arthroscopic surgery is a highly technique-dependent procedure that requires the surgeon to assess difficult cartilage conditions and manage the risk of iatrogenic damage to nerves and vessels adjacent to the joint capsule in a confined joint space, and a device that can safely assist in this procedure has been in demand. Methods: In this study, we developed a small intra-articular ultrasound (AUS) probe for upper extremity joint surgery, evaluated its safety using underwater sound field measurement, and tested its visualization with a phantom in which nerves and blood vessels were embedded. Results: Sound field measurement experiments confirmed the biological safety of the AUS probe’s output, while confirming that sufficient output power level performance was obtained as an ultrasound measurement probe. In addition, images of blood vessels and nerves were reconstructed discriminatively using A-mode imaging of the agar phantom. Conclusions: This study provides proof-of-concept of the AUS probe in upper extremity surgery. Further studies are needed to obtain approval for use in future medical devices. Arthroscopic surgery is an essential, minimally invasive surgical procedure for orthopedic diseases such as meniscus injuries, ligament injuries, osteoarthritis, rheumatoid arthritis, synovitis, free bone fragments, cartilage lesions, and bone tumors. It is also used as an examination technique for accurate assessment of the condition of intra-articular tissues such as cartilage, synovial membrane, and joint ligaments . RecentlThe two most used scanning modes in ultrasound systems are amplitude mode (A-mode) and brightness mode (B-mode), which are the basis for other advanced scanning modes such as Doppler mode and motion mode. In A-mode, the reflected ultrasound is displayed in one-dimensional graphical form and can be used to measure the distance between tissues or tissue thickness, while B-mode represents the amplitude peaks seen in A-mode as dots or pixels of varying brightness. Sequential ultrasound pulses can be sent in different directions to form multiple image lines. This process is completed quickly and repeatedly, producing the typical ultrasound image seen on all systems. This mode is used by many ultrasound systems since it provides intuitive positional information about tissue. For example, scanning in B mode is necessary to prevent tissue damage around joints and to determine the physiological state of articular cartilage, and in this study, we developed an intra-articular ultrasonography probe compatible with B-mode scanning that can be used as an examination tool during arthroscopic surgery and conducted a phantom-based proof-of-concept study to verify the observation accuracy of the device.A schematic diagram of the ultrasonic probe system is shown in The signal from the ultrasonic spike pulser was the output from the ultrasonic element of the probe, and the signal reflected by the target tissue was digitized by the APX-5040 digitizer. The amplitude of the signal was converted to intensity on the time axis by luminance modulation in the image processor, and then the information on the position of the ultrasound beam and the time intensity signal were simultaneously plotted in two dimensions by a controlled synchronous scan through the central processing unit to produce a tomographic image of the target tissue .The higher the output of the ultrasound probe, the better the signal-to-noise ratio, and the clearer the image can be constructed. However, this also increases tissue temperature and the risk of tissue damage. Before generating and evaluating ultrasound examination images, it was necessary to ensure that the output of the ultrasound probe is within a safe range. The ultrasonic sound field oscillating from the probe was measured using an underwater acoustic intensity measuring device . To measure the intensity of the ultrasonic sound of the central portion, the hydrophone was moved up, down, and away from the probe center so that the sound field could be measured in three dimensions. In this way, AIMS was used to find the point of maximum sound pressure at the center axis of the irradiated surface and to measure the maximum value of negative sound pressure measured at that point. From the viewpoint of safety, the most important biological effects of ultrasound are heating and cavitation. This is due to the fact that the heating effect induces thermal denaturation of proteins, and the cavitation effect leads to cell destruction. Therefore, in order to confirm that the heating and cavitation effects are within the acceptable range, we measured the thermal index (TI) and mechanical index (MI) using the method specified in the IEC  62359:2010 standard and confirmed that they are compatible.eq is the equivalent beam diameter aprt is the sound intensity measured with AIMS. The sound field in the XY plane at 0.3 cm from the irradiated surface was measured and the area corresponding to the −12 dB range from the peak sound pressure value was calculated. CTIC is a coefficient and 40 [mW/cm], according to IEC62359 clause 5.4.2.1; P is the output power [mW] measured with a digital phosphor oscilloscope DTDS3054C  and the value was less than 2 mW, which is less than the available measurement resolution, and was substituted into the equation as 2 [mW].The TI is defined as the ratio of the power used to that required to raise the temperature of the tissue by 1 °C and is calculated using the following equation; According to the IEC62359 clause 5.2.2, the MI is calculated using the following formula:lmic use . MI was Next, an agar phantom was prepared for observation experiments. As shown in The ulnar, median, and brachial arteries were collected from the cadaveric arm of the Japanese monkey. The nerve and blood vessels were fixed in the hole of the operculum, the tube was connected from the syringe to maintain the bore of the blood vessel, and the vessel was filled with physiological salt solution. The ulnar nerve and brachial artery were fixed longitudinally using nylon threads at a distance of 10 mm from the center, and the median nerve was fixed at a distance of 20 mm.The agar for medium use  was dissolved in the solution and was cooled to 40 °C, so as not to damage the tissue, and then poured in the mold and solidified; finally, the agar hole was filled with physiological saline and the ultrasonic probe was inserted.Phantom observations confirmed that the nerves had adventitious and funicular structures. The vessel was examined to confirm the lumen structure. Both nerves and vessels were checked for the accuracy of the distance from the probe.In this experiment, sampling was performed at 14 bits and 100 MHz, which is 10 times the probe’s center frequency of 10 MHz. Synchronous addition was performed 32 times to reduce random noise, and sensitivity time control was set to −60 db at 0.5 cm or less and 6 dB at 2.0 cm or more. Since there is a large difference in signal intensity between hard tissue such as the bone, which strongly reflects ultrasonic waves, and blood vessels, which do not reflect ultrasonic waves well, to selectively amplify signals from blood vessels and nerves, dynamic range processing was performed using the equation below.aprt of 9.08 cm2 and The ultrasonic sound field output from the probe was measured using AIMS as shown in Arthroscopy of the elbow, wrist, and hand continues to advance as a valuable clinical technique in hand surgery that facilitates effective diagnosis and surgery, with its minimally invasive nature as a major advantage. However, as arthroscopy becomes more popular, iatrogenic neurovascular complications have become a problem, with the highest frequency of neurological complications reported in 0.2–3.3% for elbow arthroscopy , 0.58% fHowever, in order to combine these technologies with arthroscopic surgery and improve surgical safety, there are limitations such as difficulty in securing working space, difficulty in aligning ultrasound images with endoscopic images, and the need for further knowledge about the consistency with anatomy and pathology, which have led to a demand for an ultrasound probe with multiple frequencies that can be used with the same ease of use as an arthroscopic device .The ultrasound arthroscope device tested in this study offers a promising solution to this problem. It provides intraoperative dynamic information that cannot be obtained with preoperative imaging such as CT or MRI, allowing the surgeon to see anatomical and qualitative tissue changes according to the surgical situation and to perform more accurate surgery. Therefore, the probe is rigid and can be easily manipulated intraoperatively in the same way as conventional endoscopic probe. The use of sector scanning, rather than circular scanning, and a good pulse shape from the transducer helped to maintain a decent spatial resolution, although increasing the density of the transducer elements will likely be necessary to improve the resolution and tissue sorting ability. For example, in arthroscopic ganglionectomy, the ability to perform ultrasonography from within the joint in cases where the stalk cannot be identified by arthroscopy will allow the surgeon to know exactly where in the joint capsule needs to be resected and will also reduce the risk of injury to the radial artery or median nerve. This will also prevent nerve damage and brachial artery damage due to technical reasons in elbow arthroscopic surgery and enable evaluation of the biological activity of articular cartilage and ligament tissue, for example, in the evaluation of free bone fragments in osteochondritis dissecans, leading to more accurate surgery. Furthermore, considering the challenges of securing work space for arthroscopy and the limitations of aligning ultrasound and endoscopic images, it is technically possible to enhance surgical efficiency and safety by using arthroscopic augmented reality (AR) technology ,23 to suOverall, owing to several mechanical and technical limitations, this study could only provide a proof-of-concept validation using an agar phantom. However, this study made it possible to recognize potential complications and limitations in the spatial discrimination capability of current technology. Based on the findings from this study, we are charting a future course that includes a dual focus. The next phase of ultrasonic arthroscopic device development should involve enhancing resolution and tissue sorting by increasing the number of ultrasonic elements. Additionally, the design of the current probes, while suitable for elbow joints, is too large for wrist joints and must be slimmed down. This redesign will require careful planning to add more elements without exceeding space limitations. Simultaneously, we are also preparing for a first-in-human study, marking another significant step in our research trajectory. In the future, ultrasound arthroscopy may help safely perform more difficult procedures in endoscopic surgeries .Nobuo Niimi, Masato Mori, Hitoshi Hirata, Shintaro Oyama: The joint surgery support devices, ultrasonic probes, and joint surgery systems JP-P2021-186308A represent a patent resulting from the work reported in this manuscript.


Our group, involving researchers from different universities in Campania, Italy, has been working for the last twenty years in the field of photonic sensors for safety and security in healthcare, industrial and environment applications. This is the first in a series of three companion papers. In this paper, we introduce the main concepts of the technologies employed for the realization of our photonic sensors. Then, we review our main results concerning the innovative applications for infrastructural and transportation monitoring. In the last three decades, optical fiber sensors (FOS) have shown their increasing importance in a large variety of applications in the fields of both applied engineering and life science, with particular reference to both safety and security ,10,11,12Our multidisciplinary group has been active in this field for the last twenty years, concentrating most of our attention on the usage of photonics and nanophotonics ,26,27,28We have decided to collect, in this paper and in its two companion papers ,65, our Accordingly, this paper is organized as follows. First, we briefly review the basic properties of the optical fiber sensors based on either fiber Bragg gratings (FBGs) or distributed optical effects. Then, we describe a strain sensor based on the use of either bar or QR codes, which is very cheap and easy to use in connection with the Internet of Things (IoT) technologies, although, of course, its characteristics are worse than those of optical fiber sensors. Subsequently, we describe some applications regarding infrastructural monitoring and railways safety. Specifically, we present new systems for measuring the weight of a train based on either point or distributed optical fiber sensors, and verifying if the wheels are perfectly circular or if they have any defects while the train is running. Then, we describe a distributed optical fiber sensor for road traffic monitoring. In the last section, we discuss some innovative systems for anti-intrusion detection in large areas and dangerous gases detection inside tunnels.This section briefly presents the theoretical aspects and mechanisms used in different applications. Here, we discuss the photonic and optical fiber technologies adopted in the proposed applications, including infrastructural and ground transportations monitoring, aerospace and submarine applications , agriculFiber Bragg grating (FBG) is one of the most popular fiber optic devices employed for sensing. Since their first introduction in the late 1970s, FBGs gave rise to several scientific works, commercial products, academic spin-off and private companies . The FBGg period . There dg period . The effg period . As the g period .The key feature of the great success of the FBG technology is the high-multiplexing capability enabling quasi-distributed and multi-parameter sensing . The usuiλ, satisfying the phase-matching condition −3 and 10−2, thus, for coupling to occur at wavelengths in the communication window (1200–1600 nm), the periods are in hundreds of micrometers. Since cladding modes attenuate rapidly while propagating due to fiber bending and absorption due to the coating, the light at the phase-matched wavelengths is lost from the fiber, while nothing is reflected backwards. It should be also noted that the bands have different attenuation values and bandwidth due to distinct coupling coefficients dependent on modal overlap . Th. Th86]. Different scattering phenomena provide a mechanism to turn a conventional optical fiber in a distributed sensor. The common mechanisms employed for temperature and strain sensing are the backward Rayleigh and Brillouin scattering and the forward Brillouin scattering. The latter has recently gained interest due to its capability of recovering the acoustic properties of liquids ; howeverRayleigh scattering arises from the intrinsic inhomogeneities of the fiber material. Since the early days of optical fibers, the Rayleigh backscattering has been exploited in optical time-domain reflectometry (OTDR) for the remote measurement of fiber loss and fault location . DiffereBrillouin scattering results from a Bragg-type reflection of the incident light from a moving diffraction grating, created by a propagating acoustic wave through the elasto-optic effect. The acoustic wave can be generated either spontaneously by thermal excitation (spontaneous Brillouin scattering), or optically via electrostriction (stimulated Brillouin scattering). Stimulated Brillouin scattering attains a higher efficiency than spontaneous Brillouin scattering, therefore it is preferred when a high spatial resolution and/or high accuracy are required. In a single-mode optical fiber, the frequency shift between the incident light and the backward scattered light, known as the Brillouin frequency shift (BFS), is given by When it comes to choosing the most suitable distributed sensing technology for a given application, several factors must be taken into account. A first distinction can be made based on how fast the phenomenon to be monitored evolves: for static or slowly varying phenomena, Brillouin scattering sensors are often preferable, as they permit self-referenced, fading-free measurements . Furthermore, they are capable of extremely long measurement ranges (up to one hundred km and more), making them ideally suited, e.g., in pipeline monitoring or in the early warning of ground movements over large areas. The spatial resolution is typically 1 m, even though some special configurations push the resolution down to the cm or even mm range, at the expense of a longer acquisition time ,93. BrilAnother distinction can be made in terms of fiber access: Rayleigh-based sensors require access to only one end of the optical fiber. Instead, Brillouin-based sensors come in two flavors: those based on stimulated Brillouin scattering, requiring access to both ends of the fiber, and those based on spontaneous Brillouin scattering, requiring access to only one end. Single-ended configurations have the advantage of being fault-tolerant, i.e., they continue to operate even if the fiber breaks at some point. Instead, double-ended configurations fail completely when losing the optical continuity, making their use more critical in harsh environments.The increasing interest in the Internet of Things (IOT), the increase of the automation processes and the more pressing requirements for both safety and security continuously enhance the demand for new sensing systems that are cheaper and simpler ,105,106.The operating principle is quite simple, and it involves the application of a barcode or QR codes on the surface to be monitored (STBM). Indeed, even if the analysis will be performed only by scanning a barcode, it will be clear that our sensor can work with any kind of image. Hereafter, by barcode, we include either the QR code or the barcode itself. After the barcode has been applied on the STBM, its image is stored by using a mobile phone or a camera. By observer, we shall mean either one of these two devices. After the barcode has been applied on the STBM, its image is stored by the observer, and it is considered the reference of the initial conditions of the STBM. By SI, we mean this initial stored image. At a different time, we again take a picture of the applied barcode, and we call this image the actual image (AI). Of course, if the STBM will experience some deformations, even the barcode will be deformed, thus resulting in a difference between the AI and SI, from which a measurement of the STBM deformation can be derived according to the analytical model reported in the next section. The comparison between the two images  is made with an image processing program that transforms the analog image (acquired) into a digital image. This digital image is elaborated and transformed in a signal through which the information of deformation and other information that needs to be measured is extracted. The simplest operational configuration involves the applied image mounted on the surface to be examined and its inspection is performed with a simple cell phone, inside which the stored image has been loaded together with an application capable of comparing the two images and providing a quantitative measure of any deformation observed .The use of a mobile phone is the cheapest method, but it demands an operator that occasionally interrogates the barcode. In order to automate the monitoring process of a structure, a camera is required. In this case, the camera must be equipped with a mini circuit with a memory accompanied by a suitable acquisition and processing system. To this aim, we have designed an active configuration in which the device consists of a parallelepiped of transparent material . On one We discuss the theoretical model of our device for a better understanding of its basic principle. Even if our device can be used with any kind of figure, QR Code or barcode, here we refer to a very simple configuration that can be analyzed with a very simple analytical model by which we can easily estimate the main performance.With reference to B and W are the width of the black and white lines, respectively. This amounts to saying that AI = SI in the initial instant of time. As AI is equal to SI, when we superimpose the two figures, we can see that the total white area is equal to the total black area. When, after a given period of time, the STBM experiences a deformation , the AI becomes different from SI. If we obtain an image that shows the deformation of the AI is normal to the lines of the barcode, then we get the situation shown in Now we discuss the theoretical model of our sensor, referring to a very simplified model that allows us to use a very simplified analytic model that is very useful for understanding the basic principle of our device. We explicitly underline that our device can work with any kind of figure different from that which we are analyzing here. In the barcode above, we have chosen, in the starting configuration, the thicknesses of the black and white lines perfectly equal to each other. More specifically, just after the device has been installed on the structure to be controlled, we haved/2, … = nd/2 and the total length is equal to Md, where M is the number of periods of the barcode. If the AI has no changes, we haveTB and TW are the dimensions of the total black and white lines, respectively.If we superimpose the two images, the resulting width of both the white and black lines will change. In the barcode with no deformation (SI), we have = After the barcode has been deformed to an amount equal to On the other hand, when the IA changes, as in As matter of fact, Equations (8) and (9) are the characteristic equations of our sensor.Some preliminary measurements have demonstrated that our model is correct and that, with no special precautions, the sensitivity is better that 1 mm over 10 m, which is sufficient for civil engineering monitoring. Our model also provides the benefit of a very low price of the proposed sensors. We think that this device is extremely useful for easy monitoring of buildings, bridges and industrial plants, including the fatigue control of mechanical pieces.Rail transport has grown significantly in the last several years for both passengers and goods: for this reason, the need to increase the levels of traffic safety and security, as well as an efficient and economical maintenance policy, are the most important goals for the railway industry . In thisIn the first case, the sensor networks must be installed in all the vehicles, and the systems are complex in terms of mounting, implementation and maintenance. In the second case, instead, the sensors are mounted on the rail or along it, and this type of system returns diagnostic information on rolling stocks passing in the instrumented section and on the rail line, avoiding the installation of devices in every vehicle.By measuring the vertical force generated by the wheel–rail interaction during the normal operation of the trains and the related dynamic track response, information on the quality status of the single wheels, as well as the distribution of weight on the wagons, axles and wheels during normal traffic operation, can be obtained. These kinds of systems are widely used, and they are known as WILD (wheel impact load measurement) and WIM (weight in motion) systems, respectively . The WILUsually, WIM systems are based on rail strain measurements that use strain gauges installed on the rails to obtain signals that are proportional to the applied loads , while tFor this reason, and due to their inherent distinctive advantages, in the last two decades, a significant number of innovative sensing technologies based on fiber optic sensors have proved to be a powerful tool for meticulous assessment of railway systems, including train and track behaviour, by enabling real-time data collection and inspection and detection of structural degradation . Wei et In this framework, we first proposed an optimized package allowing the fastening of the sensor to the foot of the rail, which offers rapid and non-invasive installation, preventing the need to drill the rail . AfterwaThe developed system is the result of an efficient synergy work, which has involved a multidisciplinary team composed by the Electronic and Photonic research group of the University of Sannio, the Optosmart Srl and the Hitachi Rail STS company, which currently has included it in its product portfolio. Here, we report on the main characteristics of the system by focusing the attention on the sensor packaging and the installation kit, the operational principle of the single optical strain sensor during the transit of trains and the data processing developed for WIM and WILD outputs. In addition, we show in-field results returned by one of many systems installed in real scenarios, demonstrating its high performance and its potentiality to increase the safety and to support new methodologies for smart maintenance in the railway industry.The WIM–WILD system is a smart solution entirely based on optical fiber technology and fiber optic sensors and combines the two functionalities by using optical fiber strain gauges based on FBG technology. The sensors are integrated in metallic packages and are clamped to the rail foot between two sleepers by a customized stainless-steel package, designed for detecting the vertical forces generated by the single wheel/rail contact in order to measure both quasi-static and dynamic solicitations imposed on the rail during normal transit.Thanks to the proposed design, the sensor installation is easy and fast: they can be easily mounted on the rail in a few minutes, during normal train service and without any interruption of the traffic. Furthermore, the maintenance and replacement of the sensors can be carried out without interfering with normal train service, and a single sensor can be removed from the rail and put alongside the track for maintenance/replacement without the removal the other sensors. It is designed for the UIC60 and UNI50 rails, but can be customized upon request for any kind of rail.Over the years, different installations in real scenarios have been carried out, and an example of an “in-field” system installation carried out in a Milano subway—San Siro station (UNI50 rail type) is shown in The total number of peaks is the same of the total number of axles: for this reason, the system also performs as the axles counting measurement. Moreover, by measuring the time delay between two pulses, and knowing the wheelbase distance, the speed is calculated. The amplitude of the single peak retrieves information about the weight of the associated train wheel and, therefore, the distribution weight per wheel, axle and wagon. The unbalance or the overload conditions are also carried out by the system.λ from a passing train can be defined as follow  used to convert the strain into impact force and/or weight measurements [P is the load applied on the wheel and g is the gravity acceleration (9.81 m/s2). The sensitivity coefficients of the FBGs depend on the tracks  and the status of the rail in the installation points: for example, in a Milano subway (rail type: UNI50), the coefficients were, on average, equal to 7 kg/pm, which indicates 70 N/pm as the sensitivity in force.As is well known ,135,136,urements :(11)P[kgελ in two parts, as follows [Pλ and ∆Dλ are, respectively, the quasi-static and dynamic component on the raw Bragg wavelength shift, the first obtained with a low pass filter. By converting the wavelength shift in loads, the quasi-static and dynamic forces, respectively related to the weights and the quality status of the rolling surface of the single wheels, are obtained as follows [The raw signal returned by the single FBG contains both quasi-static and dynamic information: the static Bragg wavelength shift (correlated to quasi-static strain induced by a travelling wheel on the track) is strictly related to the wheel weight, while the dynamic Bragg wavelength shift (correlated to the dynamic strain/vibration induced by the traveling wheel) carries important information on the healthy status of the wheel itself. For this reason, the data processing developed for WIM and WILD measurements divides the ∆ follows :(12)Δλε= follows :(13)FP[kIn the case of a defected wheel, a spike appears on the dynamic signal as a result of the impact between the defect and the rail during the normal passing. Therefore, it is clear that the developed system performs all the measurements by using the same sensors and the same hardware installed along the rails: this is a strong advantage with respect to the other competitor systems ,137, whiThe system is equipped with auto-calibration features combined with a full auto-diagnostic architecture able to continuously check the correctness of the measurements and the integrity of the different components of the system. In addition, the system redundancy is implemented to allow correct operation even in the case of 50% sensor failures for both WIM and WILD outputs.In 2007, the Electronic and Photonic research group of the University del Sannio and the Optosmart Srl, have signed an agreement with Hitachi Rail STS  for the development of trackside monitoring systems based on the use of fiber optic sensors to improve safety and security levels of the national and international transportation system.Over the years, thanks to this tight collaboration, different installations and experimental in-field trials have been carried out in various railway scenarios (in both UNI50 and UIC60 rail types), where the trains pass in normal operation , including the one realized in 2014 in Napoli central station, thanks to activities included in a research project PON 01_00142 “Sicurfer” financed by the Italian Ministry of Research (MIUR) , which aIn the following subsection, we report, as examples, some WIM and WILD results in order to demonstrate the capability of the developed system to perform with high accuracy  the load measurements and the wheel defect identification.Here we show the results returned by different in-field systems installed and actively running. In Lastly, in For this kind of measurement, in order to demonstrate the high potentiality of the developed system for defected wheels detection, we report the results obtained during experimental trials carried out in a Marcianise goods station (UIC60 rail type). Here, a test train with a healthy wheel and a flat wheel (with a length of 39 mm and 76 mm) passed over the instrumented rail, and the system, for the single under test wheel, returned a dynamic impact force, as shown in In the Marcianise installation, we used five sensors per side to cover three meters of the rolling surface, but this number can be extended on demand to cover different wheel envelopes . By returning the dynamic signals as a function of the flat length, the capability of the system to detect a defect and to estimate its size is clear: for new wheels, in fact, there are no peaks on the dynamic signal; instead, for flat wheels, a pulse with an amplitude proportional to the flat length is evident. Other reasonable results are returned by the system installed in Napoli central station , where wIn the Milan subway, we acquired the impact forces and the different dynamic observables produced by almost six thousand wheels. For all the selected wheels, we carried out an analysis on the vibration patterns (defect indicator) in order to identify healthy b and outHere we report a brief description of trackside monitoring systems based on the use of fiber optic sensors to improve safety and security levels of railway traffic, developed by the Electronic and Photonic research group of the University del Sannio in close collaboration with Hitachi Rail STS and Optosmart Srl companies. The diagnostic system performs the WIM and WILD functionalities in order to measure the loads applied on the single wheels and to identify defected wheels in real-time. During the description, we showed different in-field results carried out in different installations (for both UNI50 and UIC 60 rail types), demonstrating the correct operation, the high WIM accuracy (less than 2%) and the high reliability in the detection of defected wheels. In other words, we demonstrated the capability of the proposed tool to support new methodologies for enhancing the safety levels in railway traffic.In railway infrastructure monitoring, FBGs have been increasingly used thanks to their numerous advantages over conventional sensors ,138. On We report in P imposed on z = 0 can be expressed as [z is the coordinate along the rail, b is the sleeper width, λ is a characteristic length given by E and J are the Young’s modulus and inertial momentum of the rail, respectively. From Equation (14), the corresponding strain profile can be easily derived through differentiation. Comparing the theoretical and experimental strain profile, the weight of each axle can be properly estimated [While tracking the strain peaks permits us to easily recover the axle distance and the train speed, the estimate of weight (“weight in motion”) is more complex. In our tests, we have adopted the Winkler model , accordiessed as :(14)ηz=Pstimated . It is intenance .Optical fiber sensors have recently been increasingly applied for the detection of seismic vibrations, using an emerging technology known as distributed acoustic sensing (DAS). Thanks to DAS systems, the optical fiber acts as a spatially continuous array of microphones, where each section of the fiber operates as an independent channel . This caRoad traffic monitoring is usually realized using loop detectors, ultrasonic sensors or cameras. While video cameras are effective in achieving precise vehicle tracking and classification , they suAn optical fiber placed under a two-lane two-way state road at a depth of about 40 cm under the road surface was selected for our experiments. The acquired waveforms were grouped in frames, each one corresponding to 30 s of continuous recording. As the vibration produced by each vehicle passage appears as a line segment in the data frame, the Hough transform can be efficiently applied to detect these lines automatically and infer some information about the vehicle, such as its position, speed or class .In The ever-increasing demand of hydrocarbons for fuel applications in turn increases their transportation frequency on both rails and roads. As hydrocarbons have highly flammable and volatile behavior even at low concentrations, a real-time monitoring of leaks during their transportation is of vital importance for both environmental and public health. To date, there is a gap in the use of commercial gas sensors, as they require high operating temperatures and are hardly suitable for harsh, hostile and remote environments . An impoA monitoring system for the detection of liquefied petroleum gas in railway tunnels based on fiber technology was demonstrated in , under tThe core of the system is based on an LPG sensor due to its favorable properties for the development of chemical and biological sensors ,28,85. TThe gas sensor was embedded into a shielding case together with an array of FBGs for the compensation of environmental parameters and mounted inside the tunnel. Connecting optical fibers permitted us to measure the sensor responses from a remote location inside a railway station. The data were acquired using a PC with custom software for the elaboration. A schematic and photos of the monitoring system developed are reported in As an overall assessment, it was always possible to detect gas traces during controlled expositions. Moreover, during normal operation of the railway line, the readings associated with false positives were below 10% of the gas LEL. Finally, it should be remarked that testing was conducted in an unfavorable scenario with diesel trains and errors could probably be reduced in the case of electrical trains.In this section, we present a brief survey on recent progress in fiber optic sensors for the development of intrusion detection systems. The protection of large areas concerns the detection of accesses or unauthorized activities in several applicative scenarios ranging from airports surveillances, railways assets protection up to restricted-access zones in private properties. Nonetheless, the definition of the potential threats and the specific operative conditions related to the application field can strongly affect the characteristics of the identified technological solution. In this regard, the protection of railways assets represents specific requirements and challenges. Some of the concerns associated with the protection of a railway area is related to the unavoidable presence of the railroad tracks, which cannot be obstructed with physical barriers, and to the electromagnetic interferences associated with the train transit. Then, we specifically focus on research activities carried out at the Optoelectronic Division—Engineering Department of the University of Sannio, in collaboration with Ansaldo-STS (now Hitachi) and Ente Autonomo Volturno (EAV), a local railways operator, devoted to the development of a fiber optic intrusion detection system for the protection of railways assets.In the few last decades, to meet the increasing demand for security, worldwide research on intrusion detection sensing systems has grown significantly . The recCommercially available intrusion detection systems make use of several transduction principles , which typically imply different strength and weakness points . The synDespite the necessity of using several solutions based on different technologies, there is still minimal literature available regarding the use of optical fiber sensing technologies for intrusion detection. Nonetheless, compared to conventional technologies, optical fiber sensing technology is potentially well-suited for protecting large areas from unauthorized access with all the additional desirable attributes connected to the fiber optic sensing solutions. In fact, it is well recognized that optical fiber sensors offer specific advantages for advanced security systems because they are small, lightweight, environmentally rugged and having increased sensitivity with respect to traditional sensing techniques ,154. AddAllwood et al.  have recOptical fiber scattering techniques have also been proposed for distributed sensing ,157, demFBG-based systems were also successfully used in security applications for monitoring access points, such as windows and doors  or in feIn the following, we report on the development and field test of a fiber optic sensor for an intrusion detection system in a railway asset. Railway infrastructures represent the transportation system able to underpin the growing demand in transferring both cargo and passengers. In spite of their strategic role in the economy and in daily human life, railways are particularly vulnerable to vandalism and intentional damages. Transport operators have growing concerns about the safety and security of railway facilities, workers and passengers because of the intrinsic difficulty in surveilling all railways assets ,160. SpeIn order to avoid service interruptions and economical losses, efficient security systems in railways areas should detect unauthorized access and undesired intrusions by means of intelligent and autonomous systems. Specific features of railway environments make many conventional solutions unsuitable. A railway asset—such as a service area, a depot for trains or a railway station—cannot be closed with barriers because they would obstruct the passage of authorized staff or passengers. Obviously, the same rail tracks cannot be physically obstructed by physical barriers, such as sensorized fences or taut wire sensors. Other electronic technologies, such as microwave sensors, electric field sensors or ported coaxial cables, suffer from electromagnetic interferences associated with train transit ,160.Recently, the Optoelectronic Division—Engineering Department of the University of Sannio, Benevento proposed an optical fiber security system based on an FBG multiplexing sensing technique to prevent intruders from accessing the railway area without permission. Two technological solutions were developed and tested in realistic operative scenarios. A ribbed mat integrated with FBG strain sensors was installed near the railway track area , whilst In The sensing system is composed of a rubber mat with FBG strain sensors integrated on the lower surface of the mat. An intruder walking on the mat represents a load on the upper surface of the soft rubber mat, endowed by a low Young’s modulus. The FBGs, bonded on the ribbed lower surface of the mat, sense the strain associated with the load and convert the strain to a Bragg wavelength shift. The influence area of a single FBG integrated in the mat has been preliminary characterized in the laboratory. Then a network of 75 equally spaced FBGs has been properly deployed under the mat in order to attain a total coverage of the sensorized area without blind zones.Several trials were carried out in the field to verify the functionality of the system in the presence of intruders walking on the mat. As briefly reported in Similarly, for the rail track access protection, we carried out in-field trials at the Maddaloni–Marcianise freight station  in order to investigate the capability of the sensing system to reveal the presence of an intruder walking close to the rail tracks. Here, the sensing system for the rail track access protection was composed of two FBG accelerometers installed under the tracks . A walkiWe definitively demonstrated the capability of optical fiber sensing technology to offer solutions suitable to protect large areas from unauthorized activities in railway restricted-access zones, such as stations, depots or tunnels. Both installed sensing systems based on accelerometers underneath the tracks or FBGs integrated in a rubber mat represent effective security systems able to protect railway areas from unauthorized activities. The experimental results demonstrated that the intrusion detection system is able to detect a human entering in the protected perimeter (across either the rail tracks or the mat). We have demonstrated the capability of the sensing system to successfully accomplish the detection of intrusion events in a real and “open” scenario. Therefore, optical fiber intrusion sensing systems represent a valuable solution for railway security applications.This paper provides a comprehensive review of our results of in-field applications of optical fiber sensors for infrastructural monitoring and railways safety. In particular, we have presented innovative systems for weight measurement, wheel defect monitoring and gas detection for the railway industry, based either on point-based or distributed optical fiber sensors. We also presented a system for road traffic monitoring using already installed optical fibers. Finally, we have discussed some innovative systems for anti-intrusion detection in large areas and dangerous gases detection inside tunnels. The list of applications is completed by those reported in refs. ,2 publisThe effectiveness of the results above together with other impressive work of the group is proven by the creation of some spin-off companies , working in medical applications and in the design and application of point-based and distributed optical fiber sensors, as well as by the construction of the Center of Nanophotonics and Optoelectronics for Human Health and Industrial Applications (CNOS), which will be completed by April 2023. This Center, built by CERICT (the Competence Center on ICT of Regione Campania), will have a surface of about 3.000 square meters. CERICT is a consortium whose members are the seven Universities of Campania , the National Council of Research of Italy and the Fondazione Pascale, which is one of the highest-regarded Italian Oncological Centers. It is committed to the development of new devices and technologies based on nanophotonics for human health and new industrial applications. A multidisciplinary approach is very often required in order to provide the most suitable solution in a large variety of practical cases. Accordingly, both the team and the technologies are strongly multidisciplinary, as can be seen in To translate the innovative research results into other market products, thus creating new startup companies;To explore new applications to improve both the safety and the security in other fields, such as agrifood, anti-terrorism, biomedical and precision medicine, environment and energy saving;To improve the performance of our devices by increasing the use of both the nanotechnology and the nano materials.The main goals of our future activity can be divided along three main lines:


The crucial role of green finance policies in advocating environmental sustainability cannot be overlooked and has resulted in an increased attention in recent years. Despite their significance, the connection between these policies and economic growth remains disputed among policymakers. This study presents an empirical analysis that aims to uncover the relationship between green finance policies and economic growth rates by analysing the data from 107 cities in China, spanning a period of 16 years from 2003 to 2019. The research focuses on the implications of green finance reforms and innovation pilot zones by employing PSM-DID model to evaluate their effects on the regional GDP by segregating the industries in primary, secondary, and tertiary industries. The results indicate that the green finance reforms and innovation pilot zones are associated with reduced growth rates of regional GDP for secondary industries. However, the growth rates of the tertiary industry are positively affected. Thus, the study offers valuable guidance and recommendations to policymakers and cities seeking to join the pilot zones for green financial reform to foster economic growth while supporting environmental sustainability. The findings of the study also contribute to the understanding of how targeted policy interventions, such as the establishment of pilot zones, can influence economic dynamics at the regional level and describes the complex relationship between policy interventions, economic growth, and industry composition, particularly in the context of environmental sustainability. While comparing the development of green finance in developed countries in the West and China, we find that their development models differ significantly. In the developed countries of the West, represented by the United States and the United Kingdom, a variety of financial institutions and non-governmental organizations are the main participants in green finance, which is mainly based on market mechanisms. Government involvement only occurs when green finance has reached a certain level of development, resulting in a “top-down” development model that is influenced by market demand. It took longer for green finance to take hold in developing countries, represented by China, and the initial creation of the green financial system primarily relied upon government power and was supported by government departments and regulators, resulting in a government-oriented “top-down” approach. There has been an improvement in China's green finance policy system over the past decade, and the author compares and contrasts the timeline of green finance policy development in China .Fig. 1TiThe relevance of green finance in promoting sustainable economic growth has become a subject of academic inquiry, leading to varying conclusions among scholars. For instance, Ref.  researchThe results highlighted a significant and noteworthy suppressive effect of the green financial reform pilot policy on regional national income growth rates. This finding was assessed through a robustness test, which further supported the validity and reliability of the findings. Overall, these outcomes could have implications for policymakers and practitioners alike, as they suggest that the implementation of green financial reform policies may have broader economic consequences within the Chinese context. Moreover, the following study provides a basis for further research to investigate and explore these findings in greater depth, to better understand the underlying mechanisms and implications for future policy making. Also, the study revealed that the primary and secondary industries were significantly suppressed, whereas the tertiary industry was significantly boosted. In light of this finding, cities with diverse industry types may use it as a reference for making policy decisions. As well, the report provides theoretical support and empirical evidence for whether they should choose to apply to become green financial reform test sites. We believe that cities with a predominantly tertiary industry profile should actively seek to become pilot areas for green financial reform.This paper comprises of three essential contributions. Firstly, it investigates the impact of establishing a pilot zone for green financial reform on regional economic growth and industrial structure growth, thereby adding to the empirical research on green pilot zones and green finance. Secondly, the use of a quasi-natural experiment approach through the exogenous event of establishing a pilot zone minimizes endogenous issues, which strengthens the estimation results and provides reliable empirical evidence concerning the connection between green financial reform and regional economic development. Thirdly, this research employs a proximity test that scrutinizes the impact of green finance reform pilot programs on similar cities, accounting for the heterogeneity and significant differences that exist amongst cities. This approach enhances our understanding of the scope and implications of green financial reform policies and their effectiveness in promoting sustainable economic growth. Overall, these findings contribute significantly to the literature on green finance, pilot zones, and the broader environmental and economic policies.The remainder of this paper proceeds as follows: Section 22.1In the past few years, in-depth discussions have taken place between international organizations and governments regarding the role that green finance plays in policymaking at the global level. These discussion reveal that the concept of green finance is understood differently by different institutions. As defined by some, green finance involves investments and financing activities that are related to the environment  and thes2.2The above definitions of green finance may differ. However, there is consensus on the concept that green finance is the financing of economic projects that are beneficial to the environment. Green finance has been proven to be effective in promoting environmental upgradation from various perspectives by scholars. On the basis of micro-enterprises, green investment is considered a successful financial strategy that positively impacts enterprise performance ,13, thus2.3In the introduction to this paper, it is stated that different researchers have come up with different methods and different verification results for determining whether green finance contributes to economic development or not. The most common method of assessing the role of green finance in promoting economic growth ,26, as wMost of the existing studies on the green finance domain focus on analyzing the impact of green financial products, such as green credit, green investment, and green financing, on the environment, enterprise development, and industrial structure. However, there are only a few studies that are conducted from the perspective of green financial policies. Furthermore, a considerable amount of literature on green financial reform pilot zones centers around the role of corporate and regional green innovation, with little attention paid to the pilot effect of green financial reform pilot zones on regional economies and industries. Therefore, this paper's main objective is to examine the effects of green financial reform and innovation pilot zones on regional economic growth and industrial structure through the Propensity Score Matching (PSM) and Difference-in-Differences (DID) modeling techniques. By doing so, this study aims to bridge the gap in the literature and provide a more comprehensive understanding of the efficacy of green financial policies in promoting sustainable economic growth and restructuring regional industries.33.1The State Council approved the first batch of green financial reform and innovation pilot zones in June 2017. Among them are Huzhou and Quzhou in Zhejiang Province, Guangzhou City in Guangdong Province, Ganjiang New Area in Jiangxi Province, Gui'an New Area in Guizhou Province, and Karamay City, Hami City, and Changji Prefecture in Xinjiang Uygur Autonomous Region, a total of eight places in five provinces. This marks the beginning of a new phase for China's green finance, combining a top-down, regional exploratory approach with a top-down, top-level design approach. As of November 2019, Lanzhou New Area in Gansu Province was approved as the country's ninth pilot zone for green financial reform and innovation. This is the only pilot zone for green financial reform and innovation in the Yellow River Basin. The Pilot Zone for Green Financial Reform and Innovation in Chongqing was officially launched in August 2022.This study suggests the use of green reform pilot zones as a natural experiment to evaluate their effect on regional economic growth. The treatment group for this experiment comprises ten cities with green financial reform pilot zones, while cities without green financial reform pilot zones make up the control group. The double difference method is utilized to measure and compare the impact of green reform and innovation pilot zones on economic growth in regions across these two groups. This approach helps in isolating the effects of green financial policies on the economy by controlling for any pre-existing differences between the treatment and control groups. By using this method, the study aims to provide a more comprehensive understanding of the effectiveness of green financial reform policies in promoting sustainable economic development.(1)Except for Quzhou, Huzhou, Guangzhou, Karamay, Changji, Karamay and Chongqing City, not all pilot areas are divided by cities in the pilot area documents. This paper contains a pilot reform area of ten cities. How were they selected? Nanchang City is used as the sample because Jiangxi Ganjiang New Area is located on the bank of Ganjiang River in the north of Nanchang City. The Gui'an New Area is located at the junction of Guiyang City and Anshun City, so Guiyang City and Anshun City are used as samples. The Lanzhou New Area is located north of Lanzhou City in Gansu Province, which is why Lanzhou City was used as a sample. This paper does not include Chongqing in its list of reform pilot zone cities since it was approved in August 2022.(2)Considering the fact that the industrial structure of big cities is complete, it is necessary to select big cities to ensure the comparability between the treatment group and the control group. According to the “2020 China Population Census County-by-County Data” published by the Office of the Seventh National Population Census Leading Group of the State Council on October 22, there are 105 big cities. Of the 105 big cities identified, four are county-level cities and only have a single industrial structure, so that should be eliminated. A total of 107 cities' sample data has been collected after adding 10 cities in the pilot area and subtracting the cities that overlap with the big cities (107 = 105-4 + 10-4).(3)To minimize the influence of external factors such as the COVID-19 pandemic, the research period for this study was selected from 2003 to 2019. The source of the data is the China Urban Statistical Yearbook and the CSMAR database collected over this period, and any missing data are interpolated to ensure completeness. Therefore, a comprehensive set of balanced panel data was compiled and covers 107 major cities in China over the period from 2003 to 2019. By utilizing this data, the study aims to provide a reliable and accurate assessment of the effects of green financial reform pilot zones on economic growth in different regions of China.In order to meet the prerequisites for using the double difference method, the following pre-processing was performed in selecting the sample in this paper:3.2In this paper, green financial policy is used as the explanatory factor and regional economic growth is used as the explained factor, where green financial policy is measured by green financial reform pilot zones and regional economic growth is measured by the growth rate of regional GDP and the share of value added of each industry in GDP. The impact effects of pilot zones on the local economy are identified by comparing the differences in the impact effects of cities before and after they become pilot zones  and cities that are not pilot zones (control group). The double difference model constructed is as follows.trolsit+εgkrit=α+αThe following study employs Propensity Score Matching (PSM) combined with a Difference-in-Differences (DID) model which is advantageous for several reasons. PSM aids addressing the problem of selection bias in observational studies as in non-experimental settings, treatment assignment is not random, and there may be systematic differences between the treatment and control groups does this by balancing the covariates between the treatment and control groups, which helps to reduce bias in the estimates. PSM also provides more accurate estimates of the causal effect of the treatment on the outcome variable as it balances the distribution of observed covariates between the treated and control groups. Since our study combines PSM with DID model so it strengthens the causal inference as it compares the pre and post treatment outcomes allowing for the estimation of causal effects and DID model further isolates the treatment effect from other factors that may affect the outcome over time.3.33.3.1The primary objective of this study is to examine the impact of green financial reform pilot zones on the domestic economy of China. In doing so, the growth rates of gross regional product (gr), the proportion of the value added of the primary industry to GDP (g1r), the proportion of the value added of the secondary industry to GDP (g2r), and the proportion of the value added of the tertiary industry to GDP (g3r) are utilized as explanatory variables. By analyzing these variables, the study aims to explore the influence of the green financial reform pilot zones on both overall economic growth and industrial development in different regions of China. The findings of the study are presented in 3.3.2The explanatory variable of this study is whether it is a green financial reform pilot area. Double differential variables are primarily used to measure it. The did statistic is calculated as the product-term of the dummy variables in the processing period and the dummy variables in the processing group, that is, did = dummy variables in the processing period * dummy variables in the processing group. As long as it is officially approved, this year and later will be valued at 1, while other years will be valued at 0. The value of dids is zero in cities that are not approved as pilot areas.3.3.3To ensure the reliability and robustness of the findings, an array of control variables  have bee44.14.24.2.1In order to further verify the results of the initial analysis, a different approach was employed to handle the time variable. Given that the establishment of the first green financial reform pilot zone occurred in the midyear of 2017, assigning a value of 1 for that year may exaggerate the policy impact on the test area. To account for this concern, the time variable was adjusted to 0.5 for the year of establishment, while the values for the remaining years were assigned by following the baseline regression equation. The regression results after the adjustment are presented in 4.2.2Since the cities selected as pilot zones are not chosen at random, they may be selected because these pilot cities have certain characteristics. Moreover, policies are generally implemented first in pilot demonstration areas, which may already have a fairly high level of economic development. Therefore, in order to further ensure the validity of the regression results and eliminate the influence of the characteristic factors of the pilot cities on the empirical results, it is necessary to find cities similar to the pilot cities in the non-pilot cities for comparison tests. After conducting PSM-DID, 4.2.3To ensure that the DID model is reliable and can be utilized for research purposes, it is imperative to acknowledge that the treatment and control groups conform to the parallel trend assumption. This assumption implies that in the absence of treatment, the difference in outcomes between the two groups is relatively constant over time. By satisfying this basic requirement, it is possible to confidently attribute any observed differences in outcome after the introduction of the treatment to the actual impact of the intervention under consideration. Thus, we carefully evaluated whether the parallel trend assumption holds before attempting to draw conclusions from the DID model results. Using 2014 as a hypothetical year for cities with pilots established in 2017, and so on, the pilots were constructed 3 years before, 2 years before, current, one year after, and two years after the policy was implemented. 4.2.4To ensure that the results obtained from the implementation of the Green Financial Reform and Innovation Test Area are free from the influence of unidentified factors, a placebo test was conducted. This study utilized data from 500 samples taken from 107 cities, with only the first period number (2003) retained for each ID. To match the previous data, a random selection of 10 cities was made from each sampling. The matched cities were then used as a dummy treatment group in the regression, while the remaining cities were considered the control group. The scatter plot in 5The above empirical results could be attributed to a variety of factors. First and foremost, the coefficient of the impact of the green reform pilot policy on regional economic growth is extremely negative, indicating that the implementation of the green financial reform pilot policy will significantly decrease the regional economy's growth rate. This may be due to the fact that under the constraint of the environmental development goal, green financial development may crowd out other financial resources. In other words, environmental requirements have been raised, and investments that previously yielded high returns but did not meet environmental standards are no longer considered viable. As a result, GDP growth slows down and shifts into green, sustainable growth, instead of the crude growth of the past.It is also evident from the second result that there is a restriction on the development of primary and secondary industries. Possibly, this is due to differences in the energy demand structure among different types of industries. Green financial policies may help to promote the transformation of old into new sources of energy. As energy and industrial structure contributes to the ecological footprint of an economy . ConsequThe hypothesis mentioned earlier has been corroborated by its impact on the tertiary industry. The regression analysis performed indicates a noticeable and positive influence of the tertiary sector's growth. Based on these observations, it can be deduced that the adoption of green financial policies seems to be conducive to the expansion and progress of the tertiary industry. Furthermore, the implementation of the green finance reform and innovation policy could aide in the transformation of primary and secondary industries into tertiary ones. While there may be implications from this shift, its potential benefits could lead to greater diversification and sustainability in the long run.The application process for becoming a green financial reform pilot zone is underway in many cities. However, based on the empirical results of this study, green financial reform pilot zones will inhibit regional economic growth. Thus, not all cities are eligible to participate in the pilot program. Aside from that, different cities have different industrial structures as well as different characteristics of their industrial pillars. It is therefore necessary to determine whether to pursue green financial policy support in conjunction with their own development objectives.6In China, ten pilot zones for green financial reform and innovation have been approved across seven provinces, autonomous regions, and municipalities directly under control of the central government. Furthermore, a growing number of cities are seeking to join these designated pilot zones. Against this backdrop, this paper seeks to evaluate whether such pilot zones have the potential to stimulate regional economic growth. To achieve this, the study employs quasi-natural experiments across 107 Chinese cities from 2003 to 2019. By examining the data from these cities, the research aims to assess the relationship between the implementation of pilot zones and their potential impacts on economic growth in the region.Based on the results we deduce that the development of both primary and secondary industries may be restricted, whereas the tertiary sector seems to have gained a significant momentum to grow. These findings held constant after a set of robustness tests were executed, which lends credibility to the empirical link between green financial reform pilot zones and short-term regional economic growth. What makes this discovery noteworthy is that it provides robust and reliable empirical evidence that local authorities can reference when considering whether cities should apply to become pilot zones. Furthermore, these conclusions could inform policy decisions related to the potential advantages and drawbacks of prioritizing the green finance sector over other industrial sectors within a region.Based on the findings of our study we suggest that the central government should designate green financial reform pilot zone based on the industrial structural and characteristics of the cities; those cities with a strong tertiary industry should be given priority for pilot zone designation as our findings suggest that tertiary industry benefits more from the establishment of these pilot zones. The growth momentum in the cities with primary focus on tertiary industries can be further leveraged by giving substantial support for green financial reform and innovation in those cities. The impact of green finance policies should not be viewed as directly promoting economic growth, as their primary goal is to support sustainable and low-carbon development. Therefore, not all cities may be suitable as green reform pilot zones, since it depends on their individual characteristics. Local authorities should exercise caution while implementing green finance policies in cities with primary or secondary industry dominance as the following study suggests that these industries may experience short-term constraints on their economic growth due to the impact of green finance policies. Therefore, policymakers should cautiously evaluate the possible adverse effects and consider alternate strategies to support sustainable development in these industries. Furthermore, it is also important to consider contextual considerations such as the designations and functional positioning of each pilot zone should be tailored to the unique characteristics, resources, industrial structures, economic sizes, and financial development bases of the respective cities as our findings reveal that the effect of pilot zones on the development across industries is subjective to the level at which an industry is operating.However, cities with a primary focus on the primary or secondary industry may be negatively impacted by green finance policies, which could pose a short-term constraint on their economic growth. Therefore, the preference for green finance may not be desirable in these cities. Moreover, governments must account for the different industrial structures, resources, economic sizes, and financial development bases of their designated green finance reform pilot zones, reflecting each unique context. As such, the designations and functional positioning of each pilot zone may require tailoring to best suit local conditions, supply capacity, and demand scales accordingly.One potential limitation of this study is that the sample data only reflects information up to 2019. Given that the first announcement of green financial reform and innovation pilot zones was only released in June 2017, this means that the analysis covered a relatively brief period. Additionally, the COVID-19 pandemic that emerged in 2020 required significant efforts to combat, which created further challenges in measuring the full impact of the pilot zones on the economy. To strengthen the accuracy of future research, longer-term observation of the impact of the pilot zones on economic growth, including more established cities, would be necessary. This would allow for a more comprehensive and precise analysis of the effects of the pilot zones on regional economic development, potentially mitigating the limitations of this study based on limited data.While this paper has made a considerable effort to analyze the impact of green financial reform pilot zones on regional economic growth, there are several potential areas for future research that could enhance the study's strength. One such area is to conduct greater in-depth analysis into the different impacts of pilot zones on regions with varying industrial structures as the following study does not consider the pilot zones based on the industrial structures. This could involve further categorization of cities based on their specific industrial makeup, allowing for more detailed and precise insights into the relationship between green finance policies and economic performance as this will extend the following study further. Furthermore, since some of the pilot cities are also part of other policy experiments, such as low-carbon city pilots, it may be difficult to entirely eliminate any possible influences of these factors in our study throughout the robustness test stage. Therefore, it would be essential to exclude potential effects of unaccounted variables more thoroughly in future studies. As some of the cities included in our study are in embryonic stage and the green finance reform and innovation pilot zone is still undergoing exploration and promotion stages, and it may take more time to determine whether its potential to provide economic growth stimuli is limited. Thus, over time, the potential complexities and multidimensional impacts of green finance policies may further unfold, and this would provide more opportunities for research expansion.Cheng Hu: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.Yan Wang: Contributed reagents, materials, analysis tools or data.This work was supported by the [Young Talent Project Fund of Science and Technology Research Program of Hubei Provincial Education Department] (Q20223101).The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.