Fiber bragg grating / fiber white light interference / fiber laser interference hybrid measurement system

Abstract

The invention discloses a fiber bragg grating / fiber white light interference / fiber laser interference hybrid measurement system, and belongs to the technical field of fiber sensing. According to the invention, the wavelength division is carried out on the whole spectral range through the wavelength division multiplexing technology, and the wavelengths used for fiber grating measurement, fiber white light interference measurement and fiber laser interference measurement respectively occupy a part of the spectrum; the wavelength of the fiber bragg grating is measured through a spectrum acquisition technology, the cavity length of the Fabry-Perot interferometer is obtained through a white light interference measurement technology, and the cavity length change of the Fabry-Perot interferometer is obtained through a laser interference measurement technology; and simultaneous measurement of a plurality of channels is realized through a space division multiplexing technology. The optical fiber grating measurement and the optical fiber Fabry-Perot interferometer measurement are combined, various physical quantities including static physical quantities (such as temperature, static strain and static pressure) and dynamic physical quantities (such as dynamic strain, dynamic pressure and vibration) can be simultaneously measured on one optical fiber, and the measurement frequencies of the static physical quantities and the dynamic physical quantities are 50Hz and 200kHz respectively.

Description

Technical Field

[0001] This invention relates to a hybrid measurement system of fiber optic grating / fiber white light interferometry / fiber laser interferometry, belonging to the field of fiber optic sensing technology. Background Technology

[0002] Structural health monitoring of aerospace vehicles, large building structures, military products, and geological environments has significant application value in maintaining facilities and equipment, reducing safety accidents, and improving production efficiency. Simultaneous measurement of multiple parameters such as temperature, strain, pressure, and vibration is essential in structural health monitoring. Fiber optic sensors, with their advantages of electromagnetic interference resistance, high sensitivity, small size, high temperature and pressure resistance, and corrosion resistance, play a crucial role in the measurement of various physical quantities. Among them, fiber Bragg gratings (FBGs) are widely used for temperature and strain measurement, while fiber optic intrigued Fabry-Perot interferometers (EFPIs) are widely used for strain, pressure, and vibration measurement. Furthermore, one EFPI can be well integrated with multiple FBGs on the same fiber to form a fiber optic EFPI / FBG composite sensor, enabling simultaneous measurement of multiple parameters such as strain, temperature, pressure, and vibration.

[0003] The demodulation of fiber optic sensors directly affects the demodulation accuracy and dynamic range of the measured parameters. Designing a measurement system that simultaneously demodulates fiber Bragg gratings and fiber Fabry-Perot interferometers is crucial for achieving simultaneous measurement of strain, temperature, pressure, and vibration signals. However, these measured physical quantities include both static and dynamic quantities, and fiber Bragg gratings and fiber Fabry-Perot interferometers also have different spectral characteristics. Therefore, different measurement techniques are needed for different measured quantities and different fiber optic sensors to meet the measurement requirements.

[0004] Currently, most measurements of fiber optic EFPI / FBG composite sensors are based on white light measurement techniques using broadband light sources and spectrometers. However, spectrometers are bulky, expensive, and have slow response speeds, making this method only suitable for measuring static physical quantities and laboratory use. To achieve simultaneous measurement of static and dynamic physical quantities using fiber optic EFPI / FBG composite sensors, many researchers have proposed demodulation schemes. In 2001, Zeng Xiangkai et al. from Chongqing University proposed a scheme that uses the reflection spectra of FBG and EFPI obtained from a broadband light source with a center wavelength of 1.55 μm to measure temperature and static strain, respectively, and uses the reflection spectra of EFPI obtained from a broadband light source with a center wavelength of 1.31 μm to measure the vibration of the Fabry cavity. However, the demodulation speed of the vibration signal is only 50 Hz (Zeng Xiangkai, Rao Yunjiang, Yu Banmei, Wang Yiping, Zhu Tao, Ran Zengling. Research on new technology for simultaneous measurement of fiber strain, temperature, and vibration [J]. Acta Photonica Sinica, 2001, (10): 1254-1258.). In 2007, Deng Yinbei of Zhengzhou University injected a wavelength scanning fiber laser source and a laser diode source into the same fiber EFPI / FBG sensor using a wavelength division multiplexer. The FBG and EFPI reflection spectra in the wavelength range of 1525-1565nm were used to measure temperature and stress, respectively, while the 1305nm EFPI single-wavelength laser interference signal was used to measure vibration. The measurement frequency can reach 1MHz. However, due to the use of single-wavelength laser demodulation, it has disadvantages such as small dynamic range, difficulty in stabilizing the static operating point, and susceptibility to light source power disturbance. In addition, the data is stored in the computer before processing and cannot be measured in real time (Deng Yinbei. Fiber Optic Sensor for Simultaneous Measurement of Stress, Temperature and Vibration Frequency [J]. Optoelectronic Technology Application, 2007, (05): 35-38.). In 2017, Feng Maoqiao et al. of Chengdu Kaitian Electronics Co., Ltd. proposed a demodulation system based on an integrated semiconductor tunable laser for fiber Bragg gratings (FBGs) and fiber Fabry-Perot (FBP) sensors. The system boasts high integration, small size, versatility, and strong reusability. However, it can only demodulate one type of sensor (FBG or FBP sensor) per channel, lacking the ability to multiplex two fiber sensors on the same fiber (Feng Maoqiao et al. FP / FBG Fiber Optic Sensor Demodulation System: Chinese Patent, CN107024236B. 2017-08-08). It is evident that to achieve simultaneous demodulation of multiple parameters and multiple channels in the fiber EFPI / FBG composite sensor and to realize its application in practical engineering, further efforts are needed in areas such as cost-effectiveness of the instrument, real-time signal acquisition and processing, and high precision and speed of the demodulation method. Summary of the Invention

[0005] To address the challenge of simultaneously measuring multiple parameters across multiple channels using fiber gratings and fiber Fabry-Perot interferometers, this invention provides a hybrid measurement system combining fiber grating / fiber white-light interferometry / fiber laser interferometry. This system utilizes wavelength division multiplexing (WDM) to divide the entire spectral range into wavelengths, with each wavelength representing a portion of the spectrum for fiber grating measurement, fiber white-light interferometry, and fiber laser interferometry. The system measures the wavelength of the fiber grating using spectral acquisition techniques, obtains the cavity length of the Fabry-Perot interferometer using white-light interferometry, and obtains the cavity length variation of the Fabry-Perot interferometer using laser interferometry. Simultaneous measurement across multiple channels is achieved through spatial division multiplexing. This system combines fiber grating measurement and fiber Fabry-Perot interferometry, enabling the simultaneous measurement of multiple physical quantities on a single fiber, including static physical quantities (such as temperature, static strain, and static pressure) and dynamic physical quantities (such as dynamic strain, dynamic pressure, and vibration), with measurement frequencies of 50 Hz and 200 kHz, respectively.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system disclosed in this invention includes a three-wavelength laser source, a wavelength scanning source, a first wavelength division multiplexer, a second wavelength division multiplexer, a third wavelength division multiplexer, a fourth wavelength division multiplexer, a fifth wavelength division multiplexer, a first coupler, a 1×N coupler, a circulator, a fiber optic sensor, an etalon, a first photodiode, a second photodiode, and a third photodiode.

[0008] The light from the three-wavelength laser source is combined into a single optical fiber after passing through a three-channel first wavelength division multiplexer (WDM), and then enters the second WDM. The light from the wavelength scanning source passes through a first coupler; a portion of this light enters the second WDM and combines with the three-wavelength laser light to form a combined beam with two wavelength ranges. This combined beam then enters a 1×N coupler via an optical fiber. The remaining light enters the third WDM, where the preset wavelength light is removed to obtain the marker light. The marker light enters an etalon, resulting in transmitted light with a comb filter structure. The transmitted light is converted into an electrical signal by a first photodiode, serving as the reference signal for demodulating the fiber optic grating / fiber white light interference signal.

[0009] The combined light beam is split into N outputs by a 1×N coupler. Each of the N outputs includes a circulator and an optical fiber sensor. The circulator has three ports. The combined light passes through the circulator into the optical fiber sensor and is reflected. The reflected light, carrying information about the measured physical quantity, is output through the other port of the circulator. Each output beam enters a fourth wavelength division multiplexer, where the two wavelength bands of the output beam are separated. The two output beams are a wavelength scanning light signal and a three-wavelength laser interference signal, respectively. The wavelength scanning light signal is detected by a second photodiode and converted into an electrical signal. The three-wavelength laser interference signal is split into three beams by a fifth wavelength division multiplexer, each detected by three third photodiodes and converted into an electrical signal.

[0010] Furthermore, the wavelength scanning light source controls the scanning output of the tunable wavelength through a triangular wave scanning voltage. The triangular wave scanning voltage is generated by a direct digital frequency synthesizer (DDS) driven by an ARM processor. At the same time, the DDS also synchronously generates a square wave signal, i.e., a sampling synchronization signal, for synchronization in subsequent data processing.

[0011] Furthermore, the wavelength range of the wavelength scanning light source is in the C+L band, while the three wavelengths of the three-wavelength laser light source are in the L band, and the wavelength ranges of the two light sources do not overlap.

[0012] Furthermore, the fiber optic sensor is a single or multiple fiber optic gratings, a single fiber Fabry-Perot interferometer, or a tandem composite sensor formed by a single or multiple fiber optic gratings and a single fiber Fabry-Perot interferometer.

[0013] Furthermore, the electrical signals obtained from the first photodiode, the second photodiode, and the third photodiode are converted from analog to digital using an AD acquisition card, and then sent to the FPGA signal demodulation module for demodulation along with the sampling synchronization signal.

[0014] Furthermore, the wavelength calibration of the reflection spectrum signal of the fiber optic sensor detected by the second photodiode is performed using the transmission spectrum signal of the standard etalon with a marked wavelength detected by the first photodiode. Each transmission peak of the standard etalon transmission spectrum signal has a fixed wavelength. Combined with the wavelength of the marker light erasure, the wavelength value corresponding to each transmission peak is accurately identified, thereby realizing the wavelength calibration of the reflection spectrum signal of the fiber optic sensor.

[0015] Furthermore, the wavelength-calibrated sensor reflection spectrum signal is divided into wavelengths. A portion of the reflection spectrum in the short wavelength range is used for wavelength demodulation of the fiber optic grating, while another portion of the reflection spectrum in the long wavelength range is used for cavity length demodulation of the fiber optic Fabry-Perot interferometer. Peak-finding demodulation algorithm is used for demodulation of the fiber optic grating, and white light interferometry demodulation algorithm is used for demodulation of the fiber optic Fabry-Perot interferometer.

[0016] Furthermore, a three-wavelength symmetrical demodulation algorithm is used to demodulate the three laser interference signals detected by the three third photodiodes, thereby achieving high-speed measurement of the cavity length change of the fiber Fabry-Perot interferometer.

[0017] Furthermore, the wavelength range of the wavelength scanning light source is 1520-1580 nm, with the 1520-1532 nm wavelength range used for fiber grating measurements and the 1532-1580 nm wavelength range used for white-light interferometry measurements of the fiber Fabry-Perot interferometer. Peak-finding demodulation algorithms and interference order methods are used to demodulate the wavelength of the fiber grating and the absolute cavity length of the fiber Fabry-Perot interferometer, respectively, at a demodulation speed of 50 Hz. The wavelengths of the three-wavelength laser sources are 1585.43 nm, 1587.14 nm, and 1588.83 nm, respectively. A three-wavelength symmetrical demodulation algorithm is used to demodulate the relative cavity length variation of the fiber Fabry-Perot interferometer, at a demodulation speed of 200 kHz.

[0018] A method for simultaneous measurement of multiple channels using a hybrid measurement system of fiber optic grating / fiber white light interferometry / fiber laser interferometry is proposed: each channel simultaneously measures multiple parameters. The wavelength of the fiber optic grating is used to measure temperature or static strain, the absolute cavity length of the fiber optic Fabry-Perot interferometer demodulated by white light interferometry is used to measure static strain or static pressure, and the relative cavity length change of the fiber optic Fabry-Perot interferometer demodulated by laser interferometry is used to measure dynamic strain, dynamic pressure, or vibration.

[0019] The operating method of the fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system disclosed in this invention is as follows: Three-wavelength laser sources with a wavelength range in the L-band pass through a three-channel first wavelength division multiplexer and are then combined into a single optical fiber before entering a second wavelength division multiplexer. A wavelength scanning light source with a wavelength range in the C+L-band passes through a first coupler, and a portion of the light enters the second wavelength division multiplexer to combine with the three-wavelength lasers, forming a combined light with two wavelength ranges. This combined light then enters a 1×N coupler via an optical fiber. The remaining portion of the light enters a third wavelength division multiplexer, where the light of a preset wavelength is removed to obtain a marker light. The marker light enters an etalon to obtain transmitted light with a comb filter structure. The transmitted light is converted into an electrical signal by a first photodiode, serving as a reference signal for demodulating the fiber grating / fiber white light interferometry signal. The combined light is split into N outputs by the 1×N coupler. Each of the N outputs includes a circulator and a set of fiber optic sensors. The sensors can be single or multiple fiber gratings, a single fiber Fabry-Perot interferometer, or a composite sensor consisting of single or multiple fiber gratings and a single fiber Fabry-Perot interferometer. The converging light enters the fiber optic sensor through a circulator and is reflected. The reflected light, carrying information about the measured physical quantity, is output through another port of the circulator. Each output light enters a fourth wavelength division multiplexer, where the two wavelength bands of the output light are separated. The two output beams are then a wavelength scanning light signal and a three-wavelength laser interference signal, respectively. The wavelength scanning light signal is detected by a second photodiode and converted into an electrical signal. The three-wavelength laser interference signal is split into three beams by a fifth wavelength division multiplexer, each detected by a third photodiode and converted into an electrical signal. The wavelength scanning light source is controlled by a triangular wave scanning voltage generated by a DDS driven by an ARM processor. Simultaneously, the DDS also generates a sampling synchronization signal for synchronization during subsequent data processing. The signal detected by the photodiode is converted from digital to analog using an AD acquisition card and sent to the FPGA signal demodulation module along with the sampling synchronization signal for demodulation. The wavelength of the fiber grating, the cavity length of the fiber Fabry-Perot interferometer, and the cavity length variation of the fiber Fabry-Perot interferometer are demodulated by fiber grating measurement based on wavelength scanning light source and absolute measurement by white light interferometry, and relative measurement by laser interferometry based on three wavelength laser source. This enables the simultaneous measurement of multiple physical quantities such as temperature, static strain, static pressure, dynamic strain, dynamic pressure, and vibration.

[0020] Beneficial effects:

[0021] 1. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system disclosed in this invention can connect multiple fiber gratings and a fiber Fabry-Perot interferometer in series on a single optical fiber. By using wavelength division multiplexing technology, the wavelengths of the entire spectral range are divided, and the wavelength ranges used for fiber grating measurement, fiber white light interferometry measurement, and fiber laser interferometry measurement each occupy a portion of the spectrum. Then, the wavelength of the fiber grating, the cavity length of the fiber Fabry-Perot interferometer, and the cavity length change of the fiber Fabry-Perot interferometer are measured by spectral acquisition technology, white light interferometry technology, and laser interferometry technology, respectively. This enables the simultaneous measurement of multiple physical quantities on the same optical fiber.

[0022] 2. The fiber optic grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system disclosed in this invention demodulates the reflection spectrum of the sensor obtained by the FPGA signal demodulation module. The demodulation frequency of the wavelength of the fiber optic grating and the cavity length of the fiber Fabry-Perot interferometer is 50Hz, and the demodulation frequency of the cavity length change of the fiber Fabry-Perot interferometer is 200kHz. It can realize real-time measurement of static physical quantities (such as temperature, static strain and static pressure) and dynamic physical quantities (such as dynamic strain, dynamic pressure and vibration).

[0023] 3. The fiber grating / fiber white light interferometer / fiber laser interferometer hybrid measurement system disclosed in this invention achieves spatial multiplexing through a 1×N coupler, thereby enabling simultaneous measurement of multiple channels. Each channel can be connected to a set of fiber gratings and fiber Fabry-Perot interferometers, which greatly improves the multiplexing capability and measurement efficiency of the measurement system.

[0024] 4. The fiber optic grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system disclosed in this invention aims to integrate the proposed measurement system into a single chassis, making the instrument more miniaturized and cost-effective, and suitable for practical engineering applications. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the hybrid measurement system for fiber grating / fiber white light interferometry / fiber laser interferometry proposed in this invention.

[0026] Figure 2 The spectral range diagram for the system design is shown, from left to right, representing the wavelength ranges used for fiber grating measurement, white light interferometry, and laser interferometry.

[0027] Figure 3 This is a schematic diagram of a composite sensor consisting of a fiber optic grating and a fiber optic Fabry-Perot interferometer connected in series.

[0028] Figure 4 The standard etalon transmission spectrum and fiber optic grating / fiber Fabry-Perot interferometer reflection spectrum are erased within the range of the collected scanning wavelength light.

[0029] Figure 5 It consists of three laser interference signals.

[0030] Figure 6 The cavity length of the fiber Fabry-Perot interferometer and the wavelength of the fiber grating are demodulated within 1 second.

[0031] Figure 7 The dynamic cavity length change of the fiber Fabry-Perot interferometer demodulated within 0.02s.

[0032] Among them, 1—three-wavelength laser source, 2—wavelength scanning source, 3—first wavelength division multiplexer, 4—second wavelength division multiplexer, 5—third wavelength division multiplexer, 6—fourth wavelength division multiplexer, 7—fifth wavelength division multiplexer, 8—first coupler, 9—1×N coupler, 10—circulator, 11—fiber optic sensor, 12—etalon, 13—first photodiode, 14—second photodiode, and 15—third photodiode. Detailed Implementation

[0033] The invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0034] like Figure 1 As shown, in the embodiments described below, the fiber optic grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system includes: a three-wavelength laser source 1, a wavelength scanning source 2, a first wavelength division multiplexer 3, a second wavelength division multiplexer 4, a third wavelength division multiplexer 5, a fourth wavelength division multiplexer 6, a fifth wavelength division multiplexer 7, a first coupler 8, a 1×N coupler 9, a circulator 10, a fiber optic sensor 11, an etalon 12, a first photodiode 13, a second photodiode 14, and a third photodiode 15. To realize the practical application of the proposed hybrid measurement system, a prototype was fabricated, except... Figure 1 The prototype also includes a power module, a signal demodulation module, and a network interface board, as mentioned in the specifications. Figure 1 The optical path system shown in the wireframe is encapsulated in a box and mounted on the prototype's base plate. The power module, signal demodulation module, and network interface board are also mounted on the prototype's base plate as plug-in boards. The function of the network interface board is to transmit the wavelength and cavity length values ​​demodulated by the FPGA signal demodulation module to the host computer in real time via the Ethernet interface for display and subsequent data processing.

[0035] In practical applications, the selected three-wavelength laser light sources have wavelengths of 1585.43nm, 1587.14nm, and 1588.83nm, respectively. The wavelength range of the wavelength scanning light source is 1520-1580nm. The frequencies of the first wavelength division multiplexer 3 and the fifth wavelength division multiplexer 7 are both 100GHz. The wavelength bands of the second wavelength division multiplexer 4 and the fourth wavelength division multiplexer 6 are both 1580nm. The wavelength erased by the third wavelength division multiplexer 5 is 1529.5nm. The fiber optic sensor can be a series connection of multiple fiber optic gratings and a fiber optic Fabry-Perot interferometer. Each channel can simultaneously realize 50Hz static physical quantity measurement and 200kHz dynamic physical quantity measurement.

[0036] To enable the measurement of different physical quantities by different sensors, the entire spectral range was divided, such as... Figure 2 As shown, wavelength scanning light in the range of 1520-1532nm is used for wavelength measurement of fiber gratings, wavelength scanning light in the range of 1532-1580nm is used for white light interferometry of fiber Fabry-Perot interferometer, and three wavelengths of laser light in the range of 1585-1588nm are used for laser interferometry of fiber Fabry-Perot interferometer.

[0037] A sensor 11 is connected to one of the channels. Sensor 11 consists of four fiber gratings and a fiber optic Fabry-Perot interferometer connected in series. Figure 3 As shown, the fiber optic Fabry-Perot interferometer is formed by an optical fiber end face and a wafer surface coated with a reflective film bonded to piezoelectric ceramic (PZT). The cavity length of the Fabry-Perot cavity can be dynamically changed by applying a sinusoidal signal to the PZT using a signal generator. In this embodiment, the frequency of the sinusoidal signal is 1 kHz. Due to the low reflectivity of the optical fiber end face and the reflective film on the wafer, the light reflected from the two reflecting surfaces of the Fabry-Perot cavity forms a two-beam interference.

[0038] The first photodiode 13 and the second photodiode 14 convert the transmission spectrum of the standard etalon and the reflection spectrum of the fiber optic sensor into electrical signals, respectively. These signals are then converted from analog to digital by an AD acquisition card, resulting in the following spectral signals: Figure 4As shown, the wavelength range of the wavelength scanning light is 1520-1580 nm, with the etalon transmission peak signal at 1529.5 nm (approximately corresponding to the 7700th sampling point in the figure) being removed. The wavelength of the etalon transmission peak is fixed; in this embodiment, the wavelength difference between the two transmission peaks is 0.8 μm. Based on this removed transmission peak wavelength, the wavelengths of all transmission peaks can be identified, thereby achieving wavelength calibration of the fiber optic sensor's reflection spectrum signal. The fiber optic sensor's reflection spectrum signal shows that the sensor is connected in series with four fiber gratings and a fiber Fabry-Perot interferometer. The fiber optic sensor's reflection spectrum in the 1520-1532 nm range (approximately corresponding to the 7500th to 9000th sampling points in the figure) is used for wavelength demodulation of the fiber gratings, and the fiber optic sensor's reflection spectrum in the 1532-1580 nm range (approximately corresponding to the 500th to 7500th sampling points in the figure) is used for cavity length demodulation of the fiber optic interferometer, with a demodulation rate of 50 Hz.

[0039] Figure 5 The three laser interference signals of the fiber Fabry-Perot interferometer, detected by three third photodiodes 15 and converted by AD, are obtained by a three-wavelength symmetrical demodulation algorithm with a phase difference of 120° between any two interference signals. The cavity length change of the fiber Fabry-Perot interferometer is obtained by the three-wavelength symmetrical demodulation algorithm with a demodulation speed of 200kHz.

[0040] The demodulation results of the absolute cavity length and the wavelengths of the four fiber gratings of the fiber optic Fabry-Perot interferometer within 1 second are as follows: Figure 6 As shown, each sensor has 50 demodulation values ​​in 1 second, which corresponds to a demodulation frequency of 50Hz. The wavelengths of the four fiber gratings are 1523.1712nm, 1525.1170nm, 1526.9328nm and 1530.1090nm, respectively, and the cavity length of the fiber Fabry-Perot interferometer is 159.5360μm.

[0041] The demodulation results of the relative cavity length variation of the fiber optic Fabry-Perot interferometer within 0.02 s are as follows: Figure 7 As shown, there are 4000 demodulation values ​​within 0.02s, which corresponds exactly to the dynamic signal demodulation frequency of 200kHz. The 0.02s includes 20 periodic signals, which correspond to the vibration frequency of 1kHz, consistent with the frequency of the sinusoidal signal actually applied to the fiber optic Fabry-Perot interferometer.

[0042] After calibrating the sensor's sensitivity, the measured physical quantity is calculated based on the measured wavelength and cavity length, enabling simultaneous multi-channel measurement of static physical quantities (such as temperature, static strain, and static pressure) and dynamic physical quantities (such as dynamic strain, dynamic pressure, and vibration).

[0043] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hybrid measurement system for fiber optic grating / fiber white light interferometry / fiber laser interferometry, characterized in that: It includes a three-wavelength laser source (1), a wavelength scanning source (2), a first wavelength division multiplexer (3), a second wavelength division multiplexer (4), a third wavelength division multiplexer (5), a fourth wavelength division multiplexer (6), a fifth wavelength division multiplexer (7), a first coupler (8), a 1×N coupler (9), a circulator (10), an optical fiber sensor (11), a standard etalon (12), a first photodiode (13), a second photodiode (14), and a third photodiode (15); The light from the three-wavelength laser source (1) is combined into a single optical fiber after passing through the first wavelength division multiplexer (3) of the three channels, and then enters the second wavelength division multiplexer (4); the light from the wavelength scanning source (2) passes through the first coupler (8), and part of the light enters the second wavelength division multiplexer (4) and is combined with the three-wavelength laser to form a combined light with two wavelength ranges. The combined light enters the 1×N coupler (9) through the optical fiber; the other part of the light enters the third wavelength division multiplexer (5), where the light of the preset wavelength is removed to obtain the marker light; the marker light enters the etalon (12) to obtain the transmitted light with a comb filter structure; the transmitted light is converted into an electrical signal by the first photodiode (13) and serves as the reference signal for demodulating the fiber grating / fiber white light interference signal; The converging light is split into N outputs by a 1×N coupler. Each of the N outputs includes a circulator (10) and an optical fiber sensor (11). The circulator (10) has three ports. The converging light enters the optical fiber sensor (11) through the circulator (10) and is reflected. The reflected light carrying the measured physical quantity information is output through the other port of the circulator (10). Each output light enters the fourth wavelength division multiplexer (6). The two wavelength bands of the output light are separated. The two output light segments after separation are the wavelength scanning light signal and the three-wavelength laser interference signal, respectively. The wavelength scanning light signal is detected by the second photodiode (14) and converted into an electrical signal. The three-wavelength laser interference signal is split into three beams by the fifth wavelength division multiplexer (7) and detected by three third photodiodes (15), respectively, and converted into electrical signals.

2. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 1, characterized in that: The wavelength scanning light source (2) controls the scanning output of the tunable wavelength through the triangular wave scanning voltage. The triangular wave scanning voltage is generated by the ARM processor driving the direct digital frequency synthesizer (DDS). At the same time, the DDS also generates a square wave signal, i.e., a sampling synchronization signal, for the synchronization of subsequent data processing.

3. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 1, characterized in that: The wavelength range of the wavelength scanning light source (2) is in the C+L band, and the three wavelengths of the three-wavelength laser light source (1) are in the L band. The wavelength ranges of the two light sources do not overlap.

4. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 1, characterized in that: The fiber optic sensor (11) is a single or multiple fiber optic gratings, a single fiber optic Fabry-Perot interferometer, or a series composite sensor formed by a single or multiple fiber optic gratings and a single fiber optic Fabry-Perot interferometer.

5. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 1, characterized in that: The electrical signals obtained by the first photodiode (13), the second photodiode (14) and the third photodiode (15) are converted from analog to digital by an AD acquisition card and sent to the FPGA signal demodulation module for demodulation together with the sampling synchronization signal.

6. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 1, characterized in that: The wavelength calibration of the reflection spectrum signal of the fiber optic sensor detected by the second photodiode (14) is performed using the standard etalon transmission spectrum signal with a marked wavelength detected by the first photodiode (13). Each transmission peak of the standard etalon transmission spectrum signal has a fixed wavelength. Combined with the wavelength of the marker light erasure, the wavelength value corresponding to each transmission peak is accurately identified, thereby realizing the wavelength calibration of the reflection spectrum signal of the fiber optic sensor.

7. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 6, characterized in that: The wavelength-calibrated sensor reflection spectrum signal is divided into wavelengths. A portion of the reflection spectrum in the short wavelength range is used for wavelength demodulation of the fiber optic grating, while another portion of the reflection spectrum in the long wavelength range is used for cavity length demodulation of the fiber optic Fabry-Perot interferometer. Peak-finding demodulation algorithm is used for demodulation of the fiber optic Fabry-Perot interferometer, while white light interferometry demodulation algorithm is used for demodulation of the fiber optic Fabry-Perot interferometer.

8. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 1, characterized in that: The three-wavelength symmetrical demodulation algorithm is used to demodulate the three laser interference signals detected by the three third photodiodes (15), so as to realize the high-speed measurement of the cavity length change of the fiber Fabry interferometer.

9. The fiber grating / fiber white light interferometry / fiber laser interferometry hybrid measurement system as described in claim 1, characterized in that: The wavelength range of the wavelength scanning light source (2) is 1520-1580nm, of which the wavelength range of 1520-1532nm is used for the measurement of fiber gratings, and the wavelength range of 1532-1580nm is used for the white light interference measurement of the fiber Fabry-Perot interferometer. The wavelength of the fiber grating and the absolute cavity length of the fiber Fabry-Perot interferometer are demodulated by the peak-finding demodulation algorithm and the interference order method, respectively, with a demodulation speed of 50Hz. The wavelengths of the three-wavelength laser light source (1) are 1585.43nm, 1587.14nm and 1588.83nm, respectively. The relative cavity length change of the fiber Fabry-Perot interferometer is demodulated by the three-wavelength symmetric demodulation algorithm, with a demodulation speed of 200kHz.

10. A method for synchronous measurement of multiple channels using the measurement system described in claims 1, 2, 3, 4, 5, 6, 7, 8, or 9, characterized in that: Each channel enables the simultaneous measurement of multiple parameters. The wavelength of the fiber optic grating is used to measure temperature or static strain. The absolute cavity length of the fiber optic Fabry-Perot interferometer, demodulated by white light interferometry, is used to measure static strain or static pressure. The relative cavity length change of the fiber optic Fabry-Perot interferometer, demodulated by laser interferometry, is used to measure dynamic strain, dynamic pressure, or vibration.

Images