A Multi-Channel Programmable Miniaturized High-Speed ​​FBG Demodulation System and Method Based on AWG

Abstract

This invention discloses a multi-channel programmable miniaturized high-speed FBG demodulation system and method based on an AWG (Optical Fiber Optic Generator), belonging to the field of fiber optic sensing technology. The AWG-based multi-channel programmable miniaturized high-speed FBG demodulation system includes a high-stability broadband light source module, a low-loss isolation module, a miniaturized programmable fiber optic amplifier, a circulator, a two-stage miniaturized high-speed optical switch, a high-crosstalk AWG module, a photoelectric conversion module, a programmable A / D conversion module, and a core control module. The AWG-based multi-channel programmable miniaturized high-speed FBG demodulation method involves the optical signal entering an FBG sensor array, the FBG sensor reflecting the optical signal, the reflected optical signal entering the AWG module, and the output light undergoing photoelectric conversion to calculate the center wavelength of the FBG sensor. This invention, based on an AWG, improves demodulation accuracy while ensuring the demodulation range, achieving continuous wavelength demodulation within the AWG wavelength range.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and in particular to a multi-channel programmable miniaturized high-speed FBG demodulation system and method based on AWG. Background Technology

[0002] Fiber Bragg Grating (FBG) sensors are characterized by small size, light weight, corrosion resistance, good durability, strong resistance to electromagnetic interference, good electrical insulation, reusability, ease of distributed measurement, and high sensitivity. They can be used to test information such as load, strain, temperature, and vibration of structures, and have been widely studied and applied in aerospace, environmental monitoring, and geological exploration.

[0003] A sensing system composed of FBG sensors primarily senses quantities based on minute wavelength drift. Therefore, a precise wavelength detection device is required to accurately demodulate the center wavelength of the FBG sensor. Furthermore, the measurement accuracy and frequency of the FBG sensor's center wavelength directly limit the system's measurement performance; thus, measurement accuracy and frequency are two key technologies that need to be addressed in fiber grating demodulation methods. The hardware of a fiber grating demodulation system mainly consists of a broadband light source, signal demodulation equipment, and FBG sensors. The broadband light source provides optical energy to the demodulation system. With proper installation, changes in the measured quantity cause changes in the center wavelength, and the information from the external measured quantity is reflected in real time by the demodulation system. Reliable and stable demodulation of the fiber grating sensor signal and high-speed, low-loss channel switching among multiple fiber optic sensors are crucial research areas.

[0004] In existing technologies, commonly used fiber grating demodulation methods include tunable fiber FP filtering and AWG-based demodulation. The system structure of the tunable fiber FP filtering method is as follows: Figure 1As shown, the system specifically includes: a broadband light source, an isolator, a coupler, a tunable FP filter, a scanning voltage source, a detector, and an FBG sensor. Light emitted from the broadband light source passes through the isolator and coupler into the FBG sensor. The light reflected by the FBG sensor passes through the coupler into the tunable FP cavity. The scanning voltage source can change the cavity length of the FP cavity, thereby changing the transmission wavelength. When the scanning voltage source makes the transmission wavelength of the FP cavity coincide with the reflection wavelength of the FBG, the detector can detect the maximum light intensity. The scanning voltage value at this point corresponds to the reflection wavelength of the FBG. However, the detection accuracy of this demodulation method is affected by the stability of the FP cavity, and the measurement of the FBG center wavelength requires correction. The demodulation rate of the FP cavity is relatively low. For FBG sensor arrays integrated on the same fiber, detection can only be performed one by one by wavelength scanning. For multiplexed system detection, the detection range of the FP cavity must also be able to accommodate the operating spectrum of all sensing fiber Bragg gratings.

[0005] The system architecture based on the AWG demodulation method is as follows: Figure 2 As shown, the system includes: a broadband light source, an isolator, a coupler, an AWG (Automatic Waveguide Gauge), a photoelectric conversion circuit, a signal processing circuit, and an FBG (Fast-Fast Generation Gauge) sensor. The broadband light emitted by the broadband light source passes through the isolator and coupler to enter the FBG sensor. The narrowband light signal reflected by the sensor enters the AWG through the coupler. The AWG spatially separates the narrowband light of different wavelengths and transmits it to each output waveguide. The photoelectric conversion circuit then converts it into an electrical signal, which is finally converted into an analog-to-digital converter (AD) signal by the signal processing circuit, and the center wavelength of the FBG sensor is calculated. Since the AWG has no moving parts, its demodulation speed is not limited by the mechanical structure's response speed, allowing for high speeds. A schematic diagram of the transmission spectrum of adjacent channels of the AWG and the reflection spectrum of the FBG sensor is shown below. Figure 3As shown, the transmission spectrum of each channel of the AWG is Gaussian. When the FBG is affected by temperature or strain, the center wavelength of its reflection spectrum will also change. Due to the filtering characteristics of the AWG, the output optical power of the corresponding channel will change. The magnitude of the optical power is the convolution of the AWG transmission spectrum function and the FBG reflection spectrum function of that channel. The changes in optical power of different channels are converted into changes in current magnitude using a photodetector. Then, the center wavelength of the FBG is calculated using the outputs of two adjacent channels, thereby achieving demodulation. However, it is difficult to balance the demodulation wavelength range and demodulation accuracy of the AWG. When the number of output waveguides is fixed, increasing the wavelength spacing between adjacent channels of the AWG can expand the demodulation wavelength range, but the demodulation accuracy will decrease. Furthermore, when the center wavelength of the FBG is close to the center wavelength of the AWG channel, the optical signal can only be measured on one output channel of the AWG chip, and wavelength demodulation cannot be achieved, resulting in a blind zone that cannot be monitored. In addition, when optical path extension, optical path conversion, or channel expansion is required, the AWG's beam splitting characteristics will reduce the intensity of the optical signal reaching the photodetector, lower the system signal-to-noise ratio, and limit the accuracy of the demodulation system. In cases of high optical path loss, the FBG sensor may even fail to be detected. Summary of the Invention

[0006] To address the problems of existing fiber optic grating demodulation techniques based on conventional AWGs, such as the inability to continuously demodulate the center wavelength of FBGs, narrow demodulation bandwidth, limited accuracy, and optical path loss, this invention provides a multi-channel programmable miniaturized high-speed FBG demodulation system and method based on AWGs.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG includes a high-stability broadband light source module, a low-loss isolation module, a miniaturized programmable fiber amplifier, a circulator, a two-stage miniaturized high-speed optical switch, a high-crosstalk AWG module, a photoelectric conversion module, a programmable A / D conversion module, and a core control module. The output of the high-stability broadband light source module is connected to the input of the low-loss isolation module. The output of the low-loss isolation module is connected to the first port of the circulator via the miniaturized programmable fiber amplifier. The second port of the circulator is connected to the two-stage miniaturized high-speed optical switch. The third port of the circulator is connected to the input of the high-crosstalk AWG module. The high-crosstalk AWG module, the photoelectric conversion module, the programmable A / D conversion module, and the core control module are connected sequentially.

[0009] The two miniaturized high-speed optical switches described above are connected to the FBG sensor array.

[0010] The aforementioned core control module is connected to the host computer.

[0011] The aforementioned two-stage miniaturized high-speed optical switch includes a first-stage miniaturized high-speed optical switch and a second-stage miniaturized high-speed optical switch. The first-stage miniaturized high-speed optical switch includes a 1xX miniaturized high-speed optical switch, and the second-stage miniaturized high-speed optical switch includes multiple 1xY miniaturized high-speed optical switches. The second port of the circulator is connected to the 1xX miniaturized high-speed optical switch, the 1xX miniaturized high-speed optical switch is connected to the multiple 1xY miniaturized high-speed optical switches, and the multiple 1xY miniaturized high-speed optical switches are connected to the FBG sensor array.

[0012] The aforementioned FBG sensor array includes multiple FBG sensors.

[0013] In one specific embodiment, the above-mentioned large crosstalk AWG module uses the output optical signals of four adjacent channels to demodulate the center wavelength of an FBG.

[0014] This invention also provides a multi-channel programmable miniaturized high-speed FBG demodulation method based on AWG, including,

[0015] Step S1: The optical signal from the high-stability broadband light source module passes through the low-loss isolation module and then enters the miniaturized programmable fiber amplifier for power amplification. After amplification, it passes through the circulator and the two-stage miniaturized high-speed optical switch in sequence, and then enters the FBG sensor array.

[0016] Step S2, the FBG sensor reflects a narrowband optical signal with a specific center wavelength back, and the reflected optical signal satisfies the Bragg condition:

[0017] λ B =2n eff Λ,

[0018] Where, λ B n is the center wavelength of the FBG sensor. eff Λ is the effective refractive index of the fiber core, and Λ is the grid period of the FBG sensor.

[0019] In step S3, the reflected light signal passes through the two-stage miniaturized high-speed optical switch again, then enters the second port of the circulator, and is then output from the third port of the circulator to the large crosstalk AWG module.

[0020] Step S4: The output light of the high crosstalk AWG module is connected to the photoelectric conversion module to achieve photoelectric conversion;

[0021] In step S5, the analog electrical signal after photoelectric conversion is converted into a digital signal by the programmable A / D conversion module, and the core control module calculates the center wavelength of the FBG sensor based on the digital signal.

[0022] The above-mentioned multi-channel programmable miniaturized high-speed FBG demodulation method based on AWG further includes transmitting the calculated center wavelength of the FBG sensor to the host computer.

[0023] The center wavelength of the above FBG sensor is calculated using the centroid algorithm, and the calculation formula is as follows:

[0024]

[0025] Where N is the number of samples involved in the centroid calculation; λ i p is the center wavelength of the output channel i of the high crosstalk AWG module; i The digital signal is the result of digitization, representing the power of the output spectrum of channel i.

[0026] In one specific embodiment, the number N of samples participating in the centroid calculation is 4.

[0027] Beneficial effects: This invention, based on a multi-channel programmable miniaturized high-speed FBG demodulation system and method using an AWG (Automatic Light Source Gear), improves demodulation accuracy while maintaining the demodulation range, and overcomes the problem that traditional AWG demodulation systems cannot achieve continuous demodulation. It uses the output optical signals of four adjacent channels to demodulate the center wavelength of an FBG, achieving continuous wavelength demodulation within the AWG wavelength range. By expanding the sensor channels through two-stage miniaturized high-speed optical switches, it has high-speed switching capabilities, increasing the sensor capacity of the demodulator and enabling demodulation of large-scale FBG sensors. Furthermore, by adjusting the optical signal intensity of the system through a miniaturized programmable fiber amplifier, the overall system... The power of the light source can be increased by several to tens of times. When the system uses a high-reflectivity FBG sensor and the optical path connection loss is small, the fiber amplifier operates at a smaller amplification factor. When using a low-reflectivity FBG sensor, there are multiple losses in the optical path connection, or an additional optical path extension is required, the fiber amplifier operates at a larger amplification factor, so that the reflected light signal that finally reaches the AWG module has sufficient light intensity, effectively maintaining the signal-to-noise ratio of the system under different working environments. By adjusting the signal amplification factor through the programmable A / D conversion module, the system signal-to-noise ratio is improved, ensuring the availability of the system under different working environments.

[0028] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system structure of the tunable fiber FP filtering method.

[0030] Figure 2 This is a schematic diagram of the system architecture for the AWG-based demodulation method.

[0031] Figure 3 for Figure 2 A schematic diagram of the transmission spectrum of adjacent channels of the Chinese method AWG and the reflection spectrum of the FBG sensor.

[0032] Figure 4 This is a schematic diagram of a specific embodiment of the multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG of the present invention.

[0033] Figure 5 This is a flowchart of the multi-channel programmable miniaturized high-speed FBG demodulation method based on AWG according to the present invention.

[0034] Figure 6 This is a schematic diagram of the channel output spectrum of the high crosstalk AWG module and the reflection spectrum of the FBG sensor in this invention.

[0035] In the accompanying drawings, similar reference numerals refer to the same elements. Detailed Implementation

[0036] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Figure 4 This is a schematic diagram of a specific embodiment of a multi-channel programmable miniaturized high-speed FBG demodulation system based on an AWG (Automatic Field-Range Gauge). Figure 4 As shown, this invention discloses a multi-channel programmable miniaturized high-speed FBG demodulation system based on an AWG (Automatic Light Source), comprising a high-stability broadband light source module 11, a low-loss isolation module 12, a miniaturized programmable fiber amplifier 13, a circulator 14, a two-stage miniaturized high-speed optical switch 15, a high-crosstalk AWG module 16, a photoelectric conversion module 17, a programmable A / D conversion module 18, and a core control module 19. The two-stage miniaturized high-speed optical switch 15 includes a first-stage miniaturized high-speed optical switch 151 and a second-stage miniaturized high-speed optical switch 152. The first-stage miniaturized high-speed optical switch 151 includes a 1xX miniaturized high-speed optical switch, and the second-stage miniaturized high-speed optical switch 152 includes multiple 1xY miniaturized high-speed optical switches.

[0038] The output of the high-stability broadband light source module 11 is connected to the input of the low-loss isolation module 12. The output of the low-loss isolation module 12 is connected to the first port of the circulator 14 via the miniaturized programmable fiber amplifier 13. The second port of the circulator 14 is connected to the 1xX miniaturized high-speed optical switch 151. The 1xX miniaturized high-speed optical switch 151 is connected to multiple 1xY miniaturized high-speed optical switches. The multiple 1xY miniaturized high-speed optical switches are connected to the FBG sensor array 30. The third port of the circulator 14 is connected to the input of the high-crosstalk AWG module 16. The high-crosstalk AWG module 16, the photoelectric conversion module 17, the programmable A / D conversion module 18, and the core control module 19 are connected in sequence. The core control module 19 is connected to the host computer 20. This invention provides a multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG to acquire wavelength signals from a large-scale FBG sensor array, and then uploads the demodulated sensor signals to the host computer via a communication line. The FBG sensor array 30 includes multiple FBG sensors.

[0039] In one specific embodiment, the selected broadband light source is a superluminescent diode with a wavelength range of 1520nm to 1580nm; the selected fiber amplifier is a programmable erbium-doped fiber amplifier, which can amplify the original optical signal with an adjustable amplification factor and a maximum output optical power of 100mW; the selected optical switch is a miniaturized high-speed optical switch with a switching time ≤10ns; the waveguide type of the large crosstalk AWG module is a rectangular waveguide, the cladding material of the large crosstalk AWG module is indium phosphide (InP), the core material is indium gallium arsenide phosphide (InGaAsP), and the crosstalk between adjacent channels of the large crosstalk AWG module is greater than -10dB or less than -15dB; the photoelectric conversion module is a PIN photodetector array; the programmable A / D conversion module uses a 20-bit resolution A / D conversion chip, and the front-end charge amplification factor is programmable; the core control module is implemented using an FPGA; the single-channel sampling rate of the FBG demodulation system is ≥10kHz, and the three-sided dimensions are ≤135mm×119mm×67mm.

[0040] This invention also provides a multi-channel programmable miniaturized high-speed FBG demodulation method based on AWG, such as... Figure 5 As shown, specifically including,

[0041] In step S1, the optical signal from the high-stability broadband light source module 11 passes through the low-loss isolation module 12 and then enters the miniaturized programmable fiber amplifier 13 for power amplification. The amplified broadband light then passes through the circulator 14 and the two-stage miniaturized high-speed optical switch 15 in sequence, and then enters the selected FBG sensor array.

[0042] In step S2, the FBG sensor reflects a narrowband optical signal with a specific center wavelength back, and the reflected optical signal satisfies the Bragg condition:

[0043] λ B =2n eff Λ. (1)

[0044] Where, λ B n is the center wavelength of the FBG sensor. eff Let n be the effective refractive index of the fiber core, and Λ be the grid period of the FBG sensor. Changes in the external measured quantity will cause n to... eff The changes in Λ result in changes in the center wavelength λ of the FBG sensor. B Things have changed.

[0045] In step S3, the reflected light signal passes through the two-stage miniaturized high-speed optical switch 15 again, then enters the second port of the circulator 14, and is then output from the third port of the circulator 14 into the large crosstalk AWG module 16.

[0046] Figure 6 The diagram shows the output spectrum of the high crosstalk AWG module channel and the reflection spectrum of the FBG sensor. Specifically, the output spectrum of the high crosstalk AWG module channel used in this embodiment is shown below. Figure 6 As shown by the solid line, the dashed line represents the reflection spectrum of the FBG sensor. The output spectra of the four adjacent output channels have overlapping regions. When the center wavelength of the reflected light signal of the FBG sensor is between the center wavelength of channel M and the center wavelength of channel M+1 of the large crosstalk AWG module, the reflected light signal of the FBG sensor can be received by channels M-1, M, M+1, and M+2. The light intensity of each channel corresponds to the convolution of the transmission spectrum function of each channel with the reflection spectrum function of the FBG sensor.

[0047] In step S4, the output light of the large crosstalk AWG module 16 is connected to the photoelectric conversion module 17 to achieve photoelectric conversion. Since the light power of the laser source itself is small, the signal light power reaching the photoelectric conversion module 17 after optical path attenuation is between a few nanowatts and several hundred nanowatts.

[0048] In one specific embodiment, the photoelectric conversion module used is a PIN photodetector with a sensitivity of 0.95 A / W, and the photocurrent output by the photoelectric conversion module is from a few nanoamps to several hundred nanoamps.

[0049] In step S5, the analog electrical signal after photoelectric conversion is converted into a digital signal by the programmable A / D conversion module 18. The core control module 19 calculates the center wavelength of the FBG sensor based on the digital signal, thereby enabling the FBG sensor to measure physical quantities such as strain and temperature of the test object. Furthermore, the calculated center wavelength of the FBG sensor can be transmitted to the host computer 20, and the host computer 20 can also transmit data to the core control module 19.

[0050] The programmable A / D conversion module 18 is implemented using a 20-bit resolution multi-channel A / D conversion chip. The center wavelength of the FBG sensor is calculated using the centroid algorithm, and the calculation formula is as follows:

[0051]

[0052] Where N is the number of samples participating in the centroid calculation, and in this specific embodiment, four adjacent channels are used to calculate the center wavelength of an FBG sensor, so N is 4; λ i p is the center wavelength of the output channel i of the high crosstalk AWG module 16; i This is a 20-bit digital signal after digitization, representing the power of the output spectrum of channel i.

[0053] In summary, this invention utilizes a programmable fiber optic amplifier to amplify the signal output from a broadband light source, employs a miniaturized high-speed optical switch to expand the demodulation channel, effectively ensuring the signal-to-noise ratio of the system under different operating environments and increasing the sensor capacity of the system; it also uses a large crosstalk AWG module to overcome the defect of traditional AWG demodulation methods in achieving continuous wavelength demodulation of FBG sensors, improving demodulation accuracy and expanding the demodulation wavelength range.

[0054] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG, characterized in that, The system includes a high-stability broadband light source module, a low-loss isolation module, a miniaturized programmable fiber amplifier, a circulator, a two-stage miniaturized high-speed optical switch, a high-crosstalk AWG module, a photoelectric conversion module, a programmable A / D conversion module, and a core control module. The output of the high-stability broadband light source module is connected to the input of the low-loss isolation module. The output of the low-loss isolation module is connected to the first port of the circulator via the miniaturized programmable fiber amplifier. The second port of the circulator is connected to the two-stage miniaturized high-speed optical switch. The third port of the circulator is connected to the input of the high-crosstalk AWG module. The high-crosstalk AWG module, the photoelectric conversion module, the programmable A / D conversion module, and the core control module are connected in sequence. The two-stage miniaturized high-speed optical switch includes a first-stage miniaturized high-speed optical switch and a second-stage miniaturized high-speed optical switch. The first-stage miniaturized high-speed optical switch includes a 1xX miniaturized high-speed optical switch, and the second-stage miniaturized high-speed optical switch includes multiple 1xY miniaturized high-speed optical switches. The second port of the circulator is connected to the 1xX miniaturized high-speed optical switch, the 1xX miniaturized high-speed optical switch is connected to the multiple 1xY miniaturized high-speed optical switches, and the multiple 1xY miniaturized high-speed optical switches are connected to the FBG sensor array. The core control module uses the output optical signals of four adjacent channels to demodulate the center wavelength of an FBG. The center wavelength of the FBG is calculated using the centroid algorithm, and the calculation formula is as follows: Where N is the number of samples involved in the centroid calculation; The center wavelength of the output channel i of the high crosstalk AWG module; The digital signal is the result of digitization, representing the power of the output spectrum of channel i. The number of samples N participating in the centroid calculation is 4.

2. The multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG as described in claim 1, characterized in that, The two-stage miniaturized high-speed optical switch is connected to the FBG sensor array.

3. The multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG as described in claim 2, characterized in that, The core control module is connected to the host computer.

4. The multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG as described in claim 1, characterized in that, The FBG sensor array includes multiple FBG sensors.

5. A multi-channel programmable miniaturized high-speed FBG demodulation method based on AWG, characterized in that, The multi-channel programmable miniaturized high-speed FBG demodulation system based on AWG as described in any one of claims 1-4 includes, Step S1: The optical signal from the high-stability broadband light source module passes through the low-loss isolation module and then enters the miniaturized programmable fiber amplifier for power amplification. After amplification, it passes through the circulator and the two-stage miniaturized high-speed optical switch in sequence, and then enters the FBG sensor array. In step S2, the FBG sensor reflects a narrowband optical signal with a specific center wavelength back, and the reflected optical signal satisfies the Bragg condition: ， in, The center wavelength of the FBG sensor is [missing information]. The effective refractive index of the optical fiber core. The grid period of the FBG sensor; In step S3, the reflected light signal passes through the two-stage miniaturized high-speed optical switch again, then enters the second port of the circulator, and is then output from the third port of the circulator to the large crosstalk AWG module. Step S4: The output light of the high crosstalk AWG module is connected to the photoelectric conversion module to achieve photoelectric conversion; In step S5, the analog electrical signal after photoelectric conversion is converted into a digital signal by the programmable A / D conversion module, and the core control module calculates the center wavelength of the FBG sensor based on the digital signal.

6. The multi-channel programmable miniaturized high-speed FBG demodulation method based on AWG as described in claim 5, characterized in that, It also includes transmitting the calculated center wavelength of the FBG sensor to the host computer.

Images