A multi-sensor multiplexing temperature-pressure demodulation system and method for an EFPI optical fiber sensor

Abstract

The application discloses a kind of EFPI optical fiber sensor multi-sensor multiplexing temperature-pressure demodulation system and method, including ASE broadband laser, optical circulator, EFPI optical fiber sensor, 2-way wavelength division multiplexer, N-way wavelength division multiplexer, N-way wavelength division demultiplexer, photoelectric detector, FBG, 1*2 optical fiber coupler, optical spectrometer, data processing system;The input port input of the optical circulator is connected with ASE broadband laser, the output port cir2 is connected with two cascaded FBGs, the output port cir3 is connected with EFPI optical fiber sensor, the input port of 2-way wavelength division multiplexer is connected with the output port cir4 of optical circulator, and the output port is connected with N-way wavelength division multiplexer;N-way wavelength division multiplexer is accessed via the input port of 1*2 optical fiber coupler, and outputs two-way signals, one-way is connected with N-way wavelength division demultiplexer via N-way photoelectric detector and data processing system, and the other way is connected with optical spectrometer;N channels are connected by cascaded FBG, and the cascade of N EFPI optical fiber sensors is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical fiber sensing, and particularly relates to a multi-sensor multiplexing temperature-pressure demodulation system and method of an EFPI optical fiber sensor. BACKGROUND

[0002] EFPI optical fiber sensors have attracted more and more attention due to low transmission loss, large measurement dynamic range, high sensitivity, compact structure, electromagnetic anti-interference ability, and strong on-line transmission ability. For some complex environments, multiple sensors are usually installed to monitor environmental parameters. The use of multiple traditional single-channel optical fiber white light interference measurement systems is costly and complex to lay optical fibers. The use of multiplexing technology can greatly reduce the cost.

[0003] For the multiplexing problem of EFPI optical fiber sensors, the commonly used multiplexing methods include space division multiplexing, time division multiplexing, and frequency division multiplexing. The space division multiplexing system has a simple structure, but the multiplexing efficiency is low and the cost is high. The time division multiplexing system is greatly limited by the power of the light source, requires a high sampling rate of the pulse light source, and the switching of the optical path limits the overall measurement speed of the system. The frequency division multiplexing system requires different cavity lengths between the sub-sensors, which is difficult to manufacture, and the multiplexing number is also limited, which has poor practicability. The existing EFPI optical fiber sensor multiplexing system has a complex circuit, is difficult to implement remote placement, and has difficulty in demodulating the sensing signal. At the same time, when a sensor in the sensor array is damaged, it is difficult to accurately locate and replace the damaged sensor in time. SUMMARY

[0004] The present application aims to overcome the difficulty of large-scale multiplexing of EFPI optical fiber sensors and proposes a multi-sensor multiplexing temperature-pressure demodulation system and method of an EFPI optical fiber sensor.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] A multi-sensor multiplexing temperature-pressure demodulation system for EFPI fiber optic sensors includes an ASE broadband laser, an optical circulator, an EFPI fiber optic sensor, a 2-channel wavelength division multiplexer (WDM), an N-channel WDM, an N-channel WDM, a photodetector, an FBG (fiber cascade generator), a 1×2 fiber optic coupler, a spectrometer, and a data processing system. The input port of the optical circulator is connected to the ASE broadband laser, its output port (cir2) is connected to two cascaded FBGs, and its output port (cir3) is connected to the EFPI fiber optic sensor. The input port of the 2-channel WDM is connected to the output port (cir4) of the optical circulator, and its output port is connected to the N-channel WDM. The N-channel WDM is connected via the input port of the 1×2 fiber optic coupler and outputs two signals: one signal is connected to the N-channel WDM via the N photodetectors and then to the data processing system, and the other signal is connected to the spectrometer. Each of the N channels is connected by a cascaded FBG, enabling the cascading of N EFPI fiber optic sensors.

[0007] Furthermore, the optical circulator enables the broadband optical signal emitted by the ASE broadband laser to be transmitted unidirectionally to the FBG, and then the reflected light is transmitted to the EFPI fiber optic sensor. The reflected light signal from the sensor is transmitted to the 2-way wavelength demultiplexer via the optical circulator.

[0008] The FBG filters the broadband light source signal into narrowband optical signals with different center wavelengths to realize wavelength division multiplexing of the EFPI fiber optic sensor, and is also used to measure temperature changes and perform temperature compensation.

[0009] The EFPI fiber optic sensor converts external acoustic pressure signals into changes in the sensor's cavity length.

[0010] The two-way wave demultiplexer decomposes the reflected spectral interference signal into two narrowband spectral interference signals with the same center wavelength as the two FBGs corresponding to the EFPI fiber optic sensor.

[0011] The N-way wavelength division multiplexer combines the 2*N narrowband spectral interference signals after passing through the 2-way wavelength division multiplexer and transmits them to the 1×2 fiber coupler.

[0012] The 1×2 fiber coupler splits a single combined optical signal into two signals according to the power distribution ratio, and transmits them to the N-channel demultiplexer and the spectrometer, respectively.

[0013] The N-channel wave demultiplexer divides the merged optical signal into N narrowband spectral interference signals, marks different sensors according to the center wavelength of each FBG, and transmits the N narrowband optical signals to the photodetector respectively.

[0014] The photodetector converts narrowband optical signals into time-varying electrical signals;

[0015] The spectrometer monitors the reflectance spectral signal and reads the wavelength shift of the FBG caused by temperature changes;

[0016] The data processing system converts the photoelectric signal into an A / D converter and then sends it to the programmed host computer to demodulate and calculate the cavity length values ​​of the N EFPI fiber optic sensors.

[0017] A multi-sensor multiplexing temperature-pressure demodulation method for EFPI fiber optic sensors, comprising the following steps:

[0018] Step 1: The electrical signal obtained by the photodetector is amplified, sampled, and then converted into a discrete digital electrical signal;

[0019] Step 2: Use the orthogonal demodulation algorithm to process and calculate the digital electrical signals corresponding to each EFPI fiber optic sensor separately, and calculate the cavity length change of each EFPI fiber optic sensor.

[0020] Step 3: Based on the final reflection spectrum signal monitored by the spectrometer, calculate the wavelength drift of each EFPI fiber optic sensor, and calculate the external temperature of each sensor based on the relationship between wavelength drift and temperature.

[0021] Step 4: Based on the change in cavity length of each EFPI fiber optic sensor affected by temperature-sound pressure changes, calculate the external sound pressure of each of the N sensors.

[0022] The beneficial effects of this invention are as follows:

[0023] The employed EFPI fiber optic sensors possess extremely high sensitivity, enabling the detection of minute acoustic signals from remotely deployed sensors. A dual-wavelength orthogonal demodulation algorithm demodulates the two narrowband optical signals corresponding to each sensor to obtain the external sound pressure signal. Utilizing the temperature sensitivity of the FBG (Fiber Optic Gauge), the system can measure temperature simultaneously with sound pressure. The FBG also provides temperature compensation, eliminating the sensor's temperature-pressure cross-sensitivity and achieving high-precision temperature and sound pressure measurements. Simultaneously, the filtering effect of the FBG reduces the spectral bandwidth occupied by each sensor, enabling wavelength division multiplexing (WDM) of the various fiber optic sensors. Controlling the center wavelength of each FBG to be inconsistent allows for the marking of different sensors and timely replacement of damaged sensors within the sensor array. The use of a wavelength division multiplexer (WDM) enables remote deployment of the sensor array, effectively solving the challenge of large-scale multiplexing of EFPI fiber optic sensors.

[0024] This invention utilizes Bragg fiber gratings (FBGs) with different center wavelengths to complete wavelength division multiplexing and mark each EFPI sensor. Combined with a dual-wavelength orthogonal demodulation algorithm, the system can achieve large-scale multiplexing while simultaneously locating each sensor and demodulating external sound pressure and temperature. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a multi-sensor multiplexing temperature-pressure demodulation system for EFPI fiber optic sensors.

[0026] Figure 2 This is a schematic diagram of the ports of an optical circulator. Detailed Implementation

[0027] The present invention will now be further described with reference to the accompanying drawings.

[0028] like Figure 1 As shown, a multi-sensor multiplexing temperature-pressure demodulation system for EFPI fiber optic sensors includes an ASE broadband laser 1, a first FBG 2, a second FBG 3, a third FBG 4, a fourth FBG 5, a fifth FBG 6, a sixth FBG 7, a first optical circulator 8, a second optical circulator 10, a third optical circulator 12, a first EFPI fiber optic sensor 9, a second EFPI fiber optic sensor 11, a third EFPI fiber optic sensor 13, a first 2-way wavelength division multiplexer 14, a second 2-way wavelength division multiplexer 15, a third 2-way wavelength division multiplexer 16, an N-way wavelength division multiplexer 17, a 1×2 fiber optic coupler 18, an N-way wavelength division multiplexer 19, a first electrical detector 20, a second electrical detector 21, a third electrical detector 22, a fourth electrical detector 23, a fifth electrical detector 24, a sixth electrical detector 25, a data processing system 26, and a spectrometer 27.

[0029] The EFPI fiber optic sensor's multi-sensor multiplexing temperature-pressure demodulation system uses a C-band ASE broadband light source with an output width of 40nm. The center wavelength of each FBG is spaced 1nm apart, the reflection spectrum bandwidth is less than 0.2nm, the reflectivity is greater than 99%, and the temperature sensitivity is about 10pm / ℃. This ensures that the light source signals of each sensor do not interfere with each other and can sense independently.

[0030] The first optical circulator 8, the second optical circulator 10, and the third optical circulator 12 have their input ports connected to a light source, their CIR2 ports connected to a cascaded FBG, their CIR3 ports connected to an EFPI fiber optic sensor, and their CIR4 ports connected to a 2-channel wavelength demultiplexer.

[0031] The ASE broadband laser 1 has a wide operating bandwidth, high and stable output power, and adjustable operating wavelength to output a stable broadband optical signal. This broadband optical signal is input through port (input) of the first optical circulator 8, and transmitted through port (cir2) to the cascaded first FBG2 and second FBG3. The signal is reflected back through the filtering effect of the first FBG2 and second FBG3, resulting in a spectrum containing two narrowband optical signals. The narrowband optical signal is input to the first EFPI fiber optic sensor 9 through port (cir3) of the first optical circulator 8. The reflected optical signal from the first EFPI fiber optic sensor 9 is transmitted to the first two-way wave demultiplexer 14 through port (cir4) of the first optical circulator 8. The first two-way wave demultiplexer 14 decomposes the interference spectrum containing the sensor's acoustic pressure information into two narrowband interference spectra with the same center wavelengths as the first FBG2 and second FBG3.

[0032] The transmitted light from the first FBG2 and the second FBG3 is transmitted via optical fiber to the input port of the next second optical circulator 10 as the light source signal for the next channel. Each of the N channels is connected by a cascaded FBG, realizing the cascading of N EFPI fiber optic sensors.

[0033] The N-channel wavelength division multiplexer 17 combines 2*N narrowband interference spectra from N first 2-channel wavelength division multiplexers 14, second 2-channel wavelength division multiplexers 15, and third 2-channel wavelength division multiplexers 16. The resulting signals are then output as two optical signals of equal power via a 1×2 fiber optic coupler 18. One signal is connected to the N-channel wavelength division multiplexer 19, and the other is connected to the spectrometer 27. The N-channel wavelength division multiplexer 19 divides the combined optical signal into N narrowband spectral interference signals. These N narrowband optical signals are transmitted via optical fiber to the first electrical detector 20, where they are converted into time-varying electrical signals. These signals are then amplified, sampled, and converted into discrete digital electrical signals, which are then transmitted to the data processing system 26.

[0034] The data processing system 26 uses an orthogonal demodulation algorithm to demodulate the cavity length of the EFPI fiber optic sensor and marks different sensors according to the center wavelength of each FBG. The spectrometer 27 monitors the final interference spectrum signal and calculates the center wavelength drift of each EFPI fiber optic sensor. The center wavelength drift is linearly related to temperature; based on this linear relationship, the external temperature of each EFPI fiber optic sensor is calculated. Simultaneously, the temperature compensation effect of the FBG is utilized to eliminate the temperature-pressure cross-sensitivity of the sensor, achieving high-precision measurement of the external sound pressure and temperature of the EFPI fiber optic sensor.

[0035] A multi-sensor multiplexing temperature-voltage demodulation method for EFPI fiber optic sensors, the specific steps of which are as follows:

[0036] Step 1: The electrical signal obtained by the photodetector is amplified, sampled, and then converted into a discrete digital electrical signal;

[0037] Step 2: Use the orthogonal demodulation algorithm to process and calculate the digital electrical signals corresponding to each EFPI fiber optic sensor separately, and calculate the cavity length change of each EFPI fiber optic sensor.

[0038] Step 3: Based on the final reflection spectrum signal monitored by the spectrometer, calculate the wavelength drift of each EFPI fiber optic sensor, and calculate the external temperature of each sensor based on the relationship between wavelength drift and temperature.

[0039] Step 4: Based on the change in cavity length of each EFPI fiber optic sensor affected by temperature-sound pressure changes, calculate the external sound pressure of each of the N sensors.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 multi-sensor multiplexing temperature-pressure demodulation system for EFPI fiber optic sensors, characterized in that: The system includes an ASE broadband laser (1), an optical circulator, an EFPI fiber optic sensor, a 2-channel wavelength division multiplexer (WDM), an N-channel wavelength division multiplexer (17), an N-channel wavelength division multiplexer (19), a photodetector, an FBG, a 1×2 fiber optic coupler (18), a spectrometer (27), and a data processing system (26). The input port of the optical circulator is connected to the ASE broadband laser (1), the output port cir2 is connected to two cascaded FBGs, and the output port cir3 is connected to the EFPI fiber optic sensor. The input port of the 2-channel wavelength division multiplexer is connected to the output port cir4 of the optical circulator, and the output port is connected to the N-channel wavelength division multiplexer (17). The N-channel wavelength division multiplexer (17) is connected to the input port of the 1×2 fiber optic coupler (18) and outputs two signals. One signal is connected to the N-channel wavelength division multiplexer (19) and then to the data processing system (26) via the N-channel photodetector. The other signal is connected to the spectrometer (27). The N channels are each connected by cascaded FBGs to realize the cascading of N EFPI fiber optic sensors.

2. The multi-sensor multiplexing temperature-pressure demodulation system for EFPI fiber optic sensors according to claim 1, characterized in that: The optical circulator enables the broadband optical signal emitted by the ASE broadband laser (1) to be transmitted unidirectionally to the FBG, and then the reflected light is transmitted to the EFPI fiber optic sensor. The reflected light signal of the sensor is transmitted to the 2-way wave demultiplexer via the optical circulator. The FBG filters the broadband light source signal into narrowband optical signals with different center wavelengths to realize wavelength division multiplexing of the EFPI fiber optic sensor, and is also used to measure temperature changes and perform temperature compensation. The EFPI fiber optic sensor converts external acoustic pressure signals into changes in the sensor's cavity length. The two-way wave demultiplexer decomposes the reflected spectral interference signal into two narrowband spectral interference signals with the same center wavelength as the two FBGs corresponding to the EFPI fiber optic sensor. The N-way wavelength division multiplexer (17) combines the 2*N narrowband spectral interference signals after passing through the 2-way wavelength division multiplexer and transmits them to the 1×2 fiber coupler (18). The 1×2 fiber coupler (18) splits a combined optical signal into two signals according to the power distribution ratio, and transmits them to the N-channel demultiplexer (19) and the spectrometer (27) respectively. The N-way wave demultiplexer (19) divides the merged optical signal into N narrowband spectral interference signals, marks different sensors according to the center wavelength of each FBG, and transmits the N narrowband optical signals to the photodetector respectively. The photodetector converts narrowband optical signals into time-varying electrical signals; The spectrometer (27) monitors the reflectance spectral signal and reads the wavelength shift of the FBG caused by temperature changes; The data processing system (26) converts the photoelectric signal, performs A / D conversion and acquisition, and sends it to the programmed host computer to demodulate and calculate the cavity length values ​​of N EFPI fiber optic sensors.

3. A method for a multi-sensor multiplexing temperature-pressure demodulation system for an EFPI fiber optic sensor as described in claim 1, characterized in that: The specific steps are as follows: Step 1: The electrical signal obtained by the photodetector is amplified, sampled, and then converted into a discrete digital electrical signal; Step 2: Use the orthogonal demodulation algorithm to process and calculate the digital electrical signals corresponding to each EFPI fiber optic sensor separately, and calculate the cavity length change of each EFPI fiber optic sensor. Step 3: Based on the final reflection spectrum signal monitored by the spectrometer, calculate the wavelength drift of each EFPI fiber optic sensor, and calculate the external temperature of each sensor based on the relationship between wavelength drift and temperature. Step 4: Based on the change in cavity length of each EFPI fiber optic sensor affected by temperature-sound pressure changes, calculate the external sound pressure of each of the N sensors.

Images