High-reliability fiber bragg grating demodulation device based on dual-light-source redundant structure

Abstract

The invention relates to a high-reliability fiber bragg grating demodulation device based on a double-light-source redundant structure, belongs to the technical field of optical fiber sensing, and solves the problems that in the prior art, reliability is high, single-point faults existing in a single-light-source fiber bragg grating demodulation device are eliminated, and the reliability of an existing single-light-source fiber bragg grating demodulation device is low. The high-reliability fiber bragg grating demodulation device comprises a plurality of channels and a signal processing circuit, each channel comprises a tunable light source, an optical fiber coupler, a 1 * 3 optical fiber coupler, an optical fiber interface of a demodulation device, an optical fiber grating sensor array and a photoelectric detector; the signal processing circuit comprises an operational amplifier, an analog-to-digital converter, a digital-to-analog converter and a field programmable gate array chip. The single-light-source fiber grating demodulation device is high in reliability, single-point faults existing in the single-light-source fiber grating demodulation device are eliminated, and the problem that an existing single-light-source fiber grating demodulation device is low in reliability is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a high-reliability optical fiber Bragg grating demodulation device based on a dual-light source redundant structure. Background Art

[0002] Fiber Bragg grating sensors are small in size, light in weight, and have strong anti-electromagnetic interference capabilities. They can be used in harsh working environments, have strong multiplexing capabilities, and are easy to network. Fiber Bragg grating sensors have great application potential in aerospace, bridges, highways, subway tunnels, and other fields.

[0003] The process of measuring the central wavelength and offset of a fiber Bragg grating sensor is called the demodulation of the fiber Bragg grating sensor. For a fiber Bragg grating sensing system, demodulation is an indispensable part. The performance of the demodulation device directly determines the performance index of the entire sensing system and is one of the key technologies of the fiber optic sensing system.

[0004] The demodulation schemes of fiber Bragg grating sensors can be divided into spectrum demodulation, interferometer demodulation, filter demodulation, tunable light source demodulation, etc. At present, there are three most commonly used fiber Bragg grating demodulation schemes in engineering, namely tunable light source demodulation, tunable filter demodulation, spectroscopic element and semiconductor photosensitive element demodulation. Among them, the tunable light source demodulation scheme has the characteristics of high output light power density, high signal-to-noise ratio, simple structure, and strong anti-interference ability, and has broad application prospects in the field of fiber optic sensing.

[0005] At present, the requirements for improving the reliability of fiber Bragg grating demodulation devices in applications such as satellites, aircraft, and missiles are becoming more and more stringent. However, the existing fiber Bragg grating demodulation devices based on tunable light sources only have one light source. This single-light source fiber Bragg grating demodulation device has a single point of failure and cannot meet the requirements of high-reliability applications. Figure 1 shown. Summary of the invention

[0006] In view of the above problems, the present invention provides a high-reliability fiber Bragg grating demodulation device based on a dual-light source redundant structure. It solves the problem of high reliability in the prior art, eliminates the single point failure in the single-light source fiber Bragg grating demodulation device, and solves the problem of low reliability of the existing single-light source fiber Bragg grating demodulation device.

[0007] The present invention provides a high-reliability fiber Bragg grating demodulation device based on a dual-light source redundant structure, comprising a plurality of channels and a signal processing circuit;

[0008] Each channel includes a tunable light source 1, a fiber coupler 2, a 1×3 fiber coupler 12, a fiber interface 4 of a demodulation device, a fiber grating sensor array 5, and a photodetector 6;

[0009] The signal processing circuit includes an operational amplifier 7, an analog-to-digital converter 8, a digital-to-analog converter 10 and a field programmable gate array chip 9;

[0010] The tunable light source 1 is connected to the optical fiber coupler 2;

[0011] The 1×3 optical fiber coupler 12 is respectively connected to the optical fiber coupler 2, the optical fiber interface 4 of the demodulation device and the photodetector 6;

[0012] The optical fiber interface 4 is also connected to the optical fiber grating sensor array 5;

[0013] The photodetector 6 is also connected to the signal processing circuit;

[0014] The field programmable gate array chip 9 is connected to the analog-to-digital converter 8 and the digital-to-analog converter 10 respectively;

[0015] The operational amplifier 7 is connected to the analog-to-digital converter 8 .

[0016] Optionally, each channel is provided with one tunable light source 1 , one fiber coupler 2 , two 1×3 fiber couplers 12 , one fiber interface 4 of a demodulation device and two photodetectors 6 .

[0017] Optionally, one tunable light source 1 is connected to one fiber coupler 2; one fiber coupler 2 is respectively connected to two 1×3 fiber couplers 12; one 1×3 fiber coupler 12 is respectively connected to a fiber interface 4 of a demodulation device and a photodetector 6.

[0018] Optionally, the number of operational amplifiers 7 and analog-to-digital converters 8 is twice the number of channels; and the number of digital-to-analog converters 10 is the same as the number of channels.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: high reliability, eliminating the single point failure existing in the single light source fiber Bragg grating demodulation device, and solving the problem of low reliability of the existing single light source fiber Bragg grating demodulation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings are only for the purpose of illustrating particular embodiments and are not to be construed as limiting the invention.

[0021] Figure 1 It is a schematic diagram of a single light source fiber Bragg grating demodulation device used in the prior art;

[0022] Figure 2 is a schematic diagram of a high-reliability fiber Bragg grating demodulation device of the present invention;

[0023] Figure 3It is a five-year reliability comparison chart of two fiber Bragg grating demodulation devices when a single-light-source fiber Bragg grating demodulation device used in the prior art is available;

[0024] Figure 4 This is a comparison chart of the reliability of two fiber Bragg grating demodulation devices within five years when all channels of the high-reliability fiber Bragg grating demodulation device of the present invention are available.

[0025] Reference numerals:

[0026] 1. Tunable light source; 2. 1×4 fiber coupler; 3. 1×2 fiber coupler; 4. Fiber interface of demodulation device; 5. Fiber Bragg grating sensor array; 6. Photodetector (PD); 7. Operational amplifier (OPA); 8. Analog-to-digital converter (ADC); 9. Field programmable gate array chip (FPGA); 10. Digital-to-analog converter (DAC); 11. Other circuits; 12. 1×3 fiber coupler. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0028] like Figure 1 FIG. 1 is a schematic diagram of a single-light-source fiber Bragg grating demodulation device used in the prior art.

[0029] A specific embodiment of the present invention, as Figure 2-4 , discloses a high-reliability fiber Bragg grating demodulation device based on a dual-light source redundant structure, including m channels, 2 tunable light sources 1, 2 1×m fiber couplers 2, m 1×3 fiber couplers 12, m fiber interfaces 4 of the demodulation device and a fiber Bragg grating sensor array 5, m photodetectors 6 and operational amplifiers 7, m analog-to-digital converters 8 and digital-to-analog converters 10, a field programmable gate array chip 9 and other circuits 11.

[0030] Among them, one field programmable gate array chip 9 is connected to m analog-to-digital converters 8 and m / 2 digital-to-analog converters 10 respectively; and the operational amplifier 7 is connected to the analog-to-digital converter 8 .

[0031] Exemplarily, m=4.

[0032] The working process of a channel in the fiber Bragg grating demodulation device of the present invention is as follows: first, the field programmable gate array chip 9 controls the digital-to-analog converter 10 to drive the tunable light source 1, the tunable light source 1 emits a scanning laser and enters the corresponding 1×m fiber coupler 2, the scanning laser is divided into m beams, and enters the 1×3 fiber coupler 12 respectively, and then passes through the fiber interface 4 of the demodulation device and is reflected by the fiber Bragg grating sensor array 5, and the reflected light passes through the fiber interface 4 of the demodulation device and the 1×3 fiber coupler 12 and reaches the photodetector 6, the photodetector 6 converts the optical signal into an analog electrical signal and enters the operational amplifier 7, and then the analog electrical signal is converted into a digital electrical signal by the analog-to-digital converter 8 and enters the field programmable gate array chip 9, and finally the digital electrical signal is processed to demodulate the center wavelength and offset of the fiber Bragg grating sensor.

[0033] Compared with the single-light-source fiber Bragg grating demodulation device used in the prior art, the fiber Bragg grating demodulation device of the present invention has two digital-to-analog converters driving two tunable light sources, and the two tunable light sources emit scanning lasers into two 1×m fiber couplers. When one of the two devices fails, the other device can still work normally, playing a role of redundant backup. Since it is necessary to receive the scanning lasers emitted by the two tunable light sources, the fiber Bragg grating demodulation device also uses a 1×3 fiber coupler to replace the 1×2 fiber coupler in the prior art.

[0034] In order to quantitatively illustrate that the reliability of the fiber Bragg grating demodulation device with dual-light source redundant structure is higher than that of the single-light source fiber Bragg grating demodulation device, the following two methods are used for comparison, namely, a method for calculating the reliability changing with time and a fault injection method.

[0035] Method 1: Method for calculating reliability over time;

[0036] Consider the reliability calculation of the fiber Bragg grating demodulation device in two cases. Case 1 is that if all m channels can work normally, it is considered that the fiber Bragg grating demodulation device has no fault. Case 2 is that if only one channel can work normally, it is considered that the fiber Bragg grating demodulation device can still achieve its demodulation function and the demodulation system is judged to be normal.

[0037] For the single-light-source fiber Bragg grating demodulation device used in the prior art, the reliability R under case 1 is mt The calculation formula is:

[0038] R mt =R 1 R 2 R 9 R 10 ·(R 3 R 4 R 5 R 6R 7 R 8 R 11 ) m

[0039] Among them, R 1 is the reliability of the tunable light source, R 2 is the reliability of the 1×4 fiber coupler, R 3 is the reliability of the 1×2 fiber coupler, R 4 is the reliability of the optical fiber interface of the demodulation device, R 5 is the reliability of the fiber Bragg grating sensor array, R 6 is the reliability of the photodetector (PD), R 7 is the reliability of the operational amplifier (OPA), R 8 is the reliability of the analog-to-digital converter (ADC), R 9 is the reliability of the field programmable gate array chip (FPGA), R 10 is the reliability of the digital-to-analog converter (DAC), R 11 is the reliability of other circuits.

[0040] Reliability R under Case 2 mt The calculation formula is:

[0041] R mt =R 1 R 2 R 9 R 10 ·[1-(1-R 3 R 4 R 5 R 6 R 7 R 8 R 11 ) m ]

[0042] For the fiber Bragg grating demodulation device with dual light source redundant structure provided by the present invention, the reliability R me The calculation formula is:

[0043]

[0044] Among them, R 12 is the reliability of the 1×3 fiber coupler.

[0045] Reliability R under Case 2 me The calculation formula is:

[0046]

[0047] Mean time between failures (MTBF) is a measure of the reliability of a device, measured in hours. It reflects the ability of a device to maintain its function within a specified time. According to the data, the MTBF of tunable light source 1 is 312500 hours, and the MTBF of photodetector 6 is 3.9×10 9 hours, the MTBF of field programmable gate array chip 9 is 5.74×10 8 The MTBF of 1×4 fiber coupler 2, 1×2 fiber coupler 3 and 1×3 fiber coupler 12 are all 4.1×10 6 hours, the MTBF of the operational amplifier 7, the analog-to-digital converter 8, the digital-to-analog converter 10 and other circuits 11 are all 10 8 Hour.

[0048] The reliability of optoelectronic devices follows an exponential distribution, and its reliability R(t) can be expressed as

[0049] R(t)=e -tMTBF

[0050] Here, t represents time, and the reliability of each device over time is considered within five years, that is, the range of t is from 0 hours to 43,800 hours.

[0051] It is understandable that optoelectronic devices are Figure 1-2 All devices except the "signal processing circuit" below.

[0052] Substituting the reliability of each device over time within five years into the reliability calculation formula of the entire fiber Bragg grating demodulation device, a reliability comparison chart of the single-light source fiber Bragg grating demodulation device and the dual-light source redundant structure fiber Bragg grating demodulation device within five years is obtained, as shown in Figure 3 and Figure 4 shown.

[0053] Figure 3 This is a five-year reliability comparison chart of two fiber Bragg grating demodulation devices when a single channel is available. It can be seen that in the first year, the reliability of the single-light-source fiber Bragg grating demodulation device is 0.9701, and the reliability of the dual-light-source redundant fiber Bragg grating demodulation device is 0.9991. In the fifth year, the reliability of the single-light-source fiber Bragg grating demodulation device is 0.8594, and the reliability of the dual-light-source redundant fiber Bragg grating demodulation device is 0.9802. Throughout the five-year period, the reliability of the dual-light-source redundant fiber Bragg grating demodulation device is higher than that of the single-light-source fiber Bragg grating demodulation device.

[0054] Figure 4This is a comparison chart of the reliability of two fiber Bragg grating demodulation devices within five years when all channels are available. It can be seen that in the first year, the reliability of the single-light-source fiber Bragg grating demodulation device is 0.961, and the reliability of the dual-light-source redundant structure fiber Bragg grating demodulation device is 0.9897. In the fifth year, the reliability of the single-light-source fiber Bragg grating demodulation device is 0.8197, and the reliability of the dual-light-source redundant structure fiber Bragg grating demodulation device is 0.9349. Throughout the five-year period, the reliability of the dual-light-source redundant structure fiber Bragg grating demodulation device is higher than the reliability of the single-light-source fiber Bragg grating demodulation device. Therefore, whether it is a single-channel available situation or a full-channel available situation, the fiber Bragg grating demodulation device proposed in the present invention has higher reliability.

[0055] Method 2: Fault injection method;

[0056] Fault injection is an effective method to evaluate system reliability and a reliability verification technology. It evaluates the reliability of a system by deliberately introducing faults into the system and observing the behavior of the system when the faults exist. The number of detectable fiber Bragg grating sensors after fault injection represents the reliability of the demodulation device. When the number of detectable fiber Bragg grating sensors is zero, the entire fiber Bragg grating demodulation device is considered to be completely ineffective.

[0057] Two fault conditions are considered: fault condition 1 is a fiber interface or a photodetector failure, fault condition 2 is a tunable light source failure, and fault condition 3 is a 1×4 fiber coupler failure.

[0058] Considering that the number of fiber Bragg grating sensors in each channel of the two four-channel fiber Bragg grating demodulation devices is 10, there are 40 fiber Bragg grating sensors in total.

[0059] In fault condition 1, the number of detectable fiber Bragg gratings of both fiber Bragg grating demodulation devices is 30. In fault condition 2 and fault condition 3, the number of detectable fiber Bragg gratings of the single-light-source fiber Bragg grating demodulation device used in the prior art is 0, and the entire fiber Bragg grating demodulation device is completely ineffective. However, the fiber Bragg grating demodulation device with a dual-light-source redundant structure proposed in the present invention can still detect all 40 fiber Bragg grating sensors.

[0060] Therefore, the fiber grating demodulation device proposed by the present invention eliminates single point failure and has higher reliability.

[0061] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-reliability fiber Bragg grating demodulation device based on a dual-light source redundant structure, characterized in that: Includes multiple channels and signal processing circuits; Each channel includes a tunable light source, a fiber coupler, a 1×3 fiber coupler, a fiber interface of a demodulation device, a fiber Bragg grating sensor array, and a photodetector; The signal processing circuit includes an operational amplifier, an analog-to-digital converter, a digital-to-analog converter, and a field programmable gate array chip; The tunable light source is connected to the optical fiber coupler; The 1×3 optical fiber coupler is respectively connected to the optical fiber coupler, the optical fiber interface of the demodulation device and the photoelectric detector; The optical fiber interface is also connected to the fiber grating sensor array; The photodetector is also connected to the signal processing circuit; The field programmable gate array chip is respectively connected with the analog-to-digital converter and the digital-to-analog converter; The operational amplifier is connected to the analog-to-digital converter.

2. The high-reliability fiber Bragg grating demodulation device according to claim 1, characterized in that: Each channel is provided with a tunable light source, a fiber coupler, two 1×3 fiber couplers, a fiber interface of a demodulation device and two photoelectric detectors 6.

3. The high-reliability fiber Bragg grating demodulation device according to claim 2, characterized in that: A tunable light source is connected to a fiber coupler; a fiber coupler is respectively connected to two 1×3 fiber couplers; a 1×3 fiber coupler is respectively connected to a fiber interface of a demodulation device and a photoelectric detector.

4. The high-reliability fiber Bragg grating demodulation device according to any one of claims 1 to 3, characterized in that: The number of operational amplifiers and analog-to-digital converters is twice the number of channels; the number of digital-to-analog converters is the same as the number of channels.

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