CN112697061A

CN112697061A - Optical fiber strain system based on filter

Info

Publication number: CN112697061A
Application number: CN202110001860.7A
Authority: CN
Inventors: 王一川; 郑利军
Original assignee: WUXI KEY-SENSOR PHOTONICS TECHNOLOGY CO LTD
Current assignee: WUXI KEY-SENSOR PHOTONICS TECHNOLOGY CO LTD
Priority date: 2021-01-04
Filing date: 2021-01-04
Publication date: 2021-04-23

Abstract

The invention discloses an optical fiber strain system based on a filter, which comprises a light source, a coupler, a circulator, a demodulation module, an electro-optic modulator, a filter and a sensing optical fiber, wherein the light source generates light with the frequency of f0, the coupler is connected with the light source, and the light of the light source is split into two beams of light with the same frequency; the coupler is also connected with a circulator and a photoelectric regulator, wherein the photoelectric modulator shifts the frequency of light to two sides simultaneously to convert the light into dual-frequency light, the dual-frequency light is respectively f 1-f 0- Δ f, f2-f 0 +/Δ f, the rear end of the photoelectric modulator is connected with a filter, the filter is used for filtering the light with the frequency of f1 and transmitting the light with the frequency of f2, the filter is connected with an optical cable, and the circulator is connected with a sensing optical fiber and an adjusting module; the adjustment module detects the stress change according to the light energy change with the judgment frequency f 1. The invention directly filters f1 through the filter, thereby greatly reducing the hardware cost and simplifying the system structure.

Description

Optical fiber strain system based on filter

Technical Field

The invention relates to the technical field of optical fiber detection, in particular to an optical fiber strain system based on a filter.

Background

Nowadays, the optical fiber strain monitoring system is widely applied to the field of health monitoring of bridge tunnels. When the bridge tunnel has micro cracks, the alarm is accurately given, and special personnel carry out treatment, so that the condition that the bridge tunnel collapses is avoided.

The structure of a conventional optical fiber strain monitoring system is shown in fig. 1:

the device comprises a light source, a coupler, an acousto-optic modulator, an electro-optic modulator, a circulator, a sensing optical fiber and a demodulation module. The principle is as follows:

the light from the light source is converted into two beams of light with the frequency f0 by the coupler. Then, after passing through the electro-optical modulator, the frequency shifts to both sides simultaneously, becoming a dual-frequency light, and f1 ═ f0- Δ f, f2 ═ f0 +/Δ f; the frequency shift is f3 ═ f0 +. DELTA.f 1 through the acousto-optic modulator. Through the circulator, light of three frequencies undergoes energy transfer in the sensing fiber through the circulator. And the direction of energy transfer is: f2 → f3 → f 1. However, (f2-f3) < (f3-f1), so the end result is that the energy of f2 is transferred to f3, but the energy of f3 is not transferred to f 3. At this time, when the strain of the sensing fiber changes, the energy transferred from f2 to f3 changes. The demodulation module can then analyze the strain condition of the optical fiber by monitoring the energy change of f3 in real time. Furthermore, the optical fiber is fixed on the bridge tunnel, so that the strain condition of the bridge tunnel can be monitored in real time, and the health state of the bridge tunnel can be monitored in real time.

If the acousto-optic modulator is not used for frequency shifting f0, Δ f1 is 0, and (f2-f3) is (f3-f 1). Then no matter how the strain of the optical fiber changes, the energy will be transferred equally in the direction of f2 → f3 → f1, and finally the energy of f3 will not change. Although the role of the acousto-optic modulator is very important at this time and the acousto-optic modulator is the most expensive module in the overall system. This is also a reason that hinders further promotion of this system. On the premise of ensuring the system performance, the cost is reduced by designing a new scheme, which becomes a very important problem.

Disclosure of Invention

The technical problem to be solved by the present invention is to solve the above-mentioned deficiencies of the prior art and to provide a filter-based optical fiber strain system with low cost.

In order to solve the technical problems, the invention adopts the technical scheme that: an optical fiber strain system based on a filter comprises a light source, a coupler, a circulator, a demodulation module, an electro-optic modulator, a filter and a sensing optical fiber, wherein the light source generates light with the frequency of f0, the coupler is connected with the light source, and the light of the light source is split into two beams of light with the same frequency; the coupler is also connected with a circulator and a photoelectric regulator, wherein the photoelectric modulator shifts the frequency of light to two sides simultaneously to convert the light into dual-frequency light, the dual-frequency light is respectively f 1-f 0- Δ f, f2-f 0 +/Δ f, the rear end of the photoelectric modulator is connected with a filter, the filter is used for filtering the light with the frequency of f1 and transmitting the light with the frequency of f2, the filter is connected with an optical cable, and the circulator is connected with a sensing optical fiber and an adjusting module; the adjustment module detects the stress change according to the light energy change with the judgment frequency f 1.

Further, the bandwidth of the filter is within 1 nm.

Further, the value range of delta f is 0-100 MHz.

The technical scheme shows that the invention has the following advantages: f1 is directly filtered by the filter, so that the hardware cost is greatly reduced, and the system structure is simplified.

Drawings

Fig. 1 shows the structure of a stress optical fiber strain monitoring system in the prior art.

Fig. 2 is a schematic structural diagram of the present invention.

Detailed Description

The following describes an embodiment of the present invention with reference to fig. 2.

The optical fiber strain system based on the filter comprises a light source, a coupler, a circulator, a demodulation module, an electro-optic modulator, a filter and a sensing optical fiber, wherein the light source generates light f0 with the frequency of 129085.6GHz and the wavelength of 1549.36nm, the coupler is connected with the light source, and the light of the light source is split into two beams of light with the same frequency, and the two beams of light can be split according to the intensity of 1: 1. The coupler also connects the circulator and the photo-adjuster, wherein the photo-modulator shifts the frequency of the light to two sides simultaneously to become dual-frequency light f1 and f2, the frequency of f1 is 129077.2GHz, the wavelength is 1579.46nm, the frequency of f2 is 129093.9GHz, and the wavelength is 1549.26 nm. The offset is controlled to be 0-100 MHz, the back end of the electro-optical modulator is connected with a filter, and the bandwidth of the filter is within 1 nm. By controlling the cut-off wavelength of the filter, light with the frequency f1 is filtered out, and light with the frequency f2 can be transmitted through the filter, the filter connecting optical cable, the circulator connecting the sensing optical fiber and the adjusting module.

Thus, the light with frequencies f0 and f2 meet in the sensing fiber and energy transfer occurs in the following directions: f2 → f 0. The demodulation module can monitor the strain change of the sensing optical fiber in real time by judging the energy change of f0, so that the strain condition of the bridge tunnel can be monitored in real time, and the health state of the bridge tunnel can be monitored in real time. The invention filters out f1 directly through the filter. An acousto-optic modulator is cancelled, and the equipment cost is reduced.

Claims

1. A filter-based optical fiber strain system, comprising: the device comprises a light source, a coupler, a circulator, a demodulation module, an electro-optic modulator, a filter and a sensing optical fiber, wherein the light source generates light with the frequency of f0, the coupler is connected with the light source, and the light of the light source is split into two beams of light with the same frequency; the coupler is also connected with a circulator and a photoelectric regulator, wherein the photoelectric modulator shifts the frequency of light to two sides simultaneously to convert the light into dual-frequency light, the dual-frequency light is respectively f 1-f 0- Δ f, f2-f 0 +/Δ f, the rear end of the photoelectric modulator is connected with a filter, the filter is used for filtering the light with the frequency of f1 and transmitting the light with the frequency of f2, the filter is connected with an optical cable, and the circulator is connected with a sensing optical fiber and an adjusting module; the adjustment module detects the stress change according to the light energy change with the judgment frequency f 1.

2. The filter-based fiber strain system of claim 1, wherein: the bandwidth of the filter is within 1 nm.

3. The filter-based fiber strain system of claim 1, wherein: the value range of delta f is 0-100 MHz.