CN100588913C - A Simplified Multiplexing White Light Interference Optical Fiber Sensing and Demodulation Device - Google Patents

Abstract

The invention provides a simplified multiplexing white light interference fiber sensing demodulating device, which comprises a single-fiber two-way optical transmitting/receiving module, an optical fiber resonant cavity, a single-mode transmission fiber, and an optical fiber sensing array, wherein the single-fiber two-way optical transmitting/receiving module is composed of a semiconductor light source as the transmitting terminal, a semiconductor photodetector as the receiving terminal and related devices packaged together; and an optical fiber annular cavity is composed of an optical fiber coupler, an optical fiber self-focusing lens and a movable corner reflector. The device can achieve enquiry and measurement of a plurality of optical fiber sensors by embedding the single-fiber two-wayoptical transmitting/receiving module and the optical fiber resonant cavity in the single-mode optical fiber, and has the advantages of simple structure, easy implementation, no length restriction ofthe transmission cable, no influence caused by the external environment, and good stability and reliability. The device can be used for the measurement of physical quantities such as distributed deformation, strain and temperature, and can be used for multi-task sensing, multi-element sensing, local strain sensing, large-scale deformation sensing, etc.

Description

A Simplified Multiplexing White Light Interference Optical Fiber Sensing and Demodulation Device

(1) Technical field

The invention relates to a measuring device, in particular to a simplified multiplexing optical fiber array sensor for sensing and demodulation of a white light optical fiber interferometer.

(2) Background technology

Fiber-optic interferometers using low-coherence, broadband light sources are often referred to as white-light fiber interferometers. A typical optical fiber white light interferometer is shown in Figure 1. Its structure is to use optical fiber to build a Micheslon interferometer, and use a wide-spectrum light source LED or ASE to drive the interferometer to provide light energy for it, and detect white light interference through a detector. The stripes realize the measurement of the physical quantity to be measured. Its working principle is as follows. After the broadband light emitted by the broadband light source 11 enters the single-mode fiber, it is divided into two beams by the 3dB single-mode fiber 2×2 coupler 13, and one beam enters the single-mode fiber 14 used as the measuring arm. After being reflected by the optical reflection surface 15 at the rear end, it returns along the original path, passes through the single-mode optical fiber 14 and the coupler 13 to reach the photodetector 12, and this beam of light is called the measurement signal light; the light emitted by the light source 11 is shunted by the coupler 13 Another beam of light enters the single-mode connecting optical fiber 16 and the self-focusing lens 17 as the reference arm, and returns to the photodetector 12 along the same path after being reflected by the moving mirror 18. This beam of light is called the reference signal light . The measurement signal light and the reference signal light coherently superimpose on the surface of the detector. Since the coherence length of the broadband light source is very short, about several microns to tens of microns, only when the optical path difference between the reference signal light and the measurement signal is less than the light source When the coherence length is greater than the coherence length, coherent superposition will be generated, and a white light interference pattern will be output (see Figure 2).

As shown in Figure 2, the characteristic of white light interference fringes is that there is a main maximum value, called the central fringe, which corresponds to zero optical path difference, that is, when the optical path of the reference beam and the measurement beam are equal, it is called The reference beam and the measuring beam have an optical path matching relationship. By changing the delay amount of the fiber delay line and changing the optical path of the reference signal, the central interference fringe can be obtained. The position of the central fringe provides a reliable absolute position reference for the measurement. When the optical path of the measuring beam changes due to the influence of the external physical quantity to be measured, only the position of the white light interference fringe obtained by scanning the reference arm optical path changes. Gets the absolute value of the measured physical quantity. Compared with other fiber optic interferometers, in addition to the advantages of high sensitivity, intrinsic safety, and anti-electromagnetic field interference, the biggest feature is that it can perform absolute measurements on pressure, strain, and temperature. Therefore, the white light interferometric fiber optic interferometer is widely used in the measurement of physical quantities, mechanical quantities, environmental quantities, chemical quantities, and biomedical quantities.

In order to solve the multiplexing problem of optical fiber interferometer, people have carried out various researches. The multiplexing technologies that have been developed include: time division multiplexing technology (TDM), frequency division multiplexing technology (FDM or FMCW), wave Division Multiplexing (WDM) and Space Multiplexing (SDM).

The time division multiplexing technology (TDM) developed by Jackson et al [Santos, J.L., Jackson, D.A., Coherence sensing of time-addressed optical-fiber sensors illuminated by a multimode laser diode Appl. Opti, 30, 5068-5076, 1991] is A multiplexing technology for addressing by utilizing the optical path difference of sensing units on the same optical fiber bus, that is, the delay effect of optical fibers on light waves. The technical solution is: when the optical pulse emitted by the multimode laser diode is shorter than the transmission time between adjacent sensors on the optical fiber bus and injected into the input end of the optical fiber bus, since the distances between the sensing units on the bus and the optical pulse transmitting end are different, the The terminal of the optical fiber bus will receive a series of pulses, and the information contained in each optical pulse corresponds to a sensing unit on the optical fiber bus, and the time delay of the optical pulse reflects the address distribution of the sensing unit. If the continuous optical path scanning of the white light sensing unit can be completed within the time of the light pulse width, the sensing information of the sensor can be obtained. This method has complex structure, limited number of multiplexing, small measurement range and low measurement accuracy.

Wayne V. Sorin, Mountain View et al. [Multiplexed sensing using optical coherence reflectrometry, United States Patent, Patent Number 5,557,400, 1996] used white light fiber multiplexing interferometry to measure tension, strain, displacement and other parameters, but the white light used in the method The light source and the photoelectric detection device are independent of each other, and the devices used in the photoelectric detection device are many and complex in structure. Other similar technologies include W.Don Morison, etc. [Fiber optic sensor usable over wide range of gage lengths, United States Patent, Patent Number6870975, 2005]; Ralph Posey, etc. [Integrated fiber optic strain sensing using low-coherence wavelength-encoded addressing , United States Patent, Patent Number6289740, 2001] also uses white light optical fiber multiplexing interference technology to measure parameters such as strain and displacement. This method mainly uses the method of adjusting the wavelength of the light source to achieve measurement. Domestic documents such as the optical amplification-based Fizeau strain sensor frequency division multiplexing system and method disclosed in the Chinese Patent Gazette (publication number CN1553273A) and the like. The above-mentioned multiplexing method of the optical fiber interferometer is mainly based on the time division multiplexing technology, and a large number of technical patents and technical papers have been published.

The applicant disclosed the multiplexing optical fiber interferometer and its nesting construction method in 2006 (Chinese patent publication number: CA1963399A), invented the all-fiber interferometer optical fiber and its implementation method that can construct sensor arrays and networks, and solved the problem of optical fiber The multiplexing problem of the interferometer; the low-coherence twisted Sagnac-like optical fiber deformation sensing device disclosed by the applicant in 2007 (Chinese Patent Publication No.: 101074867A), which is mainly used to solve the problem of anti-destruction in the process of laying out the optical fiber sensor array The problem. In the above applications, especially when the white light interferometer is connected with a fiber optic sensor array, the optical paths of the local demodulation interferometer and the remote sensing interferometer are matched to realize interrogation and demodulation of the fiber optic sensor array. In this way, the sensing interferometer array can be completely passive, and the advantage is that the multiple interference signals output in the array are insensitive to the change of the length of the connecting fiber between the local demodulation interferometer and the sensor array, which enhances the stability of the measurement and reliability.

However, in the above interferometer structures based on space division multiplexing, most of the local demodulation interferometers use discrete interferometer structures such as Michelson interferometers and Mach-Zehnder interferometers. They usually have two independent optical transmission channels for optical path tuning and matching. However, because it does not have a common optical path structure, it is easily affected by environmental factors (such as temperature and vibration), resulting in inconsistent changes in the optical path of the two optical paths, which affects the demodulation of the sensor signal and reduces the signal resolution of the interferometer. Adjusting the sensitivity will reduce the measurement accuracy, and the long-term stability and reliability cannot be guaranteed; at the same time, the structure of the interferometer is also relatively complicated, which is not suitable for the practical application of the interferometer.

(3) Contents of the invention

The purpose of the present invention is to solve the complex structure of this type of optical fiber interferometer, the optical fiber cable used for connection is related to the measurement, the measurement reliability is poor, and the stability is low. A simplified multiplexing white light interference optical fiber sensing and demodulation device.

The purpose of the present invention is achieved like this:

The composition of the simplified multiplexing white light interference optical fiber sensing and demodulation device of the present invention includes a single-fiber bidirectional optical transceiver module 1, an optical fiber ring cavity 2, a single-mode transmission optical fiber 3, and an optical fiber sensor array 4; the single-fiber bidirectional The optical transceiver module 1 is mainly composed of a semiconductor light source 102 for emission and a semiconductor photodetector 103 for reception. The semiconductor photodetector 103 realizes simultaneous The output of the light source signal and the detection of the optical interference signal; after the wide-spectrum light emitted by the single-fiber bidirectional optical transceiver module 1 enters the single-mode transmission fiber, it is divided into two beams through the optical fiber ring cavity 2, and one beam of light passes through the optical fiber ring cavity 2 After the single-mode optical fiber coupler 201, it directly enters the optical fiber sensor array 4 composed of a single-mode transmission optical fiber 503 and an optical reflection surface 504 connected in series, as a measuring beam; another beam of light passes through two self-focusing lenses of the optical fiber ring cavity 2 202 and the scanning total reflection prism 203 re-enter the single-mode fiber coupler 201 and are divided into two beams, one beam continues to circulate around the optical fiber ring cavity, and the other beam enters the fiber sensor array 4 as a reference beam and is transmitted by After being reflected by the optical reflector 504, it returns to the single-fiber bidirectional optical transceiver module; the single-fiber bidirectional optical transceiver module 1 realizes multiplexing white light interference optical fiber sensing and demodulation according to the interference signal of the returned measuring beam and reference beam.

The composition of the single-fiber bidirectional optical transceiver module 1 includes a semiconductor light source 102, a semiconductor photodetector 103, a heat sink 104, an optical fiber 105, an adhesive epoxy resin 106 and a module electrical pin encapsulated in a module package housing 101. 109 poses. The semiconductor light source 102 is solidified on the semiconductor photodetector 103 , and the two are led out by three electrical pins 109 , one of which is multiplexed by the semiconductor light source 102 and the semiconductor photodetector 103 . The heat sink 104 is connected under the semiconductor photodetector 103 , and the optical fiber 105 is connected with the epoxy resin 106 above the semiconductor light source 102 , the semiconductor light source 102 emits a light beam 107 , and the semiconductor photodetector 103 receives a light beam 108 .

After the wide-spectrum light emitted by the single-fiber bidirectional optical transceiver module 1 enters the single-mode fiber, it is divided into two beams through the fiber ring cavity 2, and one beam of light passes through the fiber coupler 201 in the fiber ring cavity 2 and directly enters the optical fiber ring cavity 2. The sensor array 4 that is made up of N section single-mode optical fiber 503 and N optical partial reflection surfaces 504 as sensor 5, as measuring light beam; Another beam of light passes through two self-focus rate lenses 202 of optical fiber ring cavity 2 and scans the entire The reflective prism 203 reenters the single-mode fiber coupler 201 and is divided into two light beams. One light beam continues to circulate around the fiber resonant cavity, and the other light beam enters the optical fiber sensor array 4 for transmission and is reflected by the optical partial reflector 504. Back to the single-fiber bidirectional optical transceiver module 1.

Described optical fiber annular cavity 2 is made up of a 2 * 2 single-mode fiber coupler 201, two single-mode self-focusing lenses 202 and a scanning total reflection prism 203; The splitting ratio of single-mode fiber coupler 201 can be in 1%～ 99% range selection.

The optical fiber sensing array 4 is composed of several optical fiber sensors 5 connected in series from end to end.

The optical fiber sensor 5 is composed of a length of single-mode optical fiber 503 with optical fiber ferrules 501 at both ends.

The connection method of the optical fiber sensor array 4 is that the optical fiber sensor 5 is connected with other optical fiber sensors 5 with optical fiber ferrules 501 or connecting optical fibers 3 through the optical fiber sleeve 502 .

The optical fiber devices all work in a single-mode state.

The basic principle of the method of the present invention is the principle of white light optical fiber Michelson interferometer.

After entering the single-mode optical fiber, the wide-spectrum light emitted by the single-fiber bidirectional optical transceiver module 1 is divided into two beams by the single-mode optical fiber 2×2 coupler 201 in the optical fiber ring cavity 2, as shown in FIG. 4 . One of them is used as a measuring beam, and after passing through the fiber coupler 201, it directly enters the sensor array 4 composed of N sections of single-mode optical fiber 503 and N optical reflection surfaces 504 as the sensor 5; the other beam passes through the optical fiber ring cavity 2, the two self-focusing ratio lenses 202 and the scanning total reflection prism 203 reenter the single-mode fiber coupler 201 and are divided into two beams, one beam continues to circulate in the fiber resonator, and the other beam is used as a reference beam After entering the optical fiber sensor array 4 and being reflected by the optical partial reflector 504, it returns to the single-fiber bidirectional optical transceiver module 1 .

The initial length of the fiber resonator can be set as L ₀ , the length of the fiber sensor in the middle of the N partial reflectors is L _j (j=1, 2, 3, ... N), and this length is the same as L ₀ is close to but slightly longer, and the length of each fiber optic sensor has a slight change. At this time, the optical path length in the adjustable fiber resonator is nL ₀ +2X, where X is the optical path between the scanning prism and the double gradient index lens, and its value can be adjusted by controlling the scanning prism. When the jth optical fiber sensor is interrogated by the light source signal, the reference signal obtained by passing through the fiber resonator and the left partial reflector of the jth optical fiber sensor has the following three forms:

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="L"\; filenames="C2008101368260013H2.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="L"\; filenames="C2008101368260013H2.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="L"\; filenames="C2008101368260013H2.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="L"\; filenames="C2008101368260013H2.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula: n is the refractive index of the fiber core, and L is the length of the connecting cable.

The measurement signal obtained through the fiber resonator and the right partial reflector of the jth fiber sensor is in the following form:

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Comparing the reference signal with the measured signal gives:

nL ₀ +2X _j =nl _j , j=1, 2, 3... (5)

There is also a second reference signal type, namely in the case of L ₀ ≈2l _sensor :

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="L"\; filenames="C2008101368260013H2.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="L"\; filenames="C2008101368260013H2.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

The measurement signal does not change:

$<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nL</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Comparing the reference signal with the measured signal in this case gives:

nL ₀ +2X _j =2nl _j , j=1, 2, 3... (9)

It can be seen from formula (5) and formula (9) that when the optical paths of the measurement signal light and the reference signal light match, coherent superposition will occur in the single-fiber bidirectional optical transceiver module 1. Since the coherence length of the broadband light source is very short, It is about a few microns to tens of microns. Only when the optical path difference between the reference signal light and the measurement signal is smaller than the coherence length of the light source, coherent superposition will occur and a white light interference pattern will be output.

At the same time, it can also be seen from formulas (5) and (9) that the optical path matching relationship of the jth optical fiber sensor has nothing to do with the length L of the connecting fiber optic cable and the length l of other fiber optic sensors, that is, the length of the connecting fiber optic cable Unrestricted, while the influence of the environment on the connecting fiber optic cable is eliminated. In addition, the sensors are independent from each other due to the optical path relationship, and there is no crosstalk.

When the optical fiber sensor l _j is deformed by external factors such as stress and strain, adjust the adjustable parameter X _j in the optical fiber resonant cavity to match the optical path so that:

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="nl\; j"\; filenames="C2008101368260014H1.png"\; state="\{\{state\}\}">nl</figure-callout></span><figure-callout\; id="2"\; label="nl\; j"\; filenames="C2008101368260014H1.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2,3</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Or ΔX _j =Δ(nl _j ), j=1, 2, 3... (11)

Suppose the optical fiber sensor l ₁ changes to l ₁ +Δl ₁ , l ₂ changes to l ₂ +Δl ₂ ,...l _N changes to l _N +Δl _N , then the gauge factor of the entire sensor can be obtained

${\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="l"\; filenames="C2008101368260013H2.png,C2008101368260014H1.png"\; state="\{\{state\}\}">l</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="l"\; filenames="C2008101368260014H1.png"\; state="\{\{state\}\}">l</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Since the interference phenomenon of the fiber optic interferometer using a broadband light source only occurs within the coherence length, corresponding to a few microns to tens of microns near the optical path matching condition, multiple fiber interferometers can be connected in series, and By making the interference signals corresponding to different optical fiber sensors separate from each other and distinguishing them separately, the multiplexing of modulation and demodulation of the optical fiber interferometer can be realized. The optical path experienced by the measuring beam passing through different optical branches and different reflecting surfaces can have a one-to-one matching relationship with the optical path of the reference beam, so that the generated white light interference fringes are independent of each other in the optical path scanning space and do not interfere with each other. Based on the above ideas, the modulation and demodulation of the multiplexed self-optical fiber interferometer can be realized.

Advantages and characteristics of the present invention are:

(1) The present invention is based on the multiplexing technology of fiber optic interferometer modulation and demodulation, by embedding a single-fiber bidirectional optical transceiver module and a fiber resonator, the interrogation of multiple fiber optic interference sensors can be realized in one fiber Inquiry and measurement greatly simplifies the optical path structure of the measurement system and is easy to implement.

(2) The present invention adopts the bidirectional common optical path structure, makes the length of connecting optical cable between the single-fiber bidirectional optical transceiver module, the optical fiber resonator, the optical fiber sensing array and the optical fiber sensor in the array unrestricted, also eliminates simultaneously The impact of the environment on the connecting optical cable improves the anti-interference ability of the system and enhances the reliability and stability of the measurement.

(3) The simplified multiplexing white light fiber interferometer constructed in the present invention can make the number of multiplexed sensors reach nearly a hundred by selecting a wide-spectrum light source with suitable power and a suitable optical fiber partial reflector, and realize the optical fiber interferometer. The array arrangement of sensors greatly simplifies the complexity of the system, reduces the test cost, ensures the real-time performance of the test system, and improves the reliability of the measurement.

(4) The optical fiber materials and devices used in the present invention are all standard optical fiber communication components, which are cheap, easy to obtain, and conducive to popularization.

The invention proposes a simplified multiplexing white light fiber optic interferometer modulation and demodulation construction method, and thus constructs a fiber optic interferometer sensor array. The core content of the present invention is to use the idea of integration, based on white light interference technology, by embedding two-way optical transceiver components and optical fiber ring cavity, to realize the construction of optical fiber white light interferometer in a single optical fiber, and the multiplexing and demodulation of optical fiber sensors . Specifically, the white light source and white light interference signal detection circuit are packaged in a single-fiber bidirectional optical transceiver module device by using the packaging method of light source back detection, realizing the multiplexing of white light source and white light interference signal detection; Using the optical path tuning function of the optical fiber ring cavity, multiple reference optical signals with different optical paths are simultaneously output to complete the demodulation of multiple optical fiber sensors.

(4) Description of drawings

Figure 1 is a schematic diagram of a typical white light fiber Michelson interferometer.

Fig. 2 is a schematic diagram of a typical white light interference signal.

Fig. 3 is a structural schematic diagram of the present invention.

Fig. 4 is a schematic diagram of the structure of an optical fiber ring cavity.

Fig. 5 is a schematic diagram of the structure of the optical fiber sensor and its connection method.

Fig. 6 is a schematic structural diagram of a single-fiber bidirectional optical transceiver module.

(5) Specific implementation methods

The present invention is described in more detail below in conjunction with accompanying drawing example:

Embodiment 1: as shown in FIG. 3 . The simplified multiplexing white light optical fiber interferometer is composed of a single-fiber bidirectional optical transceiver module 1, an optical fiber resonant cavity 2, an optical fiber cable 3 for connection, and an optical fiber array sensor 4.

After entering the single-mode optical fiber, the wide-spectrum light emitted by the single-fiber bidirectional optical transceiver module 1 is divided into two beams by the single-mode optical fiber 2×2 coupler 201 in the optical fiber ring cavity 2, as shown in FIG. 4 . One of them is used as a measuring beam, and after passing through the fiber coupler 201, it directly enters the sensor array 4 composed of N sections of single-mode optical fiber 503 and N optical reflection surfaces 504 as the sensor 5; the other beam passes through the optical fiber ring cavity 2, the two self-focusing ratio lenses 202 and the scanning total reflection prism 203 reenter the single-mode fiber coupler 201 and are divided into two beams, one beam continues to circulate in the fiber resonator, and the other beam is used as a reference beam After entering the optical fiber sensor array 4 and being reflected by the optical partial reflector 504, it returns to the single-fiber bidirectional optical transceiver module 1 . When scanning the total reflection prism 203 for optical path scanning, the light signals reflected by the front and rear end faces 504 of the sensor are matched with the optical path, that is, the position of the scanning total reflection prism 203 when the generated white light interference peak is specific to the sensor array or the network The corresponding length of the sensor. When a certain sensor produces strain or displacement due to the effect of parameters such as temperature and stress, its corresponding optical path scanning position where the white light interference peak appears also changes accordingly. Record the position value before and after the change, and according to the conversion relationship, you can perform Sensory measurement of parameters.

The single-fiber bidirectional optical transceiver module 1 is a high-performance optoelectronic device, and the functions of the semiconductor light source 102 and the semiconductor photodetector 103 are integrated in a standard package. As shown in Figure 6, the functions of the single-fiber bidirectional optical transceiver module are integrated in a standard 1×3 pin package. 109. Simultaneously implement the output of the light source signal and the detection of the light interference signal. The semiconductor light source 102 converts the driving current into signal light and supplies it to the interferometer as a light energy source; the semiconductor photodetector 103 converts the light signal into a current, and after amplification and filtering, extracts the white light interference signal. The device utilizes an optical fiber to realize bidirectional light emission and light detection functions, which can improve the utilization efficiency of the optical fiber.

As shown in Figure 4, the two self-focusing lenses 202 in the fiber resonator 2 have an insertion loss range of 0.5dB, and the span between the self-focusing lens and the scanning total reflection mirror is 3mm-70mm (corresponding to the reference optical path range 6mm- 140mm), the loss between them is 4-8dB, and the optical path length of the resonant cavity is selected at 1990mm, which is approximately equal to twice the length of the optical fiber sensor.

The optical fiber sensing array 4 is composed of six optical fiber sensors 5 connected in series end to end. Each optical fiber sensor 5 is composed of a single-mode optical fiber 503 with a length of approximately 1000 mm, and has a single-mode optical fiber ferrule 501 at both ends. The connection method of the optical fiber sensor array 4 adopts the optical fiber sleeve 502, and the optical fiber sensor 5 is connected in series with other optical fiber sensors 5 or the connecting optical fiber 3 with the optical fiber ferrule 501, and the two optical fiber ferrules connected by the optical fiber sleeve An optical reflective surface 504 with an optical reflectivity of 1% to 3% is formed between them, as shown in FIG. 5 . The fiber coupler 201 is selected as a 3dB fiber 2×2 coupler. For the modulation and demodulation principle of the multiplexing white light fiber interferometer, please refer to the content of the invention. The device can be used for the measurement of tension, displacement and temperature.

Claims (5)

1. A simplified multiplexing white light interference optical fiber sensing and demodulation device, which consists of a single-fiber bidirectional optical transceiver module (1), an optical fiber ring cavity (2), a single-mode transmission optical fiber (3), and an optical fiber sensor array (4); It is characterized in that: described single-fiber bidirectional optical transceiver module (1) is mainly composed of a semiconductor light source (102) as emission, a semiconductor photodetector (103) as reception and is packaged together to form, semiconductor The photodetector (103) simultaneously realizes the output of the light source signal and the detection of the optical interference signal through the three electrical pins (109) multiplexed with the semiconductor light source (102); After the light enters the single-mode transmission fiber, it is divided into two beams through the fiber ring cavity (2), and one of the beams passes through the single-mode fiber coupler (201) in the fiber ring cavity (2), and directly enters the single-mode transmission fiber ( 503) and the optical fiber sensor array (4) that optical reflection surface (504) forms in series, as measuring light beam; Another beam of light, through two self-focusing lenses (202) and scanning total reflection prism of optical fiber annular cavity (2) (203) re-enters the single-mode fiber coupler (201) and is divided into two beams, one beam continues to circulate around the ring in the optical fiber ring cavity, and the other beam enters the fiber sensor array (4) as a reference beam and is transmitted by The optical reflective surface (504) returns to the single-fiber bidirectional optical transceiver module after reflection; the single-fiber bidirectional optical transceiver module (1) realizes multiplexing white light interference optical fiber sensing and demodulation according to the interference related signal of the returned measuring beam and reference beam . 2. The simplified multiplexing white light interference optical fiber sensing and demodulation device according to claim 1, characterized in that: the composition of the single-fiber bidirectional optical transceiver module (1) includes packaging in the module packaging shell ( Semiconductor light source (102), semiconductor photodetector (103), heat sink (104), optical fiber (105), bonding epoxy resin (106) and module electric pin (109) in 101); Semiconductor light source (102 ) is solidified on the semiconductor photodetector (103), the two are drawn by three electrical pins (109), and one of the electrical pins is multiplexed by the semiconductor light source (102) and the semiconductor photodetector (103); Connect the heat sink (104) under the detector (103), connect the optical fiber (105) with adhesive epoxy resin (106) on the semiconductor light source (102), the semiconductor light source (102) emits the light beam (107), and the semiconductor photodetector The device (103) receives the light beam (108). 3. The simplified multiplexing white light interference optical fiber sensing and demodulation device according to claim 2, characterized in that: the splitting ratio of the single-mode fiber coupling (201) is selected within the range of 1% to 99%. . 4. The simplified multiplexing white light interference optical fiber sensing and demodulation device according to claim 3, characterized in that: the optical fiber sensor (5) has a length of any two ends with an optical fiber ferrule (501) Composed of single-mode fiber (503). 5. The simplified multiplexing white light interference optical fiber sensing and demodulation device according to claim 4, characterized in that: the connection structure of the optical fiber sensor array (4) is: the optical fiber sensor (5) passes through the optical fiber sleeve The tube (502) is connected with other optical fiber sensors (5) or single-mode transmission optical fibers (3) with optical fiber ferrules (501).

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