CN106802160B - Fiber grating sensing demodulation system and method based on fork-shaped interference pattern - Google Patents
Fiber grating sensing demodulation system and method based on fork-shaped interference pattern Download PDFInfo
- Publication number
- CN106802160B CN106802160B CN201710149972.0A CN201710149972A CN106802160B CN 106802160 B CN106802160 B CN 106802160B CN 201710149972 A CN201710149972 A CN 201710149972A CN 106802160 B CN106802160 B CN 106802160B
- Authority
- CN
- China
- Prior art keywords
- light
- fork
- light beam
- interference pattern
- shaped interference
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000000835 fiber Substances 0.000 title claims abstract description 74
- 238000000034 method Methods 0.000 title claims abstract description 39
- 230000003287 optical effect Effects 0.000 claims abstract description 56
- 238000005259 measurement Methods 0.000 claims description 34
- 239000013307 optical fiber Substances 0.000 claims description 22
- 230000005540 biological transmission Effects 0.000 claims description 6
- 238000002310 reflectometry Methods 0.000 claims description 5
- 238000005253 cladding Methods 0.000 claims description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000001934 delay Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000004304 visual acuity Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35303—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using a reference fibre, e.g. interferometric devices
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35329—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using interferometer with two arms in transmission, e.g. Mach-Zender interferometer
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optical Transform (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention provides a fiber grating sensing demodulation system and a demodulation method based on a fork-shaped interference pattern, which comprises a reference light path and a measuring light path, wherein a Gaussian beam is generated in the reference light path; the fiber grating is introduced into the measuring light path, a light beam with orbital angular momentum is generated through the spiral phase plate, and light in the reference light path and light in the measuring light path interfere at the light splitting plate to generate a fork-shaped interference pattern. When the external to-be-measured changes, the propagation of light in the fiber bragg grating generates phase delay, so that the phase difference between the reference light path and the measuring light path changes, the fork-shaped interference pattern moves at the bifurcation point, the change of the fork-shaped interference pattern is detected and recorded in real time through the CCD camera, and finally the corresponding relation between the external to-be-measured and the fork-shaped interference pattern is obtained. The invention does not need the traditional optical instrument spectrometer and the like to demodulate signals, reduces the cost of the sensing system and applies the fiber grating to more engineering fields.
Description
Technical Field
The invention relates to a fiber grating sensing demodulation system and a demodulation method based on a fork-shaped interference pattern, and belongs to the technical field of photoelectric detection.
Background
With the rise of internet and internet of things technologies, the requirements on sensors are higher and higher, and the development of the sensors is mainly sensitive, high-precision, small in size and intelligent. The traditional sensor has poor high-temperature and high-pressure resistance and is easy to be interfered by electromagnetic radiation in the emerging application fields, and the fiber grating sensor has the advantages of high sensitivity, portability, distributed measurement, electromagnetic interference resistance and the like as a novel sensor, and is very suitable for the fields of constructional engineering, aerospace, biomedicine, power systems and the like. The fiber grating sensor has many advantages that can be applied to the occasions where the traditional sensor is not suitable, and is a research hotspot of the current sensor technology, and the key technology of the fiber grating sensor is the design of a demodulation system. At present, an optical instrument spectrometer is generally adopted for demodulating the optical fiber grating sensing signal, but the optical instrument spectrometer is not suitable for practical engineering application due to large volume, high price, low scanning speed and harsh use conditions. Therefore, the optical fiber grating sensing demodulation method which has industrial application value, low cost and portability is provided, and the method has important significance.
Disclosure of Invention
The invention aims to overcome the defects of the conventional fiber grating sensing signal demodulation method, provides a fiber grating sensing signal demodulation system and a demodulation method with practical engineering application values, and meets the requirements of high precision, portability and low cost.
The technical scheme is as follows: a fiber grating sensing demodulation system based on a fork-shaped interference pattern, comprising:
a laser for generating a light beam;
the coupler is used for splitting the incident light beam, and the light beam emitted by the laser enters the coupler;
the measuring optical path is used for converting the incident light beam into a light beam with orbital angular momentum;
the reference light path is used for converting the incident light beam into a Gaussian light beam, and the light beam split by the coupler is respectively incident into the reference light path and the measuring light path;
the beam splitter is used for generating a fork-shaped interference beam, and the beams in the reference light path and the measurement light path are incident into the beam splitter to generate interference;
the CCD camera is used for detecting and recording the fork-shaped interference light beams into fork-shaped interference pattern signals in real time, and the CCD camera receives the fork-shaped interference light beams emitted by the light splitting plate;
the measuring light path sequentially comprises a fiber grating, a first collimator, a spiral phase plate and a reflector;
the reference light path includes a second collimator.
Further, the laser is a distributed feedback laser, the coupler is a single-mode fiber coupler, the light beam in the reference light path is transmitted through a single-mode fiber, the first collimator and the second collimator convert the incident light beam into parallel light, the spiral phase plate converts the input parallel light beam into an orbital angular momentum light beam and outputs the orbital angular momentum light beam, and the reflector changes the propagation direction of the light beam and emits the orbital angular momentum light beam output by the reflector to the light splitting plate.
The invention also provides a fiber grating sensing demodulation method based on the fork-shaped interference pattern, which comprises the fiber grating sensing demodulation system based on the fork-shaped interference pattern and also comprises the following steps:
s1: the laser generates a light beam to be emitted into the coupler;
s2: the light beams split by the coupler are respectively emitted into a measuring light path and a reference light path;
s3: the light beam is converted into a light beam with orbital angular momentum through the measuring light path, the light beam is converted into a Gaussian light beam through the reference light path, and the light beam with orbital angular momentum and the Gaussian light beam are respectively emitted into the light splitting plate to generate interference to form a fork-shaped interference light beam;
s4: the CCD camera converts the fork-shaped interference light beam emitted by the light splitting plate into a fork-shaped interference pattern signal;
s5: the external to-be-measured changes, the propagation of the light beam in the fiber bragg grating generates phase delay, so that the phase difference between the light beam with orbital angular momentum emitted by the measuring light path and the Gaussian light beam emitted by the reference light path changes, the fork-shaped interference pattern moves at the bifurcation point, and the signals of the fork-shaped interference pattern are continuously detected in real time by the CCD camera and output to the computer 7;
s6: the computer 7 records the fork-shaped interference pattern signal to obtain the corresponding relation between the external to-be-measured and the fork-shaped interference pattern.
Further, the fiber grating has a length of 0.16mm, a grating period of 0.529 μm, a core refractive index of 1.4681, a cladding refractive index of 1.4628, and a maximum refractive index difference of 0.0053.
Further, the laser is a distributed feedback laser, the coupler is a single-mode fiber coupler, the light beam in the reference light path is transmitted through a single-mode fiber, the first collimator and the second collimator convert the incident light beam into parallel light, the spiral phase plate converts the input parallel light beam into an orbital angular momentum light beam and outputs the orbital angular momentum light beam, and the reflector changes the propagation direction of the light beam and emits the orbital angular momentum light beam output by the reflector to the light splitting plate.
Further, the center wavelength of the laser is 1550nm, and the coupler is a 2 × 2 single-mode fiber coupler with a splitting ratio of 1:1 and a working wavelength of 1550 nm;
the core diameter of the single-mode optical fiber in the reference light path is 9 micrometers;
the first collimator and the second collimator convert the transmission light beam in the optical fiber into parallel light with a divergence angle not more than 2 degrees;
the working wavelength of the spiral phase plate for converting the input parallel light beams into orbital angular momentum light beams and outputting the orbital angular momentum light beams is 1550 nm;
the reflectivity of the mirror for changing the propagation direction of the light is higher than 85%;
the inverse transmission ratio of the light splitting plate is 1: 1.
The invention has the following beneficial effects:
(1) the optical fiber grating sensing demodulation system based on the fork-shaped interference pattern can realize measurement to be measured from the outside, and compared with the traditional wavelength demodulation method, the optical fiber grating sensing signal demodulation method based on the scheme has the advantages of small volume and low cost and is more suitable for practical engineering application;
(2) according to the optical fiber grating sensing demodulation method based on the fork-shaped interference pattern, the optical delay characteristic of the optical fiber grating is utilized, when the external to-be-measured changes, light can be caused to propagate in the optical fiber grating to generate different phase delays, and the interference effect between a reference light path and a measuring light path is further enhanced, so that the scheme can be used for various optical fiber grating devices with small volume and high sensitivity;
(3) according to the fiber grating sensing demodulation method based on the fork-shaped interference pattern, the performance of a measurement system is improved by introducing the orbital angular momentum light beam and adjusting the light source, the signal receiving device and the like, and the problem that the measurement precision and the application range of a traditional wavelength demodulation method are limited due to the limited resolving power of a spectrometer is solved;
(4) according to the optical fiber grating sensing demodulation method based on the fork-shaped interference pattern, only the stability of the whole device is required to be ensured in the using process, and compared with other methods, a special process is not required, so that the process exploration difficulty is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are only some of the embodiments described in the present application, and that other drawings can be obtained from these drawings by those skilled in the art without inventive effort;
FIG. 1 is a schematic structural diagram of a fiber grating sensing demodulation system and a demodulation method based on a fork-shaped interference pattern according to the present invention;
FIG. 2(a) is an interference pattern when the phase difference between the reference optical path and the measurement optical path is 0; FIG. 2(b) is an interference pattern when the reference optical path and the measurement optical path have a phase difference of π/2; FIG. 2(c) is an interference pattern when the reference and measurement optical paths are out of phase by π;
FIG. 3(a) shows the amplitude variation of 1 column on the left side of the bifurcation point of the fork-shaped interference pattern; FIG. 3(b) shows the amplitude variation of the column 1 on the right side of the bifurcation point of the fork-shaped interference pattern, and different curves represent the amplitude distribution of the reference optical path and the measurement optical path under different phase differences;
FIG. 4(a) is the corresponding relationship between the phase difference and the amplitude of the reference optical path and the measurement optical path; fig. 4(b) is a corresponding relationship between the phase difference between the reference optical path and the measurement optical path and the difference between the amplitudes at both sides of the branch point.
Wherein: 1. the device comprises a measuring light path, 2, a reference light path, 3, a laser, 4, a coupler, 5, a light splitting plate, 6, a CCD camera, 11, a fiber grating, 12, a first collimator, 13, a spiral phase plate, 14, a reflector, 21 and a second collimator.
Detailed Description
In order to make the technical solutions and advantages of the present invention clearer, the following describes the technical solutions in the embodiments of the present invention clearly and completely with reference to the drawings in the embodiments of the present invention.
Example 1
A fiber grating sensing demodulation system based on a fork-shaped interference pattern, comprising:
a laser 3 for generating a light beam;
a coupler 4 for splitting the incident light beam, wherein the light beam emitted by the laser 3 enters the coupler 4;
a measuring optical path 1 for converting an incident light beam into a light beam with orbital angular momentum;
the reference light path 2 is used for converting the incident light beam into a Gaussian light beam, and the light beams split by the coupler 4 are respectively incident into the reference light path 2 and the measuring light path 1;
a light splitting plate 5 for generating a fork-shaped interference light beam, wherein the light beams in the reference light path 2 and the measurement light path 1 are incident into the light splitting plate 5 to generate interference;
the CCD camera 6 is used for detecting and recording the fork-shaped interference light beams into fork-shaped interference pattern signals in real time, and the CCD camera 6 receives the fork-shaped interference light beams emitted by the light splitting plate 5;
the measurement light path 1 sequentially comprises a fiber grating 11, a first collimator 12, a spiral phase plate 13 and a reflector 14;
the reference light path 2 comprises a second collimator 21.
Further, the laser 3 is a distributed feedback laser, the coupler 4 is a single-mode fiber coupler, the light beam in the reference light path 2 is transmitted through a single-mode fiber, the first collimator 12 and the second collimator 21 convert the incident light beam into parallel light, the spiral phase plate 13 converts the input parallel light beam into an orbital angular momentum light beam and outputs the orbital angular momentum light beam, and the reflector 14 changes the propagation direction of the light beam and emits the orbital angular momentum light beam output by the reflector 14 to the beam splitter 5.
The CCD camera 6 in the invention is a charge coupled device camera.
A gaussian beam is generated in the reference light path 2; the optical fiber grating 11 is arranged in the measuring optical path 1, light beams are converted into light beams with orbital angular momentum through the spiral phase plate 13, the light beams in the reference optical path 2 and the measuring optical path 1 interfere in the spectroscopic plate 5 to generate fork-shaped interference light beams, when external to-be-measured (such as temperature, strain and the like) changes, phase delay is generated in propagation of the light beams in the optical fiber grating 11, so that phase difference between the reference optical path 2 and the measuring optical path 1 changes, the fork-shaped interference light beams move at the branching points, changes of the fork-shaped interference light beams are detected and recorded in real time through the CCD camera 6 as changes of the fork-shaped interference patterns, finally, corresponding relations between the external to-be-measured and the fork-shaped interference patterns are obtained, the orbital angular momentum light beams are introduced on the basis of a Mach-Zehnder interferometer, and a light source is changed, The signal receiving device replaces a wavelength demodulation method adopted by the traditional fiber grating sensing, namely, the external measurement to be measured is realized through the movement of the resonance wavelength on a spectrometer.
Example 2
The invention also provides a fiber grating sensing demodulation method based on the fork-shaped interference pattern, which comprises the fiber grating sensing demodulation system based on the fork-shaped interference pattern and also comprises the following steps:
s1: the laser 3 generates a light beam which enters the coupler 4;
s2: the light beams split by the coupler 4 are respectively emitted into a measuring light path 1 and a reference light path 2;
s3: the light beam is converted into a light beam with orbital angular momentum through the measuring light path 1, the light beam is converted into a Gaussian beam through the reference light path 2, and the light beam with orbital angular momentum and the Gaussian beam are respectively emitted into the light splitting plate 5 to generate interference to form a fork-shaped interference light beam;
s4: the CCD camera 6 converts the fork-shaped interference light beam emitted by the light splitting plate 5 into a fork-shaped interference pattern signal;
s5: the external to-be-measured changes, the propagation of the light beam in the fiber bragg grating 11 generates phase delay, so that the phase difference between the light beam with orbital angular momentum emitted by the measuring optical path 1 and the Gaussian light beam emitted by the reference optical path 2 changes, the fork-shaped interference pattern moves at the bifurcation point, and the signals of the fork-shaped interference pattern are continuously detected in real time by the CCD camera 6 and output to the computer 7;
s6: the computer 7 records the fork-shaped interference pattern signal to obtain the corresponding relation between the external to-be-measured and the fork-shaped interference pattern.
Further, the fiber grating 11 has a length of 0.16mm, a grating period of 0.529 μm, a core refractive index of 1.4681, a cladding refractive index of 1.4628, and a maximum refractive index difference of 0.0053.
Further, the laser 3 is a distributed feedback laser, the coupler 4 is a single-mode fiber coupler, the light beam in the reference light path 2 is transmitted through a single-mode fiber, the first collimator 12 and the second collimator 21 convert the incident light beam into parallel light, the spiral phase plate 13 converts the input parallel light beam into an orbital angular momentum light beam and outputs the orbital angular momentum light beam, and the reflector 14 changes the propagation direction of the light beam and emits the orbital angular momentum light beam output by the reflector 14 to the beam splitter 5.
Further, the central wavelength of the laser 3 is 1550nm, and the coupler 4 is a 2 × 2 single-mode fiber coupler with a splitting ratio of 1:1 and a working wavelength of 1550 nm;
the core diameter of the single-mode optical fiber in the reference optical path 2 is 9 μm;
the first collimator 12 and the second collimator 21 convert the transmission light beam in the optical fiber into parallel light with a divergence angle not more than 2 degrees;
the working wavelength of the spiral phase plate for converting the input parallel light beams into orbital angular momentum light beams and outputting the orbital angular momentum light beams is 1550 nm;
the reflectivity of the mirror 14 for changing the propagation direction of the light is higher than 85%;
the inverse transmittance ratio of the light-splitting plate 5 is 1: 1.
Example 3
The invention provides a fiber grating sensing demodulation system and a demodulation method based on a fork-shaped interference pattern, and researches the basic characteristics of the fiber grating sensing demodulation system and the demodulation method based on the fork-shaped interference pattern, wherein the fiber grating sensing demodulation system comprises a reference light path 2 and a measuring light path 1, and a Gaussian beam is generated in the reference light path 2; the fiber grating 11 is incident in the measurement optical path 1, and then a light beam with orbital angular momentum is generated by passing through the spiral phase plate 13, and the light beams in the reference optical path 2 and the measurement optical path 1 interfere at the spectroscopic plate 5 to generate a fork-shaped interference pattern. When the external environment is to be measured (such as temperature, strain and the like), the propagation of the light beam in the fiber grating 11 generates phase delay, so that the phase difference between the reference optical path 2 and the measurement optical path 1 changes, the fork-shaped interference pattern moves at the bifurcation point, the change of the fork-shaped interference pattern is detected and recorded in real time through the CCD camera 6, and finally the corresponding relationship between the external environment to be measured and the fork-shaped interference pattern is obtained.
In the above solution, the optical measurement path 1 adopts a fiber grating structure, and utilizes the optical delay characteristic of the fiber grating 11, not the wavelength shift information of the reflection spectrum thereof. Known from the working principle of fiber grating, when a broadband light wave is transmitted in the grating, the incident light is reflected at the corresponding frequency, and the rest light is transmitted from the other end of the grating without being affected. The scheme utilizes the transmissivity of the fiber grating and utilizes the optical delay characteristic of the fiber grating to generate different phase delays under the condition that the reflectivity of the fiber grating is lower than 15 percent. Research shows that the fiber grating 11 has good optical delay effect and can reach picosecond magnitude. When the external environment is to be measured and changed, the propagation of the light beam in the fiber grating 11 will be delayed, and the phase difference between the reference optical path 2 and the measurement optical path 1 will be changed. The length of the fiber grating 11 is 0.16mm, the grating period is 0.529 μm, the core refractive index is 1.4681, the cladding refractive index is 1.4628, and the maximum refractive index difference is 0.0053.
In the scheme, the fork-shaped interference pattern is different from a common interference pattern, and is characterized in that the interference pattern is in a fork-shaped structure due to the introduction of the orbital angular momentum light beam, so that the orbital angular momentum is combined with optical sensing, the change of the fork-shaped interference pattern is detected in real time by the CCD camera 6, and the change information at the bifurcation point of the interference pattern is extracted, so that the wavelength demodulation method which is the change information of detecting the resonance wavelength by using a spectrometer in the traditional method is effectively replaced, and a new signal demodulation method is realized. The CCD camera model is Digital CamIR1550, and the maximum resolution is 1296 multiplied by 964.
In the above scheme, the laser 3 is a distributed feedback laser with a line width of 100kHz, and the center wavelength thereof is 1550 nm. The coupler 4 is a 2 x 2 single-mode optical fiber coupler, the splitting ratio of the coupler is 1:1, and the working wavelength is 1550 nm. The optical fiber used in the reference optical path 2 is a single mode optical fiber, and the core diameter is 9 μm. The first collimator 12 and the second collimator 21 change the transmitted light in the optical fiber into parallel light with a divergence angle not exceeding 2 °. The spiral phase plate 13 converts the input parallel light beam into orbital angular momentum light beam and outputs the light beam, and the working wavelength is 1550 nm. The mirror 14 changes the propagation direction of the light, and the reflectivity of the mirror is higher than 85%. The light splitting plate 5 is an NPCH-20-15500 type light splitting plate, and the inverse transmission ratio is 1: 1.
Fig. 1 is a schematic diagram of a fiber grating sensing demodulation system and a demodulation method based on a fork interference pattern. The light beam emitted by the laser 3 is divided into two independent beams by the coupler 4, wherein one beam is optically coupled into the measuring optical path 1 with the fiber grating 11, and is emitted into a parallel beam by the first collimator 12, and the parallel beam is incident into the spiral phase plate 13 to generate a beam with orbital angular momentum; the other light beam is coupled into the reference light path 2 with the single-mode fiber to generate a Gaussian light beam, and the two light beams interfere at the light splitting plate 5 to generate a fork-shaped interference pattern. In order to make the measurement result more reasonable, the fiber grating 11 part and the single-mode fiber part in the reference optical path in the measurement optical path need to be placed in the environment to be measured at the same time, so that the delay of the two paths of light is only affected by the characteristics of the fiber grating 11 and is not related to the characteristics of the fiber. When the external to-be-measured changes, the propagation of the light beam in the fiber grating 11 can delay the phase of the light beam, so that a phase difference is generated between the light beams respectively passing through the reference light path 2 and the measurement light path 1, and the fork-shaped interference pattern moves, the CCD camera 6 detects the change of the fork-shaped interference pattern in real time, and finally, the data collected by the CCD camera 6 is stored by the computer 7, so as to obtain the corresponding relationship between the external to-be-measured and the fork-shaped interference pattern, thereby realizing the demodulation of the sensing signal.
Fig. 2 shows interference patterns of the reference beam path 2 and the measurement beam path 1 at different phase differences. As can be seen from fig. 2(a) to (c), as the phase difference increases, the bifurcation point of the interference pattern moves rightward, and the amplitudes at both sides of the bifurcation point change. In order to accurately extract information to be measured contained in the interference pattern, the scheme adopts an image processing technology to extract amplitude information on two sides of a bifurcation point of the interference pattern, uses an imread function in a matlab toolbox to read the information of the interference pattern, and performs image enhancement, filtering and other processing on the interference pattern to reduce image processing errors. With the branching point of fig. 2(a) as a reference (at this time, the phase difference between the measurement optical path 1 and the reference optical path 2 is 0), data on both sides at the branching point is extracted, and an amplitude curve of the data on both sides is plotted by matlab. In order to ensure that the extracted interference image information is clear and accurate, different rows of information on two sides of the bifurcation point are repeatedly extracted, and the change rule of the amplitude information on two sides of the extracted bifurcation point is obtained through comparison and analysis when the left row and the right row of information on the bifurcation point return to 40 rows respectively, so that the method is easy to process and has a good result, and the analysis result is shown in fig. 3. As can be seen from fig. 3, the change of the amplitude values at two sides of the bifurcation point of the interference pattern has a certain symmetry, and the amplitude value gradually increases from bottom to top along with the increase of the phase difference in the graph. In order to reduce the measurement error, when the phase difference between the reference optical path 2 and the measurement optical path 1 is constant, the average value of the amplitudes in the region is selected as an amplitude value, and the relationship between the phase difference and the amplitude value between the reference optical path 2 and the measurement optical path 1 is determined.
Fig. 4(a) shows the amplitude variation of the fork interference pattern at different phase differences between the reference optical path 2 and the measurement optical path 1, where two curves respectively show the amplitude variation at two sides of the bifurcation point of the fork interference pattern. In order to calculate the relationship between the phase difference and the amplitude value between the reference optical path 2 and the measurement optical path 1, the present solution makes a difference between the amplitude values on the left and right sides of the bifurcation point, as shown in fig. 4 (b). As shown in fig. 4(b), the phase difference and amplitude between the reference optical path 2 and the measurement optical path 1 are approximately linear, and the linearity reaches 0.9988. According to the analysis, the fiber grating sensing demodulation method based on the fork-shaped interference pattern changes the signal demodulation structure of the traditional fiber grating, solves the problem that the resolution of a spectrometer is limited in the traditional measurement process, and has practical engineering application value.
Due to the adoption of the technical scheme, the fiber grating sensing demodulation system and the demodulation method based on the fork-shaped interference pattern can realize the measurement to be measured from the outside, and the demodulation of the fiber grating sensing signal realized by the scheme has the advantages of smaller volume and lower cost than that of the traditional wavelength demodulation method, and is more suitable for practical engineering application; by utilizing the optical delay characteristic of the fiber bragg grating, when the external to-be-measured changes, the light can be caused to propagate in the fiber bragg grating to generate different phase delays, so that the interference effect between the reference light path and the measuring light path is further enhanced, and the scheme can be used for various fiber bragg grating devices with small volume and high sensitivity; the performance of a measuring system is improved by introducing orbital angular momentum beams and adjusting a light source, a signal receiving device and the like, and the problem that the measurement precision and the application range are limited due to the limited resolving power of a traditional wavelength demodulation spectrometer is solved; in the using process, only the stability of the whole device is required to be ensured, and compared with other methods, a special process is not required, so that the process exploration difficulty is reduced.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (1)
1. A fiber grating sensing demodulation method based on a fork-shaped interference pattern is characterized in that: the fiber grating sensing demodulation system based on the fork-shaped interference pattern comprises:
a laser for generating a light beam;
the coupler is used for splitting the incident light beam, and the light beam emitted by the laser enters the coupler;
the measuring optical path is used for converting the incident light beam into a light beam with orbital angular momentum;
the reference light path is used for converting the incident light beam into a Gaussian light beam, and the light beam split by the coupler is respectively incident into the reference light path and the measuring light path;
the beam splitter is used for generating a fork-shaped interference beam, and the beams in the reference light path and the measurement light path are incident into the beam splitter to generate interference;
the CCD camera is used for detecting and recording the fork-shaped interference light beams into fork-shaped interference pattern signals in real time, and the CCD camera receives the fork-shaped interference light beams emitted by the light splitting plate;
the measuring light path sequentially comprises a fiber grating, a first collimator, a spiral phase plate and a reflector;
the reference optical path comprises a second collimator;
further comprising the steps of:
s1: the laser generates a light beam to be emitted into the coupler;
s2: the light beams split by the coupler are respectively emitted into a measuring light path and a reference light path;
s3: the light beam is converted into a light beam with orbital angular momentum through the measuring light path, the light beam is converted into a Gaussian light beam through the reference light path, and the light beam with orbital angular momentum and the Gaussian light beam are respectively emitted into the light splitting plate to generate interference to form a fork-shaped interference light beam;
s4: the CCD camera converts the fork-shaped interference light beam emitted by the light splitting plate into a fork-shaped interference pattern signal;
s5: the external to-be-measured changes, the propagation of the light beam in the fiber bragg grating generates phase delay, so that the phase difference between the light beam with orbital angular momentum emitted by the measuring light path and the Gaussian light beam emitted by the reference light path changes, the fork-shaped interference pattern moves at the bifurcation point, and the signals of the fork-shaped interference pattern are continuously detected in real time by the CCD camera and output to the computer;
s6: recording a fork-shaped interference pattern signal by a computer to obtain a corresponding relation between an external object to be measured and the fork-shaped interference pattern;
the length of the fiber grating is 0.16mm, the grating period is 0.529 mu m, the core refractive index is 1.4681, the cladding refractive index is 1.4628, and the maximum refractive index difference is 0.0053;
the laser is a distributed feedback laser, the coupler is a single-mode fiber coupler, light beams in the reference light path are conducted through a single-mode fiber, the first collimator and the second collimator convert incident light beams into parallel light, the spiral phase plate converts the input parallel light beams into orbital angular momentum light beams and outputs the orbital angular momentum light beams, and the reflector changes the propagation direction of the light beams and emits the orbital angular momentum light beams output by the reflector to the light splitting plate;
the center wavelength of the laser is 1550nm, and the coupler is a 2 multiplied by 2 single-mode optical fiber coupler with a light splitting ratio of 1:1 and a working wavelength of 1550 nm;
the core diameter of the single-mode optical fiber in the reference light path is 9 micrometers;
the first collimator and the second collimator convert the transmission light beam in the optical fiber into parallel light with a divergence angle not more than 2 degrees;
the working wavelength of the spiral phase plate for converting the input parallel light beams into orbital angular momentum light beams and outputting the orbital angular momentum light beams is 1550 nm;
the reflectivity of the mirror for changing the propagation direction of the light is higher than 85%;
the inverse transmission ratio of the light splitting plate is 1: 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710149972.0A CN106802160B (en) | 2017-03-14 | 2017-03-14 | Fiber grating sensing demodulation system and method based on fork-shaped interference pattern |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710149972.0A CN106802160B (en) | 2017-03-14 | 2017-03-14 | Fiber grating sensing demodulation system and method based on fork-shaped interference pattern |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN106802160A CN106802160A (en) | 2017-06-06 |
| CN106802160B true CN106802160B (en) | 2020-03-13 |
Family
ID=58987914
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710149972.0A Expired - Fee Related CN106802160B (en) | 2017-03-14 | 2017-03-14 | Fiber grating sensing demodulation system and method based on fork-shaped interference pattern |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN106802160B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107707300B (en) * | 2017-09-26 | 2020-07-07 | 南京邮电大学 | RVP modulation-based method for inhibiting crosstalk of non-aligned OAM multiplexing system |
| CN108645431B (en) * | 2018-05-30 | 2020-08-07 | 西安工业大学 | Fitting peak searching method for cavity length correlation demodulation of optical fiber Fabry-Perot sensor |
| CN108827344B (en) * | 2018-07-20 | 2022-06-03 | 任元 | Gyro effect verification device of wave particle vortex gyro |
| CN111238634B (en) * | 2020-02-17 | 2020-12-15 | 北京理工大学 | Light beam orbital angular momentum spectrum analysis method and device based on interference |
| WO2023070855A1 (en) * | 2021-10-25 | 2023-05-04 | 深圳大学 | Orbital angular momentum mode sensing demodulation method and orbital angular momentum mode sensing system |
| CN114140383B (en) * | 2021-10-25 | 2023-04-11 | 深圳大学 | Sensing demodulation method for orbital angular momentum mode |
| CN114964328B (en) * | 2022-05-10 | 2023-12-05 | 南京师范大学 | All-fiber angular momentum interferometry sensing measurement system and method based on spiral grating |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1596246A1 (en) * | 2004-05-13 | 2005-11-16 | Fujitsu Limited | Modulator for an optical transmitter, push-pull driven modulator, and an asymmetric modulator |
| CN101334315A (en) * | 2008-06-25 | 2008-12-31 | 北京理工大学 | Method and device for measuring light beam orbit angular momentum spectrum |
| CN102148067A (en) * | 2011-01-27 | 2011-08-10 | 西北工业大学 | Device for generating rotary combined vortex light beam |
| CN103792605A (en) * | 2013-12-11 | 2014-05-14 | 南京大学 | Forked liquid crystal grating preparation method and application of forked liquid crystal grating in vortex beam |
| CN204479017U (en) * | 2015-03-13 | 2015-07-15 | 浙江师范大学 | Spiral phase shift interference instrument apparatus |
| CN104833314A (en) * | 2015-06-03 | 2015-08-12 | 中国科学技术大学 | High-resolution optical fiber strain sensor and measuring method |
-
2017
- 2017-03-14 CN CN201710149972.0A patent/CN106802160B/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1596246A1 (en) * | 2004-05-13 | 2005-11-16 | Fujitsu Limited | Modulator for an optical transmitter, push-pull driven modulator, and an asymmetric modulator |
| CN101334315A (en) * | 2008-06-25 | 2008-12-31 | 北京理工大学 | Method and device for measuring light beam orbit angular momentum spectrum |
| CN102148067A (en) * | 2011-01-27 | 2011-08-10 | 西北工业大学 | Device for generating rotary combined vortex light beam |
| CN103792605A (en) * | 2013-12-11 | 2014-05-14 | 南京大学 | Forked liquid crystal grating preparation method and application of forked liquid crystal grating in vortex beam |
| CN204479017U (en) * | 2015-03-13 | 2015-07-15 | 浙江师范大学 | Spiral phase shift interference instrument apparatus |
| CN104833314A (en) * | 2015-06-03 | 2015-08-12 | 中国科学技术大学 | High-resolution optical fiber strain sensor and measuring method |
Non-Patent Citations (2)
| Title |
|---|
| 基于螺旋相位板的涡旋光束的产生与干涉;郭苗军等;《激光与光电子学进展》;20160930(第9期);摘要、正文2.2、3.1、3.3部分及图3、图5 * |
| 用四台阶相位板产生涡旋光束;施建珍等;《物理学报》;20150930;第64卷(第18期);正文第1842021-1842028页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN106802160A (en) | 2017-06-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106802160B (en) | Fiber grating sensing demodulation system and method based on fork-shaped interference pattern | |
| Wang et al. | Distributed OTDR-interferometric sensing network with identical ultra-weak fiber Bragg gratings | |
| CN1333230C (en) | Laser feedback nano displaycement measuring device | |
| CN106989811B (en) | Demodulation device and method for fiber grating hydrophone | |
| CN101634571B (en) | Optical pulse raster distributed fiber sensing device | |
| CN101650509B (en) | Bragg grating high-speed demodulating system based on cascade-connection long period fiber grating | |
| CN101021563A (en) | Double-refraction external cavity displacement measuring system | |
| CN113108710B (en) | Optical low-frequency strain detection system and detection method based on ellipse fitting | |
| CN105973450A (en) | Optical fiber Fizeau interferometric array distributed vibration sensing system and method | |
| CN105444793A (en) | Fiber Bragg raster sensing device based on high-speed pulse laser | |
| CN112444194A (en) | Fabry-Perot grating interferometer for two-degree-of-freedom displacement measurement, measurement method thereof and six-degree-of-freedom interferometer | |
| CN109141491A (en) | Pressure-type optical fiber is slightly variable sensor | |
| Sun et al. | Simultaneous vector bending and temperature sensing based on eccentric multi-mode fiber Bragg gratings | |
| CN100485324C (en) | All-optical fiber type optical fiber grating multi-parameter sensing system | |
| CN100593686C (en) | Optical interference measuring device and its method | |
| CN202648677U (en) | Reflecting interference type optical fiber sensor system | |
| Masoudi et al. | 10-cm spatial resolution distributed acoustic sensor based on an ultra low-loss enhanced backscattering fiber | |
| Chen et al. | Code counting of optical fringes: methodology and realization | |
| CN101825435A (en) | All-fiber-optic displacement measuring method and device thereof | |
| Zhao et al. | Interrogation technique using a novel spectra bandwidth measurement method with a blazed FBG and a fiber-optic array for an FBG displacement sensor | |
| CN100363714C (en) | Optical fiber sensor based on laser feedback | |
| JP2014235154A (en) | Optical axis adjustment device and process therefor | |
| CN102385216A (en) | Fiber Bragg grating (FBG) demodulation method based on modular interference of polarization maintaining fiber (PMF) | |
| Pullteap et al. | Modified fringe-counting technique applied to a dual-cavity fiber Fabry-Pérot vibrometer | |
| CN102735181B (en) | Laser self-mixing interference effect based fiber bragg grating signal demodulating system and method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20200313 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |