CN111006708B - Measuring point positioning error compensation method for distributed optical fiber sensor - Google Patents
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Abstract
The invention discloses a measuring point positioning error compensation method of a distributed optical fiber sensor, which is characterized in that characteristic points are arranged on an optical fiber as measuring point positioning references, the optical path compensation quantity of the measuring point is calculated by utilizing the temperature and strain information of all measuring points between a certain measuring point and the reference characteristic points, the optical path compensation quantity of the measuring point is more accurately calculated by utilizing the correlation between a Rayleigh scattering spectrum and an initial value of the certain measuring point, and the physical position of the measuring point on the optical fiber can be accurately positioned under the condition of optical path change.
Description
Technical Field
The invention relates to a signal processing technology of an optical fiber sensor, in particular to a measuring point positioning error compensation method of a distributed optical fiber sensor.
Background
The distributed optical fiber sensor utilizes the optical fiber as a sensitive medium to measure the information of temperature, strain, vibration, sound and the like distributed along the optical fiber laying path, has the advantages of large number of measuring points, intrinsic safety, electromagnetic interference resistance, remote measurement and the like, and has wide application in the fields of test testing, long-term monitoring and the like of the structure.
The distributed optical fiber sensor generally determines the physical position of a measuring point on an optical fiber by using an optical path transmitted in the optical fiber, and when the temperature or strain of the sensing optical fiber changes, the optical path transmitted in the optical fiber changes; if the optical path change of the measuring point is not compensated, the physical position of the measuring point on the optical fiber determined by the optical path can deviate from the real position, and the positioning error of the measuring point is generated.
The optical path change is accumulated along the length of the optical fiber, and as the length of the optical fiber of the distributed optical fiber sensor is increased and the spatial resolution is improved, the influence of measuring point positioning errors caused by the optical path change is more obvious.
Disclosure of Invention
The technical problem solved by the invention is as follows: aiming at the problem of the positioning error of the measuring point of the distributed optical fiber sensor caused by the change of the optical path, the method for compensating the positioning error of the measuring point of the distributed optical fiber sensor is provided, the characteristic points are arranged on the optical fiber as the positioning reference of the measuring point, the optical path compensation quantity of the measuring point is calculated by utilizing the temperature and strain information of all measuring points between a certain measuring point and the reference characteristic points, the optical path compensation quantity of the measuring point is more accurately calculated by utilizing the correlation between the Rayleigh scattering spectrum and the initial value of the certain measuring point, and the physical position of the measuring point on the optical fiber can be accurately positioned under the condition of the change of the optical path.
The technical solution of the invention is as follows:
a distributed optical fiber sensor measuring point positioning error compensation method comprises the following steps:
1) setting M characteristic points with fixed physical positions on the optical fiber, dividing the optical fiber into M-1 sections, and taking the mth characteristic point as a measuring point positioning reference of the mth section of the optical fiber; wherein M belongs to [1, M-1 ];
2) setting a plurality of measuring points in each interval to obtain the optical path compensation quantity of each measuring point, which specifically comprises the following steps:
21) setting N in the mth interval of the optical fibermA measurement point, NmThe value range of (1) is 10-1000;
22) numbering each measuring point in the m intervals in sequence according to the distance between each measuring point and the mth reference characteristic point from small to large; when the required positioning accuracy is larger than 0.2mm, entering the step 23) or 24), and when the required positioning accuracy is smaller than or equal to 0.2mm, entering the step 24);
23) determining the optical path compensation quantity of the nth measuring point in the mth interval by using the temperature values and the strain values of all measuring points between the mth characteristic point and the nth measuring point in the mth interval; n is an element of [2, N ∈m]；
24) Obtaining the cross correlation between the Rayleigh scattering spectrum and the initial state Rayleigh scattering spectrum of the ith measuring point in the mth interval under different optical path offset, and taking the corresponding optical path offset when the cross correlation peak value is maximum as the optical path compensation quantity of the ith measuring point; wherein i ∈ [1, N ∈ ]m]。
Compared with the prior art, the invention has the beneficial effects that:
1) according to the measuring point positioning error compensation method of the distributed optical fiber sensor, the characteristic points are arranged on the sensing optical fiber and used as the reference for measuring point positioning error compensation, and the accumulation of the measuring point positioning error along the length of the optical fiber is favorably reduced.
2) The invention discloses a measuring point positioning error compensation method of a distributed optical fiber sensor, which utilizes the temperature and strain information of all measuring points between a characteristic point and a certain measuring point to calculate and initially compensate the optical path change of the measuring point, and is beneficial to reducing the calculation amount.
3) The invention discloses a measuring point positioning error compensation method of a distributed optical fiber sensor, which utilizes the correlation between a measuring point Rayleigh scattering spectrum and an initial value to carry out fine compensation of the measuring point positioning error and can realize high-precision compensation of the measuring point positioning error.
Drawings
FIG. 1 is a schematic diagram of characteristic points of a distributed optical fiber sensor measuring point positioning error compensation method.
Description of reference numerals:
1-optical fiber, 21-optical fiber starting point, 22-temperature control point, 23-strain control point, 24-reflection signal enhancement point and 25-optical fiber termination point.
Detailed Description
The invention discloses a measuring point positioning error compensation method of a distributed optical fiber sensor, which comprises the following steps:
1) setting M characteristic points with fixed physical positions on the optical fiber 1, dividing the optical fiber 1 into M-1 sections, and taking the mth characteristic point as a measuring point positioning reference of the mth section of the optical fiber; wherein M belongs to [1, M-1 ];
2) setting a plurality of measuring points in each interval to obtain the optical path compensation quantity of each measuring point, which specifically comprises the following steps:
21) n is set in the mth zone of the optical fiber 1mA measurement point, NmThe value range of (1) is 10-1000;
22) numbering each measuring point in the m intervals in sequence according to the distance between each measuring point and the mth reference characteristic point from small to large; when the required positioning accuracy is larger than 0.2mm, entering the step 23) or 24), and when the required positioning accuracy is smaller than or equal to 0.2mm, entering the step 24);
23) using the sum of the m-th feature pointDetermining the optical path compensation quantity of the nth measuring point in the mth interval according to the temperature values and the strain values of all measuring points between the nth measuring point in the mth interval; n is an element of [2, N ∈m]；
24) Obtaining the cross correlation between the Rayleigh scattering spectrum and the initial state Rayleigh scattering spectrum of the ith measuring point in the mth interval under different optical path offset, and taking the corresponding optical path offset when the cross correlation peak value is maximum as the optical path compensation quantity of the ith measuring point; wherein i ∈ [1, N ∈ ]m]。
Step 1) the feature points include: the characteristic points are an optical fiber starting point 21, a temperature control point 22, a strain control point 23, a reflection signal enhancement point 24 and an optical fiber termination point 25;
the temperature control points 22 are position points of a reference temperature sensor arranged on the optical fiber 1 or position points of constant temperature control, and the number of the temperature control points 22 ranges from 1 to 50; the strain control points 23 are positions on the optical fiber 1 where an isolation protection layer is arranged, the isolation protection layer is used for keeping the strain of the optical fiber at the positions unchanged, and the number of the strain control points 23 ranges from 1 to 50; the reflection signal enhancement points 24 are position points of the optical fiber 1, wherein the intensity of the optical signal is greater than 2 times of the average value of the intensity of the optical signal of the measuring point, and the number of the reflection signal enhancement points 24 ranges from 1 to 50.
The method for determining the optical path compensation quantity P of the nth measuring point in the mth interval specifically comprises the following steps:
wherein,. DELTA.lop,pFor the initial path of light propagation in each measuring point, Δ εpIs the strain change quantity of the p measuring point relative to the initial moment, delta TpIs the temperature variation of the p-th measuring point relative to the initial time, kTHas a value range of 5 × 10-6/℃～50×10-6/℃，kεHas a value range of 0.5 × 10-6/με～5×10-6/με；p∈[1，n]。
For the m interval requiring higher positioning accuracyi stations, step 24) after step 22) is completed): obtaining the cross correlation between the Rayleigh scattering spectrum and the initial state Rayleigh scattering spectrum of the ith measuring point in the mth interval under different optical path offset, and taking the corresponding optical path offset when the cross correlation peak value is maximum as the optical path compensation quantity of the ith measuring point; wherein i ∈ [1, N ∈ ]m]。
The method for taking the optical path offset corresponding to the maximum cross-correlation peak value as the optical path compensation quantity of the nth measuring point specifically comprises the following steps:
measuring the Rayleigh scattering spectrum S of the ith measuring point of the mth interval in the initial statei0；
Adding a group of optical path offsets delta into the optical path from the mth reference characteristic point to the ith measuring point1、δ2、δ3…δjMeasuring the Rayleigh scattering spectrum S of the ith measuring point under different optical path offseti1、Si2、Si3…Sij；Si1、Si2、Si3…SijAre respectively reacted with Si0And performing cross-correlation operation, and taking the optical path offset corresponding to the maximum cross-correlation peak value as the optical path compensation quantity of the ith measuring point.
Examples
As shown in fig. 1, M characteristic points with fixed physical positions are arranged on an optical fiber 1, the characteristic points are an optical fiber starting point 21, a temperature control point 22, a strain control point 23, a reflected signal enhancement point 24 and an optical fiber termination point 25, the optical fiber 1 is divided into M-1 sections, and the mth characteristic point (M is 1,2,3 … M-1) is used as a measuring point positioning reference of the mth section of the optical fiber; the temperature or temperature trend of the temperature control point 22 is known, and one specific implementation method is to perform thermostatic control on the temperature control point 22; the strain or strain variation tendency of the strain control point 23 is known, and a specific embodiment is to make the strain control point 23 of the optical fiber 1 in a free state by using an isolation protection structure; one specific example of a reflected signal enhancement point 24 is a fiber grating or fiber end face reflection.
In the m-th interval of the optical fiber 1, N is distributedmEach measuring point is used for dividing N according to the distance between the measuring point and the reference characteristic point from small to largemThe number of each measuring point is 1,2,3 … NmThe initial optical path of light transmitted in each measuring point is Deltalop,n(n＝1,2,3,4…Nm) (ii) a The temperature change delta T of the 1 st measuring point is demodulated1Strain change Deltaε1(ii) a According to the proportionality coefficient k between relative change of optical path and temperature changeTThe ratio coefficient k between the relative change of the optical path and the change of the strainεCalculating the optical path change (k) of the light transmitted in the 1 st measuring pointTΔT1+kεΔε1)Δlop,1And the optical path compensation quantity is used as the optical path compensation quantity of the 2 nd measuring point; the nth measuring point (N is 2,3,4 … N) is calculated in turnm) Amount of optical path compensation
The compensation of the positioning errors of all measuring points is realized; in one embodiment, k isTIs typically about 7 x 10-6/℃，kεIs typically about 0.78 x 10-6/με。
Measuring the Rayleigh scattering spectrum S of the ith measuring point in the initial state for the ith measuring point needing higher positioning precision in the mth intervali0(ii) a Adding a group of optical path offsets delta into the optical path from the mth reference characteristic point to the ith measuring point1、δ2、δ3…δjMeasuring the Rayleigh scattering spectrum S of the ith measuring point under different optical path offseti1、Si2、Si3…Sij；Si1、Si2、Si3…SijAre respectively reacted with Si0And performing cross-correlation operation, and taking the optical path offset corresponding to the maximum cross-correlation peak value as the optical path compensation quantity of the ith measuring point to realize high-precision compensation of the positioning error of the ith measuring point.
Those skilled in the art will appreciate that the details of the invention not described in detail in the specification are within the skill of those skilled in the art.
Claims (4)
1. A distributed optical fiber sensor measuring point positioning error compensation method is characterized by comprising the following steps:
1) m characteristic points with fixed physical positions are arranged on the optical fiber (1), the optical fiber (1) is divided into M-1 sections, and the mth characteristic point is used as a measuring point positioning reference of the mth section of the optical fiber; wherein M belongs to [1, M-1 ];
2) setting a plurality of measuring points in each interval to obtain the optical path compensation quantity of each measuring point, which specifically comprises the following steps:
21) setting N in the mth zone of the optical fiber (1)mA measurement point, NmThe value range of (1) is 10-1000;
22) numbering each measuring point in the m intervals in sequence according to the distance between each measuring point and the mth reference characteristic point from small to large; when the required positioning accuracy is larger than 0.2mm, entering the step 23) or 24), and when the required positioning accuracy is smaller than or equal to 0.2mm, entering the step 24);
23) determining the optical path compensation quantity of the nth measuring point in the mth interval by using the temperature values and the strain values of all measuring points between the mth characteristic point and the nth measuring point in the mth interval; n is an element of [2, N ∈m]；
24) Obtaining the cross correlation between the Rayleigh scattering spectrum and the initial state Rayleigh scattering spectrum of the ith measuring point in the mth interval under different optical path offset, and taking the corresponding optical path offset when the cross correlation peak value is maximum as the optical path compensation quantity of the ith measuring point; wherein i ∈ [1, N ∈ ]m]。
2. The method for compensating the measuring point positioning error of the distributed optical fiber sensor according to claim 1, wherein the characteristic points in step 1) comprise: the device is characterized by comprising an optical fiber starting point (21), a temperature control point (22), a strain control point (23), a reflection signal enhancement point (24) and an optical fiber termination point (25);
the temperature control points (22) are position points of a reference temperature sensor arranged on the optical fiber (1) or position points of constant temperature control, and the number of the temperature control points (22) ranges from 1 to 50; the strain control points (23) are position points on the optical fiber (1) provided with an isolation protection layer, the isolation protection layer is used for keeping the strain of the optical fiber at the position points unchanged, and the number of the strain control points (23) ranges from 1 to 50; the reflection signal enhancement points (24) are position points of which the light signal intensity on the optical fiber (1) is more than 2 times of the average value of the light signal intensity of the measuring points, and the number of the reflection signal enhancement points (24) ranges from 1 to 50.
3. The method for compensating the measurement point positioning error of the distributed optical fiber sensor according to claim 2, wherein the step 23) is a method for determining the optical path compensation amount P of the nth measurement point in the mth interval, which specifically comprises the following steps:
wherein,. DELTA.lop,pFor the initial path of light propagation in each measuring point, Δ εpIs the strain change quantity of the p measuring point relative to the initial moment, delta TpIs the temperature variation of the p-th measuring point relative to the initial time, kTHas a value range of 5 × 10-6/℃～50×10-6/℃，kεHas a value range of 0.5 × 10-6/με～5×10-6/με；p∈[1，n]。
4. The method for compensating the measurement point positioning error of the distributed optical fiber sensor according to claim 2, wherein the method for taking the optical path offset corresponding to the maximum cross-correlation peak value in step 24) as the optical path compensation quantity of the nth measurement point specifically comprises the following steps:
measuring the Rayleigh scattering spectrum S of the ith measuring point of the mth interval in the initial statei0；
Adding a group of optical path offsets delta into the optical path from the mth reference characteristic point to the ith measuring point1、δ2、δ3…δjMeasuring the Rayleigh scattering spectrum S of the ith measuring point under different optical path offseti1、Si2、Si3…Sij；Si1、Si2、Si3…SijAre respectively reacted with Si0And performing cross-correlation operation, and taking the optical path offset corresponding to the maximum cross-correlation peak value as the optical path compensation quantity of the ith measuring point.
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