CN114111750A - Method for expanding measurement range of white light interference system - Google Patents

Method for expanding measurement range of white light interference system Download PDF

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CN114111750A
CN114111750A CN202111344586.XA CN202111344586A CN114111750A CN 114111750 A CN114111750 A CN 114111750A CN 202111344586 A CN202111344586 A CN 202111344586A CN 114111750 A CN114111750 A CN 114111750A
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optical fiber
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张红霞
李天玥
温国强
贾大功
刘铁根
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Tianjin University
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01CMEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C19/00Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
    • G01C19/58Turn-sensitive devices without moving masses
    • G01C19/64Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
    • G01C19/72Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00Measuring instruments characterised by the use of optical techniques
    • G01B9/02Interferometers
    • G01B9/0209Low-coherence interferometers
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01CMEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C25/00Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01CMEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C25/00Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass
    • G01C25/005Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass initial alignment, calibration or starting-up of inertial devices

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Abstract

The invention discloses a method for expanding the measurement range of a white light interference system, which comprises the following steps of 1, constructing a polarization maintaining optical fiber interference measurement system; step 2, estimating the length of the optical fiber (2) to be measured, and further determining the step progression m of the electric control delay line (6); step 3, determining the length of each stage of scanning optical fiber of the delay line; step 4, calibrating each stage of scanning optical fiber (14) in a calibration mode, and measuring the access allowance x of the scanning optical fiber stage by stagem(ii) a And 5, measuring the optical fiber (2) to be measured in the measurement mode, splicing to obtain optical fiber distributed coupling data, and obtaining the specific length of the optical fiber to be measured. Compared with the prior art, the method can realize the distributed measurement of the ultra-long-distance polarization maintaining optical fiber, and provides a basis for the calibration and the distributed detection of the high-precision optical fiber gyroscope.

Description

Method for expanding measurement range of white light interference system
Technical Field
The invention relates to the field of optical measurement, in particular to a device and a method for expanding the measurement range of a white light interference system.
Background
The polarization maintaining fiber ensures that the polarization state of the linear polarization light incident along the main shaft is not changed in the transmission process. The optical fiber gyroscope has wide application in optical fiber gyroscopes, hydrophones and sensing devices. With the continuous improvement of the requirements of the precision and the measuring distance of the fiber-optic gyroscope and the stress temperature sensing, the requirements on the detection range of the polarization-maintaining fiber are also increased.
White light interferometry is a low coherence interferometry technology and has the advantages of wide measurement range, insensitivity to external crosstalk, high resolution and the like. An interference main peak is generated at the position where the optical path difference of the two interference arms is zero, and the method can be used for measurement positioning calibration.
The optical delay line is used in the fields of optical sensing, measurement, communication and the like. The all-fiber optical delay line has the characteristics of high stability, small influence of external environment, easy integration and the like. In the prior art, a waveguide or a geometric structure is adopted to generate the optical delay.
Chinese patent CN109341520A discloses a device and method for measuring arm length difference of an optical fiber interferometer based on white light interference, which utilizes a 2 × 2 coupler to arrange two arms of the optical fiber interferometer, wherein one arm is provided with a compensating optical fiber and an optical fiber stretcher for adjusting the difference between the two arms of the optical fiber, thereby realizing white light interference measurement. Chinese patent CN106323195A discloses a scanning system suitable for a large-stroke high-precision white light interferometer, which realizes the beam splitting of two arms of the interferometer through a beam splitter prism, adopts a high-performance stepping motor as a driver and a high-precision grating scale as position feedback, and meets the requirement that the white light interferometer carries out large-stroke scanning movement.
Disclosure of Invention
The invention aims to provide a method for expanding the measurement range of a white light interference system, which realizes the ultra-long-distance polarization maintaining optical fiber measurement and provides a basis for the performance evaluation of long-distance polarization maintaining optical fibers.
The invention is realized by adopting the following technical scheme:
a method of extending the measurement range of a white light interferometry system, the method comprising the steps of:
step 1, building a polarization maintaining optical fiber interferometry system, which comprises a light source module 1, an optical fiber to be measured 2, a 45-degree fusion box 3, an analyzer 4, a first 3dB coupler 5, an electric control delay line 6, a first 1 multiplied by 2 optical switch 71, a second 1 multiplied by 2 optical switch 72, a second 3dB coupler 8, a first 1 multiplied by N optical switch 91, a second 1 multiplied by N optical switch 92, a first Faraday rotator 101, a second Faraday rotator 102, a photoelectric detector 11, a data acquisition card 12 and a computer 13;
step 2, estimating the length of the optical fiber 2 to be measured, and further determining the step number m of the electric control delay line 6, wherein the method specifically comprises the following steps:
obtaining the length estimation value of the optical fiber 2 to be measured through rough measurement
Figure BDA0003353509690000021
Calculating the step series of the electrically controlled delay line 6 as
Figure BDA0003353509690000022
Figure BDA0003353509690000023
m is a natural number from 1 to N, and Delta L represents the length of the optical fiber segment to be tested which can be scanned by the electric control delay line 6;
step 3, determining the length of each level of scanning optical fiber on the electric control delay line, and specifically comprising the following steps:
the access length of the first-stage scanning optical fiber 14 is matched with the length of the fixed arm, and then the optical path length delta L of one optical fiber ring is increased for each stage of scanning optical fiber compared with the previous-stage scanning optical fiber;
step 4, calibrating each stage of scanning optical fiber 14 in the calibration mode, and measuring the scanning optical fiber access allowance x step by stepmSpecifically, the following processes are included;
in an upper side light path of the fixed arm, a section of optical fiber fused with two ends on the upper side of the second 3dB coupler 8 forms an optical fiber ring, incident light is split by the second 3dB coupler 8, a part of light is circularly transmitted in the optical fiber ring, and optical delay with fixed length is generated in each circulation;
in the optical path of the scanning arm, the scanning optical fiber 14 is connected between the first 1 xn optical switch 91 and the second 1 xn optical switch 92, and the scanning range is expanded by the first 1 xn optical switch 91 and the second 1 xn optical switch 92;
the electric control delay line 6 realizes scanning of each stageLinear scanning of the optical fiber; step scanning is carried out on multiple sections of scanning optical fibers with fixed length difference, which are connected between the first 1 xN optical switch 91 and the second 1 xN optical switch 92, for N times, the first 1 xN optical switch 91 and the second 1 xN optical switch 92 are adjusted at the same time, and previous m-level multiple optical fibers are scanned step by step from a gear 1 to m to obtain m-level data; scanning through the electric control delay line 6, wherein each level of scanning optical fiber generates two peaks which respectively correspond to a point with equal optical path of the fixed arm and the scanning arm and a point with exactly one optical path delay difference of the optical fiber ring, and the distance between the two peaks is the actual measurement length; the positions of the two peaks are used as interference main maximum mark points generated by two scans on each section of optical fiber to be detected; the difference between the scanning data of each stage and the distance between two peaks is the scanning optical fiber access allowance xm
A connecting coupling interference peak is generated at the connecting point of the tail end of the optical fiber 2 to be tested and the system, whether the peak appears in the m-level step scanning process or not is verified in the step-by-step scanning process, and if the peak appears, the step 5 is carried out; otherwise, adjusting the step number of the electric control delay line, and returning to the step 4 for recalibration;
step 5, measuring the optical fiber 2 to be measured in the measurement mode, splicing to obtain optical fiber distributed coupling data, and obtaining the specific length of the optical fiber to be measured, wherein the method specifically comprises the following steps:
in the lower path of the fixed arm, a polarization-maintaining optical fiber 15 is connected between the first 1 × 2 optical switch 71 and the first 1 × 2 optical switch 72; step scanning is carried out on m times of multi-section scanning optical fibers with fixed length difference accessed between the first 1 xN optical switch 91 and the second 1 xN optical switch 92, the first 1 xN optical switch 91 and the second 1 xN optical switch 92 are adjusted at the same time, and m-stage multi-path optical fibers are scanned step by step from a gear 1 to m to obtain m-section data;
according to the access allowance x calibrated by each stage of scanning optical fibermAnd marking point positions, splicing the data of two adjacent stages to realize the expansion of the optical fiber delay amount and obtain the integral distributed scanning data of the optical fiber 2 to be detected; in actual measurement, a connection coupling interference peak is generated at the position of the connection system at the tail end of the optical fiber 2 to be measured, and the length of the whole optical fiber is further analyzed through the position of the peak.
Compared with the prior art, the invention can realize the distributed measurement of the ultra-long distance polarization maintaining optical fiber and provides a basis for the calibration and detection of the high-precision optical fiber gyroscope.
Drawings
FIG. 1 is a flowchart illustrating the overall method of expanding the measurement range of a white light interferometry system according to the present invention;
FIG. 2 is a schematic diagram of a polarization maintaining fiber interferometry system;
FIG. 3 is a measurement range spliced by the principal maxima generated by scanning each segment of the optical fiber to be measured in the calibration mode;
FIG. 4 is a measurement range spliced according to the main maximum positions calibrated in the calibration mode in the measurement mode.
Reference numerals: 1. the device comprises a light source module, 2, an optical fiber to be tested, 3, 45-degree fusion boxes, 4, a polarization analyzer, 5, a first 3dB coupler, 6, an electric control delay line, 71, a first 1 multiplied by 2 optical switch, 72, a first 1 multiplied by 2 optical switch, 8, a second 3dB coupler, 91, a first 1 multiplied by N optical switch, 92, a second 1 multiplied by N optical switch, 101, a first Faraday rotator mirror, 102, a second Faraday rotator mirror, 11, a photoelectric detector, 12, a data acquisition card, 13, a computer, 14, a scanning optical fiber, 15 and a polarization maintaining optical fiber.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a flowchart illustrating the overall method of expanding the measurement range of a white light interferometry system according to the present invention.
Step 1, building a polarization maintaining optical fiber interferometry system shown in FIG. 2, which comprises a light source module 1, an optical fiber to be measured 2, a 45-degree fusion box 3, an analyzer 4, a first 3dB coupler 5, an electric control delay line 6, a 1 multiplied by 2 optical switch, a second 3dB coupler 8, a 1 multiplied by N optical switch, a Faraday rotator mirror, a photoelectric detector 11, a data acquisition card 12 and a computer 13.
The light source module 1 is an ultra-wideband light source, integrates a polarization module, emits light in linearly polarized light, is welded with the analyzer 4 at an angle of 45 degrees, and is packaged in the 45-degree welding box 3;
incident light is transmitted in the optical fiber 2 to be measured, and an optical path difference exists between an excitation mode and a coupling mode due to disturbance. The excitation mode and the coupling mode are incident to the optical fiber Michelson interference structure, the first 3dB coupler 5 divides the incident light into two paths, and one path of the incident light is led to the first 1 multiplied by 2 optical switch 71, the second 3dB coupler 8, the second 1 multiplied by 2 optical switch 72 and the first Faraday rotary mirror 101 to form a fixed arm; the other path leads to an electric control delay line 6, a first 1 XN optical switch 91, a second 1 XN optical switch 92 and a second Faraday rotation mirror 102 to form a scanning arm; incident light is respectively rotated by 90 degrees through the first Faraday rotating mirror 101 and the second Faraday rotating mirror 102 and then reflected back to two paths, the excitation mode and the coupling mode are interfered with each other at the emergent end of the first 3dB coupler 5, interference signals are received by the photoelectric detector 11 and are collected to the computer 13 through the data acquisition card 12 for analysis. In the lower side light path of the fixed arm, a section of polarization maintaining optical fiber 15 is connected between the two 1 × 2 optical switches, and the length of the polarization maintaining optical fiber is equal to the sum of the lengths of the two ends of the lower side of the second 3dB coupler 8. The polarization maintaining fiber interferometry system has two working modes, namely a calibration mode and a measurement mode.
Step 2, estimating the length of the optical fiber 2 to be measured, and further determining that the step number of the electric control delay line 6 is 10, wherein the method specifically comprises the following steps:
in the upper side light path of the fixed arm, a section of optical fiber fused with two ends on the upper side of the second 3dB coupler 8 forms an optical fiber ring, the length is delta X, after the incident light is split by the second 3dB coupler 8, a part of light is circularly transmitted in the optical fiber ring, and the light delay with the fixed length is generated in each circulation, and the value of the light delay is the product n.delta X of the refractive index of the optical fiber and the length of the optical fiber ring. This delay amount is slightly longer than the single-pass scan range 1700ps of the electrically controlled delay line 6.
And obtaining an estimated value of the length of the optical fiber to be measured by rough measurement, namely 9.5km, and calculating the step stage number of the electric control delay line 6 to be 10.
Step 3, determining the length of each scanning optical fiber on the electric control delay line 6, which specifically comprises the following steps:
the access length of the first stage scanning optical fiber 14 is matched with the length of the fixed arm, and then each stage of scanning optical fiber is added with the optical path length delta L of an optical fiber ring compared with the previous stage of scanning optical fiber. In practical cases, the optical path length of each introductionWith a certain error xmI.e. the first scanning fiber access length is L1The second-stage scanning optical fiber access length is L2=L1+ΔL-x2. By analogy, the m-th scanning optical fiber access length is
Figure BDA0003353509690000051
The specific length of the scanning optical fiber is 2.11m, 2.44m, 2.79m, 3.12m, 3.47m, 3.81m, 4.14m, 4.49m, 4.82m and 5.17m respectively.
Step 4, calibrating each stage of scanning optical fiber 14 in the calibration mode, and measuring the scanning optical fiber access allowance x step by stepmSpecifically, the following processes are included;
in an upper side light path of the fixed arm, a section of optical fiber fused with two ends on the upper side of the second 3dB coupler 8 forms an optical fiber ring, incident light is split by the second 3dB coupler 8, a part of light is circularly transmitted in the optical fiber ring, and optical delay with fixed length is generated in each circulation;
in the light path of the scanning arm, a scanning optical fiber 14 is connected between the 1 XN optical switches, and the scanning range is expanded by using the 1 XN optical switches; for example, embodiments of the present invention select a 1 × 10 optical switch:
the electric control delay line 6 realizes linear scanning of each stage of scanning optical fiber; step scanning is carried out for 10 times on a multi-section scanning optical fiber with fixed length difference accessed between a first 1 x 10 optical switch and a second 1 x 10 optical switch, the optical switch comprises N gears from 1 to N, and the first 1 x N optical switch 91 and the second 1 x N optical switch 92 are adjusted simultaneously to enable the gears of the two optical switches to be consistent, and 10 sections of data are obtained step by step from the gears from 1 to 10; scanning through the electric control delay line 6, wherein each level of scanning optical fiber generates two peaks which respectively correspond to a point with equal optical path of the fixed arm and the scanning arm and a point with exactly one optical path delay difference of the optical fiber ring, and the distance between the two peaks is the actual measurement length; the two peak positions are used as interference main maximum marking points generated by two scans on each section of optical fiber to be detected; the difference between the scanning data of each stage and the distance between two peaks is the scanning optical fiber access allowance xm
Step 5, measuring the optical fiber 2 to be measured in the measurement mode, splicing to obtain optical fiber distributed coupling data, and specifically comprising the following steps:
in the lower path of the fixed arm, a 1X 2 optical switch is switched to be connected with a polarization maintaining optical fiber 15; step scanning is carried out for 10 times on the multi-section scanning optical fiber with fixed length difference connected between the first 1 × 10 optical switch and the second 1 × 10 optical switch, and the first 1 × N optical switch 91 and the second 1 × N optical switch 92 are adjusted at the same time, so that the two optical switches are consistent in gear, and 10 sections of data are obtained step by step from the gear 1 to the gear 10.
According to step 4, the access allowance x of each stage of scanning optical fiber calibrationiAnd marking point positions, splicing the data of two adjacent stages to realize the expansion of the optical fiber delay amount and obtain the integral distributed scanning data of the optical fiber 2 to be detected; in actual measurement, each section of data does not contain an interference main maximum peak, a connection coupling interference peak is generated only at the position of the tail end connecting system of the optical fiber 2 to be measured, and the length of the whole optical fiber is analyzed through the position of the peak.
The total compensating optical path difference of the system is 5.1m, and the birefringence coefficient is 5.35 multiplied by 10-4The optical fiber of (2) realizes the measurement range expansion of 9.53 km.
The foregoing detailed description is to be construed as illustrative and not restrictive, and changes may be made therein by those skilled in the art without departing from the spirit of the invention and the scope of the appended claims.

Claims (6)

1. A method of extending the measurement range of a white light interferometry system, comprising the steps of:
step 1, building a polarization maintaining optical fiber interferometry system, which comprises a light source module (1), an optical fiber to be measured (2), a 45-degree fusion box (3), a polarization analyzer (4), a first 3dB coupler (5), an electric control delay line (6), a first 1 multiplied by 2 optical switch (71), a second 1 multiplied by 2 optical switch (72), a second 3dB coupler (8), a first 1 multiplied by N optical switch (91), a second 1 multiplied by N optical switch (92), a first Faraday rotator mirror (101), a second Faraday rotator mirror (102), a photoelectric detector (11), a data acquisition card (12) and a computer (13);
step 2, estimating the length of the optical fiber (2) to be measured, and further determining the step progression m of the electric control delay line (6), wherein the step progression m specifically comprises the following steps:
the length estimation value of the optical fiber (2) to be measured is obtained through rough measurement
Figure FDA0003353509680000011
Calculating the step grade number of the electric control delay line (6) as m ═
Figure FDA0003353509680000012
m is a natural number from 1 to N, and delta L represents the length of the optical fiber segment to be measured which can be scanned by the electric control delay line (6);
step 3, determining the length of each level of scanning optical fiber on the electric control delay line, and specifically comprising the following steps:
the access length of the first-stage scanning optical fiber (14) is matched with the length of the fixed arm, and then the optical path length delta L of an optical fiber ring is increased for each stage of scanning optical fiber compared with the previous-stage scanning optical fiber;
step 4, calibrating each stage of scanning optical fiber (14) in a calibration mode, and measuring the access allowance x of the scanning optical fiber stage by stagemSpecifically, the following processes are included;
in an upper side light path of the fixed arm, a section of optical fiber fused with two ends on the upper side of the second 3dB coupler (8) forms an optical fiber ring, incident light is split by the second 3dB coupler (8), and a part of light is circularly transmitted in the optical fiber ring, so that the light delay with the fixed length is generated in each circulation;
in the optical path of the scanning arm, a scanning optical fiber (14) is connected between a first 1 xN optical switch (91) and a second 1 xN optical switch (92), and the scanning range is expanded by the first 1 xN optical switch (91) and the second 1 xN optical switch (92);
the electric control delay line (6) realizes linear scanning of each stage of scanning optical fiber; step scanning is carried out on a multi-section scanning optical fiber with fixed length difference accessed between a first 1 xN optical switch (91) and a second 1 xN optical switch (92) for N times, the first 1 xN optical switch (91) and the second 1 xN optical switch (92) are adjusted at the same time, and m-section data are obtained by scanning m-section multi-path optical fibers from a gear 1 to m step by step; via an electrically controlled delay line(6) Scanning, wherein each stage of scanning optical fiber generates two peaks which respectively correspond to a point with equal optical path of the fixed arm and the scanning arm and a point with exactly one optical path delay difference of the optical fiber ring, and the distance between the two peaks is the actual measurement length; the positions of the two peaks are used as interference main maximum mark points generated by two scans on each section of optical fiber to be detected; the difference between the scanning data of each stage and the distance between two peaks is the scanning optical fiber access allowance xm
A connecting coupling interference peak is generated at the connecting point of the tail end of the optical fiber (2) to be tested and the system, whether the peak appears in the m-level step scanning process is verified in the step-by-step scanning process, and if the peak appears, the step 5 is carried out; otherwise, adjusting the step number of the electric control delay line, and returning to the step 4 for recalibration;
step 5, measuring the optical fiber (2) to be measured in a measuring mode, splicing to obtain optical fiber distributed coupling data, and obtaining the specific length of the optical fiber to be measured, wherein the method specifically comprises the following steps:
in the lower path of the fixed arm, a polarization maintaining optical fiber (15) is connected between a first 1X 2 optical switch (71) and a first 1X 2 optical switch (72); step scanning is carried out on a multi-section scanning optical fiber with fixed length difference accessed between a first 1 xN optical switch (91) and a second 1 xN optical switch (92) for m times, the first 1 xN optical switch (91) and the second 1 xN optical switch (92) are adjusted at the same time, and m-section data are obtained by scanning m-section multi-path optical fibers before from a gear 1 to m step by step;
according to the access allowance x calibrated by each stage of scanning optical fibermAnd marking point positions, splicing the data of two adjacent stages to realize the expansion of the optical fiber delay amount and obtain the integral distributed scanning data of the optical fiber (2) to be detected; in actual measurement, a connection coupling interference peak is generated at the position of the connection system at the tail end of the optical fiber (2) to be measured, and the length of the whole optical fiber is further analyzed through the position of the peak.
2. The method for expanding the measurement range of the white light interferometry system according to claim 1, wherein in the polarization maintaining fiber interferometry system, the optical fiber (2) to be measured and the analyzer (4) are welded together at an angle of 45 ° and packaged in a 45 ° welding box (3); incident light is transmitted in an optical fiber (2) to be detected, an excitation mode and a coupling mode are incident to a Michelson interference structure of the optical fiber, a first 3dB coupler (5) divides the incident light into two paths, and one path leads to a first 1 multiplied by 2 optical switch (71), a second 3dB coupler (8), a second 1 multiplied by 2 optical switch (72) and a first Faraday rotating mirror (101) to form a fixed arm; the other path of the light is led to an electric control delay line (6), a first 1 XN optical switch (91), a second 1 XN optical switch (92) and a second Faraday rotation mirror (102) to form a scanning arm; incident light is respectively rotated by 90 degrees through the first Faraday rotating mirror (101) and the second Faraday rotating mirror (102) and then reflected back to two paths, the excitation mode and the coupling mode are mutually interfered at the emergent end of the first 3dB coupler (5), the interference signal is received by the photoelectric detector (11), and the interference signal is collected to a computer (13) for analysis through a data collection card (12); in the lower side light path of the fixed arm, a polarization maintaining optical fiber (15) is connected between the first 1X 2 optical switch (71) and the second 1X 2 optical switch (72).
3. The method of claim 1, wherein the m-th scanning fiber access length is
Figure FDA0003353509680000031
L1For the first stage of scanning the fibre access length, matched to the length of the polarization maintaining fibre (15), xiThe fiber access margin is scanned for each level.
4. A method of extending the measurement range of a white light interferometry system according to claim 1, wherein the amount of optical delay per scan stage is slightly longer than the scan range of the electrically controlled delay line (6).
5. A method for extending the measurement range of a white light interferometry system according to claim 1, wherein the length of said polarization maintaining fiber (15) is equal to the sum of the lengths of the two ends of the lower side of the second 3dB coupler (8).
6. The method of claim 1, wherein the electrical control is performed to extend the measurement range of the white light interferometry systemThe length delta L of the optical fiber segment to be measured which can be scanned by the delay line (6) is the one-way scanning range S and the birefringence coefficient delta n of the electric control delay linebThe expression is as follows:
ΔL=S/Δnb
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CN103743552A (en) * 2013-12-30 2014-04-23 哈尔滨工程大学 Calibrating device for large-range continuous optical path delay line
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