CN112066887A - Optical fiber length measuring system and measuring method thereof - Google Patents
Optical fiber length measuring system and measuring method thereof Download PDFInfo
- Publication number
- CN112066887A CN112066887A CN202010839533.4A CN202010839533A CN112066887A CN 112066887 A CN112066887 A CN 112066887A CN 202010839533 A CN202010839533 A CN 202010839533A CN 112066887 A CN112066887 A CN 112066887A
- Authority
- CN
- China
- Prior art keywords
- optical
- optical fiber
- light
- path
- optical path
- 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.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
Abstract
The invention relates to the technical field of optical fiber length measurement, in particular to an optical fiber length measurement system and a measurement method thereof. The optical fiber length measuring system comprises a light source, a coupler, a standard optical fiber, an optical path adjusting unit, a first polarizer, a second polarizer, a polarization-maintaining coupler and an optical power meter, wherein a light beam emitted by the light source is split by the coupler to form two beams of light, wherein one beam of light is transmitted to the input end of the polarization-maintaining coupler after sequentially passing through the optical fiber to be measured and the first polarizer to form a coherent light path; the other light beam is transmitted to the input end of the polarization maintaining coupler after sequentially passing through the standard optical fiber, the optical path adjusting unit and the second polarizer to form a reference optical path; after the two light beams are combined by the polarization maintaining coupler, the light beam optical path of the coherent light path is matched with the light beam optical path of the reference light path to generate white light interference; and transmitting the combined light to an optical power meter for optical power monitoring, and acquiring an optical path adjusting distance corresponding to the maximum optical power so as to acquire the length of the optical fiber to be detected. The invention can improve the capability of resisting the transmission noise and polarization state interference of the optical fiber.
Description
Technical Field
The invention relates to the technical field of optical fiber length measurement, in particular to an optical fiber length measurement system and a measurement method thereof.
Background
Optical fiber transmission has the advantages of strong anti-interference capability, low loss, strong transmission reliability and the like, so the optical fiber communication becomes a main transmission means of a modern communication network and is applied to various fields of daily life. Generally, optical fiber testing, optical fiber fusion splicing, refractive index testing, and the like all involve optical fiber length measurement, and it can be said that optical fiber length measurement is an important technical basis for implementing optical fiber communication.
At present, most of optical fiber length measuring instruments are used for measuring the length of optical fibers, for example, optical time domain reflectometer OTDR, optical frequency domain reflectometer OFDR, optical coherence reflectometer OCDR and the like are used for measuring the length of optical fibers, and these measuring methods have many defects of high measuring cost, poor measuring accuracy and the like, so that these measuring methods have certain limitations in practical application, and therefore, a new optical fiber length measuring scheme is urgently needed at present.
The interference type optical fiber sensing system mainly comprises two parts: fiber optic sensors and signal demodulation instruments. The interference type optical fiber sensor includes: Fabry-Perot, Mach-Zehnder, Michelson, Sagnac and the like, when the interferometer is acted on by the to-be-measured object, the interferometer is subjected to phase modulation, and the phase or phase change of the interferometer is demodulated from the output interference signal of the interferometer, so that the measurement of the measured physical quantity is realized. However, the use of a single-point light source in the optical fiber path is very likely to cause noise generation and the polarization state is very likely to be affected, thereby reducing the accuracy of the test signal demodulator.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide an optical fiber length measuring system and a measuring method thereof, aiming at the above-mentioned defects in the prior art, and solving the problems that the existing optical fiber length measuring scheme is easy to generate noise, the polarization state is very easy to be affected, and the measuring accuracy is low.
The technical scheme adopted by the invention for solving the technical problems is as follows: the optical fiber length measuring system comprises a light source, a coupler, a standard optical fiber, an optical path adjusting unit, a first polarizer, a second polarizer, a polarization maintaining coupler and an optical power meter, wherein the light beam emitted by the light source is split by the coupler to form two beams of light,
a light beam sequentially passes through the optical fiber to be detected and the first polarizer and then is transmitted to the input end of the polarization maintaining coupler to form a coherent light path;
the other light beam is transmitted to the input end of the polarization maintaining coupler after sequentially passing through the standard optical fiber, the optical path adjusting unit and the second polarizer to form a reference optical path;
after the two light beams are combined by the polarization maintaining coupler, the light beam optical path of the coherent light path is matched with the light beam optical path of the reference light path to generate white light interference;
and transmitting the combined light to an optical power meter for optical power monitoring, and acquiring an optical path adjusting distance corresponding to the maximum optical power so as to acquire the length of the optical fiber to be detected.
Further preferred embodiments of the present invention are: the optical path adjusting unit comprises a first circulator, a collimator, a reflector and an adjusting mechanism for adjusting the distance between the collimator and the reflector, the first circulator is provided with a first port, a second port and a third port, a light beam output by the standard optical fiber is incident to the first port of the first circulator, the light beam is transmitted into the second port from the first port, is emitted to the collimator and is transmitted to the reflector, and is reflected by the reflector to be output to the second polarizer through the collimator, the second port and the third port in sequence.
Further preferred embodiments of the present invention are: the adjusting mechanism comprises an adjusting guide rail provided with a position cursor, and the reflecting mirror is arranged on the adjusting guide rail in a sliding mode so as to adjust the distance between the reflecting mirror and the collimator.
Further preferred embodiments of the present invention are: the optical fiber length measuring system further comprises a second circulator arranged between the optical fiber to be measured and the first polarizer, and light beams output by the optical fiber to be measured are transmitted to the first polarizer through the second circulator.
Further preferred embodiments of the present invention are: the light source is an ASE light source.
Further preferred embodiments of the present invention are: the light source is an adjustable single-point light source.
The technical scheme adopted by the invention for solving the technical problems is as follows: an optical fiber length measuring method is provided, which is applied to any one of the optical fiber length measuring systems to measure the length of an optical fiber to be measured, and comprises the following steps:
calibrating the optical paths of the coherent light path and the reference light path to ensure that the optical paths of the two light paths are equal;
the optical fiber to be measured is accessed into a coherent optical path, and the standard optical fiber is accessed into a reference optical path;
adjusting the optical path of the reference optical path light beam;
monitoring the optical power of a light beam after the coherent light path and the reference light path are combined;
acquiring an optical path adjusting distance corresponding to the maximum optical power after beam closing;
and the length of the optical fiber to be measured is obtained according to the optical path adjusting distance.
Further preferred embodiments of the present invention are: the method also comprises the following steps before the optical path of the reference optical path beam is adjusted:
synchronously monitoring the optical power of a coherent light path and a reference light path;
and adjusting the welding angles of the coherent light path and the reference light path and the double fiber ends of the polarization-maintaining coupler to enable the energy of the two light beams of the coherent light path and the reference light path to be equal and output after the two light beams are combined.
Further preferred embodiments of the present invention are: the step of obtaining the optical path adjusting distance corresponding to the maximum optical power after beam combination comprises the following steps:
acquiring a first position point corresponding to an optical path adjusting unit when the optical paths of the two optical paths before the optical fiber to be detected is not accessed and the standard optical fiber are equal;
acquiring a second position point corresponding to the optical path adjusting unit when the optical paths of the two optical paths are equal after the optical fiber to be detected and the standard optical fiber are accessed;
and acquiring an optical path adjusting distance corresponding to the maximum optical power after beam closing according to the first position point and the second position point.
The invention has the advantages that compared with the prior art, the light beam emitted by the light source is split into two beams of light by the coupler, the two beams of light are divided into the coherent light path and the reference light path, the light path adjusting unit is adjusted to enable the light paths of the coherent light path and the reference light path to be matched to generate white light interference, the optical power change of the light beam after the two light paths are combined is monitored by the optical power meter, the light path adjusting distance corresponding to the maximum optical power is obtained, the length of the optical fiber to be measured is obtained, the interference white noise is greatly inhibited, the polarized light interference contrast in the same polarization direction is increased, the measurement sensitivity and the measurement precision are effectively improved, and the capacity of resisting the transmission noise and the polarization state interference of the optical.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic structural diagram of a first embodiment of an optical fiber length measuring system according to the present invention;
FIG. 2 is a schematic structural diagram of a second embodiment of the optical fiber length measuring system of the present invention;
FIG. 3 is a schematic structural diagram of a third embodiment of an optical fiber length measuring system according to the present invention;
FIG. 4 is a schematic diagram of the relationship between the working distance adjustment and the coupling efficiency of the optical path adjusting unit and the collimator according to the present invention;
FIG. 5 is a diagram showing the relationship between the optical path length and optical power of the ASE coherent combined beam after polarization in different polarization states;
FIG. 6 is a block flow diagram of a method of measuring the length of an optical fiber according to the present invention;
FIG. 7 is a block diagram of a detailed flow chart of the method of measuring the length of an optical fiber according to the present invention;
FIG. 8 is a block diagram of the process of obtaining an optical path adjustment distance according to the present invention;
FIG. 9 is a white light scanning schematic of the fiber length test of the present invention;
fig. 10 to 13 are schematic diagrams showing the relationship between the optical power and the wavelength of the combined beam under different optical path differences when the adjustable single-point light source is adopted.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
As shown in fig. 1 to 3, the present invention provides a preferred embodiment of an optical fiber length measuring system.
The optical fiber length measuring system is used for measuring the length of the optical fiber 90 to be measured. Referring to fig. 1 to 3, the optical fiber length measuring system includes a light source, a coupler 20, a standard optical fiber 30, an optical path adjusting unit 40, a first polarizer 50, a second polarizer 60, a polarization maintaining coupler 70, and an optical power meter 80, where a light beam emitted by the light source is split by the coupler 20 to form two light beams, where one light beam sequentially passes through an optical fiber 90 to be measured and the first polarizer 50 and then is transmitted to an input end of the polarization maintaining coupler 70 to form a coherent optical path; the other light beam sequentially passes through the standard optical fiber 30, the optical path adjusting unit 40 and the second polarizer 60 and then is transmitted to the input end of the polarization maintaining coupler 70 to form a reference optical path; after the two light beams are combined by the polarization maintaining coupler 70, the light beam optical path of the coherent light path is matched with the light beam optical path of the reference light path to generate white light interference; the combined light is transmitted to the optical power meter 80 for optical power monitoring, and the optical path adjusting distance corresponding to the maximum optical power is obtained, so as to obtain the length of the optical fiber 90 to be measured. The light beam emitted by the light source is split into two beams of light by the coupler 20, the two beams of light are divided into a coherent light path and a reference light path, the light path adjusting unit 40 is adjusted to enable the light path of the coherent light path to be matched with the light path of the reference light path to generate white light interference, the light power of the light beam formed by combining the two light paths is monitored by the optical power meter 80, the light path adjusting distance corresponding to the maximum light power is obtained, the length of the optical fiber 90 to be measured is obtained, interference white noise is greatly suppressed, the polarized light interference contrast in the same polarization direction is increased, the measurement sensitivity is effectively improved, and the optical fiber transmission noise and polarization state interference resistance are improved. Wherein, a reference optical path and a coherent optical path formed by splitting by the coupler 20 constitute a MZI (Mach-Zehnder interferometer) interference optical path, and the polarization is analyzed by the polarization maintaining coupler 70 to reduce the influence of polarization on the MZI output contrast.
In this embodiment, the selection and parameters of each device are as follows: the light source can be an ASE light source 11 or a tunable single-point light source 12. When the ASE light source 11 is adopted, the central wavelength of the ASE light source 11 is 1550nm, and the half-spectrum width is more than 50 nm; the fiber output power is 0.5-2 mW, and the extinction ratio is less than 3 dB; the coupler 20 adopts a single-mode coupler 20, and the working center wavelength of the coupler 20 is 1550 nm; the cut-off wavelength of the optical fiber is less than 1500nm, so that single-mode transmission of the ASE light source 11 in the optical fiber is ensured; the working wavelength of the two polarizers is 1550nm, the extinction ratio is greater than 30dB, the polarized light emergence angle is smaller than 10 degrees, namely the included angle between the linearly polarized light vibration direction and the cat eye direction is smaller than 10 degrees, the input ends of the two polarizers are single-mode fibers, and the output ends of the two polarizers are panda type polarization maintaining fibers; the splitting ratio of the polarization maintaining coupler 70 is 50%, the polarization maintaining coupler 70 is provided with three ports, the three ports are all high slow axis transmission to realize the combination of two polarized light public ends, the central working wavelength of the polarization maintaining coupler 70 is 1550nm, the splitting ratio is 50%, the polarization extinction ratio is 25dB, the extra loss is less than 0.5dB, the three ends are all panda type polarization maintaining optical fibers, and the working modes are all slow axis transmission modes; the probe of the optical power meter 80 adopts a C-band low-power probe, measures the change position of the power value near the zero optical path point, and determines the position of the maximum power value. In the invention, the wavelength working ranges of the single-mode coupler 20, the first polarizer 50, the second polarizer 60, the polarization-maintaining coupler 70 and the optical power meter 80 can cover the emission spectrum of a wide-spectrum light source, the output pigtails of the first polarizer 50 and the second polarizer 60, the input pigtail and the output pigtail of the polarization-maintaining coupler 70 all work in a single-mode state and a polarization maintaining state, and other devices only work in a single-mode state.
The ASE light source 11 is a broadband light source, signals of the broadband light source pass through the first polarizer 50 and the second polarizer 60 corresponding to the reference light path and the coherent light path, and natural light with no polarization characteristic of the ASE light source 11 is polarized into linearly polarized light and transmitted on the slow axis of the polarization maintaining optical fiber, so that the coherent contrast is improved, and the weakening of the coherent contrast caused by anisotropic polarization is reduced. The white light scanning interference ASE light source 11 can effectively avoid single-point noise caused by the optical fiber transmission process, and reduce the influence of environmental interference on the light transmission in the optical fiber light path. The optical fiber length measuring system adopting the ASE light source 11 utilizes the compensation optical path of the white light scanning interference technology, the ASE light source 11 is adopted to effectively reduce the noise amplitude of optical fiber transmission, and the optical fiber length is measured by utilizing a white light interference zero optical path point; the ASE light source 11 interferes with linear polarization to improve interference contrast and measurement accuracy. Fig. 5 shows a corresponding relationship between the optical path length and the optical power of the ASE coherent combined beam after polarization in the ASE light source polarization state.
The optical fiber length measuring system adopts an all-fiber optical path (except for an air gap in the optical path adjusting unit 40), has a stable optical path system, can be integrally transferred, and is flexible in application and convenient to operate.
Referring to fig. 1, the optical path adjusting unit 40 in this embodiment includes a first circulator 41, a collimator 42, a mirror 43, and an adjusting mechanism for adjusting a distance between the collimator 42 and the mirror 43, where the first circulator 41 has a first port, a second port, and a third port, a light beam output from the standard optical fiber 30 enters the first port of the first circulator 41, the light beam enters the second port from the first port, exits to the collimator 42, is transmitted to the mirror 43, and is reflected by the mirror 43 and sequentially output to the second polarizer 60 through the collimator 42, the second port, and the third port. The optical beam is transmitted in one direction in the first circulator 41, that is, the optical beam inputted from the first port is outputted through the second port, and the optical beam inputted from the second port is outputted through the third port. The distance between the reflector 43 and the collimator 42 is adjusted by operating the adjusting mechanism, so that the optical path of the reference light path light beam is adjusted, the optical path of the reference light beam scanned by the reference light path is matched with the optical path of the coherent light beam transmitted by the coherent light path, white light interference is generated, the adjusting optical path range is larger than the optical path difference between the optical fiber 90 to be measured and the standard optical fiber 30 in the adjusting process, and the optical path range is prevented from exceeding the measuring range. In addition, the working distance of the collimator 42, which is equivalent to twice the distance between the movement starting point of the mirror 43 and the lens, can be adjusted by changing the gap between the optical fiber and the lens in the collimator 42, so that the optical path adjusting unit 40 can adjust within a stable scanning range, that is, the optical path does not have obvious loss change when the mirror 43 moves, and the light intensity in the optical path of the moving mirror 43 does not change greatly. In this embodiment, the lens of the collimator 42 is a long-focus lens, the displacement of the reflector 43 of the millimeter-scale collimator 42 has a small influence on the fiber coupling efficiency, and the change of the fiber coupling efficiency along with the displacement of the reflector 43 can be seen in fig. 4, which shows that, as shown in fig. 4, the energy change is only 2% in the 200mm range. The working wavelength of the first circulator 41 in the optical path adjusting unit 40 is 1550nm, the channel isolation is greater than 50dB, the insertion loss is less than 0.5dB, the influence of return light on a light source is effectively avoided, and the forward transmission directivity of the optical path is increased.
Further, the adjusting mechanism comprises an adjusting guide rail 44 provided with a position cursor, and the reflector 43 is slidably arranged on the adjusting guide rail 44 to adjust the distance between the reflector 43 and the collimator 42. The distance between the mirror 43 and the collimator 42 is adjusted by adjusting the position of the mirror 43 on the adjustment guide 44, that is, the mirror 43 is made close to or far from the lens of the collimator 42, to adjust the optical path length of the reference beam on the reference optical path. The adjusting guide rail 44 with the position vernier can adopt a high-precision one-dimensional adjusting shaft, the stroke of the coarse adjusting shaft is 10cm, the precision is 10um, and the adjusting precision of the fine adjusting shaft can reach 0.5 um. In the adjusting process, the first position point before the movement of the reflector 43 and the second position point after the movement can be checked through the position cursor, and the movement distance of the reflector 43, that is, the corresponding optical path adjusting distance, is obtained according to the first position point and the second position point.
In the optical path adjusting unit 40, the adjusting guide 44 with the position cursor and the reflecting mirror 43 form a quantitative optical path scanning arm, and the optical path adjusting unit 40 adopting the reflection coupling of the collimator 42 increases the optical path scanning range by using the long-focus lens and changing the gap between the optical fiber and the lens, thereby reducing the sensitivity of the coupling efficiency varying with the optical path.
In this embodiment, before the optical path is adjusted by using the optical path adjusting unit 40, the optical fiber length measuring system needs to be calibrated. During calibration, the reference optical path is not added with the standard optical fiber 30, the coherent optical path is not added with the optical fiber 90 to be measured, the optical path adjusting unit 40 is adjusted to the optical power fluctuation change center, the position of the maximum optical power value is the zero optical path point, and the optical path difference between the two optical paths is zero. After calibration, the welding angle between the coherent optical path and the reference optical path and the two fiber ends of the polarization maintaining coupler 70 needs to be adjusted, specifically: after calibration, the light power of the coherent light path and the light power of the reference light path are monitored simultaneously, wherein the path with large power (the power difference is defined as P) and one end of the double fibers of the polarization maintaining coupler 70 are added with the cat eye alignment angle, and the angle theta meets the formula 10 log [ cos (theta) ]]2And the combined beam output with the same energy of the two optical paths is ensured as P, and the double-path interference contrast is further improved. The polarization-maintaining coupler 70 has high polarization-dependent loss, the light intensity ratio of the outputs of the first polarizer 50 and the second polarizer 60 can be adjusted through the angle aligned by the cat eye when the polarization-maintaining optical fibers are welded, and the dynamic range and the sensitivity of measurement can be kept consistent by comprehensively coupling the measurement results of light and transmission light under the conditions of energy separation and energy balance through the adjustment, so that the polarization crosstalk can be obtainedAnd the absolute amplitude eliminates the intensity of a light source and the fluctuation of the connection loss between the device and the test system, and further improves the double-path interference contrast.
In the present invention, the optical fiber 90 to be tested can be connected between the output end of the coupler 20 and the input end of the first polarizer 50 through an optical fiber connector (not shown), or the second circulator 110 can be arranged between the optical fiber 90 to be tested and the first polarizer 50 by arranging the second circulator 110, and the optical fiber 90 to be tested is connected between the output end of the coupler 20 and the input end of the first polarizer 50. The light beam output from the fiber under test 90 is transmitted to the first polarizer 50 through the second circulator 110, and the light beam is transmitted in one direction in the second circulator 110. When the optical fiber connector is used for connecting the optical fiber 90 to be tested into the coherent light path, the splitting ratio of the coupler 20 is set to 50%, equal light energy is provided for the coherent light path and the reference light path, and the optimal contrast is provided for the beam combination light power; when the second circulator 110 is used to connect the optical fiber 90 to be measured into the coherent light path, the splitting ratio of the coupler 20 is set to 99:1, that is, the coherent light path transmits 99% light energy, and the reference light path transmits 1% light energy.
Referring to fig. 6, the present invention also provides a preferred embodiment of an optical fiber length measuring method.
The optical fiber length measuring method is applied to the optical fiber length measuring system and is used for measuring the length of an optical fiber to be measured, and the optical fiber length measuring method comprises the following steps:
s10, calibrating the optical paths of the coherent light path and the reference light path to make the optical paths equal;
s20, connecting the optical fiber to be tested into a coherent optical path, and connecting the standard optical fiber into a reference optical path;
s50, adjusting the optical path of the reference optical path beam;
s60, monitoring the optical power of the light beam after the coherent light path and the reference light path are combined;
s70, obtaining an optical path adjusting distance corresponding to the maximum optical power after beam closing;
and S80, obtaining the length of the optical fiber to be measured according to the optical path adjusting distance.
The optical path of the reference light path light beam is adjusted, so that the optical paths of the coherent light path and the reference light path are matched, the light beams of the two light paths generate white light interference, the light power of the light beams after the two light paths are combined changes, when the light power is maximum, the optical path difference of the two light paths is zero, the optical path adjusting distance corresponding to the maximum light power after the light paths are combined is obtained, and the length of the optical fiber to be measured can be calculated according to the optical path adjusting distance. The method for measuring the length of the optical fiber can be widely applied to the measurement of the length of the medium-short optical fiber.
Further, referring to fig. 7, before adjusting the optical path of the reference optical path beam, the method further includes the steps of:
s30, synchronously monitoring the optical power of the coherent light path and the reference light path;
and S40, adjusting the welding angle of the coherent light path and the reference light path with the double fiber ends of the polarization-maintaining coupler, so that the energy of the two light beams of the coherent light path and the reference light path is equal and the two light beams are output after being combined.
The output energy balance of the two optical paths is controlled by adjusting the welding angles of the coherent optical path and the reference optical path and the double fiber ends of the polarization-maintaining coupler, so that the double-path interference contrast is further improved.
Further, referring to fig. 8, step S70 specifically includes the following steps:
s71, acquiring a first position point corresponding to the optical path adjusting unit when the optical paths of the two optical paths before the optical fiber to be detected and the standard optical fiber are not accessed are equal;
s72, acquiring a second position point corresponding to the optical path adjusting unit when the optical paths of the two optical paths are equal after the optical fiber to be detected and the standard optical fiber are accessed;
and S73, acquiring an optical path adjusting distance corresponding to the maximum optical power after beam combination according to the first position point and the second position point.
The first position point and the second position point corresponding to the optical path adjusting unit specifically refer to the position point of a position cursor indicated by the reflector on the adjusting guide rail before and after the reflector is moved, and the moving distance of the reflector can be calculated by acquiring the first position point and the second position point, that is, the optical path adjusting distance corresponding to the maximum optical power after beam closing is acquired, and the length of the optical fiber to be measured can be obtained according to the optical path adjusting distance.
The method for measuring the length of the optical fiber utilizes the coherent length in the white light scanning interference technology
(λCIs the central wavelength, and delta lambda is the spectral width), the optical path difference of the coherent optical path and the reference optical path can generate interference within the coherent length range, when the optical path difference of the two optical paths is zero, the interference intensity is maximum, and the optical path is defined as L by adjusting the optical path of the reference optical path0And determining a zero optical path difference point of the two paths of white light coherence, namely the position of the envelope peak value with the maximum coherent intensity, thereby determining the length of the optical fiber to be detected.
The following three specific embodiments are described in detail, in which an ASE light source is used as a light source, an optical fiber to be measured is connected to a coherent light path through an optical fiber connector, the optical fiber to be measured is connected to the coherent light path through a second circulator, and an adjustable single-point light source is used as the light source and the optical fiber to be measured is connected to the coherent light path through the optical fiber connector:
example one
Referring to fig. 1 and 9, when the optical fiber to be measured is connected to the coherent optical path through the optical fiber connector, the specific process of measuring the length of the optical fiber is as follows:
manually adjusting an adjusting guide rail of the optical path adjusting unit to drive the reflecting mirror to start moving from the calibrated motion starting point position, starting optical path scanning, changing the optical path of the reference optical path, and adjusting the optical path difference of two arms of the MZI interference optical path from L0Through zero passage, scan to-L0Monitoring the change condition of the output light power value of the optical power meter along with the scanning optical path:
(1) when the optical path difference is equal to L0When the optical path of the scanned reference beam is matched with the optical path of the coherent beam transmitted by the coherent light path, white light interference is generated, and the optical power meter firstly generates power fluctuation;
(2) when the optical path difference is zero, namely the optical paths of the coherent light path and the reference light path are equal, the light intensity peak amplitude of the combined beam is the intensity superposition of the coherent light path and the reference light pathAdding the maximum amplitude position of the optical power meter, namely a zero optical path point; the peak amplitude of the light intensity of the beam after beam combination is in direct proportion to the input power of the light source, i.e. Imain∝I0，ImainAmplitude of peak light intensity, I0Inputting optical power for a light source;
(3) when the optical path difference is equal to-L0In the process, the optical path lengths of the scanned reference beam and the coherent beam transmitted by the coherent light path are still in a matching state, the optical path difference is continuously increased, and the optical power tends to be stable and does not change any more.
In this embodiment, the length of the optical fiber to be measured can be calculated by the following formula:
wherein, Δ L is the displacement Δ L from the zero optical path difference position during calibration of the optical fiber length measuring system to the maximum position of the scanning optical power after the optical fiber to be measured is accessed, the displacement can be positive, the distance between the lens and the reflector of the collimator is correspondingly increased, the displacement can also be negative, the distance between the lens and the reflector of the collimator is correspondingly reduced, n is the refractive index of the optical fiber to be measured, L is the refractive index of the optical fiber to be measured, and the displacement Δ L is the displacement Δ L from theStandard of meritFor a known length of standard optical fiber, according to known Δ L, n and LStandard of meritThe length of the optical fiber to be measured can be calculated.
Example two
Referring to fig. 2 and 9, when the optical fiber to be measured is connected into the coherent light path through the second circulator, the light n x (L) is specularly reflected by the end face of the optical fiber to be measuredStandard of merit-2*LTo be measured) Interference is realized with a reference light path, and the reflection return loss is near 15 dB; splitting ratio selection of coupler 1: 99, the reference optical path transmits 1% of light energy, and the coherent optical path transmits 99% of light energy. The optical path adjusting process is the same as that of the first embodiment, the adjusting guide rail of the optical path adjusting unit is manually adjusted, the optical path of the reference optical path is changed, and the optical path difference of two arms of the MZI interference optical path is L0Through zero passage, scan to-L0The change process of the light intensity of the combined beam along with the optical path difference is the same as the change process of the optical fiber to be detected accessing the coherent light path by adopting the optical fiber connector, and the length of the optical fiber to be detected is obtained by the following calculation:
delta L is the displacement from the zero optical path difference position during calibration of the optical fiber length measuring system to the maximum position of the scanning optical power after the optical fiber to be measured is accessed, the displacement can be positive, the distance between the lens and the reflector of the collimator is correspondingly increased, the displacement can also be negative, the distance between the lens and the reflector of the collimator is correspondingly reduced, n is the refractive index of the optical fiber to be measured, L is the displacement from the zero optical path difference position toStandard of meritFor standard fiber lengths, according to known Δ L, n and LStandard of meritThe length of the optical fiber to be measured can be calculated.
Compared with the prior art, the optical fiber length measuring system adopting the ASE light source has the following advantages:
(1) by adopting an all-fiber optical path correlator structure, the wide-spectrum light source beam splitting and the linear polarization maintaining combined beam greatly inhibit interference beat noise, increase the interference contrast of polarized light in the same polarization direction and effectively improve the measurement sensitivity;
(2) the measurement results of the coupling light and the transmission light under the conditions of energy separation and energy balance are synthesized, so that the dynamic range and the sensitivity of measurement can be kept consistent, the absolute amplitude of polarization crosstalk is obtained, and the intensity of a light source and the fluctuation of connection loss between a device and a test system are eliminated;
(3) the MZI interference light path structure combines the circulator, the one-way coupler and the polarizer to synchronously form forward transmission, so that the influence of return light on a light source is avoided, energy is transmitted to the optical power meter in a one-way manner, and the energy utilization rate is improved;
(4) the optical path adjusting unit coupled by a collimator reflection method is adopted, the optical path scanning range is increased by using a long-focus single-fiber collimator and changing the clearance of the collimator, and the sensitivity of the coupling efficiency along with the change of the optical path is reduced;
(5) the light emitting power of the two polarizers of the MZI optical path is synchronously monitored, the light emitting included angle between the light emitting of the two polarizers and the light emitting of the polarization maintaining coupler is adjusted to ensure the consistency of the light power of the two polarizers, the coherent contrast is further improved, and the test precision is increased.
EXAMPLE III
Referring to FIG. 3, when the light source is switched into the optical fiber length measuring system by using the adjustable single-point light source, the optical path is adjusted by manually adjusting the sameThe adjusting guide rail of the element drives the reflector to move from the calibrated motion starting point position, and the light power change of the light beam after the two light paths are combined is observed. The C wave band of the adjustable single-point light source is 40nm, and the central wavelength of the C wave band is lambda0Wavelength sweep width λDWavelength scan spacing of λΔThe length of the optical fiber to be measured can be calculated by the following formula:
wherein, Δ λ is the variation period of optical power with wavelength, Δ L is the displacement from the zero optical path difference position during calibration of the optical fiber length measurement system to the maximum position of the scanning optical power after the optical fiber to be measured is accessed, the displacement can be positive, the distance between the lens and the reflector of the collimator is correspondingly increased, the displacement can also be negative, the distance between the lens and the reflector of the collimator is correspondingly reduced, n is the refractive index of the optical fiber to be measured, L is the refractive index of the optical fiber to be measured, andstandard of meritIs the length of the standard optical fiber according to the known delta L, n, lambda0、LStandard of meritAnd delta lambda, the length of the optical fiber to be measured can be calculated. In the specific operation process, the optical path adjusting unit is adjusted to enable the scanning period to be reduced, so that the positive and negative values of the optical path difference value are judged; in order to better determine the optical path difference through the optical power change, the optical path adjusting unit adjusts the optical path difference of the two paths to ensure that the optical path is in
In the meantime. In the optical fiber length measuring system using the adjustable single-point light source, the relationship graph of the light intensity of the combined beam along with the wavelength change under different optical path differences is shown in fig. 10 to 13. In the optical fiber length measuring system, the transmission mode of the first polarizer, the second polarizer and the polarization-maintaining polarizer is adopted in the rear half section of optical path, so that the stable optical path transmission is facilitated, the light intensity of the two optical paths is synchronously adjusted, the contrast can be improved, and the wavelength scanning precision is improved.
The length of the optical fiber to be measured can be obtained through the specific implementation manners of the first embodiment to the third embodiment, the measurement range of the length of the optical fiber is obtained by dividing the movable range of the adjusting guide rail by n, and n is the refractive index of the optical fiber to be measured.
It should be understood that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same, and those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some technical features; and all such modifications and alterations are intended to fall within the scope of the appended claims.
Claims (9)
1. An optical fiber length measuring system is used for measuring the length of an optical fiber to be measured and is characterized by comprising a light source, a coupler, a standard optical fiber, an optical path adjusting unit, a first polarizer, a second polarizer, a polarization maintaining coupler and an optical power meter, wherein light beams emitted by the light source are split by the coupler to form two light beams, wherein,
a light beam sequentially passes through the optical fiber to be detected and the first polarizer and then is transmitted to the input end of the polarization maintaining coupler to form a coherent light path;
the other light beam is transmitted to the input end of the polarization maintaining coupler after sequentially passing through the standard optical fiber, the optical path adjusting unit and the second polarizer to form a reference optical path;
after the two light beams are combined by the polarization maintaining coupler, the light beam optical path of the coherent light path is matched with the light beam optical path of the reference light path to generate white light interference;
and transmitting the combined light to an optical power meter for optical power monitoring, and acquiring an optical path adjusting distance corresponding to the maximum optical power so as to acquire the length of the optical fiber to be detected.
2. The optical fiber length measuring system according to claim 1, wherein the optical path adjusting unit includes a first circulator, a collimator, a mirror, and an adjusting mechanism for adjusting a distance between the collimator and the mirror, the first circulator has a first port, a second port, and a third port, a light beam output from the standard optical fiber is incident on the first port of the first circulator, the light beam is transmitted into the second port from the first port, exits to the collimator and is transmitted to the mirror, and is reflected by the mirror and is output to the second polarizer via the collimator, the second port, and the third port in sequence.
3. The optical fiber length measuring system according to claim 2, wherein the adjusting mechanism comprises an adjusting guide provided with a position cursor, and the mirror is slidably disposed on the adjusting guide to adjust a distance between the mirror and the collimator.
4. The optical fiber length measuring system according to claim 1, further comprising a second circulator disposed between the optical fiber under test and the first polarizer, wherein the light beam output from the optical fiber under test is transmitted to the first polarizer through the second circulator.
5. The optical fiber length measuring system according to any one of claims 1 to 4, wherein the light source is an ASE light source.
6. The optical fiber length measuring system according to any one of claims 1 to 4, wherein the light source is an adjustable single point light source.
7. An optical fiber length measuring method applied to the optical fiber length measuring system according to any one of claims 1 to 6 for measuring the length of an optical fiber to be measured, the optical fiber length measuring method comprising the steps of:
calibrating the optical paths of the coherent light path and the reference light path to ensure that the optical paths of the two light paths are equal;
the optical fiber to be measured is accessed into a coherent optical path, and the standard optical fiber is accessed into a reference optical path;
adjusting the optical path of the reference optical path light beam;
monitoring the optical power of a light beam after the coherent light path and the reference light path are combined;
acquiring an optical path adjusting distance corresponding to the maximum optical power after beam closing;
and the length of the optical fiber to be measured is obtained according to the optical path adjusting distance.
8. The optical fiber length measuring method according to claim 7, further comprising, before adjusting the optical path of the reference optical path beam, the steps of:
synchronously monitoring the optical power of a coherent light path and a reference light path;
and adjusting the welding angles of the coherent light path and the reference light path and the double fiber ends of the polarization-maintaining coupler to enable the energy of the two light beams of the coherent light path and the reference light path to be equal and output after the two light beams are combined.
9. The method for measuring the length of the optical fiber according to claim 7, wherein the step of obtaining the optical path adjusting distance corresponding to the maximum optical power after the beam combining comprises the steps of:
acquiring a first position point corresponding to an optical path adjusting unit when the optical paths of the two optical paths before the optical fiber to be detected is not accessed and the standard optical fiber are equal;
acquiring a second position point corresponding to the optical path adjusting unit when the optical paths of the two optical paths are equal after the optical fiber to be detected and the standard optical fiber are accessed;
and acquiring an optical path adjusting distance corresponding to the maximum optical power after beam closing according to the first position point and the second position point.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010839533.4A CN112066887A (en) | 2020-08-19 | 2020-08-19 | Optical fiber length measuring system and measuring method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010839533.4A CN112066887A (en) | 2020-08-19 | 2020-08-19 | Optical fiber length measuring system and measuring method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112066887A true CN112066887A (en) | 2020-12-11 |
Family
ID=73662221
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010839533.4A Pending CN112066887A (en) | 2020-08-19 | 2020-08-19 | Optical fiber length measuring system and measuring method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112066887A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113324485A (en) * | 2021-05-26 | 2021-08-31 | 国开启科量子技术(北京)有限公司 | Arm length difference measuring system of unequal arm interferometer |
| CN113686245A (en) * | 2020-12-25 | 2021-11-23 | 深圳市中图仪器股份有限公司 | Ranging system with polarization maintaining optical fiber |
| CN114112313A (en) * | 2021-12-02 | 2022-03-01 | 中国电子科技集团公司第四十六研究所 | Single-polarization optical fiber transmission performance testing device and testing method |
| CN114779485A (en) * | 2022-03-31 | 2022-07-22 | 昂纳信息技术（深圳）有限公司 | Annular light beam generating system and device thereof |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2513077Y (en) * | 2001-09-12 | 2002-09-25 | 复旦大学 | Interference type optic fibre length measurer |
| CN101319878A (en) * | 2008-07-15 | 2008-12-10 | 浙江大学 | Method and device for high-precision large-range measuring size of optical fiber |
| CN201242428Y (en) * | 2008-07-15 | 2009-05-20 | 浙江大学 | Apparatus for measuring optical fiber length rapidly |
| CN101561296A (en) * | 2009-05-19 | 2009-10-21 | 北京航空航天大学 | Low-coherence measuring method and system for fiber retardation |
| CN102636121A (en) * | 2012-03-09 | 2012-08-15 | 中国科学院西安光学精密机械研究所 | High-precision optical fiber length measuring system |
| CN102980599A (en) * | 2012-11-15 | 2013-03-20 | 浙江大学 | Precise length matching method in optical fiber interference optical paths |
| CN103591895A (en) * | 2013-11-07 | 2014-02-19 | 中国电子科技集团公司第四十一研究所 | Optical fiber length measuring system and measuring method |
| US20150285617A1 (en) * | 2012-12-13 | 2015-10-08 | Toyo Seikan Group Holdings, Ltd. | Method and device for measuring polishing amount of optical fiber component |
| CN106546177A (en) * | 2016-10-24 | 2017-03-29 | 金陵科技学院 | It is a kind of measurement fiber coupler tail optical fiber length difference away from system and method |
| CN106969714A (en) * | 2017-05-02 | 2017-07-21 | 中国航空工业集团公司北京长城计量测试技术研究所 | A kind of method of the fine length of precise measuring |
| CN108692749A (en) * | 2018-04-27 | 2018-10-23 | 天津大学 | Mach-Zehnder interferometer optical path difference measurement device and method based on polarization interference |
-
2020
- 2020-08-19 CN CN202010839533.4A patent/CN112066887A/en active Pending
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2513077Y (en) * | 2001-09-12 | 2002-09-25 | 复旦大学 | Interference type optic fibre length measurer |
| CN101319878A (en) * | 2008-07-15 | 2008-12-10 | 浙江大学 | Method and device for high-precision large-range measuring size of optical fiber |
| CN201242428Y (en) * | 2008-07-15 | 2009-05-20 | 浙江大学 | Apparatus for measuring optical fiber length rapidly |
| CN101561296A (en) * | 2009-05-19 | 2009-10-21 | 北京航空航天大学 | Low-coherence measuring method and system for fiber retardation |
| CN102636121A (en) * | 2012-03-09 | 2012-08-15 | 中国科学院西安光学精密机械研究所 | High-precision optical fiber length measuring system |
| CN102980599A (en) * | 2012-11-15 | 2013-03-20 | 浙江大学 | Precise length matching method in optical fiber interference optical paths |
| US20150285617A1 (en) * | 2012-12-13 | 2015-10-08 | Toyo Seikan Group Holdings, Ltd. | Method and device for measuring polishing amount of optical fiber component |
| CN103591895A (en) * | 2013-11-07 | 2014-02-19 | 中国电子科技集团公司第四十一研究所 | Optical fiber length measuring system and measuring method |
| CN106546177A (en) * | 2016-10-24 | 2017-03-29 | 金陵科技学院 | It is a kind of measurement fiber coupler tail optical fiber length difference away from system and method |
| CN106969714A (en) * | 2017-05-02 | 2017-07-21 | 中国航空工业集团公司北京长城计量测试技术研究所 | A kind of method of the fine length of precise measuring |
| CN108692749A (en) * | 2018-04-27 | 2018-10-23 | 天津大学 | Mach-Zehnder interferometer optical path difference measurement device and method based on polarization interference |
Non-Patent Citations (4)
| Title |
|---|
| N.N. SUBHASHREE OJHA等: "《Post-fabrication refractive index sensitivity enhancement technique for single-fiber Mach-Zehnder interferometer》", 《OPTICAL FIBER TECHNOLOGY》 * |
| 叶全意等: "《基于相位调制光链路的光纤长度测量系统》", 《中国激光》 * |
| 朱兴邦等: "《基于调制相移法的高准确度光纤长度测量技术》", 《光子学报》 * |
| 邱永成: "《新型全光纤电流传感器光路结构研究》", 《中国优秀博硕士学位论文全文数据库(硕士) 信息科技辑》 * |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113686245A (en) * | 2020-12-25 | 2021-11-23 | 深圳市中图仪器股份有限公司 | Ranging system with polarization maintaining optical fiber |
| CN113324485A (en) * | 2021-05-26 | 2021-08-31 | 国开启科量子技术(北京)有限公司 | Arm length difference measuring system of unequal arm interferometer |
| CN114112313A (en) * | 2021-12-02 | 2022-03-01 | 中国电子科技集团公司第四十六研究所 | Single-polarization optical fiber transmission performance testing device and testing method |
| CN114112313B (en) * | 2021-12-02 | 2024-04-19 | 中国电子科技集团公司第四十六研究所 | Single polarization optical fiber transmission performance testing device and testing method |
| CN114779485A (en) * | 2022-03-31 | 2022-07-22 | 昂纳信息技术（深圳）有限公司 | Annular light beam generating system and device thereof |
| CN114779485B (en) * | 2022-03-31 | 2023-08-29 | 昂纳科技(深圳)集团股份有限公司 | Annular light beam generation system and device thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112066887A (en) | Optical fiber length measuring system and measuring method thereof | |
| CN102279095B (en) | Device for reducing influence of birefringent chromatic dispersion on polarization coupling measurement of polarization maintaining optical fiber | |
| CN102928199B (en) | Device and method for improving polarization crosstalk measurement performance of optical device | |
| CN102288388B (en) | Device and method for improving polarization-maintaining optical fiber polarization coupling measurement precision and symmetry | |
| JP3335205B2 (en) | Optical system calibration method | |
| US5202745A (en) | Polarization independent optical coherence-domain reflectometry | |
| CN103900797B (en) | With the optical coherence territory polarimeter of light path scanning position and velocity correction | |
| CN102928198B (en) | All-fiber testing device for testing polarization crosstalk of optical device | |
| CN103900798B (en) | A kind of optical coherence domain polarization measurement device scanning on-line correction with light path | |
| CN105784336B (en) | A kind of transmission of optical fibre device and reflecting properties test device and method | |
| CN103900680B (en) | A kind of device utilizing light source to suppress polarization crosstalk to measure noise and detection method | |
| EP0484913B1 (en) | Polarization independent optical coherence-domain reflectometry | |
| CN103900799B (en) | A kind of optical coherence polarimeter that suppresses interaction noise | |
| CN113804302A (en) | Optical fiber distributed polarization crosstalk rapid measuring device based on optical frequency domain interference | |
| CN108106817B (en) | Method for improving polarization performance measurement accuracy of Y waveguide device | |
| CN105241482A (en) | Active fiber grating sensor wavelength demodulation system and method | |
| US5654793A (en) | Method and apparatus for high resolution measurement of very low levels of polarization mode dispersion (PMD) in single mode optical fibers and for calibration of PMD measuring instruments | |
| CN204255613U (en) | A kind of Sagnac annular light path is embedded in the optics autocorrelation function analyzer of non-equilibrium Mach-Zehnder type light path scanner | |
| CN113804299A (en) | Optical fiber device distributed bidirectional polarization measuring device based on optical frequency domain interference | |
| CN113503901A (en) | Device and method for eliminating measurement signal jitter of white light interferometer | |
| CN104634370B (en) | Laser-based sensor | |
| CN104677596A (en) | Optical autocorrelator with unbalanced Mach-Zehnder type optical path scanner embedded in Sagnac annular light path | |
| CN104503081A (en) | Common optical path Fizeau interferometer type optical path correlator based on annular fiber mirror | |
| CN102135437B (en) | Method and device for inquiring signals by unbalanced Mach-Zehnder interferometer | |
| CN103743487B (en) | A kind of optical coherence domain polarization measurement device |
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 | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20201211 |