CN117134822A - Optical fiber polarization mode dispersion test system and method - Google Patents
Optical fiber polarization mode dispersion test system and method Download PDFInfo
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- CN117134822A CN117134822A CN202311097466.3A CN202311097466A CN117134822A CN 117134822 A CN117134822 A CN 117134822A CN 202311097466 A CN202311097466 A CN 202311097466A CN 117134822 A CN117134822 A CN 117134822A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 82
- 230000010287 polarization Effects 0.000 title claims abstract description 60
- 238000012360 testing method Methods 0.000 title claims abstract description 37
- 239000006185 dispersion Substances 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims abstract description 13
- 238000012545 processing Methods 0.000 claims abstract description 25
- 239000002131 composite material Substances 0.000 claims abstract description 15
- 238000005314 correlation function Methods 0.000 claims abstract description 13
- 238000005311 autocorrelation function Methods 0.000 claims abstract description 11
- 239000000835 fiber Substances 0.000 claims abstract description 11
- 230000003287 optical effect Effects 0.000 claims description 16
- 238000010998 test method Methods 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000004148 unit process Methods 0.000 claims description 2
- 238000005305 interferometry Methods 0.000 abstract description 9
- 230000005540 biological transmission Effects 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07951—Monitoring or measuring chromatic dispersion or PMD
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2589—Bidirectional transmission
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2589—Bidirectional transmission
- H04B10/25891—Transmission components
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
Abstract
The invention provides an optical fiber polarization mode dispersion test system and method, comprising the following steps: a broadband light source; a polarizer; an analyzer; the polarization beam splitter is used for receiving the composite light from the output end of the optical fiber combiner and separating the composite light into a first interference pattern and a second interference pattern of two mutually orthogonal polarization states; a photodetector for converting the first interferogram into a first interferogram electrical signal, or converting the second interferogram into a second interferogram electrical signal; and the control processing unit is used for processing the first interference pattern electric signal and/or the second interference pattern electric signal, calculating an independent autocorrelation function and a cross correlation function, and determining polarization mode dispersion of the tested device according to the autocorrelation function and the cross correlation function. The invention also provides a method for testing the polarization mode dispersion of the optical fiber. The invention has the advantages that: the optical fiber splitter, the optical fiber delay line and the optical fiber combiner are adopted to replace an interferometer adopted by the existing interferometry, so that an all-fiber structure for polarization mode dispersion test is realized.
Description
Technical Field
The invention relates to the technical field of optical communication, in particular to an optical fiber polarization mode dispersion test system and method.
Background
Single mode optical fibers are ideally homogeneous media that support only one mode, however due to birefringence, the propagation mode degrades into two transmission modes that employ orthogonal polarizations and define two Principal Polarization States (PSPs). The two PSPs propagate at different speeds and arrive at different times at the fiber output, thereby causing pulse stretching and signal distortion. The time difference between the arrival of two PSPs at the fiber output is called Differential Group Delay (DGD). Determining the PMD of an optical fiber may help determine the capacity of the fiber transmission, as well as the design and control for PMD compensators.
As known from the fiber polarization mode dispersion test method specified in section 48 of the national standard GBT15972.48-2016 fiber test method specification, the PMD measurement method commonly used at present comprises an interferometry. Interferometry is the transmission of a broadband light source through a Device Under Test (DUT) into an interferometer, which commonly used interferometers such as Michelson interferometers include a beam splitter, a fixed mirror, and a movable mirror, where the beam splitter splits the light into two beams, the fixed mirror and the movable mirror each reflect one beam, and then recombine the two beams into a composite beam. The position of the movable reflecting mirror is continuously changed, so that the optical path length of one beam of light is changed, the optical path difference between two interference arms is changed, the two beams of light interfere in a composite time phase, and an interference pattern is generated after the composite light leaves the interferometer. In conventional interferometry, the average DGD value is calculated from the interference fringe envelope. However, the resulting fringe envelope is a combination of two functions, and an algorithm must be used to try to remove the center autocorrelation peak that does not contain PMD information. The general interferometry can obtain an interferogram without a central peak by means of a polarizing beam splitter.
Because the interferometer adopted by the existing interferometry comprises optical components such as a reflecting mirror, the problems of difficult coupling of space light into the optical fiber, low coupling efficiency and the like exist, and the obtained interferogram is also easily influenced by environmental vibration.
Disclosure of Invention
In order to overcome the defects, the invention provides an all-fiber testing system based on a general interferometry to realize the measurement of polarization mode dispersion.
The invention provides an optical fiber polarization mode dispersion test system and method, comprising the following steps: a broadband light source; a polarizer polarizing light from the broadband light source and applying the polarized light to an input of a device under test; an analyzer for detecting the polarization state of light leaving the output end of the device under test and applying polarized light to the input end of the optical fiber splitter; the first output end of the optical fiber branching device is connected with the first input end of the optical fiber combiner through an optical fiber delay line, and the second output end of the optical fiber branching device is connected with the second input end of the optical fiber combiner; a polarization beam splitter, configured to receive the composite light from the output end of the optical fiber combiner, and separate the composite light into a first interference pattern and a second interference pattern with two mutually orthogonal polarization states; a photodetector for converting the first interferogram into a first interferogram electrical signal or converting the second interferogram into a second interferogram electrical signal; and the control processing unit is used for processing the first interference pattern electric signal and/or the second interference pattern electric signal, calculating independent autocorrelation function and cross correlation function, and determining polarization mode dispersion of the tested device according to the autocorrelation function and the cross correlation function.
Preferably, the device under test is an optical fiber.
Preferably, the control processing unit changes the polarization state of light in the optical fiber through an optical fiber polarization controller.
Preferably, the optical fiber splitter is a 1*2 splitter and the optical fiber combiner is a 2*1 combiner.
The invention also provides a method for testing the polarization mode dispersion of the optical fiber, which adopts the testing system and comprises the following steps:
s1, outputting light by the broadband light source;
s2, the optical fiber branching device divides light into two paths, and the optical path difference between the two paths of light is regulated by the optical fiber delay line;
s3, the optical fiber combiner combines two paths of light with a certain optical path difference to form composite light;
s4, the polarization beam splitter separates the composite light into a first interference pattern and a second interference pattern of two mutually orthogonal polarization states, the first interference pattern is provided for a first light detector, the second interference pattern is provided for a second light detector, the first light detector and the second light detector complete conversion from light signals to electric signals, and the electric signals are provided for the control processing unit;
s5, the control processing unit processes the electric signals and calculates polarization mode dispersion of the tested device.
Preferably, in the above step S5, the control processing unit obtains an autocorrelation function and a cross-correlation function by calculating a sum and a difference of electric signals from the first and second photodetectors, thereby calculating polarization mode dispersion of the device under test.
The invention has the advantages that: the optical fiber splitter, the optical fiber delay line and the optical fiber combiner are adopted to replace an interferometer adopted by the existing interferometry, so that an all-fiber structure for polarization mode dispersion test is realized, when the optical path difference of two paths of light is regulated, the relation between the position of the movable reflecting mirror and the correlation function is converted into the relation between the delay time of the optical fiber delay line and the correlation function, and the calculation method is the same as that of the general interferometry. Compared with the prior art, the all-fiber structure has stronger anti-interference capability, does not need optical alignment, can be used immediately on the premise of no instability and no precision, is simpler to build and operate, and simultaneously has a smaller overall structure.
Drawings
FIG. 1 is a schematic diagram of an optical fiber polarization mode dispersion testing system of the present invention;
description of element numbers:
1. broadband light source
2. Polarizer
3. Device under test
4. Polarization analyzer
5. Optical fiber branching device
6. Optical fiber delay line
7. Optical fiber combiner
8. Polarization beam splitter
91. First photodetector
92. Second photodetector
10. Control processing unit
Detailed Description
The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and are not intended to be limiting.
In the description of the present invention, it should be noted that the terms "first," "second," and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and "coupled" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
Fig. 1 shows an optical fiber polarization mode dispersion test system provided by the invention, which comprises a broadband light source 1, a polarizer 2, a device under test 3, an analyzer 4, an optical fiber splitter 5, an optical fiber delay line 6, an optical fiber combiner 7, a polarization beam splitter 8, a light detector and a control processing unit 10. The broadband light source 1 may be a light emitting diode, an LED or an ultra-fluorescent light source, among others. The polarizer 2 polarizes the light from the broadband light source 1 and applies the polarized light to the input of the device under test 3. In one embodiment of the present invention, the device under test 3 is an optical fiber. The analyzer 4 is configured to detect the polarization state of light leaving the output of the device under test 3 and to apply polarized light to the input of the optical fiber splitter 5.
The optical fiber splitter 5 is a 1*2 splitter, and the optical fiber combiner 7 is a 2*1 combiner. The first output end of the optical fiber splitter 5 is connected with the first input end of the optical fiber combiner 7 through the optical fiber delay line 6, and the second output end of the optical fiber splitter 5 is connected with the second input end of the optical fiber combiner 7. The optical fiber splitter 5 splits the light received from the analyzer 4 into two paths of light, and the optical fiber delay line 6 delays the optical path length of one of the paths of light, thereby adjusting the optical path length difference between the two paths of light. When the optical fiber combiner 7 combines two paths of light, the two paths of light interfere with each other. Further, the optical fiber combiner 7 adopts a polarization maintaining optical fiber coupler to ensure that the polarization states of the two paths of light are consistent.
The polarization beam splitter 8 is configured to receive the combined light from the output end of the optical fiber combiner 7 and split the combined light into a first interference pattern and a second interference pattern of two mutually orthogonal polarization states. The number of photodetectors is two, including a first photodetector 91 and a second photodetector 92, the first photodetector 91 converts the first interferogram into a first interferogram electric signal, the second photodetector 92 converts the second interferogram into a second interferogram electric signal, and the first interferogram electric signal and the second interferogram electric signal are amplified and supplied to the control processing unit 10. The control processing unit 10 processes the first interferogram electric signal and/or the second interferogram electric signal, extracts interferograms of two polarization states, calculates independent autocorrelation functions and cross-correlation functions, and determines polarization mode dispersion of the device under test 3 according to the autocorrelation functions and cross-correlation functions.
The form of the control processing unit 10 is not limited, and an existing technology such as a PLC controller or a single chip microcomputer can be adopted, and the technology of performing signal processing analysis and calculation by the control processing unit 10 is the existing technology that can be implemented by a person skilled in the art, and is not described herein again. Further, the control processing unit 10 also changes the polarization state of the light in the tested optical fiber through the optical fiber polarization controller. The existing optical fiber polarization controller generates stress birefringence by winding the optical fiber on a circular disk or by pressing the optical fiber, thereby forming an independent wave plate and changing the polarization state of light transmitted in the optical fiber.
The invention also provides a method for testing the polarization mode dispersion of the optical fiber, which adopts the testing system and comprises the following steps:
s1, outputting light by the broadband light source 1.
S2, the optical fiber splitter 5 divides the light into two paths, and the optical path difference between the two paths of light is adjusted by the optical fiber delay line 6.
And S3, the optical fiber combiner 7 combines two paths of light with a certain optical path difference to form composite light.
S4, the polarization beam splitter 8 separates the composite light into a first interference pattern and a second interference pattern of two mutually orthogonal polarization states, the first interference pattern is provided to the first light detector 91, the second interference pattern is provided to the second light detector 92, the first light detector 91 and the second light detector 92 complete conversion from optical signals to electrical signals, and the electrical signals are provided to the control processing unit 10.
S5, the control processing unit 10 processes the electric signals and calculates polarization mode dispersion of the tested device 3.
Further, in the above-described step S5, the control processing unit 10 obtains the autocorrelation function and the cross-correlation function by calculating the sum and the difference of the electric signals from the first photodetector 91 and the second photodetector 92, and thereby calculates the polarization mode dispersion of the device under test 3. The specific calculation method is the prior art, and the national standard GBT15972.48-2016 (section 48 of the optical fiber test method Specification): the transmission characteristics and the optical characteristics are measured by a method and a test program of polarization mode dispersion, which are described in detail herein, and are not described in detail.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and substitutions can be made by those skilled in the art without departing from the technical principles of the present invention, and these modifications and substitutions should also be considered as being within the scope of the present invention.
Claims (6)
1. A system and a method for testing polarization mode dispersion of an optical fiber are characterized by comprising the following steps:
a broadband light source;
a polarizer polarizing light from the broadband light source and applying the polarized light to an input of a device under test;
an analyzer for detecting the polarization state of light leaving the output end of the device under test and applying polarized light to the input end of the optical fiber splitter;
the first output end of the optical fiber branching device is connected with the first input end of the optical fiber combiner through an optical fiber delay line, and the second output end of the optical fiber branching device is connected with the second input end of the optical fiber combiner;
a polarization beam splitter, configured to receive the composite light from the output end of the optical fiber combiner, and separate the composite light into a first interference pattern and a second interference pattern with two mutually orthogonal polarization states;
a photodetector for converting the first interferogram into a first interferogram electrical signal or converting the second interferogram into a second interferogram electrical signal;
and the control processing unit is used for processing the first interference pattern electric signal and/or the second interference pattern electric signal, calculating independent autocorrelation function and cross correlation function, and determining polarization mode dispersion of the tested device according to the autocorrelation function and the cross correlation function.
2. The test system of claim 1, wherein the device under test is an optical fiber.
3. The test system of claim 2, wherein the control processing unit changes the polarization state of light in the optical fiber via an optical fiber polarization controller.
4. The test system of claim 1, wherein the fiber optic splitter is a 1*2 splitter and the fiber optic combiner is a 2*1 combiner.
5. A method for testing polarization mode dispersion of an optical fiber, characterized in that the testing system according to any one of claims 1 to 4 is used, comprising the steps of:
s1, outputting light by the broadband light source;
s2, the optical fiber branching device divides light into two paths, and the optical path difference between the two paths of light is regulated by the optical fiber delay line;
s3, the optical fiber combiner combines two paths of light with a certain optical path difference to form composite light;
s4, the polarization beam splitter separates the composite light into a first interference pattern and a second interference pattern of two mutually orthogonal polarization states, the first interference pattern is provided for a first light detector, the second interference pattern is provided for a second light detector, the first light detector and the second light detector complete conversion from light signals to electric signals, and the electric signals are provided for the control processing unit;
s5, the control processing unit processes the electric signals and calculates polarization mode dispersion of the tested device.
6. The test method according to claim 5, wherein in the step S5, the control processing unit calculates polarization mode dispersion of the device under test by calculating a sum and a difference of electric signals from the first and second photodetectors to obtain an autocorrelation function and a cross correlation function.
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| CN202311097466.3A CN117134822A (en) | 2023-08-29 | 2023-08-29 | Optical fiber polarization mode dispersion test system and method |
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| CN202311097466.3A CN117134822A (en) | 2023-08-29 | 2023-08-29 | Optical fiber polarization mode dispersion test system and method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118329387A (en) * | 2024-05-11 | 2024-07-12 | 深圳市鹏大光电技术有限公司 | Automatic test method, system and storable medium for optical fiber branching device |
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2023
- 2023-08-29 CN CN202311097466.3A patent/CN117134822A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118329387A (en) * | 2024-05-11 | 2024-07-12 | 深圳市鹏大光电技术有限公司 | Automatic test method, system and storable medium for optical fiber branching device |
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