CN114938241A - Spatial mode multiplexing few-mode optical time domain reflectometer and implementation method thereof - Google Patents
Spatial mode multiplexing few-mode optical time domain reflectometer and implementation method thereof Download PDFInfo
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- H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
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Abstract
The invention provides a spatial mode multiplexing few-mode optical time domain reflectometer which comprises a parameter-adjustable optical pulse output module, a spatial mode excitation module, a spatial mode separation module, a multi-channel spatial mode synchronous detection module and a multi-channel spatial mode backward Rayleigh scattering signal processing and synthesizing module. The parameter-adjustable optical pulse output module generates parameter-adjustable optical pulses, the optical pulses are excited by the space mode excitation module and injected into the measured few-mode optical fiber link, backward Rayleigh scattering signals are extracted by the space mode separation module for separation, and the backward Rayleigh scattering signals are sent into the multi-path space mode backward Rayleigh scattering signal processing and synthesizing module to obtain a loss distribution curve of the measured few-mode optical fiber link after being synchronously detected by the multi-path space mode synchronous detection module, so that the type and the loss of a fault event are determined. By implementing the invention, the measurement times are rapidly increased through spatial mode multiplexing, the detection curve noise is reduced more rapidly, the signal-to-noise ratio of a high-order spatial mode is optimized, and the dynamic range of measurement is improved.
Description
Technical Field
The invention relates to the technical field of optical fiber fault detection, in particular to a spatial mode multiplexing few-mode optical time domain reflectometer and an implementation method thereof.
Background
With the increasing of communication services, people have increasingly increased demands for transmission capacity of communication systems, and various new technologies are emerging continuously. Currently, a new generation of Mode Division Multiplexing (MDM) based few-Mode fiber (Few-Mode fiber, FMF) communication technology is favored. The technology utilizes a limited orthogonal mode in few-mode optical fiber as an independent channel to carry out information transmission, can improve the system transmission capacity by times, breaks through the capacity limit of the traditional single-mode optical fiber system, and becomes a capacity expansion scheme which realizes the most competitive capacity of Tbit/s and even Pbit/s transmission capacities of low-delay large-bandwidth 5G networks, access networks, data centers and the like. In recent years, the rapid development of the mode division multiplexing communication technology enables optical fiber communication to take a new step in the fields of ultra-large capacity, ultra-long distance and ultra-high speed. Therefore, in the face of rapid development of few-mode optical fiber research and development, network construction and application, reliable and efficient operation of a long-distance large-capacity few-mode optical fiber link is ensured, and the research on novel few-mode optical fiber link fault detection technology is significant and has a wide development prospect.
At present, the fault detection of few-mode fiber links mainly continues the fault detection idea of traditional single-mode fibers, and mainly realizes adaptive measurement of different dynamic ranges and spatial resolutions by adjusting the detection Optical pulse width and peak power through a single-mode Optical time-domain reflectometer (OTDR). The method comprises the steps of detecting faults of a long-distance few-mode optical fiber link by adopting a large pulse width, and positioning faults with high precision by adopting a narrow pulse width. However, for the few-mode optical fiber link, the loss of each spatial mode is larger than that of a single-mode optical fiber, the power of a non-excited coupling mode is smaller, and the measurement signal-to-noise ratio is small, so that the dynamic range is smaller under the condition of the same pulse parameter. Therefore, in order to realize the same measurement dynamic range as that of the single-mode optical time domain reflectometer, the dynamic range of measurement needs to be improved by increasing the pulse width, which inevitably causes the phenomenon that the power of the few-mode optical fiber injected into the measured optical fiber is too large to generate a nonlinear effect, thereby affecting the measurement result. Meanwhile, considering the limitation of the normal operation of the line on the pulse power, for the few-mode optical time domain reflectometer, the actual requirement of the few-mode optical reflectometer on multi-scene measurement cannot be met only by adjusting the optical pulse width, namely the peak power, namely, the long-distance few-mode optical fiber link has long measurement time and poor real-time performance, and particularly, the average times are more during high-precision measurement, and the measurement time is longer. Therefore, how to effectively improve the dynamic range of the few-mode optical time domain reflectometer, improve the signal-to-noise ratio of the non-excited coupling mode and improve the measurement speed is an important content of the few-mode optical time domain reflectometer.
In the prior art, the few-mode optical time domain reflectometer adopts the following method to improve the dynamic range, reduce noise and improve the fault detection speed, and specifically includes: (1) the method for increasing the optical pulse width and the peak power can cause the limitation of the stimulated Brillouin scattering nonlinear effect of the few-mode optical fiber, and the dynamic range of the method is improved to a limited extent; (2) through the pulse coding mode, although the dynamic range can be improved, the system digital signal processing complexity is improved, and the system real-time performance is poor.
Therefore, there is a need to provide a new few-mode optical time domain reflectometer, which can implement real-time, efficient, low-cost, high-dynamic-range and high-spatial-resolution fault detection and location for a few-mode optical fiber link.
Disclosure of Invention
The technical problem to be solved in the embodiments of the present invention is to provide a spatial mode multiplexing few-mode optical time domain reflectometer and an implementation method thereof, which can rapidly increase the number of times of measurement through spatial mode multiplexing, can more rapidly reduce the noise of a detection curve, optimize the signal-to-noise ratio of a high-order spatial mode, and improve the dynamic range of measurement, thereby being capable of implementing fault detection and location of a few-mode optical fiber link with high efficiency, low cost, high dynamic range, and high spatial resolution in real time.
In order to solve the above technical problem, an embodiment of the present invention provides a spatial mode multiplexing few-mode optical time domain reflectometer, which is used for a measured few-mode optical fiber link, and includes a parameter-adjustable optical pulse output module, a spatial mode excitation module, a spatial mode separation module, a multi-channel spatial mode synchronous detection module, and a multi-channel spatial mode backward rayleigh scattering signal processing and synthesizing module, which are connected in sequence;
the parameter-adjustable optical pulse output module is used for generating optical pulses with specific parameters of repetition frequency, peak power and pulse width;
the space mode excitation module is used for carrying a fundamental mode LP of the light pulse 01 Mode conversionBecomes a base mold LP 01 The mode and the high-order space mode are injected into the tested few-mode optical fiber link;
the spatial mode separation module is used for extracting a backward Rayleigh scattering signal generated on the measured few-mode optical fiber link, separating the backward Rayleigh scattering signal and outputting a multi-routing fundamental mode LP 01 A mode-borne back-rayleigh scattered signal;
the multi-path spatial mode synchronous detection module is used for synchronously detecting a plurality of paths of basic modes LP 01 Synchronously detecting the mode-borne backward Rayleigh scattering signal to obtain a multi-path spatial mode backward Rayleigh scattering electric signal;
and the multi-path spatial mode back Rayleigh scattering signal processing and synthesizing module is used for carrying out digital signal processing and synthesizing on the multi-path spatial mode back Rayleigh scattering signals to obtain a loss distribution curve of the tested few-mode optical fiber link, and further determining the fault event type and the loss magnitude of the tested few-mode optical fiber link according to the loss distribution curve.
The parameter adjustable optical pulse output module consists of a single-frequency light source, an electro-optic modulator, a signal generator and an optical fiber amplifier; wherein the light pulse is generated by a light source through an electro-optic modulator driven by the signal generator.
The light pulse is a pulse light source with the pulse width of 200ns, the peak power of 40mw and the repetition frequency of 2 kHz.
The embodiment of the invention also provides a method for realizing the spatial mode multiplexing few-mode optical time domain reflectometer, which is realized on the spatial mode multiplexing few-mode optical time domain reflectometer, and the method comprises the following steps:
generating optical pulses with specific parameters of repetition frequency, peak power and pulse width;
a fundamental mode LP to carry the light pulse 01 Mode conversion to fundamental mode LP 01 A mode and a high-order spatial mode are injected into the tested few-mode optical fiber link;
extracting a backward Rayleigh scattering signal generated on the tested few-mode optical fiber link, and carrying out back Rayleigh scattering on the signalThe scattered signals are separated to output a plurality of routing fundamental modes LP 01 A mode-borne back-rayleigh scattered signal;
will multiplex the fundamental mode LP 01 Synchronously detecting the mode-borne backward Rayleigh scattering signal to obtain a multi-path spatial mode backward Rayleigh scattering electric signal;
and carrying out digital signal processing and synthesis on the multi-path space mode backward Rayleigh scattering signals to obtain a loss distribution curve of the measured few-mode optical fiber link, and further determining the fault event type and the loss of the measured few-mode optical fiber link according to the loss distribution curve.
Wherein the fundamental mode LP to carry the light pulse 01 Mode conversion to fundamental mode LP 01 The specific steps of injecting the mode and the high-order spatial mode into the tested few-mode optical fiber link are,
the single-mode tail fiber bearing the light pulse is subjected to eccentric fusion with the few-mode tail fiber at the port of the few-mode optical fiber circulator to excite a fundamental mode LP 01 And the mode and the high-order spatial mode are injected into the tested few-mode optical fiber link by a few-mode optical fiber circulator.
Wherein the separating the back Rayleigh scattering signals is accomplished by a mode multiplexer photon lantern.
The specific steps of processing and synthesizing the digital signals of the multiple spatial mode back rayleigh scattering signals to obtain the loss distribution curve of the measured few-mode optical fiber link include:
carrying out photoelectric detection and amplification on the multi-path space mode backward Rayleigh scattering signals;
sampling the multiple paths of space mode backward Rayleigh scattering signals after detection and amplification, and obtaining each path of space mode through digital signal processing;
after amplitude compensation, time sequence adjustment alignment, spatial mode signal power superposition and averaging are carried out on each path of spatial mode, all spatial mode signals are synthesized to obtain a loss distribution curve of the tested few-mode optical fiber link.
Wherein the light pulse is a pulse light source with pulse width of 200ns, peak power of 40mw and repetition frequency of 2kHz
The embodiment of the invention has the following beneficial effects:
compared with the traditional single-mode optical time domain reflectometer technology, the invention uses the multiplexing of the multi-path spatial mode, can efficiently improve the detection times and the number of measurement samples, increases the average measurement times, reduces the noise power, improves the low signal-to-noise ratio of the high-order spatial mode, improves the dynamic range, effectively improves the measurement speed, and improves the fault detection precision by combining the high sensitivity characteristic of the high-order spatial mode to the fault loss.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of a spatial mode multiplexing few-mode optical time domain reflectometer according to an embodiment of the present invention;
fig. 2 is an application scenario diagram of a spatial mode multiplexing few-mode optical time domain reflectometer according to an embodiment of the present invention;
fig. 3 is a schematic diagram of multiple spatial mode backward rayleigh scattering signals generated by optical pulse detection in an application scene of a spatial mode multiplexing few-mode optical time domain reflectometer according to an embodiment of the present invention;
FIG. 4 is a detection graph of the multiple spatial modes of the backward Rayleigh signal of FIG. 3 generated by amplitude compensation and superposition averaging;
fig. 5 is a flowchart of a spatial mode multiplexing few-mode optical time domain reflection method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, in an embodiment of the present invention, a spatial-mode multiplexing few-mode optical time domain reflectometer is provided, and is used for a measured few-mode optical fiber link, and includes a parameter-adjustable optical pulse output module 200, a spatial-mode excitation module 201, a spatial-mode separation module 202, a multi-channel spatial-mode synchronous detection module 203, and a multi-channel spatial-mode backward rayleigh scattering signal processing and synthesizing module 204, which are connected in sequence;
a parameter adjustable light pulse output module 200 for generating light pulses with specific parameters of repetition frequency, peak power and pulse width; the parameter-adjustable optical pulse output module 200 is composed of a single-frequency light source, an electro-optical modulator, a signal generator and an optical fiber amplifier, and the optical pulse is generated by the light source through the electro-optical modulator driven by the signal generator; in one example, the light pulse is a pulsed light source with a pulse width of 200ns, a peak power of 40mw, and a repetition frequency of 2 kHz; it can be understood that the pulse width, peak power and repetition frequency of the light pulse can be adjusted according to actual requirements;
a spatial mode excitation module 201 for exciting a fundamental mode LP carrying light pulses 01 Mode conversion to fundamental mode LP 01 Mode and higher order spatial modes LP i And injecting the optical fiber into the tested few-mode optical fiber link; in one example, a single-mode pigtail carrying light pulses is fused off-core with a few-mode pigtail at the port of a few-mode fiber circulator to excite a fundamental mode LP 01 Modal and higher order spatial modes LP i Injecting the few-mode optical fiber link to be detected by a few-mode optical fiber circulator;
a spatial mode separation module 202, configured to extract a backward rayleigh scattering signal generated on the measured few-mode optical fiber link, separate the backward rayleigh scattering signal, and output a multi-routing fundamental mode LP 01 A mode-borne back-rayleigh scattered signal; in one example, the back Rayleigh scattering signal generated on the measured few-mode fiber link is separated by the high-order spatial mode LP through the mode multiplexer photon lantern i Conversion to fundamental mode LP 01 Mode, thereby obtaining a multiple routing fundamental mode LP 01 A mode-borne back-rayleigh scattered signal;
multi-path space mode synchronous detectionA test module 203 for testing the multi-routing fundamental mode LP 01 Synchronously detecting the mode-borne backward Rayleigh scattering signals to obtain a plurality of paths of space mode backward Rayleigh scattering electrical signals; in one example, the multiple routing fundamental modes LP 01 The mode-carried back Rayleigh scattering signal is photoelectrically detected and converted into corresponding back Rayleigh scattering electric signal as a fundamental mode LP 01 Mode and higher order spatial modes LP i A back rayleigh scatter signal;
and the multi-path spatial mode back rayleigh scattering signal processing and synthesizing module 204 is configured to perform digital signal processing and synthesis on the multi-path spatial mode back rayleigh scattering signal to obtain a loss distribution curve of the measured few-mode optical fiber link, and further determine the fault event type and the loss magnitude of the measured few-mode optical fiber link according to the loss distribution curve. In one example, LP is applied to the fundamental mode 01 Mode and higher order spatial modes LP i Data acquisition, amplitude compensation of different spatial modes, time sequence adjustment alignment, spatial mode signal power superposition and averaging are carried out on backward Rayleigh scattering signals, a loss distribution curve of the tested few-mode optical fiber link is obtained, and fault detection of the few-mode optical fiber link is realized
As shown in fig. 2 to fig. 4, further description is made on an application scenario of the spatial mode multiplexing few-mode optical time domain reflectometer according to the embodiment of the present invention, which is specifically as follows:
in fig. 2, a single-frequency continuous detection light source is output by a single-frequency laser DFB-LD 1, enters an electro-optical modulator EOM 2, and generates a detection light pulse with adjustable frequency and pulse width under the driving of a signal generator SG 3, the detection light pulse output by the electro-optical modulator EOM 2 is amplified by an erbium-doped fiber amplifier EDFA4 and then injected into a few-mode fiber circulator 6, wherein the EDFA outputs a single-mode pigtail to be subjected to core-offset fusion 5 with a few-mode pigtail at an a port of the few-mode fiber circulator a, so as to realize the excitation of a high-order spatial mode; by utilizing the unidirectional transmission characteristic of the few-mode optical fiber circulator 6, the few-mode optical fiber circulator 6 is injected from the port a, and the output from the port B enters the tested few-mode optical fiber links 9, 10 and 11 through the connector (APC \ PC interface) 7, wherein the fault type 10 is generally fusion fault, connector mismatch, bending and the like. The backward Rayleigh scattered light generated in the few-mode optical fibers 9, 10 and 11 to be detected returns through the port B of the few-mode optical fiber circulator 6 and is output from the port C, then the backward Rayleigh scattered light enters the space mode demultiplexer photon lantern PL 12 to be subjected to multi-channel mixed space mode separation, and the few-mode tail fiber of the port C of the few-mode optical fiber circulator 6 and the few-mode tail fiber of the photon lantern PL 12 are subjected to center fusion. And each path of space mode output by the photon lantern PL 12 respectively enters the photoelectric detection PD 13 for photoelectric conversion, and a plurality of paths of space mode backward Rayleigh scattering electric signals are output. And entering a data acquisition ADC 14 for data acquisition, finally entering a digital signal processing 15, performing amplitude compensation of different spatial modes, time sequence adjustment alignment, spatial mode signal power superposition and average digital signal processing, and finally synthesizing all spatial mode signals to obtain a final fault detection result.
In FIG. 3, typical test results are generated for a probing pulse with a pulse width of 200ns, a peak power of 40mw, and a repetition frequency of 2kHz, the LP 01 、LP 11a 、LP 11b 、LP 21a 、LP 21b And LP 02 And respectively carrying out amplitude compensation, time sequence adjustment alignment, spatial mode signal power synthesis and averaging on the 6 spatial mode backward Rayleigh scattering signals to obtain a final test result.
In fig. 4, the small-mode optical fiber backward rayleigh dispersion loss distribution curves after synthesizing all spatial mode signals are obtained for amplitude compensation of different spatial modes, timing adjustment alignment, spatial mode signal power superposition and averaging, and the failure is a fusion splicing failure through analysis.
Therefore, compared with the single-mode optical fiber OTDR, the spatial mode multiplexing scheme adopted by the embodiment of the invention can efficiently improve the detection times and the number of measurement samples, effectively improve the measurement speed, have smaller fading noise and improve the dynamic range. Meanwhile, the scheme combines the high sensitivity characteristic of a high-order space mode to fault loss, and has higher fault detection and positioning accuracy compared with the traditional single-mode OTDR.
As shown in fig. 5, in an embodiment of the present invention, a method for implementing a spatial mode multiplexing few-mode optical time domain reflectometer is provided, which is implemented on the spatial mode multiplexing few-mode optical time domain reflectometer, and the method includes the following steps:
step S1, generating optical pulses with specific parameters of repetition frequency, peak power and pulse width;
step S2, carrying the light pulse base mode LP 01 Mode conversion to fundamental mode LP 01 The mode and the high-order space mode are injected into the tested few-mode optical fiber link;
step S3, extracting the back Rayleigh scattering signal generated on the tested few-mode optical fiber link, separating the back Rayleigh scattering signal, and outputting a multi-routing fundamental mode LP 01 A mode-borne back rayleigh scattered signal;
step S4, multiple routing basic model LP 01 Synchronously detecting the mode-borne backward Rayleigh scattering signals to obtain a plurality of paths of space mode backward Rayleigh scattering electrical signals;
and step S5, carrying out digital signal processing synthesis on the multi-path space mode backward Rayleigh scattering signals to obtain a loss distribution curve of the tested few-mode optical fiber link, and further determining the fault event type and the loss of the tested few-mode optical fiber link according to the loss distribution curve.
Wherein the fundamental mode LP to carry the light pulse 01 Mode conversion to fundamental mode LP 01 The specific steps of injecting the mode and the high-order spatial mode into the tested few-mode optical fiber link are,
the single-mode tail fiber bearing the light pulse is subjected to eccentric fusion with the few-mode tail fiber at the port of the few-mode optical fiber circulator to excite a fundamental mode LP 01 And the mode and the high-order spatial mode are injected into the tested few-mode optical fiber link by a few-mode optical fiber circulator.
Wherein said separating said backscattered Rayleigh signals is achieved by a mode multiplexer photon lantern.
The specific steps of processing and synthesizing the digital signals of the multiple spatial mode back rayleigh scattering signals to obtain the loss distribution curve of the measured few-mode optical fiber link include:
performing photoelectric detection and amplification on the multi-path space mode backward Rayleigh scattering signal;
sampling the multiple paths of space mode backward Rayleigh scattering signals after detection and amplification, and obtaining each path of space mode through digital signal processing;
after amplitude compensation, time sequence adjustment alignment, spatial mode signal power superposition and averaging are carried out on each path of spatial mode, all spatial mode signals are synthesized to obtain a loss distribution curve of the tested few-mode optical fiber link.
Wherein the light pulse is a pulse light source with pulse width of 200ns, peak power of 40mw and repetition frequency of 2kHz
The embodiment of the invention has the following beneficial effects:
compared with the traditional single-mode optical time domain reflectometer technology, the method has the advantages that the multiplexing of the multi-path spatial mode is used, the detection times and the number of the measurement samples can be efficiently increased, the average measurement times are increased, the noise power is reduced, the low signal-to-noise ratio of the high-order spatial mode is improved, the dynamic range is improved, the measurement speed is effectively improved, and the high sensitivity characteristic of the high-order spatial mode on fault loss is combined, so that the fault detection precision is improved.
It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by using a program to instruct related hardware, and the program may be stored in a computer readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (8)
1. A spatial mode multiplexing few-mode optical time domain reflectometer is used on a measured few-mode optical fiber link and is characterized by comprising a parameter-adjustable optical pulse output module, a spatial mode excitation module, a spatial mode separation module, a multi-path spatial mode synchronous detection module and a multi-path spatial mode back Rayleigh scattering signal processing and synthesizing module which are sequentially connected;
the parameter-adjustable optical pulse output module is used for generating optical pulses with specific parameters of repetition frequency, peak power and pulse width;
the space mode excitation module is used for exciting a fundamental mode LP for bearing the light pulse 01 Mode conversion to fundamental mode LP 01 A mode and a high-order spatial mode are injected into the tested few-mode optical fiber link;
the spatial mode separation module is used for extracting a back Rayleigh scattering signal generated on the tested few-mode optical fiber link, separating the back Rayleigh scattering signal and outputting a plurality of routing fundamental modes LP 01 A mode-borne back-rayleigh scattered signal;
the multi-path space mode synchronous detection module is used for LP of a multi-path basic mode 01 Synchronously detecting the mode-borne backward Rayleigh scattering signals to obtain a plurality of paths of space mode backward Rayleigh scattering electrical signals;
and the multi-path spatial mode back Rayleigh scattering signal processing and synthesizing module is used for carrying out digital signal processing and synthesizing on the multi-path spatial mode back Rayleigh scattering signals to obtain a loss distribution curve of the tested few-mode optical fiber link, and further determining the fault event type and the loss magnitude of the tested few-mode optical fiber link according to the loss distribution curve.
2. The spatial mode multiplexing few-mode optical time domain reflectometer of claim 1 wherein the parameter tunable optical pulse output module is comprised of a single frequency light source, an electro-optic modulator, a signal generator, and a fiber amplifier; wherein the light pulses are generated by a light source via an electro-optical modulator driven by the signal generator.
3. The spatial-mode-multiplexed few-mode optical time domain reflectometer as in claim 2 wherein the optical pulses are pulsed light sources having a pulse width of 200ns, a peak power of 40mw, and a repetition frequency of 2 kHz.
4. A method for implementing a spatial mode multiplexing few-mode optical time domain reflectometer, characterized in that it is implemented on the spatial mode multiplexing few-mode optical time domain reflectometer according to claim 3, the method comprising the following steps:
generating optical pulses with specific parameters of repetition frequency, peak power and pulse width;
a fundamental mode LP to carry the light pulse 01 Mode conversion to fundamental mode LP 01 A mode and a high-order spatial mode are injected into the tested few-mode optical fiber link;
extracting a back Rayleigh scattering signal generated on the tested few-mode optical fiber link, separating the back Rayleigh scattering signal, and outputting a multi-routing fundamental mode LP 01 A mode-borne back-rayleigh scattered signal;
multiple routing fundamental mode LP 01 Synchronously detecting the mode-borne backward Rayleigh scattering signals to obtain a plurality of paths of space mode backward Rayleigh scattering electrical signals;
and carrying out digital signal processing and synthesis on the multi-path space mode backward Rayleigh scattering signals to obtain a loss distribution curve of the measured few-mode optical fiber link, and further determining the fault event type and the loss of the measured few-mode optical fiber link according to the loss distribution curve.
5. The method of claim 4, wherein the LP carrying the fundamental mode of the optical pulses 01 Mode conversion to fundamental mode LP 01 The specific steps of injecting mode and high-order space mode into tested few-mode optical fiber link are,
carrying the single-mode tail fiber of the light pulse to perform eccentric fusion with the few-mode tail fiber of the port of the few-mode optical fiber circulator to excite a fundamental mode LP 01 And the mode and the high-order spatial mode are injected into the tested few-mode optical fiber link by a few-mode optical fiber circulator.
6. The method of claim 4, wherein the separating the back Rayleigh scattered signals is performed by a mode multiplexer photon lantern.
7. The method for implementing the spatial-mode multiplexing few-mode optical time domain reflectometer according to claim 4, wherein the step of performing digital signal processing and synthesis on the multiple spatial-mode backward rayleigh scattering signals to obtain the loss distribution curve of the measured few-mode optical fiber link includes:
carrying out photoelectric detection and amplification on the multi-path space mode backward Rayleigh scattering signals;
sampling the multiple paths of space mode backward Rayleigh scattering signals after detection and amplification, and obtaining each path of space mode through digital signal processing;
and after amplitude compensation, time sequence adjustment alignment, spatial mode signal power superposition and averaging are carried out on each path of spatial mode, all spatial mode signals are synthesized to obtain a loss distribution curve of the measured few-mode optical fiber link.
8. The method of claim 4, wherein the optical pulse is a pulsed light source with a pulse width of 200ns, a peak power of 40mw, and a repetition frequency of 2 kHz.
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| US20180052102A1 (en) * | 2016-08-22 | 2018-02-22 | Nec Laboratories America, Inc. | Distributed acoustic sensing in a multicore optical fiber using distributed mode coupling and delay |
| CN109120337A (en) * | 2018-10-31 | 2019-01-01 | 吉林大学 | A kind of few mould time-domain reflectomer |
| CN110071762A (en) * | 2019-04-30 | 2019-07-30 | 吉林大学 | A kind of less fundamental mode optical fibre fault detection method based on higher order mode back rayleigh scattering |
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