CN109120337A - A kind of few mould time-domain reflectomer - Google Patents
A kind of few mould time-domain reflectomer Download PDFInfo
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- CN109120337A CN109120337A CN201811284515.3A CN201811284515A CN109120337A CN 109120337 A CN109120337 A CN 109120337A CN 201811284515 A CN201811284515 A CN 201811284515A CN 109120337 A CN109120337 A CN 109120337A
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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
- H04B10/071—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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- 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
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/524—Pulse modulation
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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
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/54—Intensity modulation
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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
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
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Abstract
The invention discloses a kind of few mould time-domain reflectomers, belong to optic fibre characteristic field of measuring technique, are made of the acquisition of signal generator module, light path module, less fundamental mode optical fibre module to be measured, detecting module and data and processing module；Multifrequency light pulse signal is generated by signal generator module, light pulse signal is injected into light path module, spatial model conversion is carried out in light path module, optical signal after conversion enters less fundamental mode optical fibre module to be measured, the back rayleigh scattering light of less fundamental mode optical fibre module to be measured carries out modal cutoff back to light path module, the optical signal of modal cutoff enters detecting module and carries out photoelectric conversion, and the rear signal of conversion enters data acquisition and processing modules implement Signal sampling and processing is shown.The invention patent solve the problems, such as the online monitoring instruments applied to less fundamental mode optical fibre there are blank this, realize the monitoring of less fundamental mode optical fibre network intelligence, damage measurement, fault location function.
Description
Technical field
The invention belongs to optic fibre characteristic field of measuring technique, and in particular to a kind of few mould time-domain reflectomer.
Background technique
In recent years, Networks of Fiber Communications bandwidth demand is every year with 20%~40% rate sustainable growth.Standard single mode light
Fine message capacity is already close to non-linear shannon limit (100Tbit/s), according to conservative estimation, the single-mode optics that lay at present
Fine Transmission system is up to capacity limitation in coming 10 years.Therefore the mode multiplexing technology based on less fundamental mode optical fibre becomes research
Hot spot.It nets and predicts according to OFweek, less fundamental mode optical fibre is the next stop of optical fiber development, and less fundamental mode optical fibre communication network will be commercial in 5 years,
Become mainstream in 10 years.With the continuous development of the new technologies such as big data, cloud computing, less fundamental mode optical fibre applies meeting what signal transmitted
Constantly universal, therefore, the monitoring instrument for functions such as the monitoring of less fundamental mode optical fibre link network, damage measurement, fault location must not
It can lack.
Optical time domain reflectometer (OTDR, optical time domain re-flectometer) is that International Telecommunication Union pushes away
The fiber failure detecting instrument recommended, is widely used in optical fiber link fault detection.Traditional optical time domain reflectometer can only be examined
Single mode fiber link is surveyed, however is different from single mode optical fiber, less fundamental mode optical fibre has the mode of multiple parallel transmissions, the biography of each mode
Defeated characteristic is different, and can also have Mode Coupling between different mode.Less fundamental mode optical fibre link is assessed and is monitored, it is necessary to
Coupled characteristic between the transmission characteristic and different mode of each mode is measured comprehensively.This is current single mode optical fiber
What time-domain reflectomer cannot achieve.Therefore, it is necessary to develop a kind of few mould time-domain reflectomers, solve the intelligence prison of less fundamental mode optical fibre network
It surveys, damage the problems such as measurement and fault location.The practicalization that the development of the instrument will push less fundamental mode optical fibre to communicate, to big
The development of capacity optical communication network is of great significance.
Summary of the invention
The purpose of the present invention is, there are this status of blank, propose that one kind can be real for less fundamental mode optical fibre link monitoring instrument
Few mould time-domain reflectomer of the functions such as existing less fundamental mode optical fibre network intelligence monitoring, damage measurement, fault location.
To achieve the goals above, the invention adopts the following technical scheme:
A kind of few mould time-domain reflectomer, system block diagram is as shown in Figure 1, by signal generator module 1, light path module 2, to be measured
Less fundamental mode optical fibre module 3, detecting module 4 and data acquisition and processing module 5 form；Wherein, the light path module 2 includes mode
Converter, pattern demultiplexer and less fundamental mode optical fibre circulator；The course of work is as follows:
The signal generator module 1 generates pulse light, and then pulse light is transferred to light path module by optical fiber
2, pulse light is converted into corresponding single excitation mode light, single excitation mould by the mode converter in light path module 2
Formula light enters less fundamental mode optical fibre module 3 to be measured by the less fundamental mode optical fibre circulator in light path module 2；Less fundamental mode optical fibre module 3 to be measured
In the light energy of single excitation mode of less fundamental mode optical fibre can be coupled to other non-excitation modes (if excitation mode is LP01 mould
Formula is different from excitation mode other then other non-excitation modes are LP11a, LP11b, LP21a, LP21b, LP02 etc.
Mode.) in, the back rayleigh scattering optical signal of excitation mode and non-excitation mode can return light path mould through less fundamental mode optical fibre circulator
Block 2；Pattern demultiplexer in light path module 2 carries out modal cutoff, obtain corresponding LP01, LP11a, LP11b,
LP02 ... isotype is output to the output port of light path module 2；Then by detecting module 4 to the output end of light path module 2
The back rayleigh scattering scattering light letter of mouth is detected, then the signal after detection is input to data acquisition and processing module 5
In；In data acquisition and procession module 5, data are acquired using the data collecting card of data acquisition and processing module 5,
Then data are read, and denoising is carried out to data, the data and curves that optical power changes with transmission range are drawn, to obtain
Obtain the transmission situation of less fundamental mode optical fibre link；The various damage informations that less fundamental mode optical fibre is calculated according to curve, such as Mode Coupling, mode
Dependent loss and difference modes group delay etc. are shown eventually by data acquisition and processing module 5.
The signal generator module 1, as shown in Fig. 2, by single-frequency laser 11, phase-modulator 12, electrooptic modulator 14
It is formed with signal generator 13；The basic process of realization is: driving phase by the sinusoidal modulation signal that signal generator 13 generates
Modulator 12 carries out phase-modulation to the continuous light wave that single-frequency laser 11 exports, and obtains the multi-frequency optical arteries and veins comprising multiple frequency points
Punching；The frequency point quantity in multi-frequency optical pulse is adjusted by the modulation depth and modulating frequency that adjust phase-modulator 12
It is humorous, electrooptic modulator 14 is then driven by the pulse-modulated signal that signal generator 13 generates Parameter adjustable, multi-frequency optical is carried out
Intensity modulated finally obtains the multifrequency light pulse output of Parameter adjustable.
The signal generator 13 is as shown in figure 3, be by the Direct Digital Frequency Synthesizers (Direct based on FPGA
Digital Synthesizer, DDS) realize；The DDS is by phase accumulator, wave memorizer 134, D/A converter 135
It is formed with low-pass filter (LPF) 136；Its specific work process are as follows: frequency control word M is binary-coded phase increment
Value, the input as phase accumulator；Phase accumulator is cascaded by adder 132 and register 133, is used for register
133 output feedback arrives the input terminal of adder 132, realizes cumulative；In each clock pulses fc, phase accumulator is frequency
Control word M131 is accumulated once, and the output of phase accumulator increase accordingly the phase increment of a step-length, phase accumulator it is defeated
It is connected out with the address wire of wave memorizer 134 and tables look-up to wave memorizer 134, will be stored in wave memorizer 134
Signal sampling value find, the output data of wave memorizer is sent to D/A converter 135, by the wave-shape amplitude value of digital form
It is converted into the analog signal of certain frequency, using exporting desired analog waveform after 136 smothing filtering of low-pass filter.It utilizes
The logic unit of FPGA realizes phase accumulator, wave memorizer and peripheral control circuits, is deposited by changing waveform inside FPGA
Wave data in reservoir realizes sinusoidal signal and Parameter adjustable output of pulse signal.
The light path module 2 is as shown in figure 4, be by mode converter 29, pattern demultiplexer 210 and less fundamental mode optical fibre annular
Device 211 forms；Light path module 2 is realized in light path module 2 for connection signal generation module 1 and less fundamental mode optical fibre module 3 to be measured
The excitation of higher order mode and and mode separation, this is the core for realizing multi-mode measurement.The mode converter 29
Multifrequency light pulse signal for exporting signal generator module 1 is converted to the light of corresponding basic mode or higher order mode；Described
Pattern demultiplexer 210 is for coming each modal cutoff of less fundamental mode optical fibre, so as to measure the signal light of each mode；
The less fundamental mode optical fibre circulator 211 supports multiple transmission modes, and less fundamental mode optical fibre circulator has unidirectional transmission property, by signal
Light is oriented to another port from a port.The course of work of the light path module 2 is as follows: multifrequency light pulse signal is through mode
Certain Single port of converter 29 enter mode converter carry out mode conversion, obtain a certain excitation mode, as LP01 mode (or
LP11a or LP11b ...), using the unidirectional transmission property of less fundamental mode optical fibre circulator, the excitation mould is by less fundamental mode optical fibre circulator end
Mouth 1 enters less fundamental mode optical fibre to be measured through port 2, in the back rayleigh scattering light that less fundamental mode optical fibre generates through less fundamental mode optical fibre circulator port
2 return and are exported by port 3, carry out modal cutoff into pattern demultiplexer part.
The less fundamental mode optical fibre module 3 to be measured is mainly made of less fundamental mode optical fibre.The less fundamental mode optical fibre supports multiple modes in parallel
Transmission.It under ideal conditions, is mutually orthogonal between each mode.But during actual transmissions, less fundamental mode optical fibre due to
Manufacture craft is imperfect, causes index distribution uneven；The external interferences such as micro-bend of the optical fiber generated in transmission process make
It is no longer orthogonal between the mode of obtaining, therefore can be coupled between mode.By measuring the less fundamental mode optical fibre of any single mode backwards
The power of Rayleigh scattering with transmission range change curve, the slope of calculated curve can obtain less fundamental mode optical fibre decaying letter
Breath；, can be with acquisition model dependent loss by calculating the decaying of different mode, the group velocity for calculating different mode can obtain difference
Merotype group delay, the power ratio for calculating the back rayleigh scattering between different mode can obtain the mode coupling of less fundamental mode optical fibre
It closes.
The detecting module 4 is used to receive the signal light of less fundamental mode optical fibre module 3 to be measured and signal light is switched to electric signal, visits
The conversion regime for surveying module is divided into direct detection conversion and coherent detection conversion.
The direct detection conversion has the simple advantage of structure, and direct detection conversion is by photodetector receiving light path
The signal light that the pattern demultiplexer 210 of module 2 exports, after signal light is carried out photoelectric conversion by photodetector, by amplification electricity
Road carries out gain tuning, exports electric signal.
The coherent detection conversion has the characteristics that high sensitivity, may be implemented to faint signal light-receiving, by preceding
41,90 ° of frequency mixers 42 of amplifier, balanced detector 43, trsanscondutance amplifier 44, A/D converter 45, dsp processor is set to realize；Light
The backscatter signals light for each mode that the pattern demultiplexer 210 of road module 2 exports after preamplifier amplifies with single-frequency
Local oscillator light carries out 90 ° of mixing in 90 ° of frequency mixers, obtains signal light；It is then passed through balanced detector 43 and carries out photoelectric conversion, and
It is amplified by the power of trsanscondutance amplifier (TIA) 44 pairs of signals, then signal is merged, obtain in-phase signal I [k]
With orthogonal signalling Q [k]；Finally, carrying out digital band pass filtering, Viterbi&Viterbi phase compensation in dsp processor, mend
Digital signal after repaying obtains baseband signal using Digital Down Convert and low-pass filtering treatment, asks the superposition of all baseband signals
It is average, obtain each mode backscatter signals.
The data acquisition and processing module 5 are used to receive the electric signal of the output of detecting module 4, then draw out data wave
Shape, calculates Mode Coupling, difference modes group delay, mode dependent loss and fault location at processing data；Wherein, institute
It states data acquisition and processing module 5 is made of data collecting card and application program；The data collecting card is used for input signal
In the caching of signal deposit data collecting card after carrying out A/D conversion and converting A/D, the application program, which is realized, reads caching
In data, and real-time display, then carry out data analysis.
The application program is independently developed software systems.Using modular design method, including initialization mould
Block, parameter setting module, digital sampling and processing, image display module and data management module；Initialization module is for just
Beginningization hardware device (hardware device includes single-frequency laser and signal generator) and relevant parameter realize the control to hardware device
System, and user can realize human-computer interaction by peripheral hardware software systems；Parameter setting module is for realizing few mould Time Domain Reflectometry
The test parameter of instrument is set, such as light impulse length, average time/number and optical fibre refractivity parameter, and system is by these parameters
It sends hardware device to, realizes the interaction of software and hardware；Data management module uses MySql database to measurement parameter
And receive data and saved and read, facilitate later analysis data；Image display module uses the methods of coordinate transform will
Data are drawn on the screen, can be controlled waveform by equipment such as mouse, keyboards and be shown；Digital sampling and processing and hardware drive
It is dynamic to be closely related, FPGA is transmitted to by the digital signal that A/D converter obtains and carries out DSP data processing and caching, so as to
Read the data in memory buffer in family；Treated, data feeding human-computer interaction interface shows each mode backscattering function
Rate curve, and pass through the interaction property between backscattering power curve calculating mode.
Compared with prior art, advantages of the present invention is as follows:
Few mould time-domain reflectomer according to the present invention can solve the high efficiency of different high-order modes, low-loss excitation and not
Problem is efficiently separated with mode；Solve the Photoelectric Detection and signal processing problems of multichannel weak signal light；Solve multi-mode measurement
Measurement problem；It solves the problems, such as to measure while multiple parameters such as Mode Coupling, difference modes group delay and mode dependent loss.It can
Intelligently to adjust measurement parameter according to different scenes, application range is very extensive, and more scene measurements may be implemented.
Detailed description of the invention
Fig. 1: the structural schematic diagram of few mould optical time domain reflectometer of the present invention；
Fig. 2: signal pulse generates structure chart；
Fig. 3: the structural schematic diagram of the DDS signal generator based on FPGA；
Fig. 4: mode conversion and separation light channel structure figure；
Fig. 5: the structural block diagram of coherent detection converting system；
Fig. 6: 6 mould time-domain reflectomer system block diagrams；
Fig. 7: measurement result figure；
In figure: signal generator module 1, light path module 2, less fundamental mode optical fibre module 3 to be measured, detecting module 4 and data acquisition and
Processing module 5, single-frequency laser 11, phase-modulator 12, signal generator 13, electrooptic modulator 14, frequency control word M131,
Phase accumulator, wave memorizer 134, D/A converter 135 and low-pass filter (LPF) 136,41,90 ° of preamplifier it is mixed
Frequency device 42, balanced detector 43, trsanscondutance amplifier 44, the input port of input port 21, second of A/D converter 45, first
22, third input port 23, k-th of the output port 25, second of input port 24, first output port 26, third
Output port 27, mode converter 29, pattern demultiplexer 210, less fundamental mode optical fibre circulator 211, is answered at k-th of output port 28
With program 111, photon lantern A65, photon lantern B67, less fundamental mode optical fibre link 68 to be measured, direct detection 69, data collecting card
110。
Specific embodiment
The present invention is described in detail with specific example scheme with reference to the accompanying drawing.
Embodiment 1
The present invention establishes few mould time-domain reflectomer of 6 modes, as shown in Figure 6.Few mould time-domain reflectomer uses
Modular design, be divided into signal generator module, light path module, less fundamental mode optical fibre module to be measured, detecting module and data acquisition and
Processing module composition.In this example, signal generator module uses single-frequency laser light source, phase-modulator (PM), electrooptic modulator
(EOM) and FPGA signal generator realizes multifrequency light pulse；Light path module uses photon lantern A, photon lantern B and less fundamental mode optical fibre
The conversion of circulator implementation pattern and separation；Less fundamental mode optical fibre module to be measured is measured using the less fundamental mode optical fibre of 6 mould 6km；Detection
Module realizes the reception to signal using photodetector；Data acquisition and processing module use the application journey of MFC programming development
Sequence realizes the display to signal, and application is divided into parameter setting module, data acquisition module, data processing module and control
Display module.
This example measures 6 mould 6km less fundamental mode optical fibres.6 mode fiber can support LP01, LP11a, LP11b,
Six kinds of transmission modes of LP02, LP21a, LP21b.
In the present embodiment, select 6 mode fibers of Fiberhome Telecommunication Technologies Co., Ltd. as tested optical fiber, surveyed light
Fine length is about 6km, and attenuation coefficient is less than 0.25dB/km (LP01 mode) in 1550nm wave band, the normalization of 1550nm wave band
Cutoff frequency V=4.769 can support the transmission of six kinds of modes of LP01, LP11a, LP11b, LP02, LP21a, LP21b.
Single-frequency laser light source needed for embodiment 1 is to fly rich source 1550nm semiconductor laser light resource module.Light source output weight
Complex frequency is that 1KHz-100KHz is adjustable, and pulse width is that 10ns-1200ns is adjustable, and output pulse power is up to 40mW.At this
In example, repetition rate is set as 4KHz, width sets 100ns, power setting 40mW.Selected phase-modulator is
The phase-modulator of Thorlabs company, model LN66S-FC；Selected electrooptic modulator is the electric light of Thorlabs company
Modulator, model LN56S-FC；Selected FPGA is high-performance AC6102Altera FPGA development board；Selected data are adopted
Truck is the high-speed data acquisition card of Beijing Xing Shuohuachuan Science and Technology Ltd., model PCI-E 9826；Select photon lantern
As mode converter and demultiplexer, photon lantern is all -fiber Six-Mode selectivity multichannel of OLKIN OPTICS company
Multiplexer can support the mode of six modes of LP01, LP11a, LP11b, LP21a, LP21b, LP02 to convert.Select the vast space in Shanghai
3 port less fundamental mode optical fibre circulators of the special 1550nm wave band of Fibre Optical Communication Technology Co., Ltd, can support 6 transmission modes.
In the present embodiment, to six transmission modes of LP01, LP11a, LP11b, LP21a, LP21b, LP02 of 6 mode fibers
Transmission characteristic measured.This example is using LP01 as excitation mode.Specific block diagram is for example as shown in Figure 6.
Connection type is as described below:
Single-frequency laser 11 is connected with phase-modulator 12, and phase-modulator 12 is connected with electrooptic modulator 14.Electric light tune
The single-mode tail fiber of the output tail optical fiber connection photon lantern A65 of device 14 processed, few mould tail optical fiber of photon lantern A65 connect less fundamental mode optical fibre ring
The port 1 of shape device 211, the port 2 of less fundamental mode optical fibre circulator 211 connect less fundamental mode optical fibre link 68 to be measured.Less fundamental mode optical fibre circulator
211 port 3 connects few mould tail optical fiber of photon lantern B67, and 6 single-mode tail fiber output ports of photon lantern B67 connect photoelectricity
6 input ports of detector 69.6 signal input ports of 69 output port of photodetector connection data collecting card 110.
The output port of data collecting card 110 is connected in the bus of computer PCI-E.FPGA13 is connected to the USB jack of computer
On.
The detailed system block diagram of this example is as shown in fig. 6, workflow is as follows:
The frequency point quantity of multifrequency light pulse is set by the parameter setting module of application program first, light impulse length, is put down
The parameters such as equal time/number.Then these parameters are transmitted to laser light source and FPGA by system, the impulse generator realized by FPGA
Output sine and Parameter adjustable electric impulse signal, respectively drive the company that phase-modulator and electrooptic modulator export laser light source
Continuous laser, which is modulated, generates multifrequency light pulse；Multifrequency light pulse signal through photon lantern A carry out spatial model conversion injection to
Less fundamental mode optical fibre is surveyed, and the different mode of less fundamental mode optical fibre back rayleigh scattering light to be measured is effectively separated using photon lantern B,
Then direct detection is carried out to the back-scattering light of each mode, finally to each mode transmission characteristic of less fundamental mode optical fibre and different moulds
Interaction property between formula is analyzed, and final result is shown with waveform and numeric form by the control of application program
Module shows.
This example signal light output is multifrequency light pulse signal.Multi-frequency optical can be by changing pulse frequency point quantity and pulse
Width realizes the measurement of more scenes.The realization principle of multi-frequency optical is as shown in Figure 2.Implementation method are as follows: the Direct Digital based on FGPA
Frequency synthesizer (DDS) generates sinusoidal modulation signal driving phase-modulator and carries out phase to the continuous light wave that single-frequency laser exports
Position modulation, obtains the multi-frequency optical comprising multiple frequency points, then drives Electro-optical Modulation by the electric impulse signal that DDS generates Parameter adjustable
Device carries out intensity modulated to multi-frequency optical, finally obtains the multifrequency light pulse signal of Parameter adjustable.It can be by adjusting phase-modulation
The modulation depth and modulating frequency of device realize the control of pulse intermediate-frequeney point quantity.
The light path module of this example using photon lantern A+ less fundamental mode optical fibre circulator+photon lantern B method, wherein
Photon lantern A is mode converter, and photon lantern B is pattern demultiplexer.Groundwork process are as follows: Input1 is passed through in light pulse
Into photon lantern A, spatial model conversion can occur inside photon lantern A, obtain single excitation mode, utilize less fundamental mode optical fibre
The unidirectional transmission property of circulator, the excitation mode enter few mould to be measured via port 2 by the port 1 of less fundamental mode optical fibre circulator
Optic module.Back rayleigh scattering light is generated in the less fundamental mode optical fibre of testing fiber module, the scattering light is back to port 2 and passes through
The output of port 3 is crossed, and enters photon lantern B and carries out modal cutoff.
This example receives signal using direct detection mode.To every road output signal (LP01, LP11a, LP11b, LP02,
LP21a, LP21b) it is connected in output port (Output1, Output2, Output3, Output4, Output5, Output6)
It can be realized on each port of photodetector.
The data of this example acquire and processing module is made of data collecting card and application program.The input of data collecting card
Port receives the electric signal of photodetector output port, and collected electric signal is AD converted, and is stored in capture card
Caching in.When starting acquisition, application program reads the data in caching, and data are transmitted to the drawing window of application program
Mouthful, the drafting of data waveform is realized using function overloading in drawing window.Data can be transmitted to the mould of data acquisition and processing simultaneously
The data processing section of block realizes the Mode Coupling for calculating less fundamental mode optical fibre, when difference modes group in data processing function module
Prolong and mode dependent loss.And by analysis data, fault location is carried out using two-point method and least square method.It is last these
Information all passes through the list display of application program in main interface.
Fig. 7 gives measurement result figure, is 6 mode LP01 moulds, LP11a mould, LP11b mould, LP02 moulds, LP21a respectively
The back rayleigh scattering power of mould and LP21b mould with transmission range change curve and the wherein mould of LP01 and LP11a mode
Formula coupling ratio curve.The specific value that measurement is shown in list below, give less fundamental mode optical fibre mode coupling constant,
The measurement numerical value of mode dependent loss, there are also the numerical value of fault location for the attenuation value of less fundamental mode optical fibre.Fig. 7 can significantly find out
The metrical information of 6 mould 6km less fundamental mode optical fibres in this example.
Few mould time-domain reflectomer of the present invention is described in detail, above introduction is primarily to be used for
Method and its core concept of the invention are further understood from；At the same time, for those skilled in the art, according to this hair
There will be changes in bright thought, then specific embodiment and application range, in conclusion the content of the present specification should not manage
Solution is limitation of the present invention, in the spirit without departing substantially from the method for the invention and in the case where scope of the claims, to its into
(generation of such as pulse signal, the change of mode converter and demultiplexer type are tested few for capable various obvious changes
The mode quantity of mode fiber, direct detection or coherent detection etc.) all within protection scope of the present invention.
Claims (9)
1. a kind of few mould time-domain reflectomer, which is characterized in that by signal generator module (1), light path module (2), few mould light to be measured
Fiber module (3), detecting module (4) and data acquisition and processing module (5) composition；Wherein, the light path module (2) includes mould
Formula converter, pattern demultiplexer and less fundamental mode optical fibre circulator；Its course of work is as follows:
The signal generator module (1) generates pulse light, and then pulse light is transferred to light path module by optical fiber
(2), pulse light is converted into corresponding single excitation mode light by the mode converter in light path module (2), it is single to swash
It sends out mode light and less fundamental mode optical fibre module (3) to be measured is entered by the less fundamental mode optical fibre circulator in light path module (2)；Few mould light to be measured
The light energy of the single excitation mode of less fundamental mode optical fibre in fiber module (3) can be coupled in other non-excitation modes, excitation mode
Back rayleigh scattering optical signal with non-excitation mode is through less fundamental mode optical fibre circulator meeting return light path module (2)；In light path module
(2) pattern demultiplexer in carries out modal cutoff, obtains corresponding mode, is output to the output port of light path module (2)；So
Light letter is scattered by the back rayleigh scattering of detecting module (4) to the output port of light path module (2) afterwards to detect, then will be visited
Signal after survey is input in data acquisition and processing module (5)；In data acquisition and procession module (5), data are utilized
The data collecting card of acquisition and processing module (5) is acquired data, then reads data, and carry out at denoising to data
Reason draws the data and curves that optical power is converted with transmission range, to obtain the transmission situation of less fundamental mode optical fibre link；According to song
Line computation goes out the various damage informations of less fundamental mode optical fibre, shows eventually by data acquisition and processing module (5).
2. a kind of few mould time-domain reflectomer as described in claim 1, which is characterized in that the signal generator module (1), by list
Frequency laser (11), phase-modulator (12), electrooptic modulator (14) and signal generator (13) composition；The basic process of realization
Be: sinusoidal modulation signal driving phase-modulator (12) generated by signal generator (13) exports single-frequency laser (11)
Continuous light wave carries out phase-modulation, obtains the multifrequency light pulse comprising multiple frequency points；By the tune for adjusting phase-modulator (12)
Depth and modulating frequency processed are tuned the frequency point quantity in multi-frequency optical pulse, then generate ginseng by signal generator (13)
Adjustable pulse-modulated signal driving electrooptic modulator (14) of number, carries out intensity modulated to multi-frequency optical, finally obtains Parameter adjustable
Multifrequency light pulse output.
3. a kind of few mould time-domain reflectomer as claimed in claim 2, which is characterized in that the signal generator (13), be by
What the Direct Digital Frequency Synthesizers based on FPGA were realized；The Direct Digital Frequency Synthesizers are deposited by phase accumulator, waveform
Reservoir (134), D/A converter (135) and low-pass filter (136) composition；Its specific work process are as follows: frequency control word M is
Binary-coded phase increment value, the input as phase accumulator；Phase accumulator is by adder (132) and register
(133) it cascades, for realizing the input terminal of the output feedback of register (133) to adder (132) cumulative；Every
One clock pulses fc, phase accumulator accumulate once frequency control word M (131), and the output of phase accumulator is increase accordingly
The output of the phase increment of one step-length, phase accumulator is connected with the address wire of wave memorizer (134) to wave memorizer
(134) it tables look-up, the signal sampling value being stored in wave memorizer (134) is found, the output data of wave memorizer
D/A converter (135) are sent to, the wave-shape amplitude value of digital form are converted into the analog signal of certain frequency, using low pass
Desired analog waveform is exported after filter (136) smothing filtering.
4. a kind of few mould time-domain reflectomer as described in claim 1, which is characterized in that the light path module (2) is turned by mode
Parallel operation (29), pattern demultiplexer (210) and less fundamental mode optical fibre circulator (211) composition；Light path module (2) is produced for connection signal
Raw module (1) and less fundamental mode optical fibre module (3) to be measured；The mode converter (29) is used to export signal generator module (1)
Multifrequency light pulse signal be converted to the light of corresponding basic mode or higher order mode；The pattern demultiplexer (210) is used for will
The each modal cutoff of less fundamental mode optical fibre comes, so as to measure the signal light of each mode；The less fundamental mode optical fibre circulator
(211) multiple transmission modes are supported, signal light is oriented to another port from a port；The work of the light path module (2)
It is as follows to make process: multifrequency light pulse signal enters mode converter through certain Single port of mode converter (29) and carries out mode turn
It changes, obtains a certain excitation mode, using the unidirectional transmission property of less fundamental mode optical fibre circulator, the excitation mould is by less fundamental mode optical fibre circulator
Port 1 enters less fundamental mode optical fibre to be measured through port 2, in the back rayleigh scattering light that less fundamental mode optical fibre generates through less fundamental mode optical fibre circulator end
Mouth 2 is returned and is exported by port 3, carries out modal cutoff into pattern demultiplexer part.
5. a kind of few mould time-domain reflectomer as described in claim 1, which is characterized in that the detecting module (4) is for receiving
Signal light is simultaneously switched to electric signal by the signal light of less fundamental mode optical fibre module (3) to be measured, and the conversion regime of detecting module is divided into direct spy
Survey conversion and coherent detection conversion.
6. a kind of few mould time-domain reflectomer as claimed in claim 5, which is characterized in that the direct detection conversion is by photoelectricity
The signal light of detector receiving light path module (2) output, after signal light is carried out photoelectric conversion by photodetector, by amplifying circuit
Gain tuning is carried out, electric signal is exported.
7. a kind of few mould time-domain reflectomer as claimed in claim 5, which is characterized in that the coherent detection conversion, by preceding
Set amplifier (41), (900)Frequency mixer (42), balanced detector (43), trsanscondutance amplifier (44), A/D converter (45), at DSP
Device is managed to realize；Light path module (2) output each mode backscatter signals light after preamplifier amplifies with single-frequency local oscillator
Light is (900)(90 are carried out in frequency mixer0)Mixing, obtains signal light；It is then passed through balanced detector (43) and carries out photoelectric conversion,
And the power of signal is amplified by trsanscondutance amplifier (44), then signal is merged, obtains in-phase signal I [k]
With orthogonal signalling Q [k]；Finally, carrying out digital band pass filtering, Viterbi&Viterbi phase compensation in dsp processor, mend
Digital signal after repaying obtains baseband signal using Digital Down Convert and low-pass filtering treatment, asks the superposition of all baseband signals
It is average, obtain each mode backscatter signals.
8. a kind of few mould time-domain reflectomer as described in claim 1, which is characterized in that the data acquisition and processing module
(5), for receive detecting module (4) output electric signal, then draw out data waveform, processing data, calculate Mode Coupling,
Difference modes group delay, mode dependent loss and fault location；Wherein, data acquisition and processing module (5) by
Data collecting card and application program composition；After the data collecting card is used to carry out A/D conversion to input signal and convert A/D
Signal deposit data collecting card caching in, the application program realizes the data read in caching, and real-time display, then
Carry out data analysis.
9. a kind of few mould time-domain reflectomer as claimed in claim 8, which is characterized in that the application program, including initialization
Module, parameter setting module, digital sampling and processing, image display module and data management module；Initialization module is used for
The control of hardware device and relevant parameter realization to hardware device is initialized, and user can realize by peripheral hardware software systems
Human-computer interaction；Parameter setting module sets for realizing the test parameter of few mould time-domain reflectomer, and system transmits these parameters
To hardware device, the interaction of software and hardware is realized；Data management module uses MySql database and to measurement parameter and connects
It receives data to be saved and read, facilitates later analysis data；Image display module uses the methods of coordinate transform for data
It draws on the screen, waveform can be controlled by equipment such as mouse, keyboards and shown；Digital sampling and processing is tight with hardware driving
Close correlation is transmitted to FPGA by the digital signal that A/D converter obtains and carries out DSP data processing and caching, so as to user's reading
Data in access to memory caching；Treated, data feeding human-computer interaction interface shows that each mode backscattering power is bent
Line, and pass through the interaction property between backscattering power curve calculating mode.
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| 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 |
| CN111442789A (en) * | 2020-04-03 | 2020-07-24 | 南京晓庄学院 | Method for improving spatial resolution and measurement accuracy of sensing system based on mode multiplexing |
| CN111565069A (en) * | 2020-04-10 | 2020-08-21 | 东南大学 | Optical fiber enabled optical wireless communication system and method |
| CN111917463A (en) * | 2020-07-11 | 2020-11-10 | 吉林大学 | Embedded few-mode optical time domain reflectometer |
| CN113014313A (en) * | 2019-12-20 | 2021-06-22 | 中国移动通信集团山西有限公司 | Optical time domain reflectometer |
| CN114543973A (en) * | 2022-02-28 | 2022-05-27 | 华中科技大学 | Distributed ultrahigh frequency vibration signal measuring method and optical fiber sensor |
| CN114938241A (en) * | 2022-04-27 | 2022-08-23 | 温州大学 | Spatial mode multiplexing few-mode optical time domain reflectometer and implementation method thereof |
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| 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 |
| CN110071762B (en) * | 2019-04-30 | 2021-04-16 | 吉林大学 | Few-mode optical fiber fault detection method based on high-order mode backward Rayleigh scattering |
| CN113014313A (en) * | 2019-12-20 | 2021-06-22 | 中国移动通信集团山西有限公司 | Optical time domain reflectometer |
| CN111442789A (en) * | 2020-04-03 | 2020-07-24 | 南京晓庄学院 | Method for improving spatial resolution and measurement accuracy of sensing system based on mode multiplexing |
| CN111442789B (en) * | 2020-04-03 | 2022-03-29 | 南京晓庄学院 | Method for improving spatial resolution and measurement accuracy of sensing system based on mode multiplexing |
| CN111565069A (en) * | 2020-04-10 | 2020-08-21 | 东南大学 | Optical fiber enabled optical wireless communication system and method |
| CN111565069B (en) * | 2020-04-10 | 2021-02-09 | 东南大学 | Optical fiber enabled optical wireless communication system and method |
| CN111917463A (en) * | 2020-07-11 | 2020-11-10 | 吉林大学 | Embedded few-mode optical time domain reflectometer |
| CN111917463B (en) * | 2020-07-11 | 2023-01-24 | 吉林大学 | Embedded few-mode optical time domain reflectometer |
| CN114543973A (en) * | 2022-02-28 | 2022-05-27 | 华中科技大学 | Distributed ultrahigh frequency vibration signal measuring method and optical fiber sensor |
| CN114938241A (en) * | 2022-04-27 | 2022-08-23 | 温州大学 | Spatial mode multiplexing few-mode optical time domain reflectometer and implementation method thereof |
| CN114938241B (en) * | 2022-04-27 | 2023-07-18 | 温州大学 | Space mode multiplexing few-mode optical time domain reflectometer and implementation method thereof |
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