CN103401606A - Coherent optical time-domain reflectometer based on detection frequency coding - Google Patents
Coherent optical time-domain reflectometer based on detection frequency coding Download PDFInfo
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- 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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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
- G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
- G01M11/3109—Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR
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Abstract
The invention discloses a coherent optical time-domain reflectometer based on detection frequency coding, which comprises a laser, a first coupler, a frequency coder, a radio-frequency driver, a circulator, an optical interface, an optical filter, a second coupler, a photoelectric detector, a radio-frequency amplifier, a data acquisition module, a signal processing module and a display module. Laser light emitted by the laser passes through the frequency coder for frequency coding to obtain pulses of detection frequency pulse light and filling light which is complementary to the time sequence of the detection frequency pulse light. The frequency of the pulse of the detection frequency pulse light is different from the frequency of the pulse of the filling light. After the respective backward Raleigh scattering signals of the detection frequency pulse light and the filling light in an optical fiber line are fed back, the detection frequency pulse light and the filling light enter the optical filter through the third port of the circulator, the filtered detection light signal is coherent with local oscillator light at the second coupler, then coherent medium-frequency signals are output by the photoelectric detector and finally the medium-frequency signals are acquired and processed to obtain a time-domain curve which reflects the characteristics of the optical fiber line.
Description
Technical field
The invention belongs to the communications field, be specifically related to a kind of Coherent optical time domain reflectometer for optical fiber telecommunications line sign, Identification of events and fault location.
Background technology
The coherent light time domain reflection technology is adopted in monitoring to many relayings extra long distance optical fiber telecommunications line such as trans-oceanic submarine fiber cable usually.the coherent light time domain reflection technology is utilized the laser radar principle, by to optical fiber, injecting detecting optical pulses, and Rayleigh scattering light and/or the catoptrical return time position of locating scattering and/or pip of recording light pulse in optical fiber, the corresponding spatial resolution of measuring of the pulsewidth of light pulse, the two is proportional, such as, the spatial resolution that the detecting optical pulses width of 1 microsecond is corresponding 100 meters, and the pulse period is slightly larger than and surveys light signal two-way time in the line, simultaneously, it utilizes coherence detection by surveying light and local oscillator optical heterodyne, by the power transfer of detectable signal light on the heterodyne intermediate-freuqncy signal, so just can curb most of out-of-band noise by intermediate-freuqncy signal is carried out to narrow-band filtering, thereby promote the dynamic range of measuring.For many relayings extra long distance optical fiber telecommunications line, the circuit longer pulse period of distance is larger, and to obtain high spatial resolution, pulsewidth should be as far as possible little, so the duty ratio of detecting optical pulses is minimum, such as, for the monitoring of 10,000 kilometers long trans-oceanic submarine fiber cables, pulse period is slightly larger than 100 milliseconds, and pulsewidth is usually in 1 microsecond to 100 microsecond scope.Because circuit adopts erbium-doped fiber amplifier as relay amplifier more, the light pulse of low duty ratio will cause transient effect in erbium-doped fiber amplifier, transient effect accumulates and can form the light surge in each erbium-doped fiber amplifier, thereby cause the light pulse gross distortion, erbium-doped fiber amplifier is damaged.
For the inhibition of light surge, usually adopt shift keying technique.It introduces the filling light pulse with detecting optical pulses complementation on sequential, detecting optical pulses and filling light pulse be corresponding laser and pulse modulator separately respectively, recycling coupler or wavelength division multiplexer are combined into the quasi-continuous light in road by the two, and this quasi-continuous luminous energy suppresses the light surge well.In addition, the people such as Evangelides Stephen have proposed a kind of scheme of Coherent optical time domain reflectometer based on the frequency pulse frequency sweep, and applied for world patent, the patent No. is: US20040794174, patent name are " COTDR ARRANGEMENT WITH SWEPT FREQUENCY PULSE GENERATOR FOR AN OPTICAL TRANSMISSION SYSTEM ".The frequency of the frequency pulse that its method relates to saltus step in time but laser power is continuous, thereby the erbium-doped fiber amplifier that continuous laser enters in fibre circuit just can the transient suppression effect be avoided the light surge, but, frequency pulse is frequency sweep, for the relevant intermediate-freuqncy signal that makes to survey light and the generation of local oscillator light is stablized, therefore the local oscillator light frequency is answered corresponding change, in addition, frequency sweep does not change continuity and the laser linewidth of laser, the Brillouin threshold of this continuous light is very low, thereby this peak power that has just limited frequency pulse has limited the dynamic range of measuring.
Summary of the invention
For the deficiencies in the prior art, the present invention proposes a kind of Coherent optical time domain reflectometer based on the look-in frequency coding, it utilizes same light source obtain to survey light and fill light and the constant local oscillator light of frequency, and surveys light frequency and encoded chronologically, thereby promotes speed and the dynamic range of measuring.
A kind of Coherent optical time domain reflectometer based on the look-in frequency coding that the present invention proposes, its improvements are, described Coherent optical time domain reflectometer comprises: laser 1, the first coupler 2, frequency coding device 3, radio driver 4, circulator 5, optical interface 6, optical filter 7, the second coupler 8, photodetector 9, radio frequency amplifier 10, analog-to-digital conversion module 11, signal processing module 12 and display module 13;
The laser that described laser 1 sends is divided into two-way by described the first coupler 2, the described frequency coding device 3 of a road input, and described the second coupler 8 is directly inputted on another road;
Described radio driver 4 produces the described frequency coding device 3 of radio frequency signals drive that frequency changes with sequential, and described frequency coding device 3 modulating the incident lights produce the pulsed light of look-in frequency coding and the filling light frequency pulse of complementation on sequential with it; The first port of described look-in frequency pulsed light and the described circulator 5 of described filling light pulse input, and export from the second port of described circulator 5, through described optical interface 6, be injected into the tested optical fiber communication line;
Described look-in frequency pulsed light and the dorsad Rayleigh scattering signal of described filling light frequency pulse in tested optical fiber return, through the described optical filter 7 of the 3rd port input of described circulator 5;
The detection light signal that described optical filter 7 leaches enters described the second coupler 8 to be mixed with local oscillator light, and the two mixes the intermediate-freuqncy signal that produces and is received and export corresponding intermediate-freuqncy signal by described photodetector 9;
Described intermediate-freuqncy signal is gathered by described analog-to-digital conversion module 11 after described intermediate frequency amplifier 10 amplifies, the transfer of data that collects carries out the data processing for described signal processing module 12, and shows by described display module 13 the optical time domain reflection curve that characterizes the optical fiber telecommunications line dampening information.
Wherein, described Coherent optical time domain reflectometer comprises the scrambler 14 that is arranged between described frequency coding device 3 and circulator 5, be used to suppressing polarization noise.
Wherein, described Coherent optical time domain reflectometer comprises the erbium-doped fiber amplifier 15 that is arranged between described scrambler 14 and circulator 5, be used to promoting the power of look-in frequency pulsed light, and then improves the dynamic range of measuring.
Wherein, described frequency coding device 3 is selected electro-optic phase modulator.
Perhaps, described frequency coding device 3 is selected the electric light intensity modulator.
Wherein, described radio driver 4 is selected AWG (Arbitrary Waveform Generator), for generation of the radiofrequency signal of frequency with the sequential variation.
Wherein, described optical filter 7 is selected fiber grating.
Wherein, described photodetector 9 is selected the balance photodetector, be used to promoting detectivity.
Wherein, described analog-to-digital conversion module 11 is selected data collecting card, for the intermediate-freuqncy signal by simulation, converts digital signal to.
Wherein, described signal processing module 12 comprises fpga chip, for the treatment of digital signal.
Compared with the prior art, beneficial effect of the present invention is:
in the time of the look-in frequency pulse that obtains by the frequency coding mode, do not destroy the continuity of laser power, it does not need to be configured for separately laser and the acousto-optic modulator of filling light with respect to shift keying technique, and with respect to the mode of frequency pulse frequency sweep, the present invention becomes pure-tone pulse into multifrequency, thereby can effectively promote the Brillouin threshold of continuous light, make device can obtain larger measurement dynamic range, in addition, the local oscillator light frequency of the Coherent optical time domain reflectometer that the present invention relates to is constant, thereby reduced the modulation of detection light frequency and controlled difficulty, and be conducive to the acquisition and processing of signal, and, the present invention uses optical filter to leach detectable signal light, thereby can effectively suppress the interference of other light frequency, can further promote the signal to noise ratio of measurement.
The accompanying drawing explanation
Fig. 1 is the structural representation of a kind of Coherent optical time domain reflectometer based on look-in frequency coding of proposing of the present invention.
Fig. 2 is the detecting optical pulses sequence schematic diagram of the frequency pulse coding that proposes of the present invention.
Fig. 3 is the output power spectrum of phase-modulator under single-frequency drives.
Fig. 4 is the optical time domain reflection curve that the look-in frequency of each coding is corresponding.
Fig. 5 is a kind of detective curve that obtains based on the Coherent optical time domain reflectometer of look-in frequency coding that the present invention proposes.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.
A kind of Coherent optical time domain reflectometer based on the look-in frequency coding that the present embodiment provides, it comprises:
Laser 1, survey light be used to providing, fill light and single-frequency local oscillator light;
The first coupler 2, for light splitting;
Circulator 5, for the sending and receiving of light provides passage separately;
Optical interface 6, access for light path;
Optical filter 7, select fiber grating, for the assorted light frequently of filtering, promotes Optical Signal To Noise Ratio;
The second coupler 8, for the coupling of two-way light;
Analog-to-digital conversion module 11, select data collecting card, for converting rf signal to digital signal;
Scrambler 14, be used to making polarisation of light state change at random;
Erbium-doped fiber amplifier 15, be used to promoting luminous power;
Particularly, laser 1 with the first coupler 2, frequency coding device 3, circulator 5 with after optical interface 6 is connected, is connected with optical fiber telecommunications line successively; The first coupler 2 is connected with the second coupler 8 again, and circulator 5 also is connected with the second coupler 8 by optical filter 7.The second coupler 8 is connected with photodetector device 9, radio frequency amplifier 10, analog-to-digital conversion module 11, signal processing module 12 and display module 13 more successively.
Preferably, the present embodiment is in order to suppress polarization noise, between described frequency coding device 3 and circulator 5, added scrambler 14; In order to promote the power of look-in frequency pulsed light, between described scrambler 14 and circulator 5, add erbium-doped fiber amplifier 15, and then improve the dynamic range of measuring.
As described in Figure 1, the laser that laser 1 sends is divided into two-way by the first coupler 2, a road incoming frequency encoder 3, and the second coupler 8 is directly inputted on another road;
Corresponding with the rf modulations spectrum of Fig. 2, frequency coding device 3 produces look-in frequency pulsed light and the filling light pulse of complementation on sequential with it, then, the first port of direct impulse light and filling light pulse access circulator 5, be injected into through optical interface 6 optical fiber telecommunications line that many relayings amplify from the second port output of circulator 5;
Look-in frequency pulsed light and the dorsad Rayleigh scattering signal of filling light pulse in tested optical fiber return, through the 3rd port access optical filter 7 of described circulator 5;
The detection light signal that optical filter 7 leaches enters the second coupler 8 to be mixed with local oscillator light (another road laser that namely branches away from the first coupler 2), the two mixes the intermediate-freuqncy signal that produces and is received and export corresponding medium frequency electric signal by photodetector 9, the intermediate frequency that each look-in frequency is corresponding is respectively Δ f1, Δ f2, Δ f3,, Δ fn, as shown in Figure 4.
intermediate-freuqncy signal is amplified so that analog-to-digital conversion module 11 carries out high-precision analog-to-digital conversion through intermediate frequency amplifier 10, analog-to-digital conversion module 11 optional data capture cards, the transfer of data that collects is carried out the data processing to signal processing module 12, 12 pairs of digital signals of signal processing module are carried out digital band pass filtering to extract respectively each look-in frequency, again thereby each look-in frequency is carried out to the power that Digital Down Convert and digital low-pass filtering finally obtain detectable signal, then, thereby the result of repeatedly measuring is superposeed and reduces the random noise of measuring, like this, optical time domain reflection curve corresponding to each look-in frequency pulse as shown in Figure 4, the signal processing module 12 then detective curve that each look-in frequency pulse is corresponding carries out sequential alignment and stack, its final data show by display module 13, to characterize the optical time domain reflection curve of optical fiber telecommunications line dampening information, as shown in Figure 5.
The present invention compares with similar business machine MW90010A, from same LASER Light Source, just can obtain detecting optical pulses and fill light pulse, and without using separately filling radiant and pulse modulator just can obtain to fill light pulse, and, owing to surveying light frequency, encoding chronologically, each look-in frequency correspondence a detective curve, the result of many detective curve superposed averages can reduce the decline noise of detective curve the dynamic range of promote measuring more rapidly.
Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment, the present invention is had been described in detail, those of ordinary skill in the field are to be understood that: still can modify or be equal to replacement the specific embodiment of the present invention, and do not break away from any modification of spirit and scope of the invention or be equal to replacement, it all should be encompassed in the middle of claim scope of the present invention.
Claims (10)
1. Coherent optical time domain reflectometer based on look-in frequency coding, it is characterized in that, described Coherent optical time domain reflectometer comprises: laser (1), the first coupler (2), frequency coding device (3), radio driver (4), circulator (5), optical interface (6), optical filter (7), the second coupler (8), photodetector (9), radio frequency amplifier (10), analog-to-digital conversion module (11), signal processing module (12) and display module (13);
The laser that described laser (1) sends is divided into two-way by described the first coupler (2), a road input described frequency coding device (3), and described the second coupler (8) is directly inputted on another road;
Described radio driver (4) produces the described frequency coding device of radio frequency signals drive (3) that frequency changes with sequential, and described frequency coding device (3) modulating the incident light produces the pulsed light of look-in frequency coding and the filling light pulse of complementation on sequential with it; The first port of described look-in frequency pulsed light and the described filling light pulse described circulator of input (5), and export from the second port of described circulator (5), through described optical interface (6), be injected into the tested optical fiber communication line;
Described look-in frequency pulsed light and the dorsad Rayleigh scattering signal of described filling light pulse in tested optical fiber return, through the 3rd port input described optical filter (7) of described circulator (5);
The detection light signal that described optical filter (7) leaches enters described the second coupler (8) to be mixed with local oscillator light, and the two mixes the intermediate-freuqncy signal that produces and is received and export corresponding intermediate-freuqncy signal by described photodetector (9);
Described intermediate-freuqncy signal is gathered by described analog-to-digital conversion module (11) after described intermediate frequency amplifier (10) amplifies, the transfer of data that collects carries out the data processing for described signal processing module (12), and shows by described display module (13) the optical time domain reflection curve that characterizes the optical fiber telecommunications line decay characteristics.
2. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described Coherent optical time domain reflectometer comprises the scrambler (14) that is arranged between described frequency coding device (3) and circulator (5), be used to suppressing polarization noise.
3. Coherent optical time domain reflectometer as claimed in claim 2, it is characterized in that, described Coherent optical time domain reflectometer comprises the erbium-doped fiber amplifier (15) that is arranged between described scrambler (14) and circulator (5), for promoting the power of look-in frequency pulsed light, and then improve the dynamic range of measuring.
4. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described frequency coding device (3) is selected electro-optic phase modulator.
5. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described frequency coding device (3) is selected the electric light intensity modulator.
6. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described radio driver (4) is selected AWG (Arbitrary Waveform Generator), for generation of the radiofrequency signal of frequency with the sequential variation.
7. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described optical filter (7) is selected fiber grating.
8. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described photodetector (9) is selected the balance photodetector, be used to promoting detectivity.
9. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described analog-to-digital conversion module (11) is selected data collecting card, for the intermediate-freuqncy signal by simulation, converts digital signal to.
10. Coherent optical time domain reflectometer as claimed in claim 1, is characterized in that, described signal processing module (12) comprises fpga chip, for the treatment of digital signal.
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| CN201310308485.6A CN103401606B (en) | 2013-07-22 | 2013-07-22 | A kind of Coherent optical time domain reflectometer based on look-in frequency coding |
| PCT/CN2014/082580 WO2015010581A1 (en) | 2013-07-22 | 2014-07-21 | Coherent optical time domain reflectometry coded based on detection frequency |
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| CN103837870A (en) * | 2014-03-20 | 2014-06-04 | 华侨大学 | Frequency modulated continuous wave laser radar frequency modulation nonlinear response coefficient measuring method and device |
| CN103954308A (en) * | 2014-05-09 | 2014-07-30 | 南京发艾博光电科技有限公司 | Optical fiber disturbance detection method and device |
| WO2015010581A1 (en) * | 2013-07-22 | 2015-01-29 | 国家电网公司 | Coherent optical time domain reflectometry coded based on detection frequency |
| CN105716638A (en) * | 2016-02-24 | 2016-06-29 | 南京大学 | Novel COTDR detecting device and realizing method based on complementation light generated by optical switch |
| CN106052842A (en) * | 2016-08-05 | 2016-10-26 | 上海交通大学 | Distributed fiber vibration sensing system capable of eliminating declining noises and demodulation method of system |
| CN104344945B (en) * | 2014-11-06 | 2017-02-15 | 无锡联河光子技术有限公司 | Working method for frequency code optical fiber time domain reflectometer |
| CN107171716A (en) * | 2017-05-26 | 2017-09-15 | 武汉邮电科学研究院 | A kind of online link monitoring system and method based on correlative coding |
| CN107990970A (en) * | 2017-11-03 | 2018-05-04 | 上海交通大学 | The method for eliminating the noise that declines in distribution type fiber-optic acoustic systems |
| CN109039438A (en) * | 2018-06-19 | 2018-12-18 | 武汉邮电科学研究院有限公司 | A kind of optical fiber link detection system and method based on digital chirp signal |
| EP3098651B1 (en) * | 2014-05-19 | 2020-06-03 | Shanghai Jiao Tong University | Light pulse compression reflectometer |
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| CN112595492A (en) * | 2020-11-03 | 2021-04-02 | 烽火通信科技股份有限公司 | COTDR method and system for synchronous monitoring of loss and disturbance events |
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| CN103837870A (en) * | 2014-03-20 | 2014-06-04 | 华侨大学 | Frequency modulated continuous wave laser radar frequency modulation nonlinear response coefficient measuring method and device |
| CN103837870B (en) * | 2014-03-20 | 2016-01-20 | 华侨大学 | Continuous Wave with frequency modulation laser radar Nonlinear frequency modulation response coefficient measuring method |
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| 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 |
| WO2021233207A1 (en) * | 2020-05-22 | 2021-11-25 | 华为技术有限公司 | Polarization controller and polarization control method |
| CN111751844A (en) * | 2020-07-07 | 2020-10-09 | 南京红露麟激光雷达科技有限公司 | Coherent laser radar based on frequency domain coding technology |
| CN111751844B (en) * | 2020-07-07 | 2024-02-23 | 南京泰爱信科技有限公司 | Coherent laser radar based on frequency domain coding technology |
| CN112595492A (en) * | 2020-11-03 | 2021-04-02 | 烽火通信科技股份有限公司 | COTDR method and system for synchronous monitoring of loss and disturbance events |
| CN112697181A (en) * | 2020-12-02 | 2021-04-23 | 广东工业大学 | Phase sensitive optical time domain reflection device and method based on frequency modulation |
| CN112883521A (en) * | 2021-01-12 | 2021-06-01 | 中国科学院声学研究所南海研究站 | Seabed photoelectric composite cable external force invasion monitoring system applied to seabed observation network |
| WO2024032251A1 (en) * | 2022-08-12 | 2024-02-15 | 华为技术有限公司 | Otdr and fiber-optic communication system |
Also Published As
| Publication number | Publication date |
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| CN103401606B (en) | 2016-04-20 |
| WO2015010581A1 (en) | 2015-01-29 |
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