CN102412894B - Multifrequency probe light time division multiplexing coherent light time domain reflectometer method and apparatus thereof - Google Patents
Multifrequency probe light time division multiplexing coherent light time domain reflectometer method and apparatus thereof Download PDFInfo
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Abstract
The invention provides a method of a multifrequency probe light time division multiplexing coherent light time domain reflectometer. The method is characterized in that: a detection light pulse being injected into a fiber being detected is multifrequency detection light pulse which generates time division multiplexing by utilizing sequential electric signal synchronization control phase modulator and light pulse modulator modulation; local oscillator light is single-frequency light, and power spectrum of the multifrequency detection light pulse is bilaterally symmetrical relative to local oscillator light frequency; 0 order frequency of the multifrequency detection light pulse is same with the local oscillator light frequency; modulation depth of the phase modulator is larger than 1; a backward scattering and/or reflection signal which the multifrequency light pulse of time division multiplexing is in mixes with the local oscillator light in a coherent detection module, both side are coherent and an intermediate frequency signal of time division multiplexing is output by a photoelectric detector; an intermediate frequency signal processing module amplifies an intermediate frequency signal of time division multiplexing detected by coherent detection, according to a characteristic of the intermediate frequency signal, a needed band pass filter is selected, the intermediate frequency signal is filtered, a subsequent circuit carries out real-time processing on a plurality of paths of intermediate frequency signals, and information of the fiber being detected is displayed.
Description
Technical field:
The present invention relates to a kind of for characterizing and fault location optical fiber in optical communication line, in particular for the Coherent optical time domain reflectometer of long distance, the health monitoring of many relayings amplification submarine communication cable.
Background technology:
At present, commercial coherent light time domain reflection (COTDR) instrument all uses single mode narrow linewidth detecting optical pulses, the signal of telecommunication that coherent detection produces is single intermediate-freuqncy signal, by detecting the power of this intermediate-freuqncy signal over time, can obtain the health status of fibre circuit.Under specific pulsewidth condition, its dynamic range can be promoted by the average time increasing pulse peak power or increase data, but peak power is subject to the restriction of fiber nonlinear effect.Due to the Photoelectric Signal Processing module of commercial system, be only process an intermediate-freuqncy signal, like this, for the monitoring of the optical cable communication line of long distance, the trans-oceanic extra large cable of such as 12000 kilometers, system measurement time then can reach a few hours.Because COTDR system looks light uses live width to be less than the LASER Light Source of 10kHz, the flashlight which results between the Rayleigh scattering unit of detection light in tested optical fiber has extremely strong coherence, thus causes coherent rayleigh noise.Coherent rayleigh noise can cause the big ups and downs of detective curve, thus the identification of impact to optical communication line case point.For eliminating coherent rayleigh noise and increasing the dynamic range measured, the most frequently used way is exactly increase to measure and average number of times, and the detective curve of COTDR is generally 2
16secondary measurement result average, reaches 2 sometimes
18secondary or higher.
The performance evaluation of COTDR has three important parameters: dynamic range, spatial resolution and Measuring Time.The lifting of dynamic range realizes mainly through promoting detection of optical power and increase measurement and average number of times.But due to the restriction of the particularly stimulated Brillouin scattering of the nonlinear effect in optical fiber, inciding detection of optical power in tested optical fiber should lower than excited Brillouin threshold value, therefore the lifting of Dynamic Range is restricted.The spatial resolution measured, mainly by the restriction of detecting optical pulses width, shortens detecting optical pulses width with room for promotion resolution, but can reduce the dynamic range of measurement.By the mode of pulse code, measurement can be made to have large dynamic range and high spatial resolution, but this can increase the time of system signal process sharp simultaneously.In view of above-mentioned many restrictions, we are placed on the key promoting COTDR systematic function increases on measurement and average number of times.Obviously, commercial at present COTDR system increases measurement and average time can only realize by increasing the time of measuring.Want not to sacrifice the measurement effect that Measuring Time obtains for cost, only way is the measuring speed of elevator system.
Experimental report was had in 1996 about the research Japan NTT company Masatoyo Sumida promoting COTDR systematic survey speed.It is the frequency utilizing the Injection Current controlling distributed Blatt reflective formula (DBR) laser to change detection light, is obtained the detecting optical pulses sequence of different frequency by sequencing control.Detection light is essentially frequency pulse, and namely detection of optical power is constant and Time Continuous, but its frequency is then time-discrete.The backscattering of detection light frequency pulse in tested optical fiber and/or reflected signal are concerned with from the local oscillator light of single-frequency and produce multiple different intermediate-freuqncy signal, a corresponding drive test amount of intermediate-freuqncy signal, curve corresponding to multichannel intermediate-freuqncy signal finally synthesizes a road, and measuring speed so just can be made to be multiplied.So, the Photoelectric Signal Processing module of the program, after multiple bandpass filtering, parallel data processing, and then synthesize a road signal output by accumulator.Experimental result shows, the method can reduce the decline noise of detective curve rapidly, promotes signal to noise ratio.But can only there is a frequency in the method detection light each moment, need extra circuit design to the control of laser, the impact of the controlled-precision circuit hardware of control and the performance of laser own is very large.In addition, the local oscillator light of the program appears at the last of a pulse train cycle, therefore, certainly leads to the blind area of bringing because of design defect.
Summary of the invention:
The present invention seeks to propose multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer method and apparatus, especially propose to reduce quickly the decline noise of detective curve and promote the dynamic range measured, and the method and apparatus of multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer that measuring speed improves greatly.Described technical scheme is as follows:
The method of multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer, the detecting optical pulses be injected in tested optical fiber is time-multiplexed multifrequency detecting optical pulses, and sequential signal of telecommunication Synchronization Control phase-modulator and light pulse modulators modulate can be utilized to produce time-multiplexed multifrequency detecting optical pulses; Local oscillator light is single-frequency laser, and the power spectrum of multifrequency detecting optical pulses is symmetrical relative to the frequency both sides of local oscillator light; 0 order frequency of the time-multiplexed multifrequency detecting optical pulses utilizing sequential signal of telecommunication Synchronization Control phase-modulator and light pulse modulator to produce is identical with local oscillator light frequency; The modulation depth of phase-modulator is greater than 1; Time-multiplexed multi-frequency optical pulse backscattering and/or reflected signal mix in coherent detection module with local oscillator light, the two phase dry doubling exports time-multiplexed intermediate-freuqncy signal by photodetector; IF signal processing module amplifies the time-multiplexed intermediate-freuqncy signal that coherent detection obtains, and according to the feature of intermediate-freuqncy signal, the band pass filter needed for selection, leaches intermediate-freuqncy signal, and subsequent conditioning circuit processes in real time to multichannel intermediate-freuqncy signal, display tested optical fiber information; Or directly use the method for Digital Signal Processing extract the power of intermediate-freuqncy signal and do sequential alignment, display display tested optical fiber detective curve.
To the process of time-multiplexed intermediate-freuqncy signal, can be realized by hardware circuit; Treatment step comprises amplification intermediate-freuqncy signal, deliver to each filter unit again and leach each intermediate-freuqncy signal, then respectively analog-to-digital conversion, Digital Down Convert are being carried out to each intermediate frequency and extracting intermediate-freuqncy signal power, then sequential alignment is carried out to the power of each intermediate-freuqncy signal, superpose again, be averaging, finally show detective curve.
To the process of time-multiplexed intermediate-freuqncy signal, can be realized by software approach; Treatment step comprise utilize data collecting card gather intermediate-freuqncy signal, again digital band pass filtering is done to the data gathered and leach each intermediate-freuqncy signal, then respectively Digital Down Convert and low-pass filtering are being carried out to extract each intermediate-freuqncy signal power to each intermediate frequency, then sequential alignment is carried out to the power of each intermediate-freuqncy signal, superpose again, be averaging, finally show detective curve.The driving voltage of phase-modulator makes its modulation depth be 2.405
A device for multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer, described device comprises:
Light source module, light source is provided with two-way and exports, and a road detects optical module to multifrequency, and a road is single-frequency local oscillator light;
Multifrequency detection optical module, connects light source module, utilizes signal of telecommunication control phase modulator and the light pulse modulator simultaneously with sequential organization, thus produces time division multiplexing multifrequency detecting optical pulses;
Coherent detection module, multifrequency detection optical module outputs to the backscattering of tested optical fiber and/or reflected signal mixes in coherent detection module with single-frequency local oscillator light, realize to multifrequency detecting optical pulses in tested optical fiber with the coherent detection of local oscillator light, thus obtain time-multiplexed multiple intermediate-freuqncy signal and export;
IF signal processing module, connects and amplifies coherent detection module intermediate-freuqncy signal, then the feature of the intermediate-freuqncy signal obtained according to coherent detection, leaches required intermediate-freuqncy signal, process intermediate-freuqncy signal the display information relevant with tested optical fiber.
In multifrequency detection optical module, the signal of telecommunication with sequential organization changes the modulating frequency of phase-modulator chronologically, and the generation of Synchronization Control light pulse modulator pulses, the time division multiplexing detecting optical pulses sequence that light pulse modulator is exported within the same pulse period produces under out of phase modulators modulate frequency;
In light source module, single-frequency laser is divided into two-way through coupler, and a road enters phase-modulator, and produce multifrequency detection light through phase modulator modulation, a road is used as single-frequency local oscillator light;
In multifrequency detection optical module, electrooptic modulator selected by light pulse modulator, and controlled by the pulse electrical signal with sequential organization;
In light source module, single-frequency laser is divided into two-way through coupler, and a road enters phase-modulator, and produce multifrequency detection light through phase modulator modulation, a road is used as single-frequency local oscillator light;
In multifrequency detection optical module, acousto-optic modulator selected by light pulse modulator, and controlled by the pulse electrical signal with sequential organization;
In coherent detection module, select the acousto-optic modulator with identical shift frequency effect in local oscillator light light path, and make it be operated in continuous mode;
In IF signal processing module, IF signal processing can use software approach to realize, detailed process comprises successively: data acquisition, digital band pass filtering, Digital Down Convert and low-pass filtering, and signal sequence adjusts, signal power is sued for peace and on average, finally show detective curve;
In IF signal processing module, the timely ordered pair of extraction that IF signal processing can use analog filter group and hardware circuit to realize intermediate-freuqncy signal power is answered, and finally shows detective curve.
The invention has the beneficial effects as follows: with commercialization detect compared with the Coherent optical time domain reflectometer of light based on single-frequency, the present invention can reduce the decline noise of detective curve quickly and promote the dynamic range measured, and measuring speed improves greatly.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the present invention is further described.
Fig. 1 is a kind of method schematic diagram of the multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer that the present invention relates to.
Fig. 2 is the method schematic diagram that the multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer time division multiplexing multifrequency detecting optical pulses that the present invention relates to produces.
Fig. 3 is the time division multiplexing multifrequency detecting optical pulses schematic diagram that the multifrequency that the present invention relates to detects in the Optical Time Division Multiplexing pulse period of Coherent optical time domain reflectometer.
Fig. 4 is the multifrequency detection of optical power spectrum schematic diagram exported in the multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer phase-modulator a certain moment that the present invention relates to.
Fig. 5 is a kind of structure chart of multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer device that the present invention relates to.
Fig. 6 is that the backscattering of time division multiplexing detecting optical pulses in tested optical fiber and/or reflected signal and single-frequency local oscillator light are concerned with and produce the schematic diagram of intermediate-freuqncy signal.
Fig. 7 is a kind of structure chart based on software engineering of the multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer IF signal processing module that the present invention relates to.
Fig. 8 be multifrequency involved in the present invention detection Optical Time Division Multiplexing Coherent optical time domain reflectometer IF signal processing module based on a kind of structure chart of hardware technology.
Fig. 9 is the detective curve schematic diagram of detective curve corresponding to each intermediate-freuqncy signal time-multiplexed that the present invention relates to and final gained.
Figure 10 is the schematic diagram that filling light of the present invention and time-multiplexed detecting optical pulses sequence form quasi-continuous light.
Figure 11 is that structure shown in Fig. 5 of the present invention uses filling light and detecting optical pulses complementation to form the schematic diagram of quasi-continuous light.
Figure 12 is a kind of schematic diagram adopting acousto-optic modulator to produce detecting optical pulses in structure shown in Fig. 5 of the present invention.
1. single-frequency laser light sources in figure; 2. beam splitter; 3. phase-modulator; 4. image intensifer; 5. light pulse modulator; 6. circulator; 7. scrambler; 8. optical interface; 9.X type three-dB coupler; 10. photodetector; 11. electric amplifiers; 12. multichannel band-pass filter groups; 13. data acquisition units; 14. Digital Down Convert unit; 15. low-pass filter units; 16. intermediate-freuqncy signal synthesis and real unit; 17. fill radiant; 18. acousto-optic modulators; 19. wavelength division multiplexers; 101. light source module; 102. time division multiplexing detection optical modules; 103. coherent detection modules; 104. IF signal processing modules; 200. monochromatic sources; 201. time division multiplexing multifrequency detecting optical pulses; 202. backscatterings and/or reflected signal; 203. coherent detection; 204. IF signal processing.
Embodiment
Embodiment 1
See Fig. 1, the method for a kind of multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer that the embodiment of the present invention provides, the method detailed content is as follows:
200: the laser that single-frequency laser light source sends is divided into two-way through beam splitter, a road produces multi-frequency optical through phase modulator modulation, and another road is used as single-frequency local oscillator light;
201: the modulation depth of phase-modulator is greater than 1, utilize sequential signal of telecommunication Synchronization Control phase-modulator and light pulse modulator, produce time division multiplexing detecting optical pulses; The control procedure of the sequential signal of telecommunication as shown in Figure 2, the radio-frequency driven of phase-modulator produces the frequency pulse of sequential organization under the triggering of the sequential signal of telecommunication, as shown in Figure 3, this frequency pulse drives phase-modulation to remove to export the multifrequency detection light with sequential organization, meanwhile, the sequential signal of telecommunication drives optical pulse generator to produce multifrequency detecting optical pulses.Multifrequency detecting optical pulses is at certain frequency pulse f
idrive the power spectrum of the lower multifrequency detecting optical pulses produced as shown in Figure 4.
202: collect the backscattering of time-multiplexed multifrequency detecting optical pulses in tested optical fiber and/or reflected signal;
203: the backscattering of time-multiplexed multifrequency detecting optical pulses in tested optical fiber and/or reflected signal through mixing, produce multiple relevant intermediate-freuqncy signal with local oscillator light, and by photoelectric detector;
204: amplify relevant intermediate-freuqncy signal, then leach each intermediate-freuqncy signal, the feature of intermediate-freuqncy signal as shown in Figure 6; These intermediate-freuqncy signals of real-time process also synthesize a road, and finally show detective curve, this process as shown in Figure 9.
Embodiment 2
See Fig. 5, embodiments provide a kind of method and apparatus of multi-frequency detecting-light coherent light time-domain reflectometer, the method and device detailed content as follows:
The light that single-frequency laser light source 1 sends is divided into two bundles through the beam splitter 2 of 90: 10, one end Access Probe light light path of high-power output, the driving voltage arranging phase-modulator 3 makes its modulation depth be 2.405, the power of 0 order frequency the power spectrum of multi-frequency optical is exported so minimum from phase-modulator 3, and most power concentration is on ± 1 rank and ± 2 order frequencies, its power spectrum structure as shown in Figure 4;
The multifrequency detection light that phase-modulator 3 exports, again through image intensifer 4, as erbium-doped fiber amplifier amplifies the power to promote detection light, then becomes detecting optical pulses through electrooptic modulator 5;
Phase-modulator 3 and electrooptic modulator 5 are controlled by the sequential signal of telecommunication.As produced the sequential signal of telecommunication with pulse signal generator, the triggering of pulse signal generator connects AWG (Arbitrary Waveform Generator), make AWG (Arbitrary Waveform Generator) produce as shown in Figure 3 there is Time Division Multiplexing Fabric frequency pulse, with drive phase-modulator export time-multiplexed multifrequency detection light.Phase-modulator is at driving frequency f
ithe power spectrum of the multifrequency detection light of lower output as shown in Figure 4.In addition, the electric impulse signal that pulse signal generator exports drives electrooptic modulator 5, to produce time-multiplexed multifrequency detecting optical pulses;
The frequency of local oscillator light is identical with 0 order frequency of multifrequency detecting optical pulses, the backscattering of some like this multifrequency detecting optical pulses in tested optical fiber and/or reflected signal ± 1 rank and ± 2 order frequencies are concerned with local oscillator light and only produce two intermediate-freuqncy signals, as shown in Figure 6.Because detecting optical pulses is time-multiplexed, then it will produce time-multiplexed multiple intermediate-freuqncy signal.
Detecting optical pulses is disturbed 6 to the rear through scrambler, then injects tested optical fiber through circulator 7 with through optical interface 8;
The back rayleigh scattering light of detecting optical pulses in tested optical fiber mixes with the X-coupler 9 of single-frequency local oscillator light at 3dB, and the two relevant generation has multiple intermediate-freuqncy signals of sequential organization, and exports from photodetector 10;
Software approach can be used to the real-time process of intermediate-freuqncy signal, as shown in Figure 7, intermediate-freuqncy signal is after electric amplifier 11 amplifies, most of out-of-band noise is leached by multichannel band pass filter, the bandwidth of filter is not less than the inverse of detecting optical pulses width, then gathers the signal of telecommunication by data collecting card and is used as Digital Signal Processing;
Digital signal processing comprises and utilizes multichannel digital band-pass filter group to leach and time-multiplexed each road intermediate-freuqncy signal, then Digital Down Convert and low-pass filtering is carried out to extract the power of intermediate-freuqncy signal, adjust finally by sequential, summation and average calculating operation obtain final detective curve, and this process as shown in Figure 9.
Hardware approach can be used to realize the real-time process of intermediate-freuqncy signal, as shown in Figure 8, the intermediate-freuqncy signal that photodetector 10 exports, each hardware processing element is transported to after electric amplifier 11 amplifies, realize filtering, analog-to-digital conversion, Digital Down Convert, low-pass filtering and timing modulation and data summation with average by hardware circuit, finally show detective curve.
Light source module of the present invention, for detection light provides initial light source, also for coherent detection module provides local oscillator light, light source module selects single frequency laser;
Time division multiplexing detection optical module, connects light source module, utilizes sequential signal of telecommunication Synchronization Control phase-modulator and light pulse modulator to produce the multifrequency detecting optical pulses with sequential organization, i.e. time-multiplexed multifrequency detecting optical pulses;
Coherent detection module, connects light source module and time division multiplexing detection optical module, the backscattering of time-multiplexed detecting optical pulses in tested optical fiber and/or reflected signal mix with local oscillator light, the two time-multiplexed intermediate-freuqncy signal of generation that is concerned with;
IF signal processing module, connect coherent detection module, amplify the time-multiplexed intermediate-freuqncy signal exported from coherent detection module, utilize the separation of multiple filter realization to multiple intermediate-freuqncy signal, then in each intermediate-freuqncy signal of parallel processing, finally obtain detective curve and show, Digital Signal Processing and software approach also can be utilized to realize this process.
Wherein, described device also comprises: time division multiplexing detection optical module, after time division multiplexing detecting optical pulses sends, sends and fill light pulse, make the two take the whole pulse period, namely form quasi-continuous light.
Embodiment 3
See Figure 12, the device of the another kind of multi-frequency detecting-light coherent light time-domain reflectometer that the embodiment of the present invention provides, this device is substantially identical with embodiment 2 structure, and just, in system, light pulse modulator uses acousto-optic modulator 18.Because acousto-optic modulator 18 has shift frequency effect, therefore, also an acousto-optic modulator 18 with identical frequency shift property is used in coherent detection module local oscillator light light path, but it works, continuous light pattern more only plays shift frequency effect, so 0 order frequency in multifrequency detecting optical pulses is identical with the frequency of local oscillator light.So just can ensure that result as shown in Figure 6 appears in relevant intermediate-freuqncy signal.
Embodiment 4
The single-frequency laser that external cavity semiconductor laser 1 sends is divided into two bundles through the beam splitter 2 of 90: 10, and high-power a branch of connection phase-modulator 3 is for generation of multifrequency detection light, lower powered a branch of as local oscillator light, connects one end of the three-dB coupler 9 of X-type.Pulse signal generator is utilized to produce the sequential signal of telecommunication.The trigger end of pulse signal generator connects AWG (Arbitrary Waveform Generator), arranges the sequential of the radiofrequency signal that AWG (Arbitrary Waveform Generator) exports, makes it under triggering level effect, produce the frequency pulse with sequential organization, thus drives phase-modulator 3.The pulse duration of frequency pulse is 1 microsecond, frequency is followed successively by 15MHZ, 16MHz, 17MHz, 18MHz, 19MHz, totally 5. simultaneously, to utilize pulse signal generator to produce pulsewidth be cycle of 1 microsecond is the electric pulse of 1.2 milliseconds, and to produce pulsewidth to drive electrooptic modulator 5 be 1 microsecond periodic is the light pulse of 1.2 milliseconds.The time-multiplexed multifrequency detection light that phase-modulator 3 exports is amplified by erbium-doped fiber amplifier 4.
Detecting optical pulses is disturbed to the rear through scrambler 6, then through circulator 7 be injected into through optical interface 8 in the tested optical fiber of 100 kilometers long;
The back rayleigh scattering light of detecting optical pulses in tested optical fiber mixes with the X-coupler 9 of single-frequency local oscillator light at 3dB, and the two relevant generation has multiple intermediate-freuqncy signals of sequential organization, and is received by photodetector 10; Relevant process produces 10 intermediate-freuqncy signals, and their frequency is respectively 15MHz, 30MHz, 16MHz, 32MHz, 17MHz, 34MHz, 18MHz, 36MHz, 19MHz, 38MHz.
Zhe 10 tunnel intermediate-freuqncy signal is exported from photodetector 10, after electric amplifier 11 amplifies, deliver to each signal processing unit respectively again, Dui Zhe 10 tunnel intermediate-freuqncy signal carries out bandpass filtering, Digital Down Convert and low-pass filtering to complete the extraction of Duo Ge road intermediate-freuqncy signal power respectively, thus obtain detective curve, as shown in Figure 9.Wherein, the bandwidth of band pass filter 12 should be not less than the inverse of detecting optical pulses width, and for the detecting optical pulses width of 1 microsecond, the bandwidth of band pass filter can be taken as 1MHz.Because intermediate-freuqncy signal is also time-multiplexed, therefore need to carry out after sequential alignment summation again and average to the data of detective curve corresponding to each road intermediate-freuqncy signal, thus obtain final detective curve.
Claims (4)
1. the method for multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer execution, it is characterized in that the detecting optical pulses be injected in tested optical fiber is time-multiplexed multifrequency detecting optical pulses, utilize sequential signal of telecommunication Synchronization Control phase-modulator and light pulse modulators modulate to produce time-multiplexed multifrequency detecting optical pulses; Local oscillator light is single-frequency laser, and the power spectrum of multifrequency detecting optical pulses is symmetrical relative to the frequency both sides of local oscillator light; 0 order frequency of the time-multiplexed multifrequency detecting optical pulses utilizing sequential signal of telecommunication Synchronization Control phase-modulator and light pulse modulator to produce is identical with local oscillator light frequency; The modulation depth of phase-modulator is greater than 1; Time-multiplexed multi-frequency optical pulse mixes with local oscillator light at backscattering and/or reflected signal in coherent detection module, and the two phase dry doubling exports time-multiplexed intermediate-freuqncy signal by photodetector; IF signal processing module amplifies the time-multiplexed intermediate-freuqncy signal that coherent detection obtains, according to the feature of intermediate-freuqncy signal, the band pass filter needed for selection, leaches intermediate-freuqncy signal, subsequent conditioning circuit processes in real time to multichannel intermediate-freuqncy signal, display tested optical fiber detective curve; Or directly use the method for Digital Signal Processing extract the power of intermediate-freuqncy signal and do sequential alignment, display tested optical fiber detective curve.
2. the method for multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer according to claim 1 execution, is characterized in that the process to time-multiplexed intermediate-freuqncy signal, realizes by hardware circuit; Treatment step comprises amplification intermediate-freuqncy signal, deliver to each filter unit again and leach each intermediate-freuqncy signal, and then respectively analog-to-digital conversion, Digital Down Convert carried out to each intermediate frequency and extract intermediate-freuqncy signal power, then sequential alignment is carried out to the power of each intermediate-freuqncy signal, superpose again, be averaging, finally show detective curve.
3. the method for multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer according to claim 1 execution, be is characterized in that the process to time-multiplexed intermediate-freuqncy signal, is realized by software approach; Treatment step comprise utilize data collecting card gather intermediate-freuqncy signal, again digital band pass filtering is done to the data gathered and leach each intermediate-freuqncy signal, and then respectively Digital Down Convert and low-pass filtering are carried out to extract each intermediate-freuqncy signal power to each intermediate frequency, then sequential alignment is carried out to the power of each intermediate-freuqncy signal, superpose again, be averaging, finally show detective curve.
4. a multifrequency detection Optical Time Division Multiplexing Coherent optical time domain reflectometer, is characterized in that comprising:
Light source module, single-frequency laser is divided into two-way through coupler, and a road enters phase-modulator, and produce multifrequency detection light through phase modulator modulation, a road is used as single-frequency local oscillator light;
Time division multiplexing detection optical module, connects light source module, utilizes signal of telecommunication control phase modulator and the light pulse modulator simultaneously with sequential organization, thus produces time division multiplexing multifrequency detecting optical pulses; 0 order frequency of the time-multiplexed multifrequency detecting optical pulses utilizing sequential signal of telecommunication Synchronization Control phase-modulator and light pulse modulator to produce is identical with local oscillator light frequency; The signal of telecommunication with sequential organization changes the modulating frequency of phase-modulator chronologically, and the generation of Synchronization Control light pulse modulator pulses, the time division multiplexing detecting optical pulses sequence that light pulse modulator is exported within the same pulse period produces under out of phase modulators modulate frequency;
Acousto-optic modulator selected by phase-modulator, and controlled by the pulse electrical signal with sequential organization;
Electrooptic modulator selected by light pulse modulator, and controlled by the pulse electrical signal with sequential organization;
Coherent detection module, multifrequency detection light output mixes to the backscattering of tested optical fiber and/or reflected signal with single-frequency local oscillator light in coherent detection module, realize to multifrequency detecting optical pulses in tested optical fiber with the coherent detection of local oscillator light, thus obtain time-multiplexed multiple intermediate-freuqncy signal and export;
In coherent detection module, select the acousto-optic modulator with identical shift frequency effect in local oscillator light light path, and make it be operated in continuous mode;
IF signal processing module, connects and amplifies coherent detection module intermediate-freuqncy signal, then the feature of the intermediate-freuqncy signal obtained according to coherent detection, leaches required intermediate-freuqncy signal, and process intermediate-freuqncy signal also shows tested optical fiber detective curve.
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