CN102170307A - Dynamic Frequency Offset Correction Method and Coherent Optical Time Domain Reflectometer System - Google Patents

Abstract

The invention discloses a dynamic frequency deviation correction method and a coherent optical time domain reflectometer system, wherein the method comprises the following steps: performing light splitting processing on laser output by a laser to generate detection light and control light; inputting control light into MZI for interference, and performing photoelectric conversion on the interfered control light to obtain a first electric signal; controlling the optical path difference of optical signals transmitted on two arms of the MZI according to a first electric signal, so that the optical path difference is one fourth of the laser wavelength; calculating the deviation degree of the actual central frequency of the laser relative to the standard value of the central frequency of the laser according to the first electric signal; and correspondingly compensating according to the deviation degree. Dividing laser output by a laser into detection light and control light, and calculating the deviation degree of the actual central frequency of the laser relative to the standard value of the central frequency of the laser according to the control light; and performing corresponding correction control on the laser output by the laser according to the deviation degree, and improving the optical coherence detection performance.

Description

Dynamic Frequency Offset Correction Method and Coherent Optical Time Domain Reflectometer System

technical field

The invention relates to the technical field of optical fiber communication, in particular to a dynamic frequency offset correction method and a coherent optical time domain reflectometer system.

Background technique

With the development of optical fiber communication technology, the optical fiberization of the network has always been one of the main trends in network development. The submarine optical cable is a very important part of the network optical fiber, and the real-time monitoring of the long-distance submarine optical cable has also become an important content of network maintenance.

When testing submarine optical cables, a coherence optical time-domain reflectometer (hereinafter referred to as COTDR) is used for testing. In the COTDR system, due to the need to detect ultra-long-distance laser reflection signals, the laser is in the Frequency drift during the measurement will affect the receiver receiving frequency. In order not to lose the signal, it is necessary to expand the receiving passband of the receiver, which will lead to the influx of noise power, resulting in a decrease in the signal-to-noise ratio of the receiving system. Therefore, the detection performance of COTDR will be limited by the frequency stability of the light source. In traditional solutions, lasers with high frequency stability are often used as light sources, which will greatly increase the cost of communication systems with COTDR.

In the solution of the prior art, it is monitored whether the frequency of the measuring laser deviates from the center frequency, and if there is a deviation, the light source is adjusted. However, the prior art has the following disadvantages: since the COTDR has high requirements on the line width of the light source, the adjustment of the frequency of the light source will affect the line width of the light source, thus affecting the detection effect.

Contents of the invention

The invention provides a dynamic frequency offset correction method and a coherent optical time domain reflectometer system, which are used to improve the detection performance of coherent light, reduce the requirement on the line width of a light source, and improve the effect of frequency offset correction.

An embodiment of the present invention provides a dynamic frequency offset correction method, which is applied in a coherent optical time domain reflectometer system to eliminate the influence of laser frequency drift, including:

performing spectroscopic processing on the laser output from the laser to generate probe light and control light;

Input the control light into the Mach-Zehnder interferometer MZI for interference to obtain the control light after interference;

performing photoelectric conversion on the interfering control light to obtain a first electrical signal;

controlling the optical path difference of the optical signals transmitted on the two arms of the MZI according to the first electrical signal, so that the optical path difference is a quarter of the wavelength of the laser light;

calculating a degree of deviation of the actual center frequency of the laser relative to a standard value of the center frequency of the laser according to the first electrical signal;

Corresponding compensation is performed according to the degree of deviation, so that the actual center frequency of the baseband signal obtained after receiving the optical signal transmitted back from the downlink converges to the standard value of the center frequency of the baseband signal.

An embodiment of the present invention also provides a coherent optical time domain reflectometer system, including: a laser, a first beam splitter, a Mach-Zehnder interferometer MZI, a photodetector, a first controller, a second controller, a modulator and modulation source;

The laser is used to generate laser light;

The first beam splitter is used to split the laser light to obtain detection light and control light;

The MZI is configured to interfere with the input control light to obtain the control light after interference;

The photodetector is used to photoelectrically convert the interfering control light to obtain a first electrical signal;

The first controller is configured to generate a control signal according to the first electrical signal to control the MZI so that the optical path difference of the optical signals transmitted on the two arms of the MZI is the wavelength of the laser a quarter of

The modulator is configured to modulate the probe light to generate a probe light pulse;

The modulation source is used to generate a modulation control signal to control the modulator to modulate the detection light;

The second controller is configured to calculate the degree of deviation of the actual center frequency of the laser relative to the standard value of the center frequency of the laser according to the first electrical signal, and generate a control based on the degree of deviation signal to control the modulation source to output the output frequency of the modulation control signal, so that the actual center frequency of the detection light pulse generated by the modulation of the modulator converges to the standard value of the center frequency of the laser.

An embodiment of the present invention also provides a coherent optical time domain reflectometer system, the system includes: a laser, a first beam splitter, a Mach-Zehnder interferometer MZI, a photodetector, a first controller, and a second controller, Modulators, modulation sources, coherent receivers, mixers and oscillators;

The laser is used to generate laser light;

The first beam splitter is used to split the laser light to obtain detection light and control light;

The MZI is configured to interfere with the input control light to obtain the control light after interference;

The photodetector is used to photoelectrically convert the interfering control light to obtain a first electrical signal;

The first controller is configured to generate a control signal according to the first electrical signal to control the MZI so that the optical path difference of the optical signals transmitted on the two arms of the MZI is the wavelength of the laser a quarter of

The modulator is configured to modulate the probe light to generate a probe light pulse;

The modulation source is used to generate a modulation control signal to control the modulator to modulate the detection light;

The coherent receiver is configured to receive an optical signal transmitted back from the downlink, and perform coherent processing on the optical signal transmitted back from the downlink to obtain a second electrical signal;

The oscillator is used to generate an electrical local oscillator signal;

The mixer is configured to mix the electrical local oscillator signal with the second electrical signal to obtain a baseband signal;

The second controller is configured to calculate the degree of deviation of the actual center frequency of the laser relative to the standard value of the center frequency of the laser according to the first electrical signal, and generate a control based on the degree of deviation signal to control the oscillator to tune the frequency of the electrical local oscillator signal output by it, so that the actual center frequency of the baseband signal obtained by the mixer converges to the standard value of the center frequency of the laser.

In the present invention, the laser output by the laser is divided into detection light and control light, and the deviation degree of the actual center frequency of the laser relative to the standard value of the center frequency of the laser is calculated according to the control light; corresponding compensation is performed according to the deviation degree to eliminate the laser light The influence brought by the drift of the center frequency of the laser can improve the performance of optical coherent detection, and can reduce the requirement on the line width of the light source.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1a is a flowchart of a method for dynamic frequency offset correction provided by an embodiment of the present invention;

Fig. 1b is a schematic diagram of a coherent optical time domain reflectometer system provided by an embodiment of the present invention;

Fig. 1c is a schematic diagram of a coherent optical time domain reflectometer system provided by an embodiment of the present invention;

Fig. 1d is a schematic diagram of a coherent optical time domain reflectometer system provided by an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiment of the present invention detects the frequency offset of the laser and corrects the corresponding frequency offset, thereby eliminating the influence of the frequency drift of the laser output by the laser, reducing the bandwidth requirements of the communication system, and improving Performance of a coherent optical time domain reflectometer system.

Figure 1a shows a flow chart of a method for dynamic frequency offset correction provided by an embodiment of the present invention, including:

Step 11, performing spectroscopic processing on the laser output from the laser to generate detection light and control light.

In this embodiment, a beam splitter such as a coupler is used to split the laser light to generate detection light and control light. The power of the detection light is used to generate the detection light pulse to locate and detect the fault of the link fiber, and its power should be much greater than the power of the control light. Optionally, the ratio of the detection light to the control light can be 99 as shown in the figure: 1.

Step 12, input the control light into the Mach-Zehnder interferometer MZI for interference, and obtain the control light after interference;

Step 13, performing photoelectric conversion on the interfering control light to obtain a first electrical signal;

Step 14. Control the optical path difference of the optical signal transmitted on the two arms of the MZI according to the first electrical signal, so that the optical path difference is a quarter of the wavelength of the laser light;

In this embodiment, the Mach-Zehnder interferometer MZI is used to interfere the control light to obtain the interfered control light, and then perform photoelectric conversion on the interfered control light to obtain the first electrical signal. Since the power of the first electrical signal can reflect the optical path difference between the two arms of the MZI (that is, the optical path difference of the optical signals transmitted on the two arms), the optical path of the two arms of the MZI can be adjusted according to the first electrical signal. Difference, so that the optical path difference is a quarter of the laser, so as to correct the influence of external factors such as temperature and vibration on MZI detection. MZI can adjust the optical path difference between the two arms of MZI by adjusting the stretching degree of piezoelectric ceramics. When the optical path difference between the two arms of the MZI is exactly 1/4 of the laser wavelength, the output of the MZI is in the linear output region, and the output light intensity is proportional to the drift degree of the center frequency of the laser output from the laser.

Step 15. According to the first electrical signal, calculate the degree of deviation of the actual center frequency of the laser relative to the standard value of the center frequency of the laser.

Step 16: Perform corresponding compensation according to the degree of deviation, so that the actual center frequency of the baseband signal obtained after receiving the optical signal transmitted back from the downlink converges to the standard value of the center frequency of the baseband signal.

After obtaining the deviation degree of the actual center frequency of the laser relative to the standard value of the laser center frequency, the following two methods can be adopted to make the baseband signal obtained after receiving the optical signal transmitted from the downlink back to the coherent optical time domain reflectometer system The actual center frequency converges to the standard value of the center frequency of the baseband signal, so as to eliminate the influence caused by the center frequency drift of the laser output by the laser.

Method 1: performing coherent processing on the detection light and the optical signal from the downlink received by the coherent optical time domain reflectometer system, and performing photoelectric conversion on the optical signal obtained by the coherent processing to obtain a second electrical signal; The degree of deviation is used to control the frequency of the electrical local oscillator signal used for mixing with the second electrical signal to obtain the baseband signal, so that the actual center frequency of the baseband signal converges to the center frequency of the baseband signal standard value.

Mode 2: when the probe light is modulated to generate a probe light pulse, the output frequency of the modulation source used for the modulation is controlled according to the degree of deviation, so that the center frequency of the probe light pulse converges to the The standard value of the center frequency of the laser.

In this embodiment, the detection light can be divided by an optical splitter, and a part of the divided detection light is output to a coherent receiver, and the optical signal transmitted back from the downlink is coherently processed by the coherent receiver to obtain second electrical signal; mixing the electrical local oscillator signal with the second electrical signal to obtain a baseband signal; and then controlling the frequency mixing with the second electrical signal to obtain the baseband signal according to the degree of deviation The frequency of the electric local oscillator signal, so that the actual center frequency of the baseband signal converges to the standard value of the center frequency of the baseband signal.

The method of dynamic frequency offset correction will be described in detail below in combination with specific application scenarios. The coherent optical time domain reflectometer system in this embodiment can be a system as shown in Figure 1b, including: a laser 1, a coupler A2, and a photodetector 7. A first controller 8, a second controller 10, a modulation source 11, a modulator 12, and an MZI5; wherein, the MZI5 includes a coupler B3, a piezoelectric ceramic 9, and a coupler C6.

The method for dynamic frequency offset correction will be described in detail below in conjunction with the coherent optical time domain reflectometer system.

The optical power output by the laser 1 is divided into two outputs after passing through the coupler A2, one of which outputs most of the power, which is used as the detection light for detection; the other output power is small, and is used as the control light for control.

The coupler B3 that controls the light input to the MZI5 is divided into two paths, and the two paths of light reach the coupler C6 of the MZI5 through different paths for coherent processing, and the intensity of the output light will reflect the difference in the optical distance of the two arms. After the MZI5 interferes with the input control light, the obtained control light is input to the photodetector 7, and the photodetector 7 performs photoelectric conversion to obtain a first electrical signal for the controller to generate a control signal.

The photodetector 7 transmits the first electrical signal to the first controller 8 . The first controller 8 makes a control decision, generates a control signal to control the MZI5, and controls the expansion and contraction of the piezoelectric ceramic 9 in the MZI5 to adjust the optical path difference between the two arms of the MZI5, so that the optical path difference is a quarter of the laser wavelength. One is to correct the influence of external factors such as temperature and vibration on MZI5, so that the output of MZI5 is always in the linear output area. The feedback control of the first controller 8 on the MZI5 can correct the influence of external factors on the MZI5 to a certain extent.

Further, the following steps need to be performed to further eliminate the drift of the center frequency of the laser output by the laser.

The first electrical signal output by the photodetector 7 is input into the second controller 10; the second controller 10 calculates the actual center frequency of the laser relative to the center frequency of the laser according to the first electrical signal The deviation degree of the standard value; the second controller 10 makes corresponding control to compensate the drift of the laser center frequency according to the deviation degree. The second controller 10 makes a control decision according to the degree of deviation, and when modulating the detection light to generate a detection light pulse, controls the output frequency of the modulation source 11 for modulation control according to the degree of deviation, so that the The actual center frequency of the probe light pulse converges to the standard value of the center frequency of the laser light.

After the modulation source 11 is adjusted, the detection light enters the modulator 12 to be modulated to generate a detection light pulse. The center frequency of the detection light pulse is corrected, and enters the monitored optical cable through the uplink 13, so that the input optical cable The center frequency of the probe light pulse is always around the standard value. Since the center frequency of the detection light pulse generated in the embodiment of the present invention has been corrected, the light signal of the detection light pulse reflected and/or scattered in the optical fiber is transmitted back to the coherent optical time domain reflectometer system in the downlink , the actual center frequency of the received baseband signal can converge to the standard value of the center frequency of the baseband signal, thus eliminating the influence caused by the center frequency drift of the laser.

In another application scenario, the coherent optical time domain reflectometer system can be designed as a system as shown in Figure 1c, including: a laser 1, a coupler A2, a photodetector 7, a first controller 8, and a second controller 10. A modulation source 11, a modulator 12, and an MZI5; wherein, the MZI5 includes a coupler B3, a piezoelectric ceramic 9, and a coupler C6.

On this basis, the system also includes: a coherent receiver 15 , a mixer 17 , an oscillator 16 and a baseband filter 18 .

The method for dynamic frequency offset correction will be described in detail below in conjunction with the coherent optical time domain reflectometer system.

The optical power output by the laser 1 is divided into two outputs after passing through the coupler A2, one of which outputs most of the power, which is used as the detection light for detection; the other output power is small, and is used as the control light for control.

The control light input into the coupler B3 of MZI5 is divided into two paths, and the two paths of light reach the coupler C6 of MZI5 through different paths for coherent processing, and the intensity of the output light will reflect the difference in the optical distance of the two arms. After the MZI5 interferes with the input control light, the obtained control light is input to the photodetector 7, and the photodetector 7 performs photoelectric conversion to obtain a first electrical signal for the controller to generate a control signal.

The photodetector 7 transmits the first electrical signal to the first controller 8 . The first controller 8 makes a control decision, generates a control signal to control the MZI5, and controls the expansion and contraction of the piezoelectric ceramic 9 in the MZI5 to adjust the optical path difference between the two arms of the MZI5, so that the optical path difference between the two arms of the MZI5 is the laser a quarter of the wavelength.

In this system, the modulation source 11 generates a modulation control signal to control the modulator 12 to modulate the detection light; the modulator 12 modulates the detection light to generate a detection light pulse.

The coherent receiver 15 receives the optical signal transmitted back from the downlink, and performs coherent processing on the optical signal transmitted back from the downlink to obtain a second electrical signal.

The oscillator 16 is used for generating electrical local oscillator signals.

The mixer 17 is configured to mix the electrical local oscillator signal and the second electrical signal to obtain a baseband signal.

The method for correcting the dynamic frequency offset in this embodiment is as follows:

The first electrical signal output by the photodetector 7 is input into the second controller 10; the second controller 10 calculates the actual center frequency of the laser relative to the center frequency of the laser according to the first electrical signal The degree of deviation of the standard value; and based on the degree of deviation, a control signal is generated to control the oscillator 16 to tune the frequency of the electrical local oscillator signal output by it, so that the baseband signal obtained by the mixer 17 The actual center frequency of the laser converges to the standard value of the center frequency of the laser, thereby realizing the correction of the dynamic frequency deviation.

In this embodiment, a coupler can also be used to divide the probe light, and a part of the probe light can be output to the coherent receiver. At this time, the coherent optical time domain reflectometer system is shown in Figure 1d, through the coupler D, the detection light is divided into two parts, one part is input to the modulator 12 for modulation, and the other part is input to the coherent receiver 15 for coherent processing with the optical signal transmitted back from the downlink to generate a second electrical signal, and the second controller 10 The electrical local oscillator signal generated after tuning is mixed with the second electrical signal, and the actual center frequency of the obtained baseband signal converges to the standard value of the center frequency of the baseband signal, thereby realizing the correction of the dynamic frequency offset.

In this embodiment, the laser output by the laser is divided into probe light and control light, and the deviation degree of the actual center frequency of the laser relative to the standard value of the center frequency of the laser is calculated according to the control light; corresponding compensation control is performed according to the deviation degree, so that The influence brought by the center frequency drift of the laser is eliminated, the optical coherent detection performance is improved, and the requirement for the line width of the light source can be reduced.

An embodiment of the present invention provides a coherent optical time domain reflectometer system, and a schematic structural diagram of the system can be referred to in FIG. 1c. It includes: a laser 1 , a first beam splitter 2 (could be a coupler A in the figure), an MZI 5 , a photodetector 7 , a first controller 5 , a second controller 10 , a modulator 12 and a modulation source 11 .

The laser 1 is used to generate laser light;

The first beam splitter 2 is used to split the laser light to obtain detection light and control light;

The MZI5 is configured to interfere with the input control light to obtain the control light after interference;

The photodetector 7 is configured to photoelectrically convert the interfering control light to obtain a first electrical signal;

The first controller 8 is configured to generate a control signal according to the first electrical signal, so as to control the MZI5, so that the optical path difference of the optical signal transmitted on the two arms of the MZI5 is equal to that of the laser a quarter of the wavelength;

The modulator 12 is configured to modulate the probe light to generate a probe light pulse;

The modulation source 11 is configured to generate a modulation control signal to control the modulator 12 to modulate the detection light;

The second controller 10 is configured to calculate the degree of deviation of the actual center frequency of the laser relative to the standard value of the center frequency of the laser according to the first electrical signal, and based on the degree of deviation, generate The control signal is used to control the modulation source 11 to output the output frequency of the modulation control signal, so that the actual center frequency of the detection light pulse generated by the modulation of the modulator 12 converges to the standard value of the center frequency of the laser.

In addition, the system of this embodiment further includes: a coherent receiver 15, configured to receive the optical signal transmitted back from the downlink, and perform coherent processing on the optical signal transmitted back from the downlink.

On the basis of the coherent optical time domain reflectometer system shown in FIG. 1 c , the detection light can also be divided by an optical splitter, and a part of the divided detection light is output to the coherent receiver 15 . At this time, the system needs to be further improved, and the structural schematic diagram of the improved coherent optical time domain reflectometer system can be referred to as shown in Figure 1d. At this time, the system further includes: a second optical splitter 4 (which can be Figure 1d The shown coupler D) is used to separate a part of light from the probe light and input it to the coherent receiver 15 .

For the interaction mechanism and functions among the modules of the coherent optical time domain reflectometer system in this embodiment, please refer to the descriptions of the corresponding embodiments in FIG. 1a to FIG. 1d , and details will not be repeated here.

In this embodiment, the laser output by the laser is divided into probe light and control light, and the deviation degree of the actual center frequency of the laser relative to the standard value of the center frequency of the laser is calculated according to the control light; corresponding compensation control is performed according to the deviation degree, so that The influence brought by the center frequency drift of the laser is eliminated, the optical coherent detection performance is improved, and the requirement for the line width of the light source can be reduced.

An embodiment of the present invention provides a coherent optical time domain reflectometer system, and the structural diagram of the system can be seen in FIG. 1d. Including: laser 1, first beam splitter 2 (could be coupler A in the figure), MZI5, photodetector 7, first controller 8, second controller 10, modulator 12, modulation source 11, coherent receiver 15 , mixer 17 and oscillator 16 .

The laser 1 is used to generate laser light;

The first beam splitter 2 is used to split the laser light to obtain detection light and control light;

The MZI5 is configured to interfere with the input control light to obtain the control light after interference;

The photodetector 7 is configured to photoelectrically convert the interfering control light to obtain a first electrical signal;

The first controller 8 is configured to generate a control signal according to the first electrical signal, so as to control the MZI5, so that the optical path difference of the optical signal transmitted on the two arms of the MZI5 is equal to that of the laser a quarter of the wavelength;

The modulator 12 is configured to modulate the probe light to generate a probe light pulse;

The modulation source 11 is configured to generate a modulation control signal to control the modulator 12 to modulate the detection light;

The coherent receiver 15 is configured to receive the optical signal transmitted back from the downlink, and perform coherent processing on the optical signal transmitted back from the downlink to obtain a second electrical signal;

The oscillator 16 is used to generate an electrical local oscillator signal;

The mixer 17 is configured to mix the electrical local oscillator signal with the second electrical signal to obtain a baseband signal;

The second controller 10 is configured to calculate the degree of deviation of the actual center frequency of the laser relative to the standard value of the center frequency of the laser according to the first electrical signal, and based on the degree of deviation, generate control signal to control the oscillator 16 to tune the frequency of the electrical local oscillator signal output by it, so that the actual center frequency of the baseband signal obtained by the mixer 17 converges to the standard value of the center frequency of the laser .

In this embodiment, the detection light can be divided by a light splitter, and a part of the detection light is output to the coherent receiver 15, and the system further includes: a second light splitter 4 (which can be a coupler D in the figure ), used to separate a part of light from the probe light, and input it into the coherent receiver 15 to perform coherence with the optical signal transmitted back from the downlink.

For the interaction mechanism and functions among the modules of the device for dynamic frequency offset correction of the optical fiber communication system in this embodiment, please refer to the descriptions of the corresponding embodiments in FIG. 1a to FIG. 1d , which will not be repeated here.

In this embodiment, the laser output by the laser is divided into probe light and control light, and the deviation degree of the actual center frequency of the laser relative to the standard value of the center frequency of the laser is calculated according to the control light; corresponding compensation control is performed according to the deviation degree, so that The influence brought by the center frequency drift of the laser is eliminated, the optical coherent detection performance is improved, and the requirement for the line width of the light source can be reduced.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (9)

1. method that dynamic frequency deviation is corrected is applied in the influence that the frequency drift of eliminating laser in the coherent light time domain reflection instrument system is brought, and it is characterized in that, comprising:

Laser to described laser output carries out light-splitting processing, generates to survey light and control light;

Described control light is input among the Mach-Zehnder interferometer MZI interferes the control light after obtaining interfering;

Control light after the described interference is carried out opto-electronic conversion, obtain first signal of telecommunication;

Be controlled at the optical path difference of the light signal that transmits on two arms of described MZI according to described first signal of telecommunication, make that described optical path difference is 1/4th of a described Wavelength of Laser;

According to described first signal of telecommunication, calculate the degree of deviation of the practical center frequency of described laser with respect to the standard value of the centre frequency of described laser;

Carry out corresponding compensation according to the described degree of deviation, the practical center frequency of the baseband signal that feasible light signal of returning from downlink transmission obtains after receiving converges on the standard value of the centre frequency of described baseband signal.

2. method according to claim 1, it is characterized in that, carry out corresponding compensation according to the described degree of deviation, the practical center frequency of the baseband signal that feasible light signal of returning from downlink transmission obtains after receiving converges on the standard value of the centre frequency of described baseband signal, comprising:

The light signal from down link that described detection light and described coherent light time domain reflection instrument system the are received processing that is concerned with is carried out opto-electronic conversion to the relevant light signal that obtains of handling, and obtains second signal of telecommunication;

According to the described degree of deviation, control is used for carrying out the frequency that mixing obtains the electric local oscillation signal of described baseband signal with described second signal of telecommunication, makes the practical center frequency of described baseband signal converge on the standard value of the centre frequency of described baseband signal.

3. method according to claim 1, it is characterized in that, carry out corresponding compensation according to the described degree of deviation, the practical center frequency of the baseband signal that feasible light signal of returning from downlink transmission obtains after receiving is positioned at the standard value of the centre frequency of described baseband signal, comprising:

Described detection light is being modulated when generating detecting optical pulses, be used to carry out the output frequency of the modulation source of described modulation, making the centre frequency of described detecting optical pulses converge on the standard value of the centre frequency of described laser according to described degree of deviation control.

4. method according to claim 1 is characterized in that the power of described detection light is greater than the power of described control light.

5. a coherent light time domain reflection instrument system is characterized in that, comprising: laser, first optical splitter, Mach Zehnder interferometer MZI, photodetector, first controller, second controller, modulator and modulation source;

Described laser is used to produce laser;

Described first optical splitter is used for described laser is carried out beam split, obtains surveying light and control light;

Described MZI is used for the described control light of input is interfered the control light after obtaining interfering;

Described photodetector is used for that the control light after the described interference is carried out opto-electronic conversion and obtains first signal of telecommunication;

Described first controller is used for producing control signal according to described first signal of telecommunication, so that described MZI is controlled, makes that the optical path difference of the light signal that transmits on two arms of described MZI is 1/4th of a described Wavelength of Laser;

Described modulator is used for described detection light is modulated, and generates detecting optical pulses;

Described modulation source is used to produce modulator control signal and controls described modulator described detection light is modulated;

Described second controller, be used for according to described first signal of telecommunication, calculate the degree of deviation of the practical center frequency of described laser with respect to the standard value of the centre frequency of described laser, and based on the described degree of deviation, produce control signal and export the output frequency of described modulator control signal, make the practical center frequency of the described detecting optical pulses that described modulators modulate generates converge on the standard value of the centre frequency of described laser to control described modulation source.

6. coherent light time domain reflection instrument system according to claim 5 is characterized in that, described system also further comprises:

Coherent receiver is used for receiving the light signal of returning from the down link transmission, and to the processing that is concerned with of the described light signal that transmission is returned from down link.

7. coherent light time domain reflection instrument system according to claim 5 is characterized in that, described system also further comprises:

Second optical splitter is used for telling a part of light from described detection light, and is entered into described coherent receiver.

8. coherent light time domain reflection instrument system, it is characterized in that, described system comprises: laser, first optical splitter, Mach Zehnder interferometer MZI, photodetector, first controller, second controller, modulator, modulation source, coherent receiver, frequency mixer and oscillator;

Described laser is used to produce laser;

Described first optical splitter is used for described laser is carried out beam split, obtains surveying light and control light;

Described MZI is used for the described control light of input is interfered the control light after obtaining interfering;

Described photodetector is used for that the control light after the described interference is carried out opto-electronic conversion and obtains first signal of telecommunication;

Described first controller is used for producing control signal according to described first signal of telecommunication, so that described MZI is controlled, makes that the optical path difference of the light signal that transmits on two arms of described MZI is 1/4th of a described Wavelength of Laser;

Described modulator is used for described detection light is modulated, and generates detecting optical pulses;

Described modulation source is used to produce modulator control signal and controls described modulator described detection light is modulated;

Described coherent receiver is used for receiving the light signal of returning from the down link transmission, and to the processing that is concerned with of the described light signal that transmission is returned from down link, obtains second signal of telecommunication;

Described oscillator is used to produce electric local oscillation signal;

Described frequency mixer is used for the described electric local oscillation signal and described second signal of telecommunication are carried out mixing, obtains baseband signal;

Described second controller, be used for according to described first signal of telecommunication, calculate the degree of deviation of the practical center frequency of described laser with respect to the standard value of the centre frequency of described laser, and based on the described degree of deviation, produce the frequency of control signal, make the practical center frequency of the described baseband signal that described frequency mixer obtains converge on the standard value of the centre frequency of described laser with the described electric local oscillation signal of controlling described its output of oscillator tuning.

9. coherent light time domain reflection instrument system according to claim 8 is characterized in that, described system also further comprises:

Second optical splitter is used for telling a part of light from described detection light, and is entered in the described coherent receiver with the described light signal that transmission is returned from down link and is concerned with.

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