WO2015010581A1 - Coherent optical time domain reflectometry coded based on detection frequency - Google Patents

Coherent optical time domain reflectometry coded based on detection frequency Download PDF

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Publication number
WO2015010581A1
WO2015010581A1 PCT/CN2014/082580 CN2014082580W WO2015010581A1 WO 2015010581 A1 WO2015010581 A1 WO 2015010581A1 CN 2014082580 W CN2014082580 W CN 2014082580W WO 2015010581 A1 WO2015010581 A1 WO 2015010581A1
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Prior art keywords
frequency
time domain
light
optical time
coherent optical
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PCT/CN2014/082580
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French (fr)
Chinese (zh)
Inventor
吕立冬
梁云
李炳林
郭经红
何金陵
孙志峰
李垠韬
Original Assignee
国家电网公司
中国电力科学研究院
国网江苏省电力公司
国网江苏省电力公司信息通信分公司
国网湖北省电力公司信息通信公司
国网冀北电力有限公司信通分公司
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Publication of WO2015010581A1 publication Critical patent/WO2015010581A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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

Definitions

  • the invention belongs to the field of communications, and in particular relates to a coherent optical time domain reflectometer for optical fiber communication line characterization, event recognition and fault location.
  • coherent optical time domain reflection techniques For multi-relay ultra-long-haul fiber-optic communication lines, such as transoceanic submarine cables, coherent optical time domain reflection techniques are commonly used.
  • the coherent optical time domain reflection technique utilizes the principle of laser radar to locate the position of the scattering and/or reflection points by injecting a probe light pulse into the fiber and recording the return time of the Rayleigh scattered light and/or reflected light of the light pulse in the fiber.
  • the pulse width of the light pulse corresponds to the spatial resolution of the measurement, and the two are proportional to each other.
  • the pulse width of the probe light of 1 microsecond corresponds to the spatial resolution of 100 meters, and the pulse period is slightly larger than the round trip time of the probe light signal in the line.
  • the coherent detection method uses the coherent detection method to transmit the power of the detection signal light to the heterodyne IF signal by detecting the heterodyne of the light and the local oscillator, so that most of the out-of-band noise can be suppressed by narrow-band filtering the intermediate frequency signal.
  • the coherent detection method uses the coherent detection method to transmit the power of the detection signal light to the heterodyne IF signal by detecting the heterodyne of the light and the local oscillator, so that most of the out-of-band noise can be suppressed by narrow-band filtering the intermediate frequency signal.
  • the pulse width should be as small as possible, so that the duty ratio of the probe light pulse is extremely small, for example,
  • the pulse period is slightly greater than 100 milliseconds, and the pulse width is typically in the range of 1 microsecond to 100 microseconds. Since the erbium-doped fiber amplifier is used as the relay amplifier in the line, the low duty-cycle light pulse will cause a transient effect in the erbium-doped fiber amplifier, and the transient effect will accumulate in each erbium-doped fiber amplifier to form a light surge. This causes severe distortion of the light pulse and even damages the erbium-doped fiber amplifier.
  • frequency shift keying techniques are usually used. It introduces a fill light pulse complementary to the detection light pulse in time series, the probe light pulse and the fill light pulse respectively correspond to the respective laser and the pulse modulator, and then combine the two into a quasi-continuous using a coupler or a wavelength division multiplexer. Light, this quasi-continuous light can suppress light surges very well.
  • Evangelides Stephen et al. proposed a coherent optical time domain reflectometer based on frequency pulse sweep, and applied for a world patent, patent number: US20040794174, patent name is "COTDR ARRANGEMENT WITH SWEPT FREQUENCY PULSE GENERATOR FOR AN OPTICAL TRANSMISSION SYSTEM".
  • the frequency of the frequency pulse involved in the method jumps with time but the laser power is continuous.
  • the continuous laser enters the erbium-doped fiber amplifier in the fiber line to suppress the transient effect and avoid the light surge.
  • the frequency pulse is the frequency sweep.
  • the sweep frequency does not change the continuity of the laser light and the laser line width, and the continuous light of Brillouin
  • the threshold is very low, which limits the peak power of the frequency pulse and limits the dynamic range of the measurement. Summary of the invention
  • the present invention proposes a coherent optical time domain reflectometer based on detection frequency encoding, which uses the same light source to obtain the probe light and the fill light and the local oscillator light having a constant frequency, and the probe light frequency is coded in time series. , thereby increasing the speed and dynamic range of the measurement.
  • the invention relates to a coherent optical time domain reflectometer based on detection frequency coding, which is improved in that the coherent optical time domain reflectometer comprises: a laser 1, a first coupler 2, a frequency encoder 3, and a radio frequency drive 4, circulator 5, optical interface 6, optical filter 7, 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 light emitted by the laser 1 is divided into two paths by the first coupler 2, one input to the frequency encoder 3, and the other input directly to the second coupler 8;
  • the RF driver 4 generates a frequency-frequency-changing RF signal to drive the frequency encoder 3, and the frequency encoder 3 modulates the incident light to generate a detection frequency-encoded pulsed light and a timing-complementary filling optical frequency pulse;
  • the detecting frequency pulse light and the filling light pulse are input to the first port of the circulator 5, and are outputted from the second port of the circulator 5, and injected into the optical fiber communication line under test via the optical interface 6.
  • the detection frequency pulse light and the fill light frequency pulse are returned to the Rayleigh scattering signal in the fiber under test, and the optical filter 7 is input through the third port of the circulator 5;
  • the probe optical signal filtered by the optical filter 7 enters the second coupler 8 and is mixed with the local oscillator, and the intermediate frequency signal generated by the mixing is received by the photodetector 9 and outputs a corresponding intermediate frequency signal;
  • the intermediate frequency signal is amplified by the intermediate frequency amplifier 10 and then collected by the analog to digital conversion module 11.
  • the collected data is transmitted to the signal processing module 12 for data processing, and the display module 13 displays the characterized optical fiber communication.
  • the optical time domain reflection curve of the line attenuation information is transmitted to the signal processing module 12 for data processing, and the display module 13 displays the characterized optical fiber communication.
  • the coherent optical time domain reflectometer comprises a scrambler 14 disposed between the frequency encoder 3 and the circulator 5 for suppressing polarization noise.
  • the coherent optical time domain reflectometer comprises an erbium doped fiber amplifier 15 disposed between the scrambler 14 and the circulator 5 for increasing the power of the probe frequency pulsed light, thereby increasing the dynamic range of the measurement.
  • the frequency encoder 3 selects an electro-optical phase modulator.
  • the frequency encoder 3 uses an electro-optic intensity modulator.
  • the RF driver 4 selects an arbitrary waveform generator for generating a radio frequency signal whose frequency changes with time.
  • the optical filter 7 is a fiber grating.
  • the photodetector 9 uses a balanced photodetector for improving detection sensitivity.
  • the analog-to-digital conversion module 11 selects a data acquisition card for converting the analog intermediate frequency signal into a digital signal.
  • the signal processing module 12 includes an FPGA chip for processing digital signals. Compared with the prior art, the beneficial effects of the present invention are:
  • the frequency of the detection frequency pulse obtained by the frequency encoding method does not destroy the continuity of the laser power. Compared with the frequency shift keying technique, it does not need to separately configure the laser and the acousto-optic modulator for filling light, and the frequency pulse sweep In a frequency manner, the present invention converts a single frequency pulse into a multi-frequency, thereby effectively increasing the Brillouin threshold of continuous light, enabling the device to obtain a larger measurement dynamic range.
  • the present invention relates to a coherent optical time domain reflectometer.
  • the local oscillator frequency is constant, which reduces the frequency modulation and control difficulty of the probe light, and is advantageous
  • the present invention uses an optical filter to filter out the detection signal light, thereby effectively suppressing interference of other optical frequencies, and further improving the measured signal-to-noise ratio.
  • FIG. 1 is a schematic structural diagram of a coherent optical time domain reflectometer based on detection frequency encoding according to the present invention.
  • FIG. 2 is a schematic diagram of a frequency pulse coded probe light pulse sequence according to the present invention.
  • Figure 3 shows the output power spectrum of a phase modulator driven by a single frequency.
  • Figure 4 is an optical time domain reflectance curve corresponding to each coded detection frequency.
  • FIG. 5 is a detection curve obtained by a coherent optical time domain reflectometer based on detection frequency encoding according to the present invention. detailed description
  • the present invention provides a coherent optical time domain reflectometer based on detection frequency encoding, which includes: a laser 1 for providing detection light, filling light, and single-frequency local oscillator;
  • the frequency encoder 3 selects an electro-optic phase modulator or an electro-optic intensity modulator for modulating a single-frequency continuous laser and obtaining a frequency pulse output;
  • RF driver 4 RF generator, such as Agilent's E8257D, RF range from 200kHz to 26.5GHz, which provides frequency-coded RF signals to drive the phase modulator;
  • the circulator 5 provides respective channels for transmitting and receiving light
  • Optical interface 6 for optical path access
  • Optical filter 7 fiber grating is used to filter out the noise and improve the optical signal to noise ratio
  • a second coupler 8 for coupling of two paths of light
  • Photodetector 9 using balanced photodetector for photoelectric receiving
  • the analog-to-digital conversion module 11 selects a data acquisition card for converting the radio frequency electrical signal into a digital signal;
  • the signal processing module 12 mainly includes an FPGA chip for calculating and processing the digital signal;
  • the display module 13 includes a display screen, etc. Used to display measurement results;
  • a scrambler 14 is used to randomly change the polarization state of the light
  • An erbium doped fiber amplifier 15 is used to boost optical power
  • the laser 1 is sequentially connected to the first coupler 2, the frequency encoder 3, the circulator 5, and the optical interface 6, and is connected to the optical fiber communication line; the first coupler 2 is further connected to the second coupler 8, and the circulator 5 is also connected to the second coupler 8 via the optical filter 7.
  • the second coupler 8 is in turn connected to the photodetector 9, the radio frequency amplifier 10, the analog to digital conversion module 11, the signal processing module 12, and the display module 13.
  • the present embodiment adds a scrambler 14 between the frequency encoder 3 and the circulator 5; in order to boost the power of the probe frequency pulse light, the scrambler 14 and the ring
  • An erbium-doped fiber amplifier 15 is added between the devices 5 to increase the dynamic range of the measurement.
  • the laser light from the laser 1 is divided into two by the first coupler 2, one input frequency encoder 3, and the other directly into the second coupler 8;
  • the RF driver 4 generates a radio frequency signal whose frequency changes with time as shown in FIG. 2, ") ⁇ 1, ⁇ , ..., f T , , to achieve frequency coding, where f T is added for modulation fill light.
  • Drive frequency the rest is the probe frequency.
  • the duration of each detection frequency is 1 microsecond, which is a frequency pulse that exists in time series.
  • the RF driver 4 drives the frequency encoder 3, and the frequency encoder 3 selects the phase modulator.
  • the power spectrum of the output of the single frequency drive is shown in FIG.
  • the spacing of the optical frequencies in FIG. 3 is equal to the RF frequency output by the RF driver 4, such that the RF driving frequency encoder 3 of the timing shown in FIG. 2 modulates one laser emitted by the laser 1, and the power spectrum is changed with time.
  • the spectrum which enables the encoding of the frequency of the probe light.
  • the frequency encoder 3 generates the detection frequency pulse light and the timing-complementary filling light pulse, and then the detection pulse light and the filling light pulse enter the first port of the circulator 5, from The second port output of the circulator 5 is injected through the optical interface 6 into the multi-relay amplified optical fiber communication line; the detection frequency pulse light and the filling optical pulse are returned back to the Rayleigh scattering signal in the optical fiber to be tested, through the circulator
  • the third port of 5 is connected to the optical filter 7;
  • the probe light signal filtered by the optical filter 7 enters the second coupler 8 and is mixed with the local oscillator light (ie, the other laser light branched from the first coupler 2), and the intermediate frequency signal generated by the mixing of the two is received by the photodetector 9. And output corresponding corresponding intermediate frequency electrical signals, the intermediate frequencies corresponding to the respective detection frequencies are ⁇ , ⁇ , ⁇ , ..., ⁇ , as shown in FIG. 4 .
  • the intermediate frequency signal is amplified by the intermediate frequency amplifier 10 to facilitate high-precision analog-to-digital conversion by the analog-to-digital conversion module 11, and the analog-to-digital conversion module 11 selects a data acquisition card, and the collected data is transmitted to the signal processing module 12 for data processing, and the signal processing module 12 digitally bandpass filtering the digital signals to extract the respective detection frequencies, and then digitally down-converting and digitally low-pass filtering each of the detection frequencies to finally obtain the power of the detection signals, and then superimposing the results of the multiple measurements.
  • the measured random noise is reduced, so that the optical time domain reflection curves corresponding to the respective detection frequency pulses are as shown in FIG.
  • the display module 13 displays an optical time domain reflectance curve that characterizes the attenuation information of the fiber optic communication line, as shown in FIG.
  • the invention can obtain the detection light pulse and the filling light pulse from the same laser light source, without using the filling light source and the pulse modulator alone to obtain the filling light pulse, and, due to the detection light frequency Encoded in time series, each detection frequency corresponds to a detection curve, and the superimposed average results of multiple detection curves can reduce the fading noise of the detection curve and improve the dynamic range of the measurement more quickly.

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Abstract

A coherent optical time domain reflectometry coded based on a detection frequency comprises a laser (1), a first coupler (2), a frequency coder (3), a radio frequency driver (4), a circulator (5), an optical interface (6), a light filter (7), a second coupler (8), a photoelectric detector (9), an intermediate frequency amplifier (10), a data acquisition module (11), a signal processing module (12), and a display module (13). A laser beam emitted by the laser (1) is frequency-coded by the frequency coder (3) to obtain detection frequency pulsed light and a filled light pulse sequentially complementary to the detection frequency pulsed light. The detection frequency pulsed light and the filled light pulse are different in frequency, and after their backward Rayleigh scattered signals in an optical fiber line are returned, the signals enter the light filter (7) through a third port; a detection optical signal and local oscillation light that are obtained after the filtering are coherent in the second coupler (8), and then the photoelectric detector (9) outputs a coherent intermediate frequency signal; and finally, the intermediate frequency signal is collected and processed to obtain a timing curve reflecting characteristics of the optical fiber line.

Description

一种基于探测频率编码的相干光时域反射仪  Coherent optical time domain reflectometer based on detection frequency coding
技术领域 Technical field
本发明属于通信领域， 具体涉及一种用于光纤通信线路表征、事件识别和故 障定位的相干光时域反射仪。  The invention belongs to the field of communications, and in particular relates to a coherent optical time domain reflectometer for optical fiber communication line characterization, event recognition and fault location.
背景技术 Background technique
对多中继超长距离光纤通信线路如越洋海底光缆的监测通常采用相干光时 域反射技术。相干光时域反射技术利用激光雷达原理， 通过向光纤注入探测光脉 冲， 并记录光脉冲在光纤中的瑞利散射光和 /或反射光的返回时间来定位散射和 / 或反射点的位置，光脉冲的脉宽对应测量的空间分辨率，二者成正比关系，比如， 1微秒的探测光脉冲宽度对应 100米的空间分辨率， 而脉冲周期略大于探测光信 号在线路中的往返时间， 同时， 它利用相干检测方法通过探测光与本振光外差， 将探测信号光的功率转移到外差中频信号上，于是通过对中频信号进行窄带滤波 就可以抑制掉大部分带外噪声， 从而提升测量的动态范围。对于多中继超长距离 光纤通信线路， 线路距离越长则脉冲周期越大， 而要获得高的空间分辨率， 则脉 宽应尽量小， 于是探测光脉冲的占空比极小， 比如， 对于 1万公里长的越洋海底 光缆的监测， 脉冲周期略大于 100毫秒， 而脉宽通常在 1微秒至 100微秒范围。 由于线路多采用掺铒光纤放大器作为中继放大器，低占空比的光脉冲将在掺铒光 纤放大器中引起瞬态效应，瞬态效应在各个掺铒光纤放大器中积累会形成光浪涌， 从而导致光脉冲严重变形， 甚至使掺铒光纤放大器遭到损坏。  For multi-relay ultra-long-haul fiber-optic communication lines, such as transoceanic submarine cables, coherent optical time domain reflection techniques are commonly used. The coherent optical time domain reflection technique utilizes the principle of laser radar to locate the position of the scattering and/or reflection points by injecting a probe light pulse into the fiber and recording the return time of the Rayleigh scattered light and/or reflected light of the light pulse in the fiber. The pulse width of the light pulse corresponds to the spatial resolution of the measurement, and the two are proportional to each other. For example, the pulse width of the probe light of 1 microsecond corresponds to the spatial resolution of 100 meters, and the pulse period is slightly larger than the round trip time of the probe light signal in the line. At the same time, it uses the coherent detection method to transmit the power of the detection signal light to the heterodyne IF signal by detecting the heterodyne of the light and the local oscillator, so that most of the out-of-band noise can be suppressed by narrow-band filtering the intermediate frequency signal. Thereby increasing the dynamic range of the measurement. For a multi-relay ultra-long-distance fiber-optic communication line, the longer the line distance is, the larger the pulse period is. To obtain high spatial resolution, the pulse width should be as small as possible, so that the duty ratio of the probe light pulse is extremely small, for example, For the monitoring of a 10,000-kilometer transoceanic submarine cable, the pulse period is slightly greater than 100 milliseconds, and the pulse width is typically in the range of 1 microsecond to 100 microseconds. Since the erbium-doped fiber amplifier is used as the relay amplifier in the line, the low duty-cycle light pulse will cause a transient effect in the erbium-doped fiber amplifier, and the transient effect will accumulate in each erbium-doped fiber amplifier to form a light surge. This causes severe distortion of the light pulse and even damages the erbium-doped fiber amplifier.
对于光浪涌的抑制，通常采用频移键控技术。它引入与探测光脉冲在时序上 互补的填充光脉冲，探测光脉冲和填充光脉冲分别对应各自的激光器和脉冲调制 器， 再利用耦合器或波分复用器将二者合为一路准连续光， 这种准连续光能很好 地抑制光浪涌。 另夕卜， Evangelides Stephen等人提出了一种基于频率脉冲扫频的 相干光时域反射仪方案， 并申请了世界专利， 专利号为： US20040794174, 专利 名称为 " COTDR ARRANGEMENT WITH SWEPT FREQUENCY PULSE GENERATOR FOR AN OPTICAL TRANSMISSION SYSTEM" 。 其方法涉及的 频率脉冲的频率随时间跳变但激光功率是连续的，连续的激光进入光纤线路中的 掺铒光纤放大器就能抑制瞬态效应从而避免光浪涌， 但是， 频率脉冲是扫频的， 为了使探测光与本振光产生的相干中频信号稳定，因此本振光的频率应相应改变， 另外， 扫频并未改变激光的连续性和激光线宽， 该连续光的布里渊阈值很低， 这 就限制了频率脉冲的峰值功率从而限制了测量的动态范围。 发明内容  For the suppression of light surges, frequency shift keying techniques are usually used. It introduces a fill light pulse complementary to the detection light pulse in time series, the probe light pulse and the fill light pulse respectively correspond to the respective laser and the pulse modulator, and then combine the two into a quasi-continuous using a coupler or a wavelength division multiplexer. Light, this quasi-continuous light can suppress light surges very well. In addition, Evangelides Stephen et al. proposed a coherent optical time domain reflectometer based on frequency pulse sweep, and applied for a world patent, patent number: US20040794174, patent name is "COTDR ARRANGEMENT WITH SWEPT FREQUENCY PULSE GENERATOR FOR AN OPTICAL TRANSMISSION SYSTEM". The frequency of the frequency pulse involved in the method jumps with time but the laser power is continuous. The continuous laser enters the erbium-doped fiber amplifier in the fiber line to suppress the transient effect and avoid the light surge. However, the frequency pulse is the frequency sweep. In order to stabilize the coherent intermediate frequency signal generated by the probe light and the local oscillator light, the frequency of the local oscillator light should be changed accordingly. In addition, the sweep frequency does not change the continuity of the laser light and the laser line width, and the continuous light of Brillouin The threshold is very low, which limits the peak power of the frequency pulse and limits the dynamic range of the measurement. Summary of the invention
针对现有技术的不足，本发明提出一种基于探测频率编码的相干光时域反射 仪， 它利用同一光源获得探测光和填充光以及频率恒定的本振光， 而且探测光频 率被按时序编码， 从而提升测量的速度和动态范围。  In view of the deficiencies of the prior art, the present invention proposes a coherent optical time domain reflectometer based on detection frequency encoding, which uses the same light source to obtain the probe light and the fill light and the local oscillator light having a constant frequency, and the probe light frequency is coded in time series. , thereby increasing the speed and dynamic range of the measurement.
本发明提出的一种基于探测频率编码的相干光时域反射仪，其改进之处在于， 所述相干光时域反射仪包括： 激光器 1、 第一耦合器 2、 频率编码器 3、 射频驱 动器 4、 环形器 5、 光接口 6、 光滤波器 7、 第二耦合器 8、 光电探测器 9、 射频 放大器 10、 模数转换模块 11、 信号处理模块 12和显示模块 13 ; The invention relates to a coherent optical time domain reflectometer based on detection frequency coding, which is improved in that the coherent optical time domain reflectometer comprises: a laser 1, a first coupler 2, a frequency encoder 3, and a radio frequency drive 4, circulator 5, optical interface 6, optical filter 7, second coupler 8, photodetector 9, radio frequency amplifier 10, analog to digital conversion module 11, signal processing module 12 and display module 13;
所述激光器 1发出的激光被所述第一耦合器 2分成两路，一路输入所述频率 编码器 3， 而另一路直接输入所述第二耦合器 8;  The laser light emitted by the laser 1 is divided into two paths by the first coupler 2, one input to the frequency encoder 3, and the other input directly to the second coupler 8;
所述射频驱动器 4产生频率随时序变化的射频信号驱动所述频率编码器 3， 所述频率编码器 3 调制入射光产生探测频率编码的脉冲光和与之在时序上互补 的填充光频率脉冲； 所述探测频率脉冲光和所述填充光脉冲输入所述环形器 5 的第一端口， 并从所述环形器 5的第二端口输出， 经所述光接口 6注入到被测光 纤通信线路；  The RF driver 4 generates a frequency-frequency-changing RF signal to drive the frequency encoder 3, and the frequency encoder 3 modulates the incident light to generate a detection frequency-encoded pulsed light and a timing-complementary filling optical frequency pulse; The detecting frequency pulse light and the filling light pulse are input to the first port of the circulator 5, and are outputted from the second port of the circulator 5, and injected into the optical fiber communication line under test via the optical interface 6.
所述探测频率脉冲光和所述填充光频率脉冲在被测光纤中的背向瑞利散射 信号返回， 经所述环形器 5的第三端口输入所述光滤波器 7;  The detection frequency pulse light and the fill light frequency pulse are returned to the Rayleigh scattering signal in the fiber under test, and the optical filter 7 is input through the third port of the circulator 5;
所述光滤波器 7滤出的探测光信号进入所述第二耦合器 8与本振光混合，二 者混合产生的中频信号被所述光电探测器 9接收并输出对应的中频信号；  The probe optical signal filtered by the optical filter 7 enters the second coupler 8 and is mixed with the local oscillator, and the intermediate frequency signal generated by the mixing is received by the photodetector 9 and outputs a corresponding intermediate frequency signal;
所述中频信号经所述中频放大器 10放大后由所述模数转换模块 11进行采集， 采集到的数据传输给所述信号处理模块 12进行数据处理， 并通过所述显示模块 13显示表征光纤通信线路衰减信息的光时域反射曲线。  The intermediate frequency signal is amplified by the intermediate frequency amplifier 10 and then collected by the analog to digital conversion module 11. The collected data is transmitted to the signal processing module 12 for data processing, and the display module 13 displays the characterized optical fiber communication. The optical time domain reflection curve of the line attenuation information.
其中，所述相干光时域反射仪包括设置在所述频率编码器 3和环形器 5之间 的扰偏器 14， 用于抑制偏振噪声。  Wherein the coherent optical time domain reflectometer comprises a scrambler 14 disposed between the frequency encoder 3 and the circulator 5 for suppressing polarization noise.
其中， 所述相干光时域反射仪包括设置在所述扰偏器 14和环形器 5之间的 掺铒光纤放大器 15， 用于提升探测频率脉冲光的功率， 进而提高测量的动态范 围。  Wherein, the coherent optical time domain reflectometer comprises an erbium doped fiber amplifier 15 disposed between the scrambler 14 and the circulator 5 for increasing the power of the probe frequency pulsed light, thereby increasing the dynamic range of the measurement.
其中， 所述频率编码器 3选用电光相位调制器。  The frequency encoder 3 selects an electro-optical phase modulator.
或者， 所述频率编码器 3选用电光强度调制器。  Alternatively, the frequency encoder 3 uses an electro-optic intensity modulator.
其中，所述射频驱动器 4选用任意波形发生器， 用于产生频率随时序变化的 射频信号。  Wherein, the RF driver 4 selects an arbitrary waveform generator for generating a radio frequency signal whose frequency changes with time.
其中， 所述光滤波器 7选用光纤光栅。  The optical filter 7 is a fiber grating.
其中， 所述光电探测器 9选用平衡光电探测器， 用于提升探测灵敏度。  Wherein, the photodetector 9 uses a balanced photodetector for improving detection sensitivity.
其中， 所述模数转换模块 11选用数据采集卡， 用于将模拟的中频信号转换 成数字信号。  The analog-to-digital conversion module 11 selects a data acquisition card for converting the analog intermediate frequency signal into a digital signal.
其中， 所述信号处理模块 12包括 FPGA芯片， 用于处理数字信号。 与现有技术比， 本发明的有益效果为：  The signal processing module 12 includes an FPGA chip for processing digital signals. Compared with the prior art, the beneficial effects of the present invention are:
通过频率编码方式得到的探测频率脉冲的同时并不破坏激光功率的连续性， 相对于频移键控技术它不需要单独配置用于填充光的激光器和声光调制器，而相 对于频率脉冲扫频的方式，本发明将单频脉冲变成多频， 从而能有效提升连续光 的布里渊阈值， 使装置能获得更大的测量动态范围， 另外， 本发明涉及的相干光 时域反射仪的本振光频率恒定， 从而降低了探测光频率调制和控制难度， 并有利 于信号的采集和处理， 而且， 本发明使用光学滤波器滤出探测信号光， 从而能有 效地抑制其它光频率的干扰， 能进一步提升测量的信噪比。 附图说明 The frequency of the detection frequency pulse obtained by the frequency encoding method does not destroy the continuity of the laser power. Compared with the frequency shift keying technique, it does not need to separately configure the laser and the acousto-optic modulator for filling light, and the frequency pulse sweep In a frequency manner, the present invention converts a single frequency pulse into a multi-frequency, thereby effectively increasing the Brillouin threshold of continuous light, enabling the device to obtain a larger measurement dynamic range. In addition, the present invention relates to a coherent optical time domain reflectometer. The local oscillator frequency is constant, which reduces the frequency modulation and control difficulty of the probe light, and is advantageous In addition to the signal acquisition and processing, the present invention uses an optical filter to filter out the detection signal light, thereby effectively suppressing interference of other optical frequencies, and further improving the measured signal-to-noise ratio. DRAWINGS
图 1为本发明提出的一种基于探测频率编码的相干光时域反射仪的结构示意图。 图 2为本发明提出的频率脉冲编码的探测光脉冲序列示意图。 FIG. 1 is a schematic structural diagram of a coherent optical time domain reflectometer based on detection frequency encoding according to the present invention. FIG. 2 is a schematic diagram of a frequency pulse coded probe light pulse sequence according to the present invention.
图 3为相位调制器在单频驱动下的输出功率谱。 Figure 3 shows the output power spectrum of a phase modulator driven by a single frequency.
图 4为各个编码的探测频率对应的光时域反射曲线。 Figure 4 is an optical time domain reflectance curve corresponding to each coded detection frequency.
图 5 为本发明提出的一种基于探测频率编码的相干光时域反射仪得到的探测曲 线。 具体实施方式 FIG. 5 is a detection curve obtained by a coherent optical time domain reflectometer based on detection frequency encoding according to the present invention. detailed description
下面结合附图对本发明的具体实施方式作进一步的详细说明。  The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.
本实施例提供的一种基于探测频率编码的相干光时域反射仪， 它包括： 激光器 1， 用于提供探测光、 填充光以及单频本振光；  The present invention provides a coherent optical time domain reflectometer based on detection frequency encoding, which includes: a laser 1 for providing detection light, filling light, and single-frequency local oscillator;
第一耦合器 2， 用于分光；  a first coupler 2 for splitting light;
频率编码器 3，选用电光相位调制器或电光强度调制器,用于调制单频连续激 光， 并获得频率脉冲输出；  The frequency encoder 3 selects an electro-optic phase modulator or an electro-optic intensity modulator for modulating a single-frequency continuous laser and obtaining a frequency pulse output;
射频驱动器 4， 选用射频发生器， 如安捷伦公司的 E8257D, 射频范围从 200kHz至 26.5GHz, 它提供频率编码的射频信号以驱动相位调制器；  RF driver 4, RF generator, such as Agilent's E8257D, RF range from 200kHz to 26.5GHz, which provides frequency-coded RF signals to drive the phase modulator;
环形器 5， 为光的发送和接收提供各自的通道；  The circulator 5 provides respective channels for transmitting and receiving light;
光接口 6， 用于光路接入；  Optical interface 6, for optical path access;
光滤波器 7， 选用光纤光栅， 用于滤除杂频光， 提升光信噪比；  Optical filter 7, fiber grating is used to filter out the noise and improve the optical signal to noise ratio;
第二耦合器 8， 用于两路光的耦合；  a second coupler 8 for coupling of two paths of light;
光电探测器 9， 选用平衡光电探测器， 用于光电接收；  Photodetector 9, using balanced photodetector for photoelectric receiving;
射频放大器 10， 用于射频信号的放大；  An RF amplifier 10 for amplifying a radio frequency signal;
模数转换模块 11， 选用数据采集卡， 用于将射频电信号转换成数字信号； 信号处理模块 12， 主要包括 FPGA芯片， 用于数字信号的运算和处理； 显示模块 13， 包括显示屏等， 用于显示测量结果；  The analog-to-digital conversion module 11 selects a data acquisition card for converting the radio frequency electrical signal into a digital signal; the signal processing module 12 mainly includes an FPGA chip for calculating and processing the digital signal; and the display module 13 includes a display screen, etc. Used to display measurement results;
扰偏器 14， 用于使光的偏振态随机变化；  A scrambler 14 is used to randomly change the polarization state of the light;
掺铒光纤放大器 15， 用于提升光功率；  An erbium doped fiber amplifier 15 is used to boost optical power;
具体地， 激光器 1依次与第一耦合器 2、 频率编码器 3、 环形器 5和光接口 6连接后， 与光纤通信线路连接； 第一耦合器 2再与第二耦合器 8连接， 且环形 器 5通过光滤波器 7也与第二耦合器 8连接。第二耦合器 8再依次与光电探测器 器 9、射频放大器 10、模数转换模块 11、信号处理模块 12和显示模块 13连接。  Specifically, the laser 1 is sequentially connected to the first coupler 2, the frequency encoder 3, the circulator 5, and the optical interface 6, and is connected to the optical fiber communication line; the first coupler 2 is further connected to the second coupler 8, and the circulator 5 is also connected to the second coupler 8 via the optical filter 7. The second coupler 8 is in turn connected to the photodetector 9, the radio frequency amplifier 10, the analog to digital conversion module 11, the signal processing module 12, and the display module 13.
优选地，本实施例为了抑制偏振噪声， 在所述频率编码器 3和环形器 5之间 的加入了扰偏器 14; 为了提升探测频率脉冲光的功率， 在所述扰偏器 14和环形 器 5之间加入掺铒光纤放大器 15， 进而提高测量的动态范围。 如图 1所述， 激光器 1发出的激光被第一耦合器 2分成两路， 一路输入频率 编码器 3， 而另一路直接输入第二耦合器 8; Preferably, in order to suppress polarization noise, the present embodiment adds a scrambler 14 between the frequency encoder 3 and the circulator 5; in order to boost the power of the probe frequency pulse light, the scrambler 14 and the ring An erbium-doped fiber amplifier 15 is added between the devices 5 to increase the dynamic range of the measurement. As shown in Figure 1, the laser light from the laser 1 is divided into two by the first coupler 2, one input frequency encoder 3, and the other directly into the second coupler 8;
射频驱动器4产生如图2所示的频率随时序变化的射频信号，《)^1、^、... 、 fT,,， 从而实现频率编码， 其中 fT,为调制填充光所加的驱动频率， 其余为探测频 率。图 2中，各个探测频率的持续时间为 1微秒，它们是按时序存在的频率脉冲。 射频驱动器 4驱动频率编码器 3， 频率编码器 3选用相位调制器， 它在单频驱动 下的输出的功率谱如图 3所示。图 3中各个光频的间隔等于射频驱动器 4输出的 射频频率，这样， 如图 2所示的时序的射频驱动频率编码器 3对激光器 1发出的 一路激光进行调制，将获得功率谱随时序变化的光谱， 从而实现对探测光频率的 编码。 The RF driver 4 generates a radio frequency signal whose frequency changes with time as shown in FIG. 2, ")^1, ^, ..., f T , , to achieve frequency coding, where f T is added for modulation fill light. Drive frequency, the rest is the probe frequency. In Figure 2, the duration of each detection frequency is 1 microsecond, which is a frequency pulse that exists in time series. The RF driver 4 drives the frequency encoder 3, and the frequency encoder 3 selects the phase modulator. The power spectrum of the output of the single frequency drive is shown in FIG. The spacing of the optical frequencies in FIG. 3 is equal to the RF frequency output by the RF driver 4, such that the RF driving frequency encoder 3 of the timing shown in FIG. 2 modulates one laser emitted by the laser 1, and the power spectrum is changed with time. The spectrum, which enables the encoding of the frequency of the probe light.
与图 2的射频调制谱对应，频率编码器 3产生探测频率脉冲光和与之在时序 上互补的填充光脉冲，接着，探测脉冲光和填充光脉冲接入环形器 5的第一端口， 从环形器 5的第二端口输出经光接口 6注入到多中继放大的光纤通信线路； 探测频率脉冲光和填充光脉冲在被测光纤中的背向瑞利散射信号返回，经所 述环形器 5的第三端口接入光滤波器 7;  Corresponding to the radio frequency modulation spectrum of FIG. 2, the frequency encoder 3 generates the detection frequency pulse light and the timing-complementary filling light pulse, and then the detection pulse light and the filling light pulse enter the first port of the circulator 5, from The second port output of the circulator 5 is injected through the optical interface 6 into the multi-relay amplified optical fiber communication line; the detection frequency pulse light and the filling optical pulse are returned back to the Rayleigh scattering signal in the optical fiber to be tested, through the circulator The third port of 5 is connected to the optical filter 7;
光滤波器 7滤出的探测光信号进入第二耦合器 8与本振光（即从第一耦合器 2分出来的另一路激光）混合， 二者混合产生的中频信号被光电探测器 9接收并 输出对应的中频电信号，各个探测频率对应的中频分别为 ΔΩ，ΔΩ，Δβ， ... ,Αΐη, 如图 4所示。  The probe light signal filtered by the optical filter 7 enters the second coupler 8 and is mixed with the local oscillator light (ie, the other laser light branched from the first coupler 2), and the intermediate frequency signal generated by the mixing of the two is received by the photodetector 9. And output corresponding corresponding intermediate frequency electrical signals, the intermediate frequencies corresponding to the respective detection frequencies are ΔΩ, ΔΩ, Δβ, ..., Αΐη, as shown in FIG. 4 .
中频信号经中频放大器 10放大以便于模数转换模块 11进行高精度的模数转 换， 模数转换模块 11 可选数据采集卡， 采集到的数据传输给信号处理模块 12 进行数据处理， 信号处理模块 12对数字信号进行数字带通滤波以分别提取各探 测频率，再对每个探测频率进行数字下变频和数字低通滤波从而最终得到探测信 号的功率， 然后， 对多次测量的结果进行叠加从而降低测量的随机噪声， 这样， 各个探测频率脉冲对应的光时域反射曲线如图 4所示， 信号处理模块 12接着将 各个探测频率脉冲对应的探测曲线进行时序对齐和叠加，其最终的数据通过显示 模块 13显示， 以表征光纤通信线路衰减信息的光时域反射曲线， 如图 5所示。  The intermediate frequency signal is amplified by the intermediate frequency amplifier 10 to facilitate high-precision analog-to-digital conversion by the analog-to-digital conversion module 11, and the analog-to-digital conversion module 11 selects a data acquisition card, and the collected data is transmitted to the signal processing module 12 for data processing, and the signal processing module 12 digitally bandpass filtering the digital signals to extract the respective detection frequencies, and then digitally down-converting and digitally low-pass filtering each of the detection frequencies to finally obtain the power of the detection signals, and then superimposing the results of the multiple measurements. The measured random noise is reduced, so that the optical time domain reflection curves corresponding to the respective detection frequency pulses are as shown in FIG. 4, and the signal processing module 12 then sequentially aligns and superimposes the detection curves corresponding to the respective detection frequency pulses, and the final data passes. The display module 13 displays an optical time domain reflectance curve that characterizes the attenuation information of the fiber optic communication line, as shown in FIG.
本发明与同类商用设备 MW90010A相比， 从同一激光光源就可获得探测光 脉冲和填充光脉冲，而无需单独使用填充光光源和脉冲调制器就可获得填充光脉 冲， 而且， 由于对探测光频率按时序进行了编码， 每个探测频率对应了一条探测 曲线，多条探测曲线叠加平均的结果能更加快速地降低探测曲线的衰落噪声并提 升测量的动态范围。  Compared with the similar commercial equipment MW90010A, the invention can obtain the detection light pulse and the filling light pulse from the same laser light source, without using the filling light source and the pulse modulator alone to obtain the filling light pulse, and, due to the detection light frequency Encoded in time series, each detection frequency corresponds to a detection curve, and the superimposed average results of multiple detection curves can reduce the fading noise of the detection curve and improve the dynamic range of the measurement more quickly.
最后应当说明的是：以上实施例仅用以说明本发明的技术方案而非对其限制 尽管参照上述实施例对本发明进行了详细的说明，所属领域的普通技术人员应当 理解： 依然可以对本发明的具体实施方式进行修改或者等同替换， 而未脱离本发 明精神和范围的任何修改或者等同替换，其均应涵盖在本发明的权利要求范围当 中。  Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to be limiting thereof. Although the present invention has been described in detail with reference to the embodiments thereof, those of ordinary skill in the art DETAILED DESCRIPTION OF THE INVENTION Modifications or equivalents are intended to be included within the scope of the appended claims.

Claims

权 利 要 求 Rights request
1.一种基于探测频率编码的相干光时域反射仪， 其特征在于， 所述相干光时 域反射仪包括： 激光器 （1 ) 、 第一耦合器 （2) 、 频率编码器 （3 ) 、 射频驱动 器 （4) 、 环形器 （5) 、 光接口 （6) 、 光滤波器 （7) 、 第二耦合器 （8) 、 光 电探测器（9) 、 射频放大器（10) 、 模数转换模块（11 ) 、 信号处理模块（12) 和显示模块 （13 ) ； A coherent optical time domain reflectometer based on detection frequency encoding, wherein the coherent optical time domain reflectometer comprises: a laser (1), a first coupler (2), a frequency encoder (3), RF driver ( 4 ), circulator (5), optical interface (6), optical filter (7), second coupler (8), photodetector (9), RF amplifier (10), analog to digital conversion module (11), signal processing module (12) and display module (13);
所述激光器 （1 ) 发出的激光被所述第一耦合器 （2) 分成两路， 一路输入所 述频率编码器 （3 ) ， 而另一路直接输入所述第二耦合器 （8) ；  The laser light emitted by the laser (1) is divided into two paths by the first coupler (2), one input to the frequency encoder (3), and the other input directly to the second coupler (8);
所述射频驱动器 （4) 产生频率随时序变化的射频信号驱动所述频率编码器 (3 ) ， 所述频率编码器（3 )调制入射光产生探测频率编码的脉冲光和与之在时 序上互补的填充光脉冲；所述探测频率脉冲光和所述填充光脉冲输入所述环形器 The RF driver (4) generates a frequency encoder with a frequency varying with time series to drive the frequency encoder (3), and the frequency encoder (3) modulates incident light to generate pulsed light encoded by the detection frequency and is complementary in timing Filling light pulse; the detecting frequency pulse light and the filling light pulse are input to the circulator
(5 ) 的第一端口， 并从所述环形器 （5) 的第二端口输出， 经所述光接口 （6) 注入到被测光纤通信线路； a first port of (5), and outputted from the second port of the circulator (5), injected into the optical fiber communication line under test via the optical interface (6);
所述探测频率脉冲光和所述填充光脉冲在被测光纤中的背向瑞利散射信号 返回， 经所述环形器 （5) 的第三端口输入所述光滤波器 （7) ；  The detection frequency pulse light and the filling light pulse are returned to the Rayleigh scattering signal in the fiber under test, and the optical filter (7) is input through the third port of the circulator (5);
所述光滤波器 （7) 滤出的探测光信号进入所述第二耦合器 （8) 与本振光混 合， 二者混合产生的中频信号被所述光电探测器 （9) 接收并输出对应的中频信 号；  The probe light signal filtered by the optical filter (7) enters the second coupler (8) and is mixed with the local oscillator light, and the intermediate frequency signal generated by the mixing of the two is received by the photodetector (9) and output corresponding Intermediate frequency signal;
所述中频信号经所述中频放大器 （10) 放大后由所述模数转换模块 （11 ) 进 行采集， 采集到的数据传输给所述信号处理模块（12)进行数据处理， 并通过所 述显示模块 （13 ) 显示表征光纤通信线路衰减特征的光时域反射曲线。  The intermediate frequency signal is amplified by the intermediate frequency amplifier (10) and collected by the analog to digital conversion module (11), and the collected data is transmitted to the signal processing module (12) for data processing, and the display is performed through the display. Module (13) displays an optical time domain reflectance curve characterizing the attenuation characteristics of the fiber optic communication line.
2.如权利要求 1所述的相干光时域反射仪， 其特征在于， 所述相干光时域反 射仪包括设置在所述频率编码器（3 )和环形器（5)之间的扰偏器（14) ， 用于 抑制偏振噪声。  2. A coherent optical time domain reflectometer according to claim 1 wherein said coherent optical time domain reflectometer comprises a scrambling bias disposed between said frequency encoder (3) and said circulator (5) (14) for suppressing polarization noise.
3.如权利要求 2所述的相干光时域反射仪， 其特征在于， 所述相干光时域反 射仪包括设置在所述扰偏器（14)和环形器（5)之间的掺铒光纤放大器（15) ， 用于提升探测频率脉冲光的功率， 进而提高测量的动态范围。  3. A coherent optical time domain reflectometer according to claim 2, wherein said coherent optical time domain reflectometer comprises erbium doped between said scrambler (14) and circulator (5) A fiber amplifier (15) is used to boost the power of the pulsed light at the detection frequency, thereby increasing the dynamic range of the measurement.
4.如权利要求 1所述的相干光时域反射仪，其特征在于，所述频率编码器（3 ) 选用电光相位调制器。 4. A coherent optical time domain reflectometer according to claim 1 wherein said frequency encoder (3) is an electro-optic phase modulator.
5.如权利要求 1所述的相干光时域反射仪，其特征在于，所述频率编码器（3 ) 选用电光强度调制器。 The coherent optical time domain reflectometer according to claim 1, characterized in that the frequency encoder (3) is an electro-optic intensity modulator.
6.如权利要求 1所述的相干光时域反射仪，其特征在于，所述射频驱动器（4) 选用任意波形发生器， 用于产生频率随时序变化的射频信号。  6. The coherent optical time domain reflectometer according to claim 1, wherein the radio frequency driver (4) selects an arbitrary waveform generator for generating a radio frequency signal whose frequency changes with time.
7.如权利要求 1所述的相干光时域反射仪， 其特征在于， 所述光滤波器 （7) 选用光纤光栅。  The coherent optical time domain reflectometer according to claim 1, wherein the optical filter (7) is a fiber grating.
8.如权利要求 1所述的相干光时域反射仪，其特征在于，所述光电探测器（9) 选用平衡光电探测器， 用于提升探测灵敏度。  The coherent optical time domain reflectometer according to claim 1, wherein the photodetector (9) is a balanced photodetector for improving detection sensitivity.
9.如权利要求 1所述的相干光时域反射仪， 其特征在于， 所述模数转换模块 The coherent optical time domain reflectometer according to claim 1, wherein the analog to digital conversion module
( 11 ) 选用数据采集卡， 用于将模拟的中频信号转换成数字信号。 (11) A data acquisition card is selected for converting the analog intermediate frequency signal into a digital signal.
10.如权利要求 1所述的相干光时域反射仪， 其特征在于， 所述信号处理模块 The coherent optical time domain reflectometer according to claim 1, wherein the signal processing module
( 12) 包括 FPGA芯片， 用于处理数字信号。 (12) Includes an FPGA chip for processing digital signals.
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