WO2019169934A1 - 一种高动态范围光时域反射的检测方法和装置 - Google Patents

一种高动态范围光时域反射的检测方法和装置 Download PDF

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WO2019169934A1
WO2019169934A1 PCT/CN2018/123408 CN2018123408W WO2019169934A1 WO 2019169934 A1 WO2019169934 A1 WO 2019169934A1 CN 2018123408 W CN2018123408 W CN 2018123408W WO 2019169934 A1 WO2019169934 A1 WO 2019169934A1
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light
laser
raman
otdr
detecting
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French (fr)
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周琪
卜勤练
熊涛
付成鹏
张建涛
余春平
乐孟辉
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Accelink Technologies Co Ltd
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Accelink Technologies Co Ltd
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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
    • G01M11/3127—Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR using multiple or wavelength variable input source
    • 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
    • G01M11/319—Reflectometers using stimulated back-scatter, e.g. Raman or fibre amplifiers

Definitions

  • the present invention relates to the field of optical time domain reflectometry, and in particular to a method and apparatus for detecting high dynamic range optical time domain reflection.
  • optical time domain reflectometry is usually used to test optical fiber characteristics.
  • the OTDR is also an important device in the online monitoring system in the optical communication network, and the dynamic range is one of the important technical indicators of the OTDR. The larger the dynamic range of the OTDR, the longer the distance of the optical communication line that can be monitored.
  • the working principle of the OTDR is to analyze the characteristics of the length, attenuation, and event of the fiber by detecting the energy distribution curve of the Rayleigh backscattered light over the fiber line over time.
  • the OTDR transmits a detection light pulse to the fiber to be tested, the light pulse is transmitted forward in the fiber, and Rayleigh backscattered light is generated.
  • a reflective event occurs, Fresnel reflected light is also generated.
  • Continuously high-speed sampling of these returned signals can obtain a measurement curve reflecting characteristics such as fiber attenuation and failure by changing the signal power.
  • the dynamic range determines the length of the fiber that can be measured by the OTDR device.
  • Dynamic range and signal to noise ratio are closely related. When the signal-to-noise ratio is too low, the valid information is overwhelmed by noise and cannot be acquired.
  • the prior art generally improves the signal to noise ratio by selecting a higher power laser.
  • the power of a single laser cannot be increased indefinitely, and too high laser power can cause nonlinearity in the fiber and affect the performance of the OTDR. Therefore, after the high-power laser has been selected, how to further improve the dynamic range has high research value.
  • U.S. Patent No. 9,949,484 proposes a scheme for performing OTDR measurement in an optical path including a Raman amplifier, but this scheme transmits a single Raman amplified optical pulse only when the OTDR detecting laser transmits a light pulse, the principle of which is mainly The forward Raman pump amplifies and detects the light pulse, which has a very limited effect on the dynamic range improvement.
  • the solution has a problem that the front end curve is gentler than the back end curve and the absolute value of the slope is smaller, that is, the front end caused by the Raman amplifier is not given.
  • a solution to measuring distortion of the curve This problem can lead to the inability to obtain accurate information of the front-end fiber through the measurement results, which has a serious impact on the overall performance of the product.
  • the technical problem to be solved by the embodiments of the present invention is how to improve the dynamic range of the OTDR detection, thereby improving the distance of the OTDR detection fiber.
  • the present invention provides a high dynamic range optical time domain reflection detecting apparatus, including a Raman laser, an OTDR detecting laser, a wavelength division multiplexer WDM, a control module, a light receiving and optical signal processing module, and a circulator ,specific:
  • the Raman laser and the OTDR detecting laser are respectively connected to the WDM, and the light exit port of the WDM is connected to the illuminator entrance port, and the pulse light emitted by the Raman laser and the OTDR detecting laser is combined by WDM and then The I/O optical port of the circulator enters the fiber to be detected;
  • the light receiving and optical signal processing module is connected to the light exit port of the circulator for obtaining Rayleigh backscattered light and/or Fresnel reflected light returned in the fiber to be detected; the light receiving and optical signal processing module further Connecting the control module, configured to send reflected light related information to the control module;
  • the control module is connected to a driving pin of the Raman laser for controlling the Raman laser to emit at least two light pulses with time intervals in one detection time period according to the reflected light related information.
  • control module further includes a digital signal processing module, specifically:
  • the digital signal processing module is configured to connect the light receiving and optical signal processing module, and is configured to analyze the far end information of the optical fiber according to Rayleigh backscattered light and/or Fresnel reflected light related information; Feedback to the control module.
  • control module is specifically an FPGA, a single chip or a microprocessor; and the digital signal processing module is specifically a DSP.
  • the detecting device further comprises a display, specifically:
  • the display is coupled to the digital signal processing module or the display is coupled to the controller for displaying an analysis result of the detection device.
  • the Raman laser is specifically a cascaded Raman laser composed of at least two stages.
  • the level difference of the Raman lasers of the cascaded Raman lasers is 12 THz-13 THz.
  • the present invention further provides a method for detecting a high dynamic range optical time domain reflection, wherein the control module is configured to control the working state of the Raman laser and the OTDR detecting laser, and is also used for obtaining a reflected back in the fiber to be detected.
  • Optical signals, detection methods include:
  • the Raman laser and the OTDR detecting laser send the Raman pulse laser and the OTDR detecting optical signal to the optical fiber to be detected according to preset configuration parameters;
  • the Raman laser transmits the Raman pulse laser again to the fiber to be detected.
  • the detection period of an OTDR detection signal is determined according to one or more of the number of nodes in the optical fiber to be detected, the bandwidth of the detection signal, and the processing speed of the control module, and the detection period of the one OTDR detection signal is specifically Nms.
  • the preset time period is an Mms time after the OTDR detection signal is transmitted from the current round detection period; wherein, Mms takes a value from the interval [0, N/2].
  • the preset time period is specifically within 1 ⁇ 0.2 ms after the OTDR detection signal is transmitted.
  • the preset threshold is specifically:
  • the calculation condition of the Rayleigh backscattered light and/or Fresnel reflected light acquired during the detection period of an OTDR detection signal the calculation condition of the 3-5 dB drop from the highest value at the time of initial reception is calculated.
  • the multi-pulse solution of the present invention can not only detect the optical pulse by the forward Raman optical pulse amplification, but also continuously transmit the plurality of Raman optical pulses through the Raman laser to directly amplify the detection light pulse after the OTDR detection laser is turned off. Backward to the Rayleigh scattered light signal and / or Fresnel reflected light signal.
  • the direction of the Raman light pulse in the fiber is opposite to that of the Rayleigh backscattered light signal, but it can still amplify the Rayleigh backscattered light signal.
  • the next Raman light pulse is transmitted for amplification, thereby causing the back Rayleigh scattered light signal and/or
  • the power of the Fresnel reflected light signal is always maintained at a high level at the front end of the fiber, which provides guarantee for ultra-long-distance fiber measurement.
  • the splicing method provided by the present invention combines the near-end information obtained by the conventional OTDR measurement with the far-end information measured by the Raman amplifier, and solves the distortion problem of the front-end curve slope which is not solved in US9494484. , improve the accuracy of the measurement results.
  • FIG. 1 is a schematic structural diagram of a device for detecting a high dynamic range optical time domain reflection according to an embodiment of the present invention
  • FIG. 2 is a schematic structural view of a circulator according to an embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a device for detecting a high dynamic range optical time domain reflection in an exemplary embodiment according to an embodiment of the present invention
  • FIG. 4 is a schematic structural diagram of a device for detecting a high dynamic range optical time domain reflection after extending a function module according to an embodiment of the present invention
  • FIG. 5 is a schematic flowchart of a method for detecting a high dynamic range optical time domain reflection according to an embodiment of the present invention
  • FIG. 6 is a schematic flowchart of a method for detecting a high dynamic range optical time domain reflection in a specific example environment according to an embodiment of the present invention
  • FIG. 7 is a graph showing measurement results of a Raman laser provided by an embodiment of the present invention.
  • FIG. 8 is a diagram of measurement results obtained in a detection method according to an embodiment of the present invention.
  • FIG. 9 is a diagram showing measurement results obtained when the detection method of the embodiment of the present invention is provided according to an embodiment of the present invention.
  • Embodiment 1 of the present invention provides a high dynamic range optical time domain reflection detecting device, as shown in FIG. 1 , including a Raman laser, an optical time domain reflectometry (OTDR) detecting laser, and a wave.
  • Wavelength Division Multiplexing (WDM), control module, optical receiving and optical signal processing module, and circulator specific:
  • the Raman laser and the OTDR detecting laser are respectively connected to the WDM, and the light exit of the WDM is connected to the illuminator entrance port (the circulator used in the device in FIG. 1 is separately presented to show the interface distribution thereof, and the corresponding distribution structure As shown in FIG. 2, the pulsed light emitted by the Raman laser and the OTDR detecting laser is combined by WDM and then enters the optical fiber to be detected through the I/O optical port of the circulator (as shown in FIG. 2);
  • the light receiving and optical signal processing module is connected to the light exit port of the circulator for obtaining Rayleigh backscattered light and/or Fresnel reflected light returned in the fiber to be detected; the light receiving and optical signal processing module further
  • the control module is connected to send the reflected light related information to the control module.
  • the optical receiving and optical signal processing module includes an optical filtering and a circuit filtering function, configured to perform photoelectric conversion and noise filtering processing on the received reflected light signal, and send the processed reflected light related information to the control module.
  • the reflected light related information includes: optical power intensity, light intensity distribution, receiving time, and the like of Rayleigh backscattered light and/or Fresnel reflected light.
  • the control module is configured to control a driving pin of the Raman laser, and control the Raman laser to emit at least two light pulses with time intervals in one detection time period according to the reflected light related information.
  • the optical pulse can be amplified by the forward Raman optical pulse amplification, and the Raman laser can continue to transmit multiple Raman optical pulses to directly amplify the detection light after the OTDR detection laser is turned off.
  • the back-direction Rayleigh scattered light signal and/or Fresnel reflected light signal produced by the pulse can be amplified by the forward Raman optical pulse amplification, and the Raman laser can continue to transmit multiple Raman optical pulses to directly amplify the detection light after the OTDR detection laser is turned off.
  • the back-direction Rayleigh scattered light signal and/or Fresnel reflected light signal produced by the pulse can be amplified by the forward Raman optical pulse amplification, and the Raman laser can continue to transmit multiple Raman optical pulses to directly amplify the detection light after the OTDR detection laser is turned off.
  • the back-direction Rayleigh scattered light signal and/or Fresnel reflected light signal produced by the pulse can be amplified by the forward Raman optical pulse a
  • the direction of the Raman light pulse in the fiber is opposite to that of the Rayleigh backscattered light signal, but it can still amplify the Rayleigh backscattered light signal.
  • the next Raman light pulse is transmitted for amplification, thereby causing back Rayleigh scattered light.
  • the power of the signal and/or Fresnel reflected light signal is always maintained at a high level at the front end of the fiber, providing protection for ultra-long-distance fiber measurements.
  • control module in the instantiation solution further includes a digital signal processing module, specifically:
  • the digital signal processing module is configured to connect the light receiving and optical signal processing module, and is configured to analyze the far end information of the optical fiber according to Rayleigh backscattered light and/or Fresnel reflected light related information; Feedback to the control module.
  • the digital signal processing module may be embodied as a DSP, and the control core of the corresponding control module may be implemented by using an FPGA, a single chip, or a PC.
  • the detecting device further comprises a display, specifically:
  • the display is coupled to the digital signal processing module or the display is coupled to the controller for displaying an analysis result of the detection device.
  • Cascaded Raman fiber lasers have the advantages of long gain medium, low noise, wide tuning range, simultaneous multi-wavelength output and high coupling efficiency with fiber.
  • Cascaded Raman fiber lasers for pumping fiber Raman amplifiers provide flat amplification over a wide bandwidth and are ideal pump sources for fiber Raman amplifiers.
  • a multi-wavelength output cascaded Raman fiber laser is used as a signal source for fiber-optic communication systems, especially for wavelength division multiplexing systems, which can reduce the number of lasers at the transmitting end. Therefore, in combination with the embodiments of the present invention, the further Raman laser can be implemented in a cascade manner.
  • Embodiment 2 of the present invention further provides a method for detecting a high dynamic range optical time domain reflection, in which the detection method is It is required to implement basic connection characteristics, wherein the control module is used to control the working state of the Raman laser and the OTDR detecting laser, and is also used to obtain an optical signal reflected from the fiber to be detected (compared with the above connection characteristics, this is known
  • the corresponding detection method of the invention can also be implemented by the detecting device described in Embodiment 1, as shown in FIG. 5, the detecting method includes:
  • step 201 the Raman laser and the OTDR detecting laser send the Raman pulse laser and the OTDR detection optical signal to the optical fiber to be detected according to preset configuration parameters.
  • step 202 the control module detects that the returned Rayleigh backscattered light and/or the Fresnel reflected light intensity is less than a preset threshold in a detection period of an OTDR detection signal.
  • the Raman laser is controlled to transmit the Raman pulse laser again to the fiber to be detected.
  • the optical pulse can be amplified by the forward Raman optical pulse amplification, and the Raman laser can continue to transmit multiple Raman optical pulses to directly amplify the detection light after the OTDR detection laser is turned off.
  • the back-direction Rayleigh scattered light signal and/or Fresnel reflected light signal produced by the pulse can be amplified by the forward Raman optical pulse amplification, and the Raman laser can continue to transmit multiple Raman optical pulses to directly amplify the detection light after the OTDR detection laser is turned off.
  • the back-direction Rayleigh scattered light signal and/or Fresnel reflected light signal produced by the pulse can be amplified by the forward Raman optical pulse amplification, and the Raman laser can continue to transmit multiple Raman optical pulses to directly amplify the detection light after the OTDR detection laser is turned off.
  • the back-direction Rayleigh scattered light signal and/or Fresnel reflected light signal produced by the pulse can be amplified by the forward Raman optical pulse a
  • the pulse width of the optical pulse transmitted by the Raman laser and the time interval between the pulses may be equal or unequal.
  • the specific number of pulses, the width of each pulse, and the time interval of each pulse can be adjusted according to the actual light receiving and the optical signal power received by the optical signal processing module, thereby achieving better results.
  • the above parameters can be obtained by the existing Raman mechanism amplification principle and multiple test experiments in the implementation of the present invention, and are not described herein again.
  • the concept of the detection period of the OTDR detection signal proposed in the embodiment of the present invention is further provided for the technical solution of how to implement the OTDR detection signal in the specific application scenario. Clear explanation and qualification.
  • the detection period of an OTDR detection signal is determined according to one or more of the number of nodes in the optical fiber to be detected, the bandwidth of the detection signal, and the processing speed of the control module, and the number of nodes in the optical fiber is represented as a branch, a relay, and the like. Etc. To some extent, it will increase the complexity of the analysis.
  • the preset time period is from the current round detection period, and the Mms time after transmitting the OTDR detection signal; wherein, Mms is from the interval [0, N/2] Value, where M and N are the corresponding time parameter values.
  • the principle is that the reflected light signal in the Mms period is not used to resolve the node problem existing in the fiber to be tested, but is only used to judge the attenuation of the reflected light signal; and correspondingly, in [M, The Raman pulse laser is not emitted during the period of N], in order to avoid the emission of the Raman pulsed laser generated by the control module, the normal analysis of the reflected light signal by the control module, and the process of analyzing the node problem existing in the fiber to be tested, usually When performing normal reflected light signal analysis, it is first determined whether the detected light signal is emitted into the fiber to be tested to form reflected light, and whether the linear factor reaches a preset threshold (for example, -0.95), and when it is reached, the Raman pulse light is indicated.
  • a preset threshold for example, -0.95
  • the effect of the signal on the reflected light signal is negligible.
  • the detection period of the OTDR detection signal is 4 ms ⁇ 1 s
  • the preset time period is specifically within 1 ⁇ 0.2 ms after the OTDR detection signal is transmitted. For example, if the time interval between two detection pulses is 4ms, the Raman light pulse should not be transmitted within 1ms to 4ms after a detection pulse is transmitted. If the Raman laser is continuously illuminated without interruption, the huge noise generated will have a negative impact on the signal-to-noise ratio, thereby reducing the dynamic range of the OTDR.
  • the preset threshold in addition to the detection cycle characteristics of the OTDR detection signal explained above, there is also a key technical element, that is, the preset threshold, which will be described in more detail next.
  • the preset threshold value is a parameter value calculated according to a preset condition or a preset rule. Specifically, the preset threshold value is obtained according to an detection period of an OTDR detection signal.
  • the optical power of the Rayleigh backscattered light and/or Fresnel reflected light is calculated from the calculation condition that the maximum value at the time of initial reception is decreased by 3-5 dB. During the design and testing of the experimental protocol, it was preferred to use 3 dB.
  • the embodiment of the present invention combines the detection method described in Embodiment 2 with the detection device described in Embodiment 1, and provides a method for implementing the method of Embodiment 2 in the detection device of Embodiment 1, as shown in FIG.
  • the method includes:
  • step 301 the output ports of the Raman laser and the OTDR laser are combined by WDM and incident on the optical fiber to be tested through the circulator.
  • the circulator is coupled to the optical receiving and optical signal processing module to convert the returned optical signal into a digital electrical signal, and the output signal is coupled to the digital signal processor processing module and display.
  • the optical connection and optical signal processing module should include filters, avalanche photodiodes (APD), amplifiers and analog-to-digital converters.
  • the filter can filter out the noise in the returned light.
  • the APD converts the optical signal into an electrical signal. After amplification by the amplifier, the analog electrical signal is converted into a digital electrical signal by an analog-to-digital converter.
  • Step 302 The control module sends a driving signal to the OTDR laser, so that the OTDR laser sends the detecting light pulse.
  • the measurement information of the near-end fiber can be obtained by the optical receiving and optical signal processing module and the digital signal processing module.
  • Step 303 The control module sends a driving signal to the OTDR laser, so that the OTDR laser sends the detecting light pulse.
  • a driving signal is sent to the Raman laser through the control module to successively transmit a plurality of amplified light pulses.
  • the next Raman light pulse should be transmitted when the light power received by the light receiving and optical signal processing module is reduced to a certain level.
  • the power at which the Rayleigh backscatter power received by the light receiving and optical signal processing module is decreased by 3 dB from the highest value is used as a reference for transmitting the next Raman light pulse.
  • the pulse width of the Raman light pulse should not be too long, and the number should not be too much, so as not to affect the transmission of the normal detection pulse in the next round.
  • one quarter of the time interval of two adjacent detection light pulses is used as a flag for stopping the transmission of the Raman light pulse.
  • the Raman light pulse should not be transmitted within 1 ms to 4 ms after the transmission of one detection pulse. If the Raman laser is continuously illuminated, the large noise generated will have a negative impact on the signal-to-noise ratio, thereby reducing the dynamic range of the OTDR (as shown in Figure 7, the dynamic range is about 15 dB).
  • the control module can be implemented using FPGA-like devices.
  • the measurement information of the far-end optical fiber can be obtained through the optical receiving and optical signal processing module and the digital signal processing module. In actual operation, step 302 and step 303 are not required in sequence, that is, the Raman laser can be turned off to measure the near-end fiber, or the Raman laser can be driven to measure the far-end fiber.
  • Step 304 Integrate and analyze the remote fiber measurement information and the near-end fiber measurement information by the digital signal processing module to obtain the measurement result of the whole segment fiber, and display it through the display, as shown in FIG. 8 .
  • the fiber tail reflection event at a distance of up to 245 km is also clearly displayed.
  • the dynamic range of the OTDR has exceeded 51dB.
  • the digital signal processing algorithm such as denoising and event recognition can be used to process the measurement result, thereby more clearly and accurately determining the event occurring on the optical fiber.
  • the frequency difference of the adjacent multi-stage laser should be kept at about 13 THz (for example, 12 THz-13 THz).
  • the longer the wavelength of the laser is The set rated power will be correspondingly higher.
  • control module may select an FPGA or the like as a main device, and the digital signal processing module may select a DSP or the like as a main device.
  • the detected light pulse width in step 301 can be narrower than the detected light pulse in step 302 to ensure the resolution of the near measurement result.
  • the widest pulse width should be no more than 20 ⁇ s.

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Abstract

本发明涉及光时域反射仪技术领域，提供了一种高动态范围光时域反射的检测方法和装置。其中装置包括拉曼激光器和OTDR检测激光器分别连接WDM，WDM的出光口连接环形器入光口；光接收和光信号处理模块连接环形器的出光口；光接收和光信号处理模块还连接控制模块；控制模块用于控制拉曼激光器的驱动引脚，并根据反射光相关信息，控制拉曼激光器在一个检测时间周期内发出至少两个具有时间间隔的光脉冲。本发明的多脉冲解决方案，既可以通过正向拉曼光脉冲放大检测光脉冲，又可以在OTDR检测激光器关闭后通过拉曼激光器继续发送多个拉曼光脉冲直接放大检测光脉冲所产生的背向瑞利散射光信号和/或菲涅尔反射光信号。

Description

一种高动态范围光时域反射的检测方法和装置 【技术领域】
本发明涉及光时域反射仪技术领域，特别是涉及一种高动态范围光时域反射的检测方法和装置。
【背景技术】
当前，世界各国的通信网络主要是以光纤为传输基础，而在建设和维护光缆线路时，通常会使用光时域反射仪(OTDR)来进行光纤特性的测试。OTDR同时也是光通信网络中在线监测系统中的重要装置，而动态范围则是OTDR的重要技术指标之一。OTDR的动态范围越大，则可以监测的光通信线路的距离也越长。
OTDR的工作原理是通过检测脉冲激光在光纤线路上的瑞利背向散射光随时间的能量分布曲线来分析得到光纤的长度、衰减、事件等特性。当OTDR向待测光纤中发射一个检测光脉冲后，光脉冲在光纤中向前传输的同时，会产生瑞利背向散射光。有反射型事件发生时，还会产生菲涅尔反射光。连续高速采样出这些返回的信号可以通过信号功率的变化情况，得到反映光纤衰减、故障等特征的测量曲线。而动态范围则决定了OTDR装置最远能测量到的光纤长度。
动态范围和信噪比有密切关系。当信噪比过低时，有效信息被噪声淹没而无法获取。现有技术通常通过选择功率更高的激光器的方式来提高信噪比。但由于工艺水平的限制，单个激光器的功率不可能无限提高，且过高的激光器功率会导致光纤中产生非线性从而影响OTDR的性能。因此，在已经选择了高功率的激光器后，如何进一步提高动态范围，具有很高的研究价值。
美国专利US9494484提出的是一种在含拉曼放大器的光路中进行OTDR测量的方案，但该方案仅仅在OTDR检测激光器发送光脉冲时才发送一个单独的拉曼放大光脉冲，其原理主要是通过正向拉曼泵浦放大检测光脉冲，对动态范 围的提升效果非常有限，而且该方案存在前端曲线比后端曲线平缓，斜率绝对值更小的问题，即没有给出拉曼放大器导致的前端测量曲线失真的解决方法。该问题会导致无法通过测量结果获得前段光纤的准确信息，从而对产品的总体性能产生较为严重的影响。
【发明内容】
本发明实施例要解决的技术问题是如何提高OTDR检测的动态范围，从而提高OTDR检测光纤的距离。
本发明实施例采用如下技术方案：
第一方面，本发明提供了一种高动态范围光时域反射的检测装置，包括拉曼激光器、OTDR检测激光器、波分复用器WDM、控制模块、光接收和光信号处理模块，以及环行器，具体的：
拉曼激光器和OTDR检测激光器分别连接所述WDM，所述WDM的出光口连接所述环形器入光口，所述拉曼激光器和OTDR检测激光器发出的脉冲光通过WDM进行合波后经所述环形器的I/O光口进入待检测光纤；
所述光接收和光信号处理模块连接所述环形器的出光口，用于获取待检测光纤中返回的瑞利背向散射光和/或菲涅尔反射光；所述光接收和光信号处理模块还连接所述控制模块，用于将反射光相关信息发送给所述控制模块；
所述控制模块连接拉曼激光器的驱动引脚，用于根据所述反射光相关信息，控制拉曼激光器在一个检测时间周期内发出至少两个具有时间间隔的光脉冲。
优选的，所述控制模块中还包括数字信号处理模块，具体的：
所述数字信号处理模块用于连接光接收和光信号处理模块，用于根据瑞利背向散射光和/或菲涅尔反射光相关信息，分析出光纤远端信息；将所述光纤远端信息反馈给所述控制模块。
优选的，所述控制模块具体为FPGA，单片机或者微处理器；所述数字信号处理模块具体为DSP。
优选的，所述检测装置还包括显示器，具体的：
所述显示器连接所述数字信号处理模块或者，所述显示器连接所述控制器，用于显示检测装置的分析结果。
优选的，所述拉曼激光器具体为的由级数至少为二级构成的级联型拉曼激光器。
优选的，所述级联型拉曼激光器的各级拉曼激光器的频率差为12THz-13THz。
第二方面，本发明还提供了一种高动态范围光时域反射的检测方法，控制模块用于控制所述拉曼激光器和OTDR检测激光器的工作状态，还用于获取待检测光纤中反射回来的光信号，检测方法包括：
拉曼激光器和OTDR检测激光器按照预设的配置参数向待检测光纤发送拉曼脉冲激光和OTDR检测光信号；
控制模块在一个OTDR检测信号的检测周期中，若在预设时间段内所检测到返回的瑞利背向散射光和/或菲涅尔反射光的光强度小于预设阈值时，控制所述拉曼激光器向待检测光纤中再次发送拉曼脉冲激光。
优选的，一个OTDR检测信号的检测周期根据待检测的光纤中节点数量、检测信号的频宽和控制模块处理速度中的一项或者多项决定，所述一个OTDR检测信号的检测周期具体为Nms时，所述预设时间段为从当前轮检测周期中，发射OTDR检测信号后Mms时间内；其中，Mms从区间[0，N/2]中取值。
优选的，在所述OTDR检测信号的检测周期为4ms±1s时，所述预设时间段具体为发送OTDR检测信号后1±0.2ms以内。
优选的，所述预设阈值具体为：
根据在一个OTDR检测信号的检测周期内，获取的瑞利背向散射光和/或菲涅尔反射光的光功率由最初接收到时的最高值下降3-5dB的计算条件，计算得到。
与现有技术相比，本发明实施例的有益效果在于：
本发明的多脉冲解决方案，既可以通过正向拉曼光脉冲放大检测光脉冲，又可以在OTDR检测激光器关闭后通过拉曼激光器继续发送多个拉曼光脉冲直接放大检测光脉冲所产生的背向瑞利散射光信号和/或菲涅尔反射光信号。
根据拉曼放大器的原理，拉曼光脉冲在光纤中的方向与瑞利背向散射光信号方向相反，但仍可以对瑞利背向散射光信号产生放大作用。通过本发明提出的方案，即当接收器接收到的瑞利背向散射光信号低于某一水平时，发送下一个拉曼光脉冲进行放大，从而使背向瑞利散射光信号和/或菲涅尔反射光信号的功率在光纤的前端始终保持在一个较高的水平，为超远距离的光纤测量提供保障。
相对于US9494484的方案有原理上的区别，且效果更为显著。另外，本发明给出的拼接的方法，即将通过常规OTDR测量得到的近端信息和借助拉曼放大器测量得到的远端信息进行拼接，解决了US9494484中没有解决的前端曲线斜率更短的失真问题，提高了测量结果的准确性。
【附图说明】
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它的附图。
图1是本发明实施例提供的一种高动态范围光时域反射的检测装置的结构示意图；
图2是本发明实施例所描述的环形器结构布局示意图；
图3是本发明实施例提供的一种实例场合中更详尽的高动态范围光时域反射的检测装置的结构示意图；
图4是本发明实施例提供的一种扩展功能模块后的高动态范围光时域反射的检测装置的结构示意图；
图5是本发明实施例提供的一种高动态范围光时域反射的检测方法流程示意图；
图6是本发明实施例提供的具体实例环境中高动态范围光时域反射的检测方法的流程示意图；
图7是本发明实施例提供的拉曼激光器持续发光时的测量结果图；
图8是本发明实施例提供的检测方法中所获得的测量结果图；
图9是本发明实施例提供的为采用本发明实施例检测方法时所获得的测量结果图。
【具体实施方式】
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
在本发明的描述中，术语“内”、“外”、“纵向”、“横向”、“上”、“下”、“顶”、“底”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明而不是要求本发明必须以特定的方位构造和操作，因此不应当理解为对本发明的限制。
此外，下面所描述的本发明各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
实施例1：
本发明实施例1提供了一种高动态范围光时域反射的检测装置，如图1所示，包括拉曼激光器、光时域反射仪(Optical Time Domain Reflect-ometry，OTDR)检测激光器、波分复用器(Wavelength Division Multiplexing，简写为：WDM)、控制模块、光接收和光信号处理模块，以及环行器，具体的：
拉曼激光器和OTDR检测激光器分别连接所述WDM，所述WDM的出光口连接所述环形器入光口(图1中装置所使用的环形器被单独提出来展示其接口分布时，相应分布结构如图2所示)，所述拉曼激光器和OTDR检测激光器发出的脉冲光通过WDM进行合波后经所述环形器的I/O光口(如图2所示)进入待检测光纤；
所述光接收和光信号处理模块连接所述环形器的出光口，用于获取待检测光纤中返回的瑞利背向散射光和/或菲涅尔反射光；所述光接收和光信号处理 模块还连接所述控制模块，用于将反射光相关信息发送给所述控制模块。
其中，所述光接收和光信号处理模块包含光学滤波和电路滤波功能，用于对接收到反射光信号进行光电转换和噪音滤除处理，将处理后的反射光相关信息发送给所述控制模块。其中反射光相关信息包括：瑞利背向散射光和/或菲涅尔反射光的光功率强度、光强度分布、接收时间等等。
所述控制模块用于控制拉曼激光器的驱动引脚，并根据所述反射光相关信息，控制拉曼激光器在一个检测时间周期内发出至少两个具有时间间隔的光脉冲。
本发明实施例所提出的多脉冲解决方案，既可以通过正向拉曼光脉冲放大检测光脉冲，又可以在OTDR检测激光器关闭后通过拉曼激光器继续发送多个拉曼光脉冲直接放大检测光脉冲所产生的背向瑞利散射光信号和/或菲涅尔反射光信号。
其中，拉曼光脉冲在光纤中的方向与瑞利背向散射光信号方向相反，但仍可以对瑞利背向散射光信号产生放大作用。通过本发明提出的方案，即当光接收和光信号处理模块接收到的瑞利背向散射光信号低于某一水平时，发送下一个拉曼光脉冲进行放大，从而使背向瑞利散射光信号和/或菲涅尔反射光信号的功率在光纤的前端始终保持在一个较高的水平，为超远距离的光纤测量提供保障。
如图3所示，为结合本发明实施例1所述的检测状态，在具体应用场合下的结构实例化后的示意图。相比较实施例1所述的结构，实例化方案中所述控制模块中还包括数字信号处理模块，具体的：
所述数字信号处理模块用于连接光接收和光信号处理模块，用于根据瑞利背向散射光和/或菲涅尔反射光相关信息，分析出光纤远端信息；将所述光纤远端信息反馈给所述控制模块。其中，所述数字信号处理模块具体可以表现为DSP，而相应的控制模块的控制核心可以通过FPGA、单片机或者PC来实现。
如图4所示，为本发明实施例为提高交互效率，提高操作人员直接从本发明实施例所提出的检测装置中获取有效信息，而无需再外接其它设备的设计思 路，进一步提出的一种改进方案，其中，所述检测装置还包括显示器，具体的：
所述显示器连接所述数字信号处理模块或者，所述显示器连接所述控制器，用于显示检测装置的分析结果。
级联拉曼光纤激光器具有增益介质长、噪声低、调谐范围宽、可同时实现多波长输出和与光纤耦合效率高等优点。级联拉曼光纤激光器用于泵浦光纤拉曼放大器可以在很宽的带宽内实现平坦放大，是光纤拉曼放大器理想的泵浦源。多波长输出的级联拉曼光纤激光器用作光纤通信系统，特别是波分复用系统的信号源，可以减少发射端的激光器数量。因此，结合本发明实施例，进一步的所述拉曼激光器可以采用级联的方式实现。
实施例2：
在提供了实施例1所述的一种高动态范围光时域反射的检测装置后，本发明实施例2还提出了一种高动态范围光时域反射的检测方法，在所述检测方法中需要实现基本的连接特性，其中，控制模块用于控制所述拉曼激光器和OTDR检测激光器的工作状态，还用于获取待检测光纤中反射回来的光信号(相比较上述的连接特性可知，本发明的相应的检测方法也可以被实施例1所阐述的检测装置所实现)，如图5所示，检测方法包括：
在步骤201中，拉曼激光器和OTDR检测激光器按照预设的配置参数向待检测光纤发送拉曼脉冲激光和OTDR检测光信号。
在步骤202中，控制模块在一个OTDR检测信号的检测周期中，若在预设时间段内所检测到返回的瑞利背向散射光和/或菲涅尔反射光的光强度小于预设阈值时，控制所述拉曼激光器向待检测光纤中再次发送拉曼脉冲激光。
本发明实施例所提出的多脉冲解决方案，既可以通过正向拉曼光脉冲放大检测光脉冲，又可以在OTDR检测激光器关闭后通过拉曼激光器继续发送多个拉曼光脉冲直接放大检测光脉冲所产生的背向瑞利散射光信号和/或菲涅尔反射光信号。
在本发明实施例中，拉曼激光器发送的光脉冲的脉宽以及脉冲间的时间间隔可以相等也可以不等。具体脉冲数量、各脉冲的宽度、各脉冲的时间间隔均 可根据实际光接收和光信号处理模块接收到的光信号功率高低而调整，从而达到更好的效果。上述参数，在本发明实现方案中可以通过现有的拉曼机关器放大原理和多次的测试实验得到，在此不再赘述。
在本发明实施例中提出的OTDR检测信号的检测周期的概念，为了能够进一步的提供本发明实施例如何在具体应用场景中实现的技术思路，将对于所述OTDR检测信号的检测周期给予更为明确的解释和限定。其中，一个OTDR检测信号的检测周期根据待检测的光纤中节点数量、检测信号的频宽和控制模块处理速度中的一项或者多项决定，所述光纤中节点数量表现为分支、中继等等，一定程度上会增加分析的复杂度。所述一个OTDR检测信号的检测周期具体为Nms时，所述预设时间段为从当前轮检测周期中，发射OTDR检测信号后Mms时间内；其中，Mms从区间[0，N/2]中取值，其中M和N为相应时间参数值。其原理是，在Mms时间段内的反射光信号不会被用来解析待测光纤中存在的节点问题，而仅用来判断反射光信号的衰减情况；而相应的，之所以在[M，N]时间段内不发射拉曼脉冲激光，是为了避免发射的拉曼脉冲激光产生的发射光对控制模块正常分析反射光信号，解析待测光纤中存在的节点问题的过程产生影响，通常情况下在进行正常的反射光信号分析时，会先确定由检测光信号发射到待测光纤中形成反射光，其线性因子是否达到预设阈值(例如-0.95)，达到了则表明拉曼脉冲光信号对于反射光信号的影响已经可以忽略不计了。以一组参数进行阐述的话，其中，在所述OTDR检测信号的检测周期为4ms±1s时，所述预设时间段具体为发送OTDR检测信号后1±0.2ms以内。例如：如果两个检测脉冲的时间间隔为4ms，则当一个检测脉冲发送后的1ms至4ms内，都不应发送拉曼光脉冲。如果持续不间断地令拉曼激光器发光，产生的巨大噪声反而会对信噪比产生负面影响，从而降低OTDR的动态范围。
在本发明实施例，除了上述解释的OTDR检测信号的检测周期特征外，还有一个关键技术要素，即所述预设阈值，接下来将对其做较为详尽的阐述。
所述预设阈值，更确切的表现是一种根据预设的条件或者预设的规定计算得到的参数值，具体的：所述预设阈值根据在一个OTDR检测信号的检测周期内， 获取的瑞利背向散射光和/或菲涅尔反射光的光功率由最初接收到时的最高值下降3-5dB的计算条件，计算得到。在实验方案设计和测试过程中，得出优选的是采用3dB。
实施例3：
本发明实施例结合了实施例2所述的检测方法和实施例1所述检测装置，提供了一种如何在实施例1所述检测装置中具体实现实施例2所述方法，如图6所示，所述方法包括：
步骤301，将拉曼激光器和OTDR激光器的输出端口通过WDM合波，通过环行器入射进待测光纤。将环行器与光接收和光信号处理模块相连，以将返回的光信号转换为数字电信号，再将输出信号连接至数字信号处理器处理模块和显示屏。
其中，光接波收和光信号处理模块中应包含滤器，雪崩光电二极管(APD)，放大器以及模数转换器等器件。滤波器可以滤除返回光中的噪声，APD将光信号转换为电信号，经放大器放大后，由模数转换器将模拟电信号转换为数字电信号。
步骤302，控制模块向OTDR激光器发送驱动信号，使OTDR激光器发送检测光脉冲。通过光接收和光信号处理模块以及数字信号处理模块，即可得到近端光纤的测量信息。
步骤303，控制模块向OTDR激光器发送驱动信号，使OTDR激光器发送检测光脉冲。通过控制模块向拉曼激光器发送驱动信号，使其陆续发送多个放大光脉冲。
为了达到更好的效果，下一个拉曼光脉冲应在光接收和光信号处理模块接收到的信号光功率降低到某一水平时发送。本说明书所陈述的实施方案中，将光接收和光信号处理模块接收到的瑞利背向散射功率由最高值下降3dB处的功率作为发送下一个拉曼光脉冲的基准。与此同时，拉曼光脉冲的脉宽不宜过长，个数不宜过多，以免影响下一轮正常检测脉冲的发送。本发明实施例中将相邻两个检测光脉冲时间间隔的四分之一作为停止发送拉曼光脉冲的标志。即如果 两个检测脉冲的时间间隔为4ms，则当一个检测脉冲发送后的1ms至4ms内，都不应发送拉曼光脉冲。如果持续不间断地令拉曼激光器发光，产生的巨大噪声反而会对信噪比产生负面影响，从而降低OTDR的动态范围(如图7所示，其动态范围为15dB左右)。控制模块可以使用FPGA类似器件实现。通过光接收和光信号处理模块以及数字信号处理模块，即可得到远端光纤的测量信息。实际操作中，步骤302和步骤303无先后顺序要求，即可以先关闭拉曼激光器测量近端光纤，也可以先驱动拉曼激光器测量远端光纤。
步骤304，通过数字信号处理模块对远端光纤测量信息和近端光纤测量信息进行整合分析，得到全段光纤的测量结果，通过显示器进行显示，如图8所示。图中，距离长达245km处的光纤尾端反射事件也得到了清晰的显示。按照IEC61746-2009单程RMS动态范围定义，该OTDR的动态范围已经超过51dB。和同等条件下不含拉曼放大器所得测量结果附图9相比，动态范围得到了显著的提升。进一步的，在显示器上显示测量结果前，可以通过去噪和事件识别等数字信号处理算法对测量结果进行处理，从而更为清晰准确地判断光纤上发生的事件。
在本发明实施例中多级拉曼激光器中，相邻多级激光器的频率差应该保持在13THz左右(例如：12THz-13THz)，相应的，多级拉曼激光器中，波长越长的激光器为其设定的额定功率相应会越高。
在本发明实施例中，控制模块可以选择FPGA或类似器件作为主要器件，数字信号处理模块可以选择DSP或类似器件作为主要器件。
在本发明实时中，步骤301中的检测光脉冲宽度可以比步骤302中的检测光脉冲窄，以保证近处测量结果的分辨率。为了满足基本的分辨率需求，最宽脉宽应不大于20μs。
值得说明的是，由于检测装置实施例1与本发明的检测方法实施例2基于同一构思，具体内容可相互借鉴，此处不再赘述。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明 的保护范围之内。

Claims (10)

  1. 一种高动态范围光时域反射的检测装置，其特征在于，包括拉曼激光器、OTDR检测激光器、波分复用器WDM、控制模块、光接收和光信号处理模块，以及环行器，具体的：
    拉曼激光器和OTDR检测激光器分别连接所述WDM，所述WDM的出光口连接所述环形器入光口，所述拉曼激光器和OTDR检测激光器发出的脉冲光通过WDM进行合波后经所述环形器的I/O光口进入待检测光纤；
    所述光接收和光信号处理模块连接所述环形器的出光口，用于获取待检测光纤中返回的瑞利背向散射光和/或菲涅尔反射光；所述光接收和光信号处理模块还连接所述控制模块，用于将反射光相关信息发送给所述控制模块；
    所述控制模块连接拉曼激光器的驱动引脚，用于根据所述反射光相关信息，控制拉曼激光器在一个检测时间周期内发出至少两个具有时间间隔的光脉冲。
  2. 根据权利要求1所述的高动态范围光时域反射的检测装置，其特征在于，所述控制模块中还包括数字信号处理模块，具体的：
    所述数字信号处理模块用于连接光接收和光信号处理模块，用于根据瑞利背向散射光和/或菲涅尔反射光相关信息，分析出光纤远端信息；将所述光纤远端信息反馈给所述控制模块。
  3. 根据权利要求2所述的高动态范围光时域反射的检测装置，其特征在于，所述控制模块具体为FPGA，单片机或者微处理器；所述数字信号处理模块具体为DSP。
  4. 根据权利要求1-3任一所述的高动态范围光时域反射的检测装置，其特征在于，所述检测装置还包括显示器，具体的：
    所述显示器连接所述数字信号处理模块或者，所述显示器连接所述控制器，用于显示检测装置的分析结果。
  5. 根据权利要求1-3任一所述的高动态范围光时域反射的检测装置，其特征在于，所述拉曼激光器具体为的由级数至少为二级构成的级联型拉曼激光器。
  6. 根据权利要求5所述的高动态范围光时域反射的检测装置，其特征在于，所述级联型拉曼激光器的各级拉曼激光器的频率差为12THz-13THz。
  7. 一种高动态范围光时域反射的检测方法，其特征在于，控制模块用于控制所述拉曼激光器和OTDR检测激光器的工作状态，还用于获取待检测光纤中反射回来的光信号，检测方法包括：
    拉曼激光器和OTDR检测激光器按照预设的配置参数向待检测光纤发送拉曼脉冲激光和OTDR检测光信号；
    控制模块在一个OTDR检测信号的检测周期中，若在预设时间段内所检测到返回的瑞利背向散射光和/或菲涅尔反射光的光强度小于预设阈值时，控制所述拉曼激光器向待检测光纤中再次发送拉曼脉冲激光。
  8. 根据权利要求7所述的高动态范围光时域反射的检测方法，其特征在于，一个OTDR检测信号的检测周期根据待检测的光纤中节点数量、检测信号的频宽和控制模块处理速度中的一项或者多项决定，所述一个OTDR检测信号的检测周期具体为Nms时，所述预设时间段为从当前轮检测周期中，发射OTDR检测信号后Mms时间内；其中，Mms从区间[0，N/2]中取值。
  9. 根据权利要求7所述的高动态范围光时域反射的检测方法，其特征在于，在所述OTDR检测信号的检测周期为4ms±1s时，所述预设时间段具体为发送OTDR检测信号后1±0.2ms以内。
  10. 根据权利要求7所述的高动态范围光时域反射的检测方法，其特征在 于，所述预设阈值具体为：
    根据在一个OTDR检测信号的检测周期内，获取的瑞利背向散射光和/或菲涅尔反射光的光功率由最初接收到时的最高值下降3-5dB的计算条件，计算得到。
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