阅读说明：本技术 一种基于Simplex脉冲编码的高信噪比光时域反射仪 (High signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding ) 是由 胡远朋 茅昕 于竞雄 王治 于 2019-11-01 设计创作，主要内容包括：本发明提供一种基于Simplex脉冲编码的高信噪比光时域反射仪,其特征在于：设置窄带宽光纤激光器(1)、光脉冲调制器(2)、光纤波分复用器(3)、环形器(4)、脉冲光编码器(5)、控制模块(6)、信号采集处理器(7)、信号放大器(8)、光电转换器(9)和通信单元(10),所述脉冲光编码器(5)在光源编码中采用基于Simplex脉冲编码的编码方式,在提高发射光子数的同时通过压窄激光脉冲宽度提高空间分辨率；窄带宽光纤激光器(1)连续运行产生的强激光增加进入被测光纤的光子数,实现提高信噪比,增加光时域反射仪的动态响应,增加测量精度与长度。本发明能够实现长距离的光纤测试,具有对断点、熔接、连接器、弯曲等进行定位的功能,同时具有高空间分辨率、测量精度高,测量距离长,信噪比高。(The invention provides a high signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding, which is characterized in that: the method comprises the steps that a narrow-bandwidth optical fiber laser (1), an optical pulse modulator (2), an optical fiber wavelength division multiplexer (3), a circulator (4), a pulse optical encoder (5), a control module (6), a signal acquisition processor (7), a signal amplifier (8), a photoelectric converter (9) and a communication unit (10) are arranged, the pulse optical encoder (5) adopts a coding mode based on Simplex pulse coding in light source coding, the number of emitted photons is increased, and meanwhile the spatial resolution is improved through the pulse width of narrow-bandwidth laser; the strong laser generated by the continuous operation of the narrow-bandwidth optical fiber laser (1) increases the number of photons entering the measured optical fiber, thereby realizing the improvement of the signal-to-noise ratio, increasing the dynamic response of the optical time domain reflectometer and increasing the measurement precision and the length. The invention can realize long-distance optical fiber test, has the functions of positioning breakpoints, fusion splices, connectors, bends and the like, and simultaneously has the advantages of high spatial resolution, high measurement precision, long measurement distance and high signal-to-noise ratio.)

1. The utility model provides a high SNR optical time domain reflectometer based on Simplex pulse code which characterized in that: a narrow-bandwidth optical fiber laser (1), an optical pulse modulator (2), an optical fiber wavelength division multiplexer (3), a circulator (4), a pulse optical encoder (5), a control module (6), a signal acquisition processor (7), a signal amplifier (8), a photoelectric converter (9) and a communication unit (10) are arranged,

the narrow-bandwidth optical fiber laser (1) is connected with an optical pulse modulator (2), the optical pulse modulator (2) is respectively connected with an optical fiber wavelength division multiplexer (3) and a pulse optical encoder (5), the optical fiber wavelength division multiplexer (3) is connected with a circulator (4), the circulator (4) is connected with a photoelectric converter (9), the photoelectric converter (9) is connected with a signal amplifier (8), the signal amplifier (8) is connected with a signal acquisition processor (7), and the signal acquisition processor (7) is connected with a control module (6); the control module (6) is respectively connected with the narrow-bandwidth optical fiber laser (1), the pulse light encoder (5) and the communication unit (10);

the pulse light encoder (5) adopts a Simplex pulse encoding-based encoding mode in light source encoding, improves the number of emitted photons and simultaneously improves the spatial resolution by pressing narrow laser pulse width; the strong laser generated by the continuous operation of the narrow-bandwidth optical fiber laser (1) increases the number of photons entering the measured optical fiber, thereby realizing the improvement of the signal-to-noise ratio, increasing the dynamic response of the optical time domain reflectometer and increasing the measurement precision and the length.

2. An optical time domain reflectometer with high signal to noise ratio based on Simplex pulse encoding as claimed in claim 1, wherein: the order of the Simplex pulse code is 256.

3. An optical time domain reflectometer with high signal to noise ratio based on Simplex pulse encoding as claimed in claim 2, wherein: the rising time and the falling time of the pulse light after being modulated by the pulse light encoder (5) are less than 0.1ns, and the quality of the pulse entering the tested optical fiber is high.

4. An optical time domain reflectometer with high signal to noise ratio based on Simplex pulse encoding as claimed in claim 1 or 2 or 3, wherein: the narrow bandwidth fiber laser (1) is a continuously operating fiber laser with a center wavelength of 1550 + -0.2 nm.

5. An optical time domain reflectometer with high signal to noise ratio based on Simplex pulse encoding as claimed in claim 1 or 2 or 3, wherein: the optical fiber wavelength division multiplexer (3) is used for simultaneously carrying out a plurality of wavelength tests on the optical fiber.

6. An optical time domain reflectometer with high signal to noise ratio based on Simplex pulse encoding as claimed in claim 1 or 2 or 3, wherein: the signal acquisition processor (7) is used for realizing data acquisition, analog-to-digital conversion and signal processing, and the signal processing adopts an arithmetic mean filtering method.

7. An optical time domain reflectometer with high signal to noise ratio based on Simplex pulse encoding as claimed in claim 1 or 2 or 3, wherein: the photoelectric converter (9) has a dark current of less than 1 nA.

8. An optical time domain reflectometer with high signal to noise ratio based on Simplex pulse encoding as claimed in claim 1 or 2 or 3, wherein: the signal amplifier (8) changes the amplification factor of the signal adaptively according to the amplitude of the signal output by the photoelectric converter (9).

Technical Field

The invention relates to the technical field of high signal-to-noise ratio optical time domain reflectometers, in particular to a high signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding.

Background

The conventional OTDR (optical time domain reflectometer) system generally adopts a direct detection mode, and the dynamic response performance of the OTDR is limited because the maximum optical power allowed by the detection light and the fiber laser is always limited due to the existence of the fiber nonlinear effect. The effective sensing length of a conventional OTDR using the direct detection method is generally less than 35 km. This greatly limits the application of OTDR.

Disclosure of Invention

The invention aims at solving the problems of high spatial resolution, high measurement precision, long measurement distance and high signal-to-noise ratio. The invention relates to a high signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding, which can realize long-distance measurement on optical fibers, and can position breakpoints, fusion splices, connectors, bends and the like when the optical fibers have breakpoints, fusion splices, connectors, bends and the like. The high signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding has high signal-to-noise ratio, spatial resolution and measurement accuracy.

The technical scheme provided by the invention is that the optical time domain reflectometer with high signal-to-noise ratio based on Simplex pulse coding is provided with a narrow-bandwidth optical fiber laser 1, an optical pulse modulator 2, an optical fiber wavelength division multiplexer 3, a circulator 4, a pulse optical encoder 5, a control module 6, a signal acquisition processor 7, a signal amplifier 8, a photoelectric converter 9 and a communication unit 10,

the narrow-bandwidth optical fiber laser 1 is connected with an optical pulse modulator 2, the optical pulse modulator 2 is respectively connected with an optical fiber wavelength division multiplexer 3 and a pulse optical encoder 5, the optical fiber wavelength division multiplexer 3 is connected with a circulator 4, the circulator 4 is connected with a photoelectric converter 9, the photoelectric converter 9 is connected with a signal amplifier 8, the signal amplifier 8 is connected with a signal acquisition processor 7, and the signal acquisition processor 7 is connected with a control module 6; the control module 6 is respectively connected with the narrow-bandwidth optical fiber laser 1, the pulse optical encoder 5 and the communication unit 10;

the pulse light encoder 5 adopts a coding mode based on Simplex pulse coding in light source coding, improves the number of emitted photons and simultaneously improves the spatial resolution by pressing narrow laser pulse width; the strong laser generated by the continuous operation of the narrow-bandwidth optical fiber laser 1 increases the number of photons entering the measured optical fiber, thereby realizing the improvement of the signal-to-noise ratio, increasing the dynamic response of the optical time domain reflectometer and increasing the measurement precision and the length.

Also, the order of the Simplex pulse code is 256.

Moreover, the rise time and the fall time of the pulse light after being modulated by the pulse light encoder 5 are less than 0.1ns, and the quality of the pulse entering the optical fiber to be measured is high.

Also, the narrow bandwidth fiber laser 1 is a continuously operating fiber laser having a center wavelength of 1550 ± 0.2 nm.

Furthermore, the optical fiber wavelength division multiplexer 3 is used to perform a plurality of wavelength tests on the optical fiber at the same time.

Furthermore, the signal acquisition processor 7 is used to implement data acquisition, analog-to-digital conversion and signal processing, which employs an arithmetic mean filtering method.

Further, the photoelectric converter 9 has a dark current of less than 1 nA.

Furthermore, the signal amplifier 8 adaptively changes the amplification factor of the signal according to the amplitude of the output signal of the photoelectric converter 9.

The Simplex pulse coding adopted by the invention can improve the signal-to-noise ratio of an OTDR system, improve the measurement precision of temperature and strain and increase the measurement distance; the coding pulse light coded by the Simplex pulse improves the signal-to-noise ratio of a system and simultaneously improves the spatial resolution of the system by reducing the code element width of the coding pulse, the code element width can be as small as 10ns of the service life of an optical fiber phonon, and the corresponding spatial resolution can reach 0.8 m; the system has the monitoring functions of breakpoint, welding, connector, bending and the like by adopting coherent detection, can effectively overcome the defect that the traditional OTDR needs double-end access to cause the breakpoint to fail to work, and enhances the adaptability and the practicability of the sensing system. The invention can realize long-distance optical fiber test, when the optical fiber has a breakpoint, the system has the function of positioning the breakpoint, fusion, connector, bending and the like, and simultaneously has high spatial resolution, high measurement precision, long measurement distance and high signal-to-noise ratio.

Drawings

Fig. 1 is a block diagram of a high snr optical time domain reflectometer based on Simplex pulse coding according to an embodiment of the present invention.

Wherein the reference numerals are: the device comprises a 1-narrow bandwidth optical fiber laser, a 2-optical pulse modulator, a 3-optical fiber wavelength division multiplexer, a 4-circulator, a 5-pulse optical encoder, a 6-control module, a 7-signal acquisition processor, an 8-signal amplifier, a 9-photoelectric converter and a 10-communication unit.

Detailed Description

The technical scheme of the invention is explained in detail in the following by combining the drawings and the embodiment.

The invention provides a high signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding, wherein the Simplex pulse coding is a unipolar array matrix consisting of 0 and 1, and the matrix is obtained by converting a hadamard matrix (Hadamard product matrix). The order number of the hadamard matrix must be an integer multiple of 1, 2 or 4, and assuming that K is an n-order hadamard matrix, the resulting matrix is a 2 n-order hadamard matrix, such as the following matrix:

when the first row and the first column of the hadamard matrix are removed, the element "1" in the matrix is changed to "0" and the element "-1" is changed to "1", and the new matrix obtained is a Simplex pulse-code matrix. While the matrix is a unipolar matrix. Compared with the existing gray code coding and CCPONS coding, the Simplex pulse coding adopted in the light source coding has the advantage that when the coding order is lower, the coding gain of the Simplex coding is obviously higher than that of the gray code coding and CCPONS coding.

The invention provides a high signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding, which adopts Simplex pulse coding laser pulse, improves the number of emitted photons and can improve the spatial resolution by narrowing the laser pulse width; the continuous operation high-power optical fiber laser is used as a light source of the optical time domain analyzer, a coherent pump narrow-band laser is replaced, the difficulty that the frequency of a detection laser is required to be strictly locked in the optical time domain analyzer is overcome, stimulated scattered light amplification is achieved in a single-mode optical fiber instead of narrow-band amplification through strong laser generated by the continuous operation high-power optical fiber laser, the gain of stimulated scattered light subjected to backward coherent amplification is increased, the total gain of modulated light based on Simplex pulse coding reaches 50dB, the signal-to-noise ratio of a system is improved, the measurement length is increased, and the measurement precision is improved.

The invention relates to a high signal-to-noise ratio optical time domain reflectometer based on Simplex pulse coding, which comprises a narrow-bandwidth optical fiber laser, an optical pulse modulator, an optical fiber wavelength division multiplexer, a circulator, a pulse optical encoder, a control module, a signal acquisition processor, a signal amplifier, a photoelectric converter and a communication unit.

Referring to fig. 1, in the optical time domain reflectometer with high signal-to-noise ratio based on Simplex pulse coding provided in the embodiment, a narrow bandwidth optical fiber laser 1 is connected to an optical pulse modulator 2, the optical pulse modulator 2 is respectively connected to an optical fiber wavelength division multiplexer 3 and a pulse optical encoder 5, the optical fiber wavelength division multiplexer 3 is connected to a circulator 4, the circulator 4 is connected to a photoelectric converter 9, the photoelectric converter 9 is connected to a signal amplifier 8, the signal amplifier 8 is connected to a signal acquisition processor 7, and the signal acquisition processor 7 is connected to a control module 6; the control module 6 is respectively connected with the narrow bandwidth optical fiber laser 1, the pulse optical encoder 5 and the communication unit 10. The communication unit 10 can be connected to a host computer. Specifically, the output end of the narrow bandwidth fiber laser 1 is connected to a first input end of the optical pulse modulator 2, and the input end is connected to a first output end of the control module 6. The output of optical pulse modulator 2 links to each other with optical fiber wavelength division multiplexer 3's input, the second input links to each other with pulse optical encoder 5's output, optical fiber wavelength division multiplexer 3's input links to each other with optical pulse modulator 2's output, the output links to each other with circulator 4's first input, control module 6's first output links to each other with narrow bandwidth fiber laser 1's input, the second output links to each other with pulse optical encoder 5's input, the third output links to each other with communication unit 10's input. The output end of the signal acquisition processor 7 is connected with the input end of the control module 6, and the input end is connected with the output end of the signal amplifier 8. In specific implementation, the signal acquisition processor 7 and the control module 6 can be connected in two directions, so that the control module 6 can control whether the narrow-bandwidth fiber laser 1 and the signal acquisition processor 7 work or not and can control the encoding mode of the pulse light encoder 5. The output end of the signal amplifier 8 is connected with the input end of the signal acquisition processor 7, and the input end is connected with the output end of the photoelectric converter 9. The input of the photoelectric converter 9 is connected to the output of the circulator 4 and to the input of the signal amplifier 8.

Compared with the prior art, the key different structures of the invention are that a pulsed light encoder based on Simplex pulse coding, a narrow-bandwidth optical fiber laser (1550 +/-0.2 nm) and a signal amplifier adopting variable gain are adopted. Compared with the existing structure of the optical time domain reflectometer, the structure of the invention improves the signal-to-noise ratio, increases the dynamic response of the optical time domain reflectometer, and increases the measurement precision and length.

In the embodiment of the present invention, the narrow bandwidth fiber laser 1 preferably adopts a 120mW continuous operation fiber laser with a center wavelength of 1550 ± 0.2nm and a spectral bandwidth of 200 kHz.

Preferably, the order of the Simplex pulse code is 256. The pulse light encoder 5 has a high-speed and high-precision encoding method under the control of the control module 6. The rising time and the falling time of the pulse light modulated by the pulse modulator 5 are short, less than 0.1ns, and the quality of the pulse entering the tested optical fiber is high.

In the invention, the control module 6 controls a pulse signal source (namely, the narrow-bandwidth optical fiber laser 1) to generate signals, codes electric pulses through Simplex pulse coding, and synchronously controls the signal acquisition and processing unit 7.

The optical fiber wavelength division multiplexer 3 can simultaneously carry out a plurality of wavelength tests on the optical fiber, and the test efficiency is improved.

The signal acquisition processor 7 implements data acquisition, analog-to-digital conversion and signal processing, wherein the signal acquisition frequency is 200 MHz. The signal processing adopts arithmetic mean filtering method, after the light enters the tested optical fiber, the reflected light of the same position is continuously 10 values, and then the average value is taken. The method can filter general random interference signals and smooth the signals.

Preferably, the dark current of the photoelectric converter 9 is small, less than 1 nA. Meanwhile, the amplification factor of the signal amplifier is self-adaptive amplification. The signal amplifier 8 in the embodiment of the present invention can adaptively change the amplification factor of the signal according to the amplitude of the signal output by the photoelectric converter 9. The amplitude of the output signal of the photoelectric converter 9 is made to be within a suitable range so that the signal acquisition processor 7 can process the signal. The signal amplifier 8 in the present invention is mainly a hardware circuit implemented by a plurality of comparators.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.