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A method and device for measuring cotdr based on psk pulse coding

A technology of pulse coding and measurement method, applied in the field of measurement, can solve the problems of reducing and reducing system measurement accuracy and signal-to-noise ratio, random fluctuation of signal power, etc., to achieve the effect of improving signal-to-noise ratio, reducing measurement error, and suppressing CRN

Active Publication Date: 2022-02-01
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

However, the high coherence of the narrow-linewidth light source will cause the scattering points in the scattering unit to interfere with each other to generate coherent Rayleigh noise (CRN), which will cause random fluctuations in the power of the detected signal and reduce the measurement accuracy and signal-to-noise ratio of the system.
And due to the phase correlation characteristics of CRN, it cannot be reduced simply by signal averaging or adding a bandpass filter.

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  • A method and device for measuring cotdr based on psk pulse coding
  • A method and device for measuring cotdr based on psk pulse coding
  • A method and device for measuring cotdr based on psk pulse coding

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[0032] The technical solutions of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0033] The present invention utilizes PSK pulse coding to suppress the coherent Rayleigh noise in the COTDR system. The interference phase difference of scattering points between different bits in the pulse produces a π phase shift, and the superposition and averaging of the obtained PSK pulse coded detection curve and the uncoded original detection curve can effectively reduce the coherent scattering points between bits, thereby suppressing the coherent The impact of noise on system performance.

[0034] The symbols used in the text are explained as follows:

[0035] m is the length of the code, t b is the bit duration, W is the pulse width, v π is the half-wave voltage of PM, E 0 Intensity of signal light for PSK pulse encoding, v 0 is the frequency of the PSK pulse-encoded signal light, is the in...

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Abstract

The invention discloses a COTDR measurement method based on PSK pulse coding and its device, which uses a phase modulator driven by an arbitrary function generator and an electro-optic modulator to perform PSK pulse coding on the continuous light output by a narrow linewidth laser, and the PSK pulse The back Rayleigh scattered light generated by the coded signal light propagating in the optical fiber is used as the signal light for heterodyne coherent detection with the local reference light. After the output heterodyne signal is demodulated by the digital signal processing unit, it is sent to the computer for processing. The computer performs timing alignment on the obtained PSK pulse coded detection curve and the uncoded original detection curve, superimposes and averages, and performs linear fitting on the superposed and averaged curve to obtain information such as optical fiber transmission attenuation and fault location. This method can not only effectively suppress the CRN and reduce the amplitude fluctuation of the signal, but also reduce the measurement error and improve the signal-to-noise ratio of the system.

Description

technical field [0001] The invention relates to the field of measurement technology, in particular to a PSK pulse code-based COTDR measurement method and a device thereof. Background technique [0002] Optical time domain reflectance (Optical Time Domain Analysis, OTDR) sensing technology is one of the main means of monitoring the health of optical fiber communication lines. Attenuation, breakage, and spatial localization on links play an important role in fault detection and localization of bridges, power lines, and optical communication lines. [0003] OTDR has a small measurement range due to the direct detection method. In long-distance communication links, fiber amplifiers such as erbium-doped fiber amplifiers (EDFA) are usually used to compensate for the transmission loss of pulsed signal light. However, while the EDFA amplifies the power of the signal light, it will also generate strong amplified spontaneous emission (ASE) noise. The accumulation of ASE noise will sh...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B10/071H04B10/50H04B10/516H04B10/524H04B10/556
CPCH04B10/071H04B10/5053H04B10/5161H04B10/524H04B10/5561
Inventor 李永倩王磊范海军张立欣
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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