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Method for correcting nonlinear sweep frequency of tunable laser in optical frequency domain reflectometer

An optical frequency domain reflectometer and a technology for tuning lasers, which are used in instruments, converting sensor outputs, and using optical devices to transmit sensing components. It can solve the problem of high sampling rate and data volume requirements, measurement distance, and compensation effect limitations. problem, to achieve the effect of real-time correction

Active Publication Date: 2019-04-26
NANJING UNIV
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Problems solved by technology

J.Song et al. use the zero-crossing resampling method to compensate, but this method has high requirements for sampling rate and data volume (J.Song, et al, IEEE Photonics Journal, 2014, 6.3:1-8)
In addition, there are methods such as deskewing filters, which are also limited in terms of measurement distance and compensation effect.

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  • Method for correcting nonlinear sweep frequency of tunable laser in optical frequency domain reflectometer
  • Method for correcting nonlinear sweep frequency of tunable laser in optical frequency domain reflectometer
  • Method for correcting nonlinear sweep frequency of tunable laser in optical frequency domain reflectometer

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Embodiment Construction

[0032] Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

[0033] OFDR systems use swept frequency lasers. Assuming that the laser sweeps linearly, its sweeping speed is γ, and the initial frequency is f 0 , then its frequency is expressed as:

[0034] f(t)=f 0 +γt

[0035] In the OFDR system, the reflected or backscattered light generated at a certain position of the optical fiber interferes with the reference light to obtain a single-frequency beat signal. The frequency of the beat signal is the frequency difference between the reflected light and the reference light. The reflected light and the reference light are lights emitted by the laser at different times, and the time interval corresponding to the beam emission is equal to the group delay difference between the reflected light and the reference light. When the laser sweeps linearly, since the optical distance from the reflection position to th...

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Abstract

The invention discloses a method for correcting the nonlinear sweep frequency of a tunable laser in an optical frequency domain reflectometer. The method comprises the steps that firstly, a zero crossing point of an auxiliary interferometer is detected, then a correction coefficient is obtained through calculation according to a zero crossing point serial number difference, then the correction coefficient is used for correcting a main interferometer signal, the corrected signal is re-sampled through an interpolation method, and finally, the signal is converted to a frequency domain by using time-frequency transform, thereby compensating for the nonlinear sweep frequency of the laser. The method for correcting the nonlinear sweep frequency of the tunable laser in the optical frequency domain reflectometer has the advantages that a plurality of reflection points which are closer on sensing optical fiber can be distinguished, and the length of delay optical fiber of the auxiliary interferometer is not limited; in addition, the volume of processed data is smaller, the requirements for the sampling rate of a collecting card are reduced, and the method can reach longer measurement distance.

Description

technical field [0001] The invention relates to the field of optical fiber sensing, in particular to the nonlinear frequency sweeping of a laser in an optical frequency domain reflectometer and its correction method. Background technique [0002] Optical frequency domain reflectometer (OFDR) was first proposed by W.Eickhoff et al. in 1981, and its basic principle comes from FMCW (frequency modulated continuous wave) technology. A common OFDR system uses a tunable laser to linearly tune the optical frequency. The light emitted by the laser is divided into two beams after passing through the coupler. One beam of light enters the reference fiber and is reflected back to the coupler by the mirror as the reference light; after the other beam enters the fiber to be tested, Rayleigh scattering and Fresnel reflection returns a portion of the light back into the coupler as test light. At this time, the reference light interferes with the test light composed of Rayleigh scattering a...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01D5/353G01D18/00
CPCG01D5/35306G01D5/35361G01D18/00
Inventor 王峰章颖邢婧婧张旭苹张益昕
Owner NANJING UNIV
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