A Compensation Method for Laser Nonlinear Tuning Effect in Optical Frequency Domain Reflectometry

An optical frequency domain reflectometer and nonlinear tuning technology, which is applied in the direction of transmitting sensing components, instruments, and converting sensor output with optical devices, to achieve the effects of increasing the maximum measurable length, increasing the measuring distance, and improving the spatial resolution

Active Publication Date: 2022-02-08
NANJING UNIV
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Problems solved by technology

This method is simple and data processing is convenient, but limited by the Nyquist sampling theorem, the longest measurement length is only 1 / 4 of the delay fiber of the auxiliary interferometer

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  • A Compensation Method for Laser Nonlinear Tuning Effect in Optical Frequency Domain Reflectometry
  • A Compensation Method for Laser Nonlinear Tuning Effect in Optical Frequency Domain Reflectometry
  • A Compensation Method for Laser Nonlinear Tuning Effect in Optical Frequency Domain Reflectometry

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Embodiment Construction

[0029] The specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing:

[0030] In OFDR, the light source used is a tunable laser. The frequency-sweeping light emitted by the laser passes through the reference path and the measurement path, and beat frequency occurs. When the laser sweeps linearly, there is a one-to-one correspondence between the beat frequency and the position of the optical fiber to be tested. relationship: f b =2γnz / c. The collected signal is converted from the time domain to the frequency domain by Fourier transform, and the position information of the reflection point can be obtained according to this relationship. However, lasers generally have a nonlinear frequency sweep. At this time, the sweep rate is a function of time, and the relationship between the beat frequency and the position of the fiber to be tested becomes: f b =2γ(t)nz / c, one position corresponds to multiple beat frequencies, resul...

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Abstract

The invention discloses a laser nonlinear tuning effect compensation system for an optical frequency domain reflectometer (OFDR). Firstly, an acousto-optic frequency shifter (AOM) is connected to an interference arm of the OFDR auxiliary interferometer to shift the frequency of the light wave to increase the beat signal frequency of the auxiliary interferometer. Then, the beat frequency signal is converted into an AC signal by a photodetector, and the zero-crossing point of the signal is used as a reference point to correct the measurement signal of the main interferometer. The correction process includes five steps: solving the zero-crossing point, calculating the frequency interval between two zero-crossing points, eliminating the additional frequency introduced by AOM, finding the correction coefficient, and correcting the abscissa. Using the correction signal obtained in the above process for OFDR detection can effectively overcome the influence of the nonlinear tuning effect of the light source and improve the spatial resolution of OFDR.

Description

technical field [0001] The invention belongs to the field of distributed optical fiber sensing, and in particular relates to a method for compensating nonlinear tuning effects of lasers used in optical frequency domain reflectometers. Background technique [0002] Optical Frequency Domain Reflectometer (OFDR) technology was first proposed by Eickhoff et al. in 1981. In the past few years, OFDR has played an important role in the field of distributed optical fiber sensing due to its advantages of high spatial resolution and high sensitivity. Its main applications include temperature sensing, strain sensing, and shape sensing. [0003] In the basic OFDR, the frequency-sweeping light emitted by the tunable laser is divided into two paths, one path is used as the reference light, and the other path enters the optical fiber to be tested. The reflected or scattered light and the reference light have a beat frequency. To detect the characteristics of the optical fiber under test. ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01D5/353G01D18/00
CPCG01D5/35393G01D5/35306G01D18/00
Inventor 王峰邢婧婧章颖张旭苹张益昕
Owner NANJING UNIV
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