Fudan University

Qian Xiao

Bo Jia

Yuan Wu

Pang Bian

A method for diminishing the signal interference of a transmission path of an optical fiber interference system, belonging to the technical field of optical fiber sensing. A wavelength division multiplexer () is connected in series to the end of an induced optical fiber, a wavelength component (&#x3bb;) is separated from an operating path by means of the wavelength division multiplexer () so as to measure a signal picked up by a transmission path, and the signal is removed from overall interference sensing signals by taking same as a reference, thereby obtaining a target measurement signal. Also provided is a structure for diminishing the signal interference of a transmission path of an optical fiber interference system. The method and the structure are simple; moreover, the device connected to the end of an induced optical fiber is passive, so that power supply is not required, and it is easy to implement. The present invention can be used for a sensing structure with a single measurement point and can be used in a sensing structure with a plurality of discontinuous measurement points as well.

Method and structure for diminishing signal interference of transmission path of optical fibre interference system

A method using wavelength division multiplexing for reducing light diffusion and light reflection interference in an interference path, comprising: connecting a wavelength division multiplexer () serially at an end of a sensing optical fiber (); using the wavelength division multiplexer () to extract a wavelength component from a working path for measuring an interfering signal caused by light diffusion and light reflection; using the signal as a reference to extract an effective signal component that has been interfered by light diffusion and light reflection, and obtaining a pure effective signal. Because the device connected at the end of the sensing optical fiber () is passive and requires no power, the system is easy to implement and is particularly suitable for situations in which power provision is difficult at the end of the sensing optical fiber (). The method is suitable for long distance pipeline monitoring and a wide-range optical of fiber perimeter security. Also provided is a system using wavelength division multiplexing for reducing light diffusion and light reflection interference in an interference path.

Method and system using wavelength division multiplexing for eliminating and reducing light diffusion and light reflection interference in interference path

A method for reducing interference from scattered light/reflected light of an interference path by generating carrier through phase. Phase modulation is applied on the terminal of a fiber path, and a target signal is separated from an interference signal by selecting a specific working point, to obtain a purer target signal, thereby lengthening the measurement distance. The signal demodulation manner used in this method is different from the traditional manner of modulation performed by generating a carrier through the phase, and does not need to use the modulation frequency as the reference signal during demodulation, so this manner is easily implemented. The method is applicable to long-distance pipeline monitoring and wide-range fiber perimeter security, and especially to an application environment in which the modulation end is far away from the signal demodulation end. The method can also be applied in an application in which measurement is implemented by modulating an optical transmission phase in a feedback device.

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Shanghai, China

Qian Xiao