研究目的
To propose and experimentally demonstrate a distributed optical fibre sensor (DOFS) based on the hybrid of phase-sensitive optical time domain reflectometry (Ф-OTDR) and Raman optical time domain reflectometry (ROTDR) for simultaneous reconstruction of acoustic and temperature fields along the sensing fibre.
研究成果
The proposed hybrid system is capable of reconstructing acoustic and temperature fields simultaneously along a 12km long standard single-mode fibre with high accuracy. It offers a new option for multi-parameter sensing, extending the potential application fields of DOFS technologies.
研究不足
The study does not explicitly mention limitations, but potential areas for optimization could include further reducing the temperature uncertainty and extending the vibration frequency response range.
The experimental setup involved a hybrid system sharing the same laser and sensing fibre. A laser delivering CW output at 1550nm was used as the light source. The output lightwave was divided into two parts by a 90:10 optical coupler. The main part was pulse modulated by an Acousto-optic modulator (AOM) with frequency shift of 150MHz. The probe pulse was shaped with 100ns pulse width and 6kHz repetition rate and amplified to 22dBm by EDFA. The probe pulse was launched into fibre under test (FUT) through an optical circulator (OC). The back scattered signal was separated into the RBS, RS, and RAS components by a wavelength division multiplexer (WDM) filter. The Rayleigh component and the reference light were combined together by the 50:50 coupler and then received by a balanced detector for acoustic field reconstruction. Raman Stokes and Anti-stokes lights are detected by two APDs. The outputs of the BPD and two APDs were synchronously recorded by a data acquisition (DAQ) card with 1GHz sampling rate.
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