Distributed Vibration Sensing Over 125 km With Enhanced SNR Using Phi-OTDR Over a URFL Cavity

• Autor(a) principal: Martins,HF
• Data de Publicação: 2015
• Outros Autores: Martin Lopez,S, Corredera,P, Diego Ania Castanon,JD, Orlando Frazão, Gonzalez Herraez,M
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://repositorio.inesctec.pt/handle/123456789/7252; http://dx.doi.org/10.1109/jlt.2015.2396359

We describe the use of a phase-sensitive optical time domain reflectometer (phi OTDR) over an ultra-long Raman fiber laser cavity allowing fully distributed detection of vibrations over 125 km. Compared to a first-order Raman-assisted phi OTDR, this scheme shows an enhanced signal-to-noise ratio (SNR). This is due to the fact that the relative intensity noise introduced by the Raman amplification is mostly transferred to a lower frequency range, where the balanced detection implemented in the setup provides better suppression of the common-mode noise. The sensor was able to measure vibrations of up to 380 Hz (limit set by the time of flight of light pulses) in a distance of 125 km with a resolution of 10 m and an average SNR of 8 dB with no postprocessing. This implies a > 3 dB improvement in SNR over a first-order Raman-assisted setup with similar characteristics.