Phase-sensitive Optical Time Domain Reflectometer Assisted by First-order Raman Amplification for Distributed Vibration Sensing Over >100 km

• Published in: Journal of lightwave technology 2014-04, Vol.32 (8), p.1510-1518
• Main Authors: Martins, Hugo F., Martin-Lopez, Sonia, Corredera, Pedro, Filograno, Massimo L., Frazao, Orlando, Gonzalez-Herraez, Miguel
• Format: Article
• Language: English
• Subjects: Applied sciences; Circuit properties; Distributed sensor; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Integrated optics. Optical fibers and wave guides; Noise; Optical and optoelectronic circuits; Optical fiber amplifiers; Optical fiber sensors; Optical pulses; Optoelectronic devices; phase-sensitive optical time domain reflectometry (OTDR); Physics; Raman scattering; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Stimulated emission; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); vibration sensor
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2014.2308354

In this study, the authors present an experimental and theoretical description of the use of first order Raman amplification to improve the performance of a Phase-sensitive optical time domain reflectometer (φOTDR) when used for vibration measurements over very long distances. A special emphasis is given to the noise which is carefully characterized and minimized along the setup. A semiconductor optical amplifier and an optical switch are used to greatly decrease the intra-band coherent noise of the setup and balanced detection is used to minimize the effects of RIN transferred from the Raman pumps. The sensor was able to detect vibrations of up to 250 Hz (close to the limits set by the time of flight of light pulses) with a resolution of 10 m in a range of 125 km. To achieve the above performance, no post-processing was required in the φOTDR signal. The evolution of the φOTDR signal along the fiber is also shown to have a good agreement with the theoretical model.