Real time dynamic strain monitoring of optical links using the backreflection of live PSK data.
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Martins, H., Shi, K., Thomsen, B., Martin-Lopez, S., Gonzalez-Herraez, M., & Savory, S. (2016). Real time dynamic strain monitoring of optical links using the backreflection of live PSK data.. Optics express, 24 (19), 22303-22318. https://doi.org/10.1364/oe.24.022303
A major cause of faults in optical communication links is related to unintentional third party intrusions (normally related to civil/agricultural works) causing fiber breaks or cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic strain recorded along the cable. In this work, a novel technique is proposed to implement real-time distributed strain sensing in parallel with an operating optical communication channel. The technique relies on monitoring the Rayleigh backscattered light from optical communication data transmitted using standard modulation formats. The system is treated as a phase-sensitive OTDR (ΦOTDR) using random and non-periodical non-return-to-zero (NRZ) phase-shift keying (PSK) pulse coding. An I/Q detection unit allows for a full (amplitude, phase and polarization) characterization of the backscattered optical signal, thus achieving a fully linear system in terms of ΦOTDR trace coding/decoding. The technique can be used with different modulation formats, and operation using 4 Gbaud single-polarization dual PSK and 4 Gbaud dual-polarization quadrature PSK is demonstrated. As a proof of concept, distributed sensing of dynamic strain with a sampling of 125 kHz and a spatial resolution of 2.5 cm (set by the bit size) over 500 m is demonstrated for applied sinusoidal strain signals of 500 Hz. The limitations and possibilities for improvement of the technique are also discussed.
This work was supported by the European Research Council through Starting Grant UFINE (Grant no. 307441), the Spanish MINECO through project TEC2013-45265-R, PCIN-2015- 219, and the regional program SINFOTON-CM: S2013/MIT-2790. HFM acknowledges EU funding through the FP7 ITN ICONE program, gr. #608099. SML acknowledges funding from the Spanish MINECO through a “Ramon y Cajal” contract. UK EPSRC funding through project EP/J008842/1.
EC FP7 MC ITN (608099)
External DOI: https://doi.org/10.1364/oe.24.022303
This record's URL: https://www.repository.cam.ac.uk/handle/1810/286824
Attribution 4.0 International
Licence URL: https://creativecommons.org/licenses/by/4.0/