Abstract
A digital optical phase-locked loop (OPLL) has been implemented to develop a
distributed Brillouin sensing system in optical fibers. In our experiment, two commercial
semiconductor lasers are phase-locked to each other with a highly flexible offset frequency
using field programmable gate array (FPGA)-based electronics. Then, the difference frequency
between the two lasers is highly stabilized and scanned by a desired step frequency in the vicinity
of the Brillouin frequency of standard single-mode optical fibers. Consequently, the distribution
of Brillouin frequency shift over a 50 km-long sensing fiber has been successfully measured by a
very simple and low-cost Brillouin optical time-domain reflectometry (BOTDR) sensing system
without any penalty in the sensing performance. The measurement repeatability at 50 km position
of sensing fiber with a 5 m spatial resolution was measured be 4.5MHz under fast measurement
conditions: the number of trace averaging of 2000 and the frequency scan step of 12.8 MHz,
showing the figure-of-merit of 3.0.
Publication Reference
Optics Express, Vol. 30, Issue 11, pp. 18090-18097 (2022)
Year
2022-05-23
Sponsors
Centre Suisse d’Electronique et de Microtechnique S.A. CSEM
