Clarification of strain-temperature cross-sensitivity effect on Brillouin frequency shift in plastic optical fibers

Abstract

The strain-temperature cross-sensitivity effect on Brillouin frequency shift (BFS) in plastic optical fibers (POFs) is fully investigated. First, we show that the strain coefficient of the BFS is dependent on temperature. In the strain ranges of 0–1.2% and 4.0–9.0%, the temperature dependence is linear with coefficients of 1.5 MHz/%/°C and −0.4 MHz/%/°C, respectively. We then find that the temperature coefficient of the BFS is linearly dependent on strain with a coefficient of 1.5 MHz/°C/% in the strain range from 0 to 1.2%. For 4.0–9.0% strains, the BFS basically decreases with increasing temperature. These results indicate that temperature (and strain) compensation for the strain (and temperature) sensitivity of the BFS is required to correctly detect the strain and temperature magnitude in POF-based Brillouin sensing. We also show that temperature sensing with no sensitivity to strain is potentially feasible by using POFs pre-strained for >13%.