Brillouin frequency shift hopping in polymer optical fiber

Abstract

We investigated the Brillouin gain spectrum dependence on large strain of up to 60% in a polymer optical fiber (POF) at 1.55 μm, and found that the Brillouin frequency shift (BFS) abruptly changes from ∼2.7 GHz to ∼3.2 GHz. We named this phenomenon “BFS hopping,” and found it to originate from the varied acoustic velocity induced by the stepwise change in the core diameter of the POF. This is because of the yielding of the overcladding layer composed of polycarbonate. After the occurrence of BFS hopping phenomenon, the BFS dependence coefficients on strain and temperature in the POF were measured to be −65.6 MHz/% and −4.04 MHz/K respectively. These values indicate that, compared to an unstrained POF, further higher-precision temperature sensing with lower strain sensitivity is feasible.