Simultaneous Measurement of Strain and Temperature Based on Radio-Frequency Demodulation

We propose and experimentally demonstrate a hybrid multimode fiber laser configuration for simultaneous measurement of strain and temperature based on radio-frequency demodulation. The hybrid lasers include a Brillouin erbium fiber laser (BEFL) with dual Brillouin peaks and an erbium-doped fiber laser (EDFL). The BEFL and EDFL are incorporated in a simple and compact ring laser cavity. The injection of Brillouin pump (BP) excites first-order stimulated Brillouin scattering in two sections of fibers with different Brillouin Stokes frequencies. Without BP, the laser performs as an EDFL. The simultaneous measurement of strain and temperature are achieved by monitoring the self-beating signals of the BEFL and EDFL, respectively. The longitudinal modes beat frequency originated from the EDFL and difference of Brillouin frequency shifts from the BEFL are in radio-frequency domain and detected with an electrical spectrum analyzer which makes the detection simplified. The proposed sensor is found to be characterized with simplicity and compact configuration. The maximum measurement errors of strain and temperature obtained are within ±20.3 με and ±0.5 °C.