Heng Xie, Junqiang Sun,* and Danqi Feng
Optical fiber sensors for simultaneous strain and temperature measurement have attracted great interest in application of structure health condition and damage identification due to their high sensitivity, compact size, low cost. Although A wide variety of optical-fiber based sensing technology have been proposed to meet such requirements, the complicated fabrication process of these fiber sensors with special structure restricts their practical application.
In this paper, we propose a new technology to discriminate strain and temperature based on based on erbium-doped fiber laser (EDFL) and Brillouin erbium fiber laser (BEFL) incorporated in a single ring laser cavity. The EDFL can be switched to BEFL by injecting the Brillouin pump into the laser cavity. Longitudinal modes beat frequency and Brillouin frequency shift are monitored to discriminate strain and temperature. The longitudinal modes beat frequency is measured by observing the self-beating signals of the EDFL, while the Brillouin frequency shift is measured by monitoring the heterodyning signal of the BEFL. The simultaneous measurement errors of strain and temperature are within ± 25.8με and ± 0.8°C. Compared to the previous optical fiber sensors, the proposed sensor is of simple structure and compact size and is immune to fiber bending.
The paper is published on Optical Express (Vol. 24, Issue 11, 2016. doi:10.1364/OE.24.011475). This work is supported by the National Natural Science Foundation of China under Grant No. 61377074 and Research Fund for the Doctoral Program of High Education of China under Grant 20120142130004.
Figure.1 Experiment set-up of simultaneous strain and temperature sensing
Figure. 2 BFS and LMBF response to tempearture
Figure. 3 LMBF response to strain