Simultaneous measurement of external refractive index and temperature based on long-period-grating-inscribed Sagnac interferometer and fiber Bragg grating

Peng Gao; Xiuyan Chen; Wenjiang Feng

doi:10.1063/1.4758126

Simultaneous measurement of external refractive index and temperature based on long-period-grating-inscribed Sagnac interferometer and fiber Bragg grating

Rev Sci Instrum. 2012 Oct;83(10):105001. doi: 10.1063/1.4758126.

Authors

Peng Gao¹, Xiuyan Chen, Wenjiang Feng

Affiliation

¹ College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, People's Republic of China. gaopengsysd@126.com

PMID: 23126794
DOI: 10.1063/1.4758126

Abstract

A compact Sagnac interferometer with a long-period grating (LPG) inscribed in a polarization-maintaining fiber (PMF-LPG) and a fiber Bragg grating (FBG) is proposed. The PMF-LPG is intrinsically sensitive to the external refractive index (ERI) and temperature, whereas the FBG is only sensitive to temperature. Simultaneous measurement of the ERI and temperature can be achieved by detecting wavelength shifts in the interference patterns of the Sagnac interferometer and the FBG. Because a Sagnac interference structure is used, a high ERI sensitivity of -21.07 nm∕refractive index unit in measurement range 1.33-1.43 is obtained, which is about three times higher than for the normal LPG ERI sensor.