Joint-peaks demodulation method based on multireflection peaks of a few-mode fiber Bragg grating for reducing sensing error

A few-mode fiber Bragg grating (FM-FBG) inscribed in a few-mode fiber (FMF) can maintain multiple reflection peaks due to the stable multiple modes in FMF. This paper studies the sensing characteristics of multiple reflection peaks for a four-mode FBG (4M-FBG) and innovatively proposes a joint-peak demodulation method based on one FM-FBG to reduce measurement error in temperature or strain sensing. This joint-peak demodulation method, theoretically explained and experimentally verified, provides the possibility of generating miniature sensors with high measurement accuracy and stable measurement performance. The potential of 4M-FBG for simultaneous measurement of strain and temperature is studied in this paper. By measuring the changes of wavelength and intensity of the reflection peaks, temperature and strain can be measured effectively.