Integrated Reflective Lyot Filter and FBG Structure for Simultaneous Sensing of Temperature and Axial Strain in Fiber Ring Laser

An integrated all-fiber reflective Lyot (RL) filter and fiber Bragg gating (FBG) sensor for simultaneous sensing of temperature and axial strain is proposed and demonstrated experimentally based on a dual-wavelength fiber ring laser (FRL) in this article. Because of the gain competition between simultaneous dual-wavelength lasers, a narrow 3-dB bandwidth less than 0.03 nm and an optical signal-to-noise ratio (OSNR) higher than 50 dB are achieved. The laser emission peaks exhibit different wavelength shifts due to their different responses to temperature and axial strain variations; thus, simultaneous measurement of temperature and axial strain can be easily achieved by establishing and demodulating a sensing matrix. The sensing system exhibits the maximum sensitivities of −1.03 nm/°C and 7.33 pm/
$\mu \varepsilon $
for temperature and axial strain, respectively, with a low detection limit (DL) of
$- 1.38\times 10^{-{3}}~^{\circ }$
C and
$0.19~\mu \varepsilon $
as well as a high spectral quality factor (Q) of
$1.77\times 10^{{3}}$
and
$8.95\times 10^{{4}}$
. Through selecting the temperature and axial strain randomly and comparing with data demodulated from the sensing matrix, the corresponding maximum temperature and axial strain errors are measured to be
$0.172~^{\circ }$
C and
$27~\mu \varepsilon $
, respectively. The proposed sensor is demonstrated to be capable of simultaneous sensing accuracy and potential applications in dual-parameter detection.