Multiwavelength Single-Longitudinal-Mode Brillouin–Erbium Fiber Laser Sensor for Temperature Measurements With Ultrahigh Resolution

A multiwavelength single-longitudinal-mode (SLM) Brillouin–erbium fiber laser sensor with ultrahigh resolution is proposed and investigated experimentally. The one short common cavity with 50 m of single mode fiber (SMF) as the fiber under test and 100 m of SMF as the reference can effectively reduce the external perturbations and the cost. With the configuration that uses a fiber Fabry–Pérot (FFP) filter, every Stokes wavelength maintains SLM status, which can lead to the higher temperature resolution. In the experiment, 3.104 MHz/
$^{\circ}\hbox{C}$
sensitivity of the third-order Stokes wavelength is demonstrated, which is three times that of the first-order Stokes wavelength. A less-than
$0.2\ ^{\circ}\hbox{C}$
temperature error is obtained for every Stokes wavelength. In contrast, with a beat frequency linewidth of a different order Stokes wavelength, approximately
${10\ ^{-6}}^{\circ}\hbox{C}$
ultrahigh resolution in the short term is acquired at the third-order Stokes wavelength. This proposal can provide a feasible temperature sensing scheme with high sensitivity, high precision, and low-frequency detection.