A dual-wavelength erbium-doped fiber laser for high resolution strain sensing with compound filter of a Sagnac loop and a long period fiber grating.

• A dual-wavelength erbium-doped fiber laser (EDFL) for strain sensing with compound filter of a Sagnac loop and a long period fiber grating (LPFG) is proposed and experimentally proved. • The proposed strain-sensing system combines fiber-laser technology, sensing technology, interference technology, and filtering technology. • The proposed EDFL enables flexible laser outputs of single-wavelength and dual-wavelength through adjusting the compound filter. The wavelength tuning range of the single-wavelength output laser exceeds 10 nm. • The strain is measured through monitoring the output wavelength shift in the EDFL. Owing to the sensitivity of the output wavelength to strain and the sharp spectrum in EDFL, the strain measurement sensitivity reaches 8.33 pm/με with a high resolution of 2.4 με. A dual-wavelength erbium-doped fiber laser (EDFL) strain sensing system composed of compound filter of a long period fiber grating (LPFG) and a Sagnac loop is proposed. Polarization maintaining fiber (PMF) in Sagnac loop acts both an interference filter and a strain sensing probe with high sensitivity, low cost, and low loss. LPFG is used to modulate the transmission wavelength and bandwidth of EDFL through adjusting its bending curvature. Flexible laser output with single wavelength and dual-wavelength tunable wavelength band of 10 nm is achieved in EDFL. The measurement sensitivity of strain reaches 8.33 pm/με, while the 3 dB linewidth is less than 2 nm and the signal-to-noise ratio (SNR) exceed 36 dB. This sensor has a high resolution (R) of 0.11 nm and a high quality factor (Q) of 38.13. The experimental results suggest that the system is suitable for precise strain measurement and has significant potential in fields like biomedicine, environmental monitoring, health monitoring, and aerospace. [ABSTRACT FROM AUTHOR]