Ultralow-Noise Single-Frequency Fiber Laser and Application in High-Resolution Fiber-Optic Dynamic Strain Sensing

A 1.5 mu m ultralow-noise single-frequency fiber laser (SFFL) is realized based on a delay fiber phase-locked method and the nonlinear amplification effect of a semiconductor optical amplifier (SOA). Via feedback locking of the phase jitter signal, the phase noise achieves the minimum value of -160 dB rad Hz(-1/2)m(-1) with a maximum reduction of 50 dB. Meanwhile, SOA reduces the intensity noise by a maximum of 65 dB, making it near the shot-noise limit for frequencies above 40 kHz. To demonstrate this state-of-art SFFL with ultralow-noise property, a high-resolution fiber-optic dynamic strain sensing based on a fiber-based Michelson interferometer (FMI) is performed. As a result, the strain resolution reaches 26 f epsilon Hz(-1/2) in the 30-200 Hz band, which is improved by almost three orders of magnitude than that realized by a free-running SFFL. To the best of the knowledge, this is the first time to achieve such a high-resolution fiber-optic dynamic strain sensor in the low-frequency range utilizing the FMI system. This high-resolution fiber-optic strain sensing has promising applications in geophysics and biophotonics. Moreover, this ultralow-noise SFFL is competitive for sophisticated applications, such as precise absolute distance measurement, quantum key distribution, and generating squeezed light.