High-Precision Tunable Single-Frequency Fiber Laser at 1.5 μm Based on Self-Injection Locking

A high-precision tunable single-frequency fiber laser (T-SFFL) at
$1.5~\mu \text{m}$
based on self-injection locking is experimentally demonstrated. By virtue of an effective filtering and self-injection locking scheme, a stable single-longitudinal-mode operation of the fiber laser is obtained. The fine wavelength tunability is implemented by stretching a uniform fiber Bragg grating in the self-injection loop, and the laser wavelength is tuned from 1550.28 to 1560.40 nm with a tuning accuracy of less than 54 pm. In the whole tuning range of 10.12 nm, an output power of approximately 5 mW and an optical signal-to-noise ratio of 71 dB are synchronously obtained with this laser system. Additionally, the measured laser linewidth is less than 630 Hz and the relative intensity noise is lower than −149 dB/Hz at frequencies from 0.4 to 7.5 MHz. It is believed that this 1.5
$\mu \text{m}$
high-precision T-SFFL can be a promising candidate for the optical communications system applications.