Simultaneously improving the linewidth and the low-frequency relative intensity noise of a single-frequency fiber laser

By optimizing the pump intensity noise, simultaneous improvements in the linewidth and the low-frequency (<20 kHz) relative intensity noise (RIN) of a 1550 nm single-frequency fiber laser (SFFL) are demonstrated. A lower-RIN distributed feedback laser diode with optoelectronic feedback replaces the fiber Bragg grating laser diode to pump the SFFL. As a result, the linewidth of the SFFL is narrowed from 1.3 to 0.65 kHz and the RIN is decreased by about 7–11.5 dB from 0.2 to 5 kHz, and by about 3–7 dB from 5 to 10 kHz. The improved SFFL is an ideal laser source for fiber-optic sensing applications.