Feedback-injected erbium fiber laser with selectable tunability and constant single-longitudinal-mode characteristic

In this investigation, a wavelength-selected single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser utilizing C-band EDF based gain medium over a tuning bandwidth of 1524.0 to 1573.0 nm is demonstrated experimentally. A self-injection Rayleigh backscattering (RB) is designed in the EDF ring laser configuration to suppress the multi-longitudinal-mode (MLM) oscillation and narrow the obtained linewidth. Here, the physical output features of the proposed self-injected RB EDF laser are also studied and discussed, such as the optical signal to noise ratio (OSNR), output power, and laser linewidth, respectively. Therefore, the demonstrated EDF laser not only can reach SLM output, but also can produce a flat output spectrum of 1524.0 to 1554.0 nm with 0.2 dB power variation. Moreover, the measured fluctuation of each wavelength can be kept at ±0.05 nm based on the presented self-injected RB EDF laser, while the uncertainty issue is also considered.