Wavelength-tunable erbium fiber ring laser in single-frequency operation utilizing Fabry–Perot laser with Sagnac cavity

We propose and demonstrate experimentally a stabilized and wavelength-selective erbium-doped fiber ring laser in single-longitudinal-mode operation with Fabry–Perot laser diode (FP-LD) and using a tunable bandpass filter (TBF) inside and outside a Sagnac ring cavity. The side-mode suppression ratios of 21 dB and 36.5 dB and the output power of –3.6 dB m and –8.7 dB m in the wavelengths of 1524.45–1562.35 nm and 1531.07–1562.35 nm with the tuning step of 1.4 nm can be achieved when the TBF outside and inside Sagnac loop, respectively. The output wavelength variation of zero and the output power fluctuation of <0.1 dB are also obtained. Moreover, the transmission efficiency of the ring laser has also been performed experimentally under a 1.25, 2.5 and 10 Gb/s external modulation, respectively.