µm Semiconductor Optical Amplifier Fiber Ring Laser by Using Gain-Switching Single-Mode FPLD

We demonstrate a novel approach for generating a stable and low polarization-sensitive mode-locked fiber ring laser by using a low-cost Fabry-Perot laser diode (FPLD) as both the intracavity mode-locker and the band-pass filter. The FPLD pulses is seeded into a close-loop semiconductor optical amplifier (SOA) based fiber ring laser for harmonic and rational harmonic mode-locking operation. The SOA biased at 65 mA and 18 o C combines with an intracavity optically feedback-injected 1.3 µm FPLD biased at 9.4 mA (below threshold current) and 23 o C via some optical couplers. Picosecond optical pulse with side-mode suppressing ratio of greater than 12 dB are obtained, the measured lindwidth at 3-dB and 10-dB decay are observed to maintain at about 0.04 nm and 0.14 nm, respectively. Narrow-linewidth operation of the SOAFL with optical pulsewidth of 42.1 ps and wavelength tuning range of about 10 nm at repetition rate of 13 GHz has been demonstrated. The optically injection mode-locking scheme also has shown to exhibit low supermode noise, higher average output power and good stability. The optical output power under harmonic mode-locked scheme is about 297 µW. The fluctuation in output power, the SSB phase noise at 1 kHz offset frequency, and the calculated rms timing jitter within the integral region from 0 Hz to 1 KHz are 2.5 µW, -82.4 dBc/Hz, and 1.0 ps, respectively.