Four wave mixing in semiconductor optical amplifiers and erbium doped fiber lasers

Four Wave Mixing (FWM) in a semiconductor optical amplifier (SOA) is a third order nonlinear effect, which has various potential applications in high-speed optical communication systems. Continuous-wave (CW) FWM in a 2-section SOA has been experimentally studied. The carrier density modulation and nonlinear gain effects in the semiconductor optical amplifier contribute to the generation of the FWM. A theoretical model of CW FWM and frequency response of FWM using small signal analysis has been developed. Bandwidth of the FWM has been obtained for the first time. Pulsed FWM in the 2-section SOA has also been studied and analyzed. Optical time-division demultiplexing and wavelength conversion using the FWM in the SOA has been demonstrated for optical communication. ^ A tunable Erbium doped fiber laser, which is preferred in the FWM experiments and is potentially an important source for high speed optical communication, has also been investigated. The tunability of the fiber laser is about 40 nm for both CW and mode-locking cases. Actively harmonic mode-locking which happens when the modulation frequency fm = n fc (fc is the fundamental cavity frequency) and rational harmonic mode-locking which happens when fm = (n + 1/p)fc (n, p are both integers) have been studied and analyzed. 22nd order of rational harmonic mode-locking was observed when f m ≈ 1 GHz, which is the highest order of rational harmonic mode-locking ever reported. 40 GHz pulse train with pulse width ∼7 ps was achieved using rational harmonic mode-locking technique when f m ≈ 10 GHz. Stabilization of the mode-locked Er-doped fiber laser with a semiconductor optical amplifier in the cavity has also been studied. The semiconductor optical amplifier contributes in removing the supermode noise and stabilizing the optical pulses.