Amplitude Modulated Harmonic Mode-Locking Characteristics of Er3+ Doped Fiber Ring Laser

In this paper, characteristics of amplitude modulated harmonically mode locked (AM-HML) erbium doped fiber (EDF) ring laser are presented. It is investigated that the AM-HML method can provide a precise control of the lasing spectral bandwidth. Which in turn, can control the nonlinear effects in single mode fibers, such as stimulated Brillouin scattering in optical fiber communications. The optical spectral bandwidth is found to be broadened from -5GHz to-16.6GHz when the AM modulating low harmonic signal frequency is varied from -3.1609MHz to -44.2526MHz (1 to 14 times of the fundamental cavity frequency fa) at a fixed pulse rate of fh 2.1241 GHz. The effect of the percentage of AM modulation depth is also studied and it is observed that the bandwidth of the AM-HML laser is slightly affected when the percentage of AM modulation is varied from -5% to -50%.