Experimental and theoretical studies of a harmonically modelocked erbium fiber ring laser

This thesis presents a comprehensive experimental characterization and a theoretical analysis of a harmonically modelocked erbium fiber laser that is compatible with the current and future demands of high speed data communication and signal processing systems.; This laser generates a train of coherent, transform limited Gaussian pulses with pulsewidths in the range of 18-50 ps at a 5 Gb/s repetition rate and 10 ps at a 10 Gb/s repetition rate. The lasing wavelength is continuously tunable from 1532 to 1564 nm. The basic structure of the laser is a 16.8 meter ring of optical fiber in which the light travels in one direction. The gain medium is a 5 meter section of erbium doped fiber. In each round trip, the light also passes through two frequency filters and an amplitude modulator. A broadband Fabry-Perot filter sets the wavelength and a narrowband Fabry-Perot filter prevents unwanted cavity modes from lasing. The modulator couples energy between the selected modes and locks these modes in phase. The steady state output of this laser is a set of well defined frequency modes corresponding to a train of transform limited picosecond pulses.; A drawback of fiber lasers is their sensitivity to small temperature fluctuations, so that they must be actively stabilized. Our novel stabilization technique utilizes a narrowband Fabry-Perot filter with a feedback phase locking circuit to track the variation of cavity modes.; In addition to the experimental demonstration, a theoretical analysis has been completed. Out analytical theory extends Siegman and Kuizenga's standard modelocking theory to include the effects of birefringence, modulation frequency detuning, cavity length offset, and the effects associated with the presence of Fabry-Perot filters. We also present numerical simulations that confirm the analytical theory and include the effects of third order dispersion and laser build-up noise. These theoretical results can be used to help design of similar modelocked fiber lasers with a wide range of operating parameters.