| This thesis discusses the very important components in wavelength-division multiplexed (WDM) fiber-optic communication systems—fiber laser sources and fiber Bragg grating filters. Three areas are included: theoretical studies of fiber ring resonators with an external reflector (FRRER) and compound ring resonator with an external reflector (CRRER); implementation of erbium-doped fiber lasers (EDFLs) based on the proposed passive resonators; and theoretical studies of phase-shifted fiber Bragg grating filters.; An FRRER is made with a ring resonator, a coupler and a reflector, while a CRRER made with double ring resonators, double couplers, and a reflector. We analyze theoretically both of the resonators with regard to their resonance conditions and directionality properties. The outputs and circulating intensities of the resonators are investigated. The optimum design relationships are obtained by examining the resonators. The result shows that both resonators are suitable for development of traveling-wave fiber lasers without use of optical isolators because of a high loss difference between the counter-clockwise and clockwise directions.; Whilst both resonators feature non-reciprocal property, comparing with the single resonator FRRER, the CRRER with double resonators has advantages of potentially large free spectral range due to vernier effect. The effects of the coupling coefficients, losses and resonant numbers on the resonance are discussed for the double resonators. These resonators have properties very suitable for the construction of lasers.; Based on the proposed resonators, erbium-doped fiber lasers are fabricated. As expected, the unidirectional operation is achieved in EDFLs without need of optical isolators. The robust single-longitudinal-mode operation is achieved by employing the compound ring resonator to enhance the mode selectivity. Based on the configuration of the FRRER, by adding another reflector to the other end of the coupler, we have demonstrated a novel erbium-doped fiber laser operating at two wavelengths. The benefit of this approach is simplicity, compact and low cost.; A phase-shifted fiber Bragg grating, when combining with optical circulator, it may be used as add/drop de/multiplexes, which has very useful application in WDM fiber-optic communication systems. A comprehensive theoretical analysis of the compound phase-shifted uniform fiber Bragg grating (FBG) filter is presented. The transmission characteristics are examined by a transfer matrix formulation. The result shows that by suitably choosing the ratio, a quasi-flat-top spectrum may be obtained. The general condition of the optimum case is derived. This characteristic makes the compound phase-shifted uniform FBG filter particularly advantageous. |
