Broad-Band Fiber Amplifiers And Light Sources For Optical Communication

The optical fiber amplifiers and light sources are key devices in densewavelength division multiplexing (DWDM) transmission systems. This dissertation isfocused on broad-band fiber amplifiers and light sources for optical communication,which include:1. Broad-band erbium-doped fiber amplifiers (EDFA) 1) The intrinsic flat gain characteristics and dual-stage configuration mechanics of L-band EDFA are investigated by Optiwave corporation's simulation software (OptiAmplifier 4.0). Without gain equalized filter (GEF), gain spectrum is flat on optimum population inversion level and low noise less than 6 dB is achieved with the configuration. 2) Experimental investigation on C+L band with parallel configuration is carried out, and a novel simple structure is proposed. The small signal gain and band width are obtained more than 20 dB and 70 nm, respectively.2. Broad-band Raman fiber amplifiers and hybrid EDFA/FRA 1) The optimal design method for flat-gain broad-band FRA is presented using OptiAmplifier 4.0. With seven proper pumps, the relative gain flatnesses are all less than ±0.5 dB within the bandwidths of 80 nm (1530~1610 nm). 2) A finely gain-flattened broad-band hybrid amplifier is simulated by using OptiAmplifer 4.0. With an extremely large seamless bandwidth of 75 nm (1530-1605 nm) and a significantly enhanced optical signal-to-noise ratio, the hybrid amplifier is realized using a discrete FRA, a C-band EDFA, and a gain equalizer.3. Multiwavelength SOA-fiber ring lasers (SFRL) 1) A FBG based dual wavelength SFRL is proposed using two different central wavelength FBGs, which act as frequency selective filters. And at room temperature, stable dual wavelength is obtained. 2) Based on SOA and F-P comb filter, seven wavelengths are obtained in the ring-cavity configuration, with high stability and the wavelength spacing about 2.7 nm. The SNR of each channel is more than 29 dB and the output power relative fluctuation ratio is less than 4%. IIABSTRACT 3) We propose a novel switchable multiwavelength fiber ring laser based on SOA, which uses a Hi-Bi fiber loop mirror (Hi-Bi FLM) as filter. More than 15 wavelengths with linewidth about 0.1 nm spacing on ITU-grid (100GHz) are obtained, and the output power relative fluctuation ratio is less than 12%.4. Tunable fiber ring lasers 1) We demonstrate a novel approach to obtain a narrow linewidth laser with 35 dB sidemode suppression by utilizing a SOA in a fiber unidirectional ring that consists of a linear polarizer, 1.28 m Hi-Bi fiber and polarization controllers. The laser has a widely tuning range of 49 nm (1555~1604 nm), which is the best result with similar method until now. 2) A wavelength-selectable discretely tunable erbium-doped fiber laser in C-band is fabricated using a precise multi-wavelength grid filter (Hi-Bi FLM) and a channel-selecting tunable filter. With 41 channel operation of ~100 GHz channel spacing, the laser is suitable for DWDM sources.