Development and Characterization of Multi-Wavelength Fiber Laser Light Sources Based on Erbium and Brillouin Gain

This thesis presents the research works that has been carried out in the development and characterizations of light sources based on two gain medium, namely Erbium and Brillouin. The laser gain medium used in the research work is in the form of optical fiber rather than bulk piece of doped crystal or glass. The physical structure of the gain medium makes it easy to be spliced with other optical components in the Fiber laser configurations. The Brillouin gain comes from a standard single mode fiber used in the optical fiber communication system. The aim of the research work is to investigate various techniques in Fiber laser that allow the generation of multiple laser output (or multi-wavelength) from a single light source unit. The techniques differ from each other in the wavelength selection mechanism and the gain medium used in the configurations. In the first experiment, optical fiber Bragg grating has been chosen as the wavelength selective technique. Through this configuration, a dual and switchable laser output can be constructed. The output of the laser can be made to switch between single wavelength or with both wavelengths lases simultaneously. A moderate laser output power (about 10 mW at 60 mW EDF pump power) has also been achieved with both output power has a uniform power level. The multi-wavelength output can be easily increased through the addition of more optical fiber Bragg grating. Through a linear fiber laser configuration which incorporates Fabry-Perot band-pass filter, a dual laser output system has been demonstrated. A novel technique has been suggested which allows for a uniform output power levels at any wavelengths within the EDF allowable gain profile. This was achieved by varying the optical attenuator values placed at one of the laser cavity loops such that it changes the cavity loss at that particular wavelength of interest. Finally, by combining two gain medium within a laser cavity, a fiber laser system that is capable of achieving high number of laser outputs is being constructed. The mechanism that is responsible for the generation of the multiple laser output is the Stimulated Brillouin scattering phenomena and the feedback loop that is incorporated within the laser cavity. Output of more than 20 laser lines could be achieved with such configuration. Besides producing a high number of laser lines, the output can also be made tuneable within a wide range. A tuning range of up to 34 nm has been demonstrated for a ring laser configuration and 17 nm for linear laser configuration. The work presented in this thesis also reported for the first time a tuneable L-band Brillouin/Erbium fiber laser system adopting a linear laser cavity. A tuning range of up to11 nm can be achieved with average laser output of 10 signals.

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