Fiber optic parametric amplifiers in single and multi wavelength applications
Abstract: This thesis describes fiber optical parametric amplifiers (FOPAs) used in single- and multi-wavelength channel applications. The FOPA was operated as a pulse source in optical transmission systems at bit rates of 10-160 Gb/s. It was evaluated in terms of bit error rate after transmission with link lengths up to 650 km. The generated idler pulses were found to be limited by timing jitter due to phase modulation on the pump. A multi wavelength pulse source was also presented. A theory describing the pulse width and chirp of the FOPA generated pulses was furthermore derived and compared to experiments, showing good agreement. The use of FOPAs as amplifiers in multi wavelength systems was also evaluated. It was found that two phenomena deteriorate the performance; cross-gain saturation and four wave mixing. The FOPA was used as a preamplifier in a receiver and was evaluated both in a loop mirror configuration as well as in a high gain configuration. The loop mirror configuration allowed for a virtually loss-less combination of the pump and signal. The fiber gain in the FOPA was measured to 70 dB, which is the highest reported single stage gain in an optical amplifier. The high gain configuration single-stage FOPA had similar performance as a dual-stage Erbium-doped fiber amplifier at 100 Mb/s. Additionally, a technique based on optical time domain reflectometry was developed and used as a measurement tool for measuring gain and bandwidth evolution along the nonlinear fiber used in FOPAs. To some extent this method also made it possible to retrieve information about fiber parameters as a function of length.
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