| Summary: | 碩士 === 國立東華大學 === 電機工程學系 === 94 === Because of the output power of pump laser diodes is increasing, fiber Raman amplifier can be practically employed in optical fiber communication system. The fiber Raman amplifier has two advantages: one is the low noise characteristic and the other is the arbitrary spectral gain band. It will play an important role in optical communication system. In high bit rate system, dispersion compensation technique is necessary to increase transmission distance. The dispersion-compensating fibers are the most widely used technology for dispersion compensation. The DCF can be used not only as a dispersion compensating medium but also as an amplifying medium of discrete Raman amplifier.
In this thesis, we set up three different configurations of discrete broadband Raman fiber amplifiers with 7.3 and 15.4 km dispersion compensation fiber and using six-wavelength channel WDM pump laser diode unit, and the bandwidth achieved 96 nm. At first, we use 7.3 km DCF to set up single-pass dispersion compensation broadband Raman amplifier. This configuration can compensate the dispersion and loss of 40 km single mode fiber, than we get 15.1 dB average net gain and gain flatten is 1.14 dB. In order to enhance system performance, we increase two times of gain medium length up to 15.4 km and the DCF compensate dispersion of 80 km single mode fiber. But the efficiency couldn’t enhance double as expected, the system only get 16.4 dB average net gain. Furthermore; we employed an optical circulator, Faraday rotator mirror and a 7.3 km DCF to set up reflective type dispersion compensation broadband Raman amplifier. The purpose is to reflect the signals back into the gain medium. This configuration enhance 3 dB net gain, we get 17.8 dB average net gain and the gain flatten is 2.37 dB. In addition, the noise figure of short wavelength decreased, lead to the whole noise figure flatten decreased from 6.31 dB to 2.64 dB.
In this research, we know the employ of FRM in reflective type Raman amplifier can compensate loss and dispersion of 80 km single mode fiber with 7.3 km DCF, and the bandwidth achieved 96 nm. Furthermore; the net gain of reflective type Raman amplifier than that of single-pass Raman amplifier can enhance 3 dB. The polarization mode dispersion of the dispersion compensating fiber can be almost compensated by FRM. Reflective type dispersion compensating broadband Raman amplifier is necessary in long transmission distance and high bit rate systems.
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