Analysis of optical gain enhanced erbium-doped fiber amplifiers using optical filters

Erbium-doped fiber amplifiers (EDFAs) with enhanced optical gain obtained by incorporating narrow-bandpass optical filters into the amplifier length are studied. It is shown in theory that it is possible to increase optical gain by more than 10 dB for optical signals around the wavelength of 1.55 mu m, compared with conventional EDFAs without filters. It is also shown that the gain improvement at longer wavelengths away from the amplifier gain peak is much higher than that of the EDFA with an optical isolator within the amplifier length. The optimum filter position is found to be around 42% of the total amplifier length from the input end. The effects of filter insertion loss and pump loss are discussed. This amplifier can be used as an optical preamplifier in a receiver for a wide range of wavelengths.<
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