ANALYSIS OF OPTICAL GAIN ENHANCED ERBIUM-DOPED FIBER AMPLIFIERS USINGOPTICAL FILTERS

This letter studies the erbium-doped fiber amplifiers with enhanced op tical gain by incorporating narrow-band-pass optical filters into the amplifier length. It has been shown in theory that it is possible to i ncrease optical gain by more than 10 dB for optical signal around the wavelengths of 1.55 mum, compared with the conventional EDFA's without filters. It is also shown that the gain improvement at longer wavelen gths away from the amplifier gain peak is much higher than that of the EDFA with an optical isolator within the amplifier length. The optimu m filter position is found to be around 42% of the total amplifier len gth from 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.