A high-gain EDFA design using double-pass amplification with a double-pass filter

An erbium-doped fiber (EDF) amplifier configured in a double-pass amplification scheme together with a midway bandpass filter is presented to provide a gain as high as 37.5 dB with a noise figure of less than 6 dB. The system provides a gain improvement of as much as 9.5 dB from the double-pass system without filter. The system also can easily be upgraded to support dense wavelength-division-multiplexing (DWDM) transmissions by using a multiwavelength filter. Using a pair of four-channel DWDM multiplexer and demultiplexer, a gain of 39.53 dB for each of the channels was achieved. At the bit-error rate of 10/sup -9/, the proposed design supports the input level as low as -43 dBm with a gain of 37 dB. This is all achieved with the EDF length of 7 m and pump power of 90 mW.