Characterisation of cascaded EDFA with the inclusion of an interstage optical element

Erbium-doped fibre amplifiers (EDFA) have been widely used for long haul transmission and are already in place for WDM applications. We characterised cascaded optical amplifiers by comparing their performance while operating with and without an interstage optical filter. It is noticeable that the 3 nm filter improved the gain (G) and output signal power (P/sub sout/) by as much as 9.72 dB and 9.75 dB respectively at a signal level of -50 dBm.