Abstract

Optical wavelength-division-muitiplexing (WDM) is attractive to realize large capacity optical communication systems and networks [1]-[6]. The wideband amplification of WDM signal is indispensable to increase the transmission capacity. Over 20 nm wideband transmission experiments were reported employing wideband optical fiber amplifiers [4], [6], The gain imbalance of such wideband amplifiers is a serious problem because it accumulates across the amplifier stages; the level difference between channels grows with stage number. As a result, transmission distance was restricted by signal-to-noise ratio (OSNR) degradation and non-liner effects. Because, optical gain equalizers (GEQ) are indispensable to compensate the gain imbalance, several optical gain equalizers have been studied recently including a Mach-Zehender filter [1], a fiber grating [3], and a lattice type optical circuit [7], The lattice type optical circuit is especially attractive due to its precise tunability and the ability it provides to design the transmittance with wideband equalization range.

© 1996 Optical Society of America