A variable gain optical amplifier for metro WDM networks with mixed span losses: a gain-clamped semiconductor optical amplifier combined with a Raman fiber amplifier

A variable-gain optical amplifier for metro-WDM networks of mixed span losses is demonstrated. It consists of low-gain Raman-fiber-amplifier and gain-clamped SOA. 16/spl times/10 Gb/s signals were successfully transmitted over 170 km (87dB) of mixed span losses under dynamic add/drops.

1. Introduction

In metro WDM networks; the span length is typically different and losses of spans may change due to the upgrade and reconfiguration of systems. This unequal span loss, as well as the gain transient due to channel add-drops, can make the system design difficult unless an optical amplifier for metro WDM networks can handle these two problems [1], [2]