Abstract: An optical amplifier arrangement comprises a splitter for providing an input WDM optical signal on at least first and second output paths. An optical amplifier is provided in at least one of the paths, and a signal routing arrangement is provided for routing individual channels or groups of channels of the WDM signal within the at least one of the paths. A switch selects the signal from one of the at least first and second output paths. In this arrangement, there are two paths between the input and output. Whilst one path is being used, the components in the other path can be upgraded. For example, a switching arrangement may be provided in the other path, and an amplifier may also be upgraded, without disrupting service in the path in use. This enables an amplifying node within an optical communications system to be incrementally upgraded.

Abstract: The saturation effects observed in an MQW electro-absorption modulator are reduced by modifying the composition of the MQW structure so that the barrier layers, that are interleaved with the quantum well layers, are in tension.

Abstract: A method and system for enhancing the performance of feedforward amplifiers includes the provision of multiple sweep displays, one each for providing a display of a single performance characteristic of the amplifier. Various characteristics are monitored on an alternating and interleaved basis, and displayed during the intervals that they are monitored. The monitoring intervals are short enough so that each display appears to be continuous. The performance characteristics of the amplifier are thus observable on a real time basis, thereby facilitating adjustment of the amplifier to achieve optimum overall operation.