Towards Network Transparency with Photonic Amplifiers

Abstract : Over the past 15 years optical fibre transmission systems have largely replaced their copper forebears on a point to point basis. The approach has been, quite simply, to overlay one-on-one the copper and radio systems by an optical fibre network with improved repeater spacing, smaller physical size, increased capacity and lower cost being the key benefits gained so far. With the advent of the optical amplifier and the possibility of access to the total fibre bandwidth, insensitivity to 'lossy' components and the eradication of much of the electronics necessary in transmission, there now exists an opportunity for radically new forms of network. The key feature that an optical amplifier has to offer is transparency. The ability to convey a number of wavelengths that can act as independently-modulated orthogonal carriers for a diverse mix of traffic in both digital and analogue forms offers a revolutionary step in the evolution of telecommunication networks. Much of today's thinking with respect to photonic amplification is still concerned with the one-on-one replacement of opto-electronic 3R repeaters, coupled with the achievement of higher launch powers and pre-amplifiers for optical receivers. However, the optical amplifier in all its diverse forms offers a much greater opportunity when we consider equipment, system and network realisation more deeply. In this paper, we briefly comment on the state-of-the-art of today's optical amplifier technology and then go on to postulate future advances and applications for local, short, and long haul applications.