Practical high speed optical processing using GaInAsP amplifiers

High speed communications systems have recently received great attention for incorporation into telecommunications networks. Significant advances have included optical time division multiplexing techniques, all optical processing nodes and soliton-like transmission over dispersion shifted fibre. However, the installed fibre base comprises mainly standard, fibre with chromatic dispersion of the order 16 ps/nm/km in the 1.5 μm window with regenerator spacings of the order of 40 km. Furthermore, the optical processing nodes must be compact, reliable and insensitive to environmental and signal state effects. The authors discuss recent work at BT laboratories towards the production of such an all-optical processing element, based on a standard GaInAsP travelling wave semiconductor amplifier (TWSLA). The use of this element in a 40 Gbit/s optically time division multiplexed network is discussed. In particular, a new all optical gate configuration, similar to the nonlinear optical loop mirror (NOLM) is discussed, and its application to an 80 km transmission experiment over standard fibre is presented