Two-section travelling-wave semiconductor laser amplifier optoelectronic time division demultiplexer

Optical time division multiplexing has been demonstrated as an efficient method of increasing the transmission capacity of optical fibre networks. Multi-section semiconductor travelling-wave laser amplifiers (TWLAs) have attracted interest recently for use in all-optical networks. A multisection TWLA along with associated circuitry may be used to demultiplex a TDM data stream in to two composite electrical channels or to select a channel from a multi-channel TDM system. Such an optoelectronic time division demultiplexer (OETDDM) enables the simultaneous detection and amplification of optical TDM signals while preserving full network transparency. The demultiplexing function is carried out optoelectronically so the requirement for high speed electronic demultiplexers is eliminated. A schematic diagram of the OETDDM shown. In order to model the device performance we need to solve numerically the equations coupling the signal (P) and the spontaneous noise photon densities (S⁺_λ, S^-_λ) travelling through the amplifying medium. These must be solved in conjunction with the carrier density (N) continuity equation for each section. The simulation results show that the OETDDM can perform optoelectronic demultiplexing or channel selection at bit-rates likely to be used in future B-ISDN systems. A small-signal analysis indicates that the signal to noise ratio of the OETDDM would approach that of conventional p-i-n photodetectors. The above simulations show that the OETDDM has potential to be used as an optoelectronic node in high bit-rate transparent optical networks.