Combined modulation formats for the STARNET coherent wavelength-division multiplexed computer communication network

urrent computer networks based on shared channel architectures and electronic switching are not adequate to support future broadband services. Multi-channel all-optical approaches will be more efficient and are now being investigated. One technique for constructing multi-channel fiber optic networks is wavelength-division multiplexing (WDM). With WDM, each user transmits on a different wavelength, therefore, allowing multiple channels on the same optical fiber.;One problem in implementing WDM networks is control of reconfigurable high-speed data connections. STARNET is an experimental WDM network being investigated at Stanford University. To solve this control problem, STARNET utilizes combined modulation of a single transmitter laser, a main receiver, and an auxiliary receiver in each node. High-speed data are transmitted by angle modulation and received by the main receiver while moderate-speed control data are transmitted with the same laser by low-level amplitude modulation and received by the auxiliary receiver. Through this design, STARNET offers all users both a moderate-speed, logical, packet-switched control sub-network and a logical, reconfigurable, high-speed sub-network on a passive physical star topology.;This thesis investigates two techniques of combined modulation. The first technique utilizes combined phase shift-keyed and amplitude shift-keyed (PSK/ASK) modulation. In this experiment, an integrated phase and amplitude modulator and a Nd:YAG laser are used to transmit 125 Mb/s ASK data and 2.5 Gb/s PSK data on the same lightwave. For simultaneous operation, the optimum ASK modulation depth is 0.57 and the combined receiver sensitivity is ;Combined phase and amplitude modulation works well with Nd:YAG lasers but does not work with semiconductor lasers due to their large linewidths. Since practical WDM networks will require the use of semiconductor lasers, we propose a combined modulation technique that works with semiconductor lasers. With this technique, high-speed data are transmitted via 1.244 Gb/s direct frequency modulation (FSK) of a semiconductor laser while moderate-speed data are transmitted via 125 Mb/s external ASK modulation. For simultaneous operation, the optimum ASK modulation depth is 0.8 and the combined receiver sensitivity is...