Combined frequency and amplitude modulation for the STARNET WDM computer communication network

STARNET is an experimental wavelength-division multiplexed computer communication network that makes use of combined modulation of a single transmitter laser to implement a virtual-ring control sub-network and a reconfigurable high-speed sub-network over a passive star architecture. In this letter, we demonstrate a new technique of combined modulation that works by direct frequency-shift keyed (FSK) modulation and external amplitude-shift keyed (ASK) modulation of a semiconductor laser. By adjusting the amplitude modulation depth to 0.8, both the 125 Mb/s ASK receiver and the 1.244 Gb/s FSK receiver operate with equal bit-error ratios less than 10/sup -9/ for a received signal power of -24 dBm.<
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