John L. Stacy

Five Gb/s operation of a 50-channel optical interconnect

The architecture and experimental demonstration of a novel optical time-division multiple-access (TDMA) interconnect is presented in detail. Optical multiplexing and synchronization is used to overcome the electronic multiple-access bottlenecks associated with gigahertz-bandwidth multiprocessor communication systems. A self-clocking optical TDMA interconnect is described that may be more practical to implement than other shared-medium multiple-access protocols, such as frequency division or code division. An experimental optical TDMA interconnect is reported that uses a 100-MHz repetition rate, mode-locked laser with external modulators to generate the base-band data, and operates at a multiplexed data rate of 5 Gbits/s accommodating up to 50 channels. System measurements reveal bit error rates of less than 10 -9 , low channel crosstalk, and subnanosecond multiaccess capability. A power budget analysis predicts that 100 Gbit/s systems with 1000 nodes are feasible.

Time-division optical micro-area networks

Optical micro-area networks (iANs) are proposed as a way of providing flexible communications among VLSI processors and eliminate electrical I/O bottlenecks. Sharedmedium multiple access protocols in jtANs can avoid the access delays associated with statistical multiple access protocols (which are unacceptable in multiprocessor applications) and increase the throughput at the expense of wasting optical bandwidth. Time-division multiple access (TDMA) may be more practical to implement in a pAN than other shared-medium multiple access protocols such as frequency-division or code-division. Since the total throughput of TDMA is given by the inverse of the optical pulsewidth the throughput can be increased by making the pulse width small. Accomplishing this goal requires avoiding the use of low-bandwidth electronics in the portion of the iAN that directly processes these short pulses. Instead optical processing can be used in those protions of the network. The architecture of a TDMA pAN which uses optical multiple access processing and is self-clocking is described in detail. Experimental demonstrations of key subsytems for optically generating modulating synchronizing delaying and correlating short optical pulses are presented. The feasibility of a variable-integer-delay line which provides rapid tuing wide tuning range and high precision is demonstrated. A transmitter consisting of a mode-locked laser with an external modulator is used in the TDMA iAN since arbitrarily short pulses can be controlled with a modulator that need only operate at the bit rate which translates© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Free-space optical TDM switch

A free space optical TDM switch at 1.32 micron is experimentally studied. The architecture of a TDM circuit switching system with a fixed transmitter and tunable receiver assignment is described. Since each user of the TDM switching system is assigned a time slot on the time frame, the corresponding receiver at the output looks only in the preassigned time slot for signal recovery. The electrical data signal from the input source is used to gate the optical pulses from the centralized source for the duration of the signal. It is concluded that large input/output switching systems are feasible.

Demonstration of an optically transparent ATM packet switch node

We report on the development of a transparent optical node at 1.3 micrometers wavelength for an ATM packet switch operating at 1.24416 Gbit/s header recognition rates. The node takes advantage of the high-speed performance of optoelectronic components to alleviate potential bottlenecks resulting from optical to electrical conversion experience in nontransparent packet switching architectures. The node is intended for use in two-connected, slotted networks, is self-clocking, and has drop/add multiplexing, buffering, and routing capabilities.