Alan Lelah

CMOS VLSI pilot and support chip for a liquid crystal on silicon 8x8 optical cross connect

With the explosion of Internet and multi-service traffic, telecommunication transport networks today are turning to Wavelength Division Multiplexing. Optical cross-connects (OXCs) allow flexible rerouting of wavelength channels. It has been shown that 2-D free-space beam deflection by nematic liquid crystal gratings provide a good solution for the realization of optical switches in OXCs. Operating in the telecom 1.5 micrometers wavelength region they serve as an active holographic element. Liquid Crystal on Silicon (LCOS) combined with VLSI technologies allow the fabrication of large capacity, low cost and low consumption compact free-space switches. An N X N optical switch can be built by cascading two LCOS-based spatial light modulators (SLMs). The first part of the paper describes a circuit that provides the physical support as well as piloting circuitry for such SLMs. It is capable of piloting beams from a linear array of 8 incoming fibers towards a similar array of 8 outgoing fibers. The electrode command voltages are analog while the external interface as well as on-chip memory is digital. The chip has been implemented in a CMOS 0.5 (mu) process with 600,000 transistors while die size is 320 mm2 (80 mm2 active area).

A definition of mobility

This study proposes to give a definition of mobility that can be used as a reference in the field of telecommunications. It also presents the methodology which was employed to get to this definition.