Optics & Laser TechnologJ~, Vol. 28, No. 6, pp. 457-461, 1996 Copyright C 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved OO30-3992/96 $15.00+ 0.00 0030-3992(95)00076-3 Acousto-electro-optic demultiplexers in high data-rate optical commu nication systems M. A. G. ABUSHAGUR, A. HELALY Acousto-electro-optic scanners are introduced as time-division demultiplexing devices in optical fibre communication systems. These devices can time-demultiplex digital signals with multiple Gb s-’ data rates into a large number of channels. Acousto-electro-optic scanners combine the advantages of the large throughputs of acousto-optic scanners and the wide bandwidth of electro-optic scanners. Two-cell scanners are also introduced as a mean of increasing the time resolution by a factor of two compared with one-cell scanners. Copyright @ 1996 Elsevier Science Ltd. KEYWORDS: scanners, demultiplexers, optical communications, acousto-electro-optics Int:rodlIction Time-di1’1sion multiplexing (TDM) is a technique by whlll:h si,: lals from a number of channels are interleaved in time i 1 to a single digital signal with larger bandwidth. At the transmit end, the multiplexer combines data from the input channels and transmits them over the high- capacity c:ommunications link. At the receiver, the denrlultiI,llexer separates the data of the multiplexed signals ar d delivers them to the appropriate output line::;. Act: usto -optic deflectors (AODs) have been used as light beam SC; tnners in which the optical power of an incident beam is zlelivered in time sequence to different locations. Scannin::: the deflected optical beam is achieved by cha.:lginl,; the frequency of the drive signal. The acousto- optic scanners (AOSs) can operate in random access mode w:~re the frequency is changed in steps, or in analogul: mode where the frequency is changed linearly with time (linear FM mode). In both cases, the position of the foc,used spot at any time depends upon the drive frequenc,J, at that time. In a previous work’, the fealsibilify of using an acousto-optic scanner (AOS) as a time-diviGon demultiplexer (TD DEMUX) was introduced. It was shown that linear FM mode can prcGde demultiplexing of higher instantaneous data rates more than those provided in random access mode. In tlOSs with linear FM mode, the deflector must be blanked during the transit time. This necessitates no data trail;jmission during this interval, and therefore, the average data rate is less than the instantaneous one. It --- The authors are in the Department of Electrical and Computer Engineering, University of Alabama in Huntsville, Huntsville, AL 35899, USA. Received 7 February 1995. Revised 1 June 1995. has been shown’ that the average data rate can be maximized if the sweep interval of the drive signal is two-times larger than the aperture time. In this case, the maximum average data rate is one-half the instantaneous one. We show in this paper that using a two-scanner demultiplexer can allow the transmission of data all the time, and makes the average data equal to the instantaneous one. This DEMUX consists of two AOSs that are illuminated alternately, each for one-half the sweep interval. We also show that the resolution of a DEMUX can be increased by cascading two AOSs whose drive signals have linear FM rates with opposite signs. The data rate of the signal to be time-demultiplexed is limited by the frequency bandwidth of the AOS and the linear FM rate. We propose applying an electric field across an anisotropic AOS, which results in an acousto- electro-optic scanner (AEOS) that has much wider bandwidth, and consequently allows time- demultiplexing of digital signals with much higher data rates. These scanners have the advantage of large throughputs, as in AOSs, and high data rate demultiplexing, as in electro-optic scanners (EOSs). Analytical and computer simulations for AEOs will be shown, including the increased bandwidth and the required electric field. Analysis In an acousto-optic deflector (AOD), a light beam incident at an angle Qiis deflected at an angle 6d where zyxwvutsrq Af sin 6d = - - sin 8i V (1) where v is the acoustic velocity in the interaction medium, X is the optical wavelength, and .f is the 457