<title>Holographic optical elements for free-space clock distribution</title>

Abstract

Optical clock distribution is an attractive technique to avoid clock skew in highspeed digital systems. For short lengths free space distribution by holographic optical elements (HOE) has specific advantages. We will report on the requirements of the optical system in respect of necessary light power and its equipartition to the photoreceivers. We give an estimation for the maximum number for optical fan-out considering especially ECL circuits. Specific system constraints lead to a certain layout for the whole arrangement. The realization of a distinct HOE type is carried out in form of a binary phase reflection HOE which is produced by dry etching of silicon. The measured diffraction efficiency is close to the theoretical limit.

Optical interconnections within multichip modules

“…The efficiency is much higher than for the unfocused case, but the precision in the alignment has to be very high. To accomplish these interconnections, several solutions have been proposed that concentrate on techniques to achieve large fan-out and reduce alignment problems.24'25 In particular, Zarschizky et al 25 determined that a maximum fan-out of 50 is feasible with an optical laser power of 1 mW and a 40% efficiency of the hologram at 1-Gbps clock frequency. The rest of this paragraph summarizes that study.…”

Optical Clock Distribution With A Compact Free Space Interconnect System

“…This is due to the coding problem of the computed pattern data because the DOE has an enormous space bandwith product. Details about the DOE design, the choice of the facetted DOE version and about the calculation and coding principle can be found in [2,3,41. The realisation of the DOE is based on the use of well advanced semiconductor technologies: CAD, E-beam writing, step-and-repeat-cameras, reactive ion etching etc.…”