Holographic Optical Elements for optical backplane bus targeted at high speed data transfer

摘要

The primary technical challenge for optical backplanes involve the alignment and optical isolation of multiple data channels. Since most backplanes require data transfer rates greater than a single optical channel can cost-effectively provide, multiple data channels is the common solution for higher aggregate transfer rates. Established optical alignment and isolation techniques include spatial separation of optical channels, use of lensing elements to focus specific transmitter outputs to specific receiver areas, use of differing wavelengths for adjacent channels with appropriate frequency filtering on receivers, and the use of "light guide tubes" for each channel. This presentation will examine another promising option, the use of "matched" Holographic Optical Elements (HOEs) to provide both cross channel optical isolation and to significantly relax traditional optical alignment requirements. Matched HOEs can both induce upon a transmitted optical stream, and then filter upon a received optical stream, a number of distinguishing characteristics such as wavelength, polarization, phase, and amplitude. Thus the use of a unique "matched HOE" pair with each transmitter-receiver pair of multiple optical data channels can provide an efficient mechanism to isolate individual data streams even when they may be physically coincident, such as in a length of fibre optic or when multiple free space data transmitters illuminate several channel's receiver elements. Thus, the alignment issue is relaxed from the usual constraint of attempting to physically separate channels to one where, as long as the receiver is within the optical cone of it's matched transmitting element, cross channel interference can be effectively eliminated.