Recent Free-Space Photonic Switches

Masayasu YAMAGUCHI  Ken-ichi YUKIMATSU  

IEICE TRANSACTIONS on Communications   Vol.E77-B   No.2   pp.128-138
Publication Date: 1994/02/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Issue on Photonic Switching Technologies)
free-space photonic switching,  optical switch,  two-dimensional array device,  optical interconnection,  

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This paper briefly reviews recent studies on free-space photonic switches, and discusses classifications, applications and technical issues to be solved. The free-space photonic switch is a switch that uses light beam interconnections based on free-space optics instead of guided-wave optics. A feature of the free-space switch is its high-density three-dimensional structure that enables compact large-scale switches to be created. In this paper, the free-space switches are classified by their various attributes such as logical network configuration, path-establishment method, number of physical stages, signal-waveform transmission form, interconnection optics and so on. The logical network configuration (topological geometry or topology) is strongly related to the advantages of the free-space switches over the guided-wave switches. The path-establishment method (path-shifting/branching-and-gating) and the number of physical stages (single-stage/multistage) are related to physical switching characteristics. Signal-waveform transmission form (analog/digital) is related to switch application. Interconnection optics (imaging system/micro-beam system) is related to the density and volume of the switching fabric. Examples of the free-space switches (single-stage, analog multistage, digital multistage and photonic ATM switches) are described. Possible applications for analog switches are subscriber-line concentrators, inter-module connectors, and switching networks for parallel or distributed computer systems. Those for digital switches include multistage space-division switches in time-division circuit-switching or packet switching systems (including asynchronous transfer mode [ATM] switching system) for both communications switching systems and parallel/distributed computer systems. Technical issues of the free-space switches (system, device, assembly technique) must be solved before creating practical systems. In particular, the assembly technique is a key issue of the free-space switches.