Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1993-03-09
1994-06-28
Chilcot, Jr., Richard E.
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359117, 385 17, H04J 1408
Patent
active
053252241
ABSTRACT:
A time-multiplexed, optically-addressed, crossbar switch (38) is provided using a two-dimensional, optically-addressed, reflective spatial light modulator (O-SLM) (20). Since the optical addressing is time-multiplexed, only N addressing lines are required for an N.times.N crossbar, rather than the N.sup.2 lines needed in the prior art. This reduction in addressing lines makes possible the development of enormous crossbar switches, such as 100.times.100, for the first time. In addition, since data paths remain entirely in the optics domain, data speeds can reach the multi-gigabit level. In the switch, a row (40) of N inputs (42) at the "read" wavelength is spread over one axis of the O-SLM. The light is refocused along the other axis to an output array (48) of detectors (50), so that each input has the potential to talk to any one output. The O-SLM is normally off, i.e., non-reflective, so that the output is, in the absence of an input signal, zero. A one-dimensional array (52) of lasers (54) at the "write" wavelength is imaged onto the O-SLM. Each laser scans across an entire row of the O-SLM; where the laser is on, it turns on a portion of the O-SLM and establishes a connection between a particular input and a particular output. A full row is scanned in a time much shorter than the response time of the O-SLM, so that state of the O-SLM is capacitively stored and dynamically refreshed. The scanning is accomplished by tuning the wavelength of the laser and passing it through a grating, which sweeps the beam in space.
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A. G. Larsson et al, "Molecular beam epitaxy engineered III-V semi-conductor structures for low-ower optically addressed spatial light modulators", in Optical Engineering, vol. 31 No. 7, pp. 1576-1582 (Jul. 1992).
Cheng Li-Jen
Lang Robert J.
Maserjian Joseph
California Institute of Technology
Chilcot Jr. Richard E.
Negash Kinfe-Michael
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