Time-multiplexed, optically-addressed, gigabit optical crossbar switch
First Claim
1. A time-multiplexed, optically-addressed, gigabit optical crossbar switch comprising:
- (a) a two-dimensional, optically-addressable, reflective, pixellated spatial light modulator comprising NxN pixel elements, where N is an integer, said spatial light modulator normally non-reflective in the absence of an input signal;
(b) a one-dimensional read source array comprising N sources, adapted to receive electrical signal input and provide a one-dimensional optical input corresponding thereto, said one-dimensional read source array operating at a first wavelength and defining a first axis;
(c) means for scanning said one-dimensional optical input over an axis of said spatial light modulator orthogonal to that of said one-dimensional source array;
(d) a one-dimensional output array of detectors, adapted to receive one-dimensional optical output from said spatial light modulator and provide an output electrical signal corresponding thereto, said one-dimensional output array operating at said first wavelength;
(e) means for refocusing optical output reflected from said spatial light modulator onto said one-dimensional output array;
(f) a one-dimensional array of tunable write lasers, said array of tunable write lasers operating within a range of second wavelengths, each laser operating at a separate wavelength and imaged onto said spatial light modulator, said one-dimensional array orthogonal to said first axis defined by said one-dimensional read source array, said range of second wavelengths capable of making portions of said spatial light modulator reflective; and
(g) means for scanning each laser in said one-dimensional array of tunable write lasers across said spatial light modulator and orthogonal to said one-dimensional source array so as to make portions of said spatial light modulator reflective and thereby establish a connection between a particular optical input from said source array and a particular optical output to said detector array.
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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×N crossbar, rather than the N2 lines needed in the prior art. This reduction in addressing lines makes possible the development of enormous crossbar switches, such as 100×100, 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.
27 Citations
12 Claims
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1. A time-multiplexed, optically-addressed, gigabit optical crossbar switch comprising:
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(a) a two-dimensional, optically-addressable, reflective, pixellated spatial light modulator comprising NxN pixel elements, where N is an integer, said spatial light modulator normally non-reflective in the absence of an input signal; (b) a one-dimensional read source array comprising N sources, adapted to receive electrical signal input and provide a one-dimensional optical input corresponding thereto, said one-dimensional read source array operating at a first wavelength and defining a first axis; (c) means for scanning said one-dimensional optical input over an axis of said spatial light modulator orthogonal to that of said one-dimensional source array; (d) a one-dimensional output array of detectors, adapted to receive one-dimensional optical output from said spatial light modulator and provide an output electrical signal corresponding thereto, said one-dimensional output array operating at said first wavelength; (e) means for refocusing optical output reflected from said spatial light modulator onto said one-dimensional output array; (f) a one-dimensional array of tunable write lasers, said array of tunable write lasers operating within a range of second wavelengths, each laser operating at a separate wavelength and imaged onto said spatial light modulator, said one-dimensional array orthogonal to said first axis defined by said one-dimensional read source array, said range of second wavelengths capable of making portions of said spatial light modulator reflective; and (g) means for scanning each laser in said one-dimensional array of tunable write lasers across said spatial light modulator and orthogonal to said one-dimensional source array so as to make portions of said spatial light modulator reflective and thereby establish a connection between a particular optical input from said source array and a particular optical output to said detector array. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification