US5325224A
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US
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Time-multiplexed, optically-addressed, gigabit optical crossbar switch
Assignee: California Institute of Technology
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Filing: 1993-03-09
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Granted: 1994-06-28
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Expires: 2013-03-09
Abstract
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 N 2 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.
Inventors
- 👤 Robert J. Lang
- 👤 Li-Jen Cheng
- 👤 Joseph Maserjian
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 05:01
CPC Classifications
H; H04; H04Q; H04Q11/00; H04Q11/0001
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
279 words
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.
Claim 2
Dependent Claim
279 words
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.
Claim 3
Dependent Claim
25 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 1 wherein said spatial light modulator exhibits a contrast ratio that varies with N 2 .
Claim 4
Dependent Claim
30 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 2 wherein said spatial light modulator exhibits a contrast of at least about 60:1 for an array of 8×8 pixel elements.
Claim 5
Dependent Claim
23 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 1 wherein said first wavelength is at a longer wavelength than said second wavelength.
Claim 6
Dependent Claim
44 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 4 wherein said spatial light modulator includes a multiple quantum well structure comprising alternating layers of two different materials and wherein first and second wavelengths are related to the bandgaps of said two different materials.
Claim 7
Dependent Claim
38 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 5 wherein said one of said materials comprising said multiple quantum well structure comprises GaAs and wherein the other of said materials comprising said quantum well structure comprises (In,Ga)As.
Claim 8
Dependent Claim
31 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 6 wherein said first wavelength is at about 1015 nm and wherein said second wavelength ranges from about 900 to 950 nm.
Claim 9
Dependent Claim
21 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 1 wherein said one-dimensional source array comprises an array of diode lasers.
Claim 10
Dependent Claim
22 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 1 wherein said one-dimensional source array comprises an array of light emitting diodes.
Claim 11
Dependent Claim
21 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 1 wherein said means for scanning each laser comprises a diffraction grating.
Claim 12
Dependent Claim
30 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 1 wherein said means for scanning said one-dimensional output over one axis of said spatial light modulator comprises a cylindrical lens.
Claim 13
Dependent Claim
37 words
The time-multiplexed, optically-addressed, gigabit optical crossbar switch of claim 1 wherein said means for refocusing said optical output directed onto said spatial light modulator and reflected therefrom onto said one dimensional output array comprises a cylindrical lens.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1997-06-27 | 1997-12-27 | 1998-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-06-27 | 2001-12-27 | 2002-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-06-27 | 2005-12-27 | 2006-06-28 | $7700.00 | Window Closed / Lapsed |