Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-07-07
2001-02-27
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06195187
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of wavelength-division-multiplexed light-signal routing networks.
Dense wavelength-division multiplexing (WDM) is an important aspect of advanced long-distance fiber-optic communications networks, especially telecom and antenna remoting networks. Each of the several network fibers transports eight or more independent high-speed optical-wavelength-encoded signals. Voice/video/data signals are encoded on different, but closely spaced, wavelength “carriers” near 1550 nm or 1300 nm. A key component for signal routing and dynamic reconfiguration of the network is the electro-optical WDM crossconnect, an integrated optical switching component that interfaces with M fibers at its input and M fibers at its output. Prior art exists on such crossconnects; however, the prior-art thermooptic silica versions have large area and millisecond response times, the unamplified III-V semiconductor versions have crosstalk greater than −22 dB, and the fast LiNbO
3
versions require actuation voltages greater than 5 volts. There are unmet needs for smaller-area, lower-crosstalk, planar, nonblocking electrooptic crossconnects having restoration times less than one nanosecond and switching voltages less than 5 volts. Other unmet needs of such systems relate to low cost, low optical insertion loss, and being monolithic with commercial electronics. The crossconnect components in this invention offer most of these desired features in one compact chip.
BRIEF SUMMARY OF PREFERRED EMBODIMENTS OF THE INVENTION
This invention presents novel architectures for integrated-optic M×N×M crossconnect micro-switches. Arrays of active lightwave micro-resonators such as microring resonators on a semiconductor chip provide dense WDM switching in a compact, planar, low-voltage, high-speed geometry. The rings are changed from a low-absorption to high-absorption state by an applied field in III-V or II-VI electroabsorptive material, or the rings transform from a high-absorption state to a low-absorption state by injected current in III-V or II-VI electro-transparency material. Analysis indicates that the crossconnect routing network is scaleable to 8×8×8 with more than 48 dB signal-to-crosstalk ratio.
This invention presents new architectures for low-voltage, low-crosstalk, strictly nonblocking M×N×M crossconnect WDM routing networks intended for monolithic integration on one semiconductor chip. The routing network is based upon arrays of active microring resonators coupled to a novel network of single-mode channel waveguides. This invention exploits a unique feature of the resonant rings— switching induced by changed absorption in the rings, rather than by index changes. The expected restoration time of the active rings is <1 ns. Two novel approaches to switching, electro-absorptive and electro-transparent rings, are described. This crossconnect's architecture has many advantages: it is scaleable, contains no waveguide intersections (crossings), has simple addressing, and packs hundreds or thousands of devices in an area much less than 1 cm
2
because the waveguides have high index contrast. The chip offers convenient end-fire coupling to in-line arrays of optical fibers via tapered waveguides on the chip. Via waveguides, the crossconnect couples simply and monolithically to on-chip laser diodes and photodetectors.
The presently preferred wavelength division routing network features a plurality of cascaded optical matrix switches coupled together in optical series, each matrix including a number of light waveguides and an array of active microring resonators (AMR) two-by-two cross-point light-switching elements associated with cross-points between non-intersecting light waveguide portions, and wherein the AMR light-switching elements of each matrix are responsive to a particular wavelength of light assigned to a particular matrix of the network and unresponsive to wavelengths assigned to other matrices of the network. Switching element control circuitry is provided for causing selected AMR light-switching elements to assume a cross state for switching light across associated cross-points, or a bar state for forwarding light without traversing cross-points. Alternative switching elements include passive lightwave resonators such as microrings or microdisks with associated pairs of active electro-optic index-changing switching members which can selectively apply incoming light signals to selected resonators or alternatively, shunt incoming light signals around the resonators.
REFERENCES:
patent: 5623356 (1997-04-01), Kaminow et al.
patent: 6078605 (2000-06-01), Little et al.
patent: 6078704 (2000-06-01), Bischel et al.
patent: 6130969 (2000-10-01), Villeneuve et al.
Little Brent E.
Soref Richard A.
Auton William G.
Chan Jason
Nathans Robert L.
Nguyen Chau M.
The United States of America as represented by the Secretary of
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