Large-channel-count programmable wavelength add-drop

Details Large-channel-count programmable wavelength add-drop Large-channel-count programmable wavelength add-drop

1999-06-08

2001-07-24

Bovernick, Rodney (Department: 2874)

Optical waveguides

With optical coupler

Switch

C385S024000, C385S037000, C359S199200

Reexamination Certificate

active

06266460

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to data communications methods and apparatus.
BACKGROUND INFORMATION
Wavelength-division multiplexed (WDM) optical networks often require dynamic filters at nodes that can have each channel either pass the node without distortion or be diverted into the node and provide a replacement. Examples of such filters integrated onto a single chip have been described. (See K. Okamoto et al., “16-channel optical add/drop multiplexer consisting of arrayed-waveguide gratings and double-gate switches,” Electron. Lett., vol. 32, pp. 1471-1472, 1996; C. G. M. Vreeburg, et al., “First InP-based reconfigurable integrated add-drop multiplexer,” IEEE Photon. Technol. Lett., vol. 9, pp. 188-190, 1997; L. Eldada et al., “Integrated multichannel OADM's using polymer Bragg grating MZI's,” IEEE Photon. Technol. Lett., vol. 10, pp. 1416-1418, 1998; C. K. Madsen et al., “A multi-port add/drop router using UV-induced gratings in planar waveguides,” Optical Fiber Communications Conference, Paper ThH3, pp. 104-106, 1999; and C. R. Doerr et al., “Arrayed waveguide lens wavelength add-drop in silica,” IEEE Photon. Technol. Lett., vol. 11, pp. 557-559, 1999.)
Such known single-chip add/drop filters suffer from several substantial limitations including waveguide crossings, low channel count and difficulty in matching and controlling component characteristics. Large numbers of waveguide crossings require more chip real estate, leading to larger devices with lower channel counts and complex topologies.
SUMMARY OF THE INVENTION
The present invention provides an integrated drop/add filter for use in WDM networks. Devices in accordance with the present: invention overcome many of the limitations of known single-chip devices.
A first embodiment of a drop/add filter in accordance with the present invention comprises a planar lightwave circuit which includes a demultiplexer which is coupled to an input and demultiplexes a plurality of wavelength channels at the input into a plurality of demultiplexer outputs. Each demultiplexer output corresponds to one of the plurality of wavelength channels. Each of a plurality of waveguides are coupled to a demultiplexer output and a plurality of optical switches are coupled to each of the plurality of waveguides. A plurality of mirrors and output ports, arranged alternately, are coupled to the optical switches. Each optical switch selectively directs a corresponding wavelength channel to a mirror or to an output.
In a further embodiment of a drop/add filter of the present invention, two demultiplexer outputs are provided for each wavelength channel. Optical switches coupled to the demultiplexer outputs selectively direct the two portions of a wavelength channel either to a pair of mirrors or to a coupler. Each coupler is coupled to an add and a drop port. By providing two passbands per channel, this arrangement achieves flat-top passbands without excess loss.
Advantages of the device of the present invention include: flat-top passbands with negligible chromatic dispersion and without excess loss; no performance fading from multipath interference; no waveguide crossings; a compact size; the performance of a dilated switch with only one switch. Additionally, a device in accordance with the present invention has no need to wavelength-align multiple filters, and maintains relative channel polarizations. Furthermore, multiple adjacent “through” channels are used to make up a wider flat-top passband that is suitable for passing future generation traffic such as ≧100 Gb/s data streams.


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patent: 5812709 (1998-09-01), Arai et al.
patent: 5920666 (1999-07-01), Digonnet et al.
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