Optical waveguides – With optical coupler – Particular coupling function
Reexamination Certificate
1998-12-29
2001-02-27
Font, Frank G. (Department: 2872)
Optical waveguides
With optical coupler
Particular coupling function
Reexamination Certificate
active
06195482
ABSTRACT:
FIELD OF THE INVETION
The present invention relates generally to the field of optical interconnection and communications and in particular to an improved waveguide grating router.
BACKGROUND OF THE INVETION
Optical switching, multiplexing, and demultiplexing has been accomplished in the past by using an interconnection apparatus having a number of closely spaced input waveguides communicating with the input of a star coupler. The output of the star coupler communicates with an optical grating having a series of optical waveguides, each of these waveguides differing in length with respect to its nearest neighbor by a predetermined fixed amount. The grating is further connected to the input of a second star coupler, the outputs of which form the outputs of the switching, multiplexing, and demultiplexing apparatus.
An example of such an interconnection apparatus is disclosed in U.S. Pat. Nos. 5,002,350 and 5,136,671. The geometry of such an apparatus may be such that a number of separate and distinct wavelengths each launched into a separate and distinct input port of the apparatus will all combine and appear on a predetermined one of the output ports. In this manner, the apparatus performs a multiplexing flnction and may advantageously also perform a demultiplexing function. In this demultiplexing situation, a plurality of input wavelengths is directed to a predetermined one of the input ports of the apparatus. Each of the input wavelengths is separated from the others and directed to a predetermined one of the output ports of the apparatus. Advantageously, an appropriate selection of input wavelength permits switching between any selected input port to any selected output port. Accordingly, these devices are referred to as frequency routing devices and alternative approaches to their design is desired.
SUMMARY OF THE INVENTION
I have developed a waveguide grating router incorporating a mode converter that exhibits an improved passband flatness, lower loss and crosstalk and an increased tolerance to fabrication error. The waveguide grating router includes a first optical coupler having at least one input port, at least one mode converter, and P output ports, where P>2. A second optical coupler is also provided that has P input ports, least one output port, and at least one mode converter. P optical paths couple the input port of the first optical coupler to the output port of the second optical coupler.
The waveguide grating router uses suitable input and output transformers to control the magnitudes of the various transmission coefficients contributed by the arms of the router. The phases of the arms, and their lengths are appropriately chosen so that some of the contributions are opposite to remaining contributions, resulting in specified passband behaviour.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawing.
REFERENCES:
patent: 5002350 (1991-03-01), Dragone
patent: 5136671 (1992-08-01), Dragone
C. Dragone, “Efficient Techniques for Widening the Passband of a Wavelength Router,”Journal of Lightwave Technology,16. No. 10, pp.1895-1906 (1998).
C. Dragone et al., “Waveguide grating router with maximally flat passband produced by spatial filtering,”Electronics Letters,33, No. 15, pp. 1312-1314 (1997).
C. Dragone, “An N×N Optical Multiplexer Using a Planar Arrangement of Two Star Couplers,”IEEE Photonics Technology Letters,3, No. 9, pp. 812-814 (1991).
Brosemer J. J.
Font Frank G.
Lucent Technologies - Inc.
Nguyen Tu T.
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