Optical waveguides – With optical coupler – Particular coupling function
Patent
1998-04-06
1999-07-27
Palmer, Phan T. H.
Optical waveguides
With optical coupler
Particular coupling function
385 24, 385 28, 385 22, G02B 626
Patent
active
059304197
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a wavelength demultiplexer that is constructed using integrated optics and, more particularly, such a demultiplexer that comprises a) at least one inlet wave-guide that is fed by a plurality of optical signals in several different wavelength channels; b) a plurality of outlet wave-guides, whereby each one is traversed by one of the aforementioned wavelength channels; c) an assembly of adjacent integrated wave-guides connected from one side to the inlet wave-guides and, from the other side, to the outlet wave-guides through an inlet connector and an outlet connector, respectively, whereby the lengths of the guides of the assembly increase incrementally from guide to guide in a manner such that the assembly constitutes a phase network; d) a mode-expanding wave-guide arranged at the inlet of the inlet connector; and e) a plurality of mode-reducing wave-guides arranged at the outlet of the outlet connector and connected in each case to one of the outlet wave-guides.
Such demultiplexers are known, in particular, from U.S. Pat. No. 5,002,350. In order to minimize optical losses, mention is made in this document of close proximity coupling between the guides of the assembly of integrated wave-guides that form a phase network at the location of the outlet of the inlet connector and of the inlet of the outlet connector. This connection in the way that this is established in U.S. Pat. No. 5,136,671. In addition, an important problem in such a demultiplexer is that of optimizing the width of the band passing into each of the separated channels for an acceptable predetermined cross-talk limit level.
As its objective, the present invention aims precisely to construct an optical wavelength demultiplexer with small losses of luminous energy without recourse to the strong coupling mentioned above in which the width of the band passing through each of the separated channels is optimized in accordance with a low predetermined level of cross-talk.
One achieves these objectives of the invention as well as others that will appear on reading the description, that is going to follow, with an optical wavelength demultiplexer of the type described above that is noteworthy in regard to the feature that the mode-expanding guide is arranged at the inlet of the inlet connector and is connected to the inlet guide and the mode-reducing guides are arranged at the outlet of the outlet connector and are each connected to the outlet wave-guides and are identical in terms of geometry with a width that varies linearly in accordance with their length and the width of the aforementioned expanding and reducing guides at their connection to the associated connector is fixed in order to optimize the width of the band passing through a channel while limiting the cross-talk between the outlet channels to a predetermined level.
In accordance with one preferred form of embodiment of the invention, the arrangement also comprises a mode-reducing wave-guide between the inlet connector and one end of each of the guides of the assembly of wave-guides that form a phase network and a mode-expanding wave-guide between the other end of each of the guides of this assembly and the outlet connector, whereby these expanding and reducing guides are identical in terms of geometry, with a width varying linearly in accordance with their length and whereby they are provided with dimensions for reducing proximity coupling between the guides of the aforementioned assembly at a predetermined low level.
Other characteristics and advantages of the present invention will appear on reading the description, that is going to follow, and on examining the appended drawing in which:
FIG. 1 is an arrangement showing the principal elements of the demultiplexer in accordance with the invention;
FIGS. 2 and 3 are arrangements of the inlet connector and the outlet connector, respectively, that form part of the demultiplexer of FIG. 1;
FIG. 4 brings together three schematic sections of the connector of FIG. 2 taken in accordance with the section lines A,
REFERENCES:
patent: 5680236 (1997-10-01), Van Der Tol
Chervenak William J.
Corning Inc.
Palmer Phan T. H.
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