Large N×N waveguide grating router

Details Large N×N waveguide grating router Large N×N waveguide grating router

2000-04-24

2002-04-30

Schuberg, Darren (Department: 2872)

Optical waveguides

With optical coupler

Plural

C385S037000, C385S039000, C385S046000, C385S130000

Reexamination Certificate

active

06381383

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
Related subject matter is disclosed in the concurrently filed application entitled “MULTIPLE WAVELENGTH LASER HAVING A REDUCED NUMBER OF WAVELENGTH CONTROLS” by the inventors, C. R. Doerr., C. P. Dragone, and A. M. Glass, which is assigned to the same Assignee as the present application.
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a Waveguide Grating Router (WGR) and, more particularly, to a WGR having a large number N of input and output ports.
BACKGROUND OF THE INVENTION
Large N×N waveguide grating routers (WGR) represent an excellent solution for providing large optical cross-connects: They are fully passive elements and they can provide strictly non-blocking connections for a set of N optical channels. [1-5]. (Note in this specification, a reference to another document is designated by a number in brackets to identify its location in a list of references found in the Appendix)
However, due to the intrinsic diffraction characteristics of the grating, restrictions limit the size of a N×N WGR. Additional and even more severe limitations arise if the WGR is designed to cross-connect channels which are equally spaced in frequency [4,6] as opposed to being equally spaced in wavelength.
Because the number of wavelengths being used in an optical system is constantly increasing, there is a continuing need to increase the size of the N×N WGRs used as optical cross-connects.
SUMMARY OF THE INVENTION
In accordance with the present invention, we have recognized that because of the intrinsic diffraction characteristics of the grating, restrictions in the size of N generally happens when N approaches the diffraction order m at which the grating operates. We have developed a technique for maximizing N in a N×N WGR device for channels equally spaced either in frequency or in wavelength.
For the wavelength case, N is increased by appropriate changes in the spacing of the output ports of the WGR and/or by slightly correcting the channels wavelengths.
More particularly, the N in a N×N WGR is maximized for input signals including N equally spaced wavelengths by using an output coupler having N output ports that are shifted from their original uniformly spaced position. In another embodiment used with input signals having N wavelengths or frequencies, the N in a N×N WGR is maximized by using N wavelengths or frequencies that are not equally spaced. In yet another embodiment, used with input signals having N wavelengths or frequencies, the N in a N×N WGR is maximized by using an output coupler having N output ports that are spaced to maximize the weakest signal transmission coefficient of at least one of the N wavelengths or frequencies from any of the N input ports.


REFERENCES:
patent: 6181849 (2001-01-01), Lin et al.
C. Dragone, “A N×N optical multiplexer using a planar arrangement of two star couplers”, IEEE Photon. Technol. Lett. 3, 812-815 (1991).
C. Dragone, C. A. Edwards, and R. C. Kistler, “Integrated optics N×N multiplexer on silicon”, Photon. Technol. Lett. 3, 896-899 (1991).
H. Takahashi, S. Suzuki, K. Katoh, and I. Nishi “Arrayed-waveguide grating for wavelength division multi/demulti-plexer with nanometer resolution”, Electron. Lett. 26, 87-88 (1990).
K. Okamoto, K. Moriwaki, and S. Suzuki, “Fabrication of 64×64 arrayed-waveguide grating multiplexer on silicon”, Electron. Lett. 31, 184-186 (1995).
K. Okamoto, T. Hasegawa, O. Ishida, A. Himeno, and Y. Ohmori, “32×32 arrayed-waveguide grating multiplexer with uniform loss and cyclic frequency characteristics”, Electron. Lett. 33, 1865-1866 (1997).
H. Takahashi, K. Oda, H. Toba, and Y. Inoue, “Transmission characteristics of arrayed waveguide N×N wavelength multiplexer”, J. Lightwave Technol. 13, 447-455 (1995).
M. K. Smit, “New Focusing and dispersive planar component based on an optical phase array”, Electron. Lett. 24, 385-386 (1988).
M. S. Borella, “Simple Scheduling Algorithm for Use with a Waveguide Grating Multiplexer Based Local Optical Networky”, Photonics Net. Comm.., 1, 35-48 (1999).

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