Coherent light generators – Long wavelength
Reexamination Certificate
1999-09-21
2002-03-19
Font, Frank G. (Department: 2877)
Coherent light generators
Long wavelength
C372S020000, C372S102000, C372S032000
Reexamination Certificate
active
06359912
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
Related subject matter is disclosed in the concurrently filed application entitled “A BROADBAND ELECTRONIC N×N CROSS-CONNECT SWITCH USING TUNABLE LASERS by the inventors, C. R. Doerr, C. P. Dragone, I. P. Kaminow and A. M. Glass, both applications being assigned to the same Assignee.
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multiple wavelength laser and, more particularly, to a multiple wavelength laser configuration characterized by N=N
a
N
b
output wavelengths selected using only N
a
+N
b
control signals.
BACKGROUND OF THE INVENTION
Wavelength division multiplexing (WDM) allows high transmission capacity by allowing many wavelengths to be simultaneously transmitted in each fiber. An important device that is needed at each WDM node is a broadband cross-connect switch for providing complete connectivity between incoming and outgoing fibers. Such a cross-connect switch can be realized by combining a waveguide grating router with a set of tunable lasers. A tunable lasers can be simply realized by using an N×1 router as described in the article “Chromatic focal plane displacement in parabolic chirped waveguide grating router” by C. Doerr et al, published in IEEE Photon. Technol. Lerr., vol. 9, pp. 627-635, May 1997. However, in such an arrangement N controls are needed and such laser may be difficult to realize in integrated form for large N. A tunable laser having a reduced number of controls is described in the article entitled “Arrayed-Waveguide grating lasers and their applications to tuning-free wavelength routing” by Y. Tachikawa et al, IEE Proc. -Optoelectron., Vol 143, No. 5, pp. 322-328, October 1996. However, the article does not describe a practical way to integrate a single output tunable laser.
Therefore, there is a continuing need for an integrated single output tunable laser having a reduced number of wavelength selection controls.
SUMMARY OF THE INVENTION
In accordance with the present invention, we disclose an integrated, single output port, tunable multiple wavelength laser having N=N
a
N
b
output wavelengths selected using only N
a
+N
b
control signals. Each of N
b
ports can output N
a
of the laser wavelengths, the port being selected by the N
b
control signals and the particular one of the N
a
wavelengths being selected by the N
a
control signal. An N
b
×1 router combines the signals from the N
b
output ports into a single output.
In another embodiment, the laser apparatus comprises a waveguide grating router including a first and second free-space regions connected by a plurality of waveguide arms having a quadratic path length variation. The input side of the first free-space region includes N
a
input waveguides each separated by a spacing “a” and each including a reflective termination which is controlled by a separate one of a first group of control signals, 1−N
a
. The output side of the second free-space region includes N
b
output waveguides each separated by a spacing “b”, where “a” is equal to N
b
times “b”, each output waveguide including a reflective termination which is controlled by a separate one of a second group of control signals, 1−N
b
, each reflective termination being partially transmitting and connected as a different one of the N
b
output ports of the laser. In yet another embodiment, the laser is connected to a N
b
×1 router that combines the N
b
outputs from the laser into a single output.
REFERENCES:
patent: 5373517 (1994-12-01), Dragone et al.
patent: 5444725 (1995-08-01), Zirngibl
patent: 5913000 (1999-06-01), Doerr et al.
patent: 6023480 (2000-02-01), Dragone
patent: 6023544 (2000-02-01), Dragone
patent: 6243402 (2001-06-01), Doerr
“Arrayed-Waveguide grating lasers and their applications to tuning-free wavelength routing” by Y. Tachikawa et al, IEE Proc.—Optoelectron., vol. 143, No. 5, pp. 322-328, Oct. 1996.
Doerr Christopher Richard
Dragone Corrado Pietro
Glass Alastair Malcolm
Caccuro John A.
Flores Ruiz Delma R.
Font Frank G.
Lucent Technologies - Inc.
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