Optical waveguides – Accessories – Attenuator
Reexamination Certificate
2000-03-02
2001-12-18
Lee, John D. (Department: 2874)
Optical waveguides
Accessories
Attenuator
C385S039000, C385S040000, C385S042000
Reexamination Certificate
active
06332055
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical attenuator of multi-channels having a plurality of Mach-Zehnder-type waveguide elements, a plane waveguide type optical circuit, and an optical attenuation system having this optical attenuator.
2. Related Background Art
An optical attenuator using Mach-Zehnder-type waveguide elements is known (see, for example, OFC/IOOC' 93 Technical Digest, TuH4 by M. Kawachi, et al. and Japanese Patent Application Laid-open No. Hei 5-173101). As shown in
FIG. 1
, this optical attenuator has an input optical waveguide
2
, a first directional coupler
3
, a first optical waveguide
4
, a second optical waveguide
5
, a second directional coupler
6
, an output optical waveguide
7
, and an monitoring optical waveguide
8
all of which are provided on a substrate
1
. The optical attenuator has also a heater
9
for regulating the temperature of the first optical waveguide
4
. A light signal inputted into the input optical waveguide
2
is diverged by the first directional coupler
3
to be inputted into the second directional coupler
6
through the first optical waveguide
4
and the second optical waveguide
5
, respectively. The light signal is outputted from the second directional coupler
6
to the optical waveguide
7
and the monitoring optical waveguide
8
at a predetermined diverging ratio. The diverging ratio is controlled by the temperature of the first optical waveguide
4
regulated by the heater
9
. By detecting the light power outputted to the monitoring optical waveguide
8
by a light receiving element and by controlling the temperature of the first optical waveguide
4
, that is, the optical path length, by the heater
9
, the ratio of power P-out of the light signal outputted to the output optical waveguide
7
to the power P-in of the light signal inputted into the input optical waveguide
2
, that is, the light attenuation, can be controlled.
As shown in
FIG. 2
, a plurality of Mach-Zehnder-type waveguide elements are provided in parallel on the common substrate to realize a multi-channel optical attenuator. The multi-channel optical attenuator shown in this figure has eight Mach-Zehnder-type waveguide elements provided in parallel on the common substrate. Each of the Mach-Zehnder-type waveguide elements has an input optical waveguide
2
i,
a first directional coupler
3
i,
a first optical waveguide
4
i,
a second optical waveguide
5
i,
a second directional coupler
6
i,
an output optical waveguide
7
i
and an monitoring optical waveguide
8
i
provided in the same way as shown in
FIG. 1
, and is provided with a heater
9
i
for regulating the temperature of the first optical waveguide
4
i
(i=1 to 8).
In addition, by providing a multi-channel output circuit for outputting multi-channel light signals (for example AWG: Arrayed Waveguide Grating) and an optical attenuator of multi-channels having Mach-Zehnder-type waveguide elements according to each output channel of this multi-channel output circuit on the common substrate, a compact plane waveguide-type optical circuit with small differences between the output powers of the channels can be realized.
SUMMARY OF THE INVENTION
The inventors discovered the following problems as a result of researching the prior art described above. That is to say, in the optical attenuator of multi-channels as shown in FIG.
2
and in a plane waveguide-type optical circuit having this optical attenuator, the output optical waveguide
7
and the monitoring optical waveguide
8
are arranged alternately adjacent to each other. Therefore, it is necessary to provide light receiving elements for detecting the light power outputted to the respective monitoring optical waveguides
8
between the respective output optical waveguides
7
for sending the light signals to the following stages. It is difficult to manufacture such a configuration and it has a limit for miniaturization.
The present invention is provided to solve the above mentioned problems with the purpose of providing an optical attenuator and a plane waveguide-type optical circuit which is easy to manufacture and can be miniaturized.
An optical attenuator according to the present invention has a plurality of Mach-Zehnder-type waveguide elements arranged on a substrate each of which has an input optical waveguide to which a light signal is inputted, a first directional coupler connected to the input optical waveguide, two optical waveguides connected to the first directional coupler, a second directional coupler connected to these two optical waveguides, an output optical waveguide and an monitoring optical waveguide connected to the second directional coupler and a temperature regulator for regulating the temperature of at least one of the above two optical waveguides. The output optical waveguide of each of the plurality of Mach-Zehnder-type waveguide elements is disposed along the first direction on the substrate and an monitoring optical waveguide of each of the Mach-Zehnder-type waveguide elements is disposed along either one of the second or third directions crossing the first direction. By this configuration, it becomes possible to provide the output port of the monitoring optical waveguide of each of the plurality of Mach-Zehnder-type waveguide elements in a different region from the region where the output optical waveguide of each of the Mach-Zehnder-type waveguide elements is provided.
The optical attenuator has multi-channels with a plurality of Mach-Zehnder-type waveguide elements. Each of the channels operates as follows. A light signal inputted into the input optical waveguide is diverged by the first directional coupler to reach the second bi-directional coupler through each of the two optical waveguides. The light signal is outputted with a predetermined divergence ratio to the output optical waveguide and the monitoring optical waveguide from the second directional coupler. The divergence ratio is controlled by the temperature of either one of the above two optical waveguides regulated by the temperature regulator. By detecting the light power outputted to the monitoring optical waveguide by the light receiving element, and by controlling the temperature of the optical waveguide, that is, the optical path length, by the temperature regulator, the ratio (P-out/P-in) of the power P-out of the light signal outputted to the output optical waveguide to the power P-in of the light signal inputted into the input optical waveguide, that is, the light attenuation, can be controlled. In the Mach-Zehnder-type waveguide elements located adjacent to each other, it is preferable for the angle &thgr; between the monitoring optical waveguide of one Mach-Zehnder-type waveguide element and the output optical waveguide of the other Mach-Zehnder-type waveguide element to be 1.1 degrees or more but 2.1 degrees or less.
In this optical attenuator, an monitoring optical waveguide for each channel has an output port in a different region from the region where an output optical waveguide corresponding to each channel is provided. In this way, the light receiving elements for receiving light outputted from the outputted ports of the monitoring optical waveguides corresponding to the respective channels can be integrally arranged. Optical fibers for inputting light signals outputted from the output port from each of the optical waveguides corresponding to the respective channels can also be arranged together at the edge of the substrate. Accordingly, this optical attenuator is easy to manufacture and can be miniaturized.
In an optical attenuator according to the present invention, the monitoring optical waveguides of the plurality of Mach-Zehnder-type waveguide elements are arranged in parallel and spaced at a predetermined distance, and are characterized by trenches crossing them formed on the substrate in which light receiving elements for receiving light outputted from each output port of each monitoring optical waveguide are provided. In this case, the optical attenua
Hatayama Hitoshi
Sasaoka Eisuke
Lee John D.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
LandOfFree
Optical attenuator, plane waveguide type optical circuit... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical attenuator, plane waveguide type optical circuit..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical attenuator, plane waveguide type optical circuit... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2569856