Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
2001-02-01
2004-05-25
Glick, Edward J. (Department: 2882)
Optical waveguides
With optical coupler
Particular coupling structure
C385S041000
Reexamination Certificate
active
06741775
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical switch utilizing thermooptic effects. This invention is based on a Japanese Patent Application No. 2000-28145, the contents of which are incorporated herein by reference.
2. Background Art
Cross connection technology is a key technology in the next generation optical communication network. It is expected that a variety of optical switches will be utilized in the coming optical communication network.
As an example, optical switches based on thermooptic effects are known, and many operational schemes have been proposed.
FIG. 7A
shows a plan view of such an optical switch, and
FIG. 7B
is a cross sectional view of the switch through a plane A—A in FIG.
7
A.
In the diagram, reference numeral
2
relates to a substrate base upon which a cladding layer
3
is formed, and a Y-shaped core
4
is disposed in an interior of the cladding layer
3
. This type optical waveguide is what is called “a buried channel optical waveguide”.
Silicon substrate etc., for example, may be used for the substrate base
2
. The cladding layer
3
and the Y-shaped core
4
are made of a transparent material.
The Y-shaped core
4
is made of a material having a higher refractive index than the cladding layer
3
so as to act as a optical waveguide. Also, as will be described later, the Y-shaped core
4
is preferably made of a polymeric material (plastic) so that the refractive index can be altered by application of heat.
A polymeric material similar to the Y-shaped core
4
is used preferably as the material for the cladding layer
3
.
The Y-shaped core
4
is formed in such a way that a core having a cross sectional shape of a square-rod is split at a portion along length of the core into two branched cores. The Y-shaped core
4
is comprised by an input-side linear section
4
a
extending from the input side; a branching section
4
b
formed on the output side of the input-side linear section
4
a
, in which the width of the input-side linear section
4
a
increases gradually; a separation section
4
c
formed in a curved or linear shape so that the two branched cores
5
a
,
5
b
separate from each other as they extend from the branching section
4
b
; and an output-side linear section
4
d
in which the branched cores
5
a
,
5
b
extend parallel to each other.
In the branching section
4
b
, the input-side linear section
4
a
extends from the input end of the branching section
4
b
, and the branched cores
5
a
,
5
b
extend from the bottom perimeter opposite to the input end of the branching section
4
b.
An input port
6
a
on the input side of the Y-shaped core
4
and two ports on the output side of the Y-shaped core
4
are placed coplanarly on a plane parallel to the bottom and top surfaces of the substrate base
2
.
On top of the cladding layer
3
, line heaters
7
,
8
comprised by an electrically conductive thin film such as titanium, gold or aluminum etc. are placed so as to extend longitudinally along and on the outside of the Y-shaped core
4
, part way from the input-side linear section
4
a
through the branching section
4
b
to the separation section
4
c
. Heater
7
is disposed on the branched core
5
a
side, and heater
8
is disposed on the branched core
5
b
side.
On both end sections of the heaters
7
,
8
, rectangular-shaped electrode pads
7
a
and electrode pads
8
a
are disposed, respectively, on the outer side of the Y-shaped core
4
, and are connected to respective external electrodes. Electrode pads
7
a
and electrode pads
8
a
are formed as thin films and is made of a material similar to the heaters
7
,
8
.
Also, in the input-side linear section
4
a
, heaters
7
,
8
are disposed away from the optical path with a suitable separation distance while in the branching section
4
b
and the separation section
4
c
, the heaters
7
,
8
are disposed in close proximity to the optical path.
Therefore, if the electrical power is supplied only to heater
7
, the branched core
5
a
side of the branching section
4
b
and the branched core
5
a
in the separation section
4
c
are heated. Rise in temperature causes the effective refractive index to decrease due to thermooptic effects. The result is that light is output from the branched core
5
b
by propagating through the branched core
5
b
side of the branching section
4
b
which is not being heated. In other words, propagation of light through the branched core
5
a
is selectively blocked.
On the other hand, if the electrical power is supplied only on heater
8
, the branched core
5
b
side of the branching section
4
b
and the branched core
5
b
in the separation section
4
c
are heated, so that light is output from the branched core
5
a
by propagating through the branched core
5
a
side of the branching section
4
b
which is not being heated. In other words, propagation of light through the branched core
5
b
is selectively blocked.
The result is that when heater
7
is activated, a light inputted into input port
6
a
is output from port
6
c
through the branched core
5
b
, and when heater
8
is activated, light inputted into port
6
a
is output from output port
6
b
through the branched core
5
a.
Then, by changing the action to heat the branching section
4
b
and the branched cores
5
a
by operating the heater
7
and the action to heat the branching section
4
b
and the branched cores
5
b
by operating the heaters
8
, the optical path can be altered to obtain an optical switch functioning such that a light input into port
6
a
can be output at will from either output port
6
b
or
6
c.
In such an optical switch, in order to guide the light from the branching section
4
b
to either the branched core
5
a
or the branched core
5
b
, it is necessary to adjust the temperature distribution (i.e., refractive index distribution) suitably in the branching section
4
b
by heating either heater
7
or heater
8
.
If the heating temperature is too low, it is not possible to create a sufficient change in the refractive index in the heated section of the branching section
4
b
. The result is that light is transmitted through the heated section so that the light reaches the heated branched core, thereby generating an insertion loss.
Conversely, if the temperature is too high, even the refractive index in the side of the branched core intended for light output of the branching core
4
b
becomes affected so that the light cannot reach the branched core intended for light output, leading to an increase in the insertion loss.
On the other hand, the branched core intended for light-blocking must be heated sufficiently so as to not to permit light to be output from its port.
However, in this type of optical switch, because the branching section
4
b
and the separation section
4
c
are heated as a unit, it is experienced sometimes that if the temperature distribution in the branching section
4
b
is adjusted suitably, the separation section
4
c
cannot be heated sufficiently, and conversely, if the heating condition in the separation section
4
c
is adjusted suitably, appropriate temperature distribution in the branching section
4
b
could not be obtained.
Therefore, adjustment of heating conditions has been troublesome, and it has been difficult to reduce insertion losses.
SUMMARY OF THE INVENTION
The purpose of the present invention is to reduce insertion loss in an optical switch based on thermooptic effects.
Specifically, an object of the invention is to provide an optical switch that enables to adjust the temperature distribution in the branching section of a core and to apply optimal heat to branched cores.
To achieve the object, the present optical switch is comprised by a cladding layer and a core disposed in an interior of the cladding layer for light propagating in such a way that a width of the core is enlarged at a branching section formed at a portion along length of the core to provide plural branched cores to enable to alter a propagation path of inputted light by selective he
Fujita Daigo
Hosoya Hideyuki
Sakuma Ken
Sekiguchi Toshisada
Bell Boyd & Lloyd LLC
Fujikura Ltd.
Kao Chih-Cheng Glen
LandOfFree
Optical switch 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 switch, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical switch will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3269644