Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-08-15
2003-04-08
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06546162
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to optical switches and more particularly, to an optical switch having two states, a state with two cross-connections and a state with only a single bar connection.
BACKGROUND OF THE INVENTION
Heretofore, it has been well known to provide 2×2 optical switches having two ports on each side, wherein the switch is configurable to make a connection between ports
1
and
2
and simultaneously to provide a connection between ports
3
and
4
. Alternatively, such switches are configurable to provide simultaneous connections between ports
1
and
4
, and ports
3
and
2
. Hence these prior art switches have two states; a first state wherein two bar connections are formed and a second state wherein 2 cross connections are formed. It is desirable to provide an optical switch that is rugged, substantially insensitive to temperature changes within an operating range of temperature, and relatively inexpensive to manufacture. Such switches are required to be capable of switching a beam of light propagating in a waveguide, for example an optical fibre from a first similar waveguide, to a second. The core diameter of a single mode optical fibre is approximately 10 &mgr;m. Providing suitable coupling in both switching states, and providing a switch that is fast enough, and tolerant of physical disturbances is a daunting task most switch manufacturers face.
A well known optical switch made by JDS Fitel Inc. that has been sold in the United States since Feb. 11, 1992 under the product number SR22xx-ONC, includes a pair of GRIN lenses
10
a
and
10
b
having a reflector or mirror
14
that can be selectively disposed therebetween as shown in
FIGS. 1
a
and
1
b
. The latter figure depicts the switch in a reflecting state with the mirror positioned between the lenses
10
a
and
10
b
. Each GRIN lens has two ports offset from the optical axis (OA) of the lens. In operation, in a first state, light launched into port
1
of lens
10
a
couples with port
2
port on the other GRIN lens
10
b
, the ports being on opposite sides of a common optical axis (OA) shared by the GRIN lenses. Similarly, in the first state an optical connection is made between the other two ports
3
and
4
on lenses
10
a
and
10
b
respectively. In a second state shown in
FIG. 1
b
, with the mirror
14
positioned between the lenses, the optical connections between ports
1
and
2
, and,
3
and
4
are broken, and new optical connections is made between each pair of ports on each respective lens. Hence two connections are made, a first between ports
1
and
3
, and a second connection between ports
2
and
4
.
Although this switch performs its intended function, other switches have been developed by JDS Fitel Inc. that are easier to manufacture being much less sensitive to angular and/or lateral deviation of the movable optical element disposed between the GRIN lenses. For example, from a manufacturing standpoint, it is preferable to use a transmissive optical element, in which zero or an even number of internal reflections in each plane, and/or any number of refractions, are imposed on the incident light between the lenses rather than a reflective element imposing one reflection, to route, shift, or direct a beam from one port to an alternate port when the element is disposed between lenses. Thus, by providing a transmissive element such as a prism, the switch is much less sensitive to angular deviation and misalignment of the element than a switch using a reflective element such as a mirror. For example, in comparing angular sensitivity based on a 0.05 dB excess insertion loss criterion, an existing single mirror-based switch has a typical angular tolerance of 0.007 degrees; an existing prism-based switch (as in
FIG. 2
a
) has an angular tolerance of 0.03 degrees, whereas the transmissive optical wedge-based switch described in accordance with this invention has a angular tolerance of 1.4 degrees.
FIGS. 2
a
and
2
b
illustrate a 4-port 2×2 optical switch having 4 GRIN lenses wherein the ports are disposed along the optical axes of the lenses. In
FIG. 2
a
light launched into port
1
of GRIN lens
20
a
traverses the gap between the lenses and couples into lens
20
b
and exits port
2
. Similarly light launched into port
3
couples to port
4
in this bar-state.
With the switch selected to be in a cross-state shown in
FIG. 2
b
, a movable prism is positioned into the gap between the four GRIN lenses. Alternatively, the prism can be rotatable such that in a bar-state it is rotated so that its sides are parallel to the end faces of the GRIN lenses
20
a
,
20
b
,
20
c
, and
20
d
wherein no deflection occurs, and in a cross-state the prism
25
is rotated into the position shown in
FIG. 2
b
. Manufacturing a four port 2×2 switch such as the one shown in
FIG. 2
b
is difficult because in a cross-state not only does port
1
have to align with port
3
, but simultaneously, port
2
must align with port
4
. In the instance that opposing sides of the prism are not parallel, within certain acceptable tolerances, aligning one set of ports for example, ports
1
and
4
via deflection is possible and in fact without difficulty, however simultaneously aligning the other set of ports for example ports
2
and
3
may not be possible since the orientation and location of the four GRIN lenses is fixed.
Such manufacturing difficulties are obviated by this invention since alignment of the second set of ports is not required while the transmission element is disposed between the lenses.
Configurable add drop optical circuits require one or more switches or elements providing the functionality of switching in the event that a signal is to be added or dropped to another optical signal path. The configurable add drop circuit shown in
FIG. 3
a
allows a n-channels multiplexed signal to pass from point A to point B while providing the capability to drop one or more of the n-channels and simultaneously add a new same channel. For example a composite signal having wavelengths &lgr;a to &lgr;n is launched into the multiplexor
30
and is passed on to point B via the multiplexor
30
b
. If there is a requirement to drop the launched signal having a centre wavelength &lgr;a and &lgr;c and add in new signals having a centre wavelength &lgr;a and &lgr;c the switches
31
a
and
31
c
will selected to be in a cross-switching state such that ports
1
and
2
are coupled, and ports
3
and
4
are coupled. Otherwise, if neither adding nor dropping is desired, the switch will be in a bar-state. However one problem that results, is that if the switch is the type shown in
FIGS. 1
a
and
1
b
, or
2
a
and
2
b
, is that add and drop ports become coupled to one another. This can have deleterious effects and is not always a desired goal. It is often preferred to isolate the add and drop ports from one another, preventing a connection between ports
3
and
2
, when ports
1
and
4
are connected. Notwithstanding, a 2×2 switch bar state and in a cross state does not offer this type of isolation in either of its states.
The switch in accordance with this invention provides an elegant solution to this problem. Furthermore, the switch in accordance with this invention obviates the difficult requirement of ensuring that two pairs of ports are simultaneously coupled in a bar-state and in a cross-state.
It is an object of this invention to provide a relatively inexpensive and easy to manufacture switch that will serve as a 1½×2 optical switch.
It is a further object of this invention to provide an add drop circuit that does not optically couple the add and drop port with one another when that node of the switch is in a pass-through mode and not adding or dropping signals.
It is yet a further object of the invention to provide a tolerant, low loss, and reliable 1½×2 switch which allows a first and second port to be connected in a first state, without allowing a third and fourth port to be connected in the same state, and which all
Cohen Adam D.
Copner Nigel
Farries Mark
Iyer Rajiv
JDS Fitel Inc.
Teitelbaum Neil
Ullah Akm E.
LandOfFree
1½×2 optical switch with a transmissive... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with 1½×2 optical switch with a transmissive..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and 1½×2 optical switch with a transmissive... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3088270