Optical switch for reciprocal traffic

Details Optical switch for reciprocal traffic Optical switch for reciprocal traffic

2001-03-06

2002-03-26

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

With optical coupler

Switch

C385S016000, C385S024000, C359S199200, C359S199200

Reexamination Certificate

active

06363182

ABSTRACT:

FIELD OF THE INVENTION
The invention pertains to optical switches. More particularly, the invention pertains to such switches having reduced numbers of switchable transmission path defining elements.
BACKGROUND OF THE INVENTION
Known forms of switched optical communication systems incorporate fiberoptics as a medium for communicating messages carried by modulated beams of radiant energy. Such messages at times need to be switched between optical fibers. One known form of optical switch is a crossbar switch.
Known optomechanical crossbar switches use moving mirrors to create connections between inputs and outputs. Various mechanisms can be used to switch or move the mirrors or otherwise to cause them to be actuated and to be in a state to create a connection.
FIG. 1
illustrates a known optical crossbar switch module
10
having four inputs and four outputs. Such switch modules receive a plurality of modulated light beams to be switched at input ports such as ports
12
-
1
,
12
-
2
,
12
-
3
,
12
-
4
. . .
12
-N. Switched light beams exit module
10
at output ports
14
-
1
,
14
-
2
, . . .
14
-N.
The rectangles inside module
10
represent mirrors. The gray rectangle
16
is a fixed mirror. The dashed rectangles
20
a
-
20
k
are non-actuated mirrors. Non-actuated mirrors permit beams to pass without substantial deflection. The black rectangles
22
a
-
22
d
are actuated mirrors. Actuated mirrors substantially deflect incident beams.
In the example of
FIG. 1
, input ports
12
-
1
,
12
-
2
,
12
-
3
, and
12
-
4
are coupled to output ports
14
-
2
,
14
-
3
,
14
-
4
, and
14
-
1
, respectively. Actuating the appropriate correct set of mirrors enables the switch to make all connection permutations.
Lenses, such as lens
18
a
, at the inputs and outputs of switch module
10
keep the light beams collimated while traversing the free space inside the optical switch. Fibers provide inputs to and transmit outputs from the switch
10
and they are precisely aligned to the collimating lenses. The number of switchable mirrors required in this architecture is N
2
−1.
SUMMARY OF THE INVENTION
A reduced component non-blocking optical switch, or switch module, which supports all traffic that qualifies as reciprocal traffic, includes a plurality of optical ports. Each port has an optical input and optical output associated therewith. The ports couple incident communication beams, such as incident light beams, into a switching region within the switch. Transmission paths established within the switch support reciprocal traffic. Transmission paths can include free space, optical fibers or waveguides.
In one embodiment, a plurality of fixed mirrors or deflectors is positioned substantially diagonally within the switch at optical cross points. The fixed deflectors are located at cross points in the switch where the transmission paths exhibit 90° angles and are oriented at 45° relative to the transmission paths. Other cross points within the switch are occupied by switchable deflectors or mirrors which can be switched to complete respective paths. By combining both fixed and switchable deflector elements, transmission paths can be established between selected pairs of ports thereby supporting the reciprocal traffic.
In another aspect, the ports can be staggered relative to the deflectors so that the path lengths between pairs of ports are substantially constant. In yet another embodiment, some or all of the fixed deflectors can be replaced with combinations of a switchable deflector and a fixed path reversing deflector, such as a V-shaped mirror, to provide loop-back functionality for selected of the ports.
In yet another aspect, deflectors can be implemented as fixed or movable mirrors, or alternately instead of movable mirrors, fixed mirrors with movable mechanical optical deflectors. Solid state deflectors can be used as an alternate.
In one aspect, deflectors can be implemented as optical bubbles using internal reflections or holographic gratings.
Switch modules in accordance herewith can be combined in various configurations to implement multi-stage switches. In one embodiment, non-blocking multi-stage switches can be implemented using, in part, multiple switch modules in accordance herewith to facilitate reciprocal traffic.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.


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