Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2001-11-27
2004-12-28
Font, Frank G. (Department: 2883)
Optical waveguides
With optical coupler
Switch
C385S016000, C385S059000
Reexamination Certificate
active
06836586
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical switch, and in particular, to an optical switch suitably used in an optical communication apparatus, an optical transmission apparatus, and the like.
2. Description of the Related Art
As for an optical switch for switching an optical path, those for switching a traveling direction of light by electrically changing a refractive index or phase of an optical path, switching a traveling direction of light by mechanically displacing an optical path, and so on have been developed. The mechanical optical switch has been often used in an optical communication apparatus, optical transmission apparatus, or the like because it has a low coupling loss of light, is substantially independent of the wavelength of the propagating light, and have a self-latching property for maintaining, even after removal of electric power, the coupling state of light in a state before the removal.
The mechanical optical switch comprises a movable optical fiber which can be elastically deformed and two fixed optical fibers, an open end of the movable optical fiber facing to open ends of the fixed optical fibers via an optical gap, and switches the optical path by displacing the open end of the movable optical fiber with respect to the open ends of the fixed optical fibers. A silicone based liquid serving as an index matching oil is placed between the open end of the movable optical fiber and those of the fixed optical fibers in order to prevent attenuation and scattering of light from occurring there. For that purpose, the whole mechanism of the optical switch is contained in a housing, and the housing is filled with the silicone based liquid.
The fixed optical fibers are held by a fixed holder (fixed block) at portions close to their open ends. The movable optical fiber is held by a movable holder (movable block) at a portion close to its open end. The movable optical fiber is held by another fixed holder at a point distant from the tip of the movable optical fiber, and the point constitutes a fulcrum.
Since the open ends of the fixed optical fibers and the open end of the movable optical fiber are provided to face to each other, the fixed holder and the movable holder also face to each other. In order to displace the open end of the movable optical fiber with respect to the open ends of the fixed optical fibers, the movable holder is displaced with respect to the fixed holder. In order to keep such a movement within a certain route for avoiding misalignment when displacing the movable holder with respect to the fixed holder, guide pins are provided on one of the holders (for example, fixed holder) to protrude from the facing surface thereof and are inserted into guide channels provided on the facing surface of the other holder (for example, movable holder). Thus, when the movable holder is displaced, the guide pins move along the guide channels, and the movable holder is stopped when the guide pins reach the ends of the guide channels.
An electromagnetic actuator is used to displace the movable holder or movable optical fiber with respect to the end of the fixed optical fiber, which is typically large in size. The movable holder or movable optical fiber is moved in the index matching oil having viscosity, so that a significant magnitude of force is required. For that purpose, a large electromagnetic actuator is required. The housing of the optical switch is intended to contain the large electromagnetic actuator therein, so that it also becomes large in size. In addition, since the optical switch circuit includes a combination of many optical switches, if the individual optical switches are large, the optical switch circuit is also large.
U.S. Pat. No. 6,169,826 (issued on Jan. 2, 2001) has been proposed to reduce the size of an electromagnetic actuator used in an optical switch. The structure thereof will be described below with reference to FIG.
6
.
Referring to
FIG. 6
, in an optical switch
600
, fixed optical fibers
624
and movable optical fibers
622
are positioned so as to have their respective open ends faced to each other in a housing
610
. The open ends of the movable optical fibers are moved relatively to the open ends of the fixed optical fibers to connect and/or disconnect an optical path. The fixed optical fibers are held by a fixed holder
632
made of soft magnetic ceramic at a portion close to the open ends thereof in the housing
610
. The movable optical fibers
622
are supported and fixed in the housing
610
by another fixed holder
636
at a distance from the open ends thereof and are held by a movable holder
634
made of soft magnetic ceramic at a portion close to the open ends thereof. When the movable holder
634
made of soft magnetic ceramic is reciprocated with respect to the fixed holder
632
made of soft magnetic ceramic, the open ends of the movable optical fibers held by the movable holder
634
made of soft magnetic ceramic are reciprocated with respect to the tips of the fixed optical fibers
624
along with the movable holder
634
to connect and/or disconnect the optical path.
An electromagnetic actuator
650
comprises an E-shaped yoke
652
having a back yoke (column yoke)
654
which is located on the side of the fixed optical fibers
624
from the fixed holder
632
made of soft magnetic ceramic in the housing, and first and second end legs
656
and
656
′ of the E-shaped yoke
652
extend from the back yoke
654
to the side surfaces of the movable holder
634
made of soft magnetic ceramic. The first and second end legs
656
and
656
′ have first and second pole pieces
658
and
658
′, respectively, which face the side surfaces of the movable holder
634
made of soft magnetic ceramic. The movable holder
634
made of soft magnetic ceramic can reciprocate between the first and second pole pieces
658
and
658
′. A center leg
662
protruding from the center of the back yoke
654
toward the movable holder
634
made of soft magnetic ceramic is constituted by a permanent magnet
664
and the fixed holder
632
made of soft magnetic ceramic. For example, the permanent magnet
664
may be a sintered neodymium-iron-boron permanent magnet.
The permanent magnet
664
is magnetized in a direction from the fixed holder
632
made of soft magnetic ceramic to the back yoke
654
or in the direction opposite thereto. Part of the magnetic flux exiting from the permanent magnet
664
enters the first end leg
656
through the back yoke
654
. Then, it enters the movable holder
634
made of soft magnetic ceramic via the first pole piece
658
. Then, it passes through the fixed holder
632
made of soft magnetic ceramic to return to the permanent magnet
664
. In this way, the permanent magnet
664
, a first half of the back yoke
654
, the first end leg
656
, the first pole piece
658
, the movable holder
634
, and the fixed holder
632
constitute a first magnetic path. The magnetic flux of the permanent magnet passing through the first magnetic path is denoted by reference symbol A in this drawing.
Part of the magnetic flux exiting from the permanent magnet
664
enters the second end leg
656
′ through the back yoke
654
. Then, it enters the movable holder
634
made of soft magnetic ceramic via the second pole piece
658
′. Then, it passes through the fixed holder
632
made of soft magnetic ceramic to return to the permanent magnet
664
. In this way, the permanent magnet
664
, a second half of the back yoke
654
, the second end leg
656
′, the second pole piece
658
′, the movable holder
634
, and the fixed holder
632
constitute a second magnetic path. The magnetic flux of the permanent magnet passing through the second magnetic path is denoted by reference symbol B in this drawing.
FIG. 6
shows a state in which the movable holder
634
made of soft magnetic ceramic is attracted by the first pole piece
658
, and there is a wider gap between the movable holder and the second pole piece
658
′. The opti
Hitachi Metals Ltd.
Kianni K. Cyrus
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