U.S. patent application number 09/733309 was filed with the patent office on 2001-08-30 for dynamic multichannel fiber optic switch.
Invention is credited to Goodman, Albert, Shahinpoor, Mohsen.
Application Number | 20010017956 09/733309 |
Document ID | / |
Family ID | 27414557 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017956 |
Kind Code |
A1 |
Goodman, Albert ; et
al. |
August 30, 2001 |
Dynamic multichannel fiber optic switch
Abstract
An apparatus and method of optical switching wherein a plurality
of individual activation strips (18) are adhered longitudinally
upon an optical channel, such as an optical fiber (14) to cause the
fiber to undulate in 21/2 dimensions when the activation strips are
activated. The activation strips are activated with a constant or
varying electrical source and are located at the free end of the
optical fiber. Contraction and expansion of respective activation
strips causes a free end of the optical fiber to be displaced or to
undulate. A multichannel switch (100) operates by moving the free
end of the selected input fiber and the free end of the selected
output fiber toward one another so that the signal is sent from the
input to the output fiber.
Inventors: |
Goodman, Albert;
(Albuquerque, NM) ; Shahinpoor, Mohsen;
(Albuquerque, NM) |
Correspondence
Address: |
PEACOCK, MYERS & ADAMS, P.C.
P.O. Box 26927
Albuquerque
NM
87125-6927
US
|
Family ID: |
27414557 |
Appl. No.: |
09/733309 |
Filed: |
December 8, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09733309 |
Dec 8, 2000 |
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09513657 |
Feb 25, 2000 |
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6192171 |
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09733309 |
Dec 8, 2000 |
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09513663 |
Feb 25, 2000 |
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6181844 |
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Current U.S.
Class: |
385/16 ;
385/22 |
Current CPC
Class: |
G02B 6/3502 20130101;
G02B 6/3594 20130101; G02B 6/3582 20130101; G02B 6/3578 20130101;
G02B 6/3572 20130101; G02B 6/3552 20130101; G02B 6/355 20130101;
G02B 6/3568 20130101 |
Class at
Publication: |
385/16 ;
385/22 |
International
Class: |
G02B 006/35 |
Claims
What is claimed is:
1. An optical switch comprising an input comprising at least one
input optical channel; an output comprising at least one output
optical channel; and an activation material adhered longitudinally
on each of said at least one input optical channel to cause said
channel to undulate in 21/2 dimensions and align with the desired
output optical channel when said activation material is
activated.
2. The switch of claim 1 wherein said activation material is
adhered longitudinally on an end of said channel.
3. The switch of claim 1 wherein said activation material is
activated with a source that varies in at least one of amplitude,
frequency, or polarity.
4. The switch of claim 1 wherein said activation material comprises
at least one material selected from the group consisting of
magneto-strictive material, piezoelectric material, piezoceramic
material, piezo-polymeric material, shape-memory alloy material,
and artificial muscle material.
5. A method of switching an optical channel, the method comprising
the steps of adhering an activation material longitudinally on an
optical channel and activating the material to cause the channel to
undulate in 21/2 dimensions and align with a desired output optical
channel.
6. The method of claim 5 wherein the step of activating the
material comprises activating with a source that varies in at least
one of amplitude, frequency, or polarity.
7. The method of claim 5 wherein the step of adhering an activation
material comprises: providing an input optical channel having a
first end and a second end, wherein the activation material is
adhered longitudinally on the first end; providing at least two
output optical channels arrayed within 21/2 dimensions of the first
end of the input optical channel; and wherein the step of
activating the material comprises: activating the material to cause
the first end of the input optical channel to undulate in 21/2
dimensions to align with one of the at least two output optical
channels.
8. The method of claim 5 wherein adhering an activation material
longitudinally on an optical channel comprises adhering at least
one material selected from the group consisting of
magneto-strictive material, piezoelectric material, piezoceramic
material, piezo-polymeric material, shape-memory alloy material,
and artificial muscle material, on an optical channel.
9. An optical switch for directing the signals emitted from input
optical channels into selected output optical channels, said switch
comprising an activation material adhered longitudinally on each of
the input and output optical channels to cause the channels to
undulate in 21/2 dimensions in response to activation signals
received by said activation material.
10. The switch of claim 9 wherein said activation material is
adhered longitudinally on the free ends of the optical
channels.
11. The switch of claim 9 wherein said activation material is
activated with a source that varies in at least one of amplitude,
frequency, or polarity.
12. The switch of claim 9 wherein said activation material
comprises at least one material selected from the group consisting
of magneto-strictive material, piezoelectric material, piezoceramic
material, piezo-polymeric material, shape-memory alloy material,
and artificial muscle material.
13. The switch of claim 9 further comprising collimating lenses
located upon the sending faces of the input channels for focusing
the emitted signal from the input channels into the selected output
channels.
14. The switch of claim 9 further comprising collimating lenses
located upon the sending faces of the input channels and receiving
faces of the output channels for focusing the emitted signal from
the input channels into the selected output channels.
15. The switch of claim 9 further comprising a mirror for
reflecting the emitted signals from the input channels toward the
output channels.
16. The switch of claim 9 wherein said activation material
comprises at least one form selected from the group consisting of a
jacket and a plurality of activation strips.
17. The switch of claim 16 wherein said plurality of activation
strips are arranged symmetrically upon the channels.
18. The switch of claim 16 wherein said plurality of activation
strips comprises at least three activation strips arranged
symmetrically upon the channels.
19. The switch of claim 18 wherein said at least three activation
strips comprise four activation strips, and wherein two of said
four activation strips are oppositely polarized and located
approximately 180 degrees opposite one another, and the remaining
two are oppositely polarized and located approximately 180 degrees
opposite one another and orthogonal to the first two.
20. The switch of claim 9 further comprising at least one support
frame for stabilizing at least one of the group consisting of the
input channels and the output channels, said support frame defining
a plurality of openings for each of the channels to fit through
such that each of the channels has a free end on which said
activation material is located and a fixed portion held fixed by
said frame.
21. The switch of claim 20 wherein said openings within said frame
comprise at least one three-dimensional shape selected from the
group consisting of a cone, a pyramid, a conical segment, and a
pyramidal segment.
22. A method of optical switching for directing the signals emitted
from input optical channels into selected output optical channels,
the method comprising the steps of: adhering an activation material
longitudinally on each of the input and output optical channels;
applying an activation signal to the activation material; and
undulating the channels in 21/2 dimensions in response to the
activation signals received by the activation material.
23. The method of claim 22 wherein adhering an activation material
comprises adhering the activation material longitudinally on the
free ends of the optical channels.
24. The method of claim 22 wherein applying an activation signal
comprises varying the signal in at least one of amplitude,
frequency, or polarity.
25. The method of claim 22 wherein adhering an activation material
comprises adhering at least one material selected from the group
consisting of magneto-strictive material, piezoelectric material,
piezoceramic material, piezo-polymeric material, shape-memory alloy
material, and artificial muscle material.
26. The method of claim 22 further comprising the step of focusing
the emitted signal from the input channels into the selected output
channels with collimating lenses affixed to the sending faces of
the input channels.
27. The method of claim 22 further comprising the step of focusing
the emitted signal from the input channels into the selected output
channels with collimating lenses affixed to the sending faces of
the input channels and the receiving faces of the output
channels.
28. The method of claim 22 further comprising the step of
reflecting the emitted signals from the input channels toward the
output channels with a mirror.
29. The method of claim 22 wherein adhering an activation material
comprises adhering an activation material on each of the channels
in at least one form selected from the group consisting of a jacket
and a plurality of activation strips.
30. The method of claim 29 wherein adhering a plurality of
activation strips comprises arranging the plurality of activation
strips symmetrically on the channels.
31. The method of claim 29 wherein adhering a plurality of
activation strips comprises adhering at least three activation
strips symmetrically on the channels.
32. The method of claim 22 further comprising the steps of:
stabilizing at least one of the group consisting of the input
channels and the output channels with at least one support frame;
defining a plurality of openings with the support frame; and
fitting each of the channels through the openings of the support
frame such that each channel has a free end on which the activation
material is located and a fixed portion held fixed by the
frame.
33. The method of claim 32 wherein defining a plurality of openings
comprises defining openings of at least one three-dimensional shape
selected from the group consisting of a cone, a pyramid, a conical
segment, and a pyramidal segment.
34. An optical switch for directing the signals emitted from input
optical channels into selected output optical channels, said switch
comprising: an activation material adhered longitudinally on the
free ends of each of the input and output optical channels to cause
the channels to undulate in 21/2 dimensions in response to
activation signals received by said activation material causing the
free ends of selected of the input and output channels to move
toward one another; collimating lenses located on at least one of
the emitting and receiving faces of the input and output optical
channels for focusing the emitted signals from the input channels
into the output channels; and a support frame for stabilizing the
input channels and a support frame for stabilizing the output
channels, each of said support frames defining a plurality of
openings for each of the channels to fit through such that each
channel has a free end on which said activation material is located
and a fixed portion held fixed by said frame.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of
both U.S. patent application Ser. No. 09/513,663, entitled "Dynamic
Fiber Optic Switch", to Albert Goodman, filed on Feb. 25, 2000, and
U.S. patent application Ser. No. 09/513,657, entitled "Dynamic
Fiber Optic Switch with Artificial Muscle", to Albert Goodman and
Mohsen Shahinpoor, filed on Feb. 25, 2000, and the specifications
thereof are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention (Technical Field)
[0003] The present invention relates to fiber optic switches,
particularly the use of electro- or magneto-active materials to
cause optical fibers to undulate.
[0004] 2. Background Art
[0005] Present day optical fiber technologies are revolutionizing
the telecommunications industry. Tremendous advances have been made
in the field of telecommunications over the past decade. It has
been estimated that this technology is capable of carrying tens of
millions of conversations simultaneously on a single optical fiber.
Optical fiber communication systems offer many advantages over
systems that use copper wire or radio frequency links as a
transmission medium. They include lower transmission losses, higher
bandwidths, higher transmission rates, lower implementation costs,
greater reliability and greater electrical isolation
characteristics. It is clear that optical fiber communication will
dominate the telecommunications industry in the very near future
because of advantages such as these.
[0006] An important task in any fiber optics telecommunication
system is routing the transmitted data to the proper destination
from among many destinations possible. This task is accomplished by
a variety of fiber optics switches. As the use of fiber optics has
proliferated in telecommunication systems, replacing wire,
different routing fiber optic switches have been developed. They
generally consist of only a few or several fiber optics
channels.
[0007] Fiber optic switching is an important component in any
telecommunication system. These systems use switches to establish
communication channels among two or more of their interfaces. An
optical fiber switch is capable of optically connecting, or
aligning, any one of a first group of optical fibers with any one
of a second group of optical fibers, or vice versa, enabling an
optical signal to propagate through the optical interface junction
from one fiber to the other.
[0008] When two optical fibers are aligned end-to-end, light
entering one fiber (the input or sending fiber) will continue into
and through the second fiber (the output or receiving fiber) while
the two adjacent ends, or faces, are aligned and close together.
Fiber optic switches misalign or disjoin the adjacent ends of the
fibers by moving one or both of the two ends. By moving, for
example, the first fiber's end to a new location, the signal, in
this case light, can be redirected into another, third fiber, by
aligning the first fiber's end with an end of the third fiber.
[0009] Lateral separation of the two adjacent ends will result in
loss of light between the two fibers so that a light absorber is
provided beside the fiber which either moves into place as the
receiving fiber moves away or stays in place as the sending fiber
moves away. Space is provided for this motion. This effectively
switches the signal off. The discontinuity between the fiber ends
may be either perpendicular to the fiber axis or at some angle to
the axis but the gap is minimal when the fibers are aligned. Fibers
may be collected into a bundle, a fiber optic cable, with a
structure set up at the active location to permit the required
motion of a fiber end. A fiber bundle can be separated from a
circular bundle or other shaped cross-section to a linear
arrangement where the fibers are in a straight line at the switch
but reformed into a bundle again at the device exit.
[0010] Optical fiber switches generally utilize fiber positioning
means, alignment signal emitter means and computer control means.
Normally, a fiber positioning means is provided near the end of one
fiber to selectively point the end of that fiber in one fiber group
toward the end of another fiber in the other fiber group to perform
a switched optical transmission. Patents proposing to perform such
switching actions in fiber optic telecommunication systems include:
U.S. Pat. No. 5,024,497, to Jebens, entitled "Shape Memory Alloy
Optical Fiber Switch," which discusses switching activated by a
shape memory alloy wire in a transverse direction. U.S. Pat. No.
4,512,036, entitled "Piezoelectric Apparatus for Positioning
Optical Fibers," U.S. Pat. No. 4,543,663, entitled "Piezoelectric
Apparatus for Positioning Optical Fibers," U.S. Pat. No. 4,651,343,
entitled "Piezoelectric Apparatus for Positioning Optical Fibers,"
and U.S. Pat. No. 5,524,153, entitled "Optical Fiber Switching
System and Method Using Same," all to Laor, use piezoelectric
bimorphs for positioning optical fiber switches. U.S. Pat. No.
4,303,302, to Ramsey, et al., entitled "Piezoelectric Optical
Switch" discusses other forms of piezoelectric bimorphs for optical
fiber switching.
[0011] Patents discussing fiber optic switching include: U.S. Pat.
No. 5,812,711, to Glass, et al., entitled "Magnetostrictively
Tunable Optical Fiber Gratings;" U.S. Pat. No. 5,812,711 to
Malcolm, et al., entitled "Magnetostrictive Tunable Optical-Fiber
Gratings;" U.S. Pat. No. 4,759,597, to Lamonde, entitled
"Mechanical Switch for Optical Fibers;" U.S. Pat. No. 4,415,228, to
Stanley, entitled "Optical Fiber Switch Apparatus;" U.S. Pat. No.
5,004,318, to Ohashi, entitled "Small Optical Fiber Switch;" U.S.
Pat. No. 4,844,577, to Ninnis, et al, entitled "Bimorph Electro
Optic Light Modulator;" U.S. Pat. No. 4,512,627, to Archer, et al.,
entitled "Optical Fiber Switch, Electromagnetic Actuating Apparatus
with Permanent Magnet Latch Control;" U.S. Pat. No. 5,699,463, to
Yang, et al., entitled "Mechanical Fiber Optic Switch;" U.S. Pat.
No. 5,841,912, to Mueller-Fiedler, entitled "Optical Switching
Device;" U.S. Pat. No. 5,647,033, to Laughlin entitled "Apparatus
for Switching Optical Signals and Method of Operation;" U.S. Pat.
No. 4,886,335, to Yanagawa, et al., entitled "Optical Fiber Switch
System;" and U.S. Pat. No. 4,223,978, to Kummer, et al., entitled
"Mechanical Optical Fiber Switching Device." These patents disclose
various methods for fiber optic switching, including mechanical
devices such as rods, motors, and adapters, as well as wave guides
and reflectors. The Ohashi, Ramsey, Ninnis, Stanley, Jebens, Glass,
and Laor patents disclose various methods and apparatuses that use
piezoelectrics, magneto-strictive materials, and shape memory
alloys, for bending the fiber; however, these patents are either
complicated in their configurations or require additional
mechanical means beyond these materials.
[0012] Other issued patents that disclose types of fiber optic
switches include U.S. Pat. No. 5,915,063 to Colbourne, et al.,
entitled "Variable Optical Attenuator" which discloses the use of a
mirror that tilts in response to movement of a piezoelectric
member, or magnetostrictive or eletrostrictive elements. The signal
leaves one of the fibers and reflects off of the mirror which
directs the signal into the other fiber depending on the tilt of
the mirror. U.S. Pat. No. 5,808,472 to Hayes, entitled "Apparatus
and Methods for Positioning Optical Fibers and Other Resilient
Members" discloses positioning the free end of an optical fiber in
the electric field of several electrodes and applying voltage to a
conductive sleeve around the fiber which then responds to the
electric field produced by the electrodes. U.S. Pat. No. 4,580,292
to Laor, entitled "Communications Exchange" discloses the use of a
bender element like the bender element disclosed in the above
identified Laor patents, that is actuated by piezoelectrics. The
free end of the optical fiber is attached to the bender element so
that it can be moved by the bender element.
[0013] U.S. Pat. No. 5,870,518 to Haake, et al., entitled
"Microactuator for Precisely Aligning an Optical Fiber and an
Associated Fabrication Method" positions actuators in a complicated
substrate apparatus for controlling the movement of an optical
fiber. U.S. Pat. No. 5,216,729 to Berger, et al., entitled "Active
Alignment System for Laser to Fiber Coupling" uses piezoelectric
elements to control mirrors which direct a laser beam into an
optical fiber, and piezoelectric transducers made up of vertical
and horizontal elements that move in response to an applied voltage
and thereby move the fiber. U.S. Pat. No. 5,214,727 to Carr, et
al., entitled "Electrostatic Microactuator" discloses a
microactuator for moving an optical fiber into alignment with one
of several optical fibers by means of upper and lower substrates
and a series of electrodes on the substrates which provide upper
and lower torque stators. The fiber is moved by a conductive
armature that responds to energy from the electrodes. U.S. Pat. No.
4,652,081 to Fatatry, entitled "Optical Multi-Fibre Switch"
discloses coating a magnetic material on a fiber that causes the
fiber to move in response to an energized solenoid around the
fiber. U.S. Pat. No. 4,223,978 to Kummer, et al., entitled
"Mechanical Optical Fiber Switching Device" discloses a mechanical
switch for aligning and misaligning optical fibers.
[0014] As fiber optics telecommunication increases in application,
the number of channels required for switching systems will multiply
greatly. A switch that can accommodate dozens or even hundreds of
channels will be valuable and effective. Designs based upon
combinations of numerous small, movable mirrors and lenses to
direct light from individual fixed fibers have been under
development for some years by such organizations as Nortel
Networks, and Lucent Technologies.
[0015] The present invention overcomes deficiencies in the prior
art and simplifies optical switching by largely eliminating the
mechanical structure necessary to move the fibers. The present
invention provides movement of fiber optic channels by directly
adhering an electro- or magneto-active material to the optical
fiber itself, longitudinally to cause the fiber to undulate to the
desired "21/2-D" position. The fiber moves by application of an
electrical signal directly to the electro- or magneto-active
material upon the fiber. The designation "21/2-D" used herein
signifies that the displacement of the fiber may be both laterally
and longitudinally. The present invention, being based on
modifications of the inventions in the parent applications, allows
input and output fibers to undulate in 21/2 dimensions and
accommodates a large number of optical channels without the use of
complicated apparatuses or multiple movable mirrors.
SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)
[0016] The present invention is an optical switch wherein an
activation material is adhered on individual optical channels so
that when an electrical signal is applied to the activation
material, the activation material contracts or expands and moves
the optical channel accordingly. The activation material can
consist of either an magneto-strictive material, a piezoelectric
material, a piezoceramic material, a piezopolymeric material, a
shape-memory alloy material, or an artificial muscle material. The
activation material is adhered longitudinally upon the free end of
the optical channels in the form of activation strips or in the
form of a jacket. Alternatively, three or four piezoelectric
bimorph activation elements may be adhered to individual fibers so
as to cause undulation motion in the various directions required.
The electrical signal that is applied to the activation material
can vary in amplitude, frequency or polarity in order to control
the direction and amount of movement of the optical channel, as
well as the frequency of its movement.
[0017] The activation strips or jacket of activation material is
placed on either or both of the input and output optical channels.
In this manner, either or both the input and the output optical
channels to be aligned can move toward one another so that the
emitted signal from the input optical channel is transmitted into
the receiving face of the selected output optical channel upon
activation of the activation material. Collimating lenses are
provided on either or both of the input and output optical channels
sending and receiving faces to focus the emitted signal into the
selected output channel.
[0018] In the situation where the input and output optical channels
are not arranged in an end-to-end fashion, a fixed mirror is used
to reflect the emitted signal from the input channels toward the
output channels. Additionally, the present invention includes a
support frame for the input channels and a support frame for the
output channels. The support frame defines a plurality of openings
for each individual optical channel to fit through so that the
optical channel is held stable while allowing the free end to
undulate. The support frame is located just behind the activation
material of each optical channel so that the optical channels are
stabilized while still allowing the free ends to undulate. Each
opening in the frame is designed in a shape allowing the individual
optical channels to move freely in the directions necessary to send
and receive the transmitted signal.
[0019] A primary object of the present invention is to provide an
efficient and versatile means for optical switching by undulating
the free ends of both the input and output optical fibers such that
the selected input and output fiber move toward one another and the
signal is directed from the input fiber into the selected output
fiber.
[0020] Another object of the present invention is to undulate an
optical fiber by placing electro-magneto-active material strips
longitudinally along the optical fiber in order to move the optical
fiber in 21/2 dimensions in response to an electrical signal
applied to the strips.
[0021] A primary advantage of the present invention is that the
fibers move in response to the electrical signals applied to the
electro- or magneto-active materials adhered directly to each
fiber, and does not require additional mechanical means to move the
fiber.
[0022] Still another advantage of the present invention is that
each input and output optical fiber can be moved in 21/2 dimensions
thereby increasing the versatility of the optical switch.
[0023] Other potential advantages provided by the present
invention, due to its simplicity and design, are long life,
reliability, low cost, and a variety of applications.
[0024] Other objects, advantages and novel features, and further
scope of applicability of the present invention will be set forth
in part in the detailed description to follow, taken in conjunction
with the accompanying drawings, and in part will become apparent to
those skilled in the art upon examination of the following, or may
be learned by practice of the invention. The objects and advantages
of the invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The accompanying drawings, which are incorporated into and
form a part of the specification, illustrate several embodiments of
the present invention and, together with the description, serve to
explain the principles of the invention. The drawings are only for
the purpose of illustrating a preferred embodiment of the invention
and are not to be construed as limiting the invention. In the
drawings:
[0026] FIG. 1 is a cut-away view of the fiber optic switch of the
present invention showing a single input fiber undulating between
two output fibers in accordance with the present invention;
[0027] FIG. 2 shows four activation strips adhered to an optical
fiber in accordance with the present invention;
[0028] FIG. 3 shows three activation strips adhered to an optical
fiber in accordance with the present invention;
[0029] FIG. 4 shows the fiber optic switch having one-fiber input
and four-fiber output capability in accordance with the present
invention;
[0030] FIG. 5 shows a one fiber input and eight fiber output
capability in accordance with the present invention;
[0031] FIG. 6 shows a two fiber input and a spherical segment
output having a plurality of fiber outputs in accordance with the
present invention;
[0032] FIG. 7 shows a portion of an optical fiber having three
activation strips adhered along the portion of the fiber to be
displaced, as well as the voltage supply to one of the activation
strips;
[0033] FIGS. 8a and 8b show a side view of an optical fiber with
two activation strips, wherein each activation strip is activated
by an electrical signal applied to two electrodes located at
corresponding ends of each strip, the unactivated state being shown
in FIG. 8a and the activated state in FIG. 8b, and FIG. 8c is a
cross-sectional view of the optical fiber with activation
strips;
[0034] FIGS. 9a and 9b show a side view of an optical fiber having
two activation strips, wherein each activation strip is activated
by an electrical signal applied to two electrodes located at
opposite ends of each strip, the unactivated state being shown in
FIG. 9a and the activated state in FIG. 9b, and FIG. 9c is a
cross-sectional view of the optical fiber with activation
strips;
[0035] FIGS. 10a and 10b show a side view of an optical fiber
surrounded by a magneto-strictive material jacket having two
electrodes at one end of the jacket, wherein the jacket is
activated by an electrical signal applied to the electrodes, the
unactivated state being shown in FIG. 10a and the activated state
in FIG. 10b, and FIG. 10c is a cross-sectional view of the optical
fiber with the jacket;
[0036] FIGS. 11a and 11b show a side view of the activation strip
configuration of FIG. 8 further including a collimating lens at the
output face of the fiber;
[0037] FIG. 12 is a side view of input and output optical fibers
undulating in response to an electrical signal applied to the
activation strips upon each such that the two fiber ends move
toward one another and the signal is transmitted from one to the
other;
[0038] FIG. 13 is a side view of the preferred embodiment of the
present invention showing a group of input and a group of output
fibers showing a particular input and a particular output fiber
undulating toward one another by means of activation strips so that
the signal from the input fiber is sent to the output fiber;
collimating lenses are also shown for focusing the light from the
input to the output fiber;
[0039] FIG. 14 is a side view of a group of input and a group of
output fibers arranged approximately perpendicular to each other
and including a mirror, the arrangement demonstrating the use of
the mirror in addition to the collimating lenses and activation
strips for directing input fiber signals to the appropriate output
fiber; and
[0040] FIGS. 15a and 15b are a front and cross sectional view,
respectively, of the support frame used in accordance with the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(BEST MODES FOR CARRYING OUT THE INVENTION)
[0041] The present invention is a novel method and apparatus for
optical fiber switching which is based on adhering as part of the
body of the fiber itself, electro- or magneto-active means in the
form of wires, and/or strips, or a jacket adhered longitudinally to
the fiber itself to quickly undulate the end of a given optical
fiber, from one group of fibers, to align with another optical
fiber, from another group of optical fibers, in a telecommunication
system. It is to be understood that the word undulating, including
other tenses and forms of that word, are herein used to mean
displacement and undulation of the fiber or fibers. The present
invention can either displace a fiber to a new position or cause
the fiber to undulate back and forth between two or more positions
as required in the application of the invention. The present
invention accomplishes undulation in "21/2-D." In other words, the
end of the optical fiber to be moved is moved in both the x-axis
and y-axis directions, as well as somewhat in the z-axis direction
necessarily due to the bending of the fiber. The electro- or
magneto-active means include smart materials such as shape-memory
alloys or polymer strips or wires, piezoelectric (piezoceramics,
piezopolymers, etc.,) strips, magneto-strictive strips, and
electro- or magneto-active polymers such as ionic polymeric
conductive composites (artificial muscles). These and other
electro- or magneto-active means are referred to herein as
"activation strips."
[0042] The activation strip is extended longitudinally along and
adhered to an optical channel, be it an optical fiber, a group of
fibers, or a fiber optic cable, as well as any type of signal
transmitting channel. The activation strip can be attached by
cement, epoxy or glue between the activation strip and the fiber.
Other bonding materials may also be used.
[0043] The present invention either switches an optical signal on
or off, or directs an optical signal from one fiber to another by
moving the respective fibers toward or away from one another. It is
to be understood that while the sending fibers are generally
referred to herein as "input" fibers and those receiving the signal
therefrom are "output" fibers, the signal can of course travel in
the opposite direction so that the output fiber or fibers become
the input fiber or fibers and vice versa. The labels input and
output are merely used for ease of reference.
[0044] The switch provides on-off action by displacing the input
and output fibers by at least a complete fiber diameter. A partial
light intensity change may be accomplished by a controlled
displacement distance. A diagonal slice arrangement between the
ends of the input and output fibers will permit an intensity
variation dependent upon separation of the two faces of the input
and output fibers. Redirecting the optical signal is accomplished
by undulating the end of the input fiber until it is aligned with
the appropriate output fiber or vice versa. Then, by having the
faces of the ends of the input and output fiber to be joined, cut
at diagonals to "fit" each other like two pieces in a puzzle, it
allows the input fiber to "snap" into place against the receiving
end of the output fiber and be more easily held there.
[0045] The displacement of each fiber is accomplished by the
activation strips adhered longitudinally to the fiber near the free
end where displacement or alignment is needed. Attention is now
turned to the figures. The figures present examples of what can be
accomplished in accordance with the present invention.
[0046] FIG. 1 shows fiber optic switch 10 having input fiber 14 and
output fibers 16 and 16'. Channel guide 12 provides space in which
input fiber 14 can undulate. Input fiber 14 undulates in the area
generally referred to as 20 and aligns with either output fiber 16
or 16', therefore transmitting the signal out of end 24 of switch
10 in the appropriate channel. In this figure, two activation
strips 18 and 18' are shown adhered to input fiber 14. The
operation of the activation strips is further described below.
[0047] FIG. 2 shows input fiber 14 having four activation strips
18, 18', 18", and 18'", adhered along the length of input fiber 14
at radial positions 0.degree., 90.degree., 180.degree. and
270.degree. for a fine degree of control. FIG. 3 shows three
activation strips 18, 18' and 18" adhered along input fiber 14 at
0.degree., 120.degree. and 240.degree.. Of course, any number of
activation strips, preferably two or more, can be adhered upon
input fiber 14 longitudinally at any circumferential location in
order to achieve the desired amount of control and fiber movement.
While activation strips are shown adhered to an end of the input
fiber, the invention is not limited to movement of the input fiber
alone, but could of course include moving the output fiber or
fibers as well by the same method as will be described further
below.
[0048] FIGS. 4 and 5 show fiber optic switch 10 with a single input
fiber 14 and a plurality of output fibers to which input fiber 14
can be aligned with and transmit the signal to. FIG. 6 shows an
embodiment wherein a spherical segment of output fibers is within
the reach of input fibers. Output fibers are fixedly held in the
periphery of a hollow sphere 40. Input fibers, such as 14 and 14',
are inserted into the hollow sphere 40 and undulate to the
appropriate output fiber. Activation strips along the input fibers
cause these fibers to move to the desired output fiber location in
order to transmit the signal in the appropriate direction. Sphere
40 may be a sphere segment, such as a hemisphere, or any other
defined portion of a sphere, provided that the output fibers are
arranged spherically about the axis of the input fiber or fibers.
Furthermore, as described above regarding the designations "input"
and "output," in FIG. 6 fibers 14 and 14' can constitute output
fibers while the fibers shown at 24 constitute input fibers and the
signal would then travel in the opposite direction.
[0049] FIG. 7 is a blown-up view showing a portion of the fiber to
be controlled, whether it be input fiber 14 or any other fiber.
Three activation strips are shown adhered along input fiber 14.
While voltage source 30 is shown connecting to activation strip
18", it is to be understood that each activation strip requires its
own voltage supply for activation. Each activation strip is coated
by electrodes to which activation voltages are applied. Electrodes
can be either thin metallic or conductive films such as carbon or
graphite, or a thin wire connection. These are easily attached by
automated manufacturing processes known in the art.
[0050] The type of electrical source needed to operate the
activation strips depends upon the material used for the activation
strips. Piezoelectric materials require a high voltage and low
current because they are largely non-conductive. Shape-memory
alloys require moderate voltage and current to heat them, generally
up to a few tens of volts and up to one or two amps of current. The
preferred design voltage for activation is approximately five volts
with a maximum current of approximately 400 mA. This is a typical
voltage and current compatible with computer voltages for computer
and data acquisition system integration. However, the voltages
required may be lower depending on the dimension of the fibers to
be moved. In general, the smaller the fiber diameter the smaller
the voltage required to activate and move the activation strip.
Typically, to move a one millimeter diameter fiber approximately
two millimetes, approximately two volts of energy is required.
[0051] Each activation strip 18 is comprised of an electro- or
magneto-active material as will now be described. While only two
activation strips are discussed with reference to each embodiment,
this is done for simplicity and it is to be understood that the
invention requires at least two activation strips and most
preferably requires at least three activation strips, such as shown
in FIG. 7, for the desired 21/2-D control. Either the polarity of
the voltage or magnetic field source, or the polarity of the
electro- or magneto-strictive material itself can be altered to
effect expansion and contraction of the material.
[0052] In a first embodiment, a plurality of magneto-strictive
strips, such as Terfenol-D, approximately a few centimeters long,
for example two centimeters, and of a width of a few microns are
adhered in a symmetrical fashion longitudinally to each fiber near
the end to be undulated. These activation strips are powered by an
imposed magnetic field and either expand or contract according to
the polarity of the magnetic field. The magnetic field is normally
produced around a magneto-strictive material by a coil arrangement.
In this embodiment the coil is attached to or embedded in the
activation strip and the coil is powered by a voltage supply
connected to each activation strip in the same way as described
below for other embodiments. By controlling the magnetic field
applied to each individual activation strip, the end of the optical
fiber undulates dynamically and quickly to perform the switching
function. For example, if two magneto-strictive strips are placed
180 degrees opposite each other longitudinally along the
cylindrical mantle of a fiber, then the fiber can be made to move
to either the left or the right by concurrently expanding one
magneto-strictive strip while contracting the other
magneto-strictive strip. The degree of movement to the left or to
the right can be controlled by the amount of contraction or
expansion of each of the magneto-strictive strips which is directly
related to the strength of the magnetic field applied to each
strip. Of course, additional magneto-strictive strips are adhered
along the length of the fiber for a finer degree of control of
movement in 21/2-D. Indeed, an entire sleeve or jacket of the
material can envelop the fiber and is controlled by a plurality of
electrodes upon the jacket. FIGS. 10a and 10b show a side view and
FIG. 10c a cross-sectional view, respectively, of this embodiment.
Jacket 50, which is comprised of a magneto-strictive material
envelopes optical fiber 14. Electrodes 34 and 36 are powered by
voltage supply 30 which is controlled by switch 32. Upon closing
switch 32 and applying voltage to electrodes 34 and 36, a magnetic
field is produced around jacket 50 by one or more coils embedded in
jacket 50 causing jacket 50 to move as shown in FIG. 10b. While
only two electrodes are shown for simplicity in these figures, more
electrodes and associated coils are used for a finer degree of
control of movement. It is to be understood that wherever reference
is made herein to displacement of the optical channels via
activation strips, the activation "jacket" embodiment is also
included as a means of displacing the channels.
[0053] In a second embodiment, a plurality of piezoelectric,
piezoceramic, or piezo-polymeric strips, such as lead zirconate
titanate (PZT) or polyvinylidine difluoride (PVDF), approximately a
few centimeters long, such as two cm, and of a width of a few
microns are adhered in a symmetrical fashion longitudinally to each
fiber near the end to be undulated. Piezoelectric materials are
electrostrictive in the sense that if electrodes are attached to a
strip having width, length and thickness, and a voltage, normally a
high voltage of a few 1000 volts, is applied across the thickness,
then they either contract or expand lengthwise. Piezoelectric
materials expand or contract according to the polarity of their
properties and of the voltage applied to them. FIGS. 8a and 8b show
a side view of the second embodiment of the present invention, and
FIG. 8c shows a cross-sectional view. In this embodiment,
activation strips 18 and 18' are adhered longitudinally along and
upon optical fiber 14 to be undulated. Voltage supplies 30 and 30'
controlled by switches 32 and 32' supply voltage to strips 18 and
18' via positive electrodes 36 and 36' and negative electrodes 34
and 34' attached to each strip. Due to the way that the voltage
supplies are connected, strip 18 is polarized opposite strip 18'.
By closing switches 32 and 32', the voltage is applied to strips 18
and 18'. Accordingly, strip 18 contracts while strip 18' expands,
causing fiber 14 to bend in an upward direction as shown in FIG.
8b.
[0054] In a third embodiment, a plurality of shape-memory alloy
wires or strips, such as Nitinol, approximately a few centimeters
long, such as two centimeters, and of a width of a few microns are
adhered in a symmetrical fashion longitudinally to each fiber near
the end to be undulated. Shape-memory alloys either contract or
expand due to a temperature transition from a solid phase of
Martensite (crystalline structure is face-centered) to a solid
phase of Austenite (crystalline structure is body-centered) due to
direct electric Joule heating of the material. Shape-memory alloys
either contract or expand according to the polarity of a voltage
applied to them. By controlling the amount of voltage applied to
each strip, the end of the optical fiber undulates dynamically and
quickly to perform the switching function. FIGS. 9a and 9b show a
side view and FIG. 9c a cross-sectional view, respectively, of the
third embodiment in its simplest form. Two activation strips 18 and
18' are shown adhered 180 degrees opposite one another along the
cylindrical length of optical fiber 14. Each activation strip 18
and 18' is controlled by voltage supplies 30 and 30', respectively.
Switches 32 and 32' control the voltage supplied to the respective
shape-memory wires. Positive electrodes 36 and 36' are attached to
activation strips 18 and 18', respectively, but at opposite ends.
Negative electrodes 34 and 34' are attached at opposite ends from
positive electrodes 36 and 36' to activation strips 18 and 18'. As
demonstrated in FIG. 9b, by closing switches 32 and 32', voltage is
applied to activation strips 18 and 18' causing strip 18 to
contract and strip 18' to expand. This is due to the fact that the
voltage polarities across the two shape-memory strips are opposite.
Because activation strip 18 contracts and activation strip 18'
expands, and they are both directly adhered to optical fiber 14,
optical fiber 14 bends in an upward direction as shown in FIG. 9b.
Reversing the polarities of the voltages applied to strips 18 and
18' will cause the fiber to bend downward instead.
[0055] In addition to the materials discussed above for activation
purposes, a special material called ionic polymeric metal composite
(IPMC) artificial muscles can be used for the activation means.
This material is disclosed in U.S. Pat. No. 6,109,852, to Mohsen
Shahinpoor and Mehran Mojarrad, entitled "Soft Actuators and
Artificial Muscles," and U.S. patent application Ser. No.
09/258,602, also to Mohsen Shahinpoor and Mehran Mojarrad, entitled
"Ionic Polymer Sensors and Actuators," and the disclosures therein
are herein incorporated by reference. See also M. Shahinpoor, Y.
Bar-Cohen, J. Simpson and J. Smith, "Ionic Polymeric Metal
Composites (IPMC) as Biomimetic Sensors, Actuators and Artificial
Muscles--A Review," J. Smart Materials & Structure, Vol. 7, No.
4, pp. R15-R36, 1998, also incorporated herein by reference. This
material may be advantageous by being more compatible with optical
fiber material and more easily attachable or incorporated into
fiber optic devices. The optical fiber can be entirely built from
these electro- or magneto-active plastic materials which are
essentially transparent before activation. When entirely built from
IPMC artificial muscle, the material is cladded to have internal
reflection and is coated with electrodes to cause the optical
channel to undulate in 21/2 dimensions when the material is
activated via the electrodes.
[0056] In a fourth embodiment, a plurality of ionic polymeric metal
composite, IPMC artificial muscle, activation strips approximately
a few centimeters long, such as two cm, and of a width of a few
microns are adhered in a symmetrical fashion longitudinally to each
fiber near the end to be undulated. Artificial muscles in the form
of strips with electrodes sputtered or plated on their surfaces
across their thickness, naturally bend when subjected to a low
voltage of a few volts, such as 2-5 volts, and amperages of
approximately a few hundred milliamps. By "natural bending," one
side contracts and one side expands, in distinction to
magneto-strictive, piezoelectric, piezoceramic, piezo-polymeric or
shape-memory materials, which expand or contract more or less
uniformly. The underlying theory is that ions within the material
migrate to one side or the other and in doing so carry water with
them causing swelling on one side (expansion) and deswelling on the
other side (contraction). The strips, which either bend inward or
outward, i.e., concave or convex, are powered by a pair of wires to
a voltage supply connected to electrodes on the strips and can
enable the optical fiber to undulate dynamically and quickly to
perform the switching function. Upon applying voltage to the
electrodes on the IPMC artificial muscle activation strips, the
strips themselves bend either inward or outward direction.
Therefore, a plurality of these strips can be adhered to the fiber
for a finer degree of control in 21/2-D in much the same manner as
described above with respect to piezoelectrics and shape-memory
alloys.
[0057] In a fifth embodiment, an appropriately electroded sleeve or
tubular jacket of ionic polymeric conductor composite, IPMC
artificial muscle, approximately a few centimeters long, such as
two cm, and of a thickness of a few microns is adhered on the
cylindrical mantle of each fiber near the free end to be undulated
in the same manner as described and shown with FIG. 10 above.
Although FIG. 10 was used for purposes of illustrating a
magneto-strictive material jacket, the operation of the IPMC
artificial muscle jacket is the same. When voltage 30 is supplied
to electrodes 34 and 36 upon IPMC jacket 50 through switch 32,
jacket 50 as a whole bends in an upward direction as shown in FIG.
10b. FIG. 10 is only for purposes of demonstrating an exemplary
motion of fiber 14. Electrode pairs can be attached at various
locations upon jacket 50 to cause it to bend in other directions as
well.
[0058] In a sixth embodiment, the optical fiber is made entirely
from IPMC muscle and is cladded appropriately to have internal
reflection and coated appropriately with electrodes on the outside
to allow activation for dynamic 21/2-D undulation in any optical
fiber switching action.
[0059] In a seventh embodiment, one or more activation strips may
be attached to a fiber in the form of a bimorph. A bimorph strip
consists of a twin-layer strip that is properly equipped with
electrodes such that when a voltage is applied, one layer contracts
while the other layer expands, thereby causing the bimorph to bend
and concurrently causing the fiber to which it is attached to bend.
The bimorph can comprise a piezoelectric material.
[0060] Of course, any optical channel, be it an optical fiber, a
group of fibers, or a fiber optic cable, can be moved in the same
manners as described above. Also, it is to be understood that the
fiber can be moved using combinations of the various activation
strip materials described above. The activation strips are to be
affixed to the input or output optical channels in accordance with
the application for the switch. While only one direction of motion
is shown in FIGS. 8-10, and a particular arrangement of electrodes
and polarities is shown, it is to be understood that any direction
of movement can be accomplished by varying the locations of the
activation strip or strips, polarities, and number of strips. In
all of the embodiments presented, the electrical source applied to
the activation strips need not be a constant source, but can of
course be a variable source such as a variable voltage waveform
that varies in either frequency, amplitude, or polarity, or any
combination of those three so as to control the undulation
frequency, direction, and amplitude of the optical channel.
[0061] In an alternative embodiment, collimating lenses are affixed
to the input and/or output fibers so that the sending and receiving
fiber faces need not be in extremely close proximity, thereby in
creasing the flexibility of the switch. FIG. 11 shows the
activation strip configuration of FIG. 8 with the addition of
collimating lens 60. Collimating lens 60 is affixed to the output
end of fiber 14 with bonding bridges shown generally at 62 and 62'
to aid in focusing the light signal sent from or received into
fiber 14. Lens 60 is used to concentrate the emission of the light
signal that naturally diverges upon exiting a fiber. Turning to
FIG. 12, input fiber 64' is shown sending the signal to receiving
or output fiber 64. In this configuration both fibers 64 and 64'
are provided with collimating lenses 60 and 60'. Collimating lenses
are not required if the faces of the two fibers are in such close
proximity that the light signal does not have sufficient distance
to diverge significantly and instead remains focused enough to
enter the adjacent fiber. However, in the configuration
demonstrated in FIG. 12 the light beam diverges due to the distance
between the opposing fiber faces and lenses 60 and 60' are used to
focus and capture the light signal sent and received. The proper
choice of lenses causes the light beam to be narrow and cylindrical
so as to be sent and received properly. Collimating lenses are not
required on both the input and output fibers, but can instead be
included on either input fiber 64' or output fiber 64 depending
upon the desired amount and control of the collimation. Lenses 60
and 60' are concave, convex, or whatever shape necessary to provide
the numerical aperture and focal point required to accommodate the
distance between the input and output fiber faces and optimize
transmission of the signal.
[0062] Turning to FIG. 13, the preferred embodiment of the present
invention is shown. FIG. 13 shows a side view of a multichannel
switching system 100 is shown where the faces of a plurality of
input fibers 72 (or fiber bundle) and a plurality of output fibers
74 (or fiber bundle) are in an end-to-end or opposing relationship
and signals are sent from a selected input fiber to a selected
output fiber. In FIG. 13, input fibers 72 and output fibers 74 all
have activation strips 18 adhered to each fiber. Again, while two
activation strips can be seen on each fiber, any number of
activation strips can be adhered to each fiber as necessary for the
degree of control required.
[0063] As an example, input fiber 76 and output fiber 78 are shown
undulating toward one another by means of the activation strips so
that the light signal exiting from fiber 76 is directed into fiber
78. Collimating lenses 60 aid in focusing the light signal due to
the distance between input fibers 72 and output fibers 74. As
discussed above, collimating lenses may not be required at all, or
may not be required on both input and output fibers, but are used
as needed depending upon the distance between input and output
fibers and the collimation required for optimal transmission of the
signal. If data is to be sent in either direction through
multichannel fiber optic switch 100, the collimating lenses are
preferably attached to all of the fiber end faces of all of the
input and output fiber bundles. If the switch transmits in only one
direction, collimating lenses are preferably provided on each of
the faces of the emitting fibers. Output, or receiving fibers have
a conical viewing geometry so that the cone angle of the receiving
fibers need only cover the entire end of the emitting bundle. This
routing switch, therefore, is capable of including many hundreds of
channels in its routing capability without necessarily having to
flex the receiving fibers.
[0064] Input fibers 72 are held by support frame 70 and output
fibers 74 are held by support frame 70' in order to stabilize and
arrange the fibers so that the free ends can move in response to
the electrical signals applied to the activation strips. Attention
is briefly turned to FIG. 15a which shows a front view and FIG. 15b
a cross-sectional view of support frame 70. Frame 70 grasps fibers
72 behind the activation strips at 96 via an array of conical or
pyramidal shaped openings 94 in frame 70 that the fibers fit
through, thus allowing each fiber to flex in the area shown at 98,
up to a maximum angle; this angle being determined by the distance
and spatial relationship between the two bundles of input and
output fibers, the location of the individual fiber in its bundle,
and the viewing pattern boundary of the opposite bundle. Openings
94 are therefore shown as cones and cone segments to allow for the
necessary angle and amount of flexure for each fiber based upon
that fiber's position in the fiber bundle.
[0065] For example, an input or signal-emitting fiber near the
circumferential edge of its bundle (assuming a cylindrical bundle
of fibers) must send a beam of light straight ahead to reach a
fiber at the corresponding location in the output bundle, but to
reach a fiber located at the opposite edge (of a diameter) of the
opposite bundle, the emitting fiber must have a maximum angle of
flexure radially inward. Further, an emitting fiber centrally
located in its bundle, however, must be able to flex bilaterally if
it is to direct the signal to fibers located anywhere in the area
of the opposing bundle's face. The openings 94 in frames 70 and 70'
containing the individual fibers are shaped accordingly, for
example being shaped as conical or pyramidal segments, to
accommodate whatever degree of flexure is required of the
individual fibers of both the input and output fiber bundles.
[0066] FIG. 14 shows an alternative embodiment 110 for the
multichannel switching system of FIG. 13 wherein a plurality of
input fibers 82 are arranged at an angle, in this case
approximately ninety degrees, from a plurality of output fibers 84.
This configuration can occur when due to space or location
constraints it is not possible for the input and output fibers to
be in an opposing relationship to one another. Each fiber has
activation strips 18 adhered to the fiber to undulate the free end
of the fiber, and a collimating lens 60 for focusing the light
signal, as needed (see above discussion regarding lenses). Input
fibers 82 are held by support frame 70 and output fibers 84 are
held by support frame 70' in order to stabilize and arrange the
fibers so that the free ends can move in response to the electrical
signals applied to the activation strips as described above. As
above, the number of activation strips used on the fibers and the
location thereon can vary from one application to the next. Also,
collimating lenses 60 may or may not be required on all fibers as
needed. In this configuration, mirror 80 is provided to aid in
directing the light signals from input fibers 82 to output fibers
84 because the faces of input fibers 82 and output fibers 84 are
not in an opposing relationship. The angle of reflection off of
mirror 80 for each light signal is equal to the angle of incidence
onto mirror 80 as indicated by .alpha. and .beta.. Mirror 80 is
shown as planar, however, it can alternatively be concave or convex
as will be apparent to those skilled in the art, in order to
converge or diverge the reflected light signals as desired.
[0067] As an example of how system 110 operates, fiber 86 is shown
in three different positions so that the light from input fiber 86
is sent to one of three different output fibers 88, 90, and 92
depending upon which of the three positions fiber 86 occupies. In
the horizontal position fiber 86 emits light that is reflected off
of mirror 80 and into output fiber 88 which is not required to
undulate in order to capture the signal from fiber 86. In response
to a signal received by the activation strips located upon fiber
86, fiber 86 undulates to a second position where the emitted
signal reflects off of mirror 80 and into fiber 90 which has also
undulated by means of its activation strips in order to receive the
signal from fiber 86. When fiber 86 moves to a third position by
way of its activation strips, the emitted light reflects off of
mirror 80 and into fiber 92 that has also moved in response to
signals received by its activation strips.
[0068] The present invention may be used in telecommunications for
signal on-off control; signal routing from one destination to
another; signal attenuation; signal combination by having two or
more outgoing bundles from two or more sources to be formed into a
single bundle; and signal splitting to send a signal to more than
one destination. The invention may be located at either the
transmitting or receiving terminals of a communication channel or
any intermediate location. The functioning bandwidth of the
switching time spans a fraction of a Hertz to an upper limit of a
few kilohertz.
[0069] The activation strips for the fibers are preferably computer
controlled. Computer software directs each input or emitting fiber
to select the proper output or receiving fiber of the receiving
bundle. It then positions the emitting fiber, the receiving fiber,
or both, at the proper angle through control of the activation
strips. The data stream of the incoming channel includes both the
message information and the software instructions for each
message.
[0070] The present invention provides fiber optic switching that
controls the routing of many hundreds of data channels in a very
inexpensive, reliable, simple, and dependable way which is readily
amenable to mass production.
[0071] Although the invention has been described in detail with
particular reference to these preferred embodiments, other
embodiments can achieve the same results. Variations and
modifications of the present invention will be obvious to those
skilled in the art and it is intended to cover in the appended
claims all such modifications and equivalents. The entire
disclosures of all references, applications, patents, and
publications cited above are hereby incorporated by reference.
* * * * *