Fiber optics electro-mechanical light switch

An electro-mechanically actuated light switch is provided for transferring ight energy into or out of a fiber optic light transmission path. Liquid material contained within the switch provides a continuity between two fiber optic terminals in the fiber optic light transmission path. The liquid material is chosen to have an index of refraction higher than the material which contains it, so that substantially total internal reflection is sustained along the optical axis of the fiber optic light transmission path. A transparent member is movably mounted in a port in the switch and resiliently supported for extension into the liquid material. An electromagnetic-solenoid arrangement is adapted to extend an angularly disposed reflective end of the transparent member into the liquid material for redirecting light energy which it intercepts. Such redirected light energy in the form of light intercepted in the optical path may be detected by a suitable sensor; alternatively light signals from a suitable source such as a light emitting diode may be introduced into the transparent member and reflected to propagate along the optical path.

BACKGROUND OF THE INVENTION 
Recent development and adaptation of optical techniques for applications to 
communications, data processing, and similar transmission systems has 
numerous advantages as compared with electronic systems which have 
comparable functional objectives. 
Low-loss, high quality, multi-mode fiber optic cable has been developed 
which renders optical communication, data processing, and signal 
transmission systems feasible, practical, and desirable. Some of the 
advantages of fiber optic cables used in such systems include greatly 
reduced size, weight, and cost; electrical isolation which eliminates 
grounding and ground loops; reduced constraints relative to impedance 
matching; and, easy coupling to common logic circuitry by use of available 
light sources and detectors. Moreover, fiber optic cables permit high 
channel isolation, easy interchangeability with electrical cable, and 
greatly reduced electromagnetic interference. 
One of the most important advantages offered by fiber optic cables in 
military use is their characteristic immunity to radio frequency signals 
and the fact that the transmitted light signals are contained wholly 
within the cables. In ground communication systems, this obviously greatly 
increases transmission security. The use of optical cables also eliminates 
cross talk and optical paths provided by such fiber optic cables are 
resistant to electromagnetic interference from other equipment on air 
craft, vessel, or vehicle and even immune to electromagnetic pulses, such 
as may be generated by nuclear explosions. 
In such optical systems, there is a need for optical couplers which are 
connectable to fiber optic cables, for example, to provide the capability 
of intercepting and extracting signal information from an optical path, as 
well as introducing signal information into that optical path. 
Additionally, it is desirable that such a coupler be selectively operable 
to redirect light energy signals into or out of the optical path as 
desired and, in such selective operation, be remotely controllable if 
desired. 
SUMMARY OF THE INVENTION 
The principal functional objective of the present invention has a two-fold 
aspect, the first of which is to couple light out of an optical path, and 
the second of which is to introduce light energy signals into an optical 
path. The light switch of the present invention is electro-mechanically 
operated for transferring light energy relative to a fiber optic light 
transmission path. 
In its preferred embodiment, a body member having a cylindrical bore of 
substantially optical smoothness is configured to receive a fiber optic 
terminal at each end. Typically, the body member may be made of glass or 
other suitable material having ends threaded to receive and secure fiber 
optic terminals. A window fabricated of material substantially transparent 
to the wavelengths of light energy transmitted by the fiber optic light 
transmission path is supported in each end of the body member contiguous 
to each of the fiber optic terminals. 
A selected liquid material substantially fills the cylindrical bore of the 
body member between the windows and has an index of a refraction higher 
than that of the body member for sustaining substantially total internal 
reflection along the optical axis of the cylindrical bore, thus minimizing 
light losses within the light switch assembly. A port in the body member 
is disposed transverse relative to the optical axis of its cylindrical 
bore; a transparent member is movably mounted in the port and resiliently 
supported relative to the body member for extending into the liquid 
material. 
The transparent member has an angularly disposed reflective end which 
redirects light energy when extended into the liquid material. Suitable 
ferromagnetic material is fixed to the transparent member and an 
electrically conductive coil supported on the body member for 
electromagnetic flux linkage with the ferromagnetic element is arranged to 
be selectively connected to a source of electrical energy. Accordingly, 
the transparent member with the angularly disposed reflective end is 
extended into the light transmission path against its resilient support 
upon the actuation of the electrically conductive coil and its associated 
ferromagnetic member which functions in the manner of a solenoid. 
Upon disconnection of the source of electrical energy, the resilient 
support of the transparent member functions to withdraw it from its 
extended position in the liquid material of the light switch assembly. 
Accordingly, the concept and teaching of the present invention 
contemplates a light switch which is selectively operable to perform its 
switching function in response to electrical actuation. In the absence of 
such electrical actuation, the light switching element assumes a 
noninterfering, nonintercepting disposition relative to the light 
transmission path. 
Those knowledgeable and skilled in the pertinent arts will appreciate that 
since the light switch of the present invention is electrically actuated, 
it is readily adapted to remotely controlled operation which may be 
desirable in many functional applications within communications, data 
processing, and similar optical signal transmission systems. 
Accordingly, the primary object of the present invention is to provide an 
improved light switch for transferring light energy relative to to a fiber 
optic light transmission path with minimal light losses of optical energy 
propagating along such light transmission path. 
Another important object of the present invention is to provide such a 
light switch which is selectively operative for transferring light energy 
relative to a fiber optic transmission path. 
A further object of the present invention is to provide such a light switch 
which assumes a nonintercepting, noninterfering condition when it is not 
transferring light energy. 
Yet another important object of the present invention is to provide such a 
light switch which is readily adapted to transfer light energy into or out 
of a fiber optic light transmission path as desired. 
A further object of the present invention is to provide a light switch 
which is electrically actuatable for transferring light energy relative to 
a fiber optic light transmission path so that it may be remotely 
controlled as well as selectively operable to perform its switching 
function. 
These and other features, objects, and advantages of the present invention 
will be better appreciated from an understanding of the operative 
principles of a preferred embodiment as described hereinafter and as 
illustrated in the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a preferred embodiment of the present invention. A body 
member 10 has a cylindrical internal bore 11 which is preferably of 
substantially optical smoothness so as to minimize losses of light energy 
propagated therethrough. The body member 10 may be fabricated of optical 
glass or other suitable materials including certain plastics, for example, 
and is configured with suitable means such as the threaded ends, 12 and 13 
for coupling with a fiber optic terminal at each end. 
Windows 14 and 15 are supported at each end of the body member 10 
contiguous to each fiber optic terminal and are fabricated of material 
substantially transparent to the wavelengths of energy transmitted by the 
fiber optic light transmission path in which the light switch of the 
present invention is employed. 
In a preferred embodiment of the present invention a small amount of 
suitable liquid material may be used to complete the interface between the 
fiber optic terminals and the respectively contiguous windows 14 and 15. A 
selected liquid material substantially fills the entire cylindrical bore 
11 between the windows 14 and 15 to complete the optical path between the 
fiber optic terminals; the liquid material is selected to have an index of 
refraction higher than that of the body member 10 for sustaining 
substantially total internal reflection along the optical axis of the 
cylindrical bore of the body member 10. 
A port 16 in body member 10 is disposed transversally relative to the 
optical axis of its cylindrical bore. A transparent member 17 is movably 
mounted in the port 16 and resiliently supported relative to the body 
member 10 by a suitable means, such as the coil return spring 18. An 
O-ring or other suitable may be employed to seal the transparent member 17 
within the port 16. 
The transparent member 17, which may be fabricated of a suitable glass or 
plastic rod material, has an angularly disposed end 19 which supports a 
reflective coating. In a preferred embodiment of the present invention, 
the reflective end 19 may be disposed at a 45.degree. angle relative to 
the principle axis of the transparent member 17 and the principal axis of 
the fiber optic light transmission path. If desired, the reflective 
coating may be wavelength selective to act only upon wavelengths of light 
energy within a predetermined wavelength region. 
A ferromagnetic element 20 is affixed to the movable transparent member 17 
and is adapted to coact with an electrically conductive coil 21 supported 
on the body member 10 in response to electromagnetic flux linkage 
therewith. A source of electrical energy 22, which may preferably include 
a suitable electrical switch means, is adapted to be selectively 
connectable to energize the electrically conductive coil 21. 
A suitable light energy sensor or light signal source 23 may be affixed at 
or adjacent to the end of the transparent member 17. 
OPERATION 
In its operation, the present invention performs the function of extracting 
light energy from, or introducing additional light energy signals into, a 
fiber optic light transmission path. The fiber optic light transmission 
path is completed by the liquid filled cavity 11 of the body member 10 as 
shown in FIG. 1. 
In an absence of electrical actuation, the selectively operative light 
switch of the present invention is in the position illustrated in FIG. 2 
where the transparent member 17 is withdrawn from the liquid filled cavity 
11 so that the reflective end 19 is not in the fiber optic light 
transmission path. The movable transparent member 17 is retained in this 
position by the resilient return coil spring 18 and when the switch is in 
the condition illustrated in FIG. 2, light energy will neither be 
intercepted for redirection out of the fiber optic light transmission 
path, nor will additional light energy signals be introduced into the 
fiber optic light path transmission path. 
However, upon the actuation of the light switch of the present invention by 
its connection to the electrical source 22 as illustrated in FIG. 1 
through a suitable electrical switch (which may be included in the 
electrical source 22), electromagnetic flux linkage between the 
ferromagnetic element 20 and the electrically conductive coil 21 causes 
downward movement of the transparent member 17, compressing the return 
coil spring 18 and extending the reflective angularly disposed end face 19 
into the fiber optical light transmission path. 
In the actuated condition illustrated in FIG. 1, light energy signals 
traversing the fiber optic light transmission path along the optical axis 
of the cylindrical bore 11 of the body member 10 are in part reflected out 
of the fiber optic light transmission path and along the principal axis of 
the transparent member 17 to be received by element 23 which may comprise 
a suitable light energy sensor developing commensurate electrical signals 
at its terminals 24 and 25. In this manner, the electro-mechanically 
operated light switch of the present invention functions to transfer light 
energy out of a fiber optic light transmission path. 
Alternatively, however, element 23 may include a source of light energy 
signals such as light emitting diode, for example, and upon the 
application of suitable electrical signals to its terminals 24 and 25 will 
generate commensurate light signals which in turn will be transmitted 
along the principal axis of the transparent member 17 to be redirected by 
the reflective face of the angularly disposed end 19 for transmission 
along the fiber optic light transmission path when the light switch is in 
its actuated condition as shown in FIG. 1. 
Accordingly, it will be readily appreciated by those knowledgeable and 
skilled in the pertinent arts that the electro-mechanically operable 
switch of the present invention may be employed either to extract light 
energy signals from a fiber optic light transmission path, or to introduce 
additional light energy signals into such a fiber optic light transmission 
path. 
Moreover, the light switch of the present invention does not intercept the 
fiber optic light transmission path when it is in a nonactuated condition 
and therefore minimizes light losses when it is not operative for the 
purposes of transferring light energy into or out of the fiber optic light 
transmission path. 
Additionally, because the light switch of the present invention is 
electrically actuated, it is readily adaptable to be remotely as well as 
selectively controlled, providing an additional desirable advantage in 
many optical light transmission systems. 
The operation of the present invention can readily be rendered further 
selective by the use of a reflective surface which is responsive only to 
wavelengths of light energy within a desired wavelength region. 
Obviously many modifications and variations of the present invention are 
possible in the light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims the invention may 
be practiced otherwise than as specifically described.