Optical waveguides – With optical coupler – Switch
Reexamination Certificate
1999-06-28
2001-02-27
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S015000, C359S281000, C359S490020
Reexamination Certificate
active
06195479
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to optical fiber networks, and, in particular, to switches for directing optical signals along fibers of an optical network, or to attenuators for controlling the strength of optical signals in an optical fiber.
In optical fiber networks, switches are often used to direct optical signals along one optical fiber or another. Many, if not most, of these switches are electromechanical devices which have parts moving in response to electrical signals. While miniaturization has desirably reduced the switching speeds of such devices, switch parts are still being accelerated and decelerated with the consequent wear and breakdown. Furthermore, the physical movement of parts places an effective limitation on further improvement on switching speeds. Hence it is desirable that fiberoptic devices, including switches, be purely optical, or electro-optical, devices. Such devices ideally do not have moving parts.
The present invention provides for a switch which is electro-optical. By applying preselected electrical voltages to the switch corresponding to an On state and an Off state, the switch transmits optical signals between two optical fibers or blocks the signals. Furthermore, by applying electrical voltages intermediate the preselected voltages, the switch operates as an electro-optical attenuator. Attenuators are often used in fiberoptic networks to balance the strength of optical signals along different paths. By controlling the voltage to the device of the present invention, the strength of the signals between two optical fibers is modulated.
SUMMARY OF THE INVENTION
The present invention provides for a fiberoptic reflective variable attenuator and on-off switch comprising a sleeve having a longitudinal channel, a pair of optical fibers fixed in the longitudinal channel, a first, second and third birefringent crystals, a collimating GRIN lens, a liquid crystal cell and a mirror element. The first birefringent crystal is fixed over an end facet of one of the optical fiber pair, and the second and third birefringent crystals are fixed over an end facet of the other of the optical fiber pair. The GRIN lens has a first end face proximate the first, second and third birefringent crystals and the liquid crystal cell is located between the mirror element and a second end face of the GRIN lens. Responsive to preselected voltages applied to its electrical terminals, the liquid crystal cell is in a first state or a second state. The end facets of the pair of optical fibers, the first, second and third birefringent crystals, the GRIN lens, the liquid crystal cell, and the mirror element are arranged and oriented with respect to each other so that light from one optical fiber passes through, and back from, the first, second and third birefringent crystals, the GRIN lens, the liquid crystal cell and the mirror element into the other optical fiber when the liquid crystal cell is in the first state, and light from one optical fiber passes through, and back from, the first, second and third birefringent crystals, the GRIN lens, the liquid crystal cell and the mirror element, but not into the other second optical fiber when the liquid crystal cell is in the second state.
The present invention also provides for multiple fiberoptic reflective variable attenuator and on-off switch devices. Additional pairs of optical fibers may be inserted into the sleeve channel. The end facets of the additional pairs of optical fibers, the first, second and third birefringent crystals, the GRIN lens, the liquid crystal cell, and the mirror element arranged and oriented with respect to each other so that light from a first optical fiber of one of the additional pairs passes through, and back from, the first, second and third birefringent crystals, the GRIN lens, the liquid crystal cell and the mirror element into a second optical fiber of the one pair when the liquid crystal cell is in the first state, but light from the first optical fiber of the one pair passes through, and back from, the first, second and third birefringent crystals, the GRIN lens, the liquid crystal cell and the mirror element, but not into the second optical fiber of the pair when the liquid crystal cell is in the second state.
The first and second states of the liquid crystal cell represent the extreme On and Off states so that the operation of the described device is that of a switch. If voltages intermediate to those corresponding to the On and Off states are applied to the liquid crystal cell, the amount of light passing between the first and second optical fiber cores are proportionally controlled. The device operates as an attenuator.
REFERENCES:
patent: 5276747 (1994-01-01), Pan
patent: 5499132 (1996-03-01), Tojo et al.
patent: 5546219 (1996-08-01), Iida
patent: 5557692 (1996-09-01), Pan et al.
patent: 5689359 (1997-11-01), Kurata et al.
patent: 6055104 (2000-04-01), Cheng
Bovernick Rodney
E-Tek Dynamics, Inc.
Kim Ellen
Townsend and Townsend / and Crew LLP
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