Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
2000-03-15
2002-07-02
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C359S199200, C385S016000, C385S018000, C385S024000
Reexamination Certificate
active
06415082
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the manipulation of light carried by optical fibers. More particularly, the present invention relates to filtering light and propagating reflected light along optical paths of a planar lightguide circuit.
BACKGROUND OF THE INVENTION
In recent years, the use of optical fibers has become increasingly widespread in a variety of applications. Optical fibers have been found to be especially useful for many industries such as telecommunications, computer-based communications, and other like applications.
To maximize efficiency of optical waveguides, multiple information channels can be multiplexed into a single optical beam. In other words, multiple channels of information can propagate along an optical waveguide as a single beam of light energy. In order to form the multiplexed optical signal or to demultiplex the optical signal, optical filters are typically employed to separate light energy of a first wavelength from light energy having different wavelengths. To maximize optical filter efficiency, light energy can be collimated such that rays of light forming an optical beam travel in a manner parallel with one another. Such a collimation of light energy enables individual rays to strike an optical filter at a desired angle. Without collimating light energy, individual rays of light could strike an optical filter at undesirable angles which reduces optical filter efficiency.
For example, in the conventional art as illustrated in
FIG. 1
, an expanded beam optics system
10
can be used to separate channels of information of a single optical beam
20
that propagates along an optical waveguide
15
. Each channel of the single optical beam
20
can have a different wavelength. For example single beam
20
as illustrated in
FIG. 1
can include separate information channels that are carried by a first optical beam having a wavelength of lambda sub one (&Lgr;
1
) and a second optical beam having a wavelength of lambda sub two (&Lgr;
2
).
The expanded beam optics system
10
can employ a lens
30
to collimate the beams of optical energy forming the single optical beam
20
. The lens
30
is necessary hardware for the conventional system since whenever optical energy leaves one medium and enters into another medium the optical energy refracts or diverges because of the changes in the indices of refraction of the different materials. In addition to the lens
30
, the expanded beam optics system
10
also uses free space
40
between an optical filter
50
and the lens
30
. The free space
40
may be open space or it may include another medium such as a glass block (not shown).
In
FIG. 1
, a few of the optical beams
25
that form the single beam
20
are illustrated in order to demonstrate that the individual optical beams
25
are substantially parallel with one another when exiting the lens
30
. When the individual optical beams
25
strike the optical filter
50
, only optical beams of a predetermined wavelength are permitted to pass through the optical filter
50
. In the example illustrated in
FIG. 1
, the optical filter is designed to pass only optical beams having a wavelength of lambda one (&Lgr;
1
). The individual optical beams
25
having a wavelength of lambda one (&Lgr;
1
) pass through the optical filter
50
and through a glass plate
60
that supports the optical filter
50
. The filtered optical beam
70
exits the glass plate
60
. The light reflected off of optical filter
50
has optical beams that have wavelengths other than lambda one (&Lgr;
1
), such as lambda two (&Lgr;
2
).
One of the drawbacks of the conventional art is that with such a traditional optics systems
10
larger mechanical configurations are required. In other words, the lens
30
is typically large and bulky relative to the size of the optical waveguide
15
. Furthermore, the amount of collimation for light energy with a lens
30
can be directly related to the cross sectional area of the optical beam. Expanded beam optics systems
10
require precision alignment and mounting of the optical devices relative to each other. In other words, the optical waveguide
15
must be in precise alignment with the lens
30
to promote optical efficiency. Similarly, the lens
30
must be in precise optical alignment with the optical filter
50
in order to also promote optical efficiency. Such configurations are not cost efficient for mass production. Additionally, much optical signal loss can occur between the waveguide-lens interface an the lens-free space interface.
Accordingly, a need in the art exists for separating optical energy into separate optical beams of different wavelengths with a higher efficiency. There is a further need in the art for a system for separating optical energy that can optimize the transfer of single mode optical energy propagation between an optical waveguide and a filtering device. An additional need in the art exists for a system that can tolerate a certain amount of misalignment between optical hardware without introducing substantial optical losses. Another need exists in the art for a system separating optical energy that can be easily manufactured and scaleable smaller sizes compared to traditional expanded beam optics that require a substantial amount of hardware. Another need exists in the art for a system for separating optical energy without the use of lenses.
SUMMARY OF THE INVENTION
The present invention solves the problems of expanded beam optics systems by providing an optical network assembly that includes a planar lightguide circuit (PLC) and a filtering device. A PLC can have at least two optical paths for propagating optical energy. The PLC can be designed to channel optical energy to the filtering device in order to separate the optical energy into at least two beams, where a first beam can contain a first information channel and a second beam can contain a second information channel. The filtering device can be attached directly to the PLC or it can be attached directly to an optical waveguide that is also connected to the PLC. This direct attachment can be accomplished by building up the filtering device on the PLC or on the optical waveguide with a thin film deposition process. The optical waveguide can be a flexible optical fiber that is part of a communications network. The optical waveguide can either feed optical energy to or propagate optical energy away from the PLC. Multiple optical waveguides can be attached to a PLC to feed optical energy into and away from the PLC.
Each optical path of a PLC can be made of a transparent core of relatively high refractive index, light-conducting material while the planar material surrounding an optical path can be made of a medium having a lower refractive index. The optical paths can be made of silica, plastic, glass, or low-to-no expansion optical material such as ZERODUR glass. Each of the optical waveguides can be made of materials similar to a PLC. Both the optical waveguides and PLCs can be designed to propagate single modes of optical energy such that the optical energy travels as a single wavefront in order to reduce attenuation and other undesirable effects while increasing bandwidth and transmission properties such as increases in traveled distances.
A PLC or a filtering device (or both) can optimize transfer of single mode optical energy propagation (referred to as modal transfer) between an optical waveguide and the PLC. The PLC and filtering device can be designed to minimize modal disruption (such as changes in E-Field geometry) of optical energy that can occur during the modal transfer of the optical energy between an optical waveguide and the PLC. A PLC can minimize modal disruption that occurs within an interface or junction between the PLC and another light carrying device by facilitating efficient alignment between the PLC and the other light carrying device.
In other words, a PLC's geometry permits rapid and efficient allignment between a PLC and another light carrying device such as an optical waveguide. A PLC in combination with anot
Cirrex Corp.
King & Spalding
Lee John D.
LandOfFree
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