Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1999-08-05
2001-04-17
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S033000, C385S045000, C385S024000
Reexamination Certificate
active
06219481
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to an optical filter, and more particularly to an optical filter carried by a substrate.
BACKGROUND OF THE INVENTION
Optical filters are nearly ubiquitous elements in the field of optical communications. Optical filters are used for both multiplexing and demultiplexing, routing, attenuating, encoding, and decoding optical signals. Since optical signals are generally carried over long distance by optical fibres, optical filters are coupled in a well-known manner with the optical fibres, such that a filter assembly will be disposed in-line and between at least a pair of optical fibres. However, in some instances, these filters are configured such that they are essentially one-sided devices. For example, two wavelengths may be launched into a one sided device having two optical fibres at a same end; in this instance one wavelength may be extinguished wherein another wavelength will passed from one optical fibre to the other. Alternatively, a single sided optical filter may serve to attenuate light passing therethrough. In order to efficiently couple light from an optical fibre to a filter and back to an optical fibre, a lens is required; otherwise the light exiting an end face of an optical fibre will diverge and much of the light will be lost. It is generally desired to provide a collimated beam to a filter element or more particularly to the filter coating or layers. In view of this, optical filter assemblies usually comprise at least two optical fibres housed within a sleeve and one or more lenses disposed between a filter coating and the optical fibres for collimating light destined for the filter coating and for focusing light directed toward one of the optical fibres.
Optical filters such as dichroic filters are typically comprised of many layers of light transmissive high and low index material arranged to form optical cavities; the layers are extremely thin, and are in the order of the wavelength of light passing therethrough. These layers are coated or deposited on a light transmissive substrate that serves as a carrier or support for the ultra-thin coating.
Over the years, graded-index (GRIN) rod lenses have been widely used in the optics industry. They are convenient to use, and can be modified by polishing and end thereof. For example, if a pitch of a GRIN lens is too long, and requires shortening, the end face of the lens can be polished to shorten its length and effectively lessen its pitch. Due to the convenience and relatively low cost of GRIN lenses, they are most often the element of choice when manufacturing small precision optical devices. In order to couple one or more optical fibres to a GRIN lens, a fibre tube or sleeve is used having a complementary end face to and end face of the GRIN lens to which it is to be coupled. Adhesive such as epoxy is sometimes used to fixedly couple the tube with the lens in a preferred position. Heat cured epoxies are also used and tend to provide a strong immovable bond between the optical fibre sleeve and the GRIN lens. It is a well known practice, to use a similar adhesive such as UV cured adhesive, a heat cured adhesive, or metal or glass solder to fix an optical filter such as a dichroic filter to a GRIN lens or sleeve to an optical filter. However, one concern related to this practice that this invention addresses is the stress induced upon the ultra-thin coating applied to the carrier substrate. When adhesive cures, it tends to shrink and apply untoward forces upon the surface to which it is in contact with. However, for obvious reasons, it has been common practice to apply adhesive between an end face of a rod lens and filter layers to which the lens is to be coupled with.
It is an object of this invention, to lessen or obviate these problems associated with applying adhesive to the outer filter coating of a coated light transmissive substrate.
When light impinges and interacts within a multi-layer multi-cavity dichroic optical filter, the beam is often shifted within the filter layers. If this shift is not taken into account when aligning input and output optical fibres, optimum coupling will not result. One aspect of this invention addresses this problem and provides an elegant solution to optimizing coupling at the same time as obviating the requirement to apply adhesives to the coating layer of a filter.
It is therefore an object of this invention, to provide an optical filter that is less susceptible to stress and that provides suitable coupling between input and output waveguides.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided, an optical device comprising:
a first and a second optical fibre;
an at least partially reflective optical element including a coating disposed on a light transmissive substrate, the at least partially reflective optical element having a substrate side and a coating side;
a lens disposed to receive a beam from one of the fibres to provide a collimated beam at the coating, the substrate side of the at least partially reflective optical element disposed so as to face first and second fibres and the lens, the coating side facing away from the first and second fibres.
In accordance with the invention, there is provided an optical filter comprising: a substrate having a wavelength selective optical filter coating on one side thereof, and being absent a wavelength selective optical filter coating on the other side thereof;
a lens facing the other side of the substrate, absent the wavelength selective coating;
a pair of optical fibres adjacent and parallel to one another disposed to provide light to the optical filter through the lens or to receive light from the optical filter thorough the lens, such that light launched toward the filter through the lens from one of the optical fibres first traverses the other side of the optical substrate absent the coating, and subsequently impinges upon the side of the substrate having the wavelength selective coating.
REFERENCES:
patent: 5859940 (1999-01-01), Takahashi et al.
patent: 5917626 (1999-06-01), Lee
patent: 6014485 (2000-01-01), Pan
patent: 10-48459 (1998-02-01), None
Connelly-Cushwa Michelle R.
JDS Fitel Inc.
Lee John D.
Teitelbaum Neil
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