Abstract: An optical device that includes a filter element which affects a beam incident thereon by shifting it is provided with a lens, wherein a distance between the lens end face and the filter is different than the distance between the lens end face and the input waveguide. By ensuring an appropriate difference in distance, optimum coupling is achieved even in view of the beam shift from the filter.

Abstract: The present invention relates to an optical coupling between an end of an optical fiber and an end of a lens, which provides a reliable joint with a determined spacing and angular orientation. The optical coupling permits movement of the end of the optical fiber relative to the lens in at least two alignment directions. Advantageously, the present invention permits movement of the end of the optical fiber relative to the end of the lens in a direction perpendicular to the optical axis of the lens, before the optical coupling is secured. The optical fibre within an optical fiber tube/ferrule and the lens are secured within separate sleeves and the sleeves bonded together. The end of the optical fiber and the end of the lens are optically aligned before being secured in place relative to each other.

Abstract: A sleeve for retaining a plurality of optical fibers in a close or contacting relationship is provided. The sleeve has a bore receiving a number of optical fibers. The internal surface of the bore is such that when that number of optical fibers are contained therein the bore surface defines a perimeter substantially equally spaced about the external surfaces of the optical fibers. Advantageously the sleeve of the present invention may be sealed about the plurality of fibers by vitrification or adhesive to support the fibers or fiber ends without causing unequally distributed stress in the fibers. Signal quality is thus better assured.

Abstract: A multi-stage optical isolating device having at least three stages includes birefringent crystals for separating shifting and combining an incoming beam of light into orthogonal polarized beams. The multi-stage device also includes at least three Faraday rotators that rotate incoming light propagating through the device in a same direction. The inclusion of a reciprocal rotator in the form of a half-wave plate advantageously obviates orienting the Faraday rotators differently.

Abstract: The present invention relates to a coupling element for coupling between optical elements, for instance a ferrule encased fiber end and a lens, two lenses, or filter and lens assemblies, which provides a reliable joint with a determined spacing and angular orientation between them if needed. Advantageously, the coupling in accordance with the present invention does not obscure optical transmission through the coupling with an epoxy layer. A stand off element is provided which has opposite reference surfaces for joining the end faces of the optical elements and a central aperture, slot or equivalent open area for light transmission. In use the open area is aligned, for example with the fiber end and the desired port in the lens. Adhesive connection can be provided between the opposite surfaces of the stand off element and the coupling end faces of the optical elements. No epoxy is applied over the open area. Other securing methods such as external securing elements can be used.

Abstract: A multi-pass optical filter using two identical filters provides narrower band filtering by double filtering an optical signal passing therethrough. Although passing a beam of light at an optical filter having a substantially thick optical thickness is known to have significant coupling losses due to angular misalignment of the output beam and the receiving optical fibre, it has been found that twice filtering in the conventional manner by serially coupling two same filters increases coupling losses. However, this invention provides a coupling arrangement wherein losses are significantly lessened by offsetting the axes of the lensed filters such that the beam exiting the first filter couples into the second filter as it would be reflected backward into the first filter.

Abstract: A polarization beam splitter combiner uses a birefringent crystal that is a fraction of the size of conventional crystals used in similar devices. Since the crystal is considerably shorter in length, the beam passing through the crystal can be uncollimated, spreading very little from one end to the other. Launching uncollimated beams through a short small crystal obviates the requirement for lenses at the end face of the crystal having two waveguides coupled thereto. Since lenses are not required the waveguides at the input/output end face can be very closely spaced apart. Conventional lensed devices utilizing a pair of lenses at an input/output end face must be considerably larger in order to accommodate the lenses and resulting collimated beams.

Abstract: A useful device is provided for coupling or splitting optical signals from one port to another. The symmetry of a lens is utilized in a manner whereby two linear arrays of optical ports are disposed adjacent the optical axis of the lens equidistant from the optical axis of the lens. An at least partially reflecting optical element is disposed at a collimating end of the lens. Signals launched into one array of ports reflects back to the second array of ports at the same end. In another embodiment of the invention utilizing these two linear arrays of waveguides, two matched lenses having an element disposed between are used as a coupler/splitter. In this arrangement ports are positioned on opposite sides of the optical axis equidistant from it.

Abstract: A method and circuit is provided for more efficiently coupling light between two optical waveguides such as optical fibres. When the two waveguides are coupled to spaced apart collimating lenses such as GRIN lenses, the beam propagating between the spaced part lenses may be shifted. In this instance light can more efficiently be coupled out of the output optical fibre if it is angled with respect to the optical axis of the GRIN lens to which it is coupled. This invention provides an output fibre that is non-parallel with the optical axis of the lens it is coupled thereto.

Abstract: An optical fiber having a small numerical aperture (NA) is optically coupled with a short birefringent crystal to provide a polarization beam splitter. This arrangement obviates the use of a GRIN lens coupled between an input optical fiber and the birefringent crystal and provides significant cost savings by allowing a short crystal to be used. In this invention, the birefringent crystal has a beam-shifting angle that is larger than the numerical aperture at the output end of the optical fiber.

Abstract: A polarization beam splitter combiner uses a birefringent crystal that is a fraction of the size of conventional crystals used in similar devices. Since the crystal is considerably shorter in length, the beam passing through the crystal can be uncollimated, spreading very little from one end to the other. Launching uncollimated beams through a short small crystal obviates the requirement for lenses at the end face of the crystal having two waveguides coupled thereto. Since lenses are not required the waveguides at the input/output end face can be very closely spaced apart. Conventional lensed devices utilizing a pair of lenses at an input/output end face must be considerably larger in order to accommodate the lenses and resulting collimated beams.

Abstract: An at least 3-port optical circulator has first group of optical components, and a second group of optical components, the first group being separated from the second group by an optical distance "1". Each group of optical components has a divider and combiner for dividing an input beam into two beams having orthogonal polarizations and for combining two beams having orthogonal polarizations into a single beam. Furthermore, each group has a GRIN lens for at least substantially collimating or focussing input light, and a polarization rotator between the first divider and combiner and the GRIN lens for making two orthogonal polarization vectors parallel or the two parallel polarization vectors orthogonal to one of or both of the first and second group of optical elements having beam shifting means disposed to shift two beams having a predetermined same polarization.

Abstract: A compact non-reciprocal optical waveguide-circulating device comprising three optical waveguides disposed along side one another at an input end adjacent a thin birefringent crystal to which they are optically coupled. The circulating device also includes at a distal end, a mirror for reflecting light backwards and providing a folded configuration. The device is capable of accepting a non-collimated beam of light that is launched from the input end through the birefringent crystal and rotating elements. By providing end faces at one end of the waveguides that are mode field expanded, light is effectively coupled between the waveguides and the adjacent crystal.

Abstract: An optical multiplexing/demultiplexing device has a plurality of optical ports along a cascading optical path with wavelength-specific filters disposed at the ports. The filters are selected to form groups of at least two virtually identical filters. At least one "add" connection is provided for admitting a selected band into the optical path, the connection being disposed at a second or consecutive (third, fourth etc . . . ) filter of the same wavelength as the band being added. The device uses a single medium for processing optical signals, e.g. a single polygonal optical block or air.

Abstract: A multi-port optical circulator for transmitting light from incoming and outgoing ports circularly includes one or more birefringent crystal plates disposed adjacent to one another for dividing an input beam into two beams having orthogonal polarizations and for combining two beams having orthogonal polarizations into a singe beam. Polarization beam splitting cubes introduce a beam to an opposite direction depending on the direction of the polarization of the beam and thereby substantially reflecting only one of s and p-polarizations of the beam. A polarization rotator between the first dividing and combining birefringent crystal and said polarization dependent beam splitting cube makes two orthogonal polarization vectors parallel or the two parallel polarization vectors orthogonal to one another.

Abstract: An optical device comprising an optical element optically coupled with at least two lenses, each lens having at least a substantially collimating end, the at least substantially collimating ends being inwardly facing one another and each lens having a substantially focusing end, the substantially focusing ends being outwardly facing, and at least one waveguide disposed adjacent and spaced from the each outwardly facing end for coupling light to or from an adjacent lens, the waveguides each having an end that is separated from its adjacent lens by an optical distance of approximately d1, an optical distance between the two collimating end faces of the at least two lenses being d2, where d1 is approximately equal to one half d2.

Abstract: An optical isolator for passing light in a forward direction with greater intensity than reverse directed light, is provided. The device includes a conventional isolating means having at least two birefringent crystals, and a non-reciprocal rotating element disposed between the two crystals. The isolating means is disposed between two substantially collimating GRIN lenses, and a thermally expanded core (TEC) output optical fiber is coupled to one of the two lenses and an optical fiber having a thermally expanded core optically coupled to the other of the two collimating lenses. Unwanted reflected incident light is poorly coupled into the input TEC optical fiber due the angle of incidence at the fiber end.

Abstract: An optical device is provided having an input and an output terminal spaced equidistant from an optical axis of a graded index lens. An at least partially reflective surface is disposed spaced but adjacent from another end face of the graded index lens. The optical path length from the input or output terminal to a first end face of the lens is equal to the optical path length from the other end face of the lens to the at least partially reflective surface. The graded index lens has a length that collimates light launched from the input terminal to the at least partially reflective surface. Moving the input an output terminals toward or away from one another changes the angle at which light exits the other end face of the graded index lens, and thus changes the angle at which light is incident upon the at least partially reflecting surface.

Abstract: An optical device is disclosed wherein a first GRIN lens and a second GRIN lens having their optical axes offset. The first GRIN lens has one or more input ports at an input end. The second GRIN lens is disposed to receive light from the first GRIN lens. A reflecting surface is coated onto a second end face of the second GRIN lens or alternatively is disposed adjacent to the second end face and positioned to reflect an input beam of light launched into the input end face of the first GRIN lens. The reflective surface is at a location where light incident upon it to be returned to the first GRIN lens is collimated. By placing a filter and third GRIN lens between the first and second lenses double filtering may be achieved at the pass band or pass wavelength of the filter. Furthermore, the more simple arrangement including only first and second lenses provides a means of directing light into and out of the device at different angles or directions with respect to the optical axis of the first lens.

Abstract: This invention relates to a reflective optical isolating device having at least two stages. In one embodiment a polarization independent optical isolating device has an input/output end and a reflector at another end. An isolator is disposed between the reflector and the input/output end. The isolator includes a non-reciprocal rotator in the form of a Faraday rotator, and in one embodiment the isolator also includes two reciprocal rotators. A first end of the isolator includes a birefringent crystal for separating an input beam of light in an input direction and for combing two beams of light in an output direction. The isolator also includes a second birefringent crystal at the other end for combining a separated beam of light on route to the reflector and for separating a combined beam of light in the output direction. In one embodiment two separate single isolation stages are provided, and in another embodiment two stage isolation is provided without providing two single stages of isolation.