Abstract: A double clad fiber includes a core, a first cladding provided so as to cover the core, and a second cladding provided so as to cover the first cladding. The second cladding has a plurality of pores extending in a length direction and arranged so as to surround the first cladding. In at least one fiber end, the second cladding has been removed by mechanical processing so that the at least one fiber end is formed by the core and the first cladding.

Abstract: A star coupler includes a core embedded in a clad on a major surface of a substrate. The refractive index of the core differs by at least 40% from the refractive index of the clad. The core includes a slab optical waveguide, at least one input-output optical waveguide connected to the slab optical waveguide, and an array of channel optical waveguides connected to the slab optical waveguide. The star coupler also includes a high-index layer having a refractive index intermediate between the refractive indexes of the clad and core, covering the sides of the core orthogonal to the major surface of the substrate. The high-index layer reduces light loss.

Abstract: An optical waveguide for a touch panel in which the intensity of light beams emitted from light-emitting portions of a plurality of light-emitting cores in the form of branches is substantially uniform independently of the branch position of the light-emitting cores, and a touch panel using the same. An optical waveguide for a touch panel is provided in which a plurality of light-emitting cores 33 are formed by dividing a tip portion of a single original core into branches. A portion extending from a basal portion 32b of the original core to a branch point 32c at which the division into the branches serving as the light-emitting cores 33 starts is an isosceles triangular portion 32 gradually widened from the basal portion 32b into the shape of an isosceles triangle. The isosceles triangle has a taper angle ? in the range greater than 0 degrees and less than 15 degrees.

Abstract: A junction is made between a first microfluidic substrate (12) having an elongate component (303) protruding from it and a second microfluidic substrate (22) having a corresponding conduit (261). Each of the substrates has a pair of alignment features, for example planar orthogonal surfaces (13, 15; 23, 25) or grooves (141, 151; 241, 251) in opposite sides of the substrate. The substrates are placed on an alignment jig 6 having location features (63, 65) corresponding to the alignment features. The elongate component can be surrounded by a compressible gasket 40). The substrates are pushed towards each other so that the elongate component enters the conduit and the gasket, if any, is compressed. A fluid-tight junction results so long as the substrates are maintained in the necessary position, either by permanent means, or, if a junction which can be disassembled is needed, by maintaining pressure between the substrates.

Abstract: A plastic optical fiber (POF) based reflective star coupler is provided. The POF based reflective star coupler comprises a hollow cylindrical holding tube for receiving a plurality of plastic optical fibers (POF) at a front end of the holding tube and a mixing rod at a rear end of the holding tube; wherein a rear end of each POF is affixed to a front surface of the mixing rod; a rear convex surface of the mixing rod is coated with a highly reflective coating; and where the POFs, the mixing rod, and the holding tube are made from similar material, having similar refractive index and material properties.

Abstract: Passive optical components may be used to tap the optical power, e.g., from fibers of a wavelength switch system. The passive optical components are realized by a standard photonics light-wave circuit (PLC) integrated to the fiber collimator array of the wavelength switch system. The PLC includes multiple waveguide paths that optically couple optical signals from one or more fiber ports to one or more corresponding free space optical component ports. Optical signals traveling through these waveguide paths are tapped by one or more optical taps and coupled to one or more corresponding tap ports. Each optical tap is located such that an optical signal is tapped after it is coupled into one of the waveguide paths.

Abstract: An optical apparatus including a 360-degree star coupler with derivative structure(s) and applications to optical imaging, optical communications and optical spectroscopy.

Abstract: An optical coherent detector that employs an interleave-chirped arrayed waveguide grating (AWG). The AWG has a periodic chirp pattern that enables the AWG to function as an optical 90-degree hybrid. If the AWG is implemented using a birefringent material, then the AWG can also function as a polarization demultiplexer. In one embodiment, the AWG is designed to simultaneously function as a wavelength demultiplexer, a polarization demultiplexer for each wavelength-division-multiplexed (WDM) signal component, and a 90-degree hybrid for each polarization-division-multiplexed component of each WDM signal component.

Abstract: This document discusses, among other things, a connector for an optical imaging probe that includes one or more optical fibers communicating light along the catheter. The device may use multiple sections for simpler manufacturing and ease of assembly during a medical procedure. Light energy to and from a distal minimally-invasive portion of the probe is coupled by the connector to external diagnostic or analytical instrumentation through an external instrumentation lead. Certain examples provide a self-aligning two-section optical catheter with beveled ends, which is formed by separating an optical cable assembly. Techniques for improving light coupling include using a lens between instrumentation lead and probe portions. Techniques for improving the mechanical alignment of a multi-optical fiber catheter include using a stop or a guide.

Abstract: Provided are a waveguide structure and an arrayed waveguide grating structure. The arrayed waveguide grating structure includes an input star coupler, an output star coupler, and a plurality of arrayed waveguides optically connecting the input star coupler and the output star coupler. Each of the arrayed waveguides includes at least one section having a high confinement factor and at least two sections having a relatively low confinement factor. The sections of the arrayed waveguides having a high confinement factor have the same structure.

Abstract: An optical component including an acceptance fiber, e.g. a photonic crystal fiber, for propagation of pump and signal light, a number of pump delivery fibers and a reflector element that reflects pump light from the pump delivery fibers into the acceptance fiber. An optical component includes a) a first fiber having a pump core with an NA1, and a first fiber end; b) a number of second fibers surrounding the pump core of the first fiber, at least one of the second fibers has a pump core with an NA2 that is smaller than NA1, the number of second fibers each having a second fiber end; and c) a reflector element having an end-facet with a predetermined profile for reflecting light from at least one of the second fiber ends into the pump core of the first fiber.

Abstract: An apparatus includes one or more optical de-interleavers. Each optical de-interleaver includes an optical component having a first pair of optical input and output ports and a second pair of optical input and output ports and a 1×2 optical coupler. Each optical output port of the optical component is optically connected to a corresponding optical port of the 1×2 optical coupler. The optical component is constructed to operate as a first optical filter for light propagating between the optical ports of the first pair and is constructed to operate as a second optical filter for light propagating between the optical ports of the second pair. The first and second optical filters have substantially regularly spaced and interleaved passbands.

Abstract: Fiber optic sensors commonly require a 180 degree turnaround to form a continuous optical circuit. Methods and apparatus for providing 180 degree turnarounds in a fiber optic system that include a shorter radius turnaround then provided by micro-bending the optic fiber are desired. An embodiment of a turnaround apparatus includes a first optic fiber pigtail, a second optic fiber pigtail, and an optical waveguide forming a U-shaped path having an input end optically connected to a first end of the first pigtail and an output end optically connected to a first end of the second pigtail.

Abstract: Provided is a photonics device including at least two arrayed waveguide grating structures. Each of the arrayed waveguide grating structures of the photonics device includes an input star coupler, an output star coupler, and a plurality of arrayed waveguides optically connecting the input star coupler to the output star coupler. Each of the arrayed waveguides includes at least one first section having a high confinement factor and at least two second sections having a low confinement factor. The first sections of the arrayed waveguides have the same structure.

Abstract: A micro-cavity measuring equipment based on double optical fiber coupling includes a sight and transmitter, a controller, and a length measuring device. The equipment detects small changes in the position of an object with respect to a probe from a moment when the sight and transmitter starts working to another moment when the sight and transmitter stops working. The controller has a program to automatically control the whole measuring process. The measuring equipment is characterized in that the sight and transmitter consists of a laser unit, a data collecting and processing unit, and a double optical fiber coupling unit with its ends of incident and effluent optical fibers fixed on a coupler.

Abstract: The invention discloses an electrical connector device, which includes an optic fiber hub and a plurality of electrical embedded interfaces connected to the optic fiber hub. The optic fiber hub is connected to monitoring equipments or communication networks, and the electrical embedded interfaces are installed electrical devices and connected to the optic fiber hub, such that the electrical devices can transmit data and instructions to the monitoring equipments, the communication networks or each other by the electrical connector device.

Abstract: The present invention provides an optical access network system that allows the transmission of packets irrespective of the packet length and which is also capable of adapting to cases where another user temporarily requires a large capacity bandwidth. This system performs two-way optical communications using a code division multiplexing system via an optical fiber channel and a star coupler between an optical line terminal and first and second optical network units. The optical line terminal comprises a bandwidth control section and a bandwidth allocation section and the bandwidth control section has signal converter pairs installed therein in a number equal to the number of optical network units. Further, the optical network units each comprise first and second bandwidth control sections and first and second bandwidth allocation sections. The bandwidth control sections each have one set of signal converter pairs installed therein.

Abstract: Various embodiments include means of reducing wavelength dependency of an optical device by causing oscillating modes within at least one terminal associated with the device.

Abstract: A planar optical device useful as a low order wavelength router is realized by using a waveguide grating comprising two curved arrays of opposite curvatures. The diffraction order is determined by the angles of rotation of the two curved arrays, and any nonzero order less than about 30 can be realized. This arrangement is smaller, and performs better than a previous grating using a combination of three curved arrays.

Abstract: The present invention is a method and an apparatus for tuning an optical delay line. In one embodiment, an optical delay line includes at least one ring resonator in which light is guided or is confined and at least one heater positioned laterally from the ring resonator. The heater produces heat in a localized area, allowing for the tuning of individual delay elements with minimal crosstalk.

Abstract: Provided is an optical wavelength coupler using a multi-mode interference. The optical wavelength coupler is a planar waveguide type optical device that can distribute or couple two optical signals having different wavelengths by using the multi-mode interference. The optical wavelength coupler is suitable for integration and is small-sized. Also, the optical wavelength coupler has a low manufacturing tolerance and a low loss, and is insensitive to TE/TM polarization.

Abstract: A monolithically integrated optoelectronic subassembly having a waveguide layer stack which is applied on a substrate and has a fiber light-receiving waveguide layer in which at least one photodiode is waveguide-integrated is proposed. A plurality of photodiodes is integrated in the waveguide which is structured laterally and/or vertically in such a manner that there is connected to a coupling waveguide an optical distribution network which in turn feeds the plurality of waveguide-integrated photodiodes in parallel via waveguide parts, which photodiodes are connected electrically in series. All the components are integrated on one chip and conversion of an optical input power into an electrical power is undertaken for current supply purposes. A photodiode can be configured as a signal diode which is supplied from the remaining of the plurality of diodes, as a result of which a self-supplied photodetector is formed.

Abstract: An optical apparatus including a 360-degree star coupler with derivative structure(s) and applications to optical imaging, optical communications and optical spectroscopy.

Abstract: A composite structure for storing thermal energy. In one embodiment, an apparatus for storing thermal energy includes: a thermal storage material and a three-dimensional structure. The three-dimensional structure includes: a plurality of first truss elements defined by a plurality of first self-propagating polymer waveguides and extending along a first direction; a plurality of second truss elements defined by a plurality of second self-propagating polymer waveguides and extending along a second direction; and a plurality of third truss elements defined by a plurality of third self-propagating polymer waveguides and extending along a third direction. The first, second, and third truss elements interpenetrate each other at a plurality of nodes to form a continuous material. The first, second, and third truss elements define an open space. The thermal storage material occupies at least a portion of the open space, and the three-dimensional structure is self-supporting.

Abstract: A daisy-chain optical interconnection technique provides connectivity among a plurality of circuit boards. A plurality of optical cables is connected between pairs of the circuit boards to form a ring. Optical connection matrices disposed on each circuit board accept the ends of the optical cables. The optical connection matrices include optical vias to connect selected ones of the optical paths between ends of the optical cables. Unselected ones of the optical paths are coupled to optical transmitters and optical receivers on each board.

Abstract: An optical filter module for wavelength multiplexing and demultiplexing and a method of manufacturing the same are provided. The optical filter module for wavelength multiplexing and demultiplexing includes: at least one or more input waveguides; an input-stage star coupler in the form of a slab waveguide connected to the input waveguides; array waveguide which is connected to the input-stage star coupler and in which a plurality of individual waveguides, each of which has an optical path having a predetermined length different to those of the other waveguides and has a heterogeneous waveguide interval formed of a material having a different refraction index from that of a core of the waveguides, are sequentially arranged; an output-stage star coupler in the form of a slab waveguide connected to the array waveguides; and at least one or more output waveguides connected to the output-stage star coupler.

Abstract: An optical integrated device includes an optical waveguide structure formed on a semiconductor substrate and including a plurality of first channel optical waveguide portions, an optical coupler portion and a second channel optical waveguide portion, a burying layer formed from a semi-insulating semiconductor material and burying the optical waveguide structure therein such that an upper portion thereof forms a flat face and a side portion thereof forms an inclined face having a predetermined angle with respect to the semiconductor substrate, and a plurality of dummy structure bodies provided over a desired region in the proximity of at least an output side of the optical coupler portion so that radiation light from the optical coupler portion is spatially separated from signal light propagating along the second channel optical waveguide portion. The plural dummy structure bodies are provided discretely so as to be buried flat by the burying layer.

Abstract: A plastic optical fiber (POF) based reflective star coupler is provided. The POF based reflective star coupler comprises a hollow cylindrical holding tube for receiving a plurality of plastic optical fibers (POF) at a front end of the holding tube and a mixing rod at a rear end of the holding tube; wherein a rear end of each POF is affixed to a front surface of the mixing rod; a rear convex surface of the mixing rod is coated with a highly reflective coating; and where the POFs, the mixing rod, and the holding tube are made from similar material, having similar refractive index and material properties.

Abstract: Provided are a waveguide structure and an arrayed waveguide grating structure. The arrayed waveguide grating structure includes an input star coupler, an output star coupler, and a plurality of arrayed waveguides optically connecting the input star coupler and the output star coupler. Each of the arrayed waveguides includes at least one section having a high confinement factor and at least two sections having a relatively low confinement factor. The sections of the arrayed waveguides having a high confinement factor have the same structure.

Abstract: An integrated chip for data communication, telecommunication and optical analysis for at least one, two or more wavelengths where the chip can be used not only to emit light but also to detect light. The invention is characterised in that the chip (1) includes a waveguide (2) with a first port (3), in that the waveguide (2) expands from the first port (3) in the direction of at least one second waveguide (4) and one third waveguide (6) with at least one second port (5) and one third port (7), respectively, these being placed parallel to each other or at an angle to each other, and separated by a certain distance, and in that the various components of the chip (1) are monolithically integrated.

Abstract: An optical switch, comprises: a plurality of N input ports (2); a plurality of M output ports (24); and a plurality of displaceable beam steering arrangements (1) which, during switching, displace; N being greater or equal to 3 while M is greater or equal to 2; the plural number of displaceable arrangements substantially corresponding to either N or M; wherein said displaceable arrangements displace to and from positions of interception of substantially entire beams originating from said input ports and direct said beam on a path to said output port.

Abstract: The present invention provides an optical system with waveguides, which comprises first, second and third optical input/output means (12, 14, 16), fourth and fifth multi-mode optical waveguides (20, 22) each capable of propagating light with plural propagation modes, and optical-filter mounting means (26) for mounting an optical filter (24) between the fourth and fifth multi-mode optical waveguides (20, 22) across a traveling direction of light in the fourth and fifth multi-mode optical waveguides (20, 22). The first optical input/output means (12) is connected to an end face of the fourth multi-mode optical waveguide (20) on a side thereof opposite to the optical-filter mounting means (26). Each of the second and third optical input/output means (14, 16) is connected to an end face of the fifth multi-mode optical waveguide (22) on a side opposite to the optical-filter mounting means (26).

Abstract: The present invention relates to an optical module that has a structure for protecting a pumping light source at a low cost. The optical module comprises an amplification optical fiber, an optical coupler, a pumping light source, a delay optical fiber, a seed light source, an optical fiber, a photodetector, an optical fiber, an optical isolator, an optical isolator, and a control section. Through the insertion of the delay optical fiber between the pumping light source and the optical coupler, the timing of the output control of the pumping light source which is carried out after the photodetector detects return light leads the timing with which the return light enters the pumping light source. Hence, the time with which the return light enters the pumping light source is shortened and the accumulative damage time of the pumping light source is reduced.

Abstract: The invention relates to an optical fiber combiner and a method for the manufacture thereof. The combiner has a tapering support preform with a plurality of capillary bores, a plurality of input fibers including a core and a cladding around the core and being arranged in parallel in the capillary bores of a support preform, and an output fiber coupled to the tapered end of the support preform in optical connection with the input fibers. The cladding thickness to core thickness ratio of at least one of the input fibers is decreased at the region of the support preform. The invention provides an optically high quality fiber combiner.

Abstract: Provided is a photonics device. The photonics device includes: a substrate including a star coupler region and a transition region; a lower core layer formed on the substrate; and upper core patterns formed on the substrate to define a waveguide. The upper core patterns are disposed on the lower core layer at the transition region, so that the transition region has a multi-layered core structure.

Abstract: An optical coupler for coupling light from at least two input fibers into one output fiber and a method of fabricating and use of an optical coupler. The coupler comprises a) an input section comprising an output end face at one end of the bundling-length of input fibers; and b) an output section comprising an output fiber comprising a confining region for confining light propagated in the input fibers and a surrounding cladding region and having an input end face; wherein the output end face of said input section is optically coupled to the input end face of the output section and at least the confining region of the output fiber is tapered down from a first cross sectional area at the input end face to a second, smaller cross sectional area over a tapering-length of the output fiber.

Abstract: A wavelength independent multi-section optical coupler having at least three optical couplers, and at least two differential phase cells. Each optical coupler has two waveguides forming a coupling region having a net coupling value. The coupling value for each coupling region of the at least three optical couplers is different than the coupling values of the other two coupling regions. Each differential phase cell connects adjacent ones of said optical couplers. Each differential phase cell causes a differential phase shift in light signals traversing between the optical couplers, wherein the differential phase shifts of the differential phase cells, and the coupling value for each coupling region are chosen so as to minimize wavelength, and fabrication sensitivity of said wavelength independent multi-section optical coupler for a designed power splitting ratio.

Abstract: The invention relates to phase matched optical gratings for performing signal multiplexing and demultiplexing in optical communications networks. In prior art gratings there is a phase linearity error between the grating line and the outputs on the focal line, comparing the center output to the surrounding outputs. This corresponds to a relative phase difference between each output which limits the passband. In the case of the AWG this degradation comes primarily from field aberrations in the output star coupler. The present invention has found that if the grating line of the optical grating is disposed on a ellipse instead of a circular arc, while the focal line of outputs defines a substantially circular arc, an optimum can be found where the phase linearity error is substantially eliminated, and all outputs have substantially the same phase. As a result, this creates substantially uniform passbands across the WDM spectrum.

Abstract: The present invention relates to an optical component comprising an acceptance fibre, e.g. a photonic crystal fibre, for propagation of pump and signal light, a number of pump delivery fibres and a reflector element that reflects pump light from the pump delivery fibres into the acceptance fibre. It is an object of the invention to provide a fibre coupler for coupling two or more light sources into a multi-clad (e.g. double clad) optical fibre, which has practical advantages with respect to handling, loss and back reflection.

Abstract: An optical planar wavelength selective filter is formed on a printed circuit substrate. Low optical loss polymers are used to make a layered structure that contains waveguides and free travel zones. A diffraction grating is strategically placed on the printed circuit substrate so that light from one waveguide is diffracted by the grating to exit the free travel zone and pass through the other waveguides. The low optical loss polymer is a reaction product of the hydrolysis and polycondensation reaction of organically functionalized alkoxysilanes. With a proper grating, the apparatus can be used as an optical triplexer at frequencies of 1310, 1490, and 1550 nanometers.

Abstract: A blocking portion is provided at an end of the mirror to prevent a light beam emitted from an input port from being transmitted to or reflected by first and second output ports. The mirror is inserted to a position where the end of the blocking portion of the mirror reaches a boundary P2? on the insertion side of an area to be blocked to obtain a permissible crosstalk value of the light beam. The mirror is removed to a position where the rear end of the blocking portion of the mirror reaches a boundary P2 on the removal side of the area to be blocked. The mirror is movably driven between the removal position and the insertion position in the optical path of a first light beam by a drive. Thus it is possible to reduce the length of the driving stroke of the mirror.

Abstract: An optical splitter has an optical chip, in which a conductor track is arranged on a carrier substrate, wherein a conductor track section of the conductor track running from a first side of the chip branches into different conductor track sections which run to a second side of the chip via a plurality of branching nodes. An optical waveguide section of an optical waveguide is bonded at the first side of the chip by means of an adhesive material. Correspondingly, optical waveguide sections are bonded on the second side of the chip by means of an adhesive material. In order to reinforce the fixing, glass plates are arranged over and under the optical waveguides, said glass plates being bonded to the optical chip at the respective lateral surfaces.

Abstract: A diffraction grating of the present invention includes a first block (101) and a second block (102). The first block (101) is made up of a plurality of input waveguides (103), a slab waveguide (104), a delay waveguide array (105) and narrow grooves (106): each of which being filled with resin. The second block (102) is made up of a plurality of input waveguides (107), a slab waveguide (108) and a plurality of output waveguides (109). Since a circuit is cut off at the ends of the arrayed waveguides, a relative phase can easily be measured. The resin has undergone a refractive-index adjustment and compensates a phase error.

Abstract: A multi-port coupler for coupling an pumping light source to a cladding pump fiber for optical amplification, includes a central signal fiber and a plurality of pumping fibers arranged around the central signal fiber, the central signal fiber and the plurality of pumping fibers being unified and a front side is reduced in diameter, wherein an emitted light confining waveguide part is provided around a core of the signal fiber located at the center, and the emitted light confining waveguide part whose outer diameter is larger than that of the core has a higher refractive index than a cladding and a lower refractive index than the core and the emitted light confining waveguide part is formed continuously from a splicing point of the cladding pump fiber to a coupler front end branched into multiple fibers.

Abstract: A planar lightwave circuit including a slab waveguide, with a plurality of different diffraction filtering elements optically coupling a plurality of input and output ports, provides various optical functionalities including multiplexing, demultiplexing, diplexer and triplexer. In the basic configuration one or more output ports are optically coupled to an input port via grating filters etching in the cladding of the slab waveguide, and an additional port is optically coupled to the input port via a diffraction grating etched in an endwall of the slab waveguide. A triplexer platform can be provided by optically coupling photo-detectors to two output ports, which receive wavelength channels demultiplexed from an input signal by two cladding etched filters, and by optically coupling a laser to another input port, which launches an outgoing laser signal at the endwall etched grating filter for coupling into the same fiber that launched the original input signal.

Abstract: A compact optical splitter module is disclosed. One type of compact optical splitter module is a planar attenuated splitter module that includes a branching waveguide network having j?1 50:50 splitters that form up to n?2j output waveguides having associated n output ports, wherein only m<n output ports are suitable for transmitting light to the at least one external output device. This provides a 1×m splitter module wherein each output port has the attenuation of a 1×n splitter module, thereby obviating the need for external attenuation. Another type of compact optical splitter module is a direct-connect splitter module that eliminates the need for an optical fiber array when coupling to external optical fibers. Another type of compact optical splitter module is a microsplitter module that serves as device and module at the same time and that eliminates the differentiation between device and module. The integration of device and module also makes manufacturing the microsplitter module cost-effect.

Abstract: The invention relates to a method and a device for coupling fiber optic cables. Said device comprises at least one module, which is equipped with at least one retaining unit for retaining at least two cassettes. The invention is characterized in that: a cassette is configured with at least one coupling element; at least one strand bundle can be fixed to the module, whereby said strand bundle can be split into at least two strands comprising at least one fiber optic cable; an excess length of strand can be retained by a cassette, the fiber optic cable or cables being connected to the coupling element and the cassette together with its retained strand being detachably connected to the retaining unit.

Abstract: In order to achieve an increased reliability in respect of failure in optical networks, the invention provides a passive star coupler comprising a multiplicity of at least three optical waveguides as arms of the star coupler, which are combined at one end, and comprising, adjacent to the combined end, a reflective light mixer in the form of a common individual optical waveguide section with a light reflector, which reflects light which is guided through one of the optical waveguides and passes through the adjacent common individual optical waveguide section back into the common individual optical waveguide section, such that the light is split between the individual optical waveguides and is forwarded through the latter.

Abstract: An optical channel monitor assembly for simultaneously measuring the optical power levels of multiple series of dense wavelength division multiplexed channels or the like traveling on separate optical fibers in an optical communications system includes an arrayed waveguide grating router having a first side and a second side, the first side including a first plurality of ports and the second side including a second plurality of ports, the first plurality of ports in optical communication with the second plurality of ports, wherein the first side includes a first input port for collectively receiving a first series of optical channels, wherein the second side includes a first plurality of output ports for individually delivering the first series of optical channels, wherein the second side includes a second input port for collectively receiving a second series of optical channels, and wherein the first side includes a second plurality of output ports for individually delivering the second series of optical cha

Abstract: Techniques for designing optical devices with high reflection isolation are disclosed. According to one aspect of the devices, a pair of conjugate optical filters is used. To preserve the performance of the filters and minimize insertion loss, a lens has a first side and a second side, the first side being preferably perpendicular to an optical axis of the lens, and the second side being nearly perpendicular to the optical axis of the lens. Thus one of the conjugate optical filters is deposed towards the first side of the lens and the other one of the conjugate optical filters is deposed towards the second side of the lens. When a reflected light from one filter, presumably carrying residuals of a transmitted signal, hits another filter, the residuals are blocked, resulting in great isolation for the R-channel from the T-channel.