Abstract: A structure and method for adjusting waveforms of optical filters used in a DWDM system comprises a filter, a GRIN lens and a biporose pigtail with two holes therein. The holes are parallel to a center-axis of the pigtail but at different distance from the center-axis thereof, an input and return optical fiber are secured within the two holes. The GRIN lens is provided with a first end coupled with the biporose pigtail, thus signals from the input fiber can input the lens and the reflected signals from the lens can enter into the return fiber. The GRIN lens further defines a second end angularly to the axis thereof. The filter transmits determining wavelength and is joined with the second end of the GRIN lens.

Abstract: An optical fiber collimator using a gradient index rod lens for securing a required long opposing distance and easy handling. The collimator includes a single mode fiber and a gradient index rod lens for receiving an incident light from the single mode fiber and converting the incident light into a collimated light, or condensing an incident light and coupling the condensed incident light to the single mode fiber. A meandering period (pitch) of a ray determined by a refractive index distribution of the rod lens is decided. The gradient index rod lens has a lens length larger by 0.5 meandering periods than a minimum lens length required to obtain a predetermined opposing distance between a pair of the rod lenses.

Abstract: An optical module has first and second optical parts. Each of the optical parts has an optical path extending in a longitudinal direction and an end face intersecting the optical path. The end face of the first optical part faces the end face of the second optical part. Light enters the end face of the second optical part from the end face of the first optical part. An adhesive forms a joint for connecting the end faces of the parts to each other in peripheral portions about the optical paths of the parts.

Abstract: This invention discloses an optical collimator that includes a built-in tap-out projection optical arrangement for projecting a portion of an incoming beam to a tap-out beam-transmission fiber. In one of the preferred embodiments, the built-in tap-out projection optical arrangement further includes a front surface having an incline angle for projecting a portion of an incoming beam to a tap-out beam transmission fiber. In another preferred embodiment, the built-in tap-out projection optical arrangement further includes a prism having a pair of inclined front surfaces for projecting the incoming beam into an output beam and a tap out beam. In yet another preferred embodiment, the built-in tap-out projection optical arrangement further includes a partially reflective front surface and a reflective mirror projecting the incoming beam into an output beam and a tap out beam.

Abstract: The present invention provides the method and apparatus for multi-pass photonic processors with the use of circulators and multiple-fiber collimators. In one embodiment of the present invention, a circulator and a reflective element are placed at either end of a chain of cascaded processors. The circulator at a first end routes the light signal to be processed and passed from one processor to the next, the reflective element at a second end reflects the light to be reprocessed and passed from one processor to the previous, the light signal eventually reaches the circulator again and exits. In another embodiment of the present invention, multiple fiber strands are connected to the collimator of a photonic processor. Furthermore, all fiber strands are paired in order to reroute the light signals for reprocessing in the photonic processor.

Abstract: An apparatus to combine a filter to a collimator includes a filter supporting part to support the filter which has one side coated with an adhesive, and a chucking holder provided in a lower part of the filter supporting part to chuck the collimator. The apparatus also includes an elevation part to elevate the chucking holder toward the filter supporting part, and at least one heating part provided in one side of the filter supporting part to heat a region of contact between the collimator and the filter. Thus, a filter combining apparatus for a collimator allows the filter to be easily combined to an end of the collimator.

Abstract: A miniaturized lens array for unity magnification imaging comprises a plurality of rod lenses arranged in one row. An arrangement pitch D of the rod lenses is defined to satisfy (2 m+1)·D≦2.1 mm or 2.5 mm. An angle of aperture &thgr; of the rod lens is defined to satisfy &agr;D/6×{n·cos−1(−&agr;/2/m)+(4 m2/&agr;2−1)1/2}≦&thgr;≦&agr;D/2×(4/m2/&agr;2−1)1/2. The arrangement pitch D and angle of aperture &thgr; are defined in this manner, and it is therefore possible to obtain the lens array whose difference between a total width and effective lens width is equal to or smaller than 2.1 mm or 2.5 mm.

Abstract: A method of coupling laser-radiation into an optical fiber includes providing a stack of diode-laser bars and first and second parallel mirrors, the second mirror is selectively reflective only for one polarization plane of the laser-radiation. Each of the diode-laser bars includes at least two spaced-apart diode-laser emitters each emitting a plane-polarized beam of laser-radiation having a fast axis and a slow axis. The laser-radiation beams are collimated in the fast axis by a cylindrical lens located in front of each bar. In one arrangement the polarization orientation of one collimated beam from each diode-laser is rotated by 90 degrees and transmitted through the selectively-reflective mirror. The other collimated beam from each diode-laser bar is reflected onto the selectively-reflective mirror by the first mirror and reflected from the selectively-reflective mirror such that the reflected beam combines with the transmitted beam to form a combined beam.

Abstract: An automatic device for assembling a fiber collimator. The fiber collimator includes a transparent tubular holder, an optical fiber having a first end surface disposed at an end of the tubular holder, and a GRIN lens having a second end surface disposed at the other end of the tubular holder. The automatic device includes an image pick-up device, a processor, a first driving table for rotating and moving the optical fiber, and a second driving table for rotating and moving the GRIN lens. The image pick-up device films the first and second end surfaces, and outputs image data corresponding to the first and second end surfaces. The processor receives and processes the image data to control the first and second driving table to rotate so that the first and second end surfaces are parallel to each other, and control the first and second driving table to move so that a distance between the first and second end surfaces is equal to a predetermined value.

Abstract: A collimator array includes a plurality of collimators. Each collimator includes a lens and an optical fiber optically coupled to the lens. The lens is arranged so that its optical axis is parallel to one another. In each collimator, a core axis of the optical fiber is positioned relative to the optical axis of the lens so that an optical beam is emitted from a predetermined position at a predetermined angle.

Abstract: An optical collimator comprises an optical fiber (210), a ferrule (220), a GRIN lens (230), a metal sleeve (240), and an outer metal tube (250). The optical fiber has an exposed end which is inserted into the ferrule and glued thereinto. The GRIN lens is glued into the sleeve. Opposite ends (232, 234) of the GRIN lens protrude from opposite ends of the sleeve. The outer tube includes first and second receiving portions (252, 254). The ferrule is glued into the first receiving portion, and the sleeve is secured in the second receiving portion. A plurality of soldering holes (256) is defined in a periphery of the outer tube. Soldering is applied to the sleeve through the holes to firmly connect the outer tube and the sleeve together. A position of the GRIN lens relative to the optical fiber can be easily readjusted by re-soldering the sleeve.

Abstract: The invention is a method for manufacturing an optical module where on forms a groove in a substrate for positioning a component such as an optical component. The optical component is provided to be bonded into the groove by a aluminum oxide bonding process. To prepare the bonding an aluminum layer is deposited on the optical component followed by a protection layer.

Abstract: A zigzag wavelength division multiplexer. The zigzag wavelength division multiplexer reduces the wavelength shift in the center of a frequency band caused by temperature changes. The zigzag wavelength division multiplexer includes an intermediate block, an input end and a plurality of output ends. The input end has a first sleeve and an optical collimator disposed in the first sleeve. Each of the output ends has a second sleeve, a wave filter and an optical collimator. The optical collimator and the wave filter are disposed in the second sleeve. The zigzag wavelength division multiplexer reduces use of the GRIN lens and glass ferrule, and thereby manufacturing costs.

Abstract: The invention provides an optical isolator including a light collector for redirecting and/or absorbing backward propagating radiation. In the preferred embodiment, the light collector includes at least one of a light absorbing material and a light redirector that does not interfere with forward propagating radiation, but collects the unwanted backward propagating light. Accordingly, the light collecting means are suitable for high power applications for protecting the input optics, including epoxy used to secure the input optical fiber, from unwanted reflected light. Some examples of appropriate light collecting means include neutral density filters, polarizers, mirrors, and right angle prisms.

Abstract: A method and system for providing an optical switch is described. The method and system include providing a triple fiber collimator, a beam deflector and a reflector. The triple fiber collimator is for receiving an optical signal from a first fiber and outputting the optical signal to a second fiber or a third fiber. The beam deflector has a first portion and a second portion. The beam deflector resides between the reflector and the triple fiber collimator. The optical signal travels through the first portion of the beam deflector, is reflected by the reflector and is output over the second fiber when the beam deflector is in a first position. The optical signal travels through the second portion of the beam deflector, is reflected by the reflector and is output over the third fiber when the beam deflector is in a second position.

Abstract: A concept of designing a Variable Optical Attenuation Collimator (VOAC) is disclosed to achieve a variable degree of optical power attenuation through the collimator by adding an Attenuation Control Element (ACE) between a lens element and fiber pigtails of a traditional fiber optical collimator. The body of the ACE can be implemented in many different forms of a light blocker element capable of being controllably moved into a main light path of the VOAC to obstruct a controlled portion of light power. The light blocker can be a Micro Electro Mechanical Structure (MEMS) operating with a controlled electrostatic force, a bimetal wire driven by a controlled heating current, an electrical current-carrying wire within a surrounding permanent magnetic field or a deflectable permanent magnetic wire within a controlled surrounding magnetic field.

Abstract: An optical functional component is provided in which alignment of optical fibers is simplified, a gap between an end face of the optical fiber and an end face of a lens is minimized, and stability of performance is improved. An optical functional component comprises a first refractive index distribution type lens, one end face of which is ground diagonally, first and second ports connected to the diagonally ground end face, an optical functional element connected to an other end face of the first refractive index distribution type lens, a second refractive index distribution type lens, one end face of which is ground diagonally, and another end face placed so as to face the end face of the first refractive index distribution type lens through the optical functional element, and a third port connected to the diagonally ground end face.

Abstract: A method and system for providing a dense wavelength division multiplexer is disclosed. The method and system include providing a dual fiber collimator, a filter and a filter holder. The dual fiber collimator includes a lens and a capillary. The capillary is for holding a plurality of fibers. The filter holder has an aperture therein. The filter is disposed between the dual fiber collimator and the filter holder. The filter has a first surface and a second surface opposite to the first surface. The first surface is covered with a filter coating. The filter is affixed to the filter holder by the second surface.

Abstract: A groove portion to stay the adhesive agent penetrated into either one of closely contacted surfaces of the rod lens and the optical filter is formed, thereby, the penetration of the adhesive agent into the optical path is prevented.

Abstract: A method for coupling several non-radial light sources to a light guide having an input end, where the light guide has, in a cross-section perpendicular to the direction of propagation of light, an at least partly curved form, and the light sources are coupled on the edge region at the input end of the light guide.

Abstract: An optical switch (99) includes a housing (10), a driver (50), a first I/O port (20), a second I/O port (40) and a switching element (32). Each I/O port has a collimator (27,47) and attaches to input and to output fibers. The housing holds the first I/O port and the second I/O port in alignment with one another and supports the driver on a substrate (11) of the housing. The switching element is rotationally attached to the driver and has a first and second mirrors (322, 323) and a GRIN rod lens (324). The driver drives the switching element between a first position, wherein the rod lens aligns with the I/O ports, and a second position, wherein the mirrors align with the I/O ports. Thus light signals from input fibers are variously directed to output fibers on an opposite side, or on the same side, of the optical switch.

Abstract: A mode converter includes first and second optical waveguides and a GRIN fiber lens. The GRIN fiber lens is attached to both the first and the second waveguides.

Abstract: An optical collimator comprises an optical fiber, a capillary, a GRIN lens and a glass tube. A bore is defined in the capillary. A conical depression is defined in an end of the capillary and in communication with the bore. The optical fiber is retained in the bore of the capillary. An end of the capillary is bonded with an end of the GRIN lens. The capillary and the GRIN lens are encased in the glass tube.

Abstract: A rod lens for an optical communication module is not easily damaged. An input side end surface of the rod lens has an inclined surface. The inclined surface is inclined by a predetermined angle with respect to a central axis of the rod lens to reduce the reflection loss. A flat contact surface, which is perpendicular to the central axis, is formed on the distal end of the rod lens. By simply arranging two of the rod lenses to contact each other, the rod lenses are optically coupled in the optimum manner without being damaged.

Abstract: This invention provides a novel wavelength-separating-routing (WSR) apparatus that uses a diffraction grating to separate a multi-wavelength optical signal by wavelength into multiple spectral channels, which are then focused onto an array of corresponding channel micromirrors. The channel micromirrors are individually controllable and continuously pivotable to reflect the spectral channels into selected output ports. As such, the inventive WSR apparatus is capable of routing the spectral channels on a channel-by-channel basis and coupling any spectral channel into any one of the output ports. The WSR apparatus of the present invention may be further equipped with servo-control and spectral power-management capabilities, thereby maintaining the coupling efficiencies of the spectral channels into the output ports at desired values.

Abstract: Generally, the present invention relates to a new approach to angle tuning a thin film, interference filter device in which the light is delivered to the filter from a fiber lying off-axis relative to the filter, and to a method of optically coupling such a device. An embodiment of the invention is directed to an optical device comprising a lens unit having an optical axis and an adjustable effective focal length. The optical device includes a first port disposed on a first side of the lens unit and on a first side of the optical axis, and an optical element disposed on the second side of the lens unit, the optical element having an optical characteristic that is dependent on the angle of incidence on the optical element. Wherein the lens unit has an adjustable focal length adjusted so that light from the first port is incident on the optical element at a desired optical characteristic of the optical element.

Abstract: An optical collimator (20) includes an optical fiber (21), a metal ferrule (22), a Graded Index (GRIN) lens (23) and an outer metal tube (24). The optical fiber has an exposed end (211) which is coated with metal. The exposed end of the optical fiber is inserted into the ferrule and laser welded thereto. The GRIN lens is also coated with metal. A plurality of soldering holes (241) is defined in a periphery of the outer tube. Solder is applied to the ferrule and the GRIN lens through the holes to firmly connect the outer tube, the ferrule and the GRIN lens together. After assembly, if the position of the GRIN lens or the optical fiber is found to be inaccurate, the GRIN lens and the ferrule can be easily resoldered.

Abstract: An automatic device for assembling a fiber collimator. The fiber collimator includes a tubular holder, an optical fiber disposed at an end of the tubular holder, and a GRIN lens disposed at the other end of the tubular holder. The automatic device includes a screen, a laser light-source and a driving table. The laser light source emits a laser light to the GRIN lens to obtain a first elliptic pattern and a second elliptic pattern on the screen, wherein the first elliptic pattern has a first major axis and the second elliptic pattern having a second major axis. The driving table rotates the optical fiber until the first major axis of the first elliptic pattern is parallel to the second major axis of the second elliptic pattern.

Abstract: A method for aligning an optical assembly, including the steps of emitting at least one beam from an emitter substantially along a first axis, disposing a cylindrical lens in said at least one beam to form at least one line image, wherein a longitudinal axis of said cylinder lens is substantially parallel to a second axis which is different from said first axis, displaying at least one vertical profile of said at least one line image, defocusing said at least one line image until a first peak and a second peak of said at least one profile are displayed and adjusting in a third axis which is different from said first axis and said second axis a position of said cylindrical lens relative to said emitter until said first peak and said second peak are symmetric.

Abstract: A micro optical bench for mounting precision aligned optics thereon, and an assembly of precision aligned optical components mounted on an micro optical bench.

Abstract: A high reflection isolation device includes a metal tube (1), a glass tube (2) enclosed by the metal tube, a dual fiber pigtail (DFP) (3) having a first fiber (30) and a second fiber (32), a GRIN lens (4) engaging with the metal tube via certain adhesive (7), a first filter (5) mounted on the GRIN lens and a second filter (6) mounted between the dual fiber pigtail and the GRIN lens. Light input from the first fiber passes through the GRIN lens and encounters the first filter. The first filter passes only a first wavelength of light and reflects all others, which pass back through the GRIN lens to the second filter. The second filter passes only a second wavelength of light, which is transmitted into the second fiber.

Abstract: An optical add/drop multiplexer capable of extracting signals from within a specified waveband in a group of signals containing various wavelengths, and then adding back a new set of signals also within the specified waveband. The multiplexer includes an optical filter plate, a plane reflector and three graded-index lenses. Using a single optical filtering plate and a plane reflector to carry out multiple reflections, intra-band isolation of light signals is improved and cost of production is reduced.

Abstract: This invention provides a novel wavelength-separating-routing (WSR) apparatus that uses a diffraction grating to separate a multi-wavelength optical signal by wavelength into multiple spectral channels, which are then focused onto an array of corresponding channel micromirrors. The channel micromirrors are individually controllable and continuously pivotable to reflect the spectral channels into selected output ports. As such, the inventive WSR apparatus is capable of routing the spectral channels on a channel-by-channel basis and coupling any spectral channel into any one of the output ports, thereby constituting a dynamic optical drop module (RODM). By operating an RODM in reverse, a dynamic optical add module (ROAM) is also provided. The RODM (or ROAM) of the present invention may be further equipped with servo-control and power-management capabilities.

Abstract: This invention discloses an optical collimator that includes a built-in tap-out projection optical arrangement for projecting a portion of an incoming beam to a tap-out beam-transmission fiber. In one of the preferred embodiments, the built-in tap-out projection optical arrangement further includes a front surface having an incline angle for projecting a portion of an incoming beam to a tap-out beam transmission fiber. In another preferred embodiment, the built-in tap-out projection optical arrangement further includes a prism having a pair of inclined front surfaces for projecting the incoming beam into an output beam and a tap out beam. In yet another preferred embodiment, the built-in tap-out projection optical arrangement further includes a partially reflective front surface and a reflective mirror projecting the incoming beam into an output beam and a tap out beam.

Abstract: A compact optical apparatus for use in optical communication is provided which can be manufactured at low costs with ease. A common terminal is mounted to receive diverging light with a long wavelength and to output light with a short wavelength, and an input terminal is mounted to receive light with a short wavelength. An output terminal is mounted to transmit light with the long wavelength to a light receiver. A wavelength selecting filter permits the light with the long wavelength to pass to the light receiver and reflects light transmitted from the input terminal so as to selectively direct it to the common terminal. First and second computer-generated hologram devices guide diverging light from the input terminal to the common terminal via the wavelength selecting filter.

Abstract: A method of manufacturing a collimating assembly includes the following steps: preparing a GRIN lens subassembly; preparing a dual-fiber (DF) pigtail subassembly; fitting the GRIN lens subassembly and the DF pigtail subassembly together; applying epoxy onto a junction zone between the GRIN lens subassembly and the DF pigtail subassembly; and baking the junction zone for curing the epoxy thereof until the epoxy spreading uniformly over the junction zone due to the so-called capillarity phenomenon.

Abstract: An improved optical isolator having a pre-aligned first and second collimator and a pre-aligned core assembly joined with the first collimator, the first and second collimators and core assembly all disposed within a housing tube. The core assembly is aligned with and joined directly to the first collimator and fits snugly within the housing tube. The second collimator fits within the housing tube such that it can be aligned with core assembly to minimize insertion loss. The first and second collimators are connected to the housing tube by solder joints, at least one of which is made from a low temperature solder. The core assembly includes a cylindrical permanent magnet, a pair of birefringent wedges and an optical rotator. The optical rotator is joined to a wedge on either side and the combined structure is affixed to the cylindrical permanent magnet.

Abstract: An optical package comprises an optical element (e.g., a filter), a reflective surface, an input optical fiber and an output optical fiber. A light signal travels through the input fiber and through the element where it is shaped or modified a first time. The shaped light signal is reflected by the reflective surface and is again transmitted through the element where it is shaped or modified a second time. The twice-shaped light signal then travels out through the output fiber. The package thereby utilizes the element two times. The package is useful in wavelength division multiplex (WDM) telecommunication systems and other light processing systems.

Abstract: A gain flattening filter is provided to reduce volume and manufacturing cost of a gain flattened optical fiber amplifier, even when a required peak loss exceeds the limit of each dielectric thin film filter. The inventive gain flattening filter includes: a housing having a first opening and a second opening; a first ferrule disposed at one end of the housing, the first ferrule having an opening through which an input of an optical fiber is packaged; a second ferrule disposed at the other end of the housing, the second ferrule having an opening through which an output of the optical fiber is packaged; and, a plurality of thin film filters disposed in sequence between the first and second ferrules for flattening gain of optical signals passing therethrough.

Abstract: An automatic device for assembling a fiber collimator. The fiber collimator includes a tubular holder, an optical fiber disposed at an end of the tubular holder, and a GRIN lens disposed at the other end of the tubular holder. The automatic device includes a screen, a laser light source and a driving table. The laser light source emits a laser light to the GRIN lens to obtain a first elliptic pattern and a second elliptic pattern on the screen, wherein the first elliptic pattern has a first major axis and the second elliptic pattern having a second major axis. The driving table rotates the optical fiber until the first major axis of the first elliptic pattern is parallel to the second major axis of the second elliptic pattern.

Abstract: A fiber optic apparatus interfaces a single mode fiber into free space for coupling to active or passive devices with a collimated or parallel ray beam. This is accomplished by splicing or fusing to the end of the single mode fiber one of two types of lenses. The first type uses a graded index fiber which is cut to an odd multiple of a quarter wavelength of the light beam. The second technique is to use a step index fiber with a curved end forming a lens having a length relative to a hypotenuse line along the angle of emission of a single mode fiber to subtend half of the diameter of the core of the step index fiber. This, depending on the curvature at the end of the step index fiber, will produce either a collimated beam or a beam focused to a point.

Abstract: A variable optical attenuator device is provided for modulating an optical signal. The attenuator device includes a variable attenuation assembly with an electrochromic structure interposed between a first electrode and a second electrode. The electrochromic structure is configured to reversibly change its optical characteristics from a bleached off state to a colored active state under the influence of an electrical potential applied to the first and second electrodes to thereby modulate the optical signal. The optical attenuator device includes at least one lens attached to the variable attenuation assembly. The lens cooperates with the variable attenuation assembly to direct the optical signal towards the electrochromic structure. Waveguides such as optical fibers define ports at the outer endface of the lens for the optical signal.

Abstract: This invention provides a novel wavelength-separating-routing (WSR) apparatus that uses a diffraction grating to separate a multi-wavelength optical signal by wavelength into multiple spectral channels, which are then focused onto an array of corresponding channel micromirrors. The channel micromirrors are individually controllable and continuously pivotable to reflect the spectral channels into selected output ports. As such, the inventive WSR apparatus is capable of routing the spectral channels on a channel-by-channel basis and coupling any spectral channel into any one of the output ports. The WSR apparatus of the present invention may be further equipped with servo-control and spectral power-management capabilities, thereby maintaining the coupling efficiencies of the spectral channels into the output ports at desired values.

Abstract: Collimating microlenses are “printed” from optical polymeric materials on the ends of optical fibers using ink-jet technology. In one embodiment the optical fibers are inserted into a collet, a stand-off distance from the open upper end of the collet. The open upper end is filled with optical fluid and a microlens is formed thereon to collimate light exiting the fiber through the microlens. In another embodiment optical fibers from a “ribbon” are separated and installed into a ferrule having multiple openings therethrough. In the same manner as in the collet embodiment, the ferrule openings serve as a mold for the lens formation with the end of the fiber being located at the focal distance of the lenslet formed in an on the ferrule. A non-wetting coating can serve to control spreading of the fluid optical material and allow lens radius control as well. The microlenses are hardened after formation.

Abstract: An optical switch uses a fixed mirror cover to reflect optical signals to and from fiber collimators and movable mirrors that are formed on a common substrate.

Abstract: An optical fiber collimator array includes an optical fiber array block and a microlens array substrate. The optical fiber array block includes an angled surface and is configured to receive and retain a plurality of individual optical fibers, which carry optical signals. The microlens array substrate includes a plurality of microlenses integrated along a microlens surface and a sloped surface opposite the microlens surface. The microlens surface is coupled to the angled surface such that the optical signals from the individual optical fibers are each collimated by a different one of the integrated microlenses.

Abstract: A laser surgical apparatus is disclosed in which laser energy can be directed at an angle relative to the longitudinal axis of the probe. The probe includes a reflecting surface directing the laser energy. The reflecting surface is transparent to visible light. In a preferred embodiment, the reflecting surface is on a rod cut at an angle to form a wedge, and a collimator is used to collimate the light beam before it reaches the reflecting surface.

Abstract: The invention relates to an optical arrangement for transmitting short laser pulses in optical fibers (2), especially for injection into a laser microscope, preferably for use in two-photon laser microscopy. The inventive arrangement comprises a short-pulse laser light source (1) and at least one optical fiber (2). An optical device (3) for temporarily modifying the laser pulses is provided between the laser light source (1) and the optical fiber (2). The optical arrangement is provided for compensating an unintentional fiber dispersion and non-linear effects resulting from high energy densities, mainly self-phase modulation. The invention is characterized in that the optical device (3) is configured as a section which is, for the most part, comprised of a transparent , dispersive medium and which is located in the beam path (4) in front of the optical fiber (2) which serves the time extension of the laser pulses (pulse spreading).

Abstract: An optical isolator includes a first optical collimator, an isolated core, a second optical collimator and an outer tube. The first and second collimators and the isolated core are accommodated in the outer tube. The second collimator has a long sleeve which entirely accommodates the isolated core. The isolated core includes a first polarizer, a Faraday rotator crystal, and a second polarizer positioned in sequence within a toroidal magnetic core. An axial length of the toroidal magnetic core is equal to or slightly less than an overall length of the two polarizers and the rotator crystal. The two polarizers and the rotator crystal are sized such that an overall diameter of the isolated core is less than an inner diameter of the long sleeve. The magnetic core is glued within the long sleeve.

Abstract: A filter module includes a first optical fiber collimator, a second optical fiber collimator, and a filter located between the first and second optical fiber collimators. The first optical fiber collimator includes a first optical fiber, a first optical fiber chip for holding the first optical fiber, and a first lens. The second optical fiber collimator includes second optical fibers, a second optical fiber chip for holding the second optical fiber, and a second lens. The filter is located between and coaxial with the first and second lenses. The filter, the first lens, and the second lens form a center piece of the filter module.