Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/36—Mechanical coupling means
  • G02B6/38—Mechanical coupling means having fibre to fibre mating means
  • G02B6/3807—Dismountable connectors, i.e. comprising plugs
  • G02B6/3869—Mounting ferrules to connector body, i.e. plugs
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends
  • G02B6/325—Optical coupling means having lens focusing means positioned between opposed fibre ends comprising a transparent member, e.g. window, protective plate
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends
  • G02B6/327—Optical coupling means having lens focusing means positioned between opposed fibre ends with angled interfaces to reduce reflections
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/36—Mechanical coupling means
  • G02B6/38—Mechanical coupling means having fibre to fibre mating means
  • G02B6/3807—Dismountable connectors, i.e. comprising plugs
  • G02B6/3833—Details of mounting fibres in ferrules; Assembly methods; Manufacture
  • G02B6/3855—Details of mounting fibres in ferrules; Assembly methods; Manufacture characterised by the method of anchoring or fixing the fibre within the ferrule
  • G02B6/3861—Adhesive bonding

Definitions

• the present invention concerns a method for connecting a first optic component to a second optic component in order to achieve an optical connection between them.
• the present invention also relates to an optic device produced using such a method and a computer program for making a computer or processor execute at least one of the steps of the method.
• An optic device usually comprises at least two optic components that have to be optically connected.
• a TX-module i.e. transmitter module
• a TX-package that is connected to a fibre optic in order to transmit light away from the TX-package to one or more external locations.
• a TX- package comprises a laser diode contained in a hermetically- sealed housing together with the necessary electric circuitry and a window through which light from the laser diode exits the TX- package.
• the TX-package also comprises a receptacle holder.
• a receptacle is inserted into the receptacle holder.
• a receptacle is a structure that supports a fibre optic or waveguide, for example by means of a ferrule i.e. a cylindrical sheath provided with a central channel serving to receive the stripped end portion of a fibre optic so as to hold it accurately in alignment with another optic component.
• the receptacle or the TX-module may further comprise a lens, concave mirror or other means to focus light passing through the window of the TX-package into the fibre optic.
• the end of the fibre optic inside the receptacle has to be accurately aligned with the laser diode of the TX-package in order to obtain the optimum optimal transmission of light from the laser diode into the fibre optic with minimum optical loss.
• the receptacle is secured to the receptacle holder so as to fix the position of the fibre optic relative to the TX-package. This is usually done by welding the receptacle to the receptacle holder.
• the external surface of the receptacle often comprises a different material to the receptacle holder.
• the receptacle may be made of stainless steel or passivated copper, for example, while the receptacle holder may be made of kovar or ceramic; a vacuum melted, iron-nickel-cobalt, low expansion alloy. Since the adhesive and consequently the optic components are subjected to heat during the adhesive curing process, the receptacle and the receptacle holder undergo different dimensional changes due to their different coefficients of thermal expansion.
• the receptacle As the adhesive and consequently the receptacle and receptacle holder cool down to ambient temperature the receptacle, having a higher coefficient of thermal expansion than the receptacle holder, decreases in length more than the receptacle holder. This gives rise to stresses in the adhesive as it is either tensed or compressed at the edges of the adhesive joint. These stresses can lead to the initiation of cracks at the edges of the adhesive joint which may propagate through the adhesive joint causing the adhesive to detach from the surfaces of the receptacle and/or receptacle holder, mainly from the receptacle holder.
• the presence of cracks in the adhesive joint can lead to misalignment of the laser diode with the fibre optic resulting in poor optic transmission and decreased the power output of the TX-module.
• the mechanical properties of the adhesive joint can also be negatively influenced if the adhesive absorbs moisture from its environment as this can give rise to moisture-induced stresses in the adhesive joint. Achieving and maintaining an accurate alignment between optic components in an optic device can therefore be a difficult and time consuming process.
• Adhesive bonding is used almost exclusively to connect multi- mode fibre optics to other optic components. Connecting single- mode fibre optics to other optic components requires higher precision than that which is required when connecting multi- mode fibre optics.
• Single-mode fibre optics have much smaller core diameters (about 5 ⁇ m) than multi-mode fibre optics (at least 50 ⁇ m) since in single-mode only a fundamental mode is propagated, a mode being one of the discrete number of light waves that can propagate in a fibre while maintaining total internal reflection, while multi-mode allows multiple light waves to be propagated.
• the increased precision required for maintaining the alignment of a single-mode fibre optic makes adhesive joints unsuitable for connecting single-mode fibre optics to other optic components using an adhesive bonding method according to the prior art.
• the object of the present invention is to provide a method for connecting a first optic component to a second optic component in order to achieve an optical connection between them, whereby the alignment of the first and the second optic components is maintained after they have been secured to one another.
• the object is fulfilled using a method comprising the steps given in claim 1 , namely a method comprising the steps of providing the first optic component with a receptacle and providing the second optic component with a receptacle holder.
• the receptacle is brought into contact with the receptacle holder by inserting the receptacle into the receptacle holder or fitting the receptacle onto the receptacle holder for example.
• the receptacle is aligned with the receptacle holder and an adhesive joint is formed between the surface of the receptacle and the surface of the receptacle holder when the desired alignment has been obtained.
• the method also comprises the step of at least partly surrounding the receptacle and the receptacle holder with a sleeve, in the form of a tube or a half tube for example, and filling the sleeve with an adhesive in order to form an adhesive joint between the overlapping surfaces of the receptacle and the receptacle holder and also between the receptacle-receptacle holder-connection and the sleeve.
• This allows the adhesive to expand and contract around the surfaces of the receptacle and receptacle holder which are completely embedded in the adhesive without cracking or detaching from the surfaces that are adhered together.
• optical components is intended to mean any components between which an optical connection is to be established, for example the optic component can comprise an optic energy source, such as a laser diode, an optic energy detector, such as a photodiode or optic energy transmission means, such as a fibre optic or even just a channel along which an optic signal is to be transmitted.
• the method is may be used to connect a laser diode one or more pieces of test equipment, such as an optical power meter, or to connect one fibre optic to one or more fibre optics for example.
• the method comprises the step of sealing the sleeve to form a closed cavity to contain the adhesive prior to filling the sleeve with adhesive.
• the method comprises the step of pushing the receptacle up against sealing means, such as a sealing ring, located in front of the receptacle in order to seal the cavity.
• the sleeve is arranged to be movable so as to facilitate alignment of the receptacle with the receptacle holder prior to forming the adhesive joint.
• the position of the receptacle and/or the receptacle holder is adjusted after the sleeve has been filled with adhesive if, for example, the receptacle and/or receptacle holder are moved so as to facilitate the step of filling the sleeve with adhesive. After the sleeve has been filled with adhesive the receptacle and/or receptacle holder are moved back into the correct alignment position before the adhesive is cured.
• the method comprises the step of providing the surface of the receptacle and/or the surface of the receptacle holder with at least one opening that allows adhesive to pass through the surface(s) of the receptacle and/or the receptacle holder so that more adhesive can be accommodated in the adhesive joint between the receptacle, the receptacle holder and the sleeve.
• said surface(s) is/are provided with at least one finger, slit or hole.
• the surface of the receptacle and/or the surface of the receptacle holder is provided with a plurality of fingers, such as 6 or 12 fingers, optionally uniformly distributed around the receptacle and/or receptacle holder in the area in which the adhesive bond is to be formed. Since the fingers are more flexible than a solid pipe, they can move more readily to facilitate the movement of the adhesive as it cools. It has been found that using a surface comprising 12 fingers provides a more rigid adhesive bond than when using 6 fingers.
• At least part of the surface of the receptacle and/or at least part of the surface of the receptacle holder is/are roughened, by means of a physical or chemical process, in order to increase the surface area for adhesion.
• the surface comprises metal, for example, which is roughened, by spark machining or by providing the surface with a thread for example, prior to forming an adhesive joint so as to form an improved adhesive joint.
• said plurality of fingers is spark machined.
• the adhesive comprises at least one of the following: means to reinforce the adhesive joint, means to minimise mechanical and moisture- induced stresses within the adhesive joint and/or means to decrease the coefficient of thermal expansion of the adhesive.
• the adhesive comprises fibreglass. Such a filled adhesive absorbs about three times less moisture than an unfilled or "opaque" adhesive and decreases the linear coefficient of thermal expansion by a factor of about two to five.
• the receptacle comprises a single-mode fibre optic or a multi-mode fibre optic.
• the inventive method ensures that the receptacle and receptacle holder maintain their alignment position after they have been secured, the method is suitable for use with single- mode fibre optics thus expanding the field of application of the adhesive joint forming methods according to the state of the art.
• the present invention also concerns a sleeve for use in a method according to any of the above-mentioned embodiments.
• the sleeve comprises sealing means formed integrally with the sleeve as a single unit.
• the sleeve and sealing means are provided as separate components.
• the sleeve comprises at least one gas outlet to ventilate gas from the sleeve as it is filled with adhesive.
• the gas outlet can be provided in the body of the sleeve and/or in said sealing means which are either integrally formed with the sleeve or formed as a separate component to the sleeve.
• the sleeve comprises material that is transparent to a particular type of radiation such as ultraviolet, infrared or visible to facilitate curing of the adhesive.
• the sleeve comprises polytetrafluoroethylene (PTFE) or a flexible material.
• the present invention also concerns an optic component for use in a method according to any of the above-mentioned embodiments.
• the optic component comprises a receptacle or a receptacle holder having a surface comprising at least one finger, slit or hole.
• the optic component comprises a receptacle or a receptacle holder having a surface comprising a plurality of fingers, such as 6 or 12 fingers, optionally uniformly distributed around the end of said receptacle or receptacle holder.
• the present invention also relates to an optic device, such as an optic transceiver or transponder, comprising an optic component having at least one receptacle and an optic component having at least one receptacle holder where said at least one receptacle and said at least one receptacle holder are connected using a method according to any of the above-mentioned embodiments.
• an optic device such as an optic transceiver or transponder
• the present invention also concerns a computer program containing computer program code means for making a computer or processor execute at least one of the steps of the inventive method and such a computer program stored by means of a computer-readable medium.
• the computer program is used to monitor and/or control the alignment of optic components and the adhesive-dispensing and -curing process for example.
• Fig. 1 shows the receptacle holder of a first optic component
• Fig. 2 shows the receptacle of a second optic component
• Fig. 3 shows the misalignment of a receptacle inside a receptacle holder which can occur using a method according to the prior art
• Figs. 4-9 show the steps of a method according to an embodiment of the present invention
• Figs. 10-14 show the steps of filling a sleeve with adhesive according to an embodiment of the present invention.
• Fig. 15 shows the surface of a receptacle holder according to embodiments of the present invention.
• the following description and drawings are not intended to limit the present invention to the embodiment disclosed.
• the embodiment disclosed merely exemplifies the principles of the present invention.
• Figure 1 shows part of a first optic component, namely a TX- package, having a receptacle holder 1 .
• the receptacle holder 1 comprises a window 2 through which light from a laser diode contained inside a TX-package passes, in the direction of the arrows, for transmission out of the TX-package.
• the two optic components could be an RX-package (i.e. a receiver package) and a fibre optic where light from the fibre optic is conveyed towards the RX-package.
• Figure 2 shows a receptacle 3 comprising a fibre optic 4 contained inside a ferrule 5.
• a lens 6 focuses light passing through the window 2 of the receptacle holder 1 into the fibre optic 4.
• the receptacle 3 is formed as a male connector part and the receptacle holder 1 is formed as a female connector part.
• the receptacle could however be formed as a female connector part and the receptacle holder as the male connector part whereby the receptacle holder would be inserted into the receptacle and the surface of the receptacle would be radially outside the surface of the receptacle holder.
• Figure 3 shows a receptacle 3 that has been secured to a receptacle holder 1 having the form of a solid cylindrical tube.
• the space between the outer surface of the receptacle 3 and the inner surface of the receptacle holder 1 is filled with adhesive.
• the adhesive 7 detaches from the receptacle holder 1 giving rise to un- symmetric gaps 8 in the adhesive joint between the receptacle holder 1 and the receptacle 3.
• the receptacle 3 becomes misaligned in the receptacle holder 1 and is therefore in the wrong position and at the wrong angle for optimum light transmission from the TX-package into the fibre optic 4.
• Figures 4-9 shows the steps of a method according to an embodiment of the invention.
• a receptacle 3 is inserted into a receptacle holder 3.
• the laser diode of the TX-package is powered during the alignment process while the end of the fibre optic 4 is aligned with a light intensity meter to measure the intensity of the laser beam passing through the fibre optic 4.
• the light intensity meter will show a maximum value when the receptacle 3 and the receptacle holder 1 are optimally aligned.
• the position of the receptacle with respect to the receptacle holder is optimised to within a desired standard deviation using a micromanipulator, i.e. both its planar position (typically to within about ⁇ 10-20 ⁇ m) and its angular position (typically to within about 0.03°).
• the insertion step can be initiated by pressing a key on a keyboard.
• the computer subsequently monitors the optical transmission between the optic components and controls the movement of the receptacle 3 with respect to the receptacle holder 1 to optimize their position relative to one another.
• Figure 4 shows a sleeve 9, made of transparent PTFE, for example, one end of which is mounted on the receptacle holder 1 prior to insertion of the receptacle 3 into the receptacle holder. Once the receptacle 3 has been inserted the other end of the sleeve 9 is mounted on the receptacle.
• Figures 5 and 6 show that the movable sleeve 9 is capable of occupying different positions and angles, so as to facilitate alignment of the receptacle 3 with the receptacle holder 1.
• the sleeve 9 is sealed by means of two sealing rings 10a and a sealing washer 10b located in front of the receptacle 3 so as to form a cavity 1 1 for containing adhesive.
• the receptacle 3 is pushed up against the sealing washer 10b in order to seal the cavity 1 1 .
• the sleeve 9 and the sealing rings 10a are formed as a single unit.
• Figure 8 shows that a needle 12 is then inserted through an adhesive inlet 13 in the sleeve 9 to fill the cavity 1 1 with adhesive.
• the needle 12 is removed and the receptacle 3 is moved back to its correct alignment position away from the sealing washer 10b as shown in figure 9.
• the adhesive is then cured by irradiating the contents of the sleeve 9 with ultraviolet light for example so as to maintain the correct alignment position.
• an air- cured adhesive could be used or an IR-cured adhesive if the optic components can withstand the thermal movement caused by the curing process.
• Figure 10 shows the receptacle 3, receptacle holder 1 and sleeve 9 in cross section.
• the sleeve 9 comprises gas outlets 15 through which gas contained in the sleeve is ventilated out of the sleeve 9 as it is filled with adhesive.
• a gas outlet may also be provided in the sealing rings 10a if necessary. The provision of a gas outlet may not be necessary if the sealing means do not provide a completely gas-tight seal.
• the receptacle 3, receptacle holder 1 and sleeve 9 are shown as having a circular cross section, these components can however be of any cross sectional shape.
• the receptacle 1 surface comprises a solid, circular tube.
• the surface of the receptacle holder 3 comprises fingers 14 in-between which an adhesive can pass.
• Figure 1 1 shows the step of inserting a needle 12 through the adhesive inlet 13 and filling the cavity 1 1 between the receptacle 3 and receptacle holder 1 with adhesive 7.
• the adhesive 7 can be an epoxy, acrylate, urethane, silicone or any commercially available UV-/visible light curing optical adhesive.
• the adhesive passes in-between the fingers 14 of the receptacle and fills the cavity 1 1 between the receptacle 3 and receptacle holder 1 and the openings between the fingers 14.
• the adhesive 7 also fills the cavity 1 1 between the outside of the receptacle holder 1 and the sleeve 9.
• the pressure build-up inside the cavity eventually causes adhesive 7 to be forced out of the sides of the adhesive inlet 13 as shown in figure 12.
• the needle 12 is then removed as shown in figure 13 and the adhesive is cured by irradiating the contents of the sleeve with UV radiation for example.
• the sleeve 9 is then removed as shown in figure 14 leaving an adhesive joint between the receptacle 3 and the receptacle holder 1 and a layer of adhesive around the receptacle holder 1 whereby the adhesive layer completely encapsulates the receptacle- receptacle holder connection.
• Figure 15 shows part of the surface of four different receptacle holders 1 that comprise a plurality of fingers 14, one or more slits 16 or one or more holes 17 in order to allow adhesive 7 to pass through and encapsulate the surface of the receptacle holder 1.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Optical Couplings Of Light Guides (AREA)

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• 2004
  • 2004-05-10 WO PCT/SE2004/000716 patent/WO2005109061A1/en active Application Filing
  • 2004-05-10 CN CNA2004800432743A patent/CN101019056A/zh active Pending
  • 2004-05-10 EP EP04732065A patent/EP1779164A1/de not_active Withdrawn

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