WO2009025662A1 - Réduction de l'échauffement d'une lumière non couplée dans des fibres optiques à transmission d'énergie - Google Patents

Réduction de l'échauffement d'une lumière non couplée dans des fibres optiques à transmission d'énergie Download PDF

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Publication number
WO2009025662A1
WO2009025662A1 PCT/US2007/076228 US2007076228W WO2009025662A1 WO 2009025662 A1 WO2009025662 A1 WO 2009025662A1 US 2007076228 W US2007076228 W US 2007076228W WO 2009025662 A1 WO2009025662 A1 WO 2009025662A1
Authority
WO
WIPO (PCT)
Prior art keywords
fiber
adhesive
refractive index
light source
sol gel
Prior art date
Application number
PCT/US2007/076228
Other languages
English (en)
Inventor
Alex Rosiewics
Ninghui Zhu
Michio Matsuki
Original Assignee
Em4, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Em4, Inc. filed Critical Em4, Inc.
Priority to PCT/US2007/076228 priority Critical patent/WO2009025662A1/fr
Publication of WO2009025662A1 publication Critical patent/WO2009025662A1/fr

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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
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • 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
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
    • G02B6/4236—Fixing or mounting methods of the aligned elements
    • G02B6/4239—Adhesive bonding; Encapsulation with polymer material
    • 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
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4296—Coupling light guides with opto-electronic elements coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources

Definitions

  • the inventions relate generally to the use of optical fibers for transmission of power, and more particularly to mounting optical fibers for coupling to light sources.
  • Optical fibers can be used to transmit power.
  • electrical power is first converted into light with a power conversion device, such as a multimode pump chip.
  • the high power light is directed into the fiber at a fiber tip, and then travels down the fiber to a destination, or is coupled into another fiber.
  • the fiber tip is accurately aligned with the light source, and, once aligned, securely held in place.
  • a typical securing technique involves stripping a 10-20mm length of the jacket off the fiber at one end, metallizing the exposed glass of the fiber, inserting the fiber through a mounting tube, and securing the fiber to the mounting tube. The mounting tube is then secured to a mounting block.
  • High-powered optical fibers have been secured to a mounting tube with a metallic solder applied to the metallized surface of the fiber.
  • a metallic solder applied to the metallized surface of the fiber.
  • the deflected light is rapidly absorbed since the metallized surface of the fiber, as well as the solder, do not transmit light.
  • the interface between the fiber and the solder contains a complex web of oxides and other dielectric materials that also absorb light.
  • Modern multimode power-carrying optical fibers typically carry a total power of about 10 watts.
  • the metallic solder is replaced with glass solder or with epoxy.
  • these materials have a refractive index that is similar to that of glass or even a little higher, they refract light out of the fiber, also causing power loss. Oxides within the glass solder are efficient light absorbers, and the result can again be significant localized heating with potentially destructive consequences.
  • the described embodiments reduce the coupling of power from a power- carrying fiber to its surroundings, particularly the mounting means. This reduction is achieved by securing the fiber with its polymer cladding stripped off to its mount with an adhesive that has a refractive index lower than that of the outer glass cladding of the fiber.
  • the invention features a method of mounting an optical fiber for coupling to a light source.
  • the method involves providing a portion of the fiber with its polymer cladding stripped off in a mounting tube, applying an adhesive having a refractive index lower than the refractive index of the fiber core and glass cladding to a junction between the fiber glass cladding and the mounting tube to secure the optical fiber to the mounting tube, and hermetically sealing the mounted fiber and the light source within a module housing.
  • Embodiments include one or more of the following aspects.
  • the adhesive has a refractive index of less than 1.5; the adhesive may comprise sol gel, and may be transmissive of visible light; the adhesive further may have a curing time of less than 30 minutes at room temperature.
  • the sol gel comprises 3-mercapptopropyl-trimethoxysilane and methyltrimethoxysilane.
  • the mounting tube is mounted such that the optical fiber is aligned with the light source.
  • the mounting tube may be mounted on a mounting block connected to the module housing.
  • the fiber core and cladding may comprise glass, in addition to a polymer outer cladding. Prior to placing the fiber inside the mounting tube, a tip portion of the fiber glass cladding may be exposed by stripping off the polymer cladding.
  • the invention features an apparatus with a mounted optical fiber.
  • the apparatus includes an optical fiber having a tip portion where the fiber with its polymer cladding stripped off is exposed; a mounting tube surrounding at least a portion of the tip portion of the optical fiber, the fiber being secured to the mounting tube with an adhesive having a refractive index lower than the refractive index of glass; and a light source that is optically coupled to the light source.
  • Embodiments include one or more of the following aspects.
  • the fiber core is made of glass.
  • the adhesive has a refractive index of less than 1.5; the adhesive curing time is less than 30 minutes at room temperature; the adhesive may be a sol gel adhesive; and the adhesive may be transmissive of light.
  • the mounting tube is mounted so as to align the fiber with the light source.
  • Figure 1 is a side view of a high power multi-mode laser pump module assembly.
  • Figure 2 is an illustration of selected components used to secure a high power optical fiber.
  • Multimode optical fibers typically transmit between one and 10 watts of power as light within an individual fiber, but power transmission may be as high as 100 watts per fiber.
  • the power to be transmitted is normally provided to the fiber as an electrical current traveling along a conducting cable.
  • a high power multimode pump chip converts the incoming electrical energy into optical energy in the form of laser light, which is coupled to an optical fiber.
  • the multimode pump chip, the fiber tip (one end of the fiber), and associated components are all housed within a hermetically sealed module.
  • One source of malfunction in the assemblies that couple electrical signals to optical fibers is leakage of non-coupled energy out of the core of the fiber into the cladding and into other material that is used to adhere the end of the fiber to its mount.
  • the coupling of light to the surrounding material can be drastically reduced by using a material having a lower refractive index than that of the glass fiber.
  • a material having a lower refractive index than that of the glass fiber In this situation, light traveling along the fiber that impinges on the glass/surround boundary is incident from the higher-refractive index side of the junction. If incident at an angle greater than the critical angle (which is typically the case for light traveling along the fiber), the light is internally reflected back into the fiber. Low refractive index surrounding material thus reduces the coupling between the fiber and its surround.
  • the described embodiment uses a sol gel adhesive, referred to herein as sol gel 1612, to secure the optical fiber to the mounting tube.
  • Sol gel 1612 is a colloidal suspension of silicon dioxide that is gelled to form a solid.
  • the sol gel is an effective adhesive, and serves to replace the metallic solder and/or the glass solder or epoxy adhesives used in other systems.
  • the 1612 compound sol gel has a refractive index of 1.38 at a wavelength of 589 nm, significantly below the 1.5 refractive index of glass.
  • Sol gel is also optically transmissive, which means that any light that is coupled into it is not rapidly absorbed and does not cause localized heating.
  • the glass used in glass solder contains oxides that are efficient light absorbers that would cause power from coupled light to be deposited close to the contact surface with the fiber core.
  • a further advantage of sol gel is that it is stable at room temperature, having a long shelf life. It also cures relatively rapidly (15 to 30 minutes) at room temperature. This property enables the assembly process to proceed rapidly. It also removes the need for the high temperatures required to melt and apply solder adhesives. This allows the assembly to be fixed while on the assembly station, avoiding possible internal movements within the assembly during removal from the assembly station.
  • the low-temperature cure also beneficially avoids temperatures that could cause other solders in the module to soften or move, which could result in thermal damage to the polymer cladding of the fiber.
  • the fiber is adhered to the mount with an adhesive having a refractive index of less than 1.5; in another embodiment, the adhesive has a refractive index of less than 1.45; in yet another embodiment, the adhesive has a refractive index of less than 1.4.
  • FIG 1 is an illustration of a high power, hermetically sealed, multimode pump module that incorporates a sol gel adhesive, and that is used to couple optical power into a fiber.
  • Fiber 102 is mounted inside module 104 with fiber tip 106 aligned with multimode pump chip 108 and its carrier 110.
  • Carrier 110 is mounted on submount 112.
  • Fiber 102 is mounted and secured by ferrule 114, which serves as a mounting tube, and is mounted on mounting block 116. Fiber 102 is adhered to ferrule 114 using a sol gel (not shown in Figure 1 ).
  • the fiber then passes through second ferrule 118 that exits sealed module 104 through package ferrule 120.
  • First ferrule 114 and second ferrule 118 preferably comprise metals or metal alloys.
  • Package ferrule 120 is soldered to wall 122 of module 104, and forms a hermetic seal with wall 122.
  • Fiber 102 is hermetically sealed to second ferrule 118 with a glass solder.
  • the purpose of first ferrule 114 is to secure fiber 102 in correct alignment with multimode pump chip 108, while second ferrule 118 surrounds the fiber with a hermetic seal before it exits sealed module 104.
  • Sealed module 104 includes enclosure 124 containing a gettering material (not shown), which removes impurities from within module 104 through porous housing 126.
  • fiber 102 exits second ferrule 118 and, after a short gap, is covered with acrylate fiber jacket 128.
  • the acrylate jacket is a covering that is normally supplied with the optical fiber, but here, the jacket has been stripped off to expose the glass core of fiber 102 to a distance of 18 ⁇ 0.5mm from fiber tip 106.
  • Second ferrule 118 is secured to jacket 128 with notched tube 130, providing strain relief for the fiber gap between second ferrule 118 and jacket 128.
  • the entire assembly from package ferrule 120 to jacket 128 and beyond is covered with protective rubber strain relief boot 132, preferably comprising flame-retardant rubber.
  • Figure 2 is an illustration showing the fiber assembly in more detail.
  • the figure shows the portion of fiber 102 from tip 106 extending about 18mm along the fiber, corresponding to the portion for which fiber 102 has been stripped down to the glass core.
  • the fiber enters first ferrule 114.
  • the fiber is secured to ferrule 114 by sol gel 202, which serves as a low refractive index, highly transmissive adhesive layer.
  • Sol gel 202 is applied to the first ferrule 114, and, through capillary action, wicks along fiber 102, reaching approximately 80-100% along the length of ferrule 114.
  • Fiber 102 exits from back face 204 of ferrule 114, and after a short gap of approximately 2mm, enters second ferrule 118, where it is secured with a hermetic seal provided by glass solder 206. Fiber 102 then exits second ferrule 118, and, after short gap 208, enters jacket 128. Strain relief is provided by notched tube 130, which is secured by epoxy joints 210 to second ferrule 118 at one end and to fiber jacket 128 at the other.
  • Glass solder is used to secure fiber 102 to second ferrule 118 in order to provide a hermetic seal.
  • This joint allows light to leak from the glass cladding into the glass solder adhesive, which causes heating around the hermetic seal. This heating can be tolerated for low power parts in the 1OW range since the heat can be dissipated in the seal vicinity without destabilizing the fiber coupling or compromising the hermetic seal. However, when used with high power modules, such light leakage could cause destructive heating. In such applications it would be desirable to use a low refractive index adhesive, such as sol gel, to provide the required hermetic seal at this joint (as for first ferrule 114) without the light leakage and resulting heat dissipation associated with a glass solder joint.
  • a low refractive index adhesive such as sol gel
  • Typical applications of optical fibers transmitting high power multimode laser light include ordnance initiation, soldering, photodynamic therapy, and marking.
  • the laser light may also be used to provide pump power to other lasers, such as to diode- pumped solid state lasers, or to fiber lasers. Since the packages are fully hermetic, they can be used in challenging environments, such as underwater or in space.

Landscapes

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

Abstract

L'invention concerne un procédé et un appareil pour monter une fibre optique destinée à être couplée à une source lumineuse de grande puissance, la fibre étant fixée sur sa monture avec un adhésif à faible indice de réfraction. L'adhésif à faible indice de réfraction sert à réduire le couplage d'une lumière se déplaçant dans la fibre vers la monture de fibre, en réduisant ainsi un échauffement indésirable potentiellement destructeur de la monture de la fibre. L'adhésif est constitué de préférence d'un sol-gel.
PCT/US2007/076228 2007-08-17 2007-08-17 Réduction de l'échauffement d'une lumière non couplée dans des fibres optiques à transmission d'énergie WO2009025662A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2007/076228 WO2009025662A1 (fr) 2007-08-17 2007-08-17 Réduction de l'échauffement d'une lumière non couplée dans des fibres optiques à transmission d'énergie

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2007/076228 WO2009025662A1 (fr) 2007-08-17 2007-08-17 Réduction de l'échauffement d'une lumière non couplée dans des fibres optiques à transmission d'énergie

Publications (1)

Publication Number Publication Date
WO2009025662A1 true WO2009025662A1 (fr) 2009-02-26

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013235000A (ja) * 2012-05-09 2013-11-21 Boeing Co:The 耐久性を高めたフォトニック結晶センサパッケージング

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5727105A (en) * 1993-12-28 1998-03-10 Sumitomo Osaka Cement Co., Ltd. Package structure for optical element and fibers and composite structure thereof
US6757464B2 (en) * 2001-04-30 2004-06-29 Schott Corporation Use of sol-gel as inorganic adhesive for high stability, hermetic bonding of optical fiber to an alignment plate
US7309175B1 (en) * 2006-07-28 2007-12-18 Em4, Inc. Reducing heating from non-coupled light in power transmitting optical fibers

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5727105A (en) * 1993-12-28 1998-03-10 Sumitomo Osaka Cement Co., Ltd. Package structure for optical element and fibers and composite structure thereof
US6757464B2 (en) * 2001-04-30 2004-06-29 Schott Corporation Use of sol-gel as inorganic adhesive for high stability, hermetic bonding of optical fiber to an alignment plate
US7309175B1 (en) * 2006-07-28 2007-12-18 Em4, Inc. Reducing heating from non-coupled light in power transmitting optical fibers

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013235000A (ja) * 2012-05-09 2013-11-21 Boeing Co:The 耐久性を高めたフォトニック結晶センサパッケージング
EP2662676A3 (fr) * 2012-05-09 2014-01-01 The Boeing Company Conditionnement de capteur ave guide d'onde renforcé
RU2633675C2 (ru) * 2012-05-09 2017-10-16 Зе Боинг Компани Корпусирование фотонно-кристаллических датчиков, предназначенных для экстремальных условий

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