EP0248066A1 - Coupleur a concatenation - Google Patents

Coupleur a concatenation

Info

Publication number
EP0248066A1
EP0248066A1 EP19870900183 EP87900183A EP0248066A1 EP 0248066 A1 EP0248066 A1 EP 0248066A1 EP 19870900183 EP19870900183 EP 19870900183 EP 87900183 A EP87900183 A EP 87900183A EP 0248066 A1 EP0248066 A1 EP 0248066A1
Authority
EP
European Patent Office
Prior art keywords
fibre
filter
tapered
waveguide
coupler
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP19870900183
Other languages
German (de)
English (en)
Inventor
George Antony Georgiou
Anthony Christos Boucouvalas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co PLC
Original Assignee
General Electric Co PLC
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 General Electric Co PLC filed Critical General Electric Co PLC
Publication of EP0248066A1 publication Critical patent/EP0248066A1/fr
Withdrawn legal-status Critical Current

Links

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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
    • G02B6/03638—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 3 layers only
    • G02B6/03644—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 3 layers only arranged - + -
    • 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
    • G02B6/255—Splicing of light guides, e.g. by fusion or bonding
    • G02B6/2552—Splicing of light guides, e.g. by fusion or bonding reshaping or reforming of light guides for coupling using thermal heating, e.g. tapering, forming of a lens on light guide ends
    • 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
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2821—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals
    • G02B6/2835—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals formed or shaped by thermal treatment, e.g. couplers
    • 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
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29331—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by evanescent wave coupling
    • G02B6/29332—Wavelength selective couplers, i.e. based on evanescent coupling between light guides, e.g. fused fibre couplers with transverse coupling between fibres having different propagation constant wavelength dependency
    • 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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03605—Highest refractive index not on central axis
    • G02B6/03611—Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding

Definitions

  • the present invention concerns coaxial waveguide optical fibres.
  • a coaxial coupler can be produced from optical fibres of the type having a rod waveguide surrounded by a tubular waveguide by elongating a portion of the optical fibre to reduce the transverse dimensions of the portion. This is done by mounting the fibre in a driven clamping arrangement, launching light of a predetermined wavelength at one end of the fibre and detecting the intensity of the transmitted light at the other end whilst the clamped portion of the fibre is simultaneously elongated and heated.
  • the intensity of the detected radiation varies cyclically as the fibre is elongated and the procedure is stopped after a number of oscillations selected to provide the appropriate transmission characteristics.
  • the present invention has for an object to utilise this technique to manufacture filters with output responses which are tailored to specific requirements such as comb filters. Accordingly from one aspect the present invention consists in a filter comprising a coaxial optical fibre having at least two discrete tapered sections, caused by elongation of the fibre at two separate portions, the two sections having been produced in such a manner that the fibre has specified pass-band characteristics.
  • the invention consists in a process of producing a filter from a coaxial optical fibre including the steps of elongating at least two portions of the fibre to provide two tapered sections.
  • Figure 2 shows a diagrammatic representation of a rig for tapering optical fibres
  • Figure 3 shows a plot of the transmitted power against the extension of the fibre
  • Figure 4 is a diagram representing a section through a tapered portion of the waveguide for explaining the operation of the coupler
  • Figure 5 is a graph showing transmitted bandwidth against elongation for a single taper.
  • Figure 6 is a graph of the pass-band of a fibre which has been subjected to considerable elongation
  • Figure 7 is a graph showing the pass-band of a fibre tapered in accordance with the invention.
  • Figure 1 shows an optical fibre which defines two waveguides, a central rod waveguide which is defined by the core 2 of the fibre, and a coaxial tubular waveguide 4.
  • the refractive indices n. , nl , of the rod and tubular waveguides are elevated relative to the refractive indices n ⁇ , n-, of the intermediate cladding layer 6 and the outer coating layer 8.
  • the dimensions and refractive indices n of the rod waveguide and the tubular waveguide are selected such that each will support at least one transmission mode at the design wavelength which may be, say, 1.33 or 1.55 micrometres.
  • Plots B and in Figure 1 show other typical refractive index profiles for optical fibre coaxial couplers.
  • the apparatus of Figure 2 comprises a laser light source ⁇ 5 producing radiation at the designwavelength. This radiation is passed through a lens 14 to focus it onto the cleaved face of the core 2 of the fibre 10 so that light is propagated along the core of the fibre. Normally the fibre will be surrounded by an acrylate jacket which will strip any modes which start to propagate in the tubular waveguide. If such a jacket is not provided the fibre may pass through a bath of index matching fluid which will prevent light propagation along the tubular waveguide.
  • the fibre 10 is clamped at two spaced points along its length by clamps 16 and 18. Each clamp is provided with a motorised driver 20, 22 to enable the clamps to be pulled away from each other to taper the portion of the fibre between them.
  • the clamps may be positioned vertically one above the other so that gravity can assist the tapering process.
  • An oxy- butane flame 23 (2-25 mm in diameter) is used to heat the fibre while the taper between the clamps is elongated.
  • the end of the fibre 10 is coupled to a power detector 24 which is connected to a chart recorder. If this is not the case then the power detection is provided by a microscope coupled to a vidicon camera.
  • the power detector or microscope is focused so as to detect the power propagated along the core 2 of the optical fibre 10. If the acrylate jacket does not strip modes propagating in the tubular waveguide, a further bath of index matching fluid is provided after clamp 18 to avoid light propagatin in the tubular waveguide affecting the power detector.
  • a typical plot produced on the chart recorder 26 is shown in Figure 3. The plot comprises a level section where a constant amount of power is being received. This is indicative of the power launched from the laser into the core being propagated along the core with little or no coupling of power into the tubular waveguide 4. After this level section 30 " the received power oscillates increasingl rapidly between a series of minima 32, 34, 36 where little power is being received through the core.
  • minima correspond to extensions of the fibre at which the tapered portion of the fibre 10 between the clamps 16, is so dimensioned that there is complete energy exchange- between the two waveguides.
  • the plot produced in Figure 3 has been shown for a considerable extension of the fibre between the clamps.
  • the drive to the clamps is stopped when the recorder reaches one of the minima 34, 36, or maxima 37, 38, 39 or anywhere in between depending on the application. If it is desired to produce a coupler which couples a desired proportion of the energy from one waveguide to the other, the taper can be stopped at other than one of the minima in order to produce the required ratio of energy transfer berween the waveguides.
  • the operation of the coaxial coupler produced by this tapered waveguide can be considered as analogous to a three section coupler where the mismatch (£J9 ) between the propagation constants in each section alternates in sign.
  • the three sections of the present coupler can be identified as shown in Figure 4.
  • the sign of the differ ⁇ ence between the propagation constants of the two waveguides changes between the outer portions of the taper and the central, thinnest, portion of the tapered portion.
  • a description of the mathematics of three section A ⁇ > couplers can be found in an article entitled "Switched Directional Couplers with Alternating £& " by Herwig Kogelnik and Ronald V. Schmidt in IEEE Journal of Quantum Electronics, Volume QE-12, No. 7, July 1976.
  • This article relates to couplers in which the mismatch is produced by applying electrodes with alternating potential differences across them to the coupled waveguides.
  • the dimensional variation of the tapered portion can be considered to produce a similar effect.
  • Figure 6 where by subjecting a fibre to elongation for 20 power oscillations a pass bandwidth of 35 nm has been achieved.
  • the pass bandwidth characteristics are not suitable for a spike or comb filter.
  • the required characteristics can be achieved by concatenating together two or more tapered coaxial couplers. -
  • the spectral response of a tapered coaxial coupler is approximately sinusoidal with wavelengths of period ⁇ «
  • the wave- length response of several concatenated coaxial couplers can be represented approximately as
  • the wavelength response is the product of the wavelength responses of the individual couplers, for fixed ...
  • An indication of the desired wavelength response of the individual couplers can be obtained from the above equation
  • the tapering of the fibres is made in a manner identical to that previously described.
  • the fibre is fixed onto a motorised jig, then tapered whilst an oxy-butane flame, for example, is applied.
  • the output power is plotted on a chart recorder.
  • the first tapering- is stopped after two oscillations and the second taper is made a few centimeters from the first one in the same manner.
  • the second tapering is stopped when eight oscillations have occurred in the output power i.e. the bandwidth of the second taper is half that of the first.
  • Figure 7 shows the wavelength response when two typical tapers have been made in the manner described above in a single fibre. Naturally differing degrees of tapering can be used, and more than two sets of taper can be imparted to a single fibre.
  • the passband is narrower than the passband of the individual tapers there the passband is 70 nm as opposed to a passband of 100 nm for the second individual coaxial taper (as can be derived from the graph of Figure 5) .
  • a narrow spike or comb filter like wavelength response can be obtained which is narrower than the individual taper response.
  • the filter is of low loss, all fibre.
  • Filters of the type produced in accordance with the invention can be used in a number of different applications. For example, in a wavelength drop-off filter in a wavelength division, multiplexed communication link ; or to separate a single line from a multilongitudinal mode laser.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

Filtre dont des caractéristiques du signal de sortie sont adaptées aux besoins de l'utilisateur, utilisable par exemple en tant que filtre de bande à peigne, fabriqué en produisant deux ou plusieurs parties biconiques dans une fibre optique. La fabrication est contrôlée de manière que les coupleurs à concaténation résultants présentent les caractéristiques spécifiées de bande passante.
EP19870900183 1985-12-04 1986-12-04 Coupleur a concatenation Withdrawn EP0248066A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8529861A GB8529861D0 (en) 1985-12-04 1985-12-04 Concatenated coupler
GB8529861 1985-12-04

Publications (1)

Publication Number Publication Date
EP0248066A1 true EP0248066A1 (fr) 1987-12-09

Family

ID=10589230

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870900183 Withdrawn EP0248066A1 (fr) 1985-12-04 1986-12-04 Coupleur a concatenation

Country Status (3)

Country Link
EP (1) EP0248066A1 (fr)
GB (2) GB8529861D0 (fr)
WO (1) WO1987003701A1 (fr)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5177803A (en) * 1991-04-29 1993-01-05 Corning Incorporated Coaxial optical fiber coupler transmitter-receiver apparatus and method of making same
FR2681438B1 (fr) * 1991-09-16 1994-12-09 Alcatel Nv Procede pour limiter les pertes de couplage entre une fibre optique monomode et un systeme optique presentant respectivement des diametres de mode differents.
US5473714A (en) * 1994-04-29 1995-12-05 At&T Corp. Optical fiber system using tapered fiber devices
US5479546A (en) * 1994-05-16 1995-12-26 Litton Systems, Inc. Optimized non-linear effect tapered optical fiber interferometer/switch device
GB9803275D0 (en) 1998-02-16 1998-04-08 Univ Southampton Optical fibre filters
GB9803709D0 (en) * 1998-02-20 1998-04-15 Univ Southampton Polarisation insensitive transmissive fibre devices
KR20010071667A (ko) * 1998-06-29 2001-07-31 알프레드 엘. 미첼슨 모놀리식 동축형 장치
US6362916B2 (en) * 1998-09-25 2002-03-26 Fiver Laboratories All fiber gain flattening optical filter
CA2266195C (fr) 1999-03-19 2004-12-21 Itf Optical Technologies Inc.-Technologies Optiques Itf Inc. Filtres d'epuration optique et methode de fabrication
US6459526B1 (en) 1999-08-09 2002-10-01 Corning Incorporated L band amplifier with distributed filtering

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1494535A (en) * 1976-10-26 1977-12-07 Post Office Dielectric optical waveguides

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8703701A1 *

Also Published As

Publication number Publication date
GB8529861D0 (en) 1986-01-15
WO1987003701A1 (fr) 1987-06-18
GB2183866A (en) 1987-06-10
GB2183866B (en) 1989-10-04
GB8629036D0 (en) 1987-01-14

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Inventor name: BOUCOUVALAS, ANTHONY, CHRISTOS

Inventor name: GEORGIOU, GEORGE, ANTONY