FR2575557A1 - DIGITAL OPENING TRANSFORMER - Google Patents

Abstract

DIGITAL OPENING TRANSFORMER DEVICE INCLUDING A CORE 7, A CLADDING LAYER 9 SURROUNDING THE SAID CORE, THE SAID CORE AND THE SAID SHELL FORMING AN ELONGATED WAVE GUIDING STRUCTURE WITH TWO OPPOSED EXTREME SURFACES 6, 10 AND A CONFIGURATION ONE OF SAID EXTREME SURFACES, LONGITUDINALLY TO THE SAID STRUCTURE, AT LEAST ALONG A LARGE PORTION OF THE LATTER.

Description

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  The present invention relates to optical fibers and to our-

  with the aim of reducing the loss due to the lack of adaptation of the digital openings during the assembly of fibers having

souls of different diameter.

  The ability of an optical fiber to collect light is called the "digital aperture" of the fiber. In index jump fibers, the numerical aperture is expressed as follows: numerical aperture = F nn -2 o n1 = the refractive index of the fiber core and n2 'the refractive index of the sheath of the fiber or peripheral medium

  For gradient index fibers, the equation of the open-

  digital ture is more complex and is not indicated in the pre-

feels document.

  Plus the difference between the refractive index of the fiber

  and desa sheath or its peripheral medium is important, the more the

  digital re of fiber is great. Since many

  light-emitting fibers emit in a wide variety of years

  gles, the fibers having a large numerical aperture therefore collect a greater part of this light. Likewise, we will

  preferably use large diameter fibers if the light source

  is important compared to the fiber.

  It is possible to reduce the angular distribution of transmission power by reducing the total digital aperture of the emission optics, for example, by using a fiber with reduced digital aperture. A large area receiver can be obtained using a large area fiber core having an opening

digital is also important.

  In some fiber optic systems, it has been found

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  that by choosing an emission optic having a nu-

  sufficiently low fiber meric, the angular distribution of transmission power could be reduced at will. To avoid losses, it is essential that, throughout the rest of the system, the digital apertures are at least as large as the effective digital emission aperture. If the digital openings of the rest

  of the system are lower than that of the transmitting device,

  then serve a loss which is proportional to the ratio of the squares of the numerical apertures. In conventional fiber optic systems, it is therefore important that all digital apertures

  are adapted to each other to avoid unnecessary losses

  the. In general, the use of a large fiber receiver

  surface does not allow bidirectional operation of a system.

  If the 'forward' direction of the system is such that radiation is emitted by the system through a 'standard' digital aperture and received by a larger area receiver, operation in the 'reverse' direction of the system would use the most large area as an emitting device, which would result in a loss of light

  going from a large digital aperture to a small digital aperture

  risk. In general, the numerical aperture of a fiber increases with

  sure that the size and the surface of his soul increase. The exploita-

  bidirectional tion of such a system using both the direc-

  'forward' and 'reverse' is made impossible due to losses

  due to the lack of adaptation of digital surfaces and openings

  ques. These losses would be mainly caused in the direction

  "reverse" tion when passing a fiber with large numerical aperture

  than a large area to a fiber with a small numerical aperture and a small area. The losses due to the lack of adaptation of the surfaces are proportional to the ratio of the squares of the radii of the souls!

  The present invention therefore aims to eliminate the in-

  specific to the known devices.

  The present invention aims, in particular, to provide a device making it possible to reduce the digital aperture of a fiber

  emitting light in order to adapt it to that of a receiving device

light.

  The present invention also aims to reduce the

  angular distribution of transmission power while retaining or

  digital system of the basic system.

  The present invention also aims to provide a digital aperture transformer having a large surface reception fiber which can be used without modifying

  the digital opening of the basic system.

  The present invention also aims to adapt sensi-

  Loosely to one another the diameters of the cores of two dissimilar fibers

  blables with souls of different diameters.

  In accordance with the aims indicated above and with others which will appear subsequently, the present invention resides in particular in an arrangement making it possible to adapt the digital aperture of a

  waveguiding structure emitting light to that of a receptor

optical waveguide tor.

  The various objects and characteristics of the invention are-

  will now be detailed in the description which follows, made to

  by way of nonlimiting example, referring to the appended figure

  which represents, in schematic form, the arrangement of transforma-

  digital apertor according to the present invention.

  The figure shows an open transformer element

  digital re 1 consisting of an optical waveguiding structure which comprises a core 7 and at least one cladding layer 8. The figure also shows another optical waveguiding structure 2, comprising a central core 4 and at minus a cladding layer, and another optical guide structure 11. The structure 3 is conical over a large portion 9 of its length, in the direction of an end surface forming an interface 6

  with an extreme surface of the structure 2. The structure 3 is coni-

  so that its outside diameter at the interface 6, including its core 7 and its sheath 8, is substantially equal to the diameter of the core 4 of the structure 2. The conical portion 9 of the structure 3 is

called cornet.

  The reference numeral 10 designates an interface between

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  the digital aperture transformer element 1 and the structure 11. This structure 11 may be a light receiving device, such as a light detector or a lens. The structure 11 can also be placed at a certain distance from the extreme surface of the structure 3, so that before reaching the structure 11, the light emitted from the extreme surface of the structure 3

  is transmitted through a predetermined area of free space.

  In one mode of use of the digital aperture transformer element 1, the optical waveguiding structure 2

  is an optical fiber which, together with the digital aperture transformer

  that 1 to which it is connected, forms a transmitter making it possible to transmit the light in the waveguiding structure 11 which then takes the place of a light receiving device. The configuration of the conical zone 9 allows the light to propagate along the structure 3 from the fiber 2 in the following manner: The light which

  passes through the core 4 of the light-emitting fiber 2 directly

  tion of the structure 3 reaches the interface 6. It crosses the inter-

  face 6 and is transported both by the core 7 and by the sheath 8 of the structure 3. The angle of the c8ne 9 is provided so that the portion of light passing through the sheath 8, in sheath mode, penetrates into the core 7 and continues to propagate in the structure 3 along the core 7, in core mode. The inclination of the angle at which the light is

  reflected along the conical portion 9 decreases as the light

  mière progresses from the narrow portion to the broad portion of the zo-

  not conical. Consequently, the angles of incidence and reflection increase. Likewise, the angles formed by the path of the light

  incident and the reflected light path with a perpetual line

  diculaire at interface 6 decrease. There is therefore a reduction in digital openness. There may be a loss of light when

  level of the interface, due to the lack of adaptation of the profile al-

pha, but it remains limited.

  This arrangement makes it possible to transform a fiber transmitter

  given, with a predetermined numerical aperture, in one-emit-

  smaller digital aperture, without modifying the aperture

  meric of the transmission system or the reception system. In

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  this arrangement, the outside diameter of the structure 11 at

  the interface 10 can be identical or superior to that of the structure

ture 3 at interface 10.

  While the digital aperture transformer arrangement

  rique according to the present invention has been described above with reference to structure 2 and structure 3, serving as a transmitter

  of light, as well as of structure 11, serving as a light receptor

  miere, the same arrangement described above can be used in sense

  reverse, that is to say that the structure 11 constitutes the emitter of

  matter and structures 2 and 3 the light receptor. This utility

sation will now be described.

  With reference to the figure, the waveguiding structure 3 comprises the conical end part 9 which is directed towards the core 4 of the receiving structure 2. Again, the outside diameter of the conical area of the structure 3, at the interface 6 comprising the core 7 and the sheath 8, is substantially identical to the diameter of the core 4 of the structure 2 at the interface 6. In the measurement

  o the core 7 of the structure 3 is smaller than the core 4 of the structure

  ture 2, almost all of the core light is sent to the core 4. If a light is transmitted along the conical zone in the sheath 8, it is also sent to the core 4. Since the light then propagates in the cone from the widest end to the narrowest end, the angles of incidence and reflection

  light propagating along the core / sheath interface re-

  duide. Likewise, the angles formed by the incident light and the

  reflected light with a line perpendicular to the interface 6 aug-

  lie. The digital opening of the transmission fiber increases

  so as we approach interface 6.

  When the light travels in this direction, it is necessary that the transverse diameters of the optical waveguiding structures 2 and 3 at the interface 6 are substantially identical. It is therefore possible to use a large area receiver without modifying the digital aperture of the reception system or

of the transmission system.

  Interface 10 has been shown and described as being

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  killed between element 1 and device 11. However, the transforma-

  digital aperture may also be provided in the ex-

  device 11, which removes the area

interface 10.

  During the transmission of light between two fibers in

  known systems, it was necessary to use pre-

  sensing the same numerical aperture or, in general, the core diameter of the transmitting fiber had to be smaller than that of the receiving fiber so that no loss of light occurred at the level

  of their interface. The arrangement according to the present invention pre-

  therefore feels an advantage, namely that it adapts to each other the

  digital fiber grooves and / or fiber core diameters to

  their interface, without requiring any modification of the system or

  laughing at noticeable loss of light or signal. Likewise, the exploita-

  bidirectional tion was not possible when the fibers used had different digital apertures. In this

  case, if almost all of the light from an optical transmitter

  that was sent, in the forward direction, in a receiver fiber to

  greatest digital aperture, it was happening, in direction in-

  pours, a loss of light at the interface, when passing

  ge of the fiber with large digital aperture (in this case the transmitter) in the fiber with small digital aperture. The present invention

solves this problem.

  One of the methods for making the conical cone

  consists of heating a length of optical fiber, for example

  full between 20 and 30 cm, using a propane flame, up to

  reach the fiber softening temperature. When heating

  fage, the fiber is stretched uniformly while moving the flame

  regularly along the fiber. A conical zone is thus obtained.

  When the narrow end of the cone has reached a transverse diameter slightly smaller than that of the fiber to which it is connected, the operation of making the c8ne is interrupted and allowed to cool.

  the fiber. Using a marking tool, cut the co-

  nique at the desired transverse diameter and the marked surface is broken.

  Any other suitable means may be used to achieve the area

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conical.

  Although the principles of information have been described above

  vention with reference to a specific device, it is well-

  whereas this description is only given by way of example and does not

  cannot limit the scope of the invention as defined

  negates its purposes and the appended claims.

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Claims (10)

  1. Digital aperture transformer device   taking a core (7), a cladding layer (9) surrounding said core, said core and said sheath forming an elongated waveguiding structure   having two opposite end surfaces (6, 10) and a conical configuration   that extending from one of said end surfaces, longitudinally to said structure, at least along a large portion of the latter.   2. Arrangement of digital aperture transformer including   taking two structures (2, 11) for optical waveguiding having or   different digital vertices, each of said structures comprises   both two opposite end surfaces, and a means for adapting   ter said digital openings to each other, comprising a   conical optical waveguide device which is narrowed towards one of the   called waveguiding structures. -   3. Digital aperture transformer arrangement   The form of claim 2, characterized in that said conical waveguiding device is separate from the other waveguiding structure and is interposed between the two, said conical waveguiding device being in contact with said guide structures   waves at an interface zone of each of them.   4. Consistent digital aperture transformer arrangement   form in claim 2, characterized in that at least one of the   said optical waveguiding structures is an optical fiber which   includes a core and at least one cladding layer surrounding the core.   5. Digital aperture transformer arrangement   form according to claim 4, characterized in that said zone of in-   terface has an outer diameter substantially identical to the diameter   meter of the core of one of said fibers.   6. Digital aperture transformer arrangement   The form of claim 2, characterized in that one of said optical waveguiding structures is a light transmitter   and the other a light receiver. 9- - 2575557   7. Digital aperture transformer arrangement   form in claim 6, characterized in that one of said   optical waveguiding structures have a core diameter of   lower than that of the other waveguiding structure.   8. Digital aperture transformer arrangement   form in claim 6, characterized in that said other structure   optical waveguide structure has a larger core diameter   to that of said first waveguiding structure.   9. Digital aperture transformer arrangement   form in claim 2, characterized in that said end conical zone has a narrow end, a wide opposite end   and sufficient length to ensure that the light propagates   giant, along said sheath of said extreme conical zone, of the   said narrow end at said wide end is passed to   the soul of said extreme conical zone to continue its propagation.   10. Arrangement of core diameter transformer for   optical beams, comprising two optical waveguiding structures having cores of different diameter, and means making it possible to substantially adapt the diameter of one of said waveguiding structures to that of the other, including a conical end zone   of one of said waveguiding structures.