Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
  • H04B10/25—Arrangements specific to fibre transmission
  • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
  • H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
  • H04B10/2525—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using dispersion-compensating fibres

Definitions

• the present invention relates to a chromatic dispersion compensation device. It also relates to a chromatic dispersion compensation method.
• Such a device can for example enable a user to compensate for a specific chromatic dispersion of a signal by limiting the deterioration of this signal, in particular by limiting losses or non-linear effects.
• the field of the invention is more particularly, but without limitation, that of long-distance optical fiber signal transport.
• Chromatic dispersion distorts optical signals during propagation in optical fibers. This deformation is not a problem when the information is coded in a coherent manner, but is problematic when the coding of the information is done in the form of light pulses (which is the case for most 1G, 10G systems and a significant proportion of 40G).
• dispersion compensation modules are used. These modules have a negative chromatic dispersion, which compensates for the positive chromatic dispersion (necessary to avoid other problems) of the transmission fibers.
• the temperature sensitivity of the former can sometimes be a problem, while the second technology can introduce too many non-linear effects.
• the unit price of dispersion compensation modules has not changed significantly in recent years, due to the high cost of manufacturing Bragg gratings and dispersion-compensated single-mode fibers.
• the object of the present invention is to propose a solution for dispersion compensation: - the cost of which is significantly lower than existing solutions, and / or
• a chromatic dispersion compensation device comprising:
• an input converter arranged for:
• an output converter arranged for:
• the input converter and / or the output converter comprises a multi-pass type converter comprising:
• each correction location being arranged to modify the spatial phase profile of the light beam by a passage of the light beam by a reflection on or by a transmission through an irregular surface of this corrector position so that phase profile phase-shifts induced by this reflection or transmission is different between several points of reflection or transmission of this irregular surface, the correcting locations being successively arranged one after the other along the optical path of the light beam so that the light beam is reflected by or transmitted through the irregular surface of each corrector slot,
• the first mode is preferably a mode that can propagate in a single-mode optical fiber (i.e. in the input single-mode optical fiber and in the output single-mode optical fiber).
• the other (preferably higher order) mode is preferably a mode that can not propagate in a monomode optical fiber (i.e. in the input monomode optical fiber and the output monomode optical fiber).
• the device according to the invention may furthermore comprise:
• the input monomode optical fiber arranged to transmit the light beam according to the first mode, and which has positive chromatic dispersion properties for the first mode, and / or means of connection to this monomode input optical fiber
• the monomode optical output fiber and / or means of connection to this single-mode optical fiber output.
• - several (all in one extreme case) correcting locations may be located on a reflective surface of the same main mirror, and / or - several (all in one case extreme) corrective locations can be located a surface of the same transmission blade located between a main mirror and the means for optically transforming the light beam.
• the means for optically transforming the light beam preferably comprise means for making an optical Fourier transform of the light beam or a transformation close to an optical Fourier transform of the light beam.
• the means for optically transforming the light beam preferably comprise a so-called transformation mirror:
• the device according to the invention comprises the transformation mirror and the main mirror
• these mirrors preferably form a multi-passage cavity of the light beam.
• the input converter may comprise a multi-pass type converter.
• the output converter may comprise a multi-pass type converter.
• the input converter and the output converter may comprise in common or share the same multi-pass type converter.
• the input converter and / or the output converter may comprise a compound converter which is arranged for several successive conversions of modes of the light beam. At least one (or each) converter composed:
• the light beam passes through an intermediate multimode optical fiber, preferably with a negative chromatic dispersion, and / or
• chromatic dispersion compensation devices may have several of its intermediate multimode fibers which are grouped into a single intermediate multimode optical fiber, preferably with a negative chromatic dispersion.
• the single intermediate multimode optical fiber and the multimode optical fiber compensation can be confused.
• a set of chromatic dispersion compensation devices according to the invention, characterized in that they share:
• a chromatic dispersion compensation method is proposed (preferably implemented in a device according to the invention that has just been disclosed or as subsequently described, considering that many aspects are not limiting in the description of the figures) comprising:
• the input converter and / or the output converter comprises a multi-pass type converter comprising a plurality of correcting locations:
• each corrective location modifying the spatial phase profile of the light beam by a passage of the light beam by reflection on or by a transmission through an irregular surface of this corrector location so phase phase phase shifts induced by this reflection or transmission are different between several points of reflection or transmission of this irregular surface
• the correcting locations being successively arranged one after the other along the optical path of the light beam so that the light beam is reflected by or transmitted through the irregular surface of each corrector slot,
• the method further comprising, between each pair of successive corrective locations along the optical path of the light beam, an optical transformation of the light beam by transformation means.
• the optical transformation of the light beam by transformation means preferably comprises an optical Fourier transform of the light beam or a transformation close to an optical Fourier transform of the light beam.
• the input converter and / or the output converter may comprise a composite converter which implements several successive conversions of modes of the light beam.
• a composite converter which implements several successive conversions of modes of the light beam.
• the light beam can pass through an intermediate multimode optical fiber, preferably with a negative chromatic dispersion.
• the method according to the invention can be implemented in parallel in a set of chromatic dispersion compensation devices according to the invention which share:
• FIG. 1a is a schematic view of a first embodiment of a device according to the invention
• FIG. 1b is a side view of a multi-pass type converter 7 used in the first device embodiment according to the invention.
• FIG. 2 is a schematic view of a second embodiment of a device according to the invention.
• FIG. 3 is a more concrete schematic view of the second embodiment of the device according to the invention.
• FIG. 4 is a schematic view of a third embodiment of a device according to the invention.
• FIG. 5 is a diagrammatic view of a fourth embodiment of a device according to the invention.
• FIG. 6 is a schematic view of a fifth embodiment of a device according to the invention.
• FIG. 7 is a schematic view of a first embodiment of a set of devices according to the invention.
• FIG. 8 is a schematic view of a second embodiment of a set of devices according to the invention.
• FIG. 9 is a schematic view of a third embodiment of a set of devices according to the invention.
• FIG. 10 is a schematic view of a fourth embodiment of a set of devices according to the invention.
• FIG. 11 is a schematic view of a fifth embodiment of a set of devices according to the invention.
• variants of the invention comprising only a selection of characteristics described or illustrated subsequently isolated from the other characteristics described or illustrated (even if this selection is isolated within a sentence including these other characteristics), if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention from the state of the invention. prior art.
• This selection comprises at least one preferably functional characteristic without structural details, and / or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention from the state of the art. earlier.
• the chromatic dispersion compensation device 1 comprises an input monomode optical fiber 2 arranged to transmit a light beam 9 according to a first mode, also called a "transmission mode".
• the optical beam 9 is for example a light modulation at 16 GHz in a working wavelength range of 1530 to 1570 nm or in the band C of the electromagnetic spectrum (the device 1 having a wide bandwidth).
• the input monomode optical fiber 2 is typically a section of ITU G652 optical reference fiber.
• This fiber 2 can be several kilometers long.
• This fiber 2 has a positive chromatic dispersion over the working wavelength range of the beam 9 for the first mode.
• Mode denotes a specific spatial mode of propagation of the light beam 9 through an optical fiber, preferably according to the mode base known to those skilled in the art under the terminology LP
• m with: m a natural number greater than or equal to one
• I a natural number greater than or equal to zero
• the first (transmission) mode is preferably the fundamental mode of propagation of the light beam 9 through a fiber monomode optics, known optics in the terminology LP 0 i (or HEn according to the mode base used).
• the fundamental mode (for example called LP 0 i or HEn according to the mode base used) is the proper spatial mode of propagation for which the light intensity of the beam 9 is strictly greater than zero over the entire transverse surface of the beam. optical fiber in which the beam 9 propagates.
• the device 1 comprises a multimode optical fiber compensation 3.
• the device 1 comprises an input converter 4, arranged for:
• the first mode which can propagate in a single-mode optical fiber
• another higher order mode also called "compensation mode”
• the multimode compensation optical fiber 3 has negative chromatic dispersion properties over the working wavelength interval of the beam 9 and, after this conversion
• high order mode is meant a specific spatial mode of propagation of the light beam 9 through an optical fiber different from the fundamental mode, for example according to the LP mode base with a higher order than the LP mode 0 i, that is to say a mode known in optics under the terminology:
• I a natural integer greater than zero.
• the higher order mode is for example the LP 02 mode -
• the multimode optical fiber compensation 3 is a multimode fiber for example allowing the propagation of a small number of modes (typically a maximum of 6 or 10 modes including the fundamental), generally designated by the abbreviation FMF (for "Few modes Fiber " in English).
• multimode compensation optical fibers 3 applicable to the present invention, and which exhibit negative chromatic dispersion properties for a higher order mode, are numerous in the literature. We can for example quote:
• the device 1 comprises an output monomode optical fiber 5, distinct from the monomode input fiber 2.
• the output monomode optical fiber 5 is typically a section of ITU G652 optical reference fiber.
• This fiber 5 has a positive chromatic dispersion over the working wavelength range of beam 9 for the first mode.
• the device 1 comprises an output converter 6, arranged for:
• the input converter 4 comprises at least one multi-pass type converter 7, also called "MPLC".
• the output converter 6 comprises at least one multi-pass type converter 7.
• each of the input converter 4 and the output converter 6 comprises (preferably consists of) a multi-pass type converter 7 comprising several correcting locations 81, 82, 83, 84.
• Each corrector location 81, 82, 83, 84 is arranged to modify the spatial phase profile of the light beam 9 by a passage of the light beam 9:
• the corrective locations 81, 82, 83, 84 are successively arranged one after the other along the optical path of the light beam 9 so that the light beam 9 is reflected by or transmitted through the irregular surface of each corrector slot,
• Each converter 7 furthermore comprises, between each pair of successive correcting locations torques (torque 81 and 82, then torque 82 and 83, then torque 83 and 84) along the optical path of the light beam 9, means 10 for optically transforming the light beam 9.
• the main mirror 12 is a substantially plane mirror.
• the means 10 for optimally transforming the light beam 9 comprise (preferably consist of) means for making an optical Fourier transform of the light beam 9 (or at least substantially a Fourier transform or a transformation as close as possible to a Fourier transform).
• the means 10 for transforming optically the light beam 9 comprise a transformation mirror 11:
• the transformation mirror 11 and the main mirror 12 form a multi-passage cavity of the light beam 9.
• the converter 7 shown in FIG. 1b thus comprises two reflective optical elements 12 and 10, 11 forming between them a multipass cavity 7 in which a light radiation to be treated 9 undergoes a plurality of reflections and propagations.
• the reflecting element 10, 1 1 has a through opening
• the reflective element 12 has a substantially flat reflective surface 112 and the reflective element 10, 11 has a concave or curved reflecting surface 114.
• the multipass cavity defined by the mirrors 12 and 10, 11 is arranged so that the light radiation 9 is reflected a plurality of times by each of the mirrors 11 and 12 at different locations, in turn.
• the plane mirror 12 reflects the optical radiation 9 q four times in four different reflection locations on the flat surface 112 and the curved mirror 10, 11 reflects the optical radiation 9 three times, at three different reflection locations on the surface 114.
• the reflecting element 10, 11 is formed by a curved or concave mirror and does not apply any modification to the spatial phase profile of the optical radiation 9 outside its curvature.
• Each near transformation (because the propagation is not necessarily strictly equal to the focal length of the curved mirror) of a Fourier transform is performed by:
• the reflecting element 12 is said corrector.
• This reflecting element 12 is formed by a plane mirror whose reflective surface 112 is deformed at the scale of the working lengths of the beam 9, applying a modification of the spatial phase of the optical radiation 9.
• the deformed plane mirror 12 present at each reflection location 81, 82, 83, 84, an irregular surface so that each reflection location 81, 82, 83, 84 is corrective and has a spatial phase profile modifying the spatial phase of the radiation 9.
• each region / zone / reflection location 81, 82, 83, 84 has different depths for at least two spatial components of the radiation 9 and makes a modification of the spatial phase of the optical radiation 9, that is to say different phase shifts of at least two spatial components of the radiation 9.
• a second embodiment of the salt device will now be described with reference to FIGS. 2 and 3 the invention, but only for its differences from the first device embodiment of Figure 1.
• This architecture is more compact and less expensive.
• the input converter 4 and the output converter 6 comprise in common (that is to say share) the same multi-pass type converter 7.
• the converter 7 comprises a larger number of reflection locations than in the previous embodiment, namely:
• locations 82 and 82 ' may be identical, such as locations 82 and 82 '.
• the spatial phase profile of these locations is then optimized accordingly.
• FIG. 3 is a schematic view of the second embodiment of the device according to the invention detailing the concrete manner in which the light beam 9 is brought in / out twice in the cavity 7, and the following FIGS. 5 to 11 are views of less concrete principle.
• the concrete implementations of one or more cavities 7 in FIGS. 5 to 11 are natural from the view of FIGS. 1b and 3 whereas the multi-pass converter 7 is not limited to two orthogonal spatial modes of entry and two spatial orthogonal output modes as shown in Figure 3, but a three input / output implementation has already been published (Efficient and selective mode spatial mode multiplexer based on multi-plane light conversion ", Optics Express, vol. n ° 13, June 2014), and that six input / output systems are already on the market.
• a formal definition of the orthogonality of two spatial modes can be found in Anthony E.
• Two spatial modes are orthogonal when they can be considered as two independent information channels.
• m are orthogonal two by two.
• two spatial modes carried by different fibers constitute independent information channels and are also orthogonal.
• a conventional criterion for ascertaining the orthogonality of two spatial modes is to measure the intensity that passes through a plane. transverse to the propagation. If this intensity depends on the relative phase of the two spatial ones, then they are not orthogonal, otherwise they are.
• a third device embodiment according to the invention will now be described with reference to FIG. 4, but only for its differences with respect to the first device embodiment of FIG. 1.
• the input converter 4 comprises a composite converter 13 which is arranged for several successive conversions of modes of the light beam 9.
• the output converter 6 comprises a composite converter 13 which is arranged for several successive conversions of modes of the light beam 9.
• Each composite converter 13 comprises several multi-pass type converters 7 as previously described with reference to FIG.
• Each composite converter 13 is arranged so that, between each pair of successive conversions, the light beam 9 passes through an intermediate multimode optical fiber 14, preferably with a negative chromatic dispersion over the working wavelength interval of the beam 9. .
• Each multimode optical fiber 14 is of the same nature as the compensation fiber 3.
• a first multi-pass converter 7, 7a converts the first mode (LP 0 i) originating from the monomode fiber 2 into another mode (for example LP 02 ),
• a second multi-pass converter 7, 7b converts this other mode (for example LP 02 ) into another mode (for example LP03)
• a third multi-pass converter 7, 7c converts this still another mode (for example LP 03 ) into the "higher order mode” (for example LP 04 ) and injects it into the compensation optical fiber 3.
• this still another mode for example LP 03
• the "higher order mode” for example LP 04
• a first multi-pass converter 7, 7d converts the "higher order mode" (for example LP 04 ) coming from the compensation optical fiber 3 into another mode (for example LP 03 ), - a second converter multi-pass 7, 7th converts this other mode (eg LP 03 ) into another mode (eg LP02)
• a third multi-pass converter 7, 7f converts this still another mode (for example LP 02 ) into the "first mode” (LP01) and injects it into the single-mode output fiber 5.
• a fourth device embodiment according to the invention will now be described with reference to FIG. 5, but only for its differences with respect to the third device embodiment of FIG. 4.
• the output converter 6 comprises a composite converter 13 which is arranged for several successive conversions of modes of the light beam 9.
• each input composite converter 13 or FIG. Exit 6 only makes two conversions instead of three.
• Each composite converter 13 is arranged so that several of (more exactly all) its successive conversions are implemented by the same multi-pass type converter 7.
• the input converter 4 and the output converter 6 comprise in common (that is to say share) the same multi-pass type converter 7.
• the multi-pass converter 7 converts the first mode (LP 0 i) coming from the monomode fiber 2 into another mode (for example LP 02 ) and injects it into the intermediate optical fiber 14 a,
• the multi-pass converter 7 converts this other mode (for example LP 02 ) coming from the intermediate optical fiber 14a into the "higher order mode" (for example LP 03 ) and the injection into the optical fiber of compensation 3.
• the output converter 6 In the output converter 6:
• the multi-pass converter 7 converts the "higher order mode" (for example LP03) coming from the compensation optical fiber 3 into another mode (for example LP 04 ) and injects it into the intermediate optical fiber 14b,
• the multi-pass converter 7 converts this other mode (for example LP 04 ) coming from the intermediate optical fiber 14b into the "first mode" (LP 0 i) and injects it into the single-mode output fiber 5.
• FIG. 5 corresponds to a multi-pass type converter 7, which is built on the same principle as that illustrated in FIG. 1b, but which comprises four beam inputs / outputs.
• a fifth device embodiment according to the invention will now be described with reference to FIG. 6, but only for its differences with respect to the fourth device embodiment of FIG. 5.
• FIG. 6 corresponds to a multi-pass type converter 7, which is built on the same principle as that illustrated in FIG. 1b, but which comprises four inputs / outputs of the beam 9.
• the multi-pass type converter 7 comprises k + 1 inputs / outputs of the beam 9 .
• FIG. 7 A first embodiment of an assembly 16 of devices 1 according to the invention will now be described with reference to FIG. 7, each of these devices being only described for their differences with respect to the first embodiment of the device.
• Figure 1 A first embodiment of an assembly 16 of devices 1 according to the invention will now be described with reference to FIG. 7, each of these devices being only described for their differences with respect to the first embodiment of the device. Figure 1.
• Figure 7 shows a set of three devices 1 (three being obviously only an example). There are thus three distinct monomode input fibers 2 (referenced 2a, 2b, 2c) for three distinct light beams 9 (respectively referenced 9a, 9b, 9c) and for three distinct monomode output fibers 5 (respectively referenced 5a, 5b, 5c).
• Figure 7 corresponds to two multi-pass converters 7.
• Each multi-pass converter 7 of FIG. 7 corresponds to a multi-pass type converter 7, which is built on the same principle as that illustrated in FIG. 1b, but which comprises three beam inputs / outputs.
• a second embodiment of a set of devices according to the invention will now be described with reference to FIG. 8, but only for its differences with respect to the first overall embodiment of FIG. 7.
• the input converter 4 and the output converter 6 comprise in common (that is to say share) the same multi-pass type converter 7.
• FIG. 8 corresponds to a multi-pass type converter 7, which is built on the same principle as that illustrated in FIG. 1b, but which comprises six beam inputs / outputs.
• FIG. 9 A third embodiment of a set of devices according to the invention will now be described with reference to FIG. 9, but only for its differences with respect to the first overall embodiment of FIG. 7.
• the devices 1 of the assembly 16 share the same multimode optical fiber compensation 3.
• FIG. 9 corresponds to two multi-pass converters 7.
• Each multi-pass converter 7 of FIG. 9 corresponds to a multi-pass type converter 7, which is built on the same principle as that illustrated in FIG. 1b, but which comprises three beam inputs / outputs.
• the input converter 4 converts the first mode (LP 0 i) from the three input monomode fibers 2a, 2b, 2c into a distinct higher order mode for each beam 9a, 9b and 9c of each device 1 and orthogonal to the conversion modes of the other beams. For example :
• LP 02 , LP 0 3 and LP 04 modes being distinct and orthogonal to each other.
• the output converter 6 converts the higher order mode (for example LP 02 or LP 0 3 or P 04 ) of each beam 9a, 9b, 9c from the compensation fiber 3 into the first mode (LP 0 i ). It is thus possible to use several spatial modes in the same compensation fiber 3 to reduce the number of fibers used.
• FIG. 10 A fourth embodiment of a set of devices according to the invention will now be described with reference to FIG. 10, but only for its differences with respect to the third overall embodiment of FIG. 9.
• the input converter 4 and the output converter 6 comprise in common (that is to say share) the same multi-pass type converter 7.
• FIG. 10 corresponds to a multi-pass type converter 7, which is built on the same principle as that illustrated in FIG. 1b, but which comprises six beam inputs / outputs.
• a fifth embodiment of a set of devices according to the invention will now be described with reference to FIG. 11, but only for its differences with respect to the fourth overall embodiment of FIG. 10.
• the input converter 4 comprises a composite converter 13 which is arranged for several successive conversions of modes of the light beam 9.
• the output converter 6 comprises a composite converter 13 which is arranged for several successive conversions of modes of the light beam 9.
• Each composite converter 13 is arranged so that several of (more exactly all) its successive conversions are implemented by the same multi-pass type converter 7.
• Each compound converter 13 is arranged so that, between each pair of successive conversions, the light beam 9 passes through an intermediate multimode optical fiber 14, preferably with a negative chromatic dispersion.
• intermediate multimode fibers (intermediate) 14 of the output composite converter 6, 13 are grouped into a single intermediate multimode optical fiber 15, preferably with a negative chromatic dispersion.
• This single intermediate multimode optical fiber 15 and the multimode optical fiber compensation 3 are combined.
• a high order mode in a specialized multimode fiber 3 is an effective means for compensating for chromatic dispersion: the specialized multimode fiber 3 is easier to achieve than the monomode dispersion-compensating fiber. Conventionally, dispersion compensation is faster (so less fiber length is needed to compensate for as much propagation in the network), and unlike Bragg gratings, this approach is not temperature sensitive. This idea of using a high order mode in a specialized multimode fiber has not been satisfactorily implemented so far because of the difficulty of efficiently converting the spatial mode of the propagation fiber 2 into the mode. high order.
• At least one or each corrector slot may be arranged to modify the spatial phase profile of the light beam by passing the light beam through a transmission (and not a reflection) through a surface. irregularity of this correction location as described in WO 2012/085046 or the article "Efficient and selective mode spatial mode multiplexer based on multi-plane light conversion", Optics Express, vol .22, No. 13, June 2014.
• the correcting locations 81 to 84 or 81 to 86 and / or 81 'to 86' instead of being located on the main mirror 12, may be located wholly or partly on a surface of the same transmission blade ( or several separate blades) located (s) between the main mirror 12 and the means 10 for optically transforming the light beam 9.
• the reflecting element 10, 11 is not corrective.
• the reflecting element 10, 11 may also be corrective, at least for a part of the reflection sites on this reflecting element 10, 11.
• the reflecting element 12 corrects for each reflection location on this reflecting element 12.
• the reflecting element 12 can be corrector for only part of the reflection locations. on this reflecting element 12.
• each corrective reflection location may have the same irregularity, that is to say a phase profile identical to that of another corrective reflection location.
• the mirrors 11 and 12 face each other.
• the mirrors 11 and 12 are not centered on the same axis but along two different axes (for example perpendicular), and a mirror or an intermediate reflecting element is disposed in the cavity 7 and is arranged to reflect the beam 9 (for example at a right angle) of the mirror 11 to the mirror 10 and the mirror 10 to the mirror 11.
• the invention (device 1 or assembly 16) can be reduced to a chromatic dispersion compensation module, that is to say without any monomode input fiber 2, 2a, 2b, 2c and / or output 5, 5a, 5b, 5c but with the necessary connection means.

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