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WO2018138982A1 - Fibre optique d'amplification - Google Patents

Fibre optique d'amplification Download PDF

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Publication number
WO2018138982A1
WO2018138982A1 PCT/JP2017/037515 JP2017037515W WO2018138982A1 WO 2018138982 A1 WO2018138982 A1 WO 2018138982A1 JP 2017037515 W JP2017037515 W JP 2017037515W WO 2018138982 A1 WO2018138982 A1 WO 2018138982A1
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WIPO (PCT)
Prior art keywords
light
core
mode
optical fiber
active element
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PCT/JP2017/037515
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English (en)
Japanese (ja)
Inventor
淑通 安間
竹永　勝宏
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株式会社フジクラ
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Publication of WO2018138982A1 publication Critical patent/WO2018138982A1/fr

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    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating

Definitions

  • the present invention relates to an amplification optical fiber capable of amplifying higher-order mode light than fundamental mode light.
  • optical communication using an optical fiber information is superimposed on light in the LP 01 mode (basic mode), and information communication is performed by superimposing information on light in an LP mode higher than the basic mode such as the LP 11 mode.
  • Multi-mode communication to perform is known.
  • optical communication it is known that the intensity of light propagating through an optical fiber is attenuated by long-distance transmission, and the intensity of the attenuated light is amplified using an optical fiber amplifier.
  • Non-Patent Document 1 describes an amplification optical fiber in which an active element is added to a wide range of a core and a clad including a waveguide region for fundamental mode light and higher-order mode light. According to this amplification optical fiber, it is said that fundamental mode light and higher mode light can be amplified equally.
  • higher-order mode light propagating through an optical fiber tends to have a larger loss than fundamental mode light.
  • the main cause of this is as follows.
  • the mode field diameter (MFD) of the higher mode light is larger than the mode field diameter of the fundamental mode, and the light intensity at the interface between the core and the clad is higher in the higher mode light than in the fundamental mode light. Since impurities such as hydroxyl groups tend to remain at the interface between the core and the clad, light tends to be lost at the interface. Therefore, higher-order mode light having a higher intensity than fundamental mode light at the interface causes a greater loss.
  • the light in the higher mode is amplified than the light in the fundamental mode.
  • the amplification optical fiber of Non-Patent Document 1 is used, the light in the fundamental mode and the light in the higher order mode are equally amplified.
  • an object of the present invention is to provide an amplification optical fiber capable of amplifying light of a higher mode than light of a fundamental mode.
  • the present invention has a core and a clad, and light of a predetermined wavelength used for communication propagates through the core in at least two LP modes and forms at least a part of a light waveguide region.
  • An amplification optical fiber to which an active element is added, focusing on the light of a specific higher-order mode propagating through the core, the normalized intensity of the LP 01 mode light in the radial direction and the specific high-order light The innermost position where the normalized intensity of the light of the next mode matches the specific inner position, and the outermost position where the standardized intensity of the light of the specific higher order mode is 0.0001 is specified as the outer position.
  • the average concentration of the active element from the specific inner position to the specific outer position is It is higher than the average concentration of the active element from the center point to the specific inner position, and the amplification factor of all higher-order mode light used for communication is larger than the amplification factor of light in the fundamental mode It is.
  • Non-Patent Document 1 an active element having a constant concentration is added to the light guiding region, and the fundamental mode light and the higher-order mode light are amplified with the same amplification factor.
  • the average of the average concentration of active elements from the specific inner position to the specific outer position is the basic mode.
  • the light intensity is higher than the average concentration average of the active elements from the center point of the core, which is larger than the light intensity of the higher mode, to the specific inner position. Therefore, the amplification factors of all the higher-order mode light propagating through the core can be made larger than the amplification factors of the fundamental mode light.
  • the higher order mode is preferably an LP 11 mode and an LP 21 mode.
  • the higher-order mode is limited to the above-mentioned mode, even higher-order mode light in the even mode does not enter, and higher-order mode light can be more easily amplified than in the fundamental-mode light.
  • the active element is not added from the center point of the core to the specific inner position in the LP 11 mode light propagating through the core.
  • the specific inner position in the LP 11 mode light is closer to the center point of the core than the specific inner position in any higher order mode light. Since the active element is not added to the region from the center point of the core to at least the specific inner position, the amplification factor of the higher mode light can be made larger than the amplification factor of the fundamental mode light.
  • the active element is not added from the center point of the core to the specific inner position in the highest order higher-order mode light used for communication propagating through the core.
  • the active element is not added to the core.
  • the amplification factor of the higher mode light can be made larger than the amplification factor of the fundamental mode light.
  • the active element is preferably added at a high concentration.
  • the active element is preferably added at a concentration higher than the average concentration of the active element from the center point of the core to the specific inner position when paying attention to LP 11 mode light propagating through the core.
  • the specific outer position when focusing on the light of the highest order higher order mode used for communication propagating through the core from the specific inner position when focusing on the LP 11 mode light propagating through the core.
  • the active element and the active element at a concentration higher than the average concentration of the active element up to the specific inner position when focusing on LP 11 mode light propagating through the core from the central point of the core It is preferable that an element is added.
  • the amplification factor of the higher-order mode light can be made larger than the amplification factor of the light in the fundamental mode.
  • a multi-core amplification optical fiber can be realized.
  • each core light propagates in two or more LP modes, and in the case of paying attention to any higher-order mode light propagating through the core, the average concentration of the active element from the specific inner position to the specific outer position is The higher than the average concentration of the active element from the center point of the core to the specific inner position, the amplification factors of all higher-order modes are larger than the amplification factors of the fundamental modes. Therefore, the amplification factors of all higher-order mode light propagating through the respective cores of the multi-core amplification optical fiber can be made larger than the amplification factors of the fundamental mode light.
  • an outer cladding that covers the cladding and has a refractive index lower than that of the cladding.
  • the outer periphery of the clad has a polygonal shape.
  • the active element may be erbium.
  • the C-band and L-band light used for optical communication can be efficiently amplified.
  • an optical fiber for amplification capable of amplifying higher-order mode light than fundamental mode light is provided.
  • FIG. 1 is a view showing a state of a cross section perpendicular to the longitudinal direction of an optical fiber according to a first embodiment of the present invention.
  • an amplification optical fiber 10 includes a core 11, a clad 12 that surrounds the outer peripheral surface of the core 11 without a gap, an outer clad 13 that covers the outer peripheral surface of the clad 12, and an outer clad 13 as a main component.
  • the diameter of the core 11 is, for example, 11 ⁇ m.
  • the outer diameter of the cladding 12 is, for example, 125 ⁇ m, and the outer diameter of the outer cladding 13 is, for example, 200 ⁇ m.
  • the amplification optical fiber 10 of the present embodiment amplifies light used for communication, and an active element is added to at least a part of a waveguide region of propagating light.
  • the amplification optical fiber 10 is a multimode optical fiber that propagates light including LP 11 mode higher-order mode light in addition to LP 01 mode light, which is the fundamental mode of light propagating through the core 11. . Accordingly, when the LP 01 mode light and the LP 11 mode light are incident on the core 11 of the amplification optical fiber 10, the light of each mode can propagate through the amplification optical fiber 10.
  • the predetermined wavelength is, for example, a C band band or an L band band.
  • the amplification optical fiber 10 is intended to amplify the light used for communication as described above. Therefore, even when high-order mode light not related to communication is excited, this higher-order mode is used. There is no need to consider the light.
  • FIG. 2 is a diagram illustrating the state of the core 11 of the amplification optical fiber 10 of FIG. 1 and the surroundings thereof. Specifically, FIG. 2A shows the core 11 and the cladding 12 in the region indicated by the dotted line in FIG. 1, FIG. 2B shows the refractive index distribution in the region shown in FIG. FIG. 2 (C) amplification optical fiber 10 of the LP 01 mode when normalized by LP 01 mode of light and LP 11 mode power the light when the propagating light of a predetermined wavelength of light and LP 11 modes FIG. 2D shows the light intensity distribution, and FIG. 2D shows the concentration distribution of the active element in the region shown in FIG.
  • the refractive index of the cladding 12 is set lower than that of the core 11.
  • the refractive index of the outer cladding 13 is set lower than the refractive index of the cladding 12.
  • the refractive index of the core 11 is substantially constant in the radial direction
  • the refractive index of the cladding 12 is also substantially constant in the radial direction.
  • the relative refractive index difference between the core 11 and the clad 12 is, for example, 0.6%.
  • the core 11 is made of, for example, quartz to which a dopant such as germanium that increases the refractive index is added
  • the cladding 12 is made of, for example, quartz that is not particularly added with a dopant that increases the refractive index.
  • the core 11 may be made of, for example, quartz to which a dopant that increases the refractive index is not particularly added
  • the cladding 12 may be made of, for example, quartz to which a dopant such as fluorine that lowers the refractive index is added.
  • the core 11 and the clad 12 are added with an active element as necessary, as will be described later.
  • the outer cladding 13 is made of, for example, an ultraviolet curable resin or quartz to which a dopant for lowering the refractive index is added.
  • the covering layer 14 is made of, for example, an ultraviolet curable resin different from the outer cladding 13.
  • the LP 11 mode light has an intensity distribution as shown in FIG.
  • the LP 01 mode light has the intensity distribution that is the strongest at the center point C of the core 11, and the LP 11 mode light has an intensity of 0 at the center point C of the core 11, and the center point C of the core 11.
  • the outer peripheral surface IF of the core 11 have a peak intensity. Therefore, at a specific position between the center point C of the core 11 and the outer peripheral surface IF of the core 11, the light intensity of the LP 11 mode matches the light intensity of the LP 01 mode. This position is defined as a specific inner position Ri.
  • the intensity of light in the LP 11 mode is greater than the intensity of light in the LP 01 mode on the outer peripheral side from the specific inner position Ri.
  • the amplification optical fiber 10 propagates so as to protrude from the outer peripheral surface IF of the core 11 to the cladding 12. Accordingly, the light waveguide region extends to a region adjacent to the core 11 in the clad 12, and the light that protrudes into the clad 12 is attenuated from the core 11 side toward the outer peripheral side of the clad 12 in the clad 12.
  • the LP 11 mode light has a larger mode field diameter than the LP 01 mode light, and the protrusion to the clad 12 is large. Therefore, on the outer peripheral surface IF of the core 11, the intensity of the LP 11 mode light is greater than the intensity of the LP 01 mode light.
  • the normalized intensity of the LP 11 mode light is 0.0001 at specific positions on the inner and outer peripheral surfaces of the clad 12. That is, the light intensity when the intensity distribution is normalized so that the integral value in the radial direction of the light intensity distribution of the LP 11 mode is 1 becomes 0.0001. This position is defined as a specific outer position Ro. In this way, when the normalized intensity of light becomes 0.0001, it does not affect the propagation and amplification of light. Therefore, there is no need to consider light whose normalized intensity is less than 0.0001.
  • the light intensity of the LP 01 mode is larger than the light intensity of the LP 11 mode, and from the specific inner position Ri to the specific outer position Ro.
  • the intensity of the LP 11 mode light is larger than the intensity of the LP 01 mode light. Therefore, on the outer peripheral surface IF of the core 11, the intensity of the LP 11 mode light is greater than the intensity of the LP 01 mode light.
  • no active element is added to the region from the center point C of the core 11 to the specific inner position Ri, and the specific inner position Ri.
  • the active element is added to the region from the specific outer position Ro.
  • This active element is an element that is brought into an excited state by excitation light.
  • erbium (Er) can be cited as the active element.
  • the active element to be added varies depending on the wavelength of the propagating light, and examples of other active elements include rare earth elements such as neodymium (Nd) and ytterbium (Yb).
  • bismuth (Bi) can be cited as an active element in addition to rare earth elements.
  • the light incident on the core 11 of the amplification optical fiber 10 and light having a wavelength for exciting the active element is incident on the cladding 12 is amplified as follows. . That is, the excitation light incident on the clad 12 propagates mainly through the clad 12, and the active element is excited when the excitation light passes through the region where the active element is added.
  • the excited active element causes stimulated emission by light having a predetermined wavelength propagating through the amplification optical fiber 10, and the light having the predetermined wavelength is amplified by the stimulated emission.
  • the active element is added to the region from the specific inner position Ri to the specific outer position Ro, and the active element is not added to the region from the center point C of the core 11 to the specific inner position Ri. It is amplified in the region from the inner position Ri to the specific outer position Ro, and is not amplified in the region from the center point C of the core 11 to the specific inner position Ri.
  • Region where light is amplified is an area intensity of light of the light LP 11 mode than the intensity of the large LP 01 mode, no light is amplified region, than the intensity of light of the LP 11 mode of the LP 01 mode This is a region where the intensity of light is high. Therefore, when compared with the amplification optical fiber in which the active element is uniformly added to the entire core, according to the amplification optical fiber 10 of the present embodiment, the LP 11 mode light is more efficient than the LP 01 mode light. Amplified well.
  • the amplification factor of the LP 11 mode light can be made larger than the amplification factor of the LP 01 mode light.
  • FIG. 3 is a diagram showing the optical fiber amplifier of the present embodiment.
  • the optical fiber amplifier 1 in the present embodiment includes an incident end 20 on which signal light is incident, an excitation light source 30 that emits excitation light, an optical combiner 40 on which signal light and excitation light are input,
  • the amplification optical fiber 10 of FIG. 1 into which signal light and pumping light emitted from the optical combiner 40 are input, and an emission end 50 from which the amplified signal light is emitted are mainly configured.
  • the incident end 20 is connected to, for example, an optical fiber that performs optical communication using at least LP 01 mode light and LP 11 mode light. Accordingly, light having a predetermined wavelength including light of LP 01 mode and light of LP 11 mode used for optical communication is incident from the incident end 20.
  • the predetermined wavelength is not particularly limited, but is, for example, a C band band or an L band band as described above.
  • the light incident from the incident end 20 is composed of a core and a clad covering the core, and propagates through the optical fiber 25 that propagates the light in at least the LP 01 mode and the LP 11 mode.
  • the excitation light source 30 is composed of a plurality of laser diodes 31.
  • the laser diode 31 is, for example, a Fabry-Perot type semiconductor laser made of a GaAs-based semiconductor and emits light having a center wavelength of 980 nm. To do.
  • Each laser diode 31 of the excitation light source 30 is connected to an optical fiber 35, and the excitation light emitted from the laser diode 31 propagates through the optical fiber 35 as multimode light.
  • the optical combiner 40 to which the optical fiber 35 and the optical fiber 25 are connected is configured, for example, by melting and extending a portion where the multimode optical fiber is disposed around the optical fiber 25 as a center.
  • the core of the optical fiber 25 and the core 11 of the amplification optical fiber 10 are optically coupled, and the core of the optical fiber 35 and the cladding 12 of the amplification optical fiber 10 are optically coupled.
  • signal light incident from the incident end 20 is emitted from the optical fiber 25.
  • the wavelength of the signal light is, for example, C band or L band, and includes LP 01 mode light and LP 11 mode light. Then, the signal light propagating through the optical fiber 25 enters the optical combiner 40.
  • excitation light for exciting the active element added to the core 11 of the amplification optical fiber 10 is emitted from the excitation light source 30.
  • the wavelength at this time is, for example, 980 nm as described above. Then, the excitation light emitted from the excitation light source 30 propagates through the optical fiber 35 and enters the optical combiner 40.
  • the signal light incident on the core 11 of the amplification optical fiber 10 from the optical combiner 40 propagates through the core 11, and the excitation light incident on the cladding 12 of the amplification optical fiber 10 propagates mainly through the cladding 12.
  • the active element added as described above is in an excited state. Then, the excited active element causes stimulated emission by the signal light, and the signal light is amplified. At this time, the signal light is amplified in the region from the specific inner position Ri to the specific outer position Ro as described above for the amplification optical fiber 10, and in the region from the center point C of the core 11 to the specific inner position Ri. Not amplified. Accordingly, the signal light obtained by amplifying the LP 11 mode light with a higher amplification factor than the LP 01 mode light is emitted from the amplification optical fiber 10, and the signal light is emitted from the emission end 50.
  • the optical fiber amplifier 1 of the present embodiment it is possible to amplify the LP 11 mode light with a higher amplification factor than the LP 01 mode light. Accordingly, if the incident end 20 is a LP 01 mode of the optical power of the optical power and the LP 11 mode is the same in the light incident in the light emitted from the optical fiber amplifier 1 of LP 11 mode the power of the light LP It can be made larger than the light power of the 01 mode.
  • FIG. 4 is a view showing the concentration distribution of the active element in the amplification optical fiber 10 of the present modification as in FIG. 2D.
  • the active element is not added to the core 11, and the active element is added to the region from the outer peripheral surface IF of the core 11 to the specific outer position Ro.
  • the active element is not added to the region from the center point C to the specific inner position Ri as described above, and the active element is not added to the region from the specific inner position Ri to the specific outer position Ro.
  • the amplification factor of light in the LP 11 mode can be made larger than the amplification factor of light in the LP 01 mode.
  • the amplification optical fiber 10 of the present embodiment differs from the amplification optical fiber 10 of the first embodiment in that LP 21 mode light used for communication propagates.
  • FIG. 5 is a view showing the light intensity distribution in the case where the LP 21 mode light propagates through the amplification optical fiber 10 of FIG. 1, as in FIG.
  • the intensity distribution of the LP 01 mode light and the LP 11 mode light is shown in FIG. Same as C). Therefore, in the present embodiment, the position at which the intensity of the LP 11 mode light matches the intensity of the LP 01 mode light is defined as the specific inner position Ri 1, and the normalized intensity of the LP 11 mode light is 0.0001.
  • the light intensity of the LP 21 mode is 0 at the center point C of the core 11, and there are two positions where the intensity peaks between the center point C of the core 11 and the outer peripheral surface IF of the core 11. To do. Therefore, at a specific position between the center point C of the core 11 and the outer peripheral surface IF of the core 11, there are a plurality of positions where the light intensity of the LP 21 mode coincides with the light intensity of the LP 01 mode. Therefore, the innermost position among the positions where the light intensity of the LP 21 mode matches the light intensity of the LP 01 mode is set as the specific inner position Ri 2 .
  • the LP 21 mode light has a larger mode field diameter than the LP 01 mode light and the LP 11 mode light, and the protrusion to the clad 12 is large. Therefore, at the interface between the core 11 and the cladding 12, the intensity of the LP 21 mode light is larger than the intensity of the LP 01 mode light and the LP 11 mode light. The position of this interface coincides with the position of the outer peripheral surface IF of the core 11. Further, the standardized intensity of the LP 21 mode light is 0.0001 at a specific position on the outer peripheral surface side of the clad 12 with respect to the specific outer position Ro 1 described above. This position is the specific outer position Ro 2.
  • FIG. 6 is a view showing the concentration distribution of the active element in the amplification optical fiber 10 of the present embodiment in the same manner as FIG.
  • an active element is added to a region from the specific inner position Ri 2 to the specific outer position Ro 1, and the specific inner position from the center point C of the core 11. No active element is added to the region up to Ri 2 .
  • an active element is added between the specific inner position Ri 1 and the specific inner position Ri 2 that are part of a region where the intensity of the LP 11 mode light is greater than the intensity of the LP 01 mode light. Absent.
  • the average concentration of the active element from the specific inner position Ri 1 to the specific outer position Ro 1 of the LP 11 mode light is the center point of the core. It is higher than the average concentration of the active element from C to the specific inner position Ri 1 .
  • an active element is added between the specific outer position Ro 1 and the specific outer position Ro 2 that are part of a region where the light intensity of the LP 21 mode is larger than the light intensity of the LP 01 mode. It has not been.
  • the average concentration of the active element from the specific inner position Ri 2 to the specific outer position Ro 2 of the LP 21 mode light is the center point of the core. higher than the average concentration of the active elements in the C to a certain inside position Ri 2.
  • the amplification factor of the LP 11 mode light and the LP 21 mode light can be made larger than the amplification factor of the LP 01 mode light.
  • FIG. 7 is a view showing the concentration distribution of the active element in the amplification optical fiber 10 of the present modification as in FIG. 2D.
  • the active element is added to the region from the specific inner position Ri 2 to the specific outer position Ro 1
  • An active element is added to the region up to Ro 2 .
  • the average concentration of the active elements in the specified position inside Ri 1 of LP 11 mode of light to a certain position outside Ro 1 is higher than the average concentration of the active element in the center point C of the core to a certain inside position Ri 1.
  • the average concentration of the active elements in the specified position inside Ri 2 of LP 21 mode of light to a certain position outside Ro 2 are identified inside position Ri from the central point C of the core It is higher than the average concentration of active elements up to 2 .
  • the amplification factor of the LP 21 mode light can be further increased.
  • FIG. 8 is a view showing the concentration distribution of the active element in the amplification optical fiber 10 of the present modification as in FIG. 2D.
  • the active element is added to the region from the specific inner position Ri 2 to the specific outer position Ro 1
  • An active element is added to the region up to Ro 1 .
  • the average concentration of the active elements in the specified position inside Ri 1 of LP 11 mode of light to a certain position outside Ro 1 is higher than the average concentration of the active element in the center point C of the core to a certain inside position Ri 1.
  • the average concentration of the active elements in the specified position inside Ri 2 of LP 21 mode of light to a certain position outside Ro 2 are identified inside position Ri from the central point C of the core It is higher than the average concentration of active elements up to 2 .
  • the amplification factor of the LP 11 mode light can be further increased.
  • FIG. 9 is a view showing the concentration distribution of the active element in the amplification optical fiber 10 of the present modification as in FIG. 2D.
  • the active element is added to the region from the specific inner position Ri 2 to the specific outer position Ro 1
  • An active element is added to the region up to Ro 2 .
  • the average concentration of the active elements in the specified position inside Ri 1 of LP 11 mode of light to a certain position outside Ro 1 is higher than the average concentration of the active element in the center point C of the core to a certain inside position Ri 1.
  • the average concentration of the active elements in the specified position inside Ri 2 of LP 21 mode of light to a certain position outside Ro 2 are identified inside position Ri from the central point C of the core It is higher than the average concentration of active elements up to 2 .
  • the LP 11 mode light amplification factor and the LP 21 mode light amplification factor can be further increased.
  • FIG. 10 is a view showing the concentration distribution of the active element in the amplification optical fiber 10 of the present modification as in FIG. 2D.
  • the active element is not added to the core 11, the active element is added to an area from the outer peripheral surface IF of the core 11 to a certain position outside Ro 2.
  • the average concentration of the active elements in the specified position inside Ri 1 of LP 11 mode of light to a certain position outside Ro 1 is higher than the average concentration of the active element in the center point C of the core to a certain inside position Ri 1.
  • the average concentration of the active elements in the specified position inside Ri 2 of LP 21 mode of light to a certain position outside Ro 2 are identified inside position Ri from the central point C of the core It is higher than the average concentration of active elements up to 2 .
  • the active element is not added to the region from the center point C to the specific inner position Ri 2 as described above, and the region from the specific inner position Ri 2 to the specific outer position Ro 1 is not added.
  • the amplification factor of light in the LP 11 mode and the amplification factor of light in the LP 21 mode can be made larger than the amplification factor of light in the LP 01 mode.
  • LP 01 mode light, LP 11 mode light, and LP 21 mode light are input to the incident end 20.
  • the LP 11 mode light and the LP 21 mode light are amplified with a higher amplification factor than the LP 01 mode light and are emitted from the emission end 50.
  • an active element having a low average concentration may be added to at least a part of the region from the center point C of the core 11 to the specific inner position Ri.
  • the concentration distribution in which the average concentration of the active element in the region from the specific inner position Ri to the specific outer position Ro is higher than the average concentration of the active element from the center point C of the core 11 to the specific inner position Ri is satisfied.
  • the amplification factor of the LP 11 mode light can be made larger than the amplification factor of the LP 01 mode light.
  • the active element is not added to the core 11, and the active element is added to the region from the outer peripheral surface IF of the core 11 to the specific outer position Ro.
  • the above-described concentration distribution is satisfied in which the average concentration of the active element in the region from the specific inner position Ri to the specific outer position Ro is higher than the average concentration of the active element from the center point C of the core 11 to the specific inner position Ri.
  • an active element having a low average concentration may be added to at least a partial region of the core 11.
  • a low concentration active element is added to at least a part of the region from the center point C of the core 11 to the specific inner position Ri 1. May be.
  • the following density distribution needs to be satisfied in the second embodiment and the first to third modifications of the second embodiment.
  • LP 21 mode the highest order higher-order mode
  • the core is moved from the specific inner position Ri 2 when focusing on the light of the highest order higher order mode (LP 21 mode) used for communication propagating through the core 11. Focusing on LP 11 mode light propagating through the core from the center point of the core 11 in all regions up to the specific outer position Ro 2 when focusing on the light of the highest order higher order mode used for propagating communication In this case, the concentration distribution in which the active element is added at a concentration higher than the average concentration of the active element up to the specific inner position Ri 1 is satisfied.
  • a particular inner position Ri 1 where definitive if attention is paid to the LP 11 mode propagating through the core 11 of light, if attention is paid to the LP 11 mode propagating through the core 11 of light From the average concentration of the active element up to the specific inner position Ri 1 when focusing on the LP 11 mode light propagating through the core 11 from the center point C of the core 11 in all regions between the specific outer position Ro 1 The concentration distribution in which the active element is added at a high concentration is satisfied.
  • the highest order higher order used for communication propagating through the core 11 from the specific inner position Ri 1 when focusing on the LP 11 mode light propagating through the core 11.
  • Identification when focusing on LP 11 mode light propagating from the center point C of the core 11 to the core 11 in all regions up to the specific outer position Ro 2 when focusing on mode (LP 21 mode) light The concentration distribution in which the active element is added at a concentration higher than the average concentration of the active element up to the inner position Ri 1 is satisfied.
  • a low concentration active element may be added to at least a partial region of the core 11. Also, part of the region to a specific position outside Ro from certain inside position Ri of the first embodiment, a part of the region from a particular inner position Ri 2 to a certain position outside Ro 1 of the second embodiment, the second embodiment A part of the region from the specific inner position Ri 2 to the specific outer position Ro 2 in the first modified example, and one region from the specific inner position Ri 1 to the specific outer position Ro 1 in the second modified example of the second embodiment. In some regions from the specific inner position Ri 1 to the specific outer position Ro 2 in the third region of the second modification of the second embodiment, no active element is added or a low concentration of the active element is added. May be.
  • the average concentration of the active element from the specific inner position to the specific outer position is the center point C of the core 11.
  • the concentration distribution that is higher than the average concentration of the active element from the position to the specific inner position is satisfied, and the amplification factors of all higher-order modes used for communication are higher than the amplification factors of the light in the fundamental mode (LP 01 mode). Is also enlarged.
  • FIG. 11 is a diagram showing another example of the amplification optical fiber.
  • the outer periphery of the cladding 12 is circular.
  • the outer periphery of the cladding 12 is preferably polygonal.
  • the cross-sectional shape of the clad 12 is circular, the excitation light continues to be reflected at a certain angle at the interface between the clad 12 and the outer clad 13, and the skew light propagating through the clad 12 without the excitation light entering the core 11 is generated. It is likely to occur. Therefore, as in the present example, the clad 12 is polygonal so that the skew light can be suppressed, and the active element added to the core 11 can be excited efficiently.
  • the core 11 demonstrated one example, ie, the single core amplification optical fiber.
  • the core 11 may be plural.
  • FIG. 12 is a diagram illustrating a multi-core amplification optical fiber.
  • the core 11 is disposed at the center of the cladding 12, and a plurality of cores 11 are disposed around the core 11. That is, the core 11 is arranged 1-6.
  • this is an example in which a plurality of cores 11 are provided, and the arrangement of the plurality of cores 11 is not particularly limited.
  • at least the LP 01 mode light and the LP 11 mode light propagate through each core 11.
  • the concentration distribution of the active element is the same as that of the first embodiment and the modification thereof in each core 11 and the cladding 12 in the vicinity of the core 11.
  • LP 21 mode light may further propagate through each core 11.
  • the concentration distribution of the active element is the same as that in the second embodiment or the clad 12 in the vicinity of the core 11. This is the same as the modification.
  • pump light is incident on the clad 12 and signal light similar to that in the above embodiment is incident on each core 11.
  • FIG. 13 is a diagram showing another example of an optical fiber for multicore amplification. As shown in FIG. 13, it is preferable that the outer periphery of the cladding 12 is also a polygon in the multi-core amplification optical fiber. In this case, similarly to the description in FIG. 11, skew light can be suppressed, and the active element added to the core 11 can be excited efficiently.
  • the amplification optical fiber is a double-clad fiber having an outer cladding.
  • the amplification optical fiber may not be a double clad fiber. In this case, a structure in which excitation light is incident on the core 11 may be used.
  • the present invention is not limited to this, and higher-order mode light may be amplified by the amplification optical fiber.
  • the average concentration of the active element from the specific inner position to the specific outer position is The concentration distribution that is higher than the average concentration of the active element from the center point C to the specific inner position is satisfied, and the amplification factors of all the higher-order mode light used for communication are fundamental mode (LP 01 mode) light. It is made larger than the amplification factor.
  • LP 01 mode fundamental mode
  • light to be amplified is LP 01 mode light and LP 11 mode light used for communication, LP 01 mode light used for optical communication, LP 11 mode.
  • light in the LP 21 mode are preferable because even mode higher order light, such as the LP 02 mode, is not subject to amplification.
  • Example 1 The same amplification optical fiber as the amplification optical fiber shown in FIG. 2 was measured. Therefore, in this amplification optical fiber, the refractive index distribution of the core is constant in the radial direction, and the normalized intensity of the LP 11 mode light is larger than the normalized intensity of the LP 01 mode light only. An active element is added.
  • the theoretical cutoff wavelength ⁇ c of the LP 21 mode light is 1.40 ⁇ m and 1.50 ⁇ m
  • the ratio ⁇ is independent of the effective core area A eff of the LP 01 mode light, regardless of whether the theoretical cutoff wavelength ⁇ c of the LP 21 mode light is 1.40 ⁇ m or 1.50 ⁇ m.
  • 11 / ⁇ 01 was approximately 1.7. Therefore, in the amplification optical fiber 10 shown in FIG. 2, the amplification factor of the LP 11 mode light is larger than the amplification factor of the LP 01 mode light. Therefore, according to the amplification optical fiber 10 shown in FIG. 2, it was shown that the amplification factor of the LP 11 mode light can be made larger than the amplification factor of the LP 01 mode light.
  • Example 2 The same amplification optical fiber as the amplification optical fiber shown in FIG. 4 was measured. Therefore, in this amplification optical fiber, the refractive index distribution of the core is constant in the radial direction, and the active element is added only to the cladding.
  • this amplification optical fiber in the same manner as in the first embodiment, when the theoretical cutoff wavelength ⁇ c of the LP 21 mode light is 1.40 ⁇ m and 1.50 ⁇ m, the LP 01 mode light in the light of 1.55 ⁇ m wavelength is obtained.
  • the ratio ⁇ is independent of the effective core area A eff of the LP 01 mode light regardless of whether the theoretical cutoff wavelength ⁇ c of the LP 21 mode light is 1.40 ⁇ m or 1.50 ⁇ m.
  • 11 / ⁇ 01 was approximately 3. Therefore, in the example shown in FIG. 4, the amplification factor of the light in the LP 11 mode is larger than the amplification factor of the light in the LP 01 mode, compared to the example shown in FIG. Therefore, according to the amplification optical fiber 10 shown in FIG. 4, it is shown that the amplification factor of the LP 11 mode light can be made larger than the amplification factor of the LP 01 mode light.
  • an optical fiber for amplification capable of amplifying higher-order mode light than fundamental mode light is provided, and is expected to be used in the field of optical communication.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Lasers (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Abstract

L'invention concerne une fibre optique (10) d'amplification, dans laquelle, concernant la lumière d'un mode d'ordre supérieur spécifique se propageant à travers une âme (11), la concentration moyenne d'un élément actif de la position intérieure spécifique (Ri) à la position extérieure spécifique (Ro) est supérieure à la concentration moyenne de l'élément actif du point central (C) d'une âme (11) à la position intérieure spécifique (Ri) pour la lumière de tout mode d'ordre supérieur qui est utilisé pour la communication et qui se propage à travers l'âme (11), la position intérieure spécifique (Ri) étant la position la plus intérieure à laquelle l'intensité normalisée de la lumière du mode LP01 et l'intensité normalisée de la lumière du mode d'ordre supérieur spécifique sont appariées dans la direction radiale, et la position extérieure spécifique (Ro) étant la position la plus extérieure à laquelle l'intensité normalisée de la lumière du mode d'ordre supérieur spécifique est égale à 0,0001, et le facteur d'amplification pour la lumière de tous les modes d'ordre supérieur servant pour la communication étant supérieur au facteur d'amplification pour la lumière du mode basique.
PCT/JP2017/037515 2017-01-27 2017-10-17 Fibre optique d'amplification WO2018138982A1 (fr)

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JPWO2022039073A1 (fr) * 2020-08-17 2022-02-24
JPWO2022157896A1 (fr) * 2021-01-21 2022-07-28
JPWO2023195155A1 (fr) * 2022-04-08 2023-10-12
WO2025053231A1 (fr) * 2023-09-07 2025-03-13 古河電気工業株式会社 Fibre multicœur, coupleur optique et amplificateur optique

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JP7214527B2 (ja) * 2019-03-26 2023-01-30 古河電気工業株式会社 マルチコア光増幅ファイバ、マルチコア光ファイバ増幅器および光通信システム
JP7136534B2 (ja) 2019-05-07 2022-09-13 株式会社豊田中央研究所 光ファイバレーザ装置

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JPWO2023195155A1 (fr) * 2022-04-08 2023-10-12
WO2023195155A1 (fr) * 2022-04-08 2023-10-12 日本電信電話株式会社 Amplificateur à fibre optique
WO2025053231A1 (fr) * 2023-09-07 2025-03-13 古河電気工業株式会社 Fibre multicœur, coupleur optique et amplificateur optique

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