WO2022134663A1 - 一种多芯光纤、传输系统和多芯光纤扩容方法 - Google Patents

一种多芯光纤、传输系统和多芯光纤扩容方法 Download PDF

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WO2022134663A1
WO2022134663A1 PCT/CN2021/117762 CN2021117762W WO2022134663A1 WO 2022134663 A1 WO2022134663 A1 WO 2022134663A1 CN 2021117762 W CN2021117762 W CN 2021117762W WO 2022134663 A1 WO2022134663 A1 WO 2022134663A1
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core
fiber
cores
central
optical fiber
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PCT/CN2021/117762
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English (en)
French (fr)
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张文斗
柏云龙
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华为技术有限公司
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    • 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
    • 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
    • G02B6/02042—Multicore optical fibres
    • 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
    • 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
    • H04B10/2569—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to polarisation mode dispersion [PMD]
    • 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
    • H04B10/2581—Multimode transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor

Definitions

  • the invention relates to the technical field of optical fibers, in particular to a multi-core optical fiber, a transmission system and a method for expanding the capacity of the multi-core optical fiber.
  • SDM Space-division multiplexing
  • MIMO multiple input multiple output
  • the embodiments of the present application provide a multi-core optical fiber, a transmission system, and a method for expanding the capacity of the multi-core optical fiber.
  • the present application provides a multi-core optical fiber, comprising: a central fiber core disposed at the center of the multi-core optical fiber; at least two sets of non-central fiber cores, respectively disposed around the central fiber core, and each The distances between each non-central core in the set of non-central cores and the central core are equal, between the central core and any set of non-central cores, and between each set of non-central cores,
  • the transmitted energy has no crosstalk or weak crosstalk; each group of non-central fiber cores includes at least two non-central fiber cores, and the transmitted energy crosstalks each other between the at least two non-central fiber cores in each group.
  • the transmitted energy is free from crosstalk between the central core and any set of surrounding cores and between each set of surrounding cores, so that the multi-core fiber designed in the present application can support smooth transition from single-mode fiber. Upgrade to multi-core fiber, thus protecting the investment of customer fiber and old network equipment; by allowing each group of surrounding fiber cores to include at least two fiber cores, and the energy crosstalk transmitted between each fiber core in the group, so as to improve multi-core The number of channels and bandwidth of the fiber, and solve the problem of large dispersion between modes.
  • the refractive index differs between the central core and the non-central cores in each set of non-central cores.
  • the transmission between the central core and any set of surrounding cores, and between each set of surrounding cores is Energy without crosstalk.
  • the refractive indices of the non-central cores in each set of non-central cores are the same.
  • the difference in refractive index between each set of non-central cores is less than 0.002.
  • the refractive index of the first group of non-central fiber cores and the refractive index of the second group of non-central fiber cores are the same, and the at least two groups of non-central fiber cores include the first group of non-central fiber cores and the second set of non-central fiber cores.
  • the crosstalk between the two groups is relatively small, and the two groups can have the same fiber cores, thereby simplifying the internal structure of the multi-core fiber and reducing the multi-core cost of fiber.
  • the present application provides a multi-core optical fiber, comprising: a central core disposed at the center of the multi-core optical fiber; four sets of non-central optical cores, respectively disposed around the central core, and each The distances between each non-central core in the set of non-central cores and the central core are equal, between the central core and any set of non-central cores, and between each set of non-central cores,
  • the transmitted energy has no crosstalk or weak crosstalk; each set of non-central fiber cores includes two non-central fiber cores, and the transmitted energy crosstalks each other between the two non-central fiber cores.
  • the 4 groups of non-central fiber cores are respectively arranged on the outer frame of the four sides of the 4 ⁇ 4 matrix, and the 2 non-central fiber cores of each group are respectively arranged at the middle two nodes superior.
  • the present application provides a transmission system, comprising: at least two optical terminal multiplexers OTM, at least two optical line amplifiers OLA, and at least one multi-core optical fiber that may be implemented as in the first aspect or as in the second aspect Various possible implementations of multi-core fibers.
  • the present application provides a multi-core optical fiber expansion method, which is applied to a single-mode optical fiber transmission system.
  • the single-mode optical fiber transmission system includes at least two optical terminal multiplexers OTM, at least two optical line amplifiers OLA and at least one single-mode fiber, wherein each OTM includes at least one optical repeater unit OTU and at least one wavelength multiplexer/demultiplexer, and each OLA includes at least one single-mode fiber amplifier, including: constructing a multi-core fiber transmission
  • the multi-core optical fiber transmission link is obtained by setting a multi-core optical fiber amplifier at both ends of the multi-core optical fiber, and then connecting the fan-in/fan-out devices to the multi-core optical fiber amplifier respectively; add at least Two sets of space-division OTUs and at least two sets of space-division wavelength multiplexers/demultiplexers, or at least two new sets of OTUs and at least two sets of wavelength multiplexers/demultiplexers; the single-mode optical fiber transmission system At least two wavelength multiplexers
  • FIG. 1 is a schematic cross-sectional view of a multi-core optical fiber provided by an embodiment of the present application
  • FIG. 2 is a schematic diagram of the relationship between each core in a multi-core optical fiber provided by an embodiment of the present application;
  • FIG. 3 is a schematic diagram of the refractive index relationship of each core in a multi-core optical fiber provided by an embodiment of the present application;
  • FIG. 4 is a schematic diagram of five intra-group modes of a multi-core optical fiber provided by an embodiment of the present application.
  • FIG. 5 is a schematic structural diagram of a multi-core optical fiber transmission system according to an embodiment of the present application.
  • FIG. 6(a) is an architecture diagram of an existing single-mode optical fiber transmission system provided by an embodiment of the present application.
  • FIG. 6(b) is a schematic diagram of constructing a multi-core optical fiber transmission link according to an embodiment of the present application.
  • FIG. 6(c) is a schematic diagram of constructing a multi-core optical fiber transmission system provided by an embodiment of the present application.
  • FIG. 6(d) is an architecture diagram of a multi-core optical fiber transmission system provided by an embodiment of the present application.
  • FIG. 7(a) is a schematic diagram of the transmission of the central core in the multi-core optical fiber provided by the embodiment of the present application.
  • FIG. 7(b) is a schematic diagram of the expansion of two groups of surrounding cores in the multi-core optical fiber provided by the embodiment of the present application during transmission;
  • Figure 7(c) is a schematic diagram of four groups of surrounding fiber cores in the multi-core optical fiber provided by the embodiment of the present application during transmission;
  • FIG. 8 is a flowchart of a method for expanding the capacity of a multi-core optical fiber according to an embodiment of the present application.
  • the embodiment of the present application provides a multi-core optical fiber
  • the multi-core optical fiber includes a central core and at least two sets of non-central cores (hereinafter, the cores disposed at the non-central positions are referred to as "peripheral cores")
  • Each set of surrounding fiber cores includes at least two surrounding fiber cores.
  • the central fiber core is located at the center of the entire multi-core fiber, and at least two groups of surrounding fiber cores are respectively arranged around the central fiber core according to certain rules, and the distances between each group of surrounding fiber cores and the central fiber core are equal.
  • the transmitted energy has no crosstalk or crosstalk is very weak, so that the multi-core fiber designed in this application can support the transmission from single-mode fiber Smooth upgrade to multi-core fiber, so as to protect the investment of customer fiber and old network equipment; by allowing each group of surrounding fiber cores to include at least two fiber cores, and the energy crosstalk transmitted between each fiber core in the group, thereby improving the multi-core.
  • the number of channels and bandwidth of the core fiber and solve the problem of large dispersion between modes.
  • the structure and performance of the multi-core optical fiber provided by the embodiments of the present application will be described in detail below through several embodiments. It should be noted that the following uses an optical fiber with 9 cores (that is, a central core and 8 surrounding cores) as an example to describe the multi-core optical fiber to be protected in this application.
  • the core fiber is not limited to 9 cores, and can be any number of cores, which is not limited in this application.
  • FIG. 1 is a schematic cross-sectional view of a multi-core optical fiber provided by an embodiment of the present application.
  • the multi-core optical fiber provided by the present application includes 9 cores (Core0-Core8).
  • the core (Core 0) located at the center of the multi-core fiber is called the central core
  • the 8 cores (Core1-Core8) located around the core (Core 0) are called the surrounding cores.
  • the central core (Core0) in order to have no coupling with other surrounding cores (Core0-Core8), a channel layer with a low refractive index is provided to suppress crosstalk with the surrounding cores (Core0-Core8). question.
  • the central core (Core0) is doped with germanium to make its optical performance compatible with the optical parameters of the existing standard single-mode fiber (ITU-T G.652 standard), so that the central core (Core0) can be compatible with other Optical fibers with a central core are connected for signal transmission.
  • the “coupling” proposed here refers to the mutual crosstalk between the electric fields generated by two or more cores when transmitting optical signals; “uncoupling” refers to the transmission of two or more cores When the optical signal is used, the generated electric fields have no crosstalk with each other, or the crosstalk CT ⁇ -30dB/100km.
  • the 8 surrounding fiber cores are arranged around the central fiber core (Core0) according to different spacings according to the needs of the coupling characteristics.
  • 8 surrounding fiber cores are located on the middle nodes of the equally spaced 4 ⁇ 4 matrix frame, and the surrounding fiber cores (Core2, Core3) are located in the middle two of one side of the matrix.
  • the surrounding fiber cores are located on the middle two nodes on one side of the matrix, the surrounding fiber cores (Core6, Core7) are located on the middle two nodes on one side of the matrix, and the surrounding fiber cores (Core1, Core8) Located on the middle two nodes of one side of the matrix.
  • the spacing of the 4 ⁇ 4 matrix is about 25 ⁇ m, so the distance between the surrounding cores (Core1-Core8) and the central core (Core0) is about 39.53 ⁇ m, and the distance between the two surrounding cores on the same side About 25 ⁇ m, the distance between surrounding cores on adjacent sides is about 35.36 ⁇ m and 55.9 ⁇ m, and the distance between surrounding cores on opposite sides is about 75 ⁇ m.
  • the intervals between the nodes in the 4 ⁇ 4 matrix in the above Figure 2 are all equal. In practical applications, the distances can be different. For example, the distance between the two middle nodes can be smaller than that between the middle node and the side nodes. The distance between the two cores in the group enables better coupling between the two cores.
  • the refractive index of the 8 surrounding cores can be set.
  • the refractive index between the core (Core1) and the surrounding cores (Core8) is the same, while the central core (Core0), surrounding cores (Core2, Core3), surrounding cores (Core4, Core5), surrounding cores (Core6,
  • the refractive index between Core7) and surrounding cores (Core1, Core8) is different, and by generating differences, the central core (Core0), the surrounding cores (Core2, Core3), the surrounding cores (Core4, Core5), the surrounding cores (Core4, Core5), the surrounding The core (
  • the refractive index of the central core (Core0) is higher than that of any of the surrounding cores, and the surrounding cores (Core2, Core3), surrounding cores (Core4, Core5), surrounding cores (Core6, Core7) and The difference in refractive index between any two groups of surrounding fiber cores in the surrounding fiber cores (Core1, Core8) must satisfy the problem of no significant crosstalk caused by coupling between the fiber cores.
  • the surrounding cores (Core2, Core3) and the surrounding cores (Core6, Core7) are relatively far, the crosstalk between them is relatively weak, so the surrounding cores (Core2, Core3) can be
  • the core (Core6, Core7) selects the core with the same refractive index.
  • the surrounding cores (Core4, Core5) and the surrounding cores (Core1, Core8) also use cores with the same refractive index, thereby simplifying the internal structure of the multi-core fiber and reducing the cost of the multi-core fiber.
  • the parameters of constructing a multi-core fiber that meets the requirements are shown in Figure 3.
  • the 9 cores (Core0-Core8) in the multi-core fiber have a radius of 4.8 ⁇ m, and the channel around each core is The outer ring radius of the layer is 12 ⁇ m, the channel width is 7.2 ⁇ m, the cladding outside each core is doped with fluorine, and its refractive index is 1.439; the channel layer of each core is also doped with fluorine, and its refractive index is 1.435.
  • the material of the central core (Core0) is SiO2 doped with a small amount of germanium, and its refractive index is 1.446, and the material of the surrounding cores (Core1-Core8) is pure SiO2, and its refractive index is 1.444. Since the present application needs to group 8 surrounding cores (Core1-Core8), the difference between the refractive indices of the channel layers of the surrounding cores of the four groups is about 0.2%.
  • the surrounding cores (Core1-Core8) into 4 groups, 4 groups of surrounding cores are obtained, and adding the central core (Core0), so that the multi-core fiber of this application has five intergroup modes.
  • the modes between different groups are uncoupled or weakly coupled.
  • the crosstalk between the two groups of surrounding cores as an example, assuming that the electric fields of the inter-group modes of the surrounding cores of the p-th group and the surrounding cores of the q-th group are Ep and Eq, respectively, then the inter-group modes of the two groups are The coupling coefficient k pq is:
  • ⁇ is the angular frequency
  • ⁇ 0 is the vacuum permittivity
  • n is the refractive index distribution of the fiber cross-section
  • nq is the refractive index distribution of the core cross-section in the intergroup mode of the qth group
  • Hp is the intergroup mode of the qth group. the magnetic field.
  • the power coupling coefficient hpq of the inter-group modes of the two groups is:
  • Kpq is the average value of kpq and kqp
  • d is the correlation length
  • ⁇ ′ pq represents the difference in the transmission constants of the inter-group modes of the two groups.
  • each group of coupling cores composed of 8 surrounding cores is grouped in pairs.
  • the modes in each group will be coupled with each other during long-distance transmission, and each mode has spatial mode dispersion ( spatial mode dispersion, SMD).
  • SMD spatial mode dispersion
  • SMD is the pulse broadening caused by the different transmission speeds of different modes. Changes in SMD within groups. Under different structural parameters, after calculating the effective refractive index of each mode, formula (4) is used to calculate the SMD within the group, where formula (4) is specifically:
  • L is the fiber length
  • h is the mode coupling coefficient
  • c is the speed of light in vacuum
  • ⁇ is the mode transmission constant difference
  • k is the wave number.
  • the multi-core fiber designed in this application has a central core and 8 surrounding cores, and the 8 surrounding cores are grouped into two groups to generate four groups of cores, and the cores in the group are randomly coupled, so that the design of the application
  • the multi-core fiber can support the smooth upgrade from single-mode fiber to multi-core fiber, thus protecting customers' investment in fiber and old network equipment. Moreover, the number of channels and bandwidth of multi-core fibers are increased, and the problem of large dispersion between modes is solved.
  • FIG. 5 is a schematic structural diagram of a multi-core optical fiber transmission system according to an embodiment of the present application.
  • the system includes N optical terminal multiplexers (OTM) 501, M optical line amplifiers (OLA) 502 and L optical fibers 503, and N and M are greater than 2 is a positive integer, and L is a positive integer greater than 3.
  • OTM 501 is connected to the OLA 502 through an optical fiber
  • one end of each OLA 502 is connected to the OTM 501
  • the other end is connected to one end of another OLA 502.
  • the OTM 501 includes an optical transponder unit (OTU) 5011, a wavelength multiplexer/demultiplexer (W Mux/W DMux) 5012, and a fan-in/fan-out device 5013.
  • OTU optical transponder unit
  • W Mux/W DMux wavelength multiplexer/demultiplexer
  • fan-in/fan-out device 5013 fan-in/fan-out device
  • OTU 5011 can be divided into existing single wavelength or frequency super channel OTU and space super channel OTU.
  • the existing single-wavelength or frequency super-channel OTU is connected to one fiber channel to support two polarization modes transmission;
  • the spatial super-channel OTU is connected to a group of fiber channels (the number of channels is not less than 2), and each group of fiber channels includes two polarization modes. mode, and then receive demodulation through 2N ⁇ 2N MIMO technology (N is the number of fiber channels in each group).
  • the wavelength division multiplexer/demultiplexer is used to multiplex the light of different wavelength signals of multiple ports into one fiber core or demultiplex the multiple wavelength signals received from one fiber core to multiple port outputs.
  • Fan-in/fan-out devices are used to multiplex the intermediate core and multiple groups of surrounding cores surrounding the intermediate core into a multi-core fiber, or to decompose the signals of multiple cores in a multi-core fiber. Multiplexed into an intermediate core and multiple grouped outputs on surrounding cores.
  • the OLA 502 includes a pair of amplifiers 5021, which are respectively used to amplify the optical signals in the upstream and downstream optical fibers.
  • the amplifier 5021 can amplify the optical signals in multiple cores in a concentrated manner, or amplify the signals in the middle cores in the multi-core optical fiber and the cores of the surrounding core groups respectively through a fan-in and fan-out device.
  • the amplifier 5021 can be classified into a single-mode fiber amplifier and a multi-core fiber amplifier. If connecting with single-mode fiber, use single-mode fiber amplifier; if connecting with multi-core fiber, use multi-core fiber amplifier.
  • the optical fiber 503 can be a single-mode optical fiber or a multi-core optical fiber.
  • the single-mode optical fiber is an optical fiber that can only transmit one mode
  • the multi-core optical fiber is an optical fiber including multiple cores
  • the multi-core optical fiber used in this application is the above-mentioned FIG. 1-FIG. .
  • 6(a)-(d) are diagrams of the evolution process from single-mode optical fiber smoothing to multi-core optical fiber provided by the embodiments of the present application.
  • an existing single-mode optical fiber transmission system includes two OTMs, two OLAs (including two single-mode optical fiber amplifiers) and single-mode optical fibers.
  • one OTM is deployed at the near end (take the left OTM as an example, the same below), and the other OTM is deployed at the far end (take the right OTM as an example, the same below).
  • the demultiplexer is connected to an OLA through a single-mode fiber to compensate for fiber attenuation, and then the OLAs at both ends are connected to the single-mode fiber between the near-end and the far-end respectively, thereby constructing a single-mode fiber transmission system.
  • the optical signal is sent by the near-end OTM, it is transmitted to the far-end OTM through the near-end OLA, single-mode fiber, and the far-end OLA; After and the proximal OLA, transfer to the proximal OTM.
  • the multi-core fiber amplifiers are respectively connected at both ends of the multi-core fiber between the near end and the far end, and then the multi-core fiber amplifiers at the near end and the far end are connected.
  • a fan-in/fan-out device is respectively connected to the core fiber amplifier to form a multi-core fiber transmission link. If the near-end fan-in/fan-out device receives the optical signals sent by multiple optical fibers, it will multiplex the optical signals sent by the multiple optical fibers, so that the optical signals sent by multiple optical fibers can be transmitted to the near-end OLA, multiple optical fibers, and multiple optical fibers. After the core fiber and the remote OLA, the remote fan-in/fan-out device demultiplexes the received optical signal, and then sends it out.
  • the above multi-core fiber consists of five groups, the first group is located in the center of the fiber, has only one core, and is compatible with standard single-mode fiber performance; around the first group, there are four groups, each of which includes at least 2 a homogeneous core.
  • the link performance of each packet needs to be obtained through necessary testing methods, including but not limited to optical signal-to-noise ratio, dispersion, polarization mode dispersion/modal dispersion, nonlinear noise, etc.
  • a multi-core fiber transmission system in constructing a multi-core fiber transmission system, according to the grouping of the connected multi-core fibers, if the near-end and far-end fan-in/fan-out devices divide the 9 cores in the multi-core fiber into When one single-mode fiber and four two-core fibers (one two-core fiber is used as an example in the figure), connect one single-mode fiber and four two-core fibers to the near-end and far-end fan-in/fan-out devices Fiber, single-mode fiber is connected to the center core in a multi-core fiber, and two-core fiber is connected to the surrounding cores of each group; if the fan-in/fan-out devices at the near and far When divided into 9 single-mode fibers, connect 9 single-mode fibers to the near-end and far-end fan-in/fan-out devices.
  • the input/output ends of the wavelength division multiplexer/demultiplexer of the original single-mode fiber transmission system are respectively switched to the near-end fan-in/fan-out devices on the newly deployed multi-core fiber transmission link, so as to realize the The central core connection of multi-core fibers; then add OTUs with space division multiplexing characteristics, space division wavelength division multiplexers/demultiplexers and other devices at the near and far ends (if divided into 9 single-mode fibers, then Add devices such as OTU, wavelength division multiplexer/demultiplexer, etc. at the near end and the far end, and connect to the fan-in/fan-out devices at the near end and the far end to realize integration with other cores (non-central fibers). core) connection to expand the transmission capacity.
  • the near-end WDM/demultiplexer and/or the space-division WDM/demultiplexer fan-in/fan to the near-end After the output device sends the optical signal, the fan-in/fan-out device at the near end will multiplex the optical signal sent by the fiber, so that the optical signal sent by the multiple fibers can be transmitted through the multi-core fiber, and then the multiplexed optical signal can be transmitted through the multi-core fiber.
  • the optical signal passes through the near-end OLA, the multi-core fiber, the far-end OLA and the far-end fan-in/fan-out device; the far-end fan-in/fan-out device demultiplexes the received optical signal, and demultiplexes the received optical signal.
  • the signals are respectively transmitted to the corresponding remote wavelength division multiplexer/demultiplexer and/or space division wavelength division multiplexer/demultiplexer, thereby realizing signal transmission.
  • the center fiber (Core0) passes through the fan-in/fan-out device and the wave
  • the demultiplexer/demultiplexer is used for optical signal transmission, while other surrounding cores (Core1-Core8) are temporarily idle; if there is also a set of space division wavelength division multiplexers/demultiplexers to transmit Signal, as shown in Figure 7(b), compared with the single-mode fiber transmission system, the expansion supports 2-core space super-channel transmission.
  • the surrounding cores (Core1, Core8) are transmitted from the near end to the far end signal, the surrounding fiber cores (Core2, Core3) transmit signals from the far end to the near end; if there are two sets of space division wavelength division multiplexers/demultiplexers at the same time to send optical signals, as shown in Figure 7(c)
  • the expansion supports 4-core space super-channel transmission.
  • the surrounding fiber cores (Core1, Core8) and the surrounding fiber cores (Core4, Core5) transmit signals from the near end to the far end
  • the surrounding cores (Core2, Core3) and the surrounding cores (Core6, Core7) transmit signals from the far end to the near end; if there are two multi-core fibers, one multi-core fiber can transmit signals from the near end to the far end, and the other A multi-core optical fiber transmits signals from the far end to the near end, thereby realizing capacity expansion to support 8-core space super-channel transmission.
  • FIG. 8 is a flowchart of a method for expanding the capacity of a multi-core optical fiber according to an embodiment of the present application. As shown in Figure 8, the specific implementation process of the multi-core fiber expansion method is as follows:
  • Step S801 constructing a multi-core optical fiber transmission link.
  • the constructed multi-core fiber transmission link is shown in Figure 6(b), and the multi-core fiber amplifiers are respectively connected at both ends of the multi-core fiber between the near end and the far end, and then the multi-core fiber amplifiers at the near end and the far end are connected.
  • a fan-in/fan-out device is respectively connected to the core fiber amplifier to form a multi-core fiber transmission link.
  • Step S803 adding at least two groups of space division OTUs and at least two groups of space division wavelength multiplexers/demultiplexers, or adding at least two groups of OTUs and at least two groups of wavelength multiplexers/demultiplexers.
  • the near-end and far-end fan-in/fan-out devices divide the 9 cores of the multi-core fiber into 1 single-mode fiber and 4 two-core fibers (a two-core fiber is used as an example in the figure), then Add at least two sets of space division OTUs and at least two sets of space division wavelength multiplexers/demultiplexers; if the near-end and far-end fan-in/fan-out devices divide the 9 cores in the multi-core fiber into 9 single When the mode fiber is used, at least two sets of OTUs and at least two sets of wavelength multiplexers/demultiplexers are added.
  • Step S805 cutting at least two wavelength multiplexers/demultiplexers in the single-mode optical fiber transmission system to the fan-in/fan-out devices in the multi-core optical fiber transmission link, respectively, to be connected with the multi-core optical fiber transmission link. and connecting the newly added at least two sets of space division wavelength multiplexers/demultiplexers or the newly added at least two sets of wavelength multiplexers/demultiplexers to the multi-core optical fiber transmission On fan-in/fan-out devices in the link, connecting to surrounding cores in multi-core fibers.
  • the existing single-mode fiber transmission system includes at least two optical terminal multiplexers OTM, at least two optical line amplifiers OLA and at least one single-mode fiber, wherein each OTM includes at least one optical repeater unit OTU and at least one A wavelength multiplexer/demultiplexer, each OLA including at least one single-mode fiber amplifier.
  • the input/output ends of the wavelength division multiplexer/demultiplexer of the original single-mode optical fiber transmission system are respectively switched to the near-end fan-in/fan-out devices on the newly deployed multi-core optical fiber transmission link
  • realize the connection with the central core of the multi-core fiber then add the OTU, space division wavelength division multiplexer/demultiplexer and other devices with space division multiplexing characteristics at the near end and the far end Mode fiber, add OTU, wavelength division multiplexer/demultiplexer and other devices at the near and far ends), connect to the fan-in/fan-out devices at the near and far ends, and realize the integration with other cores. (non-central core) connections to expand transmission capacity.

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Abstract

本申请提供了一种多芯光纤、传输系统和多芯光纤扩容方法，涉及光纤技术领域。其中，所述多芯光纤包括一个中心纤芯和至少两组非中心纤芯，每组非中心纤芯包括至少两个非中心纤芯。中心纤芯位于整个多芯光纤的正中心，至少两组非中心纤芯分别按照一定规则，设置在中心纤芯的周围，且每组非中心纤芯中的非中心纤芯与中心纤芯之间的距离相等。本申请中心纤芯与任意一组非中心纤芯之间、以及每组非中心纤芯之间，传输的能量无串扰或串扰很弱，使得多芯光纤支持从单模光纤平滑升级到多芯光纤，保护客户光纤和老网设备的投资；通过让每组非中心纤芯内每个纤芯之间，传输的能量串扰，从而提高多芯光纤的信道数量和带宽，并解决模式间色散大的问题。

Description

一种多芯光纤、传输系统和多芯光纤扩容方法
本申请要求于2020年12月21日提交中国国家知识产权局、申请号为202011523362.0、申请名称为“一种多芯光纤、传输系统和多芯光纤扩容方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及光纤技术领域，尤其涉及一种多芯光纤、传输系统和多芯光纤扩容方法。
背景技术
伴随着5G的商用和未来向6G的演进，光纤通信带宽需求将持续增长。然而，普通单芯单模光纤可支持的容量已经趋近香农极限，持续提升已遇到瓶颈。
空分复用(space-division multiplexing，SDM)技术被广泛认为是下一代光纤通信系统方向，弱耦合多芯光纤具有空间信道密度高，差分模式色散系数相对强耦合多芯光纤显著降低,并使接收端多路输入多路输出(multiple input multiple output，MIMO)解调复杂度大幅降低，所以SDM技术被认为是最具竞争力的演进方向。
但是，从商用角度，从单芯单模光纤到多芯光纤的演进，由于传输介质结构变化，会导致新老网络的对接兼容出现困难，运营商在维护老网络运行同时还需要新建全新的空分复用网络，从而面临巨大的投资资金周转困难。
从技术角度，走到空分复用阶段，为了避免因空分复用光纤结构切换带来多次的设备替代、割接以及潜在引入的兼容性问题。因此需要从多芯光纤一开始规划就要充分考虑如何利用光纤包层截面支持最多的纤芯数量和容量。而这与工程技术发展相矛盾，比如短期内受限MIMO均衡逻辑规模和功耗的限制，还不能支持超长距离弱耦合多芯传输系统应用。
发明内容
为了解决上述的问题，本申请的实施例提供了一种多芯光纤、传输系统和多芯光纤扩容方法。
第一方面，本申请提供一种多芯光纤，包括：中心纤芯，设置在所述多芯光纤的中心位置；至少两组非中心纤芯，分别设置在所述中心纤芯周围，且每组非中心纤芯中的各个非中心纤芯与所述中心纤芯之间的距离相等，所述中心纤芯与任意一组非中心纤芯之间、以及每组非中心纤芯之间，传输的能量无串扰或弱串扰；每组非中心纤芯包括至少两个非中心纤芯，每一组的所述至少两个非中心纤芯之间，传输的能量相互串扰。
在该实施方式中，通过让中心纤芯与任意一组周围纤芯之间、每组周围纤芯之间，传输的能量无串扰，使得本申请设计的多芯光纤可以支持从单模光纤平滑升级到多芯光纤，从而保护客户光纤和老网设备的投资；通过让每组周围纤芯包括至少两个纤芯，且组内每个纤芯之间，传输的能量串扰，从而提高多芯光纤的信道数量和带宽，并解决模式间色散大的问题。
在一种实施方式中，所述中心纤芯和所述每组非中心纤芯中的非中心纤芯之间的折射 率不同。
在该实施方式中，通过让中心纤芯、每组的周围纤芯之间的折射率不同，以实现中心纤芯与任意一组周围纤芯之间、每组周围纤芯之间，传输的能量无串扰。
在一种实施方式中，每一组非中心纤芯内各个非中心纤芯的折射率相同。
在一种实施方式中，每一组非中心纤芯之间的折射率的差值小于0.002。
在一种实施方式中，第一组非中心纤芯的折射率和第二组非中心纤芯的折射率相同，所述至少两组非中心纤芯包括所述第一组非中心纤芯和所述第二组非中心纤芯。
在该实施方式中，当两组周围纤芯之间的距离较远，两组之间的串扰比较小，可以让这两组的纤芯相同，从而简化了多芯光纤内部结构和降低多芯光纤的成本。
第二方面，本申请提供一种多芯光纤，包括：一个中心纤芯，设置在所述多芯光纤的中心位置；4组非中心纤芯，分别设置在所述中心纤芯周围，且每组非中心纤芯中的各个非中心纤芯与所述中心纤芯之间的距离相等，所述中心纤芯与任意一组非中心纤芯之间、以及每组非中心纤芯之间，传输的能量无串扰或弱串扰；每组非中心纤芯包括2个非中心纤芯，所述2个非中心纤芯之间，传输的能量相互串扰。
在一种实施方式中，所述4组非中心纤芯分别设置在4×4矩阵的四个侧面的外框上，且每组的所述2个非中心纤芯分别设置在中间两个节点上。
第三方面，本申请提供一种传输系统，包括：至少两个光终端复用器OTM、至少两个光线路放大器OLA和至少一个如第一方面各个可能实现的多芯光纤或如第二方面各个可能实现的多芯光纤。
第四方面，本申请提供一种多芯光纤扩容方法，应用在单模光纤传输系统上，所述单模光纤传输系统包括至少两个光终端复用器OTM、至少两个光线路放大器OLA和至少一个单模光纤，其中，每个OTM包括至少一个光转发器单元OTU和至少一个波长复用器/解复用器，每个OLA包括至少一个单模光纤放大器，包括：构建多芯光纤传输链路，所述多芯光纤传输链路通过在多芯光纤的两端分别设置一个多芯光纤放大器，然后分别在所述多芯光纤放大器上连接扇入/扇出器件得到的；新增至少两组空分OTU和至少两组空分波长复用器/解复用器，或新增至少两组OTU和至少两组波长复用器/解复用器；将所述单模光纤传输系统中至少两个波长复用器/解复用器分别切割到所述多芯光纤传输链路中的扇入/扇出器件上，与多芯光纤中的中心纤芯连接；和将新增的至少两组空分波长复用器/解复用器或新增的至少两组波长复用器/解复用器分别连接到所述多芯光纤传输链路中的扇入/扇出器件上，与多芯光纤中的非中心纤芯连接。
附图说明
下面对实施例或现有技术描述中所需使用的附图作简单地介绍。
图1为本申请实施例提供的一种多芯光纤的截面示意图；
图2为本申请实施例提供的多芯光纤中各个纤芯之间关系示意图；
图3为本申请实施例提供的多芯光纤中各个纤芯的折射率关系示意图；
图4为本申请实施例提供的多芯光纤的五种组内模式的示意图；
图5为本申请实施例提供的一种多芯光纤传输系统的结构示意图；
图6(a)为本申请实施例提供的现有单模光纤传输系统架构图；
图6(b)为本申请实施例提供的构建多芯光纤传输链路示意图；
图6(c)为本申请实施例提供的构建多芯光纤传输系统示意图；
图6(d)为本申请实施例提供的多芯光纤传输系统架构图；
图7(a)为本申请实施例提供的多芯光纤中的中心纤芯传输时示意图；
图7(b)为本申请实施例提供的多芯光纤中的扩容两组周围纤芯传输时示意图；
图7(c)为本申请实施例提供的多芯光纤中的扩容四组周围纤芯传输时示意图；
图8为本申请实施例提供的一种多芯光纤扩容的方法流程图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行描述。
本申请实施例提供了一种多芯光纤，该多芯光纤包括一个中心纤芯和至少两组非中心纤芯(后续将设置在非中心位置处的纤芯称为“周围纤芯”)，每组周围纤芯包括至少两个周围纤芯。其中，中心纤芯位于整个多芯光纤的正中心，至少两组周围纤芯分别按照一定规则，设置在中心纤芯的周围，且每组周围纤芯与中心纤芯之间的距离相等。
本申请中，中心纤芯与任意一组周围纤芯之间、以及每组周围纤芯之间，传输的能量无串扰或串扰很弱，使得本申请设计的多芯光纤可以支持从单模光纤平滑升级到多芯光纤，从而保护客户光纤和老网设备的投资；通过让每组周围纤芯包括至少两个纤芯，且组内每个纤芯之间，传输的能量串扰，从而提高多芯光纤的信道数量和带宽，并解决模式间色散大的问题。
下面通过几个实施例，具体讲述本申请实施例提供的多芯光纤的结构和性能。需要特别说明的是，本申请下面以9个纤芯的光纤(也即一个中心纤芯，8个周围纤芯)为例，来讲述本申请所要保护的多芯光纤，但本申请保护的多芯光纤不限于9个纤芯，可以为任意个纤芯，本申请在此不做限定。
实施例一
图1为本申请实施例提供的一种多芯光纤的截面示意图。如图1所示，本申请提供的多芯光纤包括9个纤芯(Core0-Core8)。其中，位于多芯光纤的中心位置的纤芯(Core 0)称为中心纤芯，位于纤芯(Core 0)周围的8个纤芯(Core1-Core8)称为周围纤芯。
对于中心纤芯(Core0)来说，为了与其它周围纤芯(Core0-Core8)之间无耦合，通过提供低折射率的沟道层来抑制与周围纤芯(Core0-Core8)之间产生串扰问题。另外，中心纤芯(Core0)通过纤芯掺锗的方式，让其光学性能兼容现有标准单模光纤(ITU-T G.652标准)光学参数，从而使得中心纤芯(Core0)可以与其它有中心纤芯的光纤对接，进行信号传输。
其中，这里提出的“耦合”是指两个或更多个纤芯在传输的光信号时，产生的电场之间相互串扰；“无耦合”是指两个或更多个纤芯在传输的光信号时，产生的电场之间相互无串扰，或串扰CT<-30dB/100km。
8个周围纤芯(Core1-Core8)根据耦合特性的需要，按照不同间距排列在中心纤芯(Core0)的周围。示例性地，如图2所示，8个周围纤芯(Core1-Core8)位于等间隔的4×4矩阵外框的中间节点上，周围纤芯(Core2，Core3)位于矩阵一个侧面的中间两个节点上，周围纤芯(Core4，Core5)位于矩阵一个侧面的中间两个节点上，周围纤芯(Core6，Core7) 位于矩阵一个侧面的中间两个节点上，周围纤芯(Core1，Core8)位于矩阵一个侧面的中间两个节点上。其中，4×4矩阵的间隔约为25μm，所以周围纤芯(Core1-Core8)与中心纤芯(Core0)之间的距离约为39.53μm，同一侧面上的两个周围纤芯之间的距离约为25μm，相邻侧面上的周围纤芯之间的距离约为35.36μm和55.9μm，相对侧面上的周围纤芯之间的距离约为75μm。
上述图2中4×4矩阵中的各个节点之间的间隔均是相等的，在实际应用中，间距可以不相同，如中间两个节点之间的距离可以小于中间节点与侧边节点之间的距离，使得组内两个纤芯之间更好的耦合。
另外，为了满足耦合特性的需要，再对8个周围纤芯(Core1-Core8)的折射率进行设定，可以通过微调折射率、或纤芯直径、或改变各纤芯区域结构等方式，让周围纤芯(Core2)与周围纤芯(Core3)之间、周围纤芯(Core4)与周围纤芯(Core5)之间、周围纤芯(Core6)与周围纤芯(Core7)之间和周围纤芯(Core1)与周围纤芯(Core8)之间的折射率相同，而中心纤芯(Core0)、周围纤芯(Core2，Core3)、周围纤芯(Core4，Core5)、周围纤芯(Core6，Core7)和周围纤芯(Core1，Core8)之间的折射率不同，通过产生差异性，形成中心纤芯(Core0)、周围纤芯(Core2，Core3)、周围纤芯(Core4，Core5)、周围纤芯(Core6，Core7)和周围纤芯(Core1，Core8)五组纤芯，且四组周围纤芯内纤芯，相互随机耦合，从而实现周围纤芯(Core2，Core3)、周围纤芯(Core4，Core5)、周围纤芯(Core6，Core7)和周围纤芯(Core1，Core8)分别构成4组有耦合的双芯通道。
其中，中心纤芯(Core0)的折射率高于任何一个周围纤芯的折射率，且周围纤芯(Core2，Core3)、周围纤芯(Core4，Core5)、周围纤芯(Core6，Core7)和周围纤芯(Core1，Core8)中任意两组周围纤芯之间的折射率之差必须满足不会出现显著的纤芯间因耦合产生串扰的问题。
可选地，由于周围纤芯(Core2，Core3)和周围纤芯(Core6，Core7)之间的距离比较远，相互之间产生串扰比较弱，所以可以让周围纤芯(Core2，Core3)和周围纤芯(Core6，Core7)选用相同折射率的纤芯。同理，周围纤芯(Core4，Core5)和周围纤芯(Core1，Core8)也选用相同折射率的纤芯，从而简化多芯光纤内部结构和降低多芯光纤的成本。
在一个例子中，构建出符合要求的多芯光纤的各个参数如图3所示，多芯光纤中的9个纤芯(Core0-Core8)的半径为4.8μm，每个纤芯外围的沟道层的外环半径为12μm，沟道宽度为7.2μm，每个纤芯外部的包层掺有氟，其折射率为1.439；每个纤芯的沟道层也掺有氟，其折射率为1.435。中心纤芯(Core0)材料为掺有少量的锗的SiO 2，其折射率1.446，周围纤芯(Core1-Core8)材料为纯SiO2，其折射率为1.444。由于本申请需要将8个周围纤芯(Core1-Core8)进行分组，所以四个分组的周围纤芯的沟道层的折射率之间约有0.2％的差异。
在本申请中，通过将周围纤芯(Core1-Core8)分成4组，得到4组周围纤芯，并加上中心纤芯(Core0)，使得本申请的多芯光纤有五种组间模式。在实际设计多芯光纤时，需要保证不同组间模式为无耦合或弱耦合的方式很多。示例性地，以两组周围纤芯之间串扰为例，假设第p组周围纤芯和第q组周围纤芯的组间模式的电场分别为Ep与Eq，则两组的组间模式的耦合系数k pq为:
Figure PCTCN2021117762-appb-000001
其中，ω表示角频率，ε0表示真空介电常数，n表示光纤截面折射率分布，nq表示第q组的组间模式中的纤芯截面折射率分布，Hp表示表示第q组的组间模式的磁场。
考虑实际应用场景中的微扰，两组的组间模式的功率耦合系数hpq为：
Figure PCTCN2021117762-appb-000002
其中，Kpq是kpq和kqp的平均值，d是相关长度，Δβ′ pq表示两组的组间模式的传输常数差。
此时，得到的两组的组间模式的串扰为：
Figure PCTCN2021117762-appb-000003
当两组的组间模式的串扰CT<-30dB/100km时，即认为第p组周围纤芯与第q组周围纤芯之间无耦合或弱耦合，而此时各组内模式主要分部于各自组的纤芯内，如图4所示。
另外，8个周围纤芯(Core1-Core8)按照两两分组构成的四组耦合芯，其各自组内模式在长距离传输时，相互之间会发生耦合，且各模式间具有空间模式色散(spatial mode dispersion，SMD)。当多芯光纤与接收机耦合进行传输时，为了降低接收机均衡复杂度，需要将多芯光纤各个组内的SMD控制在尽可能小的范围内。在随机耦合多芯光纤中，SMD是不同模式传输速度不同而造成的脉冲展宽，可通过包层折射率、纤芯之间的间距、纤芯半径、沟道半径、沟道折射率等参数研究组内SMD的变化。在不同结构参数下，计算得到各模式的有效折射率后，再利用公式(4)计算组内SMD，其中，公式(4)具体为：
Figure PCTCN2021117762-appb-000004
其中，L表示光纤长度，h表示模式耦合系数，c为真空中光速，δβ为模式传输常数差，k为波数。在本申请中，如果本申请多芯光纤的SMD不符合要求，优选的通过改变多芯光纤的长度L实现本申请多芯光纤的SMD在规定范围内。
本申请设计的多芯光纤，一个中心纤芯和8个周围纤芯，并将8个周围纤芯两两分组，生成四组纤芯，且组内纤芯之间随机耦合，使得本申请设计的多芯光纤可以支持从单模光纤平滑升级到多芯光纤，从而保护客户光纤和老网设备的投资。而且提高多芯光纤的信道数量和带宽，并解决模式间色散大的问题。
实施例二
图5为本申请实施例提供的一种多芯光纤传输系统的结构示意图。如图5所示，该系统包括N个光终端复用器(optical terminal multiplexer，OTM)501、M个光线路放大器(optical line amplifier，OLA)502和L个光纤503，且N和M为大于2的正整数，L为 大于3的正整数。其中，每个OTM 501通过光纤与OLA 502连接，每个OLA 502的一端与OTM 501连接，另一端与另一个OLA 502的一端连接。
OTM 501包括n光转发器单元(optical transponder unit，OTU)5011、波长复用器/解复用器(W Mux/W DMux)5012和扇入/扇出器件5013。
OTU 5011可分为现有单波长或频率超通道OTU和空间超通道OTU。其中，现有单波长或频率超通道OTU连接一个光纤信道，以支持两个偏振模式传输；空间超通道OTU连接一组光纤信道(信道数目不小于2)，且每组光纤信道包括两个偏振模式，然后通过2N×2N MIMO技术接收解调(N为每组内光纤信道数)。
波分复用器/解复用器，用于把多个端口不同波长信号的光复用到一个纤芯或从一个纤芯中接收到的多个波长信号解复用到多个端口输出。
扇入/扇出器件，用于把中间纤芯和包围在中间纤芯周围的多组周围纤芯复用到一根多芯光纤、或者把一根多芯光纤中多个纤芯的信号解复用为一个中间纤芯和多个分组的周围纤芯上输出。
OLA 502包括一对放大器5021，分别用于放大上下行两根光纤中的光信号。放大器5021可以是集中放大多个纤芯中的光信号，也可以通过扇入扇出器件把多芯光纤中的中间纤芯和周围纤芯组的纤芯中的信号分别放大。
另外，放大器5021可以分为单模光纤放大器和多芯光纤放大器。如果与单模光纤连接，则使用单模光纤放大器；如果与多芯光纤连接，则使用多芯光纤放大器。
光纤503可以为单模光纤，也可以为多芯光纤。其中，单模光纤为只能传一种模式的光纤，多芯光纤为包括多个纤芯的光纤，本申请在此采用的多芯光纤为上述图1-图4以及相应描述的多芯光纤。
实施例三
图6(a)-(d)为本申请实施例提供的从单模光纤平滑到多芯光纤的演进过程图。
如图6(a)所示，现有的一种单模光纤传输系统中，包括两个OTM、两个OLA(包括两个单模光纤放大器)和单模光纤。其中，一个OTM部署在近端(以左侧OTM为例，下同)，另一个OTM部署在远端(以右侧OTM为例，下同)，在两个OTM的波分复用器/解复用器上分别通过单模光纤连接一个OLA，用于补偿光纤衰减，然后再将两端的OLA分别与近端和远端之间的单模光纤连接，从而构建出单模光纤传输系统。
在信号传输过程，近端OTM发送光信号后，通过近端OLA、单模光纤和远端OLA后，传输至远端OTM；或远端OTM发送出光信号后，通过远端OLA、单模光纤和近端OLA后，传输至近端OTM。
需要特别说明的时，在单模光纤传输系统中，由于只传输一种模式的光纤，不需要将多个纤芯进行复用或解复用，所以近端OTM和远端OTM中可以没有扇入/扇出器件。
如图6(b)所示，在构建多芯光纤传输链路过程，在近端和远端之间的多芯光纤的两端分别连接多芯光纤放大器，然后在近端和远端的多芯光纤放大器上分别连接一个扇入/扇出器件，从而构成多芯光纤传输链路。如果近端扇入/扇出器件接收到多根光纤发送的光信号后，则将多跟光纤发送的光信号进行复用处理，使得多根光纤发送的 光信号可以传输至近端OLA、多芯光纤和远端OLA后，远端扇入/扇出器件将接收到的光信号进行解复用处理，然后发送出去。
上述多芯光纤包括五个分组，第一个分组位于光纤的中心，只有一个纤芯，与标准单模光纤性能兼容；在第一个分组的周围，有四个分组，其中每组至少包括2个同质纤芯。在构建完成多芯光纤传输链路后，需要通过必要的测试手段获得各个分组的链路性能，包括但不限于光信噪比、色散、偏振模色散/模式色散、非线性噪声等。
如图6(c)所示，在构建多芯光纤传输系统中，根据连接的多芯光纤的分组，如果近端和远端的扇入/扇出器件将多芯光纤中9个纤芯分成1个单模光纤和4个两芯光纤(图中以一个两芯光纤为例)时，则在近端和远端的扇入/扇出器件上连接1个单模光纤和4个两芯光纤，单模光纤与多芯光纤中的中心纤芯连接，两芯光纤与每组的周围纤芯连接；如果近端和远端的扇入/扇出器件将多芯光纤中9个纤芯分成9个单模光纤时，则在近端和远端的扇入/扇出器件上连接9个单模光纤。
然后将原单模光纤传输系统的波分复用器/解复用器的输入/输出端分别切换到新部署的多芯光纤传输链路上的近端的扇入/扇出器件上，实现与多芯光纤的中心纤芯连接；再在近端和远端新增空分复用特性的OTU、空分波分复用器/解复用器等器件(如果分成9个单模光纤，则在近端和远端新增OTU、波分复用器/解复用器等器件)，连接到近端和远端的扇入/扇出器件上，实现与其它组纤芯(非中心纤芯)连接，以扩大传输容量。
如图6(d)所示，通过如图6(c)所示的过程，构建出多芯光纤传输系统后，将原先单模传输链路移除(包括单模光纤和单模光纤放大器)。
构建出的多芯光纤传输系统在信号传输过程中，近端的波分复用器/解复用器和/或空分波分复用器/解复用器向近端的扇入/扇出器件发送光信号后，近端的扇入/扇出器件将多跟光纤发送的光信号进行复用处理，使得多根光纤发送的光信号可以通过多芯光纤传输，然后将复用后的光信号通过近端OLA、多芯光纤、远端OLA和远端的扇入/扇出器件；远端的扇入/扇出器件将接收到的光信号进行解复用处理，将得到的光信号分别传输至对应的远端的波分复用器/解复用器和/或空分波分复用器/解复用器上，从而实现信号的传输。
对于多芯光纤来说，如果只有波分复用器/解复用器发送光信号时，如图7(a)所示，此时中心纤芯(Core0)通过扇入/扇出器件与波分复用器/解复用器，进行光信号传输，而其它周围纤芯(Core1-Core8)处在暂时闲置状态；如果同时还有一组空分波分复用器/解复用器发送光信号时，如图7(b)所示，此时相比较单模光纤传输系统来说，扩容支持2芯空间超通道传输，此时周围纤芯(Core1，Core8)由近端向远端传输信号，周围纤芯(Core2，Core3)由远端向近端传输信号；如果同时还有两组空分波分复用器/解复用器发送光信号时，如图7(c)所示，此时相比较单模光纤传输系统来说，扩容支持4芯空间超通道传输，此时周围纤芯(Core1，Core8)和周围纤芯(Core4，Core5)由近端向远端传输信号，周围纤芯(Core2，Core3)和周围纤芯(Core6，Core7)由远端向近端传输信号；如果有两根多芯光纤，可以一根多芯光纤由近端向远端传输信号，另一根多芯光纤由远端向近端传输信号，从而实现扩容支持8芯空间超通道传输。
图8为本申请实施例提供的一种多芯光纤扩容的方法流程图。如图8所示，该多芯 光纤扩容的方法具体实现过程如下：
步骤S801，构建多芯光纤传输链路。
其中，构建的多芯光纤传输链路如图6(b)所示，在近端和远端之间的多芯光纤的两端分别连接多芯光纤放大器，然后在近端和远端的多芯光纤放大器上分别连接一个扇入/扇出器件，从而构成多芯光纤传输链路。
步骤S803，新增至少两组空分OTU和至少两组空分波长复用器/解复用器，或新增至少两组OTU和至少两组波长复用器/解复用器。
其中，如果近端和远端的扇入/扇出器件将多芯光纤中9个纤芯分成1个单模光纤和4个两芯光纤(图中以一个两芯光纤为例)时，则新增至少两组空分OTU和至少两组空分波长复用器/解复用器；如果近端和远端的扇入/扇出器件将多芯光纤中9个纤芯分成9个单模光纤时，则新增至少两组OTU和至少两组波长复用器/解复用器。
步骤S805，将所述单模光纤传输系统中至少两个波长复用器/解复用器分别切割到所述多芯光纤传输链路中的扇入/扇出器件上，与多芯光纤中的中心纤芯连接；和将新增的至少两组空分波长复用器/解复用器或新增的至少两组波长复用器/解复用器分别连接到所述多芯光纤传输链路中的扇入/扇出器件上，与多芯光纤中的周围纤芯连接。
其中，现有的单模光纤传输系统包括至少两个光终端复用器OTM、至少两个光线路放大器OLA和至少一个单模光纤，其中，每个OTM包括至少一个光转发器单元OTU和至少一个波长复用器/解复用器，每个OLA包括至少一个单模光纤放大器。在构建过程中，将原单模光纤传输系统的波分复用器/解复用器的输入/输出端分别切换到新部署的多芯光纤传输链路上的近端的扇入/扇出器件上，实现与多芯光纤的中心纤芯连接；再在近端和远端新增空分复用特性的OTU、空分波分复用器/解复用器等器件(如果分成9个单模光纤，则在近端和远端新增OTU、波分复用器/解复用器等器件)，连接到近端和远端的扇入/扇出器件上，实现与其它组纤芯(非中心纤芯)连接，以扩大传输容量。
在本说明书的描述中，具体特征、结构、材料或者特点可以在任何的一个或多个实施例或示例中以适合的方式结合。
最后说明的是：以上实施例仅用以说明本申请的技术方案，而对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (9)

  1. 一种多芯光纤，其特征在于，包括：
    中心纤芯，设置在所述多芯光纤的中心位置；
    至少两组非中心纤芯，分别设置在所述中心纤芯周围，且每组非中心纤芯中的各个非中心纤芯与所述中心纤芯之间的距离相等，所述中心纤芯与任意一组非中心纤芯之间、以及每组非中心纤芯之间，传输的能量无串扰或弱串扰；
    每组非中心纤芯包括至少两个非中心纤芯，每一组的所述至少两个非中心纤芯之间，传输的能量相互串扰。
  2. 根据权利要求1所述的多芯光纤，其特征在于，所述中心纤芯和所述每组非中心纤芯中的非中心纤芯之间的折射率不同。
  3. 根据权利要求1或2所述的多芯光纤，其特征在于，每一组非中心纤芯内各个非中心纤芯的折射率相同。
  4. 根据权利要求3所述的多芯光纤，其特征在于，每一组非中心纤芯之间的折射率的差值小于0.002。
  5. 根据权利要求3-4任意一项所述的多芯光纤，其特征在于，第一组非中心纤芯的折射率和第二组非中心纤芯的折射率相同，所述至少两组非中心纤芯包括所述第一组非中心纤芯和所述第二组非中心纤芯。
  6. 一种多芯光纤，其特征在于，包括：
    一个中心纤芯，设置在所述多芯光纤的中心位置；
    4组非中心纤芯，分别设置在所述中心纤芯周围，且每组非中心纤芯中的各个非中心纤芯与所述中心纤芯之间的距离相等，所述中心纤芯与任意一组非中心纤芯之间、以及每组非中心纤芯之间，传输的能量无串扰或弱串扰；
    每组非中心纤芯包括2个非中心纤芯，所述2个非中心纤芯之间，传输的能量相互串扰。
  7. 根据权利要求6所述的多芯光纤，其特征在于，所述4组非中心纤芯分别设置在4×4矩阵的四个侧面的外框上，且每组的所述2个非中心纤芯分别设置在中间两个节点上。
  8. 一种传输系统，其特征在于，包括：至少两个光终端复用器OTM、至少两个光线路放大器OLA和至少一个如权利要求1-5或权利要求6-7所述的多芯光纤。
  9. 一种多芯光纤扩容方法，应用在单模光纤传输系统上，所述单模光纤传输系统包括至少两个光终端复用器OTM、至少两个光线路放大器OLA和至少一个单模光纤，其中，每个OTM包括至少一个光转发器单元OTU和至少一个波长复用器/解复用器，每个OLA包括至少一个单模光纤放大器，其特征在于，包括：
    构建多芯光纤传输链路，所述多芯光纤传输链路通过在多芯光纤的两端分别设置一个多芯光纤放大器，然后分别在所述多芯光纤放大器上连接扇入/扇出器件得到的；
    新增至少两组空分OTU和至少两组空分波长复用器/解复用器，或新增至少两组OTU和至少两组波长复用器/解复用器；
    将所述单模光纤传输系统中至少两个波长复用器/解复用器分别切割到所述多芯光纤传输链路中的扇入/扇出器件上，与多芯光纤中的中心纤芯连接；和
    将新增的至少两组空分波长复用器/解复用器或新增的至少两组波长复用器/解复用器分别连接到所述多芯光纤传输链路中的扇入/扇出器件上，与多芯光纤中的非中心纤芯连接。
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