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WO2025046727A1 - Trajet de transmission optique et système de transmission optique - Google Patents

Trajet de transmission optique et système de transmission optique Download PDF

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Publication number
WO2025046727A1
WO2025046727A1 PCT/JP2023/031156 JP2023031156W WO2025046727A1 WO 2025046727 A1 WO2025046727 A1 WO 2025046727A1 JP 2023031156 W JP2023031156 W JP 2023031156W WO 2025046727 A1 WO2025046727 A1 WO 2025046727A1
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WO
WIPO (PCT)
Prior art keywords
optical transmission
crosstalk
mcf
low
signal light
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2023/031156
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English (en)
Japanese (ja)
Inventor
崇嘉 森
和秀 中島
隆 松井
裕介 山田
悠途 寒河江
雅 菊池
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NTT Inc
Original Assignee
Nippon Telegraph and Telephone Corp
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Filing date
Publication date
Application filed by Nippon Telegraph and Telephone Corp filed Critical Nippon Telegraph and Telephone Corp
Priority to PCT/JP2023/031156 priority Critical patent/WO2025046727A1/fr
Publication of WO2025046727A1 publication Critical patent/WO2025046727A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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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

Definitions

  • This disclosure relates to optical transmission paths and optical transmission systems.
  • Multicore fiber is known to increase the transmission capacity of optical fiber.
  • MCF Multicore fiber
  • XT crosstalk
  • Non-Patent Document 1 In order to suppress inter-core crosstalk, an MCF with appropriately designed core spacing has been proposed (Non-Patent Document 1).
  • Non-Patent Document 2 An optical transmission system has been proposed that reduces the effects of crosstalk by making the transmission directions of signal light to adjacent cores different from each other.
  • Non-Patent Document 3 A trench-type MCF has been proposed that reduces crosstalk between cores by making the core a trench structure.
  • This disclosure has been made in light of the above, and aims to provide an optical transmission path that combines quality and cost.
  • An optical transmission path includes a first multicore fiber and a second multicore fiber connected to both ends of the first multicore fiber, and the second multicore fiber has a characteristic of reducing crosstalk between cores more than the first multicore fiber.
  • An optical transmission system is an optical transmission system that transmits signal light in both directions, and includes the optical transmission path described above, a first transmitter that transmits a first signal light to a core of the optical transmission path, a first receiver that receives the first signal light via the optical transmission path, a second transmitter that transmits a second signal light to the core of the optical transmission path, and a second receiver that receives the second signal light via the optical transmission path, and the first signal light and the second signal light have different transmission directions.
  • This disclosure makes it possible to provide an optical transmission path that combines quality and cost.
  • FIG. 1 is a diagram illustrating an example of the configuration of an optical transmission line.
  • FIG. 2 is a diagram showing an example of a cross section of a multicore fiber.
  • FIG. 3 is a diagram illustrating an example of the relationship between the length ratio of a low-crosstalk multi-core fiber and crosstalk.
  • FIG. 4 is a diagram showing an example of the relationship between the length ratio of the low-crosstalk multi-core fiber and the crosstalk improvement amount when the crosstalk characteristic difference is 20 dB.
  • FIG. 5 is a diagram showing an example of the relationship between the length ratio of the low-crosstalk multi-core fiber and the crosstalk improvement amount when the crosstalk characteristic difference is 10 dB.
  • FIG. 1 is a diagram illustrating an example of the configuration of an optical transmission line.
  • FIG. 2 is a diagram showing an example of a cross section of a multicore fiber.
  • FIG. 3 is a diagram illustrating an example of the relationship between the length ratio of a low-crosstalk multi-core fiber and crosstalk.
  • FIG. 6 is a diagram showing an example of the relationship between the length ratio of the low-crosstalk multi-core fiber and the crosstalk improvement amount when the crosstalk characteristic difference is 30 dB.
  • FIG. 7 is a diagram showing an example of the relationship between the length ratio of the low-crosstalk multi-core fiber and the crosstalk improvement amount when the crosstalk characteristic difference is 40 dB.
  • FIG. 8 is a diagram showing the relationship between the total transmission distance and the length ratio of the low-crosstalk multi-core fiber when the crosstalk improvement amount is set to 5 dB.
  • FIG. 9 is a diagram showing the relationship between the total transmission distance and the length ratio of the low-crosstalk multi-core fiber when the crosstalk improvement amount is set to 10 dB.
  • FIG. 10 is a diagram showing the relationship between the total transmission distance and the length ratio of the low-crosstalk multi-core fiber when the crosstalk improvement amount is set to 15 dB.
  • FIG. 11 is a diagram illustrating an example of the configuration of an optical transmission line.
  • FIG. 12 is a diagram illustrating an example of a configuration of an optical transmission system.
  • FIG. 13 is a diagram illustrating an example of a configuration of an optical transmission system.
  • FIG. 1 is a diagram showing an example of the configuration of an optical transmission line 10 of this embodiment.
  • the optical transmission line 10 in FIG. 1 is an optical transmission line configured with multicore fibers 11 and 12 having multiple cores.
  • Multicore fibers 12 are connected to both ends of the multicore fiber 11.
  • the multicore fiber 12 has lower crosstalk characteristics between adjacent cores than the multicore fiber 11.
  • the crosstalk characteristics are an index for evaluating the interference and influence of signal light between adjacent cores. If the crosstalk characteristics are low, the deterioration of signal quality caused by crosstalk can be suppressed.
  • the multicore fibers 11 and 12 are connected by fusion splicing or optical connectors with their core axes aligned and their cores aligned.
  • the multicore fiber 11 may be referred to as a high XT-MCF
  • the multicore fiber 12 as a low XT-MCF.
  • the following table shows an example of the characteristics of high XT-MCF and low XT-MCF.
  • the difference in crosstalk characteristics between high XT-MCF and low XT-MCF is 10 -2 km -1 (-20 dB/km).
  • the difference in co-directional XT and return XT characteristics between high XT-MCF and low XT-MCF is 10 -2 km -1 (-20 dB/km).
  • the propagation loss between high XT-MCF and low XT-MCF is 0.2 dB/km.
  • high XT-MCF is a step-index MCF
  • low XT-MCF is a trench-assisted MCF.
  • Step-index MCF is easier to fabricate than trench-assisted MCF, and costs can be reduced.
  • High XT-MCF and low XT-MCF are uncoupled MCFs, and it is desirable for the core spacing to be around 40 ⁇ m.
  • the optical transmission path 10 is a transmission path that assumes bidirectional transmission. Opposing signal light is input to each adjacent core.
  • a low XT-MCF is connected to one end of a high XT-MCF, the order in which the signal light passes through multicore fibers with different crosstalk characteristics differs depending on the direction in which the signal light is input, resulting in differences in signal quality.
  • by connecting low XT-MCFs to both ends of a high XT-MCF it is possible to obtain a crosstalk reduction effect during bidirectional transmission, regardless of the input direction of the signal light.
  • Figure 2 shows an example of a cross-sectional view of the multicore fibers 11 and 12.
  • the multicore fibers 11 and 12 have multiple cores 102 in the cladding 101.
  • Figure 2 shows examples of multicore fibers with an even number of cores, such as 2 cores, 4 cores, 6 cores, and 8 cores. Each core may have a different refractive index difference or core radius.
  • the cores 102 are arranged in a circular ring.
  • the cores 102 may be arranged in a straight line, as in the 2-core MCF.
  • the cores 102 are arranged in a double circular ring.
  • the crosstalk between adjacent cores is the crosstalk between the nearest cores.
  • Figure 3 shows the crosstalk value versus the length ratio r of low XT-MCF for optical transmission lines with total transmission distances L of 20, 40, 80, and 100 km.
  • the horizontal axis shows the length ratio r of low XT-MCF
  • the vertical axis shows the crosstalk value.
  • the ratio of low XT-MCF increases toward the right of the figure, which means higher costs.
  • the effect of crosstalk increases toward the top of the figure.
  • the difference in crosstalk characteristics between high XT-MCF and low XT-MCF is set to 10 -2 km -1 (-20 dB/km).
  • the horizontal axis shows the length ratio r of low XT-MCF
  • the vertical axis shows the crosstalk improvement. Note that Figures 4 to 7 show different differences in crosstalk characteristics between high XT-MCF and low XT-MCF. Each figure will be explained below.
  • FIG. 4 shows the crosstalk improvement XTR when the crosstalk characteristic difference ⁇ XT between high XT-MCF and low XT-MCF is 20 dB/km.
  • the crosstalk characteristic of the high XT-MCF is 10 -2 km -1
  • that of the low XT-MCF is 10 -4 km -1 .
  • FIG. 5 shows the crosstalk improvement XTR when the crosstalk characteristic difference ⁇ XT between high XT-MCF and low XT-MCF is 10 dB/km.
  • the crosstalk characteristic of the high XT-MCF is 10 -2 km -1
  • the crosstalk characteristic of the low XT-MCF is 10 -3 km -1 .
  • FIG. 6 shows the crosstalk improvement XTR when the crosstalk characteristic difference ⁇ XT between high XT-MCF and low XT-MCF is 30 dB/km.
  • the crosstalk characteristic of the high XT-MCF is 10 -2 km -1
  • the crosstalk characteristic of the low XT-MCF is 10 -5 km -1 .
  • FIG. 7 shows the crosstalk improvement XTR when the crosstalk characteristic difference ⁇ XT between high XT-MCF and low XT-MCF is 40 dB/km.
  • the crosstalk characteristic of the high XT-MCF is 10 -2 km -1
  • the crosstalk characteristic of the low XT-MCF is 10 -6 km -1 .
  • the length ratio r of the low XT-MCF can be determined based on the crosstalk improvement amount XT R , the total transmission distance L, and the crosstalk characteristic difference ⁇ XT between the high XT-MCF and the low XT-MCF.
  • Figures 8 to 10 show the relationship between the total transmission distance L and the length ratio r of low XT-MCF for each amount of crosstalk improvement that can be achieved.
  • the horizontal axis is the total transmission distance L
  • the vertical axis is the length ratio r of low XT-MCF.
  • FIG. 8 is a diagram showing the relationship between the total transmission distance L and the length ratio r of the low XT-MCF when the crosstalk improvement amount XTR is 5 dB.
  • FIG. 9 is a diagram showing the relationship between the total transmission distance L and the length ratio r of the low XT-MCF when the crosstalk improvement amount XTR is 10 dB.
  • FIG. 10 is a diagram showing the relationship between the total transmission distance L and the length ratio r of the low XT-MCF when the crosstalk improvement amount XT R is 15 dB.
  • the desired crosstalk improvement amount ⁇ XT R can be achieved by setting r so that the relationship between r and L satisfies the following equation.
  • the approximation line expressed by the above formula is shown by a solid line.
  • the desired crosstalk improvement amount XTR 5, 10, 15 dB can be realized. Note that it is desirable that the crosstalk characteristic difference ⁇ XT between the high XT-MCF and the low XT-MCF is equal to or greater than the crosstalk improvement amount XTR .
  • FIG. 11 is a diagram showing the configuration of an optical transmission line 10 of a modified example.
  • a multi-core fiber 13 (medium XT-MCF) having crosstalk characteristics between the crosstalk characteristics of the multi-core fibers 11 and 12 is disposed between the multi-core fibers 11 and 12.
  • a plurality of multi-core fibers 12 and 13 having different crosstalk characteristics may be provided on both ends of the multi-core fiber 11.
  • optical transmission system An optical transmission system that uses the optical transmission line 10 of this embodiment will be described with reference to FIG.
  • the optical transmission system shown in FIG. 12 includes an optical transmission path 10 in which multicore fibers 11, 12 having M+N cores are connected.
  • the optical transmission path 10 is configured such that multicore fibers (low XT-MCF) 12 are connected to both ends of a multicore fiber (high XT-MCF) 11.
  • the lengths of the multicore fibers 12 at both ends of the optical transmission path 10 do not necessarily have to be the same.
  • the signal light propagates in different directions between the M cores u1 to uM and the N cores d1 to dN.
  • the M cores u1 to uM are not adjacent to one another, and the N cores d1 to dN are not adjacent to one another. In other words, the signal light propagating through adjacent cores propagates in opposite directions.
  • the signal light output by the left transmitters 30-u1 to 30-uM is sent to each of the cores u1 to uM of the left multicore fiber 12 via the optical coupling unit 50-1, and is received by the right receivers 40-u1 to 40-uM via the multicore fiber 11, the right multicore fiber 12, and the optical coupling unit 50-2.
  • the signal light output by the right-side transmitters 30-d1 to 30-dN is sent to each of the cores d1 to dN of the right-side multicore fiber 12 via the optical coupling unit 50-2, and is received by the left-side receivers 40-d1 to 40-dN via the multicore fiber 11, the left-side multicore fiber 12, and the optical coupling unit 50-1.
  • the receiver 40 processes the received signal with a Digital Signal Processor (DSP). If the receiver 40 is equipped with a Multiple-Input Multiple-Output Digital Signal Processor (MIMO-DSP), the MIMO-DSP can eliminate noise caused by crosstalk, allowing the wiring distance of the optical transmission path 10 to be extended.
  • DSP Digital Signal Processor
  • MIMO-DSP Multiple-Input Multiple-Output Digital Signal Processor
  • the optical coupling unit 50 can use a fan-in/fan-out device for multicore fiber.
  • the communication wavelength band of the signal light is approximately 1.3 to 1.7 ⁇ m.
  • the signal light may also be in the mid-infrared range (2 ⁇ m or more) with a longer wavelength, or in the visible light range.
  • the optical transmission system shown in FIG. 13 includes an optical transmission line that connects K optical transmission lines 10-1 to 10-K.
  • Each of the K optical transmission lines 10-1 to 10-K is an MCF in which a low XT-MCF is connected to both ends of a high XT-MCF.
  • K-1 amplifier units 60-1 to 60-K-1 are disposed at the connection points of the K optical transmission lines 10-1 to 10-K.
  • amplifier units 60-1 to 60-K-1 are connected via optical coupling units 50-1 to 50-2K.
  • the amplifier units 60 amplify the signal light propagating through each core of the optical transmission line 10.
  • the optical transmission lines 10-1 to 10-K have M+N cores.
  • the signal light propagates in a different direction between the M cores u1 to uM and the N cores d1 to dN.
  • the M cores u1 to uM are not adjacent to one another, and the N cores d1 to dN are not adjacent to one another.
  • the signal light output by the transmitters 30-u1 to 30-uM on the left side is sent to each core u1 to uM of the optical transmission line 10-1 via the optical coupling unit 50-1, propagates through the K optical transmission lines 10-1 to 10-K while being amplified by the amplifiers 60-1 to 60-K-1, and is received by the receivers 40-u1 to 40-uM on the right side.
  • the signal light output by the transmitters 30-d1 to 30-dN on the right side is sent to each core d1 to dN of the optical transmission line 10-K via the optical coupling unit 50-2K, propagates through the K optical transmission lines 10-1 to 10-K while being amplified by the amplifiers 60-1 to 60-K-1, and is received by the receivers 40-d1 to 40-dN on the left side.
  • the loss caused by the signal light propagating through the MCF is compensated for by the amplifier section 60, making it possible to support long-distance transmission paths.
  • the optical transmission path 10 of this embodiment includes a multicore fiber 11 and multicore fibers 12 connected to both ends of the multicore fiber 11.
  • the multicore fiber 12 has a characteristic of reducing crosstalk between cores more than the multicore fiber 11.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne un trajet de transmission optique 10 comprenant une fibre à âmes multiples 11 et des fibres à âmes multiples 12 connectées aux deux extrémités de la fibre à âmes multiples 11. Les fibres à âmes multiples 12 ont des caractéristiques telles que la diaphonie entre les âmes est réduite par rapport à la fibre à âmes multiples 11.
PCT/JP2023/031156 2023-08-29 2023-08-29 Trajet de transmission optique et système de transmission optique Pending WO2025046727A1 (fr)

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Application Number Priority Date Filing Date Title
PCT/JP2023/031156 WO2025046727A1 (fr) 2023-08-29 2023-08-29 Trajet de transmission optique et système de transmission optique

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PCT/JP2023/031156 WO2025046727A1 (fr) 2023-08-29 2023-08-29 Trajet de transmission optique et système de transmission optique

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130136404A1 (en) * 2011-11-30 2013-05-30 At&T Intellectual Property I, L.P. Multicore Optical Fiber with Reduced Inter-Core Crosstalk
JP2014126575A (ja) * 2012-12-25 2014-07-07 Fujikura Ltd マルチコアファイバ
WO2020080254A1 (fr) * 2018-10-15 2020-04-23 住友電気工業株式会社 Module optique et procédé de fabrication d'un module optique
WO2020209170A1 (fr) * 2019-04-08 2020-10-15 日本電気株式会社 Dispositif d'amplification optique, système de transmission optique et procédé d'amplification optique
WO2021177367A1 (fr) * 2020-03-06 2021-09-10 住友電気工業株式会社 Dispositif de guide d'ondes optique et système de communication optique comprenant ce dernier
WO2023008341A1 (fr) * 2021-07-28 2023-02-02 古河電気工業株式会社 Fibre à âmes multiples, dispositif de conversion de pas, corps de connexion de fibre optique et procédé de production de corps de connexion de fibre optique

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130136404A1 (en) * 2011-11-30 2013-05-30 At&T Intellectual Property I, L.P. Multicore Optical Fiber with Reduced Inter-Core Crosstalk
JP2014126575A (ja) * 2012-12-25 2014-07-07 Fujikura Ltd マルチコアファイバ
WO2020080254A1 (fr) * 2018-10-15 2020-04-23 住友電気工業株式会社 Module optique et procédé de fabrication d'un module optique
WO2020209170A1 (fr) * 2019-04-08 2020-10-15 日本電気株式会社 Dispositif d'amplification optique, système de transmission optique et procédé d'amplification optique
WO2021177367A1 (fr) * 2020-03-06 2021-09-10 住友電気工業株式会社 Dispositif de guide d'ondes optique et système de communication optique comprenant ce dernier
WO2023008341A1 (fr) * 2021-07-28 2023-02-02 古河電気工業株式会社 Fibre à âmes multiples, dispositif de conversion de pas, corps de connexion de fibre optique et procédé de production de corps de connexion de fibre optique

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