CN102461021B - Receiver for optical transverse-mode-multiplexed signals - Google Patents

Receiver for optical transverse-mode-multiplexed signals Download PDF

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Publication number
CN102461021B
CN102461021B CN201080028849.XA CN201080028849A CN102461021B CN 102461021 B CN102461021 B CN 102461021B CN 201080028849 A CN201080028849 A CN 201080028849A CN 102461021 B CN102461021 B CN 102461021B
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China
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signal
optical
optical fiber
tmm
phase
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CN201080028849.XA
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CN102461021A (en
Inventor
R-j·埃西安布尔
R·赖夫
P·J·温泽尔
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Alcatel Optical Networks Israel Ltd
Nokia of America Corp
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Alcatel Optical Networks Israel Ltd
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Priority claimed from US12/492,399 external-priority patent/US8320769B2/en
Priority claimed from US12/492,391 external-priority patent/US8355638B2/en
Application filed by Alcatel Optical Networks Israel Ltd filed Critical Alcatel Optical Networks Israel Ltd
Publication of CN102461021A publication Critical patent/CN102461021A/en
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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
    • H04B10/60—Receivers
    • 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
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/14—Mode converters
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2848—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers having refractive means, e.g. imaging elements between light guides as splitting, branching and/or combining devices, e.g. lenses, holograms
    • 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
    • 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
    • H04B10/40—Transceivers
    • 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
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/614—Coherent receivers comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers
    • 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
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/65—Intradyne, i.e. coherent receivers with a free running local oscillator having a frequency close but not phase-locked to the carrier signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/04—Mode multiplex systems

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

A representative optical receiver of the invention receives an optical transverse-mode-multiplexed (TMM) signal through a multimode fiber that supports a plurality of transverse modes. The optical receiver has a plurality of optical detectors operatively coupled to a digital signal processor configured to process the TMM signal to determine its modal composition. Based on the determined modal composition, the optical receiver demodulates each of the independently modulated components of the TMM signal to recover the data encoded onto the TMM signal at the remote transmitter.

Description

For the receiver of light transverse-mode-multiplexed signals
the cross reference of related application
The theme of the application relates to R.-J.Essiambre, R.Ryf and P.Winzer's, attorney docket is Essiambre 22-36, to submit on the same day with the present invention, title is the U.S. Patent application No.12/492 of " Transverse-Mode Multiplexing for Optical Communication Systems (transverse mode for optical communication system is multiplexing) ", 399, it is all herein incorporated this application by reference.
Technical field
The present invention relates to optical communication equipment, the present invention especially but and not exclusively relate to the equipment of the transverse mode multiplexing (TMM) supported in optical communication system.
Background technology
This part is introduced and can be helped to be convenient to understand aspects of the present invention better.Correspondingly, the description of this part should from reading in this respect, and should not be understood to admit which be prior art or which be not prior art.
The wireless communication system with multiple-input and multiple-output (MIMO) function improves total transmission capacity by developing (instead of attempting to alleviate) multidiameter broadening in wireless channel.More specifically, radio MIMO is by using multiple antennas to improve efficiency and reliability at transmitter and receiver place.The raising of average throughput caused thus with signal transacting and hard-wired larger complexity for cost and realizing, and not with the spectral bandwidth increased or higher signal power for cost.
In optical communication system, such as, due to the modal dispersion of multimode optical fiber and the multidiameter of wireless transmission medium similar, be feasible for improving the MIMO method of transmission capacity.Therefore, light MIMO can be used for developing the intrinsic high-transmission capacity of multimode optical fiber.But, also fully do not develop for the hardware implementing light MIMO.
Summary of the invention
The various embodiments of the optical receiver for light transverse mode multiplexing (TMM) signal are disclosed at this.A kind of representative optical receiver of the present invention is by supporting that the multimode optical fiber of multiple transverse mode receives TMM signal.This optical receiver comprises the photodetector that multiple operability is coupled to digital signal processor, and this digital signal processor is configured for this TMM signal of process, to determine that its pattern forms.Form based on determined pattern, each separate modulation component of this optical receiver to TMM signal carries out demodulation, to recover the data be encoding at remote transmitters place on this TMM signal.
According to an embodiment, provide a kind of optical receiver, it comprises: (A) tap module, its light TMM signal be configured for having N number of separate modulation component is sampled, to produce K light sample at each Signal transmissions interval, N and K be greater than one positive integer, wherein K >=N; (B) local oscillator (LO) source, it is configured for and generates light LO signal; And (C) K coherent detector, each coherent detector is optically coupled to this tap module and LO source.Each in this K coherent detector is all configured for (i) by corresponding light sample and the mixing of this LO signal, to generate one or more optical interference signals; And described one or more optical interference signals is converted to the instruction in-phase component of this light sample and one or more electric signal of quadrature component by (ii).This optical receiver comprises digital signal processor (DSP) further, its operability is coupled to this K coherent detector, and be configured for and process the electric signal that produced by coherent detector, with recover by N number of separate modulation component of TMM signal each entrained by data.This optical receiver is by supporting that the multimode optical fiber of multiple transverse mode receives this TMM signal.At the remote terminal of this multimode optical fiber, each separate modulation component of this TMM signal corresponds to the corresponding single transverse mode of multimode optical fiber.
According to another embodiment, provide a kind of optical receiver, it comprises tap module, the light TMM signal be configured for having N number of separate modulation component is sampled, to produce K light sample at each Signal transmissions interval, N and K be greater than one positive integer, wherein K >=N.This tap module is by supporting that the multimode optical fiber of multiple transverse mode receives this TMM signal.This optical receiver comprises (i) local oscillator (LO) source further, and it is configured for and generates light LO signal; And (ii) K coherent detector, each coherent detector is optically coupled to this tap module and LO source.Each in this K coherent detector is all configured for: (a) carries out phase filtering to this LO signal, corresponding through phase filtering light beam to produce, it has the PFS pattern of phase place/field strength (PFS) pattern corresponding to the corresponding selected transverse mode of this multimode optical fiber; B () is by corresponding light sample and this is through the mixing of phase filtering light beam, to generate one or more optical interference signals; And described one or more optical interference signals is converted to the instruction in-phase component of this light sample and one or more electric signal of quadrature component by (iii).This optical receiver comprises digital signal processor (DSP) further, its operability is coupled to this K coherent detector, and be configured for the electric signal processing and produced by this coherent detector, to recover the data of being carried by each separate modulation component of N number of separate modulation component of this TMM signal.
According to another embodiment, provide a kind of optical receiver, it comprises multiple beam splitter, it is configured for: the beam separation corresponding to light TMM signal is multiple beamlets of the first quantity by (i), wherein this TMM signal has multiple separate modulation component, and via supporting that the multimode optical fiber of multiple transverse mode receives; (ii) by the beam separation corresponding to local oscillator (LO) signal be multiple beamlets of the second quantity; And the beamlet from this first quantity and the second quantity mixes to generate two or more mixed light beams by (iii).This optical receiver comprises further: (a) first array detector, and it is configured for the first interference figure detecting the first mixed light beam corresponding to these two or more mixed light beams; (b) second array detector, it is configured for the second interference figure detecting the second mixed light beam corresponding to these two or more mixed light beams; And (c) digital signal processor (DSP), its operability is coupled to this first and second array detector, and be configured for this first and second interference figure of process, to determine the pattern composition of this TMM signal, and form based on described pattern, recover the data entrained by the separate modulation component of this TMM signal.
According to another embodiment, provide a kind of optical receiver, it comprises tap module, it is configured for samples to the light transverse mode with N number of separate modulation component multiplexing (TMM) signal, to produce K light sample at each Signal transmissions interval, N and K be greater than one positive integer, wherein K >=N.This optical receiver comprises (i) local oscillator (LO) source further, and it is configured for and generates light LO signal; And (ii) K coherent detector, each coherent detector is optically coupled to this tap module and LO source.Each in this K coherent detector is all configured for (a) by corresponding light sample and the mixing of LO signal, to generate one or more optical interference signals; And described one or more optical interference signals is converted to the instruction in-phase component of this light sample and one or more electric signal of quadrature component by (b).This optical receiver comprises digital signal processor (DSP) further, its operability is coupled to this K coherent detector, and be configured for the electric signal processing and produced by this coherent detector, to recover the data entrained by each separate modulation component of N number of separate modulation component of this TMM signal.This optical receiver is by supporting that the multimode optical fiber of multiple transverse mode receives this TMM signal.This tap module comprises: (A) K multimode optical fiber (MMF) coupling mechanism, and luminous power is tapped into single-mode fiber from this multimode optical fiber by each coupling mechanism, to produce the corresponding light sample of this TMM signal; And (B) K-1 pattern scrambler, its each be arranged between the MMF coupling mechanism of two vicinities.
Accompanying drawing explanation
At least one secondary coloured picture is comprised in this patent or application documents.Should to ask and after paying necessary expense, will be provided by official with copy disclosed in this patent of coloured picture or patented claim.
By way of example, from the following detailed description and accompanying drawing, other aspects of various embodiments of the invention, Characteristics and advantages will become more fully obviously, wherein:
Fig. 1 shows the block diagram of the optical communication system can putting into practice various embodiments of the invention;
Fig. 2 A-Fig. 2 H shows the sectional view of the optical fiber that can use in the system of fig. 1 according to various embodiments of the invention;
Fig. 3 A-Fig. 3 B illustrates the optical transmitting set that can use in the node of system shown in Figure 1 according to an embodiment of the invention;
Fig. 4 A-Fig. 4 B illustrates optical mode coupling (OMC) module that can use in the transmitter of Fig. 3 according to an embodiment of the invention;
Fig. 5 shows the block diagram of the OMC module that can use in the transmitter of Fig. 3 according to another embodiment of the present invention;
Fig. 6 shows the block diagram of the OMC module that can use in the transmitter of Fig. 3 according to further embodiment of this invention;
Fig. 7 shows the block diagram of the optical transmitting set that can use in the node of system shown in Figure 1 according to another embodiment of the present invention;
Fig. 8 shows the block diagram of the optical transmitting set that can use in the node of system shown in Figure 1 according to further embodiment of this invention;
Fig. 9 shows the block diagram of the optical receiver that can use in the node of system shown in Figure 1 according to an embodiment of the invention;
Figure 10 A-Figure 10 B shows the tap module and coherent detector that can use in the optical receiver shown in Fig. 9 according to an embodiment of the invention;
Figure 11 shows the tap module that can use in the optical receiver shown in Fig. 9 according to another embodiment of the present invention; And
Figure 12 shows the block diagram of the optical receiver that can use in the node of system shown in Figure 1 according to another embodiment of the present invention.
Embodiment
optical communication system
Fig. 1 shows the block diagram of the optical communication system 100 can putting into practice various embodiments of the invention.System 100 comprises multiple communication nodes 110 of the network interconnection by optical communication link 120.System 100 comprises optical add/drop multiplexer (ADM) 130, image intensifer 140 and optical cross-connect 150 further, and it is all inserted between node 110 in a variety of manners.
Each node 110 has light multiple-input and multiple-output (MIMO) function realized by using transverse mode multiplexing (TMM).Node 110 generally comprises optical transmitting set and optical receiver (all clearly not illustrating in Fig. 1), with the two-way communication between the various nodes of back-up system 100.Except TMM is multiplexing, each node 110 also can use wavelength-division multiplex (WDM) and/or palarization multiplexing (PM), or both uses.The representative embodiment of optical transmitting set and the receiver that can use in individual nodes 110 will be described in further detail at the corresponding paragraph of this instructions below.
Each optical communication link 120 by use following in one or morely to realize: (i) single-mode fiber; (ii) multimode optical fiber; (iii) multi-core fiber; (iv) single-mode fiber bundle.In one embodiment, the multimode optical fiber used in link 120 supports the transverse mode between two kinds to about 100 kinds.In an alternative embodiment, multimode optical fiber support is more than 100 kinds of transverse modes.In one embodiment, each fibre core of the multi-core fiber used in link 120 supports single transverse mode.In an alternative embodiment, the some or all of fibre cores of multi-core fiber support multiple transverse mode, and this multi-core fiber super model as a whole.
As used herein, term " transverse mode " refers to that it has nothing to do with propagation distance substantially at the guided electromagnetic wave perpendicular to (namely laterally) in the plane of the direction of propagation with electric field or Distribution of Magnetic Field (hereinafter referred to as optical field distribution).More specifically, if the loss of the luminous power in optical fiber or the factor of gain are excluded, the optical field distribution of this pattern then measured along two diverse location places of optical fiber is by only owing to reflecting the factor of overall phase transformation and different, and this phase transformation is formed by the pattern between these two positions.Often kind of transverse mode is an eigenmode of optical fiber, and different transverse modes is mutually orthogonal.Usually, optical fiber can support the transverse mode of fixed qty, and its optical field distribution and propagation constant are determined clearly by waveguiding structure, material behavior and optical frequency (wavelength).It should be noted, the concept of transverse mode is applicable to the polytype optical fiber comprising multi-core fiber.Such as, the transverse mode of the individual fibre core of multi-core fiber is also the transverse mode of this multi-core fiber as a whole.
In one embodiment, optical add/drop multiplexer 130 is reconfigurable add-drop multiplexer.Typically have the feature of the intermode mixing of relative height due to link 120, node 110 generally needs reception to have all transverse modes of identical optical frequency (wavelength), correctly to process the data that TMM signal also recovers to be carried by this signal.Therefore, multiplexer 130 is designed to (i) and separates all transverse modes with identical optical frequency from input link 120, and/or (ii) inserts to output link 120 and have all of identical optical frequency and insert transverse mode.In other words, multiplexer 130 realizes conventional WDM drop and insert feature, but works to the multiplexing entirety of the TMM of each specific wavelength.
In order to support the function of expecting, multiplexer 130 uses arrowband, intertexture type optical filter, and it has transmission feature identical substantially for all transverse modes.In addition, multiplexer 130 has the WDM crosstalk (that is, the crosstalks between the different optical frequencies that WDM is multiplexing) of low relative levels.A rear feature performed necessary light filtering (for example, see Fig. 8) by such as (i) before Mode Coupling module in single mode territory; (ii) Singh's type (sinc) wave shaping is used; And/or (iii) uses OFDM (OFDM) to realize.
If system 100 uses multi-core fiber in link 120, then multiplexer 130 can be designed as using one group of selected fibre core (can be all fibre cores of this multi-core fiber or its random subset) as single entity, thus inserts wavelength channel to this whole group of fibre core and/or separate this wavelength channel from this whole group of fibre core simultaneously.If link 120 has the crosstalk of low relative levels between different fibre core, then multiplexer 130 can be designed as and in each individual fibre core, to insert signal of communication and/or separate signal of communication in each individual fibre core, crosstalk between core is considered as noise/loss simultaneously.
In various embodiments, image intensifer 140 can for concentrating amplifier or distributed amplifier.Usually, system 100 can be designed as the whole link that runs through between two communication nodes 110 and maintains unitary (unitary) property of mode mixture matrix.Therefore, image intensifer 140 is designed to present gain identical substantially for all transverse modes of link 120.
In one embodiment, image intensifer 140 is relatively long fiber amplifier (being such as longer than about 100m), and it comprises (i) multiple active section, and (ii) is inserted in the multiple pattern scramblers between active section.Each active section provides a medium gain (such as, between about 1dB to 5dB).Pattern scrambler (having another name called for mode mixer) is the optical device introducing relatively large Mode Coupling between different transverse modes.Ideally, pattern scrambler generates statistically uniform mode mixture at output terminal, and the mode profile that this mode mixture receives at input end with pattern scrambler substantially has nothing to do.Those skilled in the art will recognize, the combination of the medium gain of each active section and the pattern scrambling of related frequency ensure that all transverse modes being applied to amplifier 140 experience amplification quantity identical substantially.
In one embodiment, optical cross-connect 150 is reconfigurable, to support the expectation route of the light signal between different node 110.As mentioned above, in order to each separate modulation component that the TMM that correctly decodes is multiplexing, it is multiplexing that node 110 generally needs to receive whole TMM.Correspondingly, cross-connect 150 is designed to, when performing its WDM routing function, integrally work multiplexing for the TMM corresponding with each wavelength.One of skill in the art will appreciate that usually, cross-connect 150 can be realized by multiple assembly identical with multiplexer 130.
Exemplarily, the system 100 shown in Fig. 1 comprises four nodes, 110, optical add/drop multiplexer, 130, image intensifer 140 and an optical cross-connect 150.It will be appreciated by one of skill in the art that, in other embodiments, system 100 can comprise the node 110 of varying number, optical add/drop multiplexer 130, image intensifer 140 and/or optical cross-connect 150.Those skilled in the art will understand further, and usually, these elements can arrange in the mode different from shown in Fig. 1 or interconnect.
optical fiber
Fig. 2 A-Fig. 2 H shows (not in scale) sectional view according to the optical fiber that can use within system 100 of various embodiments of the invention.More specifically, the various optical fiber shown in Fig. 2 A-Fig. 2 H may be used for node 110, optical communication link 120, optical add/drop multiplexer 130, image intensifer 140 and/or optical cross-connect 150.
Fig. 2 A shows the sectional view of single-mode fiber 210.Optical fiber 210 comprises covering 212 and fibre core 216.The diameter of fibre core 216 is relatively little, and it makes the single transverse mode of each wavelength in the wavelength coverage of use in optical fiber 210 back-up system 100.
Fig. 2 B shows the sectional view of multimode optical fiber 220.Optical fiber 220 comprises covering 222 and fibre core 226.With the difference of optical fiber 210, optical fiber 220 is that the diameter of fibre core 226 is greater than fibre core 216.In various embodiments, the diameter of fibre core 226 is chosen as the transverse mode making optical fiber 220 can support the desired amt selected in the scope of 2 to about 100.
Fig. 2 C shows the sectional view of multimode optical fiber 230.Optical fiber 230 comprises covering 232 and fibre core 236.The diameter of fibre core 236 is also larger than fibre core 226, and it makes optical fiber 230 can support about 100 kinds of transverse modes incessantly.
Fig. 2 D shows the sectional view of multi-core fiber 240.Optical fiber 240 has first (outward) covering 242 and second (interior) covering 244.Optical fiber 240 has the multiple fibre cores 246 being enclosed in inner cladding 244 li further.The diameter of each fibre core 246 may be selected to be and makes fibre core can support single transverse mode or multiple transverse mode.
In one embodiment, optical fiber 240 is designed to use in image intensifer 140.More specifically, inner cladding 244 and/or fibre core 246 have doping (such as erbium ion) to provide photolytic activity medium.The optical pumping (clearly not illustrating in Fig. 1) of amplifier 140 injects optical pumping ripple in inner cladding 244, and due to refractive index different of inner cladding and surrounding layer 242, the longitudinal axis of this optical pumping ripple along optical fiber 240 can guide by it.Directed optical pumping ripple is coupled to each fibre core 246 from inner cladding 244, thus provides energy source for the amplification of the light signal guided by fibre core.The diameter of inner cladding 244 makes this covering use as the multimode fibre core for optical pumping ripple, its guarantee pump energy along fibre core 246 substantial uniform distribute.
Fig. 2 E shows the sectional view of multi-core fiber 250.Optical fiber 250 comprises covering 252 and multiple fibre core 256.Fibre core 256 is distributed in covering 252, thus makes to have relatively large interval between fibre core.Due to the interval that this is relatively large, between the core in optical fiber 250, amount of crosstalk is relatively little, and it makes individual fibre core 256 can as the separately and independently pipeline for communicate optical signal.In various embodiments, each individual fibre core 256 can be designed as and supports single transverse mode or multiple transverse mode.
Fig. 2 F shows the sectional view of multi-core fiber 260.Optical fiber 260 comprises covering 262 and multiple fibre core 266.Fibre core 266 is distributed in covering 262, thus makes the interval between fibre core: (i) is enough little, and with the linear coupling of amount in generation between fibre core, and (ii) is enough large again, to produce the Non-linear coupling of a small amount of relatively between fibre core.If each fibre core 266 supports corresponding single transverse mode, then these characteristics of optical fiber 260 may be used for for this optical fiber integrally creates the definition clear-cut of relatively small amount and the transverse mode of space separation.
Fig. 2 G shows the sectional view of multi-core fiber 270.Optical fiber 270 comprises multiple fibre cores 276 of covering 272, first quantity and multiple fibre cores 278 of the second quantity.The diameter of fibre core 276 is less than fibre core 278.The spacing used in spacing between various fibre cores in optical fiber 270 and optical fiber 260 (Fig. 2 F) is similar.
The reason that optical fiber 270 comprises two kinds of different fibre core types is the transverse mode in order to produce two types characterized by different propagation constant.Not mating of propagation constant causes group velocity difference, and usually, it is conducive to the adverse effect reducing nonlinear fiber.Such as, when channel have relatively large group velocity do not mate time, the adverse effect of Cross-phase Modulation can be weakened significantly for the signal from different WDM channel.In one embodiment, fibre core 276 and 278 is distributed in whole covering 272, with the maximum space interval between the fibre core realizing identical type.
Fig. 2 H shows the sectional view of multi-core fiber 280.Optical fiber 280 comprises multiple fibre cores 286 of covering 282, first quantity and multiple fibre cores 288 of the second quantity.Although fibre core 286 is identical with the diameter of 288, they are made up of the material with different refractivity.The difference of refractive index causes fibre core 286 and 288 to have different propagation constants, and it makes optical fiber 280 can be reduced the adverse effect of nonlinear fiber by the mechanism similar in nature to the mechanism worked in optical fiber 270 (Fig. 2 G).
It will be appreciated by those skilled in the art that, except the optical fiber shown in Fig. 2 A-Fig. 2 H, the optical fiber of other types is also feasible.Such as, the fibre core with two or more different sizes can be manufactured and the multi-core fiber be made up of two or more different materials of fibre core, to realize the feature shown in Fig. 2 G and Fig. 2 H.
As used herein, term " multi-channel optical fibre " had both comprised multimode optical fiber (optical fiber 220 and 230 in such as Fig. 2 B-Fig. 2 C), comprised again multi-core fiber (the optical fiber 240-280 in such as Fig. 2 D-Fig. 2 H).
optical transmitting set
Fig. 3 A-Fig. 3 B illustrates the optical transmitting set 300 that can use in node 110 (Fig. 1) according to an embodiment of the invention.More specifically, Fig. 3 A shows the block diagram of transmitter 300.Fig. 3 B illustrates the operation of optical mode coupling (OMC) module 340 used in transmitter 300 by chart.
Fig. 3 A illustrates the transmitter 300 being coupled to communication link 120 by output optical fibre 350.Usually, optical fiber 350 is identical with the fiber type used at the direct adjacent segment place of communication link 120.As mentioned above, communication link 120 can use the optical fiber of any suitable type of those optical fiber as shown in Figure 2 to realize.Following be described as exemplary and correspond to the embodiment that output optical fibre 350 is similar to optical fiber 220 (see Fig. 2 B).Describe based on this, it will be appreciated by those skilled in the art that other embodiments how designing the transmitter 300 being suitable for optical fiber communicate optical signal being coupled to other types.
Transmitter 300 comprises laser instrument 310, and it is configured for the output beam generating specified wavelength.The beam separation generated by laser instrument 310 is N road by beam splitter 320, and by consequent N number of light beam coupling in N number of single-mode fiber 322, wherein, N be greater than one integer.Its respective beam direction to corresponding photomodulator 330, in this photomodulator 330, utilizes the data being supplied to this modulator to modulate this light beam via control signal 328 by each optical fiber 322.It should be noted, different modulators 330 or the modulator be applicable to are arranged and can be used from the different independence of control signal 328 or relevant data stream to modulate its respective light beam.In a representative configurations, each modulator 330 modulates its light beam based on the independent data stream that will transfer to the correspondence of far-end receivers from transmitter 300.The modulated optical signal produced by modulator 330 is finally as the separate modulation component of TMM signal, and it is applied to optical fiber 350 by OMC module 340.
In an alternative embodiment, laser instrument 310 can couple directly to modulator 330, or not by optical fiber but by free space coupling to this modulator.
A function of OMC module 340 is correctly coupled in optical fiber 350 by the N number of modulated light signal received by N number of single-mode fiber 332.More specifically, each modulated optical signal received by OMC module 340 is coupled in the single selected transverse mode of optical fiber 350 substantially, and wherein different modulated optical signals is coupled in different transverse modes.As used herein, " signal is coupled to single transverse mode substantially " and has two kinds of possibilities but not mutually exclusive implication.According to the first implication, it refers to that at least about 50% (may be greater than about 80% or 90%) of this signal integral energy is coupled in a selected transverse mode.According to the second implication, it refers to the part for being coupled in signal integral energy in multimode optical fiber, at least about 50% (may be greater than about 80% or 90%) of this part is coupled in a selected transverse mode, and the remainder of this part is coupled in other transverse modes.When body light signal is coupled in the single transverse mode of multimode optical fiber (such as optical fiber 350) at the most proximal end place of optical fiber by (such as OMC module 340) substantially one by one, and when therefore changing the light component of the TMM signal be emitted in this multimode optical fiber into, it is said that the light component of this TMM signal " corresponds to the single transverse mode of this multimode optical fiber " at the most proximal end place of this multimode optical fiber.
In an embodiment of transmitter 300, quantity N is chosen as identical with the sum of the transverse mode that optical fiber 350 is supported.In other words, the light signal of corresponding separate modulation can be filled in each of multimode optical fiber 350 and each transverse mode by the OMC module 340 that this embodiment of transmitter 300 uses.
Fig. 3 B graphical drawing beam shaping performed by OMC module 340.More specifically, the zones of different in Fig. 3 B shows various phase place/field strength (PFS) patterns that can be produced at the end 348 of optical fiber 350 by OMC module 340, and wherein different regions corresponds to the different optical channel of OMC module.Each PFS pattern uses color graphics to represent in figure 3b, and wherein: the saturation degree of (i) color represents distribution of light intensity, and (ii) color itself represents the phase place of this light field.Such as, the distribution of light intensity that light red is more corresponding than peony is low.From blue extremely red rainbow shape change, color represents that phase place changes from the Phase Continuation of-π to+π.
For each optical channel of OMC module 340, the PFS pattern produced at the end 348 of optical fiber 350 by this channel substantially with the PFS pattern match of transverse mode being assigned to this channel.It will be appreciated by those skilled in the art that the Mode Coupling loss of above indication may be by these PFS patterns between do not mate caused.Luminous energy corresponding to Mode Coupling loss can by intercoupling in other transverse modes of optical fiber 350, and/or completely by this optical fiber rejection.
As used herein, term " substantially mate " refers to that the difference between the PFS pattern generated by optical channel and the PFS pattern corresponding to transverse mode is relatively little, and meet two may but at least one in not mutually exclusive standard.According to the first standard, this difference is enough little, to make being coupled in corresponding transverse mode at least about 50% (may be greater than about 80% or 90%) of the gross energy of the PFS pattern generated by this optical channel.According to the second standard, this difference is enough little, to make the part be coupled in the gross energy for the PFS pattern generated by optical channel in multimode optical fiber, entering in corresponding transverse mode at least about 50% (about 80% or 90% may be greater than) of this part, and the remainder of this part enters in other transverse modes.
Different transverse modes corresponding to the different PFS patterns of Fig. 3 B use following mark to mark.Character " LP " expression " linear polarization ".In mark, " LP " numeral thereafter provides two quantization parameter values according to indicated order.For each transverse mode, the quantity of the phase increment of size in units of 2 π that first quantization parameter each position angle given about fiber axis rotates, second quantization parameter gives the quantity of the phase increment of size in units of π on fiber radius.Such as, the transverse mode being expressed as LP01 has (i) zero azimuthal phase increment, and (ii) radius phase increment.Similarly, the transverse mode being expressed as LP32 has (i) three azimuthal phase increments, and (ii) two radius phase increments.
If OMC module 340 comprises eight optical channels, then following representative mode can be used to distribute: (channel 1)-LP01, (channel 2)-LP11, (channel 3)-LP21, (channel 4)-LP02, (channel 5)-LP31, (channel 6)-LP12, (channel 7)-LP41 and (channel 8)-LP22.Skilled person will appreciate that, when not deviating from scope of the present invention and principle, other patterns can be used similarly to distribute, distribute according to these patterns, each optical channel of OMC module 340 is configured for the PFS pattern producing and mate substantially with the PFS pattern of the transverse mode of assigned optical fiber 350.
It will be appreciated by those skilled in the art that Fig. 3 B corresponds to a possible transverse mode basic set, and other each basis set comprising multiple mutually orthogonal transverse mode can similarly for realizing OMC module 340.
Fig. 4 A-Fig. 4 B illustrates the OMC module 400 that can be used as OMC module 340 (Fig. 3) according to an embodiment of the invention.More specifically, Fig. 4 A shows the block diagram of OMC module 400.Fig. 4 B shows the phase mask 420 that can use in OMC module 400.
OMC module 400 comprises two optical channels, and as directedly itself is coupled to two input optical fibres 332 (also can see Fig. 3 A).It will be appreciated by those skilled in the art that OMC module 400 can be revised as in a straightforward manner and comprise three or more optical channels.More specifically, new optical channel can create with the optical element similar for the formation of the channel 2 in OMC module 400 by increasing by one group.
OMC module 400 comprises two laser instruments 410, and each laser instrument 410 collimates in the corresponding divergent beams of OMC module by a fiber optic applications corresponding in optical fiber 332.Each collimated light beam therefore produced is through in phase mask 420 corresponding one, corresponding to phase filtering light beam 422 to produce.Then, " superposition " light beam 432 therefore produced through phase filtering light beam 422, and guides towards optical fiber 350 by multiple minute surface 430 space overlapping these two.It should be noted, minute surface 430 4the minute surface of partially transparent, and minute surface 430 1-430 3it is common opaque minute surface.Two laser instruments 442 and 446 and aperture 444 for compression (namely reducing size) union space filtered beam 432, with produce incide optical fiber 350 end 348 on output beam 452 and produce the expection superposition of PFS pattern as shown in Figure 3 B.
Depend on the transverse mode of two optical channels being assigned to OMC module 400, such as suitable selected phase mask 420 in the phase mask kind shown in Fig. 4 B 1with 420 2.Such as, if the specific light channel of OMC module 400 has been assigned the LP11 pattern of optical fiber 350, be then labeled as the phase mask of LP11 in Fig. 4 B as the phase mask 420 in this optical channel.Similarly, if the specific light channel of OMC module 400 has been assigned the LP21 pattern of optical fiber 350, be then labeled as the phase mask of LP21 in Fig. 4 B as the phase mask 420 in this optical channel, etc.The phase filtering applied by phase mask 420 and the combined effect of spatial filtering applied by aperture 444 are, this optical channel generates one that expects in the PFS pattern shown in Fig. 3 B at the end 348 of optical fiber 350, be effectively coupled in the corresponding transverse mode of this optical fiber by light signal thus from this optical channel.
It should be noted, some phase masks shown in Fig. 4 B are bifurcation phase mask (namely only locally can apply the phase mask of (such as 0 or π) in two possible phase shifts).Especially, the phase mask corresponding to LP01, LP02 and LP03 pattern is bifurcation phase mask.All the other phase masks shown in Fig. 4 B are " simulation " phase mask, because the different piece of this phase mask can apply phase shift selected in continuous print phase shift range.Analogue phase mask uses color graphics to represent in figure 4b, wherein: the color table that (i) is different is shown in the different phase shifts in continuous print 2 π interval, and the different bandwidth of (ii) same color can represent the phase shift mutually distinguished with the integral multiple of 2 π.
In one embodiment, OMC module 400 can use single relatively large continuous phase mask to replace two phase masks be separated 420 1with 420 2.This relatively large continuous phase mask is hereinafter referred to as " multisection type phase mask ", and it can comprise the phase mask in two or more Fig. 4 B in different sections (part).These sections of multisection type phase mask are arranged so that a section is used as phase mask 420 1, another section is used as phase mask 420 2.
Fig. 5 shows the block diagram that can be used as the OMC module 500 of OMC module 340 (Fig. 3) according to another embodiment of the present invention.Usually, OMC module 500 is similar to OMC module 400 (Fig. 4), and uses much identical element, such as lens 410,442 and 446, minute surface 430 and aperture 444.Being described in this and no longer repeating of these elements.But the description of following OMC module 500 concentrates on the difference between OMC module 400 and 500.
A difference between OMC module 400 and 500 is that the latter's usage space photomodulator (SLM) 520 is to replace phase mask 420.In one embodiment, SLM 520 is liquid crystal on silicon (LCOS) SLM.The representative LCOS SLM of SLM 520 can be used as in such as " Polarization Engineering for LCD Projection (the polarization engineering for LCD projection) ", describe in Chapter 11 257-275 pages in 2005, author M.G.Robinson, J.Chen, G.D.Sharp, Wiley, Chichester (Britain), it is instructed by reference and entirety is herein incorporated.Can be suitable for use as the LCOS SLM of SLM 520 also at such as U.S. Patent No. 7,268,852, No.6,940,577 and No.6,797, open in 983, it all by reference and entirety is herein incorporated.The LCOSSLM be applicable to that can be used as SLM 520 is manufactured by JVC company, and its parts as JVC projector model DLA-HD2K and selling.
SLM 520 comprises two regions 524 1with 524 2, it is configured for and performs the channel 1 of OMC module 500 and the phase filtering needed for channel 2 respectively.More specifically, region 524 1be configured for display generation and be similar to phase mask 420 1the spatial modulation pattern of the phase filtering of (see Fig. 4 A).Similarly, region 524 2be configured for display generation and be similar to phase mask 420 2the spatial modulation pattern of the phase filtering of (also seeing Fig. 4 A).
Because SLM 520 is reconfigurable devices, it may be used for dynamically changing or adjusting being presented at its zones of different, such as region 524 1with 524 2in pattern.This feature may be useful, such as make it possible to the transverse mode relatively easily changed for the different optical channels of OMC module 500 distribute, and/or when changing the features relevant that may cause multimode optical fiber 350 and producing the operating conditions of corresponding change, keep the optimal light coupling of the different optical channels of OMC module.
OMC module 500 uses two polarization beam splitters 528, suitably to guide the collimated light beam produced by lens 410 towards SLM 520, and guides the light beam through phase filtering produced by SLM towards minute surface 430.In one embodiment, quarter-wave plate (obviously not illustrating in Fig. 5) can be inserted between polarization beam splitter 528 and SLM 500, with the suitably rotary transfer polarization by the light beam of this wave plate, thus collimated light beam can be guided towards SLM by polarization beam splitter, and the light beam through phase filtering is guided towards minute surface 430.In an alternative embodiment, SLM 500 can be designed to reflection polarisation of light to be rotated into make polarization beam splitter 528 can make identical beam course.
In one embodiment, OMC module 500 may be used for producing also is the TMM signal of palarization multiplexing.Especially, if SLM 520 itself is substantially to polarization insensitive, then identical SLM may be used for processing the polarization mode being used as palarization multiplexing.
Fig. 6 shows the block diagram that can be used as the OMC module 600 of OMC module 340 (Fig. 3) according to further embodiment of this invention.Usually, the function of OMC module 600 and OMC module 400 and 500 (Fig. 4 and Fig. 5) similar.But with the difference of OMC module 400 and 500, OMC module 600 is that it uses volume hologram 620, volume hologram is generally regarded as three dimensional Phase mask.It should be noted, compared with volume hologram 620, phase mask 420 and SLM 520 generally can be regarded as film or two-dimensional phase mask.
In OMC module 600, volume hologram 620 performs at least two different functions.First function in these functions is the phase filtering function being similar to the phase mask 420 in OMC module 400 and the SLM 520 in OMC module 500.Second function in these functions is the light beam combination function being similar to minute surface 430.Because the light beam of correspondence travels through the different sub-volume of this volume hologram, therefore volume hologram 620 can by required out of phase filtering application in the different light signals received from optical fiber 332.Same because this reason, volume hologram 620 can change the direction of propagation of different light signal with different amounts.Volume hologram is known prior art, and it is in more detail in U.S. Patent No. 7,416,818, No.7,323,275 and No.6,909, and describe in 528, it is all by reference and entirety is herein incorporated.
OMC module 600 is illustratively shown as has three optical channels.Skilled person will appreciate that OMC module 600 can be revised as the optical channel with varying number in a straightforward manner.
Fig. 7 shows the block diagram of the optical transmitting set 700 that can use in node 110 (Fig. 1) according to another embodiment of the present invention.Similar with transmitter 300 (Fig. 3), transmitter 700 can optionally by the optical signal of separate modulation in the respective transversal pattern of output optical fibre (i.e. optical fiber 750).But additionally, transmitter 700 by using polarization beam splitter 714 and polarization combiner 734 in the modulation and palarization multiplexing (MPM) module 712 of this transmitter, and has palarization multiplexing (PM) ability.Transmitter 700 is illustratively shown as each polarization and has three optical channels.It will be appreciated by those skilled in the art that transmitter 700 can be revised as the channel (such as two or more than three) that each polarization has varying number in a straightforward manner.
Transmitter 700 comprises laser instrument 710, and it is configured for the output beam generating specified wavelength.Laser instrument 710 is fed to MPM module 712, and wherein the beam separation that this laser instrument generates is become the light beam 716 of mutually orthogonal polarization by polarization beam splitter 714 1with 716 2.MPM module 712 has two power splitters 720 further, and the corresponding light beam being received from polarization beam splitter 714 is separated into three tunnels by each power splitter, and by three light beam coupling to three single-mode fibers 722 obtaining thus.Its respective light beam is directed to corresponding photomodulator 730 by each optical fiber 722, in this photomodulator, utilizes the data being supplied to this modulator to modulate this light beam via control signal 728.The modulated optical signal that modulator 730 produces is coupled in single-mode fiber 732, and is directed to corresponding polarization combiner 734.The orthogonal polarization signals that two receive is incorporated in corresponding PM signal by each polarization combiner 734, then by respective single-mode fiber 736, PM signal is directed to OMC module 740.
In an alternative embodiment, transmitter 700 can use direct optically-coupled or replaces the coupling fiber at least partially shown in Fig. 7 by free space optically-coupled or supplement it.
Usually, the OMC module 740 of transmitter 700 is similar with the OMC module 340 (Fig. 3) of transmitter 300, and it is coupled to optical fiber 750 rightly for the PM signal received three.More specifically, each PM signal that OMC module 740 receives is coupled in the selected transverse mode of optical fiber 750, and wherein different PM signals is coupled in different transverse modes.For individual PM signal (it has two orthogonal polarized components), each in its polarized component all experiences phase filtering identical substantially in OMC module 740.In various embodiments, OMC module 740 can realize similarly with OMC module 400,500 and 600 (see Fig. 4-Fig. 6).But, when designing OMC module 740, the feature of its polarization manipulation should be paid special attention to, to make described OMC module can substantially to polarization insensitive.
Fig. 8 shows the block diagram of the optical transmitting set 800 that can use in node 110 (Fig. 1) according to further embodiment of this invention.Similar with each in transmitter 300 and 700 (see Fig. 3 and Fig. 7), communicate optical signal can optionally be coupled in the various transverse modes of output optical fibre (i.e. optical fiber 850) by transmitter 800.Similar with transmitter 700, transmitter 800 has palarization multiplexing ability by use three MPM modules 812, and each MPM module 812 is similar to MPM module 712 (see Fig. 7).But additionally, transmitter 800 has WDM ability.Therefore transmitter 800 use three dissimilar multiplexing: transverse mode multiplexing (TMM), palarization multiplexing (PM) and wavelength-division multiplex (WDM).
Transmitter 800 has three TMM channels, three WDM channels and two PM channels, and it makes transmitter to generate to have the TMM signal up to 18 separate modulation communicate optical signals (each transverse mode of being excited is up to six).It will be appreciated by those skilled in the art that transmitter 800 can be revised as the separate modulation component that can generate varying number in a relatively simple manner, and couple it in the selected transverse mode of optical fiber 850 in the mode of any desired.
Each WDM channel of transmitter 800 has respective laser instrument 810, and the wavelength that its generation is specified also is applied to respective MPM module 812.Three outputs of MPM module 812 are applied to optical filter (OF) 818, and it performs the bandpass filtering of relative close, with the crosstalk between reducing corresponding to the light signal of different WDM channel.In multiplexer 826, carry out WDM through filtering signal multiplexing, consequent WDM signal is directed to OMC module 840 by single mode or integrated optical fiber 836.
Usually, the OMC module 840 of transmitter 800 is similar with the OMC module 340 (Fig. 3) of transmitter 300, and it is coupled to optical fiber 850 rightly for the WDM signal received three.More specifically, each WDM signal that OMC module 840 receives is coupled in the selected transverse mode of optical fiber 850, and wherein different WDM signal is coupled in different transverse modes.Although the PFS pattern corresponding to the transverse mode of multimode optical fiber depends on wavelength, the typical light bands of a spectrum relative narrower used in a wdm system, this makes it possible to use identical phase mask for all WDM channels in practice.Such as, centered by about 1550nm, the overall width variance of band on overall spectrum band in carrier frequency that be about 100nm only have an appointment 6%.Due to the variance that this is relatively little, will enough be competent in all wavelengths of these bands of a spectrum for the phase mask be arranged in close to the Wavelength design of this band middle.Therefore, in various embodiments, OMC module 840 can realize similarly with OMC module 400,500 and 600 (see Fig. 4-Fig. 6).
optical receiver
As be known in the art, the transverse mode of multi-channel optical fibre stands intermode mixing when its length direction along this optical fiber is propagated.Usually, the impact of intermode mixing is stronger in multimode optical fiber.But relatively strong intermode mixing (such as, crosstalk between core) also may be there is in the multi-core fiber with the fibre core of relative close arrangement.Therefore, even if signal of communication is coupled in specific single transverse mode in the front end of multi-channel optical fibre, at the far-end of this optical fiber, the contribution that other transverse modes also will have from this signal of communication.Therefore, need to perform quite a large amount of signal transacting, fully to recover the data of being carried by the different separate modulation components of TMM signal at receiver.Usually, in order to N number of separate modulation component of TMM signal of decoding, receiver needs at least N number of independent sample obtaining this signal.Usually, be applied to the signal transacting of these samples based on diagonalization of matrix algorithm, target is the impact of the intermode mixing reversed in this multi-channel optical fibre.
Fig. 9 shows the block diagram of the optical receiver 900 that can use in node 110 (Fig. 1) according to an embodiment of the invention.Receiver 900 can be configured for and such as receive input TMM signal 902 from link 120.TMM signal 902 is applied to tap module 910 to produce K sample 912 of this TMM signal, wherein K be greater than one positive integer.Each sample 912 by correspondence coherent detector 930, use the LO signal 922 supplied by local oscillator (LO) source 920 to carry out relevant detection.The testing result generated from sample 912 by coherent detector 930, the in-phase component I of such as sample and quadrature component Q, is applied to digital signal processor (DSP) 940.For each Signal transmissions interval (such as bit period), DSP 940 suitably processes by coherent detector 930 1-930 kthe one whole group of testing result generated, to generate output stream 942.If tap module 910 produces the sample of enough TMM signals 902, then DSP 940 can recover and export the initial all data being encoding to TMM signal by remote transmitters by stream 942, and wherein this TMM signal is received by receiver 900 as TMM signal 902.
It will be appreciated by those skilled in the art that a function of DSP 940 is reversed by the mode mixture matrix corresponding to link 120.Usually, link condition changes in time, therefore causes mode mixture matrix also to change, usually in millisecond magnitude or slower.In one embodiment, DSP 940 is configured for and follows link condition variation adaptively.Such as, as be known in the art, DSP 940 can use blind adaptive MUD to learn link condition and to adapt to this link condition.Alternatively or additionally, the controller 950 being coupled to DSP 940 may require that remote transmitters sends training sequence to receiver 900 again and again, obtains present mode hybrid matrix for DSP.The representative training sequence being applied to link 120 by remote transmitters can have TMM signal, wherein by the transverse mode that known order sequential energisation is different, makes to only have a transverse mode to be energized in any preset time.The signal transacting realized in DSP940 also may compensate some Nonlinear perturbations, the phase shift such as introduced by its mode and cross-mode nonlinear fiber.
Figure 10 A-Figure 10 B shows the typical module that can use in receiver 900 (Fig. 9) according to an embodiment of the invention.More specifically, Figure 10 A shows the block diagram of the tap module 1010 that can use as tap module 910.Figure 10 B shows the block diagram of the coherent detector 1030 that can use as coherent detector 930.
With reference to Figure 10 A, tap module 1010 receives TMM signal 902 by multimode optical fiber 1002.The divergent beams that collimation lens 1004 pairs of optical fiber 1002 produce collimate, and guide consequent collimated light beam towards K-1 partially transparent minute surface 1006 1-1006 k-1with the nontransparent minute surface 1006 of end k.In one implementation, the reflectivity of different minute surfaces 1006 causes the light beam 1012 from this mirror-reflection 1-1012 kthere is approximately uniform intensity.
With reference to Figure 10 B, detecting device 1030 receives the LO signal 922 from LO source 920 by single-mode fiber 1016.The divergent beams that collimation lens 1018 pairs of optical fiber 1016 produce collimate, and guide consequent collimated light beam towards phase mask 1020.Usually, phase mask 1020 is similar with phase mask 420 (see Fig. 4 A-Fig. 4 B).More specifically, phase mask 1020 produces the light beam 1022 through phase filtering with PFS pattern, and this PFS pattern is expansion (amplification) version of the PFS pattern of the selected transverse mode corresponding to multimode optical fiber 1002 (Figure 10 A).As mentioned above, Fig. 4 B shows the kind of phase mask, and wherein each is all suitable for using as phase mask 1020.When each detecting device 930 in receiver 900 uses detecting device 1030 to realize, the different instances of the detecting device 1030 in receiver has different phase masks 1020 (the out of phase mask such as selected from kind shown in Fig. 4 B) usually.In various embodiments, these different phase masks 1020 can be implemented by the different sections of multistage phase mask, or use the different piece being similar to the SLM of SLM 520 (Fig. 5) to implement.
Be applied to the optical mixer 1026 of 2x4 through the light beam 1022 of phase filtering and light beam 1012 (its carrying TMM sample 922, is shown in Fig. 9 and Figure 10 A), both impact to produce four interference signals 1032 mutually wherein 1-1032 4.Each interference signal 1032 1-1032 4be applied to corresponding photodetector (such as photodiode) 1034, to be converted into corresponding electric signal.The electric signal generated by photodetector 1034 is digitized and is directed to the further process in DSP940.The optical mixer of the 2x4 that can use as the mixer 1026 in detecting device 1030 is known in the prior art, its representative example is such as being submitted on Dec 18th, 2008: (i) U.S. Patent Application Publication No.2007/0297806 and (ii) U.S. Patent application No.12/338, open in 492, both by reference whole and entirety is herein incorporated.
Interference signal 1032 1-1032 4electric field E 1-E 4provide respectively by formula (1):
E 1 E 2 E 3 E 4 = 1 2 E S - E LO - j E S - j E LO - j E S - j E LO e jπ / 2 - E S + E LO e jπ / 2 - - - ( 1 )
Wherein, E sand E lObe respectively the electric field of light signal 1012 and 1022.It should be noted, formula (1) is applicable to each point of the lateral cross section of light beam 1032.This means detecting device 1030 not only measuring beam 1012 and 1022 how to impact mutually in time, also detect them and spatially how to impact mutually.Further, due to the mutual orthogonality of the different transverse modes of optical fiber 1016, the different instances with the detecting device 1030 of out of phase mask 1020 measures the electric field of the different transverse modes corresponding to TMM signal 902 effectively.Skilled person will appreciate that, if K >=N, then coherent detector 930 (or 1030) generates enough sample datas, mode mixture matrix corresponding to communication link 120 can be reversed rightly to make DSP 940, and recover data entrained by the separate modulation component of TMM signal, wherein this TMM signal distally transmitter (such as transmitter 300) be emitted to receiver 900 by communication link 120.
Figure 11 shows the block diagram of the tap module 1110 that can use as tap module 910 according to another embodiment of the present invention.Tap module 1110 comprises multimode optical fiber 1102, receives TMM signal 902 by this multimode optical fiber 1102.Along the length direction of optical fiber 1102, tap module 1110 has K multimode optical fiber (MMF) coupling mechanism 1106 1-1106 kwith K-1 pattern scrambler 1108 2-1108 k.Each MMF coupling mechanism 1106 is fiber optic tap, and it shunts a part of TMM signal 902 and by this partial coupling in corresponding single-mode fiber 1110.By optical fiber 1110 1-1110 kthe signal 1112 carried 1-1112 krespectively as the sample 912 in receiver 900 1-912 k.
Each signal 1112 indicates the linear combination of the transverse mode existed in the multimode optical fiber 1102 of the position of the MMF coupling mechanism 1106 in correspondence.Due to pattern scrambler 1108 2-1108 kby MMF coupling mechanism 1106 1-1106 kbetween transverse mode mix, therefore each signal 1112 1-1112 kthe different linear combinations of the transverse mode in instruction multimode optical fiber 1102.Skilled person will appreciate that, if K >=N, then coherent detector 930 generates enough sample datas, mode mixture matrix corresponding to communication link 120 can be reversed rightly to make DSP 940, and recover the data of being carried by the separate modulation component of TMM signal, wherein this TMM signal distally transmitter (such as transmitter 300) be emitted to receiver 900 by communication link 120.
In one embodiment, receiver 900 comprises tap module 1110, and it can use as coherent detector 930, and wherein coherent detector is designed for and detects PM signal.Coherent detector for detecting PM signal is known in the prior art and be disclosed in such as above-mentioned U.S. Patent Application Publication No.2007/0297806 and U.S. Patent application No.12/338, in 492.It will be appreciated by those skilled in the art that and use the receiver 900 of tap module 1110 and multiple coherent detector for detecting PM signal can suitably detect the light signal utilizing the multiplexing generation of TMM and PM.The receiver 900 that the WDM receiver that what those skilled in the art will be further understood that it is possible to suitably detects the light signal using above-mentioned whole three kinds of duplex type (i.e. TMM, PM and WDM) to produce can all have TMM and PM function by deployment for each WDM channel of WDM receiver is formed.
Figure 12 shows the block diagram of the optical receiver 1200 that can use in node 110 (Fig. 1) according to another embodiment of the present invention.Receiver 1200 receives TMM signal (such as from link 120) by multimode optical fiber 1202.Collimation lens 1204 1the divergent beams that optical fiber 1202 produces are collimated, and consequent collimated light beam 1205 is guided towards beam splitter 1206 1-1206 4.In one embodiment, each beam splitter 1206 is translucent minute surface.
Receiver 1200 also comprises and being exported through collimation lens 1204 2to form the LO source 1220 of collimation LO light beam 1221.Similar with light beam 1205, LO light beam 1221 is also guided towards beam splitter 1206 1-1206 4.Be positioned at beam splitter 1206 1with 1206 2between 90 ° of phase shifters 1208 phase shift of 90 ° is introduced into via its transmission light beam in.
Beam splitter 1206 1-1206 4suitably light beam 1205 and 1221 is separated into multiple beamlet, and then a part of recombinating in these beamlets is to generate four mixed light beams, it is incident on four array detectors (such as CCD) 1230 1-1230 4pixelation receiving surface on, wherein mixed light beam produces corresponding interference figure at this place.Each array detector 1230 operates with sufficiently high speed, can catch and export the data of Signal transmissions interval (such as symbol period) at least one interference figure corresponding to each TMM signal 1201.Each interference figure at the pixelation receiving surface place of array detector 1230, the light field of the reference field generated by LO source 1220 by impinging upon one another and TMM signal 1201 and generating.Array detector 1230 catches interference figure by the light intensity of the multiple pixel places measured pattern at this array detector, thus generates the two-dimensional section intensity corrugated (profile) of mixed light beam.
Correspond to by array detector 1230 1-1230 4the data of four interference figures detected are provided to DSP 1240 and process.If array detector 1230 1-1230 4have sufficiently high resolution (such as enough a large amount of relatively little pixels), then DSP 1240 receives enough data from four interference figures, to determine the pattern composition of TMM signal 1201.At this, term " pattern composition " refers to that TMM signal 1201 is with the form of expression of the transverse mode of multimode optical fiber 1202.Typically, this linear combination taking the form of the transverse mode of suitable weighting.Then, the knowledge of relevant pattern composition makes DSP can reverse mode mixture matrix corresponding to communication link 120 rightly, and recover the data of being carried by the separate modulation component of TMM signal, wherein this TMM signal distally transmitter (such as transmitter 300) be emitted to receiver 1200 by communication link 120.DSP 1240 exports the data be resumed by data stream 1242.
It will be understood by those of skill in the art that, array detector 1230 2with 1230 4be selectable, it is used in receiver 1200 the balance detection scheme realizing being similar to and realize in detecting device 1030.More specifically, by array detector 1230 1-1230 4four interference figures detected are processed by DSP 1240, to generate two sectional views of TMM signal 1201.First sectional view is the same phasor of TMM signal 1201, and the second sectional view is the orthogonal graph of TMM signal 1201.Same phasor and the orthogonal graph with TMM signal 1201 may be favourable because DSP 1240 can use these figure to come sooner, more accurately and/or more effectively determine the pattern composition of TMM signal.
In various embodiments, receiver 1200 can comprise other optical module, is less than four array detectors be separated using.Such as, in one embodiment, receiver 1200 can have two relatively large array detectors, wherein: (i) first detecting device be subregion, make a part for the first detecting device as array detector 1230 1, and another part of the first detecting device is as array detector 1230 2, and (ii) is similar, the second detecting device is subregion, makes a part for the second detecting device as array detector 1230 3, and another part of the second detecting device is as array detector 1230 4.In an alternative embodiment, receiver 1200 can have a very large array detector, and it can be divided into four parts, and each part is as detecting device 1230 1-1230 4one of middle correspondence.
Although the present invention is described in this with reference to illustrated embodiment, this instructions is not intended to explain in defined meaning.For those skilled in the art in the invention it is apparent that be considered to fall in the principle and scope of the present invention expressed by claims to the various amendment of described embodiment and other embodiments of the present invention.
Unless otherwise described clearly, otherwise each numerical value and scope should be interpreted as approximate value, as before word " approximately " or " approx " are positioned at the numerical value of this numerical value or scope.
Will be further understood that, when not departing from the scope of the invention described by claims, those skilled in the art can carry out various change in order to explain that essence of the present invention describes with the details of illustrated parts, material and layout.
If any, although the mark that the element in following methods claim is corresponding is recorded with specific order, record except non-claimed otherwise implies the particular order of some or all for implementing those elements, otherwise those elements do not need restriction to implement with this particular order.
Here " embodiment " mentioned or " embodiment " refer to and can to comprise at least one embodiment of the present invention in conjunction with the special characteristic described by this embodiment, structure or characteristic.The phrase " in one embodiment " that many places occur in the description does not need all to relate to identical embodiment, and independent or interchangeable embodiment does not need other embodiments mutually exclusive yet.More than be equally applicable to term " realization ".
Also be for illustrative purposes, term " coupling ", " connection " refer to prior art known or any-mode that the permission energy of later exploitation transmits between two or more elements, and it is contemplated that and insert one or more add ons, although this is not necessarily.On the contrary, there is not this add ons in term " direct-coupling ", " directly connecting " etc. hint.
The present invention may implement with other specific equipment and/or method.Described embodiment can think in all respects be only used to illustrate and unrestricted.Especially, scope of the present invention is shown by claims, but not is shown by instructions herein and accompanying drawing.The all changes of carrying out in the implication of equal value and scope of claims will be included within the scope of it.
Instructions and accompanying drawing merely illustrate principle of the present invention.Therefore will understand, although do not describe clearly at this or illustrate, those of ordinary skill in the art can design multiple layout to implement principle of the present invention, and it is also included within the spirit and scope of the present invention.Further, all examples are mainly intended to clearly only for teaching purpose listed herein, help reader understanding's principle of the present invention and the concept that proposed by inventor, with push technological development, it should be understood to be not limited to this specific example enumerated and situation.In addition, this describe in detail principle of the present invention, in and the description of embodiment, and its particular example is intended to comprise its equivalencing.
Those of ordinary skill in the art should recognize, are the concept map of the exemplary circuit represented for implementing principle of the present invention at this any block diagram.Similarly, it is to be appreciated that, any flow table, process flow diagram, state transition diagram, false code and the multiple process of similar expression, whether it can be represented by computer-readable medium substantially and be performed by computing machine or processor, illustrate clearly regardless of this computing machine or processor.

Claims (16)

1. an optical receiver, comprising:
Tap module, it is configured for samples to the multiplexing TMM signal of the light transverse mode with N number of separate modulation component, to produce K light sample at each Signal transmissions interval, N and K be greater than 1 positive integer, wherein K >=N;
Local oscillator LO source, it is configured for and produces light LO signal;
K coherent detector, each coherent detector is optically coupled to described tap module and described LO source, and is configured for:
By corresponding light sample and the mixing of described LO signal, to produce one or more optical interference signals; And
Described one or more optical interference signals is converted to the instruction in-phase component of this light sample and one or more electric signal of quadrature component; And
Digital signal processor DSP, its operability is coupled to this K coherent detector and is configured for the electric signal processing and produced by described coherent detector, to recover the data of being carried by each separate modulation component of N number of separate modulation component of this TMM signal, wherein:
Described optical receiver is configured for by supporting that the multimode optical fiber of multiple transverse mode receives described TMM signal; And
Coherent detector comprises:
Phase mask, it is configured for and carries out phase filtering to this LO signal, and to produce through phase filtering light beam, wherein said phase mask makes the described PFS pattern through phase filtering light beam with the phase place/field strength PFS pattern corresponding to selected transverse mode;
Optical mixer, it is configured for and (i) is mixed through phase filtering light beam with (ii) is described, to generate described one or more optical interference signals corresponding to the light beam of corresponding light sample; And
Multiple photodetector, described one or more optical interference signals is converted to described one or more electric signal by it.
2. optical receiver according to claim 1, wherein:
Described TMM signal experienced intermode and mixes before being received by described optical receiver in described multimode optical fiber; And
Described DSP is configured for the impact mixed by described intermode and reverses to recover described data.
3. optical receiver according to claim 1, comprise controller further, its operability is coupled to described DSP, and be configured for distally transmitter and send request, to send light training signal to this optical receiver, wherein this DSP is configured for derives mode mixture matrix corresponding to this multimode optical fiber based on this training signal.
4. optical receiver according to claim 1, wherein at least two different coherent detectors have different phase masks.
5. optical receiver according to claim 4, wherein said different phase mask is embodied as the different sections of multisection type phase mask.
6. optical receiver according to claim 1, wherein said tap module comprises:
K multimode optical fiber MMF coupling mechanism, wherein eachly branches to single-mode fiber by luminous power from this multimode optical fiber, to produce the light sample of the correspondence of this TMM signal; And
K-1 pattern scrambler, between each MMF coupling mechanism being arranged in two vicinities.
7. optical receiver according to claim 1, wherein said multimode optical fiber support amounts to N number of transverse mode.
8. optical receiver according to claim 1, wherein:
At the far-end of described multimode optical fiber, each separate modulation component of described TMM signal corresponds to the corresponding single transverse mode of described multimode optical fiber.
9. an optical receiver, comprising:
Tap module, it is configured for samples to the multiplexing TMM signal of the light transverse mode with N number of separate modulation component, to produce K light sample at each Signal transmissions interval, N and K be greater than 1 positive integer, wherein K >=N, and described tap module is by supporting that the multimode optical fiber of multiple transverse mode receives described TMM signal;
Local oscillator LO source, it is configured for and produces light LO signal;
K coherent detector, each coherent detector is optically coupled to described tap module and described LO source, and is configured for:
Carry out phase filtering to described LO signal, to produce through phase filtering light beam, described have the PFS pattern corresponding to the phase place/field strength PFS pattern of the corresponding selected transverse mode of described multimode optical fiber through phase filtering light beam;
By corresponding light sample and the mixing of described LO signal, to produce one or more optical interference signals; And
Described one or more optical interference signals is converted to the instruction in-phase component of this light sample and one or more electric signal of quadrature component; And
Digital signal processor DSP, its operability is coupled to this K coherent detector and is configured for the electric signal processing and produced by described coherent detector, to recover the data of being carried by each separate modulation component of N number of separate modulation component of this TMM signal.
10. an optical receiver, comprising:
Multiple beam splitter, it is configured for:
I the beam separation corresponding to light transverse mode multiplexing TMM signal is multiple beamlets of the first quantity by (), wherein this TMM signal has multiple separate modulation component, and it is by supporting that the multimode optical fiber of multiple transverse mode receives;
(ii) multiple beamlets that the beam separation of local oscillator L0 signal is the second quantity will be corresponded to; And
(iii) beamlet of the beamlet of the first quantity and the second quantity is mixed to generate two or more mixed light beams;
First array detector, it has corresponding pixelation receiving surface and is configured for the first two-dimentional interference figure detecting the first mixed light beam corresponding to these two or more mixed light beams;
Second array detector, it has correspondingly pixelation receiving surface and is configured for the second two-dimentional interference figure detecting the second mixed light beam corresponding to these two or more mixed light beams; And
Digital signal processor DSP, it is operatively coupled to this first and second array detector, and be configured for this first and second two-dimentional interference figure of process, to determine the pattern composition of this TMM signal, and form the data of recovering to be carried by the separate modulation component of this TMM signal based on described pattern.
11. optical receivers according to claim 10, wherein:
Each in this first and second array detector is all configured for and at least obtains once one corresponding in this first and second two-dimentional interference figure at each Signal transmissions interval of this TMM signal.
12. optical receivers according to claim 10, comprise phase shifter further, it causes having specific phase shift from the first beamlet of multiple beamlets of this second quantity relative to the second beamlet of the multiple beamlets from this second quantity, wherein, and the plurality of beam splitter:
I () mixes by the first beamlet of the multiple beamlets from this first quantity with from the first beamlet of multiple beamlets of this second quantity, to generate this first mixed light beam; And
(ii) mix by the second beamlet of the multiple beamlets from this first quantity with from the second beamlet of multiple beamlets of this second quantity, to generate this second mixed light beam.
13. optical receivers according to claim 12, wherein this specific phase shift is approximate 90 degree.
14. optical receivers according to claim 12, it comprises further:
3rd array detector, it has corresponding pixelation receiving surface and is configured for the 3rd two-dimentional interference figure detecting and correspond to the 3rd mixed light beam; And
4th array detector, it has corresponding pixelation receiving surface and is configured for the 4th two-dimentional interference figure detecting and correspond to the 4th mixed light beam, wherein
This phase shifter causes having this specific phase shift from the 3rd beamlet of multiple beamlets of this second quantity relative to the 4th beamlet of the multiple beamlets from this second quantity and each of described second beamlet;
The plurality of beam splitter:
(iii) mix by the 3rd beamlet of the multiple beamlets from this first quantity with from the 3rd beamlet of multiple beamlets of this second quantity, to generate the 3rd mixed light beam; And
(iv) mix by the 4th beamlet of the multiple beamlets from this first quantity with from the 4th beamlet of multiple beamlets of this second quantity, to generate the 4th mixed light beam; And
This DSP is operatively coupled to this third and fourth array detector, and is configured for this third and fourth interference figure of process, to determine the pattern composition of this TMM signal.
15. optical receivers according to claim 14, wherein, described array detector and DSP realize balance detection scheme, wherein:
This first and the 3rd two-dimentional interference figure be processed the same phasor generating this TMM signal;
This second and the 4th two-dimentional interference figure be processed the orthogonal graph generating this TMM signal; And
Described same phasor and orthogonal graph are processed the pattern composition determining this TMM signal.
16. optical receivers according to claim 10, wherein said first and second array detectors are embodied as the different piece of same larger array detector.
CN201080028849.XA 2009-06-26 2010-06-18 Receiver for optical transverse-mode-multiplexed signals Expired - Fee Related CN102461021B (en)

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US12/492,399 US8320769B2 (en) 2009-06-26 2009-06-26 Transverse-mode multiplexing for optical communication systems
US12/492,391 2009-06-26
US12/492,391 US8355638B2 (en) 2009-06-26 2009-06-26 Receiver for optical transverse-mode-multiplexed signals
US12/492,399 2009-06-26
PCT/US2010/039101 WO2010151484A1 (en) 2009-06-26 2010-06-18 Receiver for optical transverse-mode-multiplexed signals

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