CN102461021A

CN102461021A - Receiver for optical transverse-mode-multiplexed signals

Info

Publication number: CN102461021A
Application number: CN201080028849XA
Authority: CN
Inventors: R-j·埃西安布尔; R·赖夫; P·J·温泽尔
Original assignee: Alcatel Optical Networks Israel Ltd
Current assignee: Alcatel Optical Networks Israel Ltd; Nokia of America Corp
Priority date: 2009-06-26
Filing date: 2010-06-18
Publication date: 2012-05-16
Anticipated expiration: 2030-06-18
Also published as: CN102461021B; WO2010151484A1; JP2012533915A; KR101355011B1; KR20120040202A; JP2013243682A; JP5587467B2; EP2446560A1

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

The receiver that is used for light transverse mode multiplexed signals

The cross reference of related application

The application's theme relates to R.-J.Essiambre, R.Ryf and P.Winzer's; Act on behalf of case and be numbered Essiambre 22-36; 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 that is used for optical communication system is multiplexing) ", 399, and it all is 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 supporting the transverse mode multiplexing (TMM) in the optical communication system.

Background technology

This part is introduced and can be helped to be convenient to understand better aspects of the present invention.Correspondingly, the description of this part should be from reading in this respect, and should not be understood that to admit which is that prior art or which are not prior aries.

Wireless communication system with multiple-input and multiple-output (MIMO) function has improved the total transmission capacity through exploitation (rather than attempting to alleviate) multidiameter broadening in wireless channel.More specifically, radio MIMO is through using many antennas to improve efficient and reliability at reflector and receiver place.The raising of the average throughput that is caused thus is that cost realizes with signal processing and hard-wired bigger complexity, and is not to be cost with the spectral bandwidth or the higher signal power that increase.

In optical communication system, for example,, be feasible so be used to improve the MIMO mode of transmission capacity because the multidiameter of the modal dispersion of multimode fiber and wireless transmission medium is similar.Therefore, light MIMO can be used for developing the intrinsic high-transmission capacity of multimode fiber.But, be used to implement the also not fully development of hardware of light MIMO.

Summary of the invention

The various embodiment of the optical receiver that is used for light transverse mode multiplexing (TMM) signal are disclosed at this.A kind of representative optical receiver of the present invention receives the TMM signal through the multimode fiber of supporting multiple transverse mode.This optical receiver comprises that a plurality of operability are coupled to the photodetector of digital signal processor, and this digital signal processor configuration is used to handle this TMM signal, forms to confirm its pattern.Form based on determined pattern, this optical receiver carries out demodulation to each separate modulation component of TMM signal, to recover being encoding to the data on this TMM signal at far-end reflector place.

According to an embodiment, a kind of optical receiver is provided, it comprises: (A) tap module; Its configuration is used for the light TMM signal with N separate modulation component is sampled; To produce K light sample at each signal transmission intercal, N and K are the positive integer greater than, wherein K >=N; (B) local oscillator (LO) source, its configuration is used to generate light LO signal; And (C) K coherent detector, each coherent detector is optically coupled to this tap module and LO source.In this K coherent detector each all disposes and is used for (i) with corresponding light sample and this LO signal mixing, to generate one or more optical interference signals; And (ii) convert said one or more optical interference signals into the in-phase component of this light sample of indication and one or more signals of telecommunication of quadrature component.This optical receiver further comprises digital signal processor (DSP); Its operability is coupled to this K coherent detector; And configuration is used to handle the signal of telecommunication that is produced by coherent detector, to recover each the entrained data by N separate modulation component of TMM signal.This optical receiver receives this TMM signal through the multimode fiber of supporting multiple transverse mode.At the remote terminal of this multimode fiber, each separate modulation component of this TMM signal is corresponding to the corresponding single transverse mode of multimode fiber.

According to another embodiment, a kind of optical receiver is provided, it comprises tap module; Configuration is used for the light TMM signal with N separate modulation component is sampled; To produce K light sample at each signal transmission intercal, N and K are the positive integer greater than, wherein K >=N.This tap module receives this TMM signal through the multimode fiber of supporting multiple transverse mode.This optical receiver further comprises (i) local oscillator (LO) source, and its configuration is used to generate light LO signal; And (ii) K coherent detector, each coherent detector is optically coupled to this tap module and LO source.In this K coherent detector each all disposes and is used for: (a) this LO signal is carried out phase filtering; To produce accordingly through the phase filtering light beam, it has the PFS pattern corresponding to the phase place/field intensity of the corresponding selected transverse mode of this multimode fiber (PFS) pattern; (b) corresponding light sample and this are mixed through the phase filtering light beam, to generate one or more optical interference signals; And (iii) convert said one or more optical interference signals into the in-phase component of this light sample of indication and one or more signals of telecommunication of quadrature component.This optical receiver further comprises digital signal processor (DSP); Its operability is coupled to this K coherent detector; And configuration is used to handle the signal of telecommunication that is produced by this coherent detector, the data of carrying with each the separate modulation component that recovers by N separate modulation component of this TMM signal.

According to another embodiment; A kind of optical receiver is provided; It comprises a plurality of beam splitters; Its configuration is used for: will be a plurality of beamlets of first quantity corresponding to the beam separation of light TMM signal (i), wherein this TMM signal has a plurality of separate modulation components, and receives via the multimode fiber of supporting multiple transverse mode; To corresponding to the beam separation of local oscillator (LO) signal a plurality of beamlets of second quantity (ii); And (iii) will mix to generate two or more mixed light beams from the beamlet of this first quantity and second quantity.This optical receiver further comprises: (a) first array detector, its configuration are used to detect first interference figure corresponding to first mixed light beam of these two or more mixed light beams; (b) second array detector, its configuration are used to detect second interference figure corresponding to second mixed light beam of 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 configuration is used to handle this first and second interference figure; Pattern to confirm this TMM signal is formed, and forms based on said pattern, recovers by the entrained data of the separate modulation component of this TMM signal.

According to another embodiment, a kind of optical receiver is provided, it comprises tap module; Its configuration is used for the light transverse mode with N separate modulation component multiplexing (TMM) signal is sampled; To produce K light sample at each signal transmission intercal, N and K are the positive integer greater than, wherein K >=N.This optical receiver further comprises (i) local oscillator (LO) source, and its configuration is used to generate light LO signal; And (ii) K coherent detector, each coherent detector is optically coupled to this tap module and LO source.In this K coherent detector each all disposes and is used for (a) with corresponding light sample and the mixing of LO signal, to generate one or more optical interference signals; And (b) said one or more optical interference signals are converted into in-phase component and one or more signals of telecommunication of quadrature component of this light sample of indication.This optical receiver further comprises digital signal processor (DSP); Its operability is coupled to this K coherent detector; And configuration is used to handle the signal of telecommunication that is produced by this coherent detector, to recover the entrained data of each separate modulation component by N separate modulation component of this TMM signal.This optical receiver receives this TMM signal through the multimode fiber of supporting multiple transverse mode.This tap module comprises: (A) K multimode fiber (MMF) coupler, and each coupler is tapped into monomode fiber with luminous power from this multimode fiber, to produce the corresponding light sample of this TMM signal; And (B) K-1 pattern scrambler, its each be arranged between the MMF coupler of two vicinities.

Description of drawings

Comprise at least one secondary coloured picture in this patent or the application documents.After should asking and paying necessary fee, this patent or the disclosed copy of patent application that have coloured picture will be provided by official.

Through the mode of example, from following detailed description and accompanying drawing, other aspects, characteristic and the advantage of various embodiments of the invention will become more fully obviously, wherein:

Fig. 1 shows the block diagram of the optical communication system that can put into practice various embodiments of the invention;

Fig. 2 A-Fig. 2 H shows the sectional view according to the optical fiber that can in the system of Fig. 1, use of various embodiments of the invention;

Fig. 3 A-Fig. 3 B illustrates the optical transmitting set that can in the node of system shown in Figure 1, use according to an embodiment of the invention;

Fig. 4 A-Fig. 4 B illustrates optical mode coupling (OMC) module that can in the reflector of Fig. 3, use according to an embodiment of the invention;

Fig. 5 shows the block diagram of the OMC module that can in the reflector of Fig. 3, use according to another embodiment of the present invention;

Fig. 6 shows the block diagram according to the OMC module that can in the reflector of Fig. 3, use of further embodiment of this invention;

Fig. 7 shows the block diagram of the optical transmitting set that can in the node of system shown in Figure 1, use according to another embodiment of the present invention;

Fig. 8 shows the block diagram according to the optical transmitting set that can in the node of system shown in Figure 1, use of further embodiment of this invention;

Fig. 9 shows the block diagram of the optical receiver that can in the node of system shown in Figure 1, use according to an embodiment of the invention;

Figure 10 A-Figure 10 B shows the tap module and the coherent detector that can in optical receiver shown in Figure 9, use according to an embodiment of the invention;

Figure 11 shows the tap module that can in optical receiver shown in Figure 9, use according to another embodiment of the present invention; And

Figure 12 shows the block diagram of the optical receiver that can in the node of system shown in Figure 1, use according to another embodiment of the present invention.

Embodiment

Optical communication system

Fig. 1 shows the block diagram of the optical communication system 100 that can put into practice various embodiments of the invention.System 100 comprises a plurality of communication nodes 110 through the network interconnection of optical communication link 120.System 100 further comprises optical add/drop multiplexer (ADM) 130, image intensifer 140 and optical cross-connect 150, and it all is inserted between the node 110 with various forms.

Each node 110 has light multiple-input and multiple-output (MIMO) function through using transverse mode multiplexing (TMM) to realize.Node 110 generally comprises optical transmitting set and optical receiver (all clearly not illustrating among Fig. 1), with the two-way communication between the various nodes of back-up system 100.Except TMM was multiplexing, each node 110 also can use wavelength division multiplexing (WDM) and/or palarization multiplexing (PM), and perhaps the both uses.Below at the corresponding paragraph of this specification the optical transmitting set that can in individual nodes 110, use and the exemplary embodiment of receiver will be described in further detail.

Each optical communication link 120 is through using one or more realization the in following: (i) monomode fiber; (ii) multimode fiber; (iii) multi-core fiber; (iv) monomode fiber bundle.In one embodiment, the transverse mode between the multimode fiber that uses in the link 120 is supported two kinds to about 100 kinds.In alternative, the multimode fiber support surpasses 100 kinds of transverse modes.In one embodiment, each fibre core of the multi-core fiber that uses in the link 120 is supported single transverse mode.In alternative, the some or all of fibre cores of multi-core fiber are supported multiple transverse mode, and this multi-core fiber super model as a whole.

As use, term " transverse mode " is meant the guided electromagnetic wave that (promptly horizontal) has electric field or Distribution of Magnetic Field (after this being called optical field distribution) in the plane perpendicular to the direction of propagation, it is irrelevant with propagation distance substantially. hereMore specifically; If the loss of the luminous power in the optical fiber or the factor of gain are excluded; The optical field distribution of this pattern of then measuring along two diverse location places of optical fiber is the difference owing to the factor of the overall phase transformation of reflection only, and this phase transformation is formed by the pattern between these two positions.Every kind of transverse mode is an eigen mode of optical fiber, and different transverse modes is mutually orthogonal.Usually, optical fiber can be supported the transverse mode of fixed qty, and its optical field distribution and propagation constant are confirmed by waveguiding structure, material behavior and optical frequency (wavelength) clearly.It should be noted that the notion of transverse mode is applicable to the polytype optical fiber that comprises multi-core fiber.For example, the transverse mode of the individual fibre core of multi-core fiber also is the transverse mode of this multi-core fiber as a whole.

In one embodiment, optical add/drop multiplexer 130 is reconfigurable add-drop multiplexer.Because link 120 typically has the characteristic that the intermode of relative altitude mixes, node 110 generally needs to receive all transverse modes with identical optical frequency (wavelength), with the data of correctly handling the TMM signal and recovering to be carried by this signal.Therefore, multiplexer 130 is designed to (i) and tells all transverse modes with identical optical frequency from input link 120, and/or (ii) inserts with identical optical frequency all to output link 120 and insert transverse mode.In other words, multiplexer 130 is realized conventional WDM drop and insert feature, but the multiplexing integral body of the TMM of each specific wavelength is worked.

For the function of supporting to expect, multiplexer 130 use arrowbands, the type optical filter that interweaves, it has identical substantially transmission feature for all transverse modes.In addition, multiplexer 130 has low-level relatively WDM crosstalk (that is crosstalking between the multiplexing different optical frequencies of WDM).Back one characteristic can be carried out necessary light filtering (for example referring to Fig. 8) through for example (i) in the single mode territory before the Mode Coupling module; (ii) use Singh's type (sinc) waveform shaping; And/or (iii) use OFDM (OFDM) to realize.

If system 100 uses multi-core fiber in link 120; Then multiplexer 130 can be designed as one group of selected fibre core (can be all fibre cores or its any subset of this multi-core fiber) as single entity, thereby inserts wavelength channel and/or tell this wavelength channel from this whole group fibre core to this whole group fibre core simultaneously.If link 120 has low-level relatively crosstalking between different fibre cores, then multiplexer 130 can be designed as and in each individuals fibre core, inserts signal of communication and/or in each individuals fibre core, tell signal of communication, is regarded as noise/loss with crosstalking between core simultaneously.

In various embodiments, image intensifer 140 can be for concentrating amplifier or distributed amplifier.Usually, system 100 can be designed as unitary (unitary) property that runs through the whole link between two communication nodes 110 and keep the mode mixture matrix.Therefore, image intensifer 140 is designed to present identical substantially gain for all transverse modes of link 120.

In one embodiment, image intensifer 140 is long relatively fiber amplifier (for example being longer than about 100m), and it comprises (i) a plurality of active sections, and (ii) is inserted in a plurality of pattern scramblers between the active section.Each active section provides a medium gain (for example, approximately between the 1dB to 5dB).Pattern scrambler (have another name called and be mode mixer) is for introducing the optics of big relatively Mode Coupling between different transverse modes.Ideally, the pattern scrambler generates uniform mode mixture on the statistics at output, and this mode mixture is irrelevant in the mode profile that input end receives with the pattern scrambler substantially.Those skilled in the art will recognize, the combination of the medium gain of each active section and frequent relatively pattern scrambling have guaranteed to be applied to the identical substantially amplification quantity of all transverse mode experience of amplifier 140.

In one embodiment, optical cross-connect 150 is reconfigurable, to support the expectation route of the light signal between the different nodes 110.As stated, for each multiplexing separate modulation component of the TMM that correctly decodes, it is multiplexing that node 110 generally needs to receive whole TMM.Correspondingly, cross-connect 150 is designed to when carrying out its WDM routing function, and TMM that will be corresponding with each wavelength is multiplexing to do as a whole working.One of skill in the art will appreciate that usually cross-connect 150 can be realized with multiplexer 130 identical assemblies by a plurality of.

Exemplarily, system 100 shown in Figure 1 comprises four nodes 110, optical add/drop multiplexer 130, an image intensifer 140 and an optical cross-connect 150.What it will be appreciated by one of skill in the art that is that in other embodiments, system 100 can comprise node 110, optical add/drop multiplexer 130, image intensifer 140 and/or the optical cross-connect 150 of varying number.Those skilled in the art will understand further that usually, these elements can be to be provided with different mode shown in Figure 1 or to interconnect.

Optical fiber

Fig. 2 A-Fig. 2 H shows (not in scale) sectional view according to the optical fiber that can in system 100, use of various embodiments of the invention.More specifically, the various optical fiber shown in Fig. 2 A-Fig. 2 H can 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 monomode fiber 210.Optical fiber 210 comprises covering 212 and fibre core 216.The diameter of fibre core 216 is less relatively, and it makes the single transverse mode of each wavelength in the wave-length coverage of using in optical fiber 210 back-up systems 100.

Fig. 2 B shows the sectional view of multimode fiber 220.Optical fiber 220 comprises covering 222 and fibre core 226.The diameter that the difference of optical fiber 220 and optical fiber 210 is fibre core 226 is greater than fibre core 216.In various embodiments, the diameter of fibre core 226 is chosen as and makes optical fiber 220 can support from the transverse mode of 2 desired amts selected to about 100 the scope.

Fig. 2 C shows the sectional view of multimode fiber 230.Optical fiber 230 comprises covering 232 and fibre core 236.The diameter of fibre core 236 is also bigger than fibre core 226, and it makes optical fiber 230 can support more than about 100 kinds of transverse modes.

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 further has a plurality of fibre cores 246 that are enclosed in 244 li of inner claddings.The diameter of each fibre core 246 may be selected to be and makes fibre core can support single transverse mode or a plurality of transverse mode.

In one embodiment, optical fiber 240 is designed in image intensifer 140, use.More specifically, inner cladding 244 and/or fibre core 246 have doping (for example erbium ion) so that the photolytic activity medium to be provided.The optical pumping of amplifier 140 (clearly not illustrating among Fig. 1) injects the optical pumping ripple in inner cladding 244, because the refractive index of inner cladding and surrounding layer 242 is different, it can guide the longitudinal axis of this optical pumping ripple along optical fiber 240.The optical pumping ripple that is directed is coupled to each fibre core 246 from inner cladding 244, thereby for by the amplification of the light signal that fibre core guided energy source being provided.The diameter of inner cladding 244 makes this covering use as the multimode fibre core that is used for the optical pumping ripple, and it guarantees that the pump energy distributes along fibre core 246 substantially equably.

Fig. 2 E shows the sectional view of multi-core fiber 250.Optical fiber 250 comprises covering 252 and a plurality of fibre cores 256.Fibre core 256 is distributed in the covering 252, has big relatively interval between the fibre core thereby make.Because this big relatively interval, amount of crosstalk is less relatively between the core in the optical fiber 250, its make individual fibre core 256 can as be used for communicate optical signal separately with pipeline independently.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 a plurality of fibre cores 266.Fibre core 266 is distributed in the covering 262, thereby makes the interval between fibre core: (i) enough little, and with the linearity coupling of amount between fibre core, producing, and (ii) enough big again, between fibre core, to produce non-linear coupling relatively in a small amount.If each fibre core 266 is supported corresponding single transverse mode, then these characteristics of optical fiber 260 can be used to this optical fiber integrally and create the definition clear-cut of relatively small amount and the transverse mode of apart.

Fig. 2 G shows the sectional view of multi-core fiber 270.Optical fiber 270 comprises a plurality of fibre cores 276 of covering 272, first quantity and a plurality of fibre cores 278 of second quantity.The diameter of fibre core 276 is less than fibre core 278.The spacing of using in spacing between the various fibre cores in the optical fiber 270 and the optical fiber 260 (Fig. 2 F) is similar.

A reason that comprises two kinds of different fibre core types in the optical fiber 270 is two types the transverse mode that is characterized by different propagation constants in order to produce.Not matching of propagation constant causes group velocity difference, and usually, it helps reducing the adverse effect of nonlinear fiber.For example, when channel has big relatively group velocity and do not match, can weaken the adverse effect of cross-phase modulation significantly to signal from different WDM channels.In one embodiment,

fibre core

276 and 278 is distributed in the whole covering 272, with the maximum space between the fibre core of realizing same type at interval.

Fig. 2 H shows the sectional view of multi-core fiber 280.Optical fiber 280 comprises a plurality of fibre cores 286 of covering 282, first quantity and a plurality of fibre cores 288 of second quantity.Although fibre core 286 is identical with 288 diameter, they are processed by the material with different refractivity.The difference of refractive index causes

fibre core

286 and 288 to have different propagation constants, its make optical fiber 280 can through with optical fiber 270 (Fig. 2 G) in acting mechanism in nature similar mechanism reduce the adverse effect of nonlinear fiber.

It will be appreciated by those skilled in the art that the optical fiber of other types also is feasible except the optical fiber shown in Fig. 2 A-Fig. 2 H.For example, can make the multi-core fiber that fibre core with two kinds or more kinds of different sizes and fibre core are processed by two kinds or more kinds of different materials, to realize the characteristic shown in Fig. 2 G and Fig. 2 H.

As as used herein, term " multi-channel optical fibre " had both comprised multimode fiber (the for example optical fiber 220 and 230 among Fig. 2 B-Fig. 2 C), comprised multi-core fiber (the for example optical fiber 240-280 among Fig. 2 D-Fig. 2 H) again.

Optical transmitting set

Fig. 3 A-Fig. 3 B illustrates the optical transmitting set 300 that can in node 110 (Fig. 1), use according to an embodiment of the invention.More specifically, Fig. 3 A shows the block diagram of reflector 300.Fig. 3 B illustrates the operation of optical mode coupling (OMC) module 340 of using in the reflector 300 through chart.

The exemplary reflector 300 that is coupled to communication link 120 through output optical fibre 350 that shows of Fig. 3 A.Usually, optical fiber 350 is identical with the fiber type that uses at communication link 120 direct adjacent segment places.As stated, communication link 120 can use the optical fiber of any suitable type of those optical fiber as shown in Figure 2 to realize.Below be described as exemplary and be similar to the embodiment of optical fiber 220 (referring to Fig. 2 B) corresponding to output optical fibre 350.Describe based on this, it will be appreciated by those skilled in the art that how to design other embodiment of reflector 300 that are suitable for communicate optical signal is coupled to the optical fiber of other types.

Reflector 300 comprises laser 310, and its configuration is used to generate the output beam of specified wavelength.Beam splitter 320 will be the N road by the beam separation that laser 310 generates, and with a consequent N light beam coupling to N monomode fiber 322, wherein, N is the integer greater than.Each optical fiber 322 to corresponding optical modulator 330, in this optical modulator 330, utilizes the data that are supplied to this modulator that this light beam is modulated via control signal 328 its beam direction separately.It should be noted that different modulators 330 or the modulator that is fit to are arranged can use from the different independence or the relevant data flow of control signal 328 and modulated its light beam separately.In a representative configurations, each modulator 330 is based on modulating its light beam from the independent data stream that reflector 300 transfers to the correspondence of far-end receiver.The modulated optical signal that is 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 alternative, laser 310 can couple directly to modulator 330, perhaps not through optical fiber but be coupled to this modulator through free space.

A function of OMC module 340 is that N the modulated light signal that receives through N monomode fiber 332 correctly is coupled in the optical fiber 350.More specifically, each is coupled in the single selected transverse mode of optical fiber 350 by the modulated optical signal that OMC module 340 receives substantially, and wherein different modulated optical signals is coupled in the different transverse modes.As as used herein, " signal is coupled to single transverse mode substantially " has two kinds of possibilities but not mutually exclusive implication.According to first kind of implication, its about at least 50% (maybe greater than about 80% or 90%) who is meant this signal integral energy is coupled in the selected transverse mode.According to second kind of implication; It is meant for being coupled to that part of in the multimode fiber in the signal integral energy; At least about 50% (maybe greater than about 80% or 90%) of this part be coupled in the selected transverse mode, and the remainder of this part is coupled in other transverse modes.Most proximal end place at optical fiber is coupled in the single transverse mode of multimode fiber (for example optical fiber 350) by (for example the OMC module 340) substantially when body light signal one by one; Therefore and when changing the light component of the TMM signal that is emitted in this multimode fiber into, it is said the light component " at the most proximal end place of this multimode fiber corresponding to the single transverse mode of this multimode fiber " of this TMM signal.

In an embodiment of reflector 300, quantity N is chosen as the total identical of the transverse mode supported with optical fiber 350.In other words, the OMC module 340 used of this embodiment of reflector 300 can be filled to the light signal of corresponding separate modulation in each and each transverse mode of multimode fiber 350.

Fig. 3 B has graphically described the beam shaping by 340 execution of OMC module.More specifically, the zones of different among Fig. 3 B shows can be by various phase place/field intensities (PFS) pattern of OMC module 340 in the generation of end 348 places of optical fiber 350, and wherein different zones is corresponding to the different optical channel of OMC module.Each PFS pattern uses color graphics to represent that wherein: (i) saturation of color is represented distribution of light intensity in Fig. 3 B, and the (ii) phase place of this light field of color expression itself.For example, the light red distribution of light intensity more corresponding than peony is low.Color changes the expression phase place to red rainbow shape the phase place to+π changes continuously from-π from blue.

For each optical channel of OMC module 340, give the PFS pattern match of the transverse mode of this channel substantially with appointment at the PFS pattern of end 348 places of optical fiber 350 generation by this channel.The Mode Coupling loss that it will be appreciated by those skilled in the art that above indication possibly be by not matching between these PFS patterns cause.Can be corresponding to the light energy of Mode Coupling loss by in other transverse modes of parasitic couplings to optical fiber 350, and/or fully by this optical fiber rejection.

As as used herein, term " coupling substantially " is meant by the PFS pattern of optical channel generation and less relatively corresponding to the difference between the PFS pattern of transverse mode, and satisfies at least one in two possible but not mutually exclusive standards.According to first kind of standard, this difference is enough little so that the gross energy of the PFS pattern that generates by this optical channel (maybe greater than about 80% or 90%) be coupled in the corresponding transverse mode at least about 50%.According to second kind of standard; This difference is enough little; So that be coupled to that part of in the multimode fiber in the gross energy for the PFS pattern that generates by optical channel; This part (maybe greater than about 80% or 90%) gets in the corresponding transverse mode at least about 50%, and the remainder of this part gets in other transverse modes.

Different transverse modes corresponding to the different PFS patterns of Fig. 3 B use following mark to come mark.Character " LP " expression " linear polarization "." LP " numeral thereafter provides two quantization parameter values according to indicated order in the mark.For each transverse mode; First quantization parameter provided about each azimuth rotation of fiber axis be the quantity of the phase increment of unit-sized with 2 π, it is the quantity of the phase increment of unit-sized that second quantization parameter provided on fiber radius with π.For example, the transverse mode that is expressed as LP01 has (i) zero azimuth phase increment, and (ii) radius phase increment.Similarly, the transverse mode that is expressed as LP32 has (i) three azimuth phase increments, and (ii) two radius phase increments.

If OMC module 340 comprises eight optical channels, then can use following representative mode 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; Under the situation that does not deviate from scope of the present invention and principle; Can use other mode assignments similarly; According to these mode assignments, each optical channel of OMC module 340 configuration is used to produce the PFS pattern that the PFS pattern with the transverse mode of the optical fiber 350 of being assigned matees substantially.

It will be appreciated by those skilled in the art that Fig. 3 B corresponding to a possible transverse mode basic set, and other each comprises that the basis set of the transverse mode of a plurality of mutually orthogonals can be used to realize OMC module 340 similarly.

Fig. 4 A-Fig. 4 B illustrates according to an embodiment of the invention can be as the OMC module 400 of OMC module 340 (Fig. 3).More specifically, Fig. 4 A shows the block diagram of OMC module 400.Fig. 4 B shows the phase mask 420 that can in OMC module 400, use.

OMC module 400 comprises two optical channels, and as directed two input optical fibres 332 (also can referring to Fig. 3 A) that itself are coupled to.It will be appreciated by those skilled in the art that OMC module 400 simply mode be revised as and comprise three or more a plurality of optical channel.More specifically, new optical channel can be created with the channel 2 similar optical elements that are used to form in the OMC module 400 through increasing by one group.

OMC module 400 comprises two lasers 410, and 410 pairs in each laser is collimated in the corresponding divergent beams of OMC module by a corresponding fiber optic applications in the optical fiber 332.Each collimated light beam that therefore produces passes in the phase mask 420 corresponding one, and is corresponding to phase filtering light beam 422 to produce.Then, a plurality of minute surfaces 430 spaces superpose these two through phase filtering light beam 422, and " stack " light beam 432 that will therefore produce guides towards optical fiber 350.It should be noted minute surface 430 ₄Be the minute surface of partially transparent, and minute surface 430 ₁-430 ₃It is common opaque minute surface.Two

lasers

442 and 446 and aperture 444 be used for compression (promptly reducing size) union space filtering light beam 432, incide output beam 452 on the end 348 of optical fiber 350 and the expection stack that produces the PFS pattern shown in Fig. 3 B with generation.

Depend on the transverse mode of assigning two optical channels giving OMC module 400, for example in the phase mask kind shown in Fig. 4 B, suitably select phase mask 420 ₁With 420 ₂For example, if the specific light channel of OMC module 400 has been assigned the LP11 pattern of optical fiber 350, the phase mask that then is labeled as LP11 among Fig. 4 B is 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, the phase mask that then is labeled as LP21 among Fig. 4 B is used as the phase mask 420 in this optical channel, or the like.The combined effect of phase filtering that is applied by phase mask 420 and the space filtering that applied by aperture 444 is; This optical channel has generated one that expects in the PFS pattern shown in Fig. 3 B at the end 348 of optical fiber 350, thus light signal is coupled in the corresponding transverse mode of this optical fiber from this optical channel effectively.

It should be noted that some phase masks shown in Fig. 4 B are bifurcation phase mask (promptly only can local apply the phase mask of in two possible phase shifts (for example 0 or π)).Especially, the phase mask corresponding to LP01, LP02 and LP03 pattern is the 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 phase shift range.The analogue phase mask uses color graphics to represent in Fig. 4 B, and wherein: (i) various colors is illustrated in the different phase shifts in the continuous 2 π interval, and (ii) the different bandwidth of same color can be represented with the integral multiple of 2 π the phase shift of differentiation each other.

In one embodiment, OMC module 400 can use single big relatively continuous phase mask to replace the phase mask 420 of two separation ₁With 420 ₂After this this big relatively continuous phase mask is called " multisection type phase mask ", and it can comprise the phase mask among two or more Fig. 4 B in different sections (part).These sections of multisection type phase mask are arranged such that a section is as phase mask 420 ₁, another section is 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 with OMC module 400 (Fig. 4), and uses a lot of components identical, and for example 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 the

OMC module

400 and 500 is that latter's usage space optical modulator (SLM) 520 replaces phase mask 420.In one embodiment, SLM 520 is liquid crystal on silicon (LCOS) SLM.The representative LCOS SLM that can be used as SLM 520 is at for example " Polarization Engineering for LCD Projection (the polarization engineering that is used for the LCD projection) "; In the Chapter 11 257-275 pages or leaves in 2005 author M.G.Robinson, J.Chen are described; G.D.Sharp; Wiley, Chichester (Britain), its instruction is by reference and integral body is herein incorporated.Can be suitable for LCOS SLM as SLM 520 also at for example United States Patent(USP) No. 7,268,852, No.6, open in 940,577 and No.6,797,983, it all by reference and integral body is herein incorporated.The LCOSSLM that is fit to that can be used as SLM 520 is by the JVC manufactured, and it is sold as the parts of JVC projector model DLA-HD2K.

SLM 520 comprises two zones 524 ₁With 524 ₂, the phase filtering that the channel 1 that its configuration is used for carrying out respectively OMC module 500 and channel 2 are required.More specifically, zone 524 ₁Configuration is used for showing that generation is similar to phase mask 420 ₁The spatial modulation pattern of the phase filtering of (seeing Fig. 4 A).Similarly, zone 524 ₂Configuration is used for showing that generation is similar to phase mask 420 ₂The spatial modulation pattern of the phase filtering of (also seeing Fig. 4 A).

Because SLM 520 be reconfigurable device, it can be used for dynamically changing or adjustment is presented at its zones of different, for example regional 524 ₁With 524 ₂In pattern.This characteristic possibly be useful; For example make it possible to relatively easily change transverse mode distribution to the different optical channels of OMC module 500; And/or changing under the situation of features relevant generation to the operating condition of change that possibly cause multimode fiber 350 the optimal light coupling that keeps the different optical channels of OMC module.

OMC module 500 is used two polarization beam splitters 528, suitably will guiding towards SLM 520 by the collimated light beam that lens 410 produce, and will by SLM produces through the light beam guide of phase filtering towards minute surface 430.In one embodiment; Quarter-wave plate (obviously not illustrating among Fig. 5) can be inserted between polarization beam splitter 528 and the SLM 500; Suitably to rotate the polarization of transmission through the light beam of this wave plate; Thereby make polarization beam splitter can collimated light beam be guided towards SLM, and will guide towards minute surface 430 through the light beam of phase filtering.In alternative, SLM 500 can be designed to polarization of reflected light is rotated into and make polarization beam splitter 528 can make identical beam course.

In one embodiment, can be used to produce also be the TMM signal of palarization multiplexing to OMC module 500.Especially, if SLM 520 itself substantially to polarization insensitive, then identical SLM can be used to handle the polarization mode 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) are similar.But OMC module 600 is that with the difference of

OMC module

400 and 500 it uses volume hologram 620, and volume hologram generally is regarded as the three dimensional Phase mask.It should be noted, compare that phase mask 420 generally can be regarded as film or two-dimensional phase mask with SLM 520 with volume hologram 620.

In OMC module 600, volume hologram 620 is carried out at least two different functions.First function in these functions is the phase filtering function of the SLM 520 in phase mask 420 and the OMC module 500 that is similar in the OMC module 400.Second function in these functions is the light beam combination function that is similar to minute surface 430.Because the different sub volume of this volume hologram of corresponding light beam traversal, so volume hologram 620 can be with essential out of phase filtering application in the different light signals that receive from optical fiber 332.Same because of this reason, volume hologram 620 can change the direction of propagation of different light signals with different amounts.Volume hologram is a known systems, and it is in more detail at United States Patent(USP) No. 7,416, describes in 818, No.7,323,275 and No.6,909,528, and it all by reference and integral body is herein incorporated.

OMC module 600 exemplary being depicted as have three optical channels.Skilled person will appreciate that OMC module 600 can be revised as the optical channel with varying number with simple mode.

Fig. 7 shows the block diagram of the optical transmitting set 700 that can in node 110 (Fig. 1), use according to another embodiment of the present invention.(Fig. 3) is similar with reflector 300, and reflector 700 can be optionally be coupled to the light signal of separate modulation in the respective transversal pattern of output optical fibre (being optical fiber 750).But additionally, reflector 700 passes through in the modulation of this reflector and palarization multiplexing (MPM) module 712, to use polarization beam splitter 714 and polarization combiner 734, and has palarization multiplexing (PM) ability.Reflector 700 exemplary each polarization that are depicted as have three optical channels.It will be appreciated by those skilled in the art that reflector 700 can be revised as the channel that each polarization has varying number (for example two or more than three) with simple mode.

Reflector 700 comprises laser 710, and its configuration is used to generate the output beam of specified wavelength.Laser 710 is presented to MPM module 712, and wherein polarization beam splitter 714 becomes the beam separation of this laser generation the light beam 716 of mutually orthogonal polarization ₁With 716 ₂ MPM module 712 further has two power splitters 720, and the corresponding light beam that each power splitter will be received from polarization beam splitter 714 is separated into three the tunnel, and in three light beam coupling to three monomode fibers 722 that will obtain thus.Each optical fiber 722 is directed to corresponding optical modulator 730 with its light beam separately, in this optical modulator, utilizes the data that offer this modulator that this light beam is modulated via control signal 728.The modulated optical signal that modulator 730 produces is coupled in the monomode fiber 732, and is directed to corresponding polarization combiner 734.Each polarization combiner 734 is incorporated into the orthogonal polarization signals of two receptions in the corresponding PM signal, and the monomode fiber 736 through separately is directed to OMC module 740 with the PM signal then.

In alternative, reflector 700 can use the direct sunshine coupling or replace the optical fiber coupling of at least a portion shown in Figure 7 perhaps it to be replenished through the free space optical coupling.

Usually, the OMC module 740 of reflector 700 is similar with the OMC module 340 (Fig. 3) of reflector 300, and it is used for the PM signal of three receptions is coupled to optical fiber 750 rightly.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 are coupled in the different transverse modes.For individual PM signal (it has two orthogonal polarization components), each in its polarized component is the identical substantially phase filtering of experience in OMC module 740 all.In various embodiments, OMC module 740 can (be seen Fig. 4-Fig. 6) realization similarly with OMC module 400,500 and 600.But, when design OMC module 740, should pay special attention to the characteristic of its polarization manipulation, so that said OMC module can be substantially to polarization insensitive.

Fig. 8 shows the block diagram according to the optical transmitting set 800 that can in node 110 (Fig. 1), use of further embodiment of this invention.Similar with in the reflector 300 and 700 (seeing Fig. 3 and Fig. 7) each, reflector 800 can optionally be coupled to communicate optical signal in the various transverse modes of output optical fibre (being optical fiber 850).Similar with reflector 700, reflector 800 has the palarization multiplexing ability through using three MPM modules 812, and each MPM module 812 is similar with MPM module 712 (see figure 7)s.But additionally, reflector 800 has the WDM ability.Therefore reflector 800 use three dissimilar multiplexing: transverse mode multiplexing (TMM), palarization multiplexing (PM) and wavelength division multiplexing (WDM).

Reflector 800 has three TMM channels, three WDM channels and two PM channels, and it makes reflector to generate to have the TMM signal up to 18 separate modulation communicate optical signals (each is excited transverse mode up to six).It will be appreciated by those skilled in the art that reflector 800 can be revised as the separate modulation component that can generate varying number with simple relatively mode, and it is coupled in the selected transverse mode of optical fiber 850 with the mode of any desired.

Each WDM channel of reflector 800 has laser 810 separately, and it generates the wavelength of appointment and is applied to MPM module 812 separately.Three outputs of MPM module 812 are applied to optical filter (OF) 818, and it carries out bandpass filtering relatively closely, to reduce corresponding to crosstalking between the light signal of different WDM channels.It is multiplexing in multiplexer 826, to carry out WDM through filtering signal, and consequent WDM signal is directed to OMC module 840 through single mode or integrated optical fiber 836.

Usually, the OMC module 840 of reflector 800 is similar with the OMC module 340 (Fig. 3) of reflector 300, and it is used for the WDM signal of three receptions is coupled to optical fiber 850 rightly.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 signals are coupled in the different transverse modes.Although the PFS pattern corresponding to the transverse mode of multimode fiber depends on wavelength, the typical light bands of a spectrum relative narrower of in wdm system, using, this makes it possible to use identical phase mask to all WDM channels in reality.For example, be that center, overall width are about the variance that the band of 100nm uploads on the wave frequency at the integral light bands of a spectrum and only have an appointment 6% with about 1550nm.Because this relatively little variance, will enough be competent at all wavelengths in these bands of a spectrum to the phase mask that is arranged near the wavelength design of this band middle.Therefore, in various embodiments, OMC module 840 can (be seen Fig. 4-Fig. 6) realization similarly with OMC module 400,500 and 600.

Optical receiver

As be known in the art, the transverse mode of multi-channel optical fibre stands intermode at it when this length of fiber direction is propagated mixes.Usually, the influence of intermode mixing is stronger in multimode fiber.But the multi-core fiber with compact arranged relatively fibre core also possibly exist strong relatively intermode to mix (for example, crosstalking between core).Therefore, even signal of communication is coupled in the specific single transverse mode at the front end of multi-channel optical fibre, at the far-end of this optical fiber, other transverse modes also will have the contribution from this signal of communication.Therefore, need carry out quite a large amount of signal processing, the data of carrying by the different separate modulation components of TMM signal with abundant recovery at receiver.Usually, for N separate modulation component of the TMM signal of decoding, receiver need obtain the independent sample of N at least of this signal.Usually, the signal processing that is applied to these samples is based on the diagonalization of matrix algorithm, and target is to reverse the influence that the intermode in this multi-channel optical fibre mixes.

Fig. 9 shows the block diagram of the optical receiver 900 that can in node 110 (Fig. 1), use according to an embodiment of the invention.Receiver 900 can dispose and be used for for example receiving input TMM signal 902 from link 120.TMM signal 902 is applied to K the sample 912 of tap module 910 to produce this TMM signal, and wherein K is the positive integer greater than.Each sample 912 carries out coherent detection by coherent detector 930, the use of correspondence by the LO signal 922 of local oscillator (LO) source 920 supplies.By the testing result that coherent detector 930 generates from sample 912, for example the in-phase component I of sample and quadrature component Q are applied to digital signal processor (DSP) 940.For each signal transmission intercal (for example bit period), DSP 940 suitably handles by coherent detector 930 ₁-930 _KA whole group testing result that generates is to generate output stream 942.If tap module 910 produces the sample of enough TMM signals 902, then DSP 940 can recover and export initial all data by far-end transmitter codes to TMM signal through stream 942, and wherein this TMM signal is received by receiver 900 as TMM signal 902.

A function that it will be appreciated by those skilled in the art that DSP 940 is that the mode mixture matrix corresponding to link 120 is reversed.Usually, link condition changes in time, therefore causes the mode mixture matrix also to change, usually in millisecond magnitude or slower.In one embodiment, DSP 940 configurations are used for following adaptively the link condition change.For example, as be known in the art, DSP 940 can use the blind adaptive algorithm to learn link condition and adapt to this link condition.Alternatively or additionally, the controller 950 that is coupled to DSP 940 possibly require the far-end reflector to send training sequences to receiver 900 again and again, obtains the present mode hybrid matrix for DSP.Can have the TMM signal by the far-end transmitters applications in the representative training sequence of link 120, wherein, make and having only a transverse mode to be energized preset time arbitrarily by the different transverse mode of known order excitation.The signal processing that in DSP940, realizes also possibly compensate some non-linear interference, the phase shift of for example being introduced by self pattern and cross-mode nonlinear fiber.

Figure 10 A-Figure 10 B shows the typical module that can in receiver 900 (Fig. 9), use according to an embodiment of the invention.More specifically, Figure 10 A shows the block diagram of the tap module 1010 that can be used as tap module 910 uses.Figure 10 B shows the block diagram of the coherent detector 1030 that can be used as coherent detector 930 uses.

With reference to Figure 10 A, tap module 1010 receives TMM signal 902 through multimode fiber 1002.The divergent beams that 1004 pairs of optical fiber of collimating lens 1002 produce collimate, and consequent collimated light beam is guided towards K-1 partially transparent minute surface 1006 ₁-1006 _K-1 Nontransparent minute surface 1006 with end _KIn a realization, the reflectivity of different minute surfaces 1006 causes the light beam 1012 from this direct reflection ₁-1012 _KHas approximately uniform intensity.

With reference to Figure 10 B, the LO signal 922 that detector 1030 receives from LO source 920 through monomode fiber 1016.The divergent beams that 1018 pairs of optical fiber of collimating lens 1016 produce collimate, and consequent collimated light beam is guided towards phase mask 1020.Usually, phase mask 1020 is similar with phase mask 420 (seeing 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 corresponding to the PFS pattern of the selected transverse mode of multimode fiber 1002 (Figure 10 A).As stated, Fig. 4 B shows the kind of phase mask, and wherein each all is suitable for using as phase mask 1020.When each detector 930 in the receiver 900 used detector 1030 to realize, the different instances of the detector 1030 in the receiver had different phase mask 1020 (the out of phase mask of for example from kind shown in Fig. 4 B, selecting) 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 of the SLM that is similar to SLM 520 (Fig. 5) to implement.

Be applied to the optical mixer 1026 of 2x4 through light beam of phase filtering 1022 and light beam 1012 (it carries TMM sample 922, sees Fig. 9 and Figure 10 A), both therein mutually impacts to produce four interference signals 1032 ₁-1032 ₄Each interference signal 1032 ₁-1032 ₄Be applied to corresponding photodetector (for example photodiode) 1034, to be converted into the corresponding signal of telecommunication.The signal of telecommunication that is generated by photodetector 1034 is digitized and is directed to the further processing among the DSP940.The optical mixer that can be used as the 2x4 of blender 1026 uses in the detector 1030 is known in the prior art; Its representative example is for example being submitted on December 18th, 2008: (i) the open No.2007/0297806 of U.S. Patent application and (ii) U.S. Patent application No.12/338; Open in 492, both by reference whole and integral body is herein incorporated.

Interference signal 1032 ₁-1032 ₄Electric field E ₁-E ₄Provide through formula (1) respectively:

[\begin{matrix} E_{1} \\ E_{2} \\ E_{3} \\ E_{4} \end{matrix}] = \frac{1}{2} [\begin{matrix} 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} \end{matrix}] - - - (1)

Wherein, E _SAnd E _LOBe respectively the electric field of light signal 1012 and 1022.It should be noted that formula (1) is applicable to each point of the lateral cross section of light beam 1032.This means detector 1030 not only measuring

beam

1012 and 1022 how impact mutually in time, also detect them and spatially how to impact mutually.Further, because the mutually orthogonal property of the different transverse modes of optical fiber 1016, the different instances with detector 1030 of out of phase mask 1020 is measured the electric field corresponding to the different transverse modes of TMM signal 902 effectively.Skilled person will appreciate that; If K >=N; Then coherent detector 930 (perhaps 1030) generates enough sample datas; So that DSP 940 can reverse the mode mixture matrix corresponding to communication link 120 rightly, and recover by the entrained data of the separate modulation component of TMM signal, wherein this TMM signal is emitted to receiver 900 from far-end reflector (for example reflector 300) through communication link 120.

Figure 11 shows according to another embodiment of the present invention the block diagram of the tap module 1110 that can use as tap module 910.Tap module 1110 comprises multimode fiber 1102, receives TMM signal 902 through this multimode fiber 1102.Along the length direction of optical fiber 1102, tap module 1110 has K multimode fiber (MMF) coupler 1106 ₁-1106 _KWith K-1 pattern scrambler 1108 ₂-1108 _KEach MMF coupler 1106 is a fiber optic tap, and it is shunted a part of TMM signal 902, and this part is coupled in the corresponding monomode fiber 1110.By optical fiber 1110 ₁-1110 _KThe signal 1112 that carries ₁-1112 _KRespectively as the sample in the receiver 900 912 ₁-912 _K

The linear combination of the transverse mode that each signal 1112 indication exists in the multimode fiber 1102 of the position of the MMF of correspondence coupler 1106.Because pattern scrambler 1108 ₂-1108 _KWith MMF coupler 1106 ₁-1106 _KBetween transverse mode mix so each signal 1112 ₁-1112 _KThe different linear combinations of the transverse mode in the indication multimode fiber 1102.Skilled person will appreciate that; If K >=N; Then coherent detector 930 generates enough sample datas; So that DSP 940 can reverse the mode mixture matrix corresponding to communication link 120 rightly, and recover the data that the separate modulation component by the TMM signal carries, wherein this TMM signal is emitted to receiver 900 from far-end reflector (for example reflector 300) through communication link 120.

In one embodiment, receiver 900 comprises tap module 1110, and it can be used as coherent detector 930 and uses, and wherein coherent detector is designed for and detects the PM signal.It is known in the prior art and be disclosed in open No.2007/0297806 of for example above-mentioned U.S. Patent application and U.S. Patent application No.12/338 to be used to detect the coherent detector of PM signal, in 492.It will be appreciated by those skilled in the art that and use tap module 1110 and a plurality of receivers 900 that are used to detect the coherent detector of PM signal can suitably detect the light signal that utilizes TMM and the multiplexing generation of PM.What those skilled in the art will be further understood that is, can suitably detect the WDM receiver that uses the light signal that above-mentioned whole three kinds of multiplexing types (being TMM, PM and WDM) produce can constitute through disposing the receiver 900 that each WDM channel to the WDM receiver all has TMM and PM function.

Figure 12 shows the block diagram of the optical receiver 1200 that can in node 110 (Fig. 1), use according to another embodiment of the present invention.Receiver 1200 receives TMM signal (for example from link 120) through multimode fiber 1202.Collimating lens 1204 ₁The divergent beams that optical fiber 1202 is produced collimate, and consequent collimated light beam 1205 is guided towards beam splitter 1206 ₁-1206 ₄In one embodiment, each beam splitter 1206 is translucent minute surface.

Receiver 1200 also comprises collimating lens 1204 is passed in its output 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 ₄Be positioned at beam splitter 1206 ₁With 1206 ₂Between 90 ° of phase shifters 1,208 90 ° phase shift is introduced in the light beam via its transmission.

Beam splitter 1206 ₁-1206 ₄Suitably

light beam

1205 and 1221 is separated into a plurality of beamlets, and then the part in these beamlets of recombinating to be to generate four mixed light beams, it is incident on four array detectors (for example CCD) 1230 ₁-1230 ₄The pixelation receiving surface on, wherein mixed light beam produces corresponding interference figure at this place.Each array detector 1230 turns round with sufficiently high speed, so that it can catch and export the data of at least one interference figure of signal transmission intercal (for example symbol period) corresponding to each TMM signal 1201.Each interference figure is at the pixelation receiving surface place of array detector 1230, generate through clashing into the reference field that generated by LO source 1220 and the light field of TMM signal 1201 each other.Array detector 1230 is caught interference figure through the light intensity of the measured pattern at a plurality of pixels place of this array detector, thereby generates the two-dimensional section intensity corrugated (profile) of mixed light beam.

Corresponding to by array detector 1230 ₁-1230 ₄The data of detected four interference figures are provided for DSP 1240 and handle.If array detector 1230 ₁-1230 ₄Have sufficiently high resolution (for example enough a large amount of relatively little pixels), then DSP 1240 receives enough data from four interference figures, forms with the pattern of confirming TMM signal 1201.At this, term " pattern composition " is meant the form of expression of TMM signal 1201 with the transverse mode of multimode fiber 1202.Typically, this linear combination that takes the form of the transverse mode of suitable weighting.Then; The knowledge that relevant pattern is formed makes DSP can reverse the mode mixture matrix corresponding to communication link 120 rightly; And recover the data that the separate modulation component by the TMM signal carries, wherein this TMM signal is emitted to receiver 1200 from far-end reflector (for example reflector 300) through communication link 120.The data that DSP 1240 is resumed through data flow 1242 outputs.

It will be understood by those of skill in the art that array detector 1230 ₂With 1230 ₄Be selectable, it is used in realizes being similar to the balance detection scheme that realizes in the detector 1030 in the receiver 1200.More specifically, by array detector 1230 ₁-1230 ₄Detected four interference figures are handled by DSP 1240, to generate two sectional views of TMM signal 1201.First sectional view is the same phasor of TMM signal 1201, and second sectional view is the orthogonal graph of TMM signal 1201.Same phasor and orthogonal graph with TMM signal 1201 possibly be favourable, because DSP 1240 can use these to scheme to come sooner, more accurately and/or more effectively confirm the pattern composition of TMM signal.

In various embodiments, receiver 1200 can comprise other optical module, can use the array detector that is less than four separation.For example, in one embodiment, receiver 1200 can have two big relatively array detectors, and wherein: (i) first detector is a subregion, and a part that makes the detector of winning is as array detector 1230 ₁, and another part of first detector is as array detector 1230 ₂, and (ii) similar, second detector is a subregion, makes the part of second detector as array detector 1230 ₃, and another part of second detector is as array detector 1230 ₄In alternative, receiver 1200 can have a very large array detector, and it can be divided into four parts, and each part is as detector 1230 ₁-1230 ₄In corresponding one.

Although the present invention is described in this with reference to illustrated embodiment, this specification is not intended to explain with limiting meaning.Obviously for those skilled in the art in the invention, be that various modifications and other embodiment of the present invention of said embodiment are considered to fall in the expressed the principle and scope of the present invention of accompanying claims.

Only if otherwise describe clearly, otherwise each numerical value and scope should be interpreted as approximation, the numerical value that is positioned at this numerical value or scope as word " approximately " or " approx " before.

What will be further understood that is that under the situation that does not depart from the described scope of the invention of accompanying claims, those skilled in the art can be to describing with details, material and the layout of illustrated parts and carry out various changes in order to explain essence of the present invention.

If any; Although the element in the following claim to a method is put down in writing with specific order with corresponding mark; Be used to implement some of those elements or whole particular order only if the record of claim otherwise hints, otherwise those elements need not limit with this particular order and implement.

Here " embodiment " who mentions or " embodiment " are meant the described special characteristic of this embodiment of combination, structure or characteristic can be included among at least one embodiment of the present invention.The phrase " in one embodiment " that many places occur in specification does not need all to relate to identical embodiment, and independent or interchangeable embodiment does not need mutually exclusive other embodiment yet.More than be equally applicable to term " realization ".

Also be for illustrative purposes; Term " coupling ", " connection " are meant the any-mode that prior art permission energy known or exploitation later on transmits between two or more elements; And it is contemplated that and insert one or more add ons, although this not necessarily.On the contrary, term " directly coupling ", " directly connecting " or the like hint and do not have this add ons.

The present invention possibly implement with other specific equipment and/or method.Said embodiment can think it only is unrestricted for explanation in all respects.Especially, scope of the present invention shows through accompanying claims, but not shows through specification and accompanying drawing here.The all changes of in the implication of equal value of claims and scope, carrying out will be included in its scope.

Specification and accompanying drawing have only illustrated principle of the present invention.Therefore will understand, although do not describe clearly or illustrate at this, those of ordinary skills can design the principle that multiple layout is come embodiment of the present invention, and it is also included within the spirit and scope of the present invention.Further; Mainly be intended to only be used for clearly teaching purpose in these all examples of enumerating; The notion that helps reader understanding's principle of the present invention and proposed by the inventor, with push technological development, it is to be understood that to being not limited to this specific example of enumerating and situation.In addition, this detail principle of the present invention, aspect and the description of embodiment, with and particular example be intended to comprise its replacement of equal value.

Those of ordinary skills should recognize, are the concept map of the exemplary circuit of the expression principle that is used for embodiment of the present invention at this any block diagram.Similarly; To will be appreciated that; Any flow table, flow chart, state transition diagram, false code and similarly represent multiple process, it can be represented by computer-readable medium substantially and carried out by computer or processor, no matter whether this computer or processor illustrate clearly.

Claims

1. optical receiver comprises:

Tap module, its configuration are used for the light transverse mode with N separate modulation component multiplexing (TMM) signal is sampled, and to produce K light sample at each signal transmission intercal, N and K are the positive integer greater than 1, wherein K >=N;

Local oscillator (LO) source, its configuration is used to produce light LO signal;

K coherent detector, each coherent detector are optically coupled to said tap module and said LO source, and configuration is used for:

Corresponding light sample and said LO signal are mixed, to produce one or more optical interference signals; And

Convert said one or more optical interference signals to the in-phase component of this light sample of indication and one or more signals of telecommunication of quadrature component; And

Digital signal processor (DSP); Its operability is coupled to this K coherent detector and configuration is used to handle the signal of telecommunication that is produced by said coherent detector; The data of carrying with each the separate modulation component that recovers by N separate modulation component of this TMM signal, wherein:

Said optical receiver receives said TMM signal through the multimode fiber of supporting multiple transverse mode; And

At the far-end of said multimode fiber, each separate modulation component of said TMM signal is corresponding to the corresponding single transverse mode of said multimode fiber.

2. optical receiver according to claim 1, wherein:

Said TMM signal is experience intermode mixing in said multimode fiber before being received by said optical receiver; And

The influence that said DSP configuration is used for said intermode is mixed reverses to recover said data.

3. optical receiver according to claim 1; Further comprise controller; Its operability is coupled to said DSP; And configuration is used for to the request of sending of far-end reflector, and to send the light training signal to this optical receiver, wherein this DSP configuration is used for deriving the mode mixture matrix corresponding to this multimode fiber based on this training signal.

4. optical receiver comprises:

Tap module; Its configuration is used for the light transverse mode with N separate modulation component multiplexing (TMM) signal is sampled; To produce K light sample at each signal transmission intercal; N and K are the positive integer greater than 1, and wherein K >=N, and this tap module receives this TMM signal through the multimode fiber of supporting multiple transverse mode;

K coherent detector, each coherent detector are optically coupled to this tap module and LO source, and its configuration is used for:

This LO signal is carried out phase filtering, and to produce accordingly through the phase filtering light beam, it has the PFS pattern corresponding to phase place/field intensity (PFS) pattern of the corresponding selected transverse mode of said multimode fiber;

With corresponding light sample and said through the mixing of phase filtering light beam, to generate one or more optical interference signals; And

Digital signal processor (DSP), it operatively is coupled to this K coherent detector, and configuration is used to handle the signal of telecommunication that is produced by said coherent detector, the data of carrying with each the separate modulation component that recovers by N separate modulation component of this TMM signal.

5. optical receiver according to claim 4, at least one in the wherein said K coherent detector comprises:

Phase mask, its configuration are used for this LO signal is carried out phase filtering, to produce accordingly through the phase filtering light beam;

Optical mixer, its configuration are used for mixing through the phase filtering light beam with corresponding to the light beam of corresponding light sample said, to generate these one or more optical interference signals; And

A plurality of photodetectors, it should convert this one or more signals of telecommunication into by one or more optical interference signals.

6. optical receiver comprises:

A plurality of beam splitters, its configuration is used for:

(i) will be a plurality of beamlets of first quantity corresponding to the beam separation of light transverse mode multiplexing (TMM) signal, wherein this TMM signal has a plurality of separate modulation components, and it receives through the multimode fiber of supporting multiple transverse mode;

To corresponding to the beam separation of local oscillator (LO) signal a plurality of beamlets of second quantity (ii); And

(iii) the beamlet of first quantity and the beamlet of second quantity are mixed to generate two or more mixed light beams;

First array detector, its configuration are used to detect first interference figure corresponding to first mixed light beam of these two or more mixed light beams;

Second array detector, its configuration are used to detect second interference figure corresponding to second mixed light beam of these two or more mixed light beams; And

Digital signal processor (DSP); It operatively is coupled to this first and second array detector; And configuration is used to handle this first and second interference figure, forms with the pattern of confirming this TMM signal, and forms based on said pattern and to recover the data that the separate modulation component by this TMM signal carries.

7. optical receiver according to claim 6, wherein:

In this first and second array detector each all disposes each the signal transmission intercal that is used at this TMM signal and obtains once corresponding one of this first and second interference figure at least;

This optical receiver further comprises phase shifter, and it causes having specific phase shift from first beamlet of a plurality of beamlets of this second quantity with respect to second beamlet from a plurality of beamlets of this second quantity, wherein, and these a plurality of beam splitters:

(i) will mix from first beamlet of a plurality of beamlets of this first quantity with from first beamlet of a plurality of beamlets of this second quantity, to generate this first mixed light beam; And

(ii) will mix, to generate this second mixed light beam from second beamlet of a plurality of beamlets of this first quantity with from second beamlet of a plurality of beamlets of this second quantity; And

This specific phase shift is approximate 90 degree.

8. optical receiver according to claim 7, it further comprises:

Tri-array detector, its configuration are used to detect the 3rd interference figure corresponding to the 3rd mixed light beam; And

The 4th array detector, its configuration are used to detect the 4th interference figure corresponding to the 4th mixed light beam, wherein

This phase shifter causes from the 3rd beamlet of a plurality of beamlets of this second quantity with respect to having this specific phase shift from the 4th beamlet of a plurality of beamlets of this second quantity and each of said second beamlet;

These a plurality of beam splitters:

(iii) will mix, to generate the 3rd mixed light beam from the 3rd beamlet of a plurality of beamlets of this first quantity with from the 3rd beamlet of a plurality of beamlets of this second quantity; And

(iv) will mix, to generate the 4th mixed light beam from the 4th beamlet of a plurality of beamlets of this first quantity with from the 4th beamlet of a plurality of beamlets of this second quantity; And

This DSP operatively is coupled to this third and fourth array detector, and configuration is used to handle this third and fourth interference figure, forms with the pattern of confirming this TMM signal.

9. optical receiver according to claim 8, wherein, said array detector and DSP realize the balance detection scheme, wherein:

This first and the 3rd interference figure is processed to generate the same phasor of this TMM signal;

This third and fourth interference figure is processed to generate the orthogonal graph of this TMM signal; And

Said being processed with the pattern of confirming this TMM signal with phasor and orthogonal graph formed.

10. optical receiver comprises:

K coherent detector, each coherent detector are optically coupled to this tap module and LO source, and configuration is used for:

Corresponding light sample and this LO signal are mixed, to produce one or more optical interference signals; And

Digital signal processor (DSP); It operatively is coupled to this K coherent detector; And configuration is used to handle the signal of telecommunication that is produced by said coherent detector, the data of carrying with each the separate modulation component that recovers by N separate modulation component of this TMM signal, wherein:

This optical receiver receives said TMM signal through the multimode fiber of supporting multiple transverse mode; And

This tap module comprises:

K multimode fiber (MMF) coupler, wherein each branches to luminous power the monomode fiber from this multimode fiber, with the light sample of the correspondence that produces this TMM signal; And

K-1 pattern scrambler, each is arranged between the MMF coupler of two vicinities.