CN103973388A - Optical line terminal, ONU, optical communication system and corresponding methods - Google Patents
Optical line terminal, ONU, optical communication system and corresponding methods Download PDFInfo
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- CN103973388A CN103973388A CN201310032607.3A CN201310032607A CN103973388A CN 103973388 A CN103973388 A CN 103973388A CN 201310032607 A CN201310032607 A CN 201310032607A CN 103973388 A CN103973388 A CN 103973388A
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Abstract
The invention provides an optical line terminal, an ONU, an optical communication system and corresponding methods. An adjustable laser device is used in an ONU in an existing TWDM-PON, and cost is high. The optical line terminal comprises a dual-wavelength generator (2), a plurality of downlink modulation modules (7) and a coupler (8), wherein the dual-wavelength generator (2) is used for generating first optical signals corresponding to multiple multiplexed seed optical signals different in wavelength and second optical signals corresponding to the multiple multiplexed seed optical signals different in wavelength, the frequencies of the first optical signals are different from the frequencies of the second optical signals, the first optical signals serve as the first set of optical signals, and the second optical signals serve as the second set of optical signals. The multiple downlink modulation modules (7) correspond to the first optical signals in the first set of optical signals respectively to modulate downlink information onto the first optical signals. The coupler (8) enables the second set of optical signals and the first set of optical signals with modulated downlink information to be coupled together and output. The ONU comprises a downlink receiving module and an uplink modulation module. The downlink receiving module is used for detecting the corresponding first optical signals to obtain the downlink information. The uplink modulation module is used for modulating uplink information onto the corresponding second optical signals and outputting the second optical signals.
Description
Technical field
The present invention relates to optical-fiber network, relate in particular to the wavelength division multiplexed optical network based on EPON.
Background technology
Along with senior multimedia extensive use, for example 3D TV, Telemedicine, game on line, the exploitation of the application such as interdynamic video study, has had huge growth to the demand of bandwidth.PON2 of future generation (NG-PON2) is as the PON solution of Long Term Evolution, just as a focus subject under discussion, discussed by portion of international telecommunication union telecommunication (ITU-T) and FSAN (Full Service Access Network is called for short FSAN) institute.Most operator wishes that NG-PON2 can provide larger bandwidth, higher splitting ratio (split ratio), longer transmission range and better access capability.At present, ITU-T and FSAN are finally determining the demand of NG-PON2, available bandwidth is increased to 40Gb/s speed.
In the technical scheme having proposed, TWDM-PON is the main solution to NG-PON2 by nearest FSAN meeting be considered as, wherein, 4 10G-PON (XG-PON) are stacked on together and have the splitting ratio of 1: 64, and this can obtain the rate of polymerization of down direction 40Gbps and up direction 10GGbps.In single wavelength, TWDM-PON has reused descending multiplexing and up access technology, time slot granularity, multicast capability and the Bandwidth sharing mechanism of XG-PON.
But in TWDM-PON, ONU transmitter must have the ability uplink information to be modulated on any one wavelength in four up wavelength.ONU receiver also must have the ability to detect downlink information from any wavelength to four downstream wavelength.Therefore, design adjustable ONU cheaply and become a crucial technical problem.
At present, wavelength can conditioning technology be existing for realizing the preferred plan of colorless ONU, and wherein, a tunable optical filter is for downstream signal wavelength selectivity, and tunable laser is for upward signal transmitter, as shown in Figure 1.Specifically, at down direction, in optical line terminal OLT, after four downstream wavelength are converged by grating AWG (left part in OLT), exported by circulator.Via Optical Fiber Transmission, to remote node RN, four downstream wavelength that are re-used are divided into n road by the optical splitter in remote node RN, and wherein each road is all with the signal of four downstream wavelength.Optical splitter output Yi road multiplexed signals reaches optical network unit ONU 1, and this optical network unit ONU 1 is corresponding to wavelength X
1.Its AWG and tunable optical filter are by the wavelength X corresponding to this ONU1
1signal from the signal of four multiplexing downstream wavelength, select, and offer receiver Rx and detect.And at up direction, the tunable laser in ONU1 is λ ' by the wavelength of modulated output upward signal
1upward signal.This upward signal is provided to RN by the AWG in ONU.The upward signal of the different wave length that the optical splitter in RN provides each ONU is together multiplexing, sends it back OLT by optical fiber.Circulator in OLT sends upward signal the AWG that is responsible for selecting each up wavelength, and this AWG is by each up wavelength separated and offer respectively corresponding uplink receiver Rx (OLT middle and lower part).
But tunable laser is very expensive equipment.Particularly, in the time that NG-PON2 need to support to be greater than the splitting ratio of 1: 64, need at least 64 ONU users, the total cost of tunable laser will become greatly so increases.Due to the cost costliness of tunable laser, and this expensive increase of linearity along with ONU quantity, limit deployment and the enforcement of TWDM-PON system.Therefore, need in TWDM-PON system, design adjustable ONU cheaply.
Summary of the invention
This solution is paid close attention to the low cost ONU in design TWDM-PON system, and keeps traditional ODN (optical distributed network) simultaneously.Basic conception of the present invention comprises following any in some:
1. the single new dual wavelength maker of Mach-Zehnder (Mach-Zehnder) modulator design driving based on common, for example 4 light sources can produce 8 independently wavelength.
2. use Mach-Zehnder delay interferometer (MZDI) cheaply that 8 wavelength are divided into two parts that quantity is identical, a part is used as seed light and is injected into from outside among common commercial FP-LD to produce for descending light signal, a part is modulated and be directly sent to ONU to as the light carrier of upward signal, modulated by upward signal in addition.
3. remote node has optical splitter, identical with the remote node in traditional ODN framework, makes this invention have compatibility to traditional ODN framework.
4. in ONU, select module to select required wavelength based on single adjustable light, use common optical receiver, and carry out uplink communication with common ROSA, realize adjustable ONU cheaply, and do not need to use tunable laser to provide light signal to carry out upward signal modulation.
According to first basic aspect of the present invention, a kind of optical line terminal is provided, comprise as lower component:
The-the first array waveguide grating, is connected with described dual wavelength maker, for receiving respectively the seed photo-signal of multiple different wave lengths, is converged, and offers described dual wavelength maker;
-dual wavelength maker, for receiving the seed photo-signal of the multiple different wave lengths that are re-used, and respectively for each seed photo-signal, the first light signal that generates the different frequency corresponding with this seed photo-signal as first group of light signal and the second light signal as second group of light signal;
-light separator, for first group of light signal corresponding to each seed photo-signal is separated in together, and is separated in second group of light signal corresponding to each seed photo-signal together;
-optical selector, for selecting respectively each the first light signal from isolated first group of light signal;
-multiple Corticofugal Modulation of Somatosensory modules, correspond respectively to each the first light signal, downlink information is modulated on described the first light signal, and feeds back to described optical selector;
Described optical selector has each first light signal of downlink information to be multiplexed with first group of light signal modulation;
-coupler, for isolated described second group of light signal and described first group of light signal that be re-used, modulated downlink information are coupled, and output.
Correspondingly, second basic aspect according to the present invention, the present invention also provides a kind of optical network unit, comprises as lower component:
-light is selected module, for receiving optical signals, therefrom select corresponding to the first light signal in first group of light signal of the different frequency of same seed photo-signal and the second light signal in second group of light signal, and described the first and second light signals are separated from each other out, wherein, described the first light signal is modulated downlink information;
-descending receiver module, for described the first light signal being separated is detected, obtains described downlink information;
-up modulation module, for uplink information being modulated to described the second light signal being separated, and is reflected back described light by described second light signal of modulated uplink information and selects module with output.
From the angle of system, the invention provides a kind of optical communication system, comprising:
-described according to a first aspect of the invention optical line terminal;
-optical branching device, is connected with described optical line terminal;
-multiple according to the present invention the optical network unit described in second aspect, be connected with described optical branching device respectively;
The downlink optical signal that described optical branching device provides described optical line terminal is along separate routes to each optical network unit.
In aspect more than of the present invention, by producing adjustable up wavelength and offer ONU in OLT, system complexity is transferred in OLT, in ONU, has removed wavelength management, avoid using tunable laser, effectively reduced the cost of ONU.And, correspondingly provide scalability to rolling up of wavelength or ONU,, in the time that needs increase wavelength, improvement OLT can realize the increase of up-downgoing wavelength simultaneously; Thereby in the time that needs increase ONU, can not cause the surge of system cost.
According to one preferred embodiment, described dual wavelength maker comprises input port, the first branch road, the second branch road in parallel, and output port, described input port is divided into described the first branch road and described the second branch road by the seed photo-signal of input by certain splitting ratio, and, be stacked adduction through the signal of described the first branch road and the second branch road and export by described output port
Wherein, described the first branch road comprises a Mach-Zehnder modulator, described Mach-Zehnder modulator receives the bias voltage of radiofrequency signal and certain amplitude of certain frequency, makes this Mach-Zehnder modulator export described seed photo-signal and is the second order sideband signals of this certain frequency of twice with described seed photo-signal frequency interval;
Described the second branch road comprises one section of waveguide, and has a phase-modulator, and described phase-modulator, by the described seed photo-signal regulating on the second branch road, makes phase place reverse;
Described the first branch road and described the second branch road described seed photo-signal that provide respectively, that phase place is reverse is cancelled out each other at least in part, and described second order sideband signals is exported by described output port as described the first and second light signals.
This execution mode provides a kind of concrete implementation of described dual wavelength maker.
According to a further execution mode, the splitting ratio of this first branch road and this second branch road is 80: 20, and the output of this Mach-Zehnder modulator, described seed photo-signal is identical with the amplitude of described second order sideband signals.In this embodiment, dual wavelength maker can be offset seed photo-signal a low energy level, ensures that the power of the second order sideband of output meets modulation and transmission demand.
According to a further execution mode, the frequency of described radiofrequency signal is 12.5GHz.The radio frequency signal frequency of 12.5GHz can produce each downlink optical signal that each uplink optical signal that frequency interval is 100GHz and frequency interval are 100GHz, meets the demand of TWDM-PON.
According to one preferred embodiment, described light separator comprises:
-Mach-Zehnder delay interferometer, has an input port and two outputs, wherein,
The first output is coupled to described optical selector, and the peak of the transmission spectrum of this first output mates respectively the wavelength of each the first light signal;
The second output is coupled to described coupler, and the peak of the transmission spectrum of this second output mates respectively the wavelength with each the second light signal.
This execution mode provides a kind of concrete implementation of described light separator.
Preferred embodiment described Corticofugal Modulation of Somatosensory module comprises fabry-Perot type laser according to one, and described optical selector comprises the second array waveguide grating, and is connected with between described light separator, described the second array waveguide grating and described coupler:
The-the first circulator, each the first light signal described light separator being provided, be separated offers described the second array waveguide grating, and will have each first light signal of downlink information to offer described coupler by the modulation multiplexing, that be reflected back of described the second array waveguide grating.
In this embodiment, the fabry-Perot type laser that use cost is lower completes modulation function, and cost is lower.
According to one preferred embodiment, between described dual wavelength maker and described light separator, be also connected with: Xie Pianqi, for removing the polarization state of described each the first and second light signals.
This preferred embodiment in, eliminated the polarization dependence of traditional injecting lock mould owing to separating inclined to one side device, so FP-LD can be used to the downlink data of modulation data rate up to 10Gb/s, improved communication performance.。
According to one preferred embodiment, this optical line terminal also comprises:
-uplink receiving module;
The-the second circulator, be connected to output port and the described uplink receiving module of described coupler, described optical line terminal, described coupler coupled signal is offered to this output port output, and the upward signal that this output port is received offers described uplink receiving module.
This execution mode provides the functional structure for uplink receiving part.
In ONU, preferably, described light selects module to comprise:
-tunable optical filter, for leaching described the first and second light signals corresponding to same seed photo-signal from received first group of light signal and second group of light signal,
Described tunable optical filter can be conditioned from any in multiple different seed photo-signals and mate.
This execution mode provides the support of ONU to multi-wavelength.
Preferably, described up modulation module is also by described the second optical signal amplification, and described up modulation module comprises reflective semiconductor optical amplifier.
Because OLT provides uplink optical signal, so ONU can adopt the reflective semiconductor optical amplifier that cost is very low (RSOA) that this uplink optical signal is amplified and modulated, reduce ONU cost.
From the angle of method, the 4th aspect of the present invention provides the method for the transmission downstream signal in a kind of optical communication, comprises the steps:
-receive the seed photo-signal of multiple different wave lengths of being re-used, and respectively for each seed photo-signal, the first light signal that generates the different wave length corresponding with this seed photo-signal as first group of light signal and the second light signal as second group of light signal;
-the first light signal corresponding to each seed photo-signal is separated in together, and the second light signal corresponding to each seed photo-signal is separated in together;
-from isolated first group of light signal corresponding to each seed photo-signal, select each the first light signal;
-correspond respectively to each the first light signal, downlink information is modulated on described the first light signal;
-there is each first light signal of downlink information to be polymerized to first group of light signal modulation;
-by the described second group of light signal being separated and described first group of light signal coupling that be re-used, modulated downlink information, and output.
Correspondingly, the 5th aspect of the present invention provides the reception downstream signal in a kind of optical communication the concurrent method of sending upward signal, comprises the steps:
-receiving optical signals, therefrom select corresponding to the first light signal in first group of light signal of the different wave length of same seed photo-signal and the second light signal in second group of light signal, and described the first and second light signals are separated from each other out, wherein, described the first light signal is modulated downlink information;
-described the first light signal being separated is detected, obtain described downlink information;
-uplink information is modulated on described the second light signal being separated, and described second light signal of modulated uplink information is reflected back to described light selects module with output.
Brief description of the drawings
By reading the detailed description that non-limiting example is done of doing with reference to the following drawings, other features, objects and advantages of the present invention will become more apparent:
Fig. 1 is the structured flowchart of existing TWDM-PON;
Fig. 2 is according to the structured flowchart of the OLT of an embodiment of the invention;
Fig. 3 is according to the schematic diagram of the dual wavelength maker of an embodiment of the invention;
Fig. 4 is according to the schematic diagram of the light separator of an embodiment of the invention;
Fig. 5 is the spectrogram of the transmission spectrum curve of the light separator shown in Fig. 4 and the input of light separator;
Fig. 6 is the spectrogram of the output of the light separator of Fig. 4;
Fig. 7 shows the optical signal spectrum of the multiple light paths position among the OLT of Fig. 3;
Fig. 8 is according to the structured flowchart of the ONU of an embodiment of the invention;
Fig. 9 is the transmission spectrum curve that the light in Fig. 8 is selected module;
Figure 10 shows the optical signal spectrum of the multiple light paths position among the ONU of Fig. 8.
Embodiment
As shown in Figure 2, the invention provides a kind of optical line terminal OLT, comprise as lower component:
The-the first array waveguide grating 11, for receiving respectively the seed photo-signal λ of multiple different wave lengths
1, λ
2, λ
3, λ
4, converged, and offered dual wavelength maker 12;
-dual wavelength maker 12, for receiving the seed photo-signal λ of the multiple different wave lengths that are re-used
1, λ
2, λ
3, λ
4, and respectively for each seed photo-signal, the first light signal that generates the different frequency corresponding with this seed photo-signal as first group of light signal and the second light signal as second group of light signal;
-light separator 14, for separating of going out first group of light signal c and second group of light signal d, respectively from two output port output;
-optical selector 16, for selecting respectively each the first light signal from isolated first group of light signal c;
-multiple Corticofugal Modulation of Somatosensory modules 17 (only illustrating one in Fig. 2), correspond respectively to each the first light signal, downlink information is modulated on described the first light signal, and feeds back to described optical selector 16;
Described optical selector 16 has modulation each first optical multiplexed signal of downlink information with become first group of light signal e together;
-coupler 18, for isolated second group of light signal d and first group of light signal e that be re-used, modulated downlink information are coupled, and output.
As shown in Figure 8, the present invention also provides a kind of optical network unit ONU, comprises as lower component:
-light is selected module 21, for receiving optical signals, therefrom select the first and second light signals corresponding to the different frequency of same seed photo-signal, and described the first and second light signals are separated from each other out, wherein, described the first light signal is modulated downlink information;
-descending receiver module 22, for described the first light signal being separated is detected, obtains described downlink information;
-up modulation module 23, for uplink information being modulated to described the second light signal being separated, and is reflected back described light by described second light signal of modulated uplink information and selects module with output.
Below by more concrete description according to the structure of optical line terminal OLT of the present invention and optical network unit ONU and function.In execution mode below, to produce the required spectrum intervals of TWDM-PON as downstream wavelength/spectrum intervals of 100GHz is as the up wavelength of 100GHz is as example describes, be appreciated that the present invention can make suitable change in the situation that of other required wavelength.
There is 4 continuous waves (CW) laser λ of 100GHz spectrum intervals
1, λ
2, λ
3, λ
4be transfused among optical line terminal OLT as seed photo-signal, and be gathered together by the first array waveguide grating 11.The optical signal spectrum that the first array waveguide grating 11 is exported is by shown in Fig. 7 (a), and these 4 CW laser are injected among dual wavelength maker 12.
Dual wavelength maker 12 receives the seed photo-signal λ of four different wave lengths that are re-used
1, λ
2, λ
3, λ
4, and respectively for each seed photo-signal, generate the first and second light signals of the different frequency corresponding with this seed photo-signal.
For a kind of implementation of dual wavelength maker, as shown in Figure 3, it uses common single Mach-Zehnder modulator (MZM) and a low speed phase-modulator of driving, and they are embedded in respectively on two branch roads of a Mach-Zehnder delay interferometer.Upper branch road is single to drive Mach-Zehnder modulator, and lower branch road is one section of optical fiber, and has a low speed phase-modulator and be used to regulate the phase difference of two branch signals.Mach-Zehnder modulator has the independent biasing control of controlling, to realize optimal performance and external radio frequency input port independently.
Below with four seed photo-signal λ
1, λ
2, λ
3, λ
4in a seed photo-signal be example, the generating principle of dual wavelength is described, be appreciated that dual wavelength maker is that each seed photo-signal generates corresponding the first and second light signals.Light source (the frequency f of input
s) with certain splitting ratio, for example, be divided into two parts at 20: 80, and be fed to two branch roads.MZM is by an electrical clock signal (frequency: f
rF) institute drives, the peak value that this clock signal is offset to transmission curve is sentenced and is suppressed odd number sideband.The fiber segment of inferior division fully sees through optical carrier.
To obtain the phase differences of 180 degree between Liang Ge branch, and control the frequency of electrical clock signal and the amplitude of bias voltage is suitable value by control phase modulator, because single spin-echo, amplitude are identical, frequency f
sthe signal at place almost can be offset completely.
Based on this design, from single seed laser, can obtain the light signal of dual wavelength, there is quadruple spectrum interval (4f
rF), frequency is separately f
s+ 2f
rF(can be described as the second light signal or right channel) and f
s-2f
rF(can be described as the first light signal or left channel), the first light signal and the second light signal can be deemed to be independently laser.Consider the needs of TWDM-PON, f
rFfor 12.5GHz, the first light signal generating for same seed photo-signal and the spectrum intervals of the second light signal are 50GHz; And because the spectrum intervals between each seed photo-signal is 100GHz, so the individual independently wavelength X of the 2x4=8 producing
1L, λ
1R, λ
2L, λ
2R, λ
4L, λ
4Roptical signal spectrum as shown in Fig. 7 (b), spectrum intervals is 50GHz.Therefore, use four light sources just can produce 8 individual wavelengths of aliging with the TWDM-PON grid of the ITU-T of 50GHz.Wherein, the seed photo-signal λ shown in dotted line
1, λ
2, λ
3, λ
4be only used to show its frequency location, in fact these seed photo-signals are offset completely or are offset to very low light intensity level, can in communication, not produce substantially impact again.
Be appreciated that dual wavelength maker also can adopt other modes to realize, for example, adopt Mach-Zehnder modulator and the corresponding control/processing signals module of two cascades.One of ordinary skill in the art can realize by other implementation the function of dual wavelength maker, and the present invention does not repeat them here.
Next, the 2x4=8 condensing together that generates first light signal and the second light signal inclined to one side device of a solution (depolarizer) 13 of being fed, to change their polarized state (SoP) into pseudorandom polarization.Because Xie Pianqi has been used to eliminate the polarization dependence that traditional input locks, and the wavelength that the outside that is derived from continuous wave is injected has good correlation properties, so in the time of modulation the first light signal, can carry out the downlink data of modulation rate up to 10Gb/s by the lower FP-LD of use cost, this also will illustrate hereinafter.Be appreciated that this Xie Pianqi is a kind of preferred implementation that improves modulation rate in order to mate FP-LD, it is omissible.
Afterwards, the first light signal and the second light signal that condense together are sent to light separator 14, and this light separator 14 is by the first light signal λ corresponding to each seed photo-signal
1L, λ
2L, λ
3L, λ
4Lbe separated in together, and by the second light signal λ corresponding to each seed photo-signal
1R, λ
2R, λ
3R, λ
4Rbe separated in together.
In a concrete realization, a light Mach-Zehnder delay interferometer (MZDI) is used to separate 8 wavelength signals that generate, and forms each the first light signal λ
1L, λ
2L, λ
3L, λ
4Lthe first group of light signal and each the second light signal λ that form
1R, λ
2R, λ
3R, λ
4Rthe second group of light signal forming.Fig. 4 shows the structure of designed Mach-Zehnder delay interferometer, it has an input port IN and two output OUT1 and OUT2, the free spectral range of MZDI should be 100GHz, and the spectrum curve of the first and second outputs skew 50GHz, therefore, the peak of the transmission spectrum of the first output OUT1 mates respectively the wavelength of each the first light signal, as shown in the spectrum curve of solid line in Fig. 5; The peak of the transmission spectrum of the second output OUT2 mates respectively and the wavelength of each the second light signal and its transmission spectrum, as shown in the spectrum curve of dotted line in Fig. 5.This MZDI can make of commercial ordinary optic fibre, and cost is very low, and stability also can well be controlled.First output OUT1 output four left channels (the first light signal) λ of this interferometer
1L, λ
2L, λ
3L, λ
4L, as shown in Fig. 6 and Fig. 7 (c), second output OUT2 output four right channels (the second light signal) λ
1R, λ
2R, λ
3R, λ
4R, as shown in Fig. 6 and Fig. 7 (d).
Be appreciated that this light separator also can have much other implementations, for example, adopt grating to realize, the present invention repeats no more.
The first output OUT1 of light separator 14 is coupled to the first optical circulator 15, four left channels of this first optical circulator (the first light signal) λ
1L, λ
2L, λ
3L, λ
4Loffer optical selector 16.Optical selector 16 is from being separated in four the first light signal λ together
1L, λ
2L, λ
3L, λ
4Lmiddlely select respectively each the first light signal as four independent channels, each wavelength is used as seed light and is injected in Corticofugal Modulation of Somatosensory module by outside.Each Corticofugal Modulation of Somatosensory module corresponds respectively to each the first light signal, and Fig. 2 only shows corresponding to the first light signal λ
1Lcorticofugal Modulation of Somatosensory module 17.Each Corticofugal Modulation of Somatosensory module is modulated to downlink information on the first light signal, and feeds back to optical selector 16.In specific implementation, Corticofugal Modulation of Somatosensory module can be realized by common FP-LD.FP-LD after outside injection locking is modulated by downstream signal DL.Respectively to four the first light signal λ
1L, λ
2L, λ
3L, λ
4L, obtain the signal spectrum shown in for example Fig. 7 (e).
Optical multiplexer 16 has each first optical multiplexed signal of downlink information with together by modulation, offers the first loop device 15.This signal is offered coupler 18 by the first loop device 15.
Coupler 18 will be separated in each the second light signal λ together, not modulated
1R, λ
2R, λ
3R, λ
4Rwith that be re-used, modulated each first light signal λ of downlink information
1L, λ
2L, λ
3L, λ
4Lbe coupled, and export by the second loop device 19.
OLT is connected to remote node RN by single optical fiber, by not modulated each second light signal λ of coupling
1R, λ
2R, λ
3R, λ
4Rwith that be re-used, modulated each first light signal λ of downlink information
1L, λ
2L, λ
3L, λ
4Lsend to remote node RN.
At remote node RN place, as shown in Figure 8, optical splitter is used to the downlink optical signal of arrival to be allocated to each ONU.Therefore embodiments of the present invention are supported traditional ODN framework, can reduce significantly the cost of actual realization.Fig. 8 at length illustrates corresponding to λ
1Land λ
1RoNU, the structure of other ONU is identical, in order briefly no longer to illustrate.
As shown in Figure 8, optical network unit ONU comprises:
-light is selected module 81, and for receiving optical signals, therefrom select the first and second light signals corresponding to the different frequency of same seed photo-signal, and the first and second light signals are separated from each other out, wherein, the first light signal is modulated downlink information;
-descending receiver module 82, for the first light signal being separated is detected, obtains downlink information;
-up modulation module 83, for uplink information being modulated to the second light signal being separated, and selects module with output the second light signal reflected light of modulated uplink information.
Fig. 9 shows the transmission spectrum curve of light selection module 81, and the peak value of the transmission spectrum that the first output OUT1 is corresponding is corresponding to λ
1L, and the corresponding λ of the peak value of transmission spectrum corresponding to the second output OUT2
1R., the light signal that the first output OUT1 provides to descending receiver module 82, as shown in Figure 10 (a), has only comprised the first light signal λ of downstream signal modulated
1L.The light signal that the second output OUT2 provides to up modulation module 83, as shown in Figure 10 (b), comprises not the second light signal λ of the continuous wave of modulated any signal
1R.
Preferably, it is adjustable that this light is selected module 81, and it can be conditioned from any in multiple different seed photo-signals mates, and can be adjusted and export first light signal and second light signal corresponding with other seed photo-signals.Be appreciated that this is only preferred embodiment, at this ONU, regularly corresponding certain seed photo-signal wavelength, this light selects module can select regularly left channel and the right channel of this seed photo-signal wavelength.
Descending receiver module 82 is to by this first light signal λ
1Ldetect, obtain downlink information, complete downlink communication.The specific implementation of descending reception is that one of ordinary skill in the art is known, does not repeat them here.
Up modulation module 83 is preferably realized by reflective semiconductor optical amplifier (RSOA).It is very promising realizing with RSOA that ONU in WDM-PON has been confirmed as, and this is to amplify and the function of modulation because it has simultaneously.In the present invention, commercial low cost RSOA can be used in the upward signal of modulation 2.5Gb/s, has the small signal gain of 20dB, the protection power output of 3dB, and very low front end factor reflection (frontfactor reflectivity).The second channel wavelength obtaining after upward signal modulation is as shown in Figure 10 (c), and this modulation wavelength can send it back OLT.In the present invention, descending and upward signal uses different carrier wavelengths, therefore rear end reflection (back-reflection) is had to stronger tolerance, and rear end reflection is that single fiber is fed to a main deteriorating effect in scheme.In addition, with respect to traditional descending carrier reuse scheme, because right channel (the second light signal) is not modulated continuous light wave, this can improve upstream performance effectively.
Afterwards, in OLT, upward signal is passed to uplink receiving module by the second loop device 19.Uplink receiving module comprises that an array waveguide grating 20 and each uplink receiver 21, array waveguide grating 20 separate the second up light signal of each different wave length, offers respectively corresponding uplink receiver 21 and detects.This process is similar compared with the prior art, does not repeat them here.
In embodiments of the present invention, common low cost RSOA is used as adjustable transmitter, has saved the expensive tunable laser in ONU, and therefore the cost of ONU can be reduced widely.In order further to reduce the cost of OLT, in embodiments of the present invention, the downstream transmitter of 10Gb/s can be used by the outside injection FP-LD of relevant seed light locking and realize, and saves the Distributed Feedback Laser of expensive 10Gb/s.In embodiments of the present invention, the complexity of system is positioned among OLT to a certain extent, need to increase an extra dual wavelength generator, the inclined to one side device of solution, the AWG of a 100GHz spectrum intervals, a MZDI, a coupler and a loop device.
Following table has been listed the cost of TWDM-PON network and the cost compare of the PON network that embodiments of the present invention form of existing forecast scheme configuration, and wherein this network comprises an OLT and 64 ONU.This comparison based on parts be all the device that business can be used.
Table 1
For the TWDM-PON system of 64 channels, compared with prior art, the present invention can reduce costs approximately 8000 dollars.Especially, in the time that ONU user's quantity increase is more, the reduction of system cost is more obvious.
It should be noted that, in the situation that not conflicting, the combination in any mutually of the feature in embodiment and embodiment in the application.
Certainly; the present invention also can have other various embodiments; in the situation that not deviating from spirit of the present invention and essence thereof; those of ordinary skill in the art can make according to the present invention various corresponding changes and distortion, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.
One of ordinary skill in the art will appreciate that all or part of step in said method can carry out instruction related hardware by program and complete, described program can be stored in computer-readable recording medium, as read-only memory, disk or CD etc.Alternatively, all or part of step of above-described embodiment also can realize with one or more integrated circuits.Correspondingly, the each module/unit in above-described embodiment can adopt the form of hardware to realize, and also can adopt the form of software function module to realize.The present invention is not restricted to the combination of the hardware and software of any particular form.
Claims (15)
1. an optical line terminal, comprises as lower component:
The-the first array waveguide grating (11), for receiving respectively the seed photo-signal of multiple different wave lengths, is converged, and offers dual wavelength maker;
-dual wavelength maker, for receiving the seed photo-signal of the multiple different wave lengths that are re-used, and respectively for each seed photo-signal, generates the first and second light signals of the different frequency corresponding with this seed photo-signal;
-light separator, for separating of each the first light signal as first group of light signal and each the second light signal as second group of light signal, by first group of light signal corresponding to each seed photo-signal and second group of optical multiplexed signal with respectively from two output port output;
-optical selector, for selecting respectively each the first light signal from first group of light signal;
-multiple Corticofugal Modulation of Somatosensory modules, correspond respectively to each the first light signal, downlink information is modulated on described the first light signal, and feeds back to described optical selector;
Described optical selector has each first optical multiplexed signal of downlink information to use together as first group of light signal modulation;
-coupler, for described second group of light signal and described first group of light signal that be re-used, modulated downlink information are coupled, and output.
2. optical line terminal according to claim 1, it is characterized in that, described dual wavelength maker comprises input port, the first branch road, the second branch road in parallel, and output port, described input port is divided into described the first branch road and described the second branch road by the seed photo-signal of input by certain splitting ratio, and, after the signal coherence of described the first branch road and the second branch road relates to and by described output port, export
Wherein, described the first branch road comprises a Mach-Zehnder modulator, described Mach-Zehnder modulator receives the bias voltage of radiofrequency signal and certain amplitude of certain frequency, makes this Mach-Zehnder modulator export described seed photo-signal and is the second order sideband signals of this certain frequency of twice with described seed photo-signal frequency interval;
Described the second branch road comprises one section of waveguide, and has a phase-modulator, and described phase-modulator, for regulating the phase place of the described seed photo-signal on this second branch road, makes this phase place and former single spin-echo;
Described the first branch road and described the second branch road described seed photo-signal that provide respectively, that phase place is reverse is approximate cancels out each other completely, and described second order sideband signals is exported by described output port as described the first and second light signals.
3. optical line terminal according to claim 1, it is characterized in that, the splitting ratio of this first branch road and this second branch road is 80: 20, the frequency of described radiofrequency signal is 12.5GHz, and the output of this Mach-Zehnder modulator, described seed photo-signal is identical with the amplitude of described second order sideband signals.
4. optical line terminal according to claim 1, is characterized in that, described light separator comprises:
-Mach-Zehnder delay interferometer, has an input port and two outputs, wherein,
The first output is coupled to described optical selector, and the centre wavelength of the transmission spectrum of this first output is mated respectively the wavelength of each the first light signal;
The second output is coupled to described coupler, and the centre wavelength of the transmission spectrum of this second output is mated respectively the wavelength with each the second light signal.
5. optical line terminal according to claim 1, it is characterized in that, described Corticofugal Modulation of Somatosensory module comprises fabry-Perot type laser, and described optical selector comprises the second array waveguide grating, and is connected with between described light separator, described the second array waveguide grating and described coupler:
The-the first circulator, each the first light signal described light separator being provided, be separated offers described the second array waveguide grating, and will have each first light signal of downlink information to offer described coupler by the modulation multiplexing, that be reflected back of described the second array waveguide grating.
6. optical line terminal according to claim 1 or 5, is characterized in that, between described dual wavelength maker and described light separator, is also connected with:
-Xie Pianqi, for removing the polarization state of described each the first and second light signals.
7. optical line terminal according to claim 1, is characterized in that, also comprises:
-uplink receiving module;
The-the second circulator, be connected to output port and the described uplink receiving module of described coupler, described optical line terminal, described coupler coupled signal is offered to this output port output, and the upward signal that this output port is received offers described uplink receiving module.
8. an optical network unit, comprises as lower component:
-light is selected module, for receiving optical signals, therefrom select corresponding to the first light signal in first group of light signal same seed photo-signal, different frequency and the second light signal in second group of light signal, and described the first and second light signals are separated from each other out, wherein, described the first light signal is modulated downlink information;
-descending receiver module, for described the first light signal being separated is detected, obtains described downlink information;
-up modulation module, for uplink information being modulated to described the second light signal being separated, and is reflected back described light by described second light signal of modulated uplink information and selects module with output.
9. optical network unit according to claim 8, is characterized in that, described light selects module to comprise:
-tunable optical filter, for leach described the first and second light signals corresponding to same seed photo-signal from received light signal,
Described tunable optical filter can be conditioned from any in multiple different seed photo-signals and mate.
10. optical network unit according to claim 8, is characterized in that, described up modulation module is also by described the second optical signal amplification,
Described up modulation module comprises reflective semiconductor optical amplifier.
11. 1 kinds of optical communication systems, comprising:
-according to the optical line terminal described in any one in claim 1-7;
-optical branching device, is connected with described optical line terminal;
-multiple according to the optical network unit described in any one in claim 9-10, be connected with described optical branching device respectively;
The downlink optical signal that described optical branching device provides described optical line terminal is along separate routes to each optical network unit.
The method of the transmission downstream signal in 12. 1 kinds of optical communications, comprises the steps:
-receive the seed photo-signal of multiple different wave lengths of being re-used, and respectively for each seed photo-signal, the first light signal that generates the different wave length corresponding with this seed photo-signal as first group of light signal and the second light signal as second group of light signal;
-first group of optical multiplexed signal corresponding to each seed photo-signal used together, and second group of optical multiplexed signal corresponding to each seed photo-signal used together;
-from first group of light signal corresponding to each seed photo-signal, select each the first light signal;
-correspond respectively to each the first light signal, downlink information is modulated on described the first light signal;
-there is each first light signal of downlink information to be multiplexed with first group of light signal modulation;
-by multiplexing described second group of light signal together and described first group of light signal coupling that be re-used, modulated downlink information, and output.
13. methods according to claim 12, is characterized in that, before separating described first group and second group of light signal, described first group and second group of light signal are separated partially, remove the polarization state of described first group and second group light signal.
The concurrent method of sending upward signal of reception downstream signal in 14. 1 kinds of optical communications, comprises the steps:
-receiving optical signals, therefrom select corresponding to the first light signal in first group of light signal of the different wave length of same seed photo-signal and the second light signal in second group of light signal, and described the first and second light signals are separated from each other out, wherein, described the first light signal is modulated downlink information;
-described the first light signal being separated is detected, obtain described downlink information;
-uplink information is modulated on described the second light signal being separated, and described second light signal of modulated uplink information is reflected back to described light selects module with output.
15. methods according to claim 14, is characterized in that, before described the second light signal of output, also described the second light signal are amplified.
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