CN101635700B - ASK/DPSK hybrid modulation method, device and system - Google Patents
ASK/DPSK hybrid modulation method, device and system Download PDFInfo
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Abstract
The invention relates to an ASK/DPSK hybrid modulation method. An optical line terminal (OLT) sends a downlink amplitude shift keying (ASK) modulation signal with uniformly inserted '1' codes to an optical network unit (ONU) and each inserted '1' code is smaller than a bit length of an uplink difference phase shift keying modulation (DPSK) signal; the ONU divides the downlink ASK modulation signal inserted with '1' codes into two paths; one path directly receives the ASK signal, and the other path modulates to generate the uplink DPSK signal which enters into a transmission link to be transmitted into the OLT which carries out modulation and receiving on the uplink DPSK signal. The invention also provides an ASK/DPSK hybrid modulation device and a system. In the embodiment of the invention, the scheme of inserting '1' codes is adopted to lead two successive bits which modulate the uplink DPSK signal are both '1' codes, thus the modulation effect is better, and the influence of inherent signal crosstalk of the ASK/DPSK hybrid modulation is inhibited; the influence of nonlinear effect is reduced, and the extinction ratio does not restrict the DPSK signal receiving, and the transmission performance of the system is greatly improved.
Description
Technical field
The present invention relates to technical field of optical network communication, relate in particular to a kind of ASK/DPSK hybrid modulation method, Apparatus and system.
Background technology
EPON (PON, Passive Optical Network) is the Technology of Light Access Network of relatively being paid close attention at present, and it uses wavelength division multiplexing flexibly, and combines time-division multiplex technology, can make network capacity and resource utilization reach a very considerable level.In recent years along with the increase gradually of Access Network traffic carrying capacity, the diversification of service, in the framework of PON, introducing Hybrid Modulation Technology becomes a kind of new research direction.Its advantage is directly at Wave division multiplexing passive optical network (WDM-PON; Wavelength divisionmultiplex-Passive Optical Network) utilizes various signal encoding superposition modulated technology on the basis; Realize the noiseless transmission of uplink and downlink signals, avoid expensive system upgrade spending, and reduced at optical network unit (ONU; Optical Network Unit) additional apparatus in has been simplified the complexity of whole system.
Said Hybrid Modulation Technology is a kind of advanced person's a modulation system; Adopt two kinds of relatively independent modulation systems exactly; Two groups of information are modulated to does not have the independent transmission of crosstalking on the same light carrier; Two groups of information are relatively independent, and can receive respectively at receiver end, adopt demodulator separately to detect.Compound modulation has been practiced thrift signal bandwidth, has improved the transmission transparency, and different modulation formats can effectively be resisted the influence of nonlinear effect in transmission, and the bit rate of two groups of signals also can be uncorrelated mutually with the sign indicating number type, and receive mode is also relatively independent.
Present progress is to be applied to compound modulation in the Access Network; Method is (CO from the central office; Central Office) adopts a kind of modulation format transmission of downlink signal to ONU; Generation for ONU end upward signal does not re-use another reflector, but directly utilizes the flashlight of down link to adopt another kind of modulation format to carry out secondary modulation, returns original link transmission then to CO.This hybrid modulation principle of in Access Network, utilizing is transmitted uplink and downlink signals light simultaneously, and advantage is to have saved a signal optical source at the ONU end, and has practiced thrift bandwidth resources, can realize the wavelength transparent transmission; Signal link can be selected single fiber or two Optical Fiber Transmission, but because the influence of Rayleigh scattering can make the single fiber limited transmission distance.Owing to need provide a continuous light to modulate to upward signal; Therefore downstream signal is generally selected frequency keying modulation (FSK, Frequency-shift Keying), phase shift keying (PSK, phaseshift keying), polarization keying modulation (PolSK; Polarization-shift Keying) modulation format such as; Also the gain saturation effect of available semiconductor optical amplifier is carried out signal and is wiped, and perhaps changes other modulation system such as signal extinction ratio and realizes, reaches same effect.
The technical scheme of the prior art one relevant with the present invention is described below:
Be illustrated in figure 1 as amplitude keying modulation (ASK, Amplitude-shift Keying)/differential phase keying (DPSK) modulation (DPSK, Differential Phase-shift Keying) modulation system and be applied to the implementation method of Access Network., optical line terminal (OLT, Optical Line Terminal) end downstream signal directly drives phase-modulator (PM, Phase Modulator) after carrying out differential coding; Produce dpsk signal, dpsk signal arrives the ONU end through the transmission of a segment standard monomode fiber (SMF, Standard single Mode Fiber); Here signal is divided into two-way; One the tunnel uses interferometer and photodiode that downstream signal is separated to be in harmonious proportion receives, and another road is carried out secondary modulation with upward signal drive strength modulator (IM, Intensity Modulation) and produced the ASK signal; Get into transmission link by circulator; Directly received at the OLT end at last, accomplished the uplink and downlink signal transfer functions of whole system like this, because downlink data is embodied on the phase information of variation; It is constant that its flashlight remains light intensity; And the light carrier that is used for the upward signal modulation directly utilizes downstream signal light to obtain through the beam splitter beam split, and its amplitude information and phase information can receive separately, so can't cause crosstalking between data.
The inventor finds in realizing process of the present invention; There is following shortcoming at least in above-mentioned prior art one: in practical application; ONU end-apparatus spare cost is higher, needs Mach-Zehnder ear delay interferometer (MZDI, Mach-Zehnder Delayed Interferometer) demodulation dpsk signal; Add the intensity modulator that is used for secondary modulation, increased many use expenses to the user.
The technical scheme of the prior art two relevant with the present invention is following:
In order to overcome the high problem of ONU end cost in the prior art one; This programme proposes downstream signal and uses the ASK modulation; The scheme that upward signal uses DPSK to modulate only receives descending ASK signal with a photodiode and a phase-modulator is modulated upward signal; Simplify the project organization of ONU end, reduced user's use cost.
And realize finding in the process of the present invention that there is following shortcoming at least in above-mentioned prior art two the inventor:
Being used for the DPSK modulated signal light is not continuous wave (CW, Continuous Wave) light, but the ASK signal, wherein the power of " 0 " sign indicating number is lower, loses phase information easily, and the mediation of separating that influences dpsk signal receives, and causes crosstalking between the uplink and downlink signal.In order to guarantee the reception of dpsk signal, need to improve input optical power, the extinction ratio of ASK signal also is restricted, and can improve the receiving sensitivity of ASK signal like this, makes system performance degradation, reduces the reliability of Network Transmission.In addition, the demodulation dpsk signal needs 1 strict bit interferometer (MZDI).Because upward signal speed is generally slower, this just means that the MZDI amount is longer, and this brings great challenge for the required precision of element manufacturing, also is unfavorable for integrated.
Summary of the invention
The embodiment of the invention provides a kind of ASK/DPSK hybrid modulation method, Apparatus and system.
The embodiment of the invention realizes through following technical scheme:
The embodiment of the invention provides a kind of ASK/DPSK hybrid modulation method, comprising:
Optical line terminal OLT is sent the descending amplitude keying modulation ASK signal that evenly inserts " 1 " sign indicating number and is given optical network unit ONU, and " 1 " code interval of being inserted is less than a bit length of up differential phase keying (DPSK) modulation dpsk signal;
ONU is divided into two-way with the descending ASK signal of said insertion " 1 " sign indicating number, and one the tunnel directly receives said ASK signal, and another road modulation produces up dpsk signal, gets into transmission link and transfers to said OLT;
Said OLT carries out demodulate reception to said up dpsk signal.
The embodiment of the invention provides a kind of ASk/DPSK hybrid modulation device, comprising:
" 1 " sign indicating number inserts the unit, is used for evenly inserting " 1 " sign indicating number at downlink data, and " 1 " code interval of being inserted is less than a bit length of up differential phase keying (DPSK) modulation dpsk signal;
The downstream signal generation device is used for the downlink data of said even insertion " 1 " sign indicating number is carried out amplitude keying modulation ASK, is evenly inserted the descending ASK signal behind " 1 " sign indicating number;
The upward signal receiving system is used for the up dpsk signal of demodulate reception.
The embodiment of the invention provides a kind of ASK/DPSK hybrid modulation system, comprising: central office CO and optical network unit ONU,
Said CO adopts the ASK/DPSK hybrid modulation method, in downlink data, evenly inserts " 1 " sign indicating number, and the line amplitude of going forward side by side keying modulation ASK modulation is evenly inserted the descending ASK signal behind " 1 " sign indicating number, and sent said descending ASK signal; " 1 " code interval of being inserted is less than a bit length of up differential phase keying (DPSK) modulation dpsk signal;
Said ONU is divided into two-way with the descending ASK signal behind said even insertion " 1 " sign indicating number, and one the tunnel directly receives said descending ASK signal, and another road modulation produces up differential phase keying (DPSK) modulation dpsk signal, and sends said up dpsk signal to said CO;
Said CO also is used to receive said up dpsk signal, and " 1 " code interval of said insertion is less than a bit length of up dpsk signal.
Technical scheme by the invention described above embodiment provides can find out that embodiment of the invention downstream signal adopts the ASK modulation, and upward signal adopts the DPSK modulation, and adopts " 1 " sign indicating number to insert encoding scheme, has following superiority:
1) down high speed ASK signal is easy to receive, and only needs common PIN detector to get final product; Up dpsk signal can be placed on the OLT end to the DPSK demodulation and carry out, and helps centralized control and management.Therefore this ASK/DPSK Hybrid Modulation Technology can design by simplied system structure, reduces cost.
2) owing to adopt " 1 " sign indicating number to insert encoding scheme; Then up dpsk signal is being separated timing, because two continuous bits are " 1 " sign indicating number, demodulation better effects if before and after the demodulation; Suppressed the influence that ASK/DPSK hybrid modulation intrinsic signal is crosstalked; And can reduce the influence of nonlinear effect, and extinction ratio also no longer restricts dpsk signal and receive, improved the transmission performance of system greatly.
Description of drawings
Fig. 1 is applied to the Access Network sketch map for prior art ASK/DPSK modulation system;
Fig. 2 is the embodiment of the invention one an ASK/DPSK hybrid modulation method operational flowchart;
Fig. 3 is that the embodiment of the invention is inserted the coded system sketch map for one " 1 " yard;
Fig. 4 is the embodiment of the invention one a DPSK demodulate reception method sketch map one;
Fig. 5 is the embodiment of the invention one a DPSK demodulate reception method sketch map two;
Fig. 6 is the present invention's " 1 yard insertion " coding ASK/DPSK hybrid modulation instantiation transmission system installation drawing;
Fig. 7 is the present invention's instantiation signal sensitivity shown in Figure 6 and ASK extinction ratio graph of a relation;
Fig. 8 is the embodiment of the invention two ASK/DPSK hybrid modulation apparatus module sketch mapes;
Fig. 9 is applied to the Access Network sketch map for the embodiment of the invention two said ASK/DPSK hybrid modulation devices;
Figure 10, Figure 11 are applied to behind the Access Network Rayleigh scattering and stimulated Brillouin scattering to the systematic influence sketch map for embodiment of the invention ASK/DPSK hybrid modulation device.
Embodiment
To combine the accompanying drawing in the embodiment of the invention below, the technical scheme in the embodiment of the invention is carried out clear, intactly description, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills are not making the every other embodiment that is obtained under the creative work prerequisite, all belong to the scope of the present invention's protection.
In the ASK/DPSK hybrid modulation method; The extinction ratio of ASK signal is restricted to be can right demodulation and reception for dpsk signal, and the device that the DPSK demodulation is used is MZDI, and it utilizes the relevant principle of flashlight of continuous two bits; Phase place is consistent just to be strengthened; Phase difference π just offsets, and converts phase information into amplitude information like this, the convenient reception.But become complicated through situation after the hybrid modulation, table 1 provides and utilizes MZDI demodulation dpsk signal luminous power in the ASK/DPSK hybrid modulation, supposes that the light intensity of " 1 " sign indicating number is 1, and " 0 " sign indicating number light intensity is ε.
Table 1
Can find out that from table 1 signal after the demodulation has 5 power ranks,, require at least (1-ε) in order to guarantee the judgement of last " 1 " sign indicating number and " 0 " sign indicating number
2/ 4＜ε
2, draw ε＞1/3, know that thus extinction ratio must be restricted.
Based on above-mentioned analysis, the embodiment of the invention one provides a kind of ASK/DPSK hybrid modulation method, and downstream signal adopts the ASK modulation; Upward signal adopts the DPSK modulation, utilizes the coding method of " 1 yard insertion ", and downlink data is encoded; Separate timing the ASK signal being modulated the up dpsk signal that obtains like this; Continuous two bits in front and back that guarantee demodulation are " 1 " sign indicating number, thereby obtain better demodulation effect, and extinction ratio no longer restricts the reception of up dpsk signal.
Said " 1 yard insertion "; In descending ASK signal, inserted " 1 " sign indicating number exactly uniformly; " 1 " sign indicating number of said insertion does not have any data message, just is used for optimizing the dpsk signal demodulation, and the interval of " 1 " sign indicating number that inserts must be less than a bit length of dpsk signal; Guarantee to be used for the MZDI retardation of demodulation dpsk signal simultaneously also for inserting the interval of " 1 " sign indicating number, so just can demodulate upstream data in the position of inserting " 1 " yard.Said " 1 yard insertion " method comprises: in the circuit code sequence of downlink data, evenly insert " 1 " sign indicating number, and then carry out the ASK modulation, obtain the descending ASK signal of said even insertion " 1 " sign indicating number.
Present embodiment said ASK/DPSK hybrid modulation method concrete operations flow process is as shown in Figure 2, comprises the steps:
Step 1:OLT end sends the descending ASK signal that evenly inserts " 1 " sign indicating number;
The method of the described even insertion of present embodiment " 1 " sign indicating number is to realize through the coding of electricity at the OLT end; Promptly in the circuit code sequence of downlink data, evenly insert " 1 " sign indicating number; And then carry out the ASK modulation, obtain the descending ASK signal of said even insertion " 1 " sign indicating number.The method of said insertion " 1 " sign indicating number can realize through chip, the sign indicating number type of final output and common 8B10B, and the sign indicating number type of 9B10B is similar.This type signal on the frequency spectrum except having the clock signal at the correspondent frequency point; The not too big difference of whole power spectrum envelope and primary signal; To each bit, remain nonreturn to zero code (NRZ, NonReturn to Zero); Do not have the burst pulse problem, dispersion management does not need additional designs yet.
In the application of Access Network; Usually the transmission rate of uplink and downlink is asymmetric; Downlink transfer speed will be higher than uplink speed far away; If comprise N descending ASK signal bit in 1 up dpsk signal bit time slots, then every N bit evenly inserts m " 1 " sign indicating number in descending ASK signal bit stream, promptly inserts in 1 corresponding up dpsk signal bit time slots of " 1 " sign indicating number back to comprise m " 1 " sign indicating number.The number m of said insertion " 1 " sign indicating number as long as guarantee have in each dpsk signal bit time slots insertion 1 " sign indicating number; so just can guarantee the reception of up dpsk signal; thereby do not need strict aligning, it is yard slightly just passable synchronously to need only the insertion of dpsk signal and ASK signal.As shown in Figure 3, for " 1 " sign indicating number inserts the coded system sketch map, corresponding ASK signal has all inserted 4 " 1 " sign indicating number uniformly in each dpsk signal bit time slots.
In the coding method of present embodiment, the bandwidth efficiency of ASK signal is N/ (N+m), is the function of m, and therefore selected m value need be taken into account the receiving sensitivity of dpsk signal and the bandwidth availability ratio of ASK signal.
Step 2: the descending ASK signal that transmits said even insertion " 1 " sign indicating number is held to ONU;
The descending ASK signal that step 3:ONU end will evenly insert " 1 " sign indicating number is divided into two-way, and one the tunnel directly receives said ASK signal, and another road modulation produces up dpsk signal, gets into transmission link and transfers to said OLT;
The descending ASK signal of said even insertion " 1 " sign indicating number that the ONU end will receive is divided into two-way through coupler, and one the tunnel can use a photodiode directly to receive said ASK signal.Another road uses phase-modulator to carrying out the DPSK modulation at first to the preparatory differential coding of upstream data then, produces up dpsk signal, gets into transmission link through circulator afterwards and transfers to the OLT end;
The said up dpsk signal of step 4:OLT end demodulate reception.
Present embodiment uses the MZDI demodulator that up dpsk signal is carried out demodulate reception.
First kind of demodulate reception method that present embodiment provides is as shown in Figure 4:
MZDI demodulator time-delay arm lengths is 1 dpsk signal bit time; If in each dpsk signal bit time slots, evenly insert m " 1 " sign indicating number; The m that inserts in then said each dpsk signal bit time slots " 1 " sign indicating number is one group; Be concerned with the m that inserts in next dpsk signal bit time slots " 1 " sign indicating number, as being that preceding 4 " 1 " sign indicating number is concerned with back 4 " 1 " sign indicating number among Fig. 4.The demodulation result that obtains is that m the bit that can represent upstream data arranged in 1 dpsk signal bit time slots; Any reception in this m bit of can random probing during judgement relevant back; Also can survey this m bit all; Select the maximum bit of probability to receive, thereby reduce error code.For example, through asking the mean value of m bit, and select the bigger result of probability, thereby reduce error through the method for threshold judgement.
Second kind of demodulation method that present embodiment provides is as shown in Figure 5:
MZDI demodulator time-delay arm lengths is shortened to 1/m dpsk signal bit time, in Fig. 5, if m is 4; Then postponing brachium is 1/4 of 1 dpsk signal bit time slots, is concerned with at " 1 " sign indicating number of separating each insertion of timing " 1 " sign indicating number with preceding 1 insertion like this, if " 1 " of inserting sign indicating number is in same dpsk signal bit time slots; Because phase place is identical; Relevant result is 0, has only adjacent insertion " 1 " sign indicating number to be positioned at dpsk signal bit time slots edge, and " 1 " sign indicating number of promptly preceding 1 insertion is in a last psk signal bit time slots; Demodulation result has just reflected phase change like this, is the result that need obtain.So when receiving in the method, need the control time decision, selective reception is positioned at dpsk signal bit time slots edge, and be positioned at " 1 " sign indicating number that different DPSK bit time slots insert bit after relevant.This method is because of 1/m＜1, so the time-delay arm of demodulator can be done shortlyer.For example, it is 8cm optical fiber that the MZDI that 2.5Gb/s DPSK is corresponding postpones brachium, and inserts the MZDI demodulation that can use 10Gb/s behind 4 bits, postpones brachium and is merely 2cm.Short delay arm has better stability, and device also is easy to integrated and exploitation.
Hence one can see that, and the said hybrid modulation method of present embodiment promptly can adopt existing demodulation mode that up dpsk signal is carried out demodulate reception, also can adopt the scheme of dwindling MZDI demodulator time-delay arm lengths to carry out demodulate reception.
Downstream signal adopts the ASK modulation among the invention described above embodiment, and upward signal adopts the DPSK modulation, and the superiority that adopts " 1 " sign indicating number to insert encoding scheme mainly comprises:
1) down high speed ASK signal is easy to receive, and only needs common PIN detector to get final product, and does not relate to the frequency discrimination and the phase demodulating of FSK and dpsk signal needs; Up dpsk signal can be placed on the OLT end to the DPSK demodulation and carry out, and helps centralized control and management.Therefore this ASK/DPSK Hybrid Modulation Technology can design by simplied system structure, reduces cost.
2) adopt " 1 " sign indicating number to insert encoding scheme; Up dpsk signal is separated timing, because two continuous bits are " 1 " sign indicating number before and after the demodulation, the demodulation effect is best; Suppressed the influence that ASK/DPSK hybrid modulation intrinsic signal is crosstalked; And can reduce the influence of nonlinear effect, and extinction ratio also no longer restricts dpsk signal and receive, improved the transmission performance of system greatly.
Can reduce the retardation of MZDI when 3) adopting second kind of demodulation method, shorten the delay arm lengths, improve its job stability.
Further specify the feasibility and the superiority of the said scheme of the embodiment of the invention below through instantiation.
Be illustrated in figure 6 as this instance " 1 yard insertion " coding ASK/DPSK hybrid modulation transmission system installation drawing.Wherein, Light source is the outside cavity gas laser (ECL, External Cavity Laser) of wavelength-tunable, and its operation wavelength can be 1550nm; Drive Mach-Zehnder ear modulator (MZM by the downstream data flow of representing downstream signal; Mach-Zehnder Modulator) produce the ASK signal, as shown in Figure 6, said downstream data flow can be the data flow of 40Gb/s; In downlink data, evenly insert " 1 " sign indicating number and carry out the descending ASK signal that " 1 " sign indicating number is evenly inserted in the ASK modulation, make " 1 " sign indicating number that insertion is all arranged in corresponding each bit time slots of up dpsk signal.The ASK signal is through SMF and dispersion compensating fiber (DCF, Dispersion Compensating Fiber) transmission, and is as shown in Figure 6 to the ONU end, can adopt the SMF of 40km and 6kmDCF to transmit said ASK signal.At the ONU end, said descending ASK signal is coupled device and is divided into two-way: a route photodiode directly receives, and surveys the ASK signal; Another road produces up dpsk signal through PM; Get into former transmission link by circulator and transfer to OLT; At the OLT end, earlier with this dpsk signal of MZDI demodulation, and then by photodiode detection reception; All right electricity consumption low pass filter is to suppress high-frequency noise, like the electric low pass filter of the 1.8GHz among Fig. 6 in the said device.
Obtain the curved line relation between dpsk signal receiving sensitivity and the ASK signal extinction ratio through above-mentioned experiment, as shown in Figure 7.It is generally acknowledged that when ASK signal and the dpsk signal receiving sensitivity isochronous system service behaviour that good balance arranged and the best is arranged mutually promptly to put pairing delustring ratio be best extinction ratio for ASK signal receiving sensitivity curve and dpsk signal receiving sensitivity curve intersection.See from Fig. 7; Utilize " 1 yard insertion " coded system when improving extinction ratio, can reduce the receiving sensitivity of ASK and dpsk signal; In above-mentioned instance; Utilize " 1 yard insertion " coded system can be so that best extinction ratio is brought up to 9dB from 7dB, the receiving sensitivity of ASK, the dpsk signal 6dB that also descended be many, and system is more strong.
The embodiment of the invention two provides a kind of ASK/DPSK hybrid modulation device, and this device is arranged at the OLT of CO end, and is as shown in Figure 8, comprising:
" 1 " sign indicating number inserts the unit, is used for evenly inserting " 1 " sign indicating number at downlink data, and the interval of " 1 " sign indicating number that inserts must be less than a bit length of dpsk signal.The method of inserting " 1 " sign indicating number is to realize through the coding of electricity at the OLT end, promptly in the circuit code sequence of downlink data, evenly inserts " 1 " sign indicating number, and then is transferred to said downstream signal generation device.
The downstream signal generation device is used for the downlink data behind said even insertion " 1 " sign indicating number is carried out the ASK modulation, is evenly inserted the descending ASK signal of " 1 " sign indicating number; This device can adopt the scheme of existing various generation ASK modulation, and for example laser adds Mach-Zehnder ear modulator mode, produces light source input Mach-Zehnder ear modulator by laser, produces the ASK signal by the downlink data driven modulator then;
The upward signal receiving system is used for the up dpsk signal of demodulate reception, and concrete method of reseptance repeats no more with described in the embodiment one here.
The descending ASK signal that ASK/DPSK hybrid modulation device sends and the up dpsk signal of reception separate through circulator; Said descending ASK signal is input to transmission link through said circulator, and the up dpsk signal in the transmission link also gets into said upward signal receiving system through this circulator simultaneously.Said circulator also plays the effect of isolation, can effectively avoid the phase mutual interference of ASK, dpsk signal in downstream signal generation device and the upward signal receiving system.
The said device of present embodiment can also be applied in the Access Network; For example in WDM-PON or the time division multiplexing EPON TDM-PON Access Networks such as (Time Division Multi plexing Passive OpticalNetwork), its system construction drawing that is applied to behind the Access Network is as shown in Figure 9.It comprises CO and ONU, and said CO adopts the ASK/DPSK hybrid modulation method, in downlink data, evenly inserts " 1 " sign indicating number; And carry out the ASK modulation, and the descending ASK signal that is evenly inserted " 1 " sign indicating number sends, and " 1 " code interval of being inserted is less than a bit length of up dpsk signal; With in different wave length channel multiplexing to the SMF transmission link, arrive remote node (RN by array waveguide grating (AWG, Array Waveguide Grating); Remote Node) locates,, be redistributed to each ONU user side by the AWG demultiplexing; Said ONU is divided into two-way with the descending ASK signal behind said even insertion " 1 " sign indicating number, and one the tunnel directly receives said descending ASK signal, the up dpsk signal of another road modulation generation; Then being connected into former link through circulator returns CO, at the CO end up dpsk signal is carried out demodulate reception at last.Saidly at CO end descending ASK signal is carried out the operation that " 1 yard insertion " be encoded and modulated into the ASK form and up dpsk signal carried out demodulate reception and accomplish by the foregoing description two described ASK/DPSK hybrid modulation devices.The main effect of said AWG is the multiplexing and demultiplexing of wavelength, promptly uses the optical multiplexed signal of different wave length channel among the SMF, and the wavelength optical signals demultiplexing that transmits among the SMF is assigned to corresponding wavelength channel.Be respectively arranged with circulator at CO and ONU end, be used for said descending ASK signal and said up dpsk signal are separated, avoid said descending ASK signal and the mutual interference of said up dpsk signal phase.
In Access Network is used, must consider the influence of Rayleigh scattering and stimulated Brillouin scattering to system transmissions.After Figure 10 and Figure 11 have shown the ASK/DPSK mixed-modulation scheme that under different condition, adopts " 1 yard insertion " of the present invention, the relation between up dpsk signal and descending ASK signal receiving sensitivity and the launched power.Obviously, along with the raising of launched power, the system injury that back scattering causes increases.Main backward scattered limiting factor to the uplink and downlink signal is a stimulated Brillouin scattering.Rayleigh scattering can be brought the Power penalty of about 0.5dB, and this is complete acceptable in the art; When launched power surpassed 10dBm, stimulated Brillouin scattering can be brought deterioration to transmission system, cause that receiver sensitivity worsens, and stimulated Brillouin scattering can not show when launched power is less than 10dBm.We can draw the ASK/DPSK compound modulation that the present invention proposes and can not bring excessive system injury because of Rayleigh scattering and stimulated Brillouin scattering in Application in Access Network thus, transmission performance that can safeguards system in the certain power marginal range.
This ASK/DPSK hybrid modulation device based on " 1 yard insertion " coding is applied to have following advantage behind the Access Network:
1) in Access Network, using ASK/DPSK hybrid modulation device can design by simplied system structure, reduces cost, improves bandwidth utilization, adopts novel modulation format can also reduce the influence of nonlinear effect.
2) adopt " 1 yard insertion " coding, suppress the influence that ASK/DPSK hybrid modulation intrinsic signal is crosstalked, solve the limited problem of extinction ratio, improve the service behaviour of system.
In sum, ASK/DPSK hybrid modulation method and device that the embodiment of the invention provides, downstream signal adopt the ASK modulation, and upward signal adopts the DPSK modulation, and adopt " 1 " sign indicating number to insert encoding scheme, have following superiority:
1) descending employing high speed ASK signal is easy to receive, and only needs common PIN detector to get final product, and does not relate to the frequency discrimination and the phase demodulating of FSK and dpsk signal needs; Up employing dpsk signal can be placed on the OLT end to the DPSK demodulation and carry out, and helps centralized control and management.Therefore this ASK/DPSK Hybrid Modulation Technology can design by simplied system structure, reduces cost.
2) after employing " 1 " sign indicating number inserts encoding scheme; Up dpsk signal is separated timing, because two continuous bits are " 1 " sign indicating number before and after the demodulation, the demodulation effect is best; Suppressed the influence that ASK/DPSK hybrid modulation intrinsic signal is crosstalked; And can reduce the influence of nonlinear effect, and extinction ratio also no longer restricts dpsk signal and receive, improved the transmission performance of system greatly.
Can reduce the retardation of MZDI when 3) adopting second kind of demodulation method, shorten the delay arm lengths, improve its job stability.
The above; Be merely the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technical staff who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.
Claims (10)
1. an ASK/DPSK hybrid modulation method is characterized in that, comprising:
Optical line terminal OLT is sent the descending amplitude keying modulation ASK signal that evenly inserts " 1 " sign indicating number and is given optical network unit ONU, and " 1 " code interval of being inserted is less than a bit length of up differential phase keying (DPSK) modulation dpsk signal;
ONU is divided into two-way with the descending ASK signal of said insertion " 1 " sign indicating number, and one the tunnel directly receives said ASK signal, and another road modulation produces up dpsk signal, gets into transmission link and transfers to said OLT;
Said OLT carries out demodulate reception to said up dpsk signal.
2. the method for claim 1 is characterized in that, in the circuit code sequence of downlink data, evenly inserts " 1 " sign indicating number, carries out the ASK modulation again, is evenly inserted the descending ASK signal of " 1 " sign indicating number.
3. the method for claim 1 is characterized in that, the retardation that said OLT carries out demodulate reception to said up dpsk signal equals the interval of said even insertion " 1 " sign indicating number.
4. like claim 1,2 or 3 described methods, it is characterized in that said OLT comprises the method that said up dpsk signal carries out demodulate reception:
If evenly insert m " 1 " sign indicating number in each dpsk signal bit time slots; The m that inserts in then said each dpsk signal bit time slots " 1 " sign indicating number; Be concerned with the m that inserts in next dpsk signal bit time slots " 1 " sign indicating number, obtain m the bit that can represent the current time slots upstream data;
Any reception in m the bit that obtains after selecting at random to be concerned with; Or from m bit after said being concerned with, select the maximum bit of probability to receive.
5. like claim 1,2 or 3 described methods, it is characterized in that said OLT comprises the method that said up dpsk signal carries out demodulate reception:
" 1 " sign indicating number of each insertion is concerned with " 1 " sign indicating number of previous insertion;
Selective reception is positioned at dpsk signal bit time slots edge, and is positioned at " 1 " sign indicating numbers of different dpsk signal bit time slots bit after relevant.
6. an ASK/DPSK hybrid modulation device is characterized in that, comprising:
" 1 " sign indicating number inserts the unit, is used for evenly inserting " 1 " sign indicating number at downlink data, and " 1 " code interval of being inserted is less than a bit length of up differential phase keying (DPSK) modulation dpsk signal;
The downstream signal generation device; Be used for the downlink data of said even insertion " 1 " sign indicating number is carried out amplitude keying modulation ASK; Evenly inserted the descending ASK signal behind " 1 " sign indicating number, so that ONU is divided into two-way with the descending ASK signal of said insertion " 1 " sign indicating number, the one tunnel direct said ASK signal of reception; Another road modulation produces up dpsk signal, gets into transmission link and transfers to the upward signal receiving system;
The upward signal receiving system is used for the up dpsk signal of demodulate reception.
7. device as claimed in claim 6; It is characterized in that; Said downstream signal generation device and upward signal receiving system link to each other with transmission link through circulator, and said downstream signal generation device is input to transmission link with said descending ASK signal through said circulator; Up dpsk signal in the transmission link gets into said upward signal receiving system through said circulator.
8. device as claimed in claim 6 is characterized in that, said device is applied in the Access Network of Wave division multiplexing passive optical network or time division multiplexing EPON.
9. an ASK/DPSK hybrid modulation system is characterized in that, comprising: central office CO and optical network unit ONU,
Said CO evenly inserts " 1 " sign indicating number in downlink data, the line amplitude of going forward side by side keying modulation ASK is evenly inserted the descending ASK signal of " 1 " sign indicating number, and sends said descending ASK signal; " 1 " code interval of being inserted is less than a bit length of up differential phase keying (DPSK) modulation dpsk signal;
Said ONU is divided into two-way with the descending ASK signal of said even insertion " 1 " sign indicating number, and one the tunnel directly receives said descending ASK signal, and another road modulation produces up differential phase keying (DPSK) modulation dpsk signal, and sends said up dpsk signal and give said CO;
Said CO also is used to receive said up dpsk signal.
10. system as claimed in claim 9 is characterized in that, is respectively arranged with circulator at said CO and ONU side, is used for said descending ASK signal and said up dpsk signal are separated, and avoids said descending ASK signal and the mutual interference of said up dpsk signal phase.
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| CN111193544B (en) * | 2020-01-06 | 2022-05-13 | 南京航空航天大学 | Communication method and system based on visible light bidirectional communication system |
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