CN102036134A - OFDM (Orthogonal Frequency Division Multiplexing)-based convergence type OAN (Optical Access Network) system and method - Google Patents
OFDM (Orthogonal Frequency Division Multiplexing)-based convergence type OAN (Optical Access Network) system and method Download PDFInfo
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Abstract
The invention provides OFDM (Orthogonal Frequency Division Multiplexing)-based convergence type OAN (Optical Access Network) system and method. The method comprises the following steps of: generating basic optical carriers by a laser contained in a mode optical line terminal; generating millimeter wave optical carriers and baseband optical carriers by applying a radio-frequency modulation module and an optical inter-difference filter, then, respectively loading OFDM signals, synthesizing and outputting the OFDM signals by utilizing a coupler and transmitting to an optical network unit through an optical distribution network; and separating millimeter wave contents from the received signals by the optical network unit, converting into electric signals, transmitting the electric signals through an antenna group, carrying out the photoelectric conversion, the digital-analog conversion and the treatment to the rest signals and further transmitting to the next unit to realize the convergence access of the wireless signals. The model and the method of the invention are adopted to realize the convergence access of cable signals and wireless signals in the OAN, realize the access in various modes such as baseband OFDM signals, UWB (MB-OFDM) (Ultra Wideband) (Multi-Band-Orthogonal Frequency Division Multiplexing) signals, WiMax/WiFi (Worldwide Interoperability for Microwave Access/Wireless Fidelity) signals and millimeter wave OFDM signals in the same scene and improve the generalization of the access network.
Description
Technical field
Design of communications technology of the present invention, particularly a kind of convergence type optical access network system and method based on OFDM.
Background technology
Along with science and technology development, human society is just being marched toward informationalized epoch.Increasing information data need be propagated by network, and the application of various high flow capacities also emerges, for example IPTV, VoIP, video conference or the like.People are increasing for the demand of message transmission bandwidth always with surprising rapidity.And for Access Network, but still rest on the transmission rate of megabit magnitude, no matter be bandwidth or flexible aspect, all can not satisfy the develop rapidly of current network traffics and user's diversified demand, become a bottleneck in high-speed backbone and the local network.Following broadband access optical-fiber network not only will provide the access way of dynamic flexible for the user, and will improve spectrum efficiency, reduces transmission cost, satisfies the ever-increasing bandwidth demand of user.
At present widely used smooth access technology be the time division multiplexing EPON (Time DivisionMultiplexing-Passive Optical Network, TDM-PON).In this technology, local side apparatus is optical line terminal (Optical Line Terminal, OLT), remote equipment is a plurality of optical network units (Optical Network Unit, ONU), (OpticalDistribution Network ODN) connects the two by the Optical Distribution Network that has no chance.During data downstream, OLT transfers to each ONU with data in the mode of broadcasting by the mode of Time Division Multiplexing, and different ONU give up other data by the data of the own corresponding time slot of agreement acquisition; During data uplink, (by agreement in advance, in difference constantly, each ONU sends separately data respectively to OLT for TimeDivision Multiple Access, TDMA) mode then to adopt time division multiple access.Present commercial TDM-PON technology mainly is to follow the GPON technology of ITU-TG.984 standard, and the EPON technology of following the IEEE802.3ah standard.But the time division multiplexing mode during the TDM-PON up-downgoing has limited the bandwidth of unique user, causes problems such as the not enough and burst reception of band efficiency; Because each optical network unit ONU is different to the distance of optical line terminal OLT, the data that a plurality of ONU equipment send clash on the OLT receiver easily, must introduce ranging technology and burst control technology; Simultaneously, in order to guarantee that OLT can correctly receive the bursty data of ONU, also need to introduce and realize burst light receiving element that quick light detects and the burst clock and data recovery of recovered clock signal (BurstClock and Data Recovery, BCDR) device fast.When expanding more high bandwidth, implement very difficultly based on the burst reception technique of electricity, not only need to increase complicated Bandwidth Management algorithm, and, semiconductor and photoelectron industry have been proposed harsh requirement in clock synchronization, fast aspect the optical signal detecting.These problem restricted T DM-PON further develops, and is difficult to adapt to the evolution of network.
Wave division multiplexing passive optical network (Wavelength Division Multiplexing-PassiveOptical Network, WDM-PON) all distributed an independently wavelength for each ONU, can provide bigger bandwidth for each ONU, each ONU enjoys independently speed, compared to all ONU shared bits speed of TDM-PON, improved the fineness of network greatly.In addition, different ONU information are carried on the different wavelength, have largely increased the fail safe and the integration of network.A fly in the ointment of WDM-PON is that cost is higher, so from moving towards practicality distance is arranged still.
Over the past two years, (Orthogonal Frequency DivisionMultiplexing, the OFDM) appearance of technology was for new vitality had been injected in optical communication to the OFDM in light territory.It is that the OFDM technology in the radio communication is referred on the light that light positive is handed over frequency multiplexing technique, the bit information of high speed serialization is assigned on the overlapped subcarrier of each frequency spectrum dynamically, each subcarrier adopts senior modulation formats such as QAM, the spectrum efficiency of elevator system effectively simultaneously.What is more important, the data-signal duration of light OFDM symbol on each subcarrier increases relatively, add the employing of Cyclic Prefix technology, thereby effectively overcome the intersymbol interference that chromatic dispersion in the optical fiber link and the chromatic dispersion of sheet vibrating diaphragm are brought.In addition, OFDM is a requisite technology in the radio communication.If adopt OFDM form carrying light signal, can realize that optical fiber inserts and the seamless fusion of wireless access.
OFDM can effectively improve the spectrum efficiency of optical access network.Because the orthogonality between each subcarrier of light ofdm signal, it not only allows the frequency spectrum of each subchannel to overlap mutually, and can realize the contour contrast system of xQAM, xPSK on each subcarrier by simple constellation mapping algorithm.Therefore, compare, light OFDM technology is applied in the optical access network can utilizes frequency spectrum resource to greatest extent, promote spectrum efficiency with other modes.
Simultaneously, the resisting chromatic dispersion that light OFDM technology is good makes optical access network to growing apart from the Access Network smooth evolution.Length greater than 80 kms is nearly 2 a years research focus apart from Access Network, is that the metropolitan area Access Network inserts the product that merges mutually with EPON, and it can effectively simplify network configuration, promotes network performance, reduces network cost.Insert for long distance, link dispersion is to the primary beyond doubt problem that solves of the influence of system.And theoretically, the light ofdm signal is not subjected to the chromatic dispersion in the link and the influence of polarization mode dispersion fully.Can realize that optical access network is to long seamlessly transitting apart from Access Network so adopt OFDM to insert.
As everyone knows, Optical Access Network has huge bandwidth potential and good QoS performance, but does not possess mobility, can't satisfy the diversified demand of user terminal; Wireless access network has higher flexibility ratio and mobility, but the QoS poor-performing.OFDM is widely used in WiMax/WiFi and UWB (Ultra-Wide Band, the ultra broadband) framework as the mature technology in the radio communication.If the two fusion, by appropriate design, integrate both advantages, may realize both having had the good QoS of Optical Access Network, can transmit the integrated system of millimeter-wave signal again.
In order to realize this imagination, we have designed the convergence type optical access network system based on OFDM.This system just is based on the basis of OFDM Optical Access Network, the integrated radio-frequency module of millimeter wave frequency band, method by the radio frequency cutting, and make use up between difference multiplexer (Inter Leaver, IL), in a system, produce millimeter wave light carrier and fundamental frequency light carrier simultaneously, be coupled as the single channel mixed signal after the modulation respectively, between optical line terminal and optical network unit, form mixed signal stream, grow Distance Transmission by optical fiber.Reusing between light the difference multiplexer at far-end at last separates with wireless signal wired.So just realize the access of converging of wire signal and wireless signal.
Fig. 1 is common millimeter wave transmission system.Now, common millimeter wave transmission system is described in conjunction with Fig. 1, specific as follows:
LASER Light Source 10 is used for producing millimeter wave at the needed light carrier of optical fiber transmission; Millimeter wave electricity territory signal source 11 produces the electric territory signal of the millimeter wave that has modulated; Light carrier and millimeter wave electricity territory signal are all imported into MZ modulator 12; MZ modulator 12 is divided into two bundles with the light carrier that receives and propagates on two waveguide arms in modulator respectively, utilize the information in the signal of millimeter wave electricity territory to change the modulation voltage of two waveguide arms in the modulator then to change the refractive index of waveguide, change close down phase difference between the two-beam of output of two ripples, the millimeter glistening light of waves that output has mixed up carries signal.
Light carries signal and is set out by local side, grows the transmission of distance by optical fiber, transfers to the high-speed photodetector 13 of millimeter-wave signal transmitting terminal.
The millimeter glistening light of waves that high-speed photodetector 13 will receive carries signal and carries out opto-electronic conversion, is reduced into millimeter wave electricity territory signal, imports Anneta module 14 into; Anneta module 14 is launched millimeter wave electricity territory signal by antenna.
Fig. 2 is common OFDM optical access network system.Now in conjunction with Fig. 2, the structure of common OFDM optical access network system is described, specific as follows:
Common OFDM access network system comprises: optical line terminal, Optical Distribution Network, a L optical network unit.L is greater than or equal to 1 integer.
Optical Distribution Network 21 is assigned to the ofdm signal of light local side output in L the optical network unit 22 of far-end.Wherein, L is the integer more than or equal to 1.
Above-mentioned common millimeter wave transmission system and common OFDM insert optical network system and have finished the long Distance Transmission of millimeter wave in fibre system and the transfer of data of light OFDM form respectively.But when two kinds of systems need use on same circuit, then must set up two cover systems, transmit light respectively and carry millimeter wave and light OFDM formatted data, the complexity that this had both increased the system synthesis management has also increased fund costs such as optical fibre installation, the device space.In order to make full use of the transmission bandwidth potentiality of optical fiber, two Optical Fiber Transmission are fused to the single fiber transmission can overcome above-mentioned weakness.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of convergence type optical access network system based on OFDM, this system can be implemented in the Same Scene, multiple modes such as baseband OFDM signal, UWB (MB-OFDM) signal, WiMax/WiFi signal and millimeter wave ofdm signal insert, and increase the universality of Access Network.
Another object of the present invention is to provide a kind of convergence type optical access network method based on OFDM, this method can be implemented in the Same Scene, multiple modes such as baseband OFDM signal, UWB (MB-OFDM) signal, WiMax/WiFi signal and millimeter wave ofdm signal insert, and increase the universality of Access Network.
In order to achieve the above object, technical scheme of the present invention is such:
Should comprise three parts based on the convergence type optical access network system of OFDM: optical line terminal, Optical Distribution Network, a N optical network unit.
Produce the light source light wave by the LASER Light Source in the optical line terminal, after of the radio frequency cutting of MZ modulator, form the multicarrier of a plurality of frequency contents with radiofrequency signal; Multicarrier is differed from multiplexer subsequently by frequency separation between light, obtain independently base band light carrier and millimeter wave light carrier two paths of signals, need the ofdm signal by millimeter wave and baseband transmission respectively in the modulation, be coupled by coupler then, the acquisition mixed signal also sends.
Mixed signal after optical line terminal will be coupled is transferred to N optical network unit; Wherein N is the integer more than or equal to 1.
In optical network unit one side, multiplexer carries signal according to different frequency with the millimeter glistening light of waves and base band light carries Signal Separation by differing between light again; The millimeter glistening light of waves carries that signal is converted into the signal of telecommunication and via antenna transmission; Base band light carries signal and is converted into the signal of telecommunication, and the entering signal processing unit is handled then, isolates WiMax/WiFi signal, UWB signal, base band data etc., again with it by antenna emission or be transferred to next step application.
Innovation part of the present invention the access net system that provided and method is provided plurality of access modes such as UWB, millimeter wave, WiMax/WiFi, base band are converged is one, the unified OFDM technology beared information that adopts on the physical layer, plurality of access modes is discerned, survey and handle, realize that the seamless light that converges inserts.
As seen from the above technical solutions, the invention provides a kind of convergence type optical access network system and method based on OFDM.The advantage of scheme is again, and being used in combination of difference multiplexer and rf modulations module between the light in the optical line terminal makes the millimeter glistening light of waves carry the generation that signal and base band light carries signal and be positioned on the same optical line terminal, is convenient to the buying and the installation administration of equipment; Only need a LASER Light Source at local side, reduce equipment cost; Millimeter-wave signal and light ofdm signal be by the transmission of same Optical Distribution Network, saved the material of optical fiber wiring and manpower equipment, cost, simplified the complexity of Optical Distribution Network; Improved the band efficiency of fibre system; Add difference multiplexer between light inlet at the light allocation units of far-end, two systems that realize integrated at far-end, the installation of being convenient to system is disposed; Select plurality of access modes such as baseband OFDM signal, UWB signal, WiMax/WiFi signal and millimeter wave ofdm signal at different scenes flexibly, satisfied the diversified demand of optical access network terminal, and increased the universality of Access Network largely.
Description of drawings
The common millimeter wave transmission system of Fig. 1.
The common OFDM optical access network system of Fig. 2.
Fig. 3 is the structural representation that the present invention is based on the convergence type optical access network system of OFDM.
Fig. 4 is the structural representation of OFDM module in the system of the present invention.
Fig. 5 is the flow chart that the present invention is based on the convergence type optical access network method of OFDM.
Embodiment
For make purpose of the present invention, technical scheme, and advantage clearer, below with reference to the accompanying drawing embodiment that develops simultaneously, the present invention is described in more detail.
The invention provides a kind of convergence type optical access network system and method based on OFDM, the laser that this mould optical line terminal comprises produces basic light carrier, the difference filter generates millimeter wave light carrier and base band light carrier between utilization rf modulations module and light, load ofdm signal subsequently respectively, utilize coupler with its synthetic output, transfer to optical network unit by Optical Distribution Network; Optical network unit goes out the millimeter wave composition with the Signal Separation that receives, and launches by antenna sets, and remaining signal carries out digital-to-analogue conversion and signal processing, further is transferred to the next stage unit, thereby realizes the access of converging of wireless signal.
Fig. 3 is the structural representation that the present invention is based on the convergence type optical access network system of OFDM; Fig. 4 is the structural representation of OFDM module in the system of the present invention.Now in conjunction with Fig. 3 and Fig. 4, the structure of the convergence type optical access network system that the present invention is based on OFDM is described, specific as follows:
For sake of clarity, earlier the convergence type optical access network system that the present invention is based on OFDM is defined, access net system of the present invention can produce that a millimeter glistening light of waves carries signal and base band light carries signal simultaneously at optical line terminal, and rationally mix, transfer to optical line terminal by Optical Distribution Network, isolate a millimeter glistening light of waves and carry signal in terminal, and launch by antenna, base band light carries signal and then enters correlation module and carry out digital processing; The present invention's OFDM module shown in Figure 4 can realize the OFDM code conversion of data flow, by steps such as IFFT conversion, digital-to-analogue conversions, exports data to the MZ modulator at last, is used for light carrier is modulated.
The convergence type optical access network system that the present invention is based on OFDM comprises: optical line terminal 30, Optical Distribution Network 31 and N optical network unit 32.
Wherein, optical line terminal 30 comprises difference multiplexer 303 and coupler 408 between 300,2 OFDM modulation modules of LASER Light Source (Fig. 3 is not shown), 1 rf modulations module (Fig. 3 is not shown), light.
LASER Light Source 300 in the optical line terminal 30 and the signal between the rf modulations module are the light source light wave, are the light carrier primary light sources of whole system; Produce the radiofrequency signal of millimere-wave band in the rf modulations module, subsequently with this signal by in the MZ modulator 301 the light source light wave being carried out radio frequency cutting, the multi-carrier signal that formation has a plurality of frequency contents; After difference multiplexer 303 received multi-carrier signal between light, it carries out frequency separation handled, and produces millimeter wave light carrier and base band light carrier two paths of signals; The frequency of described base band light carrier has identical light frequency with the light source light wave; Wherein the frequency of base band light carrier has identical light frequency with the light source light wave, and the millimeter wave light carrier is the signal with two frequencies, and the difference of two frequencies is exactly the frequency values of millimeter wave carrier, and these two frequencies are symmetrically distributed in the both sides of base band optical carrier frequency; One of OFDM modulation module (being made up of MZ modulator 304 and OFDM module 305) carries out OFDM to the data of millimeter wave data source to be handled, generation need be by the ofdm signal of millimeter wave transmission, this signal is loaded on the millimeter wave light carrier in the MZ modulator subsequently, and the millimeter glistening light of waves that forms required transmission carries signal; Two (being made up of MZ modulator 306 and OFDM module 307) of OFDM modulation module the data of an other data source being carried out OFDM handles, the needs that produce are by the ofdm signal of light baseband transmission, this signal subsequently in the MZ modulator north be loaded on the base band light carrier, form the required base band light of transmission and carry signal; Coupler 308 carries signal and base band light with the millimeter glistening light of waves and carries signal two-way independent light signal and be coupled, and forms the nonoverlapping mixed signal of frequency, and exports it to link fiber, is linked into Optical Distribution Network 31.
Optical Distribution Network 31 receives the signal of the optical line terminal that is positioned at local side, and passes to N the optical network unit 32 that is positioned at far-end; Optical Distribution Network 31 is limiting structure not, and its structure can be star-like, bus-type, annular, existing structure such as point-to-point, also can be the following new construction that occurs.Present invention focuses on the convergence type optical access network system and the method based on OFDM of optical line terminal 30 and optical network unit 32; The structure of N optical network unit 32 is identical; N is the positive integer more than or equal to 1.
After difference filter 320 receives the mixed signal that Optical Distribution Network 31 transmits between light, by signal being carried out the staggered separation of frequency, obtain independently that a millimeter glistening light of waves carries signal with base band light carries signal, common two-way; One of high-speed photodetector 321 carries conversion of signals with the millimeter glistening light of waves and becomes millimeter wave electricity territory signal; Millimeter wave electricity territory signal is handled by Anneta module 322, and carries out wireless transmission by one of antenna 323; Two of high-speed photodetector 324 converts isolated base band optical carrier to base band electricity territory signal; A/D converter 325 becomes digital signal with base band electricity territory conversion of signals; 326 pairs of digital signals of signal processing unit are handled, and isolate WiMax/WiFi signal, UWB signal, base band data; 2 327 of antenna sends the WiMax/WiFi signal; 3 328 of antenna sends the UWB signal; Base band data is output for other application.
Wherein, two OFDM modulation modules respectively comprise a MZ modulator and an OFDM module.The rf modulations module comprises MZ modulator 301 and radio-frequency signal generator 302.Wherein, MZ modulator 304 and OFDM module 305 are formed one of OFDM modulation module, finish the modulation that millimeter glistening light of waves carries signal; MZ modulator 306 and OFDM module 307 are formed two of OFDM modulation module, finish the modulation that base band light carries signal.
The MZ modulator is divided into two bundles with the light carrier that receives and propagates on two waveguide arms in modulator respectively, utilize the information that contains in photoelectric effect and the traffic spike to change the modulation voltage of two waveguide arms in the modulator then to change the refractive index of waveguide, change close down phase difference between the two-beam of output of two ripples, the signal that output has mixed up.If the MZ modulator is positioned at the OFDM modulation module, then flows of data signals refers to ofdm signal, and output signal carries signal for the millimeter glistening light of waves or base band light carries signal; If the MZ modulator is positioned at the rf modulations module, then flows of data signals refers to the millimeter-wave frequency carrier signal that radio-frequency signal generator produces, and output signal is a multi-carrier signal.
Radio-frequency signal generator produces the sine wave in an electric territory, and this sine wave is used as the carrier wave of millimeter-wave signal.Therefore, the frequency of sinusoidal signal should be a millimeter scope to satisfy wavelength at 30GHz-300GHz.
The structure of OFDM module comprises as shown in Figure 4 with lower member: data source 40, serial to parallel conversion module 41, digital signal processing module 42, parallel serial conversion module 43, two D/A converter modules 44 and software up-conversion modules 45.
Data source 40 produces the signal that needs transmission;
Serial to parallel conversion module 41 is converted to the M channel parallel data with one tunnel serial data;
Digital signal processing module 42 carries out inverse fast fourier transform (IFFT) with M road serial signal, promptly the M circuit-switched data is modulated on the different orthogonal sub-carriers; In the ofdm signal that forms, add Cyclic Prefix subsequently, expand the intersymbol interference that causes in order to the multidiameter delay that overcomes channel; Add training sequence, as receiving terminal do regularly synchronously, channel estimating and frequency offset estimating etc.;
Serial-parallel converter 43 transfers M road parallel signal to two ways of digital signals;
D/A switch module 44 converts two ways of digital signals to the two-way analog signal;
Software up-conversion module 45 merges the two-way analog signal handles the output OFDM signal.
Fig. 5 is the flow chart that the present invention is based on the convergence type optical access network method of OFDM.Now in conjunction with Fig. 5, the convergence type optical access network method that the present invention is based on OFDM is described, specific as follows, step comprises:
Step 501: utilize LASER Light Source to produce the light source light wave; Subsequently in the rf modulations module, produce the radiofrequency signal of millimeter wave frequency band, and with this signal loading to described light source light wave, by the radio frequency cutting, form the described multi-carrier signal that contains a plurality of frequency contents; Multi-carrier signal contains the main carrier frequency of LASER Light Source, and monosymmetric two sideband carrier frequencies, and two sideband frequency-splittings are the millimeter wave carrier frequency; Multicarrier is carried out frequency separation handle, the difference multiplexer obtains millimeter wave light carrier and base band light carrier 2 tunnel independent light signals respectively with the LASER Light Source frequency content and the sideband frequency component separation of multi-carrier signal between promptly using up; The millimeter wave light carrier is loaded need be become a millimeter glistening light of waves and carry signal by the wireless OFDM signal of millimeter wave transmission; Base band light carrier two paths of signals all is loaded the ofdm signal that needs by the base band optical signal transmission, becomes base band light and carries signal; The millimeter glistening light of waves carries signal and described base band light and carries signal and be coupled device subsequently and be coupled as one tunnel mixed signal of separating on the frequency, the incoming fiber optic link, and export Optical Distribution Network to;
Wherein, radiofrequency signal is the electrical signal of the frequency of millimeter wave, i.e. the signal of telecommunication of 30GHz-300GHz; Described millimeter wave light carrier up and down two harmonic frequency difference correspondences millimeter-wave frequency; The base band optical carrier frequency is identical with the light source light wave frequency;
In this step, the method that produces millimeter wave light carrier and base band light carrier two paths of signals comprises:
Step 5011, the light source light wave that LASER Light Source is produced transfers to MZ modulator carrier wave input, and as the primary light source of whole system, its frequency is called centre frequency; And the radio signal transmission that radio-frequency signal generator is produced is to the modulation signal end of MZ modulator; The frequency of radiofrequency signal is in and is millimere-wave band, and scope is 30GHz-300GHz;
Step 5012 is carried out the carrier wave cutting with radiofrequency signal to the light source light wave in the MZ modulator, form the multi-carrier signal that contains a plurality of frequency contents, comprises a centre frequency carrier wave identical with the light source light wave frequency in this carrier signal, and two sideband carriers; The amplitude of two sideband carriers equates; The frequency-splitting of sideband carrier is the frequency of radiofrequency signal; Two sideband carrier frequencies are symmetry with the centre frequency carrier wave;
Step 5013, adopt between light the difference multiplexer to handle multi-carrier signal,, the centre frequency carrier and sideband carrier wave in the multicarrier separated entering in the two-way optical fiber respectively by frequency separation, forming the two independent light carrier, is respectively millimeter wave light carrier and base band light carrier.
Millimeter wave light carrier and base band light carrier are added ofdm signal, and form the implementation method of mixed signal, comprise following steps:
Step 5014 is transmitted the millimeter wave light carrier MZ modulator carrier wave incoming end that enters an OFDM modulation module; The OFDM module will need to be treated to ofdm signal by the data source data of millimeter wave transmission, and will need to insert the MZ modulator signal end that links to each other with the millimeter wave light carrier by the ofdm signal of millimeter wave transmission;
Step 5015, the MZ modulator is loaded on ofdm signal on the millimeter wave light carrier in the amplitude modulation(PAM) mode by voltage control phase delay effect subsequently, forms the millimeter glistening light of waves and carries signal;
Step 5016, the base band light carrier is imported into the MZ modulator carrier wave incoming end of another OFDM modulation module, the OFDM module will need to be treated to ofdm signal by another data source data of light baseband transmission, and will need to insert MZ modulator signal end therewith by the ofdm signal of this light carrier transmission;
Step 5017, the MZ modulator is loaded on ofdm signal on the base band light carrier in the amplitude modulation(PAM) mode by voltage control phase delay effect subsequently, forms base band light and carries signal;
Step 5018 is utilized coupler, with in the two-way optical fiber independently the millimeter glistening light of waves of different frequency composition carry signal and base band light and carry signal and be coupled in the optical link, form nonoverlapping mixed signal on the frequency; The mixed signal that will have data subsequently exports Optical Distribution Network to, grows the Access Network transmission of distance.
Step 502 is utilized Optical Distribution Network, and the mixed signal that will be positioned at the optical line terminal output of local side is distributed to N the optical network unit that is positioned at far-end.
Optical Distribution Network in this step, limiting structure not, its structure can be star-like, bus-type, annular, existing structure such as point-to-point, also can be the following new construction that occurs.Present invention focuses on the convergence type optical access network system and the method based on OFDM of optical line terminal and optical network unit.Wherein, N is the positive integer more than or equal to 1.
Wherein, millimeter wave is by this access net system, and the step of separating, sending at optical network unit is as follows:
Step 5031, the mixed signal that receives is inserted difference multiplexer (IL) between light,, handle in the mode that is similar to the A3 step by the separation on the frequency, an acquisition millimeter glistening light of waves carries signal and base band light carries signal two independent light signal, inserts the two-way optical fiber link respectively;
Step 5032, the millimeter glistening light of waves carries signal and is imported into high-speed photodetector, finishes opto-electronic conversion by photoelectric effect, forms millimeter wave electricity territory signal, so that carry out the signal emission by antenna;
Step 5033, millimeter wave electricity territory signal is imported into Anneta module to be handled, and goes out by antenna transmission then.
Base band light carries the separation of signal and handles as following steps:
Step 5034, base band light are carried signal and are imported into high-speed photodetector, finish opto-electronic conversion by photoelectric effect, generate electric territory signal, so that signal is carried out the processing in electric territory;
Step 5035, the signal of telecommunication that previous step is generated inserts A/D converter, makes analog signal conversion become digital signal, accesses to signal processing unit;
Step 5036, the digital signal input signal processing unit processes of generation is at first carried out fast Fourier transform (FFT), recovers the data source data of back acquisition at optical line terminal; According to processing such as separating of various objectives general signal wherein, then obtain WiMax/WiFi signal, UWB signal and base band data then; WiMax/WiFi signal wherein and UWB signal are sent into two antennas respectively, go out by wireless transmission.The light that base band data has then been finished long distance inserts transmitting of task, further is transferred to other equipment and uses.
The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being made, is equal to replacement, improvement etc., all should be included within the scope of protection of the invention.
Claims (7)
1. the convergence type optical access network system based on OFDM is characterized in that this system comprises: optical line terminal, Optical Distribution Network, a N optical network unit;
Described optical line terminal comprises difference multiplexer (IL), coupler between 1 LASER Light Source, 1 rf modulations module, 2 OFDM modulation modules, light; Described LASER Light Source produces the light source light wave, is the light carrier primary light source of whole system; In the described rf modulations module, produce the electric territory radiofrequency signal of millimere-wave band in the radio-frequency signal generator, subsequently with this signal by in the MZ modulator light source light wave being carried out radio frequency cutting, the multi-carrier signal that formation has a plurality of frequency contents; After difference multiplexer (IL) is received multi-carrier signal between described light, it is carried out frequency separation handle, produce millimeter wave light carrier and base band light carrier two paths of signals; The frequency of described base band light carrier has identical light frequency with the light source light wave; Described millimeter wave light carrier is the signal with two frequencies, and the difference of two frequencies is exactly the frequency values of millimeter wave carrier, and these two frequencies are symmetrically distributed in the both sides of base band optical carrier frequency; OFDM module in one of described OFDM modulation module is carried out the OFDM conversion process to the data of a data source, generation need be by the ofdm signal of millimeter wave transmission, this signal is loaded in the MZ modulator on the millimeter wave light carrier subsequently, forms the required millimeter glistening light of waves of transmission and carries signal; Described OFDM modulation module two in the OFDM module data of an other data source are carried out the OFDM conversion process, the needs that produce are by the ofdm signal of light baseband transmission, this signal subsequently in the MZ modulator north be loaded on the base band light carrier, form the required base band light of transmission and carry signal; Described coupler carries signal and base band light with the millimeter glistening light of waves and carries signal two-way independent light signal and be coupled, and forms the nonoverlapping mixed signal of frequency, and exports it to link fiber, is linked into described Optical Distribution Network;
Described Optical Distribution Network receives the mixed signal of described optical line terminal output, and passes to N described optical network unit, and the structure of a described N optical network unit is identical; Wherein, N is the integer more than or equal to 1;
Described optical network unit comprises difference filter, 2 high-speed photodetectors, 1 Anneta module, 3 antennas, 1 A/D converter between 1 light, 1 signal processing unit in each unit; After the difference filter is received the mixed signal that Optical Distribution Network transmits between described light, by signal being carried out the staggered separation of frequency, obtain independently that a millimeter glistening light of waves carries signal with base band light carries signal, common two-way; One of described high-speed photodetector carries conversion of signals with the millimeter glistening light of waves and becomes millimeter wave electricity territory signal; Described millimeter wave electricity territory signal is handled by described Anneta module, and carries out wireless transmission by one of described antenna; Two of described high-speed photodetector converts isolated base band optical carrier to base band electricity territory signal; Described A/D converter becomes digital signal with base band electricity territory conversion of signals; Described signal processing unit carries out fast Fourier transform (FFT) to digital signal, and WiMax/WiFi signal, UWB signal, base band data are distinguished and exported to the purpose that has more data flow; Two of described antenna sends the WiMax/WiFi signal wireless; Three of described antenna sends the UWB signal wireless; Described base band data is output for other application.
2. system according to claim 1 is characterized in that, described OFDM modulation module comprises: 1 OFDM module and 1 MZ modulator (Mach-Zehnder modulators);
Described OFDM module comprises data source, initial data is carried out the OFDM (OFDM) in electric territory and handles, and electric territory OFDM data-signal is provided;
Described MZ modulator is divided into two bundles with the light carrier that receives and propagates on two waveguide arms in modulator respectively, utilize the information in the ofdm signal of described electric territory to change the modulation voltage of two waveguide arms in the modulator then to change the refractive index of waveguide, change close down phase difference between the two-beam of output of two ripples, the light that output has mixed up carries signal; In this patent, the light carrier of described MZ modulator correspondence is described base band light carrier, described millimeter wave light carrier, and this two output that loads by ofdm signal is respectively that described base band light carries signal, the described millimeter glistening light of waves carries signal.
3. system according to claim 1 is characterized in that, described rf modulations module comprises: a radio-frequency signal generator and a MZ modulator;
Described radio-frequency signal generator, the electric territory CF signal of generation millimeter wave frequency band, frequency range are by 30GHz-300GHz, and this radiofrequency signal is used for forming light territory millimeter wave carrier frequency;
Described MZ modulator is divided into two bundles with the light source light ripple that receives and propagates on two waveguide arms in modulator respectively, utilize described millimeter-wave frequency electricity territory CF signal to change the modulation voltage of two waveguide arms in the modulator then to change the refractive index of waveguide, change close down phase difference between the two-beam of output of two ripples, output contains the multicarrier of a plurality of frequency contents, promptly finishes the light source light wave is carried out the radio frequency cutting.
4. system according to claim 2 is characterized in that, described OFDM module comprises: data source, serial to parallel conversion module, digital signal processing module, parallel serial conversion module, two D/A converter modules and software up-conversion module;
Described data source produces the signal that needs transmission;
Described serial to parallel conversion module is converted to the M channel parallel data with one road serial data stream, forms multiple signals, exports digital signal processing module to;
Described digital signal processing module carries out inverse fast fourier transform (IFFT) with M road serial signal, promptly the M circuit-switched data is modulated on the different orthogonal sub-carriers; In the ofdm signal that forms, add Cyclic Prefix subsequently, expand the intersymbol interference that causes in order to the multidiameter delay that overcomes channel; Add training sequence, as receiving terminal do regularly synchronously, channel estimating and frequency offset estimating etc.;
Described serial-parallel converter transfers M road parallel digital signal to two ways of digital signals;
Described D/A converter module converts two ways of digital signals to the two-way analog signal;
Described software up-conversion module merges the two-way analog signal to be handled, and output OFDM signal to MZ modulator is modulated.
5. convergence type optical access network method based on OFDM is characterized in that this method comprises:
A, utilize LASER Light Source to produce the light source light wave; Subsequently in the rf modulations module, produce the radiofrequency signal of millimeter wave frequency band, and with this signal loading to described light source light wave, by the radio frequency cutting, form the described multi-carrier signal that contains a plurality of frequency contents; Described multi-carrier signal contains the main carrier frequency of LASER Light Source, and monosymmetric two sideband carrier frequencies, and two sideband frequency-splittings are the millimeter wave carrier frequency; Described multicarrier is carried out frequency separation handle, the difference multiplexer obtains millimeter wave light carrier and base band light carrier 2 tunnel independent light signals respectively with the LASER Light Source frequency content and the sideband frequency component separation of multi-carrier signal between promptly using up; Described millimeter wave light carrier is loaded need be become a millimeter glistening light of waves and carry signal by the wireless OFDM signal of millimeter wave transmission; Described base band light carrier two paths of signals all is loaded the ofdm signal that needs by the base band optical signal transmission, becomes base band light and carries signal; The described millimeter glistening light of waves carries signal and described base band light and carries signal and be coupled device subsequently and be coupled as one tunnel mixed signal of separating on the frequency, the incoming fiber optic link, and export Optical Distribution Network to; Described radiofrequency signal is the electrical signal of the frequency of millimeter wave, i.e. the signal of telecommunication of 30GHz-300GHz; Described millimeter wave light carrier up and down two harmonic frequency difference correspondences millimeter-wave frequency; Described base band optical carrier frequency is identical with the light source light wave frequency;
B, utilize Optical Distribution Network, the mixed signal that will be positioned at the optical line terminal output of local side is distributed to N the optical network unit that is positioned at far-end; N is the integer more than or equal to 1;
C, use up between the difference multiplexer mixed signal that receives is carried out frequency separation, light source frequency composition in the described mixed signal and sideband frequency composition are divided to the two-way link, and become respectively that a millimeter glistening light of waves carries signal and base band light carries signal; The described millimeter glistening light of waves carries signal delivers to the antenna emission, and the wireless signal that sends this moment still contains the carrier wave of two frequencies, and the carrier wave difference frequency still is the millimeter-wave signal carrier frequency; Described base band light is carried signal carry out digital processing, separate obtaining WiMax/WiFi signal, UWB signal and base band data; Described WiMax/WiFi signal and UWB signal are sent into the antenna emission respectively; Base band data will be transferred to other application.
6. method according to claim 5 is characterized in that, steps A is described to be produced the millimeter glistening light of waves and carry the mixed signal that signal and base band light carries signal and comprise:
A1, the light source light wave that LASER Light Source is produced transfer to MZ modulator carrier wave input, and as the primary light source of whole system, its frequency is called centre frequency; And the radio signal transmission that radio-frequency signal generator is produced is to the modulation signal end of MZ modulator; The frequency of radiofrequency signal is in and is millimere-wave band, and scope is 30GHz-300GHz;
A2, in the MZ modulator, the light source light wave is carried out carrier wave cutting, form the multi-carrier signal that contains a plurality of frequency contents, comprise a centre frequency carrier wave identical in this carrier signal with the light source light wave frequency with radiofrequency signal, and two sideband carriers; The amplitude of two sideband carriers equates; The frequency-splitting of sideband carrier is the frequency of radiofrequency signal; Two sideband carrier frequencies are symmetry with the centre frequency carrier wave;
A3, adopting between light the difference multiplexer to handle multi-carrier signal, by frequency separation, the centre frequency carrier and sideband carrier wave in the multicarrier separated entering in the two-way optical fiber respectively, form the two independent light carrier, is respectively millimeter wave light carrier and base band light carrier;
A4, millimeter wave light carrier transmission entered the MZ modulator carrier wave incoming end of an OFDM modulation module; The OFDM module will need to be treated to ofdm signal by the data source data of millimeter wave transmission, and will need to insert the MZ modulator signal end that links to each other with the millimeter wave light carrier by the ofdm signal of millimeter wave transmission;
A5, the MZ modulator is loaded on ofdm signal on the millimeter wave light carrier in the amplitude modulation(PAM) mode by voltage control phase delay effect subsequently, forms a millimeter glistening light of waves and carries signal;
A6, the base band light carrier imported into the MZ modulator carrier wave incoming end of another OFDM modulation module, the OFDM module will need to be treated to ofdm signal by another data source data of light baseband transmission, and will need to insert MZ modulator signal end therewith by the ofdm signal of this light carrier transmission;
A7, the MZ modulator is loaded on ofdm signal on the base band light carrier in the amplitude modulation(PAM) mode by voltage control phase delay effect subsequently, forms base band light and carries signal;
A8, utilize coupler, with in the two-way optical fiber independently the millimeter glistening light of waves of different frequency composition carry signal and base band light and carry signal and be coupled in the optical link, form nonoverlapping mixed signal on the frequency; The mixed signal that will have data subsequently exports Optical Distribution Network to, grows the Access Network transmission of distance.
7. method according to claim 5 is characterized in that, the described separating mixture of source signals of step C, and the method for isolated millimeter wave light carrier and base band light carrier being handled transmission respectively comprises:
C1, the mixed signal that receives is inserted difference multiplexer (IL) between light,, handle, obtain that a millimeter glistening light of waves carries signal and base band light carries signal two independent light signal, insert the two-way optical fiber link respectively in the mode that is similar to the A3 step by the separation on the frequency;
C2, the millimeter glistening light of waves carry signal and are imported into high-speed photodetector, finish opto-electronic conversion by photoelectric effect, form millimeter wave electricity territory signal, so that carry out the signal emission by antenna;
C3, millimeter wave electricity territory signal are imported into Anneta module to be handled, and goes out by antenna transmission then.
Base band light carries the separation of signal and handles as following steps:
C4, base band light carry signal and are imported into high-speed photodetector, finish opto-electronic conversion by photoelectric effect, generate electric territory signal, so that signal is carried out the processing in electric territory;
C5, the signal of telecommunication that previous step is generated insert A/D converter, make analog signal conversion become digital signal, access to signal processing unit;
The digital signal input signal processing unit processes of C6, generation is at first carried out fast Fourier transform (FFT), recovers the data source data of back acquisition at optical line terminal; According to processing such as separating of various objectives general signal wherein, then obtain WiMax/WiFi signal, UWB signal and base band data then; WiMax/WiFi signal wherein and UWB signal are sent into two antennas respectively, go out by wireless transmission; The light that base band data has then been finished long distance inserts transmitting of task, further is transferred to other equipment and uses.
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Application publication date: 20110427 |