CN108718213B - Full duplex wired and wireless hybrid optical access system and method based on polarization multiplexing - Google Patents

Full duplex wired and wireless hybrid optical access system and method based on polarization multiplexing Download PDF

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CN108718213B
CN108718213B CN201810810896.8A CN201810810896A CN108718213B CN 108718213 B CN108718213 B CN 108718213B CN 201810810896 A CN201810810896 A CN 201810810896A CN 108718213 B CN108718213 B CN 108718213B
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optical
downlink
signal
uplink
frequency
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CN108718213A (en
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张瑞姣
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North China University of Water Resources and Electric Power
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North China University of Water Resources and Electric Power
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2589—Bidirectional transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/564—Power control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/615—Arrangements affecting the optical part of the receiver
    • H04B10/6151—Arrangements affecting the optical part of the receiver comprising a polarization controller at the receiver's input stage
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q11/0067—Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Electromagnetism (AREA)
  • Signal Processing (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention discloses a full duplex wired and wireless mixed optical access system and a method based on polarization multiplexing, comprising a central station, an optical fiber transmission link between the central station and a mixed ONU, the mixed ONU and a wireless user terminal, wherein the full duplex transmission of downlink and uplink broadband signals is realized, a full duplex optical link is formed, the complexity of the central station is reduced, the frequency spectrum utilization rate is improved, and the long-distance transmission of high-speed broadband signals is realized; the hybrid ONU flexibly and conveniently provides wired or millimeter wave wireless selective access according to different requirements of users, so that the flexibility of the hybrid ONU access mode is improved; the central station reserves the coherent demodulation local oscillation light of the uplink optical signal, simplifies the complexity of the central station and increases the realizability of the full duplex link; the mixed ONU only needs a continuous laser source CWLD2 with fixed output wavelength, heterodyne beat frequency local oscillation light for wireless access of the downlink optical signal and uplink optical carrier wave for wireless access are provided, and the cost of the mixed ONU is reduced.

Description

Full duplex wired and wireless hybrid optical access system and method based on polarization multiplexing
Technical Field
The invention relates to the technical field of optical fiber wired access communication and millimeter wave wireless access communication, in particular to a full-duplex wired and wireless hybrid optical access system and method based on polarization multiplexing.
Background
With the advent of the high-speed informatization era, the continuous emergence of ultra-wideband multimedia new services such as video education, telemedicine, network games, three-dimensional display, ultra-high definition/blue-ray television and the like, and the rapid development of apps such as online shopping, mobile banking, video live broadcasting, palm health, sharing bicycle and cloud service and the like based on a high-speed wireless mobile terminal application platform, the requirement of human society on the transmission bandwidth of an access network is increased at a striking speed, and the severe challenges are presented to the communication capacity of the current wired access network and wireless access network. Meanwhile, with the proposal of the concept of the smart city and the rapid construction of the smart city, people hope to be connected with the broadband ubiquitous network at any time and any place (fixed place: office and the like and mobile place: train running at high speed and the like), so that the dependence of the human society on the network becomes larger and larger, and the requirement on the convenience of a network access mode is higher and higher.
The optical fiber wired access communication uses the optical fiber as a transmission medium, can provide huge bandwidth and realize long-distance transmission of high-speed data information, but because the optical cable is required to be laid, the terminal user is bound by the optical cable, so that the flexibility of a network access mode is severely limited; although the wireless access communication can use free space as transmission medium to provide flexible and convenient network access mode, and meet the requirement of terminal users for diversified access modes, the transmission rate of the narrowband wireless access communication using low-frequency spectrum is far smaller than that of the optical fiber wired access communication at present, and the spectrum resources of the low-frequency spectrum are quite crowded, so that the requirements of communication multimedia services with different daily needs for access network bandwidth and rate can not be met. In order to simultaneously meet the requirements of the human society on the continuously-increased bandwidth and transmission rate of communication multimedia new services and the flexibility of network access modes, the optical fiber wired access communication and the wireless access communication in the next-generation broadband access network play a great role, the advantages of the optical fiber wired access communication and the wireless access communication are complementary, and the optical fiber wired access communication and the wireless access communication are mutually fused into a hybrid optical access network to cooperatively meet the requirements of the human society on the flexible selectivity of the access network broadband, the transmission rate and the access modes. At present, the advent of radio-on-fiber (RoF) technology for generating optical waves carrying radio-frequency signals based on microwave photonics technology makes optical fiber wired access communication and wireless access communication show compatibility in network distribution, namely, both utilize an optical fiber distribution network to transmit optical signals, and the advent of the technology further promotes the fusion of the optical fiber wired access communication and the wireless access communication.
The integrated wired and wireless hybrid optical access network has the advantages of large bandwidth, low loss and long-distance transmission of optical fiber wired access communication and the advantages of ubiquitous wireless access communication and flexible and convenient access mode, can respectively transmit broadband wired access signals based on optical fibers and transmit optical millimeter wave signals based on RoF, and provides broadband wired or wireless selective access for users at access network terminals; the integration of optical fiber wired access communication and wireless access communication is realized in the network layer, so that the network structure of the optical access network can be simplified, the network cost can be reduced, and meanwhile, the requirements of human society on the bandwidth, the transmission rate and the access mode of the communication multimedia new service can be met.
At present, a wired and wireless hybrid optical access network combining a PON-based optical fiber wired access network and a RoF-based wireless access network is widely paid attention to and researched by research institutions at home and abroad. However, there are at least the following problems in the reported PON/RoF based wired/wireless hybrid optical access networks: the method simply superimposes the frequency spectrum bearing the wired access signal light wave and the frequency spectrum bearing the wireless access signal light wave, the wired and wireless access channels are two mutually independent channels, the problems of complex structure, low network fusion degree and network resource waste of the fusion network exist, the services provided by the wired and wireless access are different in the network access terminal, and the problem of immobilization of the access mode exists. The method for deeply fusing the PON-based optical fiber wired access network and the RoF-based wireless access network is provided at present, the network and spectrum structure are simplified, the network cost is reduced, the spectrum utilization rate is improved, the wired or millimeter wave wireless selective access of Gbit/s high-rate data is realized, and full duplex communication is realized, so that the method becomes a key problem to be solved at present.
Disclosure of Invention
In view of the foregoing, it is an object of the present invention to provide a polarization multiplexing-based full duplex wired/wireless hybrid optical access system and method.
The technical scheme for solving the problems is as follows: the full duplex wired and wireless hybrid optical access system based on polarization multiplexing comprises a central station, an uplink optical fiber transmission link and a downlink optical fiber transmission link between the central station and a hybrid ONU, the hybrid ONU and a wireless user terminal; the central station comprises a downlink optical signal transmitting module and an uplink optical signal receiving module, wherein one part of output signals of the downlink optical signal transmitting module are reserved as coherent demodulation local oscillation light of uplink optical signals in the central station, and the other part of the output signals form downlink optical signals which are sent into the hybrid ONU through a downlink optical fiber transmission link; the mixed ONU comprises a polarization beam splitter PBS2, a polarization controller PC3, two optical switches S1 and S2, a downlink wired access module, a downlink wireless signal transmitting module, a wireless access uplink signal receiving module and a wired access uplink optical signal transmitting module, wherein the PBS2 is used for dividing a received downlink optical signal into two paths of optical waves, one path of optical wave is sent to an input port of the S1 through the PC3, and the other path of optical wave is sent to the downlink wired access module; the downlink wireless signal transmitting module comprises a continuous laser CWLD2, a polarization beam splitter PBS3, a polarization controller PC5, an optical coupler OC, a photoelectric detector PD, an electric band-pass filter EBPF and a transmitting antenna which are sequentially connected, wherein the input end of the OC is also connected with a first output port of S1, the output end of the PBS3 is also connected with a wireless access uplink signal receiving module, and the transmitting antenna transmits the output signal of the EBPF to a wireless user terminal; the wireless access uplink signal receiving module comprises a receiving antenna, an output signal of the receiving antenna is sent to a Mach-Zehnder modulator (MZM), the input end of the MZM is also connected with the output end of the PBS3, and the output end of the MZM is connected with a first input port of the S2 through an Optical Band Pass Filter (OBPF); the downlink wired access module comprises a polarization controller PC4, an optical power beam splitter PS2 and an optical coherence receiver OCR2 which are sequentially connected, wherein the input end of the OCR2 is also connected with a second output port of the S1, and the output end of the PS2 is also connected with the wired access uplink optical signal transmitting module; the wired access uplink optical signal transmitting module comprises a second optical I/Q modulator, wherein the input end of the second optical I/Q modulator is connected with the output end of the PS2, and the output end of the second optical I/Q modulator is connected with the second input port of the S2; and S2, after the output signal of the output port passes through an uplink optical fiber transmission link, the coherent demodulation local oscillation light of the reserved uplink optical signal of the concentric station is input into the uplink optical signal receiving module together.
Further, the downstream optical signal transmitting module includes a continuous laser CWLD1, a polarization beam splitter PBS1, a first optical I/Q modulator, a polarization beam combiner PBC, and an optical power beam splitter PS1; wherein CWLD1 provides the required frequency f 0 Is a light wave of (2); the PBS1 is used for dividing the light wave output by the CWLD1 into two paths of light waves B1 and B2 which have the same frequency but mutually orthogonal polarization states; the first optical I/Q modulator is used for modulating the downlink baseband vector electric signal baseband to the frequency f 0 On B1 with polarization state of X, generating carrier downlink baseband vector electric signalAn optical signal; the PBC is used for combining an optical signal carrying a downlink baseband vector electric signal with an unmodulated polarization state of Y and a frequency of f 0 B2 of (B) to generate a downstream optical signal; PS1 is used to split B2 into two paths of equal power.
Further, the uplink optical signal receiving module comprises an optical coherent receiver OCR1 and two polarization controllers PC1 and PC2, wherein the OCR1 is used for carrying out coherent demodulation on a wired or wireless access uplink optical signal to recover a wired or wireless access uplink baseband signal; PC1 is used for adjusting the polarization state of reserved coherent demodulation local oscillation light, and PC2 is used for adjusting the polarization state of received wired or wireless access uplink optical signals.
Furthermore, the uplink optical fiber transmission link and the downlink optical fiber transmission link are standard single mode optical fiber SSMF.
Further, the PBS2 is configured to split the received downlink optical signal including two mutually orthogonal polarization states into two optical waves; PC3 is used to adjust the polarization state of B1 separated by PBS 2; s1 is used for bearing downlink baseband vector electric signals, wherein the polarization state is X, and the frequency is f 0 B1 of (2) are respectively routed to a downlink wired access module and a downlink wireless signal transmitting module; PC4 is used for adjusting the polarization state of B2 separated by PBS2 to be consistent with the polarization state of B1, and PS2 is used for separating the polarization state of the electrical signal which does not carry the downlink baseband vector and is separated by PBS2 into Y and f 0 B2 of (2) is divided into two paths with equal power; OCR2 is used for carrying out coherent demodulation on the downlink optical signal to recover the downlink baseband electric signal; the CWLD2 is used for providing heterodyne beat frequency local oscillation light of the wireless access of the downlink optical signal and wireless access uplink optical carrier, the PBS3 is used for dividing the optical wave output by the CWLD2 into two paths of optical waves B3 and B4 with orthogonal polarization, the PC5 is used for adjusting the polarization state of the B3, the OC is used for coupling the heterodyne beat frequency local oscillation light B3 with the B1 which is separated by the PBS2 and carries the downlink baseband vector electric signal, the PD is used for heterodyne beat frequency detection, the optical signal is converted into an electric signal, the EBPF is used for filtering out the downlink wireless access millimeter wave signal, and the transmitting antenna is used for transmitting the downlink wireless access millimeter wave signal; the OBPF is used for filtering out an optical sideband carrying the wireless access uplink baseband vector electric signal; the second optical I/Q modulator is used for The wired access uplink baseband vector electric signal is modulated onto an optical carrier of a wired access uplink to generate a wired access uplink optical signal.
Further, the wireless user terminal comprises a receiving antenna for receiving downlink wireless access millimeter wave signals, a transmitting antenna for transmitting wireless access uplink millimeter wave signals, a mixer and a radio frequency local vibration source; the mixer is used for down-converting a downlink wireless access electric millimeter wave signal into a downlink baseband electric signal and loading a wireless access uplink baseband vector electric signal onto an uplink millimeter wave carrier; the radio frequency local oscillation source is used for providing radio frequency local oscillation signals, coherently demodulating downlink radio access electric millimeter wave signals into downlink baseband electric signals, and up-converting radio access uplink baseband vector electric signals into uplink electric millimeter wave signals.
The access method of the full duplex wired and wireless hybrid optical access system based on polarization multiplexing comprises the following steps:
in the downstream optical signal transmitting module of the central station, the frequency output by the continuous laser CWLD1 is f 0 First, the light wave of the (B) baseband vector electric signal is divided into two paths of light waves B1 and B2 which have the same frequency but have mutually orthogonal polarization states through a polarization beam splitter PBS1, and then, the downlink baseband vector electric signal is baseband modulated to have the frequency f in the optical domain through a first optical I/Q modulator 0 And B1 with polarization state X; and the polarization state not modulated by the downlink baseband vector electric signal is Y, and the frequency is f 0 The B2 of the (B2) is divided into two parts by an optical power beam splitter PS1, one part is reserved as coherent demodulation local oscillation light of an uplink optical signal in a central station, the other part is combined with the B1 modulated by a downlink baseband vector electric signal by polarization beam combiners PBC in a polarization manner to form a downlink optical signal, the generated downlink optical signal only comprises two orthogonal polarization states of one frequency component, and only one polarization state carries the downlink baseband vector electric signal, so that the spectrum component is simple;
transmitting a downlink optical signal to a hybrid ONU through a standard single mode fiber SSMF, and firstly utilizing a polarization beam splitter PBS2 to make the frequency in the downlink optical signal equal to f 0 But the polarization states are mutually orthogonal B1 and B2 are separated, whereinThe polarization state of B2 which is output by a lower branch of PBS2 is Y and is not modulated by a downlink baseband vector electric signal is divided into two parts by an optical power beam splitter PS2 after the polarization state is regulated by a PC4, one part is used as coherent demodulation local oscillation light which is accessed by a downlink optical signal in a wired way and is directly injected into a downlink wired access module, the other part is used as an optical carrier which is accessed by an uplink in a wired way and is used for carrying a wired access uplink baseband vector electric signal and is injected into a wired access uplink optical signal transmitting module, and the B1 which is output by an upper branch of PBS2 and carries the downlink baseband vector electric signal and has an X-polarization state is respectively routed to the downlink wireless signal transmitting module or the downlink wired access module by an optical switch S1 after the polarization state is regulated by a polarization controller PC 3;
In the downlink wireless signal transmitting module, a continuous laser CWLD2 is utilized to provide heterodyne beat frequency local oscillation light for wireless access of downlink optical signals and optical carrier wave for wireless access of uplink, and the output frequency is f at first 1 ＝f 0 -f RF The light wave of (2) is divided into two branches B3 and B4 with orthogonal polarization by a polarization beam splitter PBS3, wherein the frequency is f 1 B3 with polarization state of X is used as heterodyne beat frequency local oscillation light of the wireless access of the downlink optical signal, the polarization state is adjusted by a polarization controller PC5, and then the heterodyne beat frequency local oscillation light is coupled with a carrier downlink baseband vector electric signal by an optical coupler OC and has frequency of f 0 B1 with polarization state of X is injected into a photoelectric detector PD after being coupled, and frequency f is generated based on heterodyne beat frequency RF ＝f 0 -f 1 Finally, the electric millimeter wave signal with the center frequency f is utilized RF An electric band-pass filter EBPF with the bandwidth of 3 times of the main lobe bandwidth of the downlink baseband vector electric signal filters out the main lobe bandwidth for wireless access, feeds the main lobe bandwidth to a transmitting antenna and transmits the main lobe bandwidth to a wireless user terminal, and has a polarization state of Y and a frequency of f 1 B4 of the wireless access uplink signal is injected into a wireless access uplink signal receiving module, reserved as a wireless access uplink optical carrier and used for bearing a wireless access uplink baseband vector electric signal;
in the wireless user terminal, the frequency is f RF After receiving the downlink radio access millimeter wave signal from the receiving antenna, the signal is mixed by a mixer with a frequency f RF Is provided by a radio frequency local oscillation sourceDemodulating and recovering the downlink baseband electric signal to realize the wireless access of a downlink;
in the downlink wired access module, the frequency not modulated by the downlink baseband vector electric signal is f 0 B2 with polarization state Y is regulated to have polarization state which is equal to f with the carrier downlink baseband vector electric signal and frequency by a polarization controller PC4 0 The polarization state of B1 with the polarization state of X is kept consistent, and then the polarization state is divided into two parts by power such as an optical power beam splitter PS2, wherein one part of the polarization state and B1 are injected into an optical coherent receiver OCR2 together, B2 is used as coherent demodulation local oscillation light of B1 to carry out coherent demodulation of an optical domain on B1, a downlink baseband electric signal is recovered, the wired access of a downlink is realized, and meanwhile, the other part of optical power of B2 is used as a wired access uplink optical carrier to bear a wired access uplink baseband vector electric signal;
for the wireless access uplink, at the wireless user terminal, the wireless access uplink baseband vector electric signal and the frequency provided by the radio frequency local oscillation source are f RF After the radio frequency local oscillation signal of (2) is mixed by a mixer, the frequency is f RF Is transmitted to the hybrid ONU through a transmitting antenna; in the wireless access uplink signal receiving module of the hybrid ONU, the frequency received by the receiving antenna is f RF Is modulated by a Mach-Zehnder modulator MZM single sideband to a polarization state Y, frequency f, provided by CWLD2 1 ＝f 0 -f RF On the radio access uplink optical carrier B4, a center frequency f is reused 0 ＝f 1 +f RF An optical band-pass filter (OBPF) with the bandwidth of 3 times of the bandwidth of a main lobe of a wireless access uplink baseband vector electric signal outputs a frequency f 0 Filtering out an upper sideband carrying a wireless access uplink baseband vector electric signal to be used as a wireless access uplink optical signal;
for the wired access uplink, in the hybrid ONU, the frequency separated from the downstream optical signal by PBS2, which is not modulated by the downstream baseband vector electrical signal, is f 0 Part of the optical power of B2 with polarization state of Y is directly injected into the second optical I/Q modulator as a wired access uplink optical carrier wave to be wired accessBaseband modulation of uplink baseband vector electric signal to generate frequency f 0 Is connected with an uplink optical signal by a wire;
the generated wireless or wired access uplink optical signal is transmitted to the central station through the uplink optical fiber link after being selected by the optical switch S2, and the reserved frequency is f in the uplink optical signal receiving module of the central station 0 After the polarization state of the B2 of the partial optical power of (2) is adjusted by a polarization controller PC2, the B2 is used as coherent demodulation local oscillation light of a wireless or wired access uplink optical signal, and the coherent demodulation local oscillation light and the wireless or wired access uplink optical signal are injected into an optical coherent receiver OCR1 together, and after coherent detection, wireless or wired access uplink baseband signals are respectively obtained;
the downlink and the uplink can realize full duplex transmission of broadband signals, and form a full duplex optical link.
Preferably, the optical coherent receiver OCR1 and OCR2 are each composed of a two-input four-output 90 ° optical mixer and two pairs of balanced PDs.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages:
1. the structure of the central station and the frequency spectrum of the downlink optical signals are kept unchanged no matter whether the mixed ONU is in wired access or wireless access, the complexity of the central station is reduced, the downlink optical signal transmitting module included in the central station has a simple structure, and can generate downlink optical signals with two polarization states which are same in frequency but orthogonal to each other, so that the frequency spectrum utilization rate is improved while the structure of the central station is simplified and the cost of the central station is reduced;
2. the continuous laser CWLD1 of the central station not only provides an optical carrier wave of a downlink baseband vector electric signal, but also provides coherent demodulation local oscillation light of an uplink optical signal which is accessed wirelessly or in a wired way, thereby further simplifying the complexity of the central station;
3. In the downlink optical signals, only one polarization state carries the downlink baseband vector electric signals, and the other orthogonal polarization state is not modulated by data information, so that the influence of optical fiber dispersion is effectively reduced, the optical fiber link transmission performance of the downlink optical signals is improved, and the transmission distance of the downlink optical signals is prolonged;
4. the hybrid ONU provides wired or wireless selective access according to different demands of users, can realize 60GHz high-frequency millimeter wave wireless access based on PD or high-speed wired access based on OCR2, increases the flexibility of a network access mode, and realizes the deep fusion of an optical fiber wired access network and a wireless access network;
5. the downlink optical signal not only comprises the optical wave for bearing the downlink baseband vector electric signal, but also comprises the coherent demodulation local oscillation light of the downlink optical signal wired access and the uplink optical carrier of the wired access, and only one continuous laser CWLD2 with fixed output wavelength is needed in the hybrid ONU to provide heterodyne beat local oscillation light of the downlink optical signal wireless access and the uplink optical carrier of the wireless access, thereby reducing the structure and the cost of the hybrid ONU.
Drawings
Fig. 1 shows a system schematic diagram of the present invention.
FIG. 2 shows the frequency f of the CWLD1 output of the central station continuous laser according to the present invention 0 Light wave of 193.1 THz.
FIG. 3 is a spectrum of a 40Gbit/s,16-QAM (10 Gbaud) downstream baseband vector electrical signal baseband modulated at 193.1THz optical carrier with polarization state X.
FIG. 4 is a spectrum of a downstream optical signal obtained by the polarization beam combiner PBC of the present invention.
Fig. 5 shows a light wave with a polarization state X and a frequency 193.1THz, which is obtained by passing through a polarization beam splitter PBS2 and carries a downlink baseband vector electric signal.
Fig. 6 shows a light wave with a polarization state Y and a frequency 193.1THz, which is obtained by the polarization beam splitter PBS2 and is not modulated by the downlink baseband vector electric signal, in the present invention.
Fig. 7 shows a light wave with a frequency of 193.04THz output from the continuous laser CWLD2 with a fixed output wavelength in the hybrid ONU according to the present invention.
Fig. 8 is a spectrum diagram of an optical wave formed by coupling a B1 carrying a downlink baseband vector electric signal and having a frequency of 193.1THz with a heterodyne beat frequency local oscillation light B3 having a frequency of 193.04THz provided by a continuous laser CWLD2 through an optical coupler OC.
Fig. 9 is a downlink radio access millimeter wave signal with a frequency of 60GHz generated in the present invention.
Fig. 10 is a diagram of a 40Gbit/s,16-QAM downlink baseband electric signal constellation and I, Q branch eye diagram obtained by coherent demodulation of a downlink radio access millimeter wave signal with a frequency of 60GHz in the present invention under (a) back-to-back condition without wireless transmission and (b) 20 km optical fiber transmission.
Fig. 11 shows a 40Gbit/s, a 16-QAM downlink baseband electric signal constellation diagram and a I, Q branch eye diagram obtained by coherent demodulation after (a) back-to-back and (b) 20 km optical fiber transmission of the downlink wired access in the present invention.
Fig. 12 is a spectrum diagram of a wireless access uplink optical carrier with a frequency of 193.04THz after single sideband modulation of a 60GHz uplink electric millimeter wave signal of 40Gbit/s, 16-QAM.
Fig. 13 is a spectral diagram of a wireless access uplink optical signal filtered out by an optical band pass filter OBPF in the present invention.
Fig. 14 is a diagram of a 40Gbit/s, a 16-QAM uplink baseband electric signal constellation and a I, Q branch eye diagram obtained by coherent demodulation of a radio access uplink under (a) back-to-back conditions without radio transmission and (b) 20 km optical fiber transmission to a central station in the present invention.
Fig. 15 is a spectrum diagram of a wired access uplink optical signal generated by modulating a wired access uplink optical carrier wave with a frequency of 193.1THz by a 40Gbit/s,16-QAM uplink baseband vector electric signal baseband in the present invention.
Fig. 16 shows a 40Gbit/s, a 16-QAM uplink baseband electric signal constellation diagram and a I, Q branch eye diagram obtained by coherent demodulation of a wired access uplink in the present invention after (a) back-to-back condition and (b) transmission to a central station via 20 km optical fiber.
Wherein: the back-to-back case, i.e. the fiber length is 0km.
Detailed Description
The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of the embodiments, which proceeds with reference to fig. 1-16. The following embodiments are described in detail with reference to the drawings.
The full duplex wired and wireless hybrid optical access system based on polarization multiplexing comprises a central station, an optical fiber transmission link between the central station and a hybrid ONU, the hybrid ONU and a wireless user terminal.
The central station comprises a downlink optical signal transmitting module and an uplink optical signal receiving module, wherein the downlink optical signal transmitting module comprises a continuous laser CWLD1, a polarization beam splitter PBS1, a first optical I/Q modulator, a polarization beam combiner PBC and an optical power beam splitter PS1; wherein CWLD1 provides the required frequency f 0 Is a light wave of (2); the PBS1 is used for dividing the light wave output by the CWLD1 into two paths of light waves B1 and B2 which have the same frequency but mutually orthogonal polarization states; the first optical I/Q modulator is used for modulating the downlink baseband vector electric signal baseband to the frequency f 0 On B1 with polarization state of X, generating optical signal for bearing downlink baseband vector electric signal; the PBC is used for combining an optical signal carrying a downlink baseband vector electric signal with an unmodulated polarization state of Y and a frequency of f 0 B2 of (B) to generate a downstream optical signal; PS1 is used for dividing B2 into two paths with equal power; the uplink optical signal receiving module comprises an optical coherent receiver OCR1 and two polarization controllers PC1 and PC2, wherein the OCR1 is used for carrying out coherent demodulation on a wired or wireless access uplink optical signal to recover a wired or wireless access uplink baseband signal; PC1 is used for adjusting the polarization state of reserved coherent demodulation local oscillation light, and PC2 is used for adjusting the polarization state of received wired or wireless access uplink optical signals.
The transmission link between the central station and the hybrid ONU comprises an uplink optical fiber transmission link and a downlink optical fiber transmission link: the transmission of the uplink optical signal and the downlink optical signal is realized, and the transmission comprises a standard single mode fiber SSMF.
The hybrid ONU comprises a polarization beam splitter PBS2, a polarization controller PC3, two optical switches S1 and S2, a downlink wired access module, a downlink wireless signal transmitting module, a wireless access uplink signal receiving module and a wired access uplink optical signal transmitting module; the PBS2 is used for dividing a received downlink optical signal containing two mutually orthogonal polarization states into two paths of optical waves; PC3 is used to adjust the polarization state of B1 separated by PBS 2; s1 is used for bearing downlinkThe polarization state of the baseband vector electric signal is X, and the frequency is f 0 B1 of (2) are respectively routed to a downlink wired access module and a downlink wireless signal transmitting module; s2, selecting wireless or wired access to uplink optical signals; the downlink wired access module comprises a polarization controller PC4, an optical power beam splitter PS2 and an optical coherence receiver OCR2, wherein the PC4 is used for adjusting the polarization state of B2 separated by the PBS2 to be consistent with the polarization state of B1, and the PS2 is used for separating the polarization state of the electrical signal which does not carry the downlink baseband vector and is separated by the PBS2, wherein the polarization state is Y and the frequency is f 0 B2 of (2) is divided into two paths with equal power; OCR2 is used for carrying out coherent demodulation on the downlink optical signal to recover the downlink baseband electric signal; the downlink wireless signal transmitting module comprises a continuous laser CWLD2, a polarization beam splitter PBS3, a polarization controller PC5, an optical coupler OC, a photoelectric detector PD, an electric band-pass filter EBPF and a transmitting antenna, wherein the CWLD2 is used for providing heterodyne beat frequency local oscillation light and wireless access uplink optical carrier waves which are accessed by downlink optical signals wirelessly, the PBS3 is used for dividing optical waves output by the CWLD2 into two paths of optical waves B3 and B4 with orthogonal polarization, the PC5 is used for adjusting the polarization state of the B3, the OC is used for coupling the heterodyne beat frequency local oscillation light B3 with the B1 which is separated by the PBS2 and carries downlink baseband vector electric signals, the PD is used for heterodyne beat frequency detection, the optical signals are converted into electric signals, the EBPF is used for filtering downlink wireless access electric millimeter wave signals, and the transmitting antenna is used for transmitting the downlink wireless access electric millimeter wave signals; the wireless access uplink signal receiving module comprises a receiving antenna for receiving a wireless access uplink electric millimeter wave signal, a Mach-Zehnder modulator MZM for electro-optical conversion and an Optical Band Pass Filter (OBPF) for filtering out an optical band carrying a wireless access uplink baseband vector electric signal; the wired access uplink optical signal transmitting module comprises a second optical I/Q modulator, which is used for modulating the wired access uplink baseband vector electric signal baseband to an optical carrier of the wired access uplink to generate a wired access uplink optical signal.
The wireless user terminal comprises a receiving antenna for receiving downlink wireless access millimeter wave signals, a transmitting antenna for transmitting wireless access uplink millimeter wave signals, a mixer and a radio frequency local vibration source; the mixer is used for down-converting a downlink wireless access electric millimeter wave signal into a downlink baseband electric signal and loading a wireless access uplink baseband vector electric signal onto an uplink millimeter wave carrier; the radio frequency local oscillation source is used for providing radio frequency local oscillation signals, coherently demodulating downlink radio access electric millimeter wave signals into downlink baseband electric signals, and up-converting radio access uplink baseband vector electric signals into uplink electric millimeter wave signals.
The access method of the full duplex wired and wireless hybrid optical access system based on polarization multiplexing comprises the following steps:
in the downstream optical signal transmitting module of the central station, the frequency output by the continuous laser CWLD1 is f 0 First, the light wave of (2) is divided into two paths of B1 and B2 having the same frequency but orthogonal polarization states by a polarization beam splitter PBS1, wherein the light wave has a light frequency f 0 193.1THz (1552.5 nm), linewidth of 0.1MHz, output optical power of 5dBm, and spectrum of the optical fiber is shown in fig. 2. Wherein the polarization state is X, frequency f 0 B1, 193.1THz, is injected into the first optical I/Q modulator, the driving signal of the first optical I/Q modulator is a downlink 10Gbaud vector signal formed by mapping binary data with the rate of 40Gbit/s by a constellation diagram of 16-QAM and then pulse forming, and the half-wave voltage of the first optical I/Q modulator is 4V. After electro-optic modulation by the first optical I/Q modulator, the downlink baseband vector electric signal is modulated to a frequency f in a baseband mode 0 An optical wave carrying a downstream baseband vector electrical signal as shown in fig. 3 is generated on an optical carrier B1 with 193.1THz and a polarization state X. Then, the polarization beam combiner PBC combines it with the B2 polarization with the polarization state Y and frequency 193.1THz, which is not modulated by the downlink baseband vector electric signal, to generate a downlink optical signal, and the spectrum is shown in fig. 4. Only B1 with polarization state X carries the downlink baseband vector electric signal, its bandwidth is obviously widened, and B2 with polarization state Y does not carry any data information, and is a pure light wave, its bandwidth is not widened, but directly overlapped with B1 polarization multiplexing. The resulting downstream optical signal comprising two mutually orthogonal polarizations is injected into a downstream optical fiber transmission link. Meanwhile, B2 with polarization state of Y and frequency of 193.1THz passes through optical power before being combined with B1 polarization The beam splitter PS1 filters out part of the optical power, and reserves a coherent demodulation local oscillation light for wireless or wired access to an uplink optical signal at the central station after the polarization state is adjusted by the polarization controller PC 1.
In the downlink transmission link, the downlink is formed by standard single mode fiber SSMF, so that the downlink optical signal can be transmitted to the hybrid ONU, the influence of chromatic dispersion of the optical fiber is very small, and the nonlinearity of the optical fiber is small, so that the optical fiber can be ignored.
Transmitting a downlink optical signal to a hybrid ONU through a standard single mode fiber SSMF, and firstly utilizing a polarization beam splitter PBS2 to make the frequency in the downlink optical signal equal to f 0 The polarization states of the B1 and B2 which are=193.1 THz but are orthogonal to each other are separated, wherein the B1 carrying downlink baseband vector electric signal and having the polarization state of X and the frequency of 193.1THz output by the upper branch of the PBS2 has a spectrum as shown in fig. 5, the polarization state of the B1 is firstly adjusted by the polarization controller PC3, and then the optical switch S1 routes the B1 to a downlink wireless signal transmitting module or a downlink wired access module according to different user access modes, so as to realize wireless access or wired access of a downlink optical signal; the spectrum of the B2 which is outputted by the lower branch of the PBS2, has a polarization state of Y and a frequency of 193.1THz and is not modulated by the downlink baseband vector electric signal is shown in fig. 6, and the spectrum is reserved as the coherent demodulation local oscillation light of the downlink optical signal wired access and the optical carrier of the uplink wired access, so as to realize the wired access of the downlink optical signal and the loading of the wired access uplink baseband vector signal. For downlink wireless access, in a downlink wireless signal transmitting module of the hybrid ONU, a frequency output by a continuous laser CWLD2 with a fixed output wavelength is f 1 The optical wave of = 193.04THz is first divided into two paths of optical waves B3 and B4 with the same frequency but orthogonal polarization states by a polarization beam splitter PBS3, wherein the polarization state is X and the polarization state is B3 with the frequency of 193.04THz, the spectrum is shown in fig. 7, after the polarization state is adjusted by a polarization controller PC5, the optical wave is coupled with a B1 carrying a downlink baseband vector electric signal, the polarization state is X and the frequency is 193.1THz separated by a PBS2 by an optical coupler OC, the spectrum of the optical wave is formed after coupling, as shown in fig. 8, the spectrum is heterodyned by a photoelectric detector PD, and the spectrum is photoelectrically converted into the frequency f RF ＝f 0 -f 1 An electric millimeter wave signal of 60GHz, which is centered onAn electric band-pass filter EBPF with the frequency of 60GHz and the bandwidth of 25GHz is filtered out, the frequency spectrum is shown in figure 9, the electric band-pass filter EBPF is fed to a transmitting antenna, the electric band-pass filter EBPF is transmitted to a wireless user terminal through the transmitting antenna, in order to check the optical fiber transmission performance of a downlink wireless access signal, a downlink wireless access millimeter wave signal generated in the invention is not transmitted wirelessly, but is subjected to electric domain coherent demodulation by directly utilizing a mixer and a radio frequency local oscillation signal with the frequency of 60GHz in a hybrid ONU, namely, the mixer and the radio frequency local oscillation source of the wireless user terminal are moved into the hybrid ONU, and a downlink baseband electric signal constellation diagram and a I, Q branch eye diagram obtained by coherent demodulation are shown in figure 10 after back-to-back (0 km) and 20km optical fiber transmission; for downstream wired access, in a downstream wired access module of the hybrid ONU, B2 which is separated by PBS2 and is not modulated by a downstream baseband vector electric signal with frequency of 193.1THz and polarization state of Y is subjected to adjustment of polarization state by PC4, so that it is consistent with polarization state of B1, then part of optical power is reserved as a wired access uplink optical carrier through an optical power beam splitter PS2 for carrying the wired access upstream baseband vector electric signal, and the other part of optical power is used as coherent demodulation local oscillation light and is injected into an optical coherent receiver OCR2 consisting of a 90 ° optical mixer and two pairs of balanced PDs together with the PC 3-adjusted polarization state carrying downstream baseband vector electric signal separated by PBS2 with frequency of 193.1THz and polarization state of X, and is subjected to coherent demodulation by an optical domain to obtain a downstream baseband eye diagram (0) and constellation diagram and I, Q after transmission by 20 optical fibers, which are shown in fig. 11.
Radio access uplink: the invention directly generates the wireless access uplink electric millimeter wave signal in the mixed ONU, namely, the mixer and the radio frequency local vibration source of the wireless user terminal are moved into the mixed ONU, the 16-QAM baseband vector electric signal of the wireless access uplink 40Gbit/s is utilized by the mixer and the frequency is f in the mixed ONU RF The frequency spectrum generated by mixing the radio frequency local oscillation signals of 60GHz is shown in fig. 12, and the electric millimeter wave signals are modulated to reserved continuous excitation fixed by the output wavelength through a single sideband of a Mach-Zehnder modulator MZM in a wireless access uplink signal receiving module of the mixed ONUThe frequency provided by the optical device CWLD2 is f 1 On a radio access uplink optical carrier B4 with polarization state Y of = 193.04THz, the spectrum of the generated millimeter wave signal is shown in fig. 12, where only the frequency is f 1 +f RF The upper sideband=193.1 THz carries the radio access uplink baseband vector electric signal, which is then filtered out by an optical band pass filter OBPF with a center frequency of 193.1THz and a bandwidth of 25GHz to generate a radio access uplink optical signal, the spectrum of which is shown in fig. 13; transmitting the signal to a central station through an uplink optical fiber link, and in an uplink optical signal receiving module of the central station, receiving a wireless access uplink optical signal with the frequency of 193.1THz and the polarization state of Y, adjusting the polarization state through a polarization controller PC2, and then obtaining the same frequency f as the reserved frequency provided by a continuous laser CWLD1 0 The optical coherence receiver OCR1 consisting of a 90-degree optical mixer and two pairs of balanced PDs is injected with the coherence demodulation local oscillation light B2 with the polarization state of 193.1THz and Y, and the wireless access uplink baseband signal is recovered through the coherence demodulation of an optical domain. The constellation diagram of the uplink baseband signal of the wireless access obtained by detection after the back-to-back condition (0 km) and the transmission through the 20km optical fiber and the I, Q branch eye diagram are shown in fig. 14.
Wired access uplink: in a wired access uplink optical signal transmitting module of the hybrid ONU, a 16-QAM baseband vector electric signal of 40Gbit/s in the wired access uplink is modulated to a frequency f which is separated by PBS2 and is not modulated by a downlink baseband vector electric signal through a second optical I/Q modulator baseband 0 On the wired access uplink optical carrier B2 with polarization state Y of =193.1 THz, a wired access uplink optical signal is generated, and the spectrum is shown in fig. 15; transmitting the signal to a central station through an uplink optical fiber link, wherein in an uplink optical signal receiving module of the central station, the signal is consistent with the wireless access uplink optical signal receiving process, namely, the reserved frequency provided by a continuous laser CWLD1 is f by using a PC1 and a PC2 respectively 0 The optical coherent receiver OCR1 consisting of a 90 DEG optical mixer and two pairs of balanced PDs is injected into the optical coherent receiver after the coherent demodulation local oscillation light B2 with the polarization state of Y and the received wired access uplink optical signals with the frequency of 193.1THz and the polarization state of Y are modulated to be consistent, and the wired access is restored through the coherent demodulation of the optical domain Into the upstream baseband electrical signal. The constellation diagram of the uplink baseband signal of the wired access obtained by detection after the back-to-back condition (0 km) and the transmission through the 20km optical fiber and the I, Q branch eye diagram are shown in fig. 16.
The downlink and the uplink can realize full duplex transmission of broadband signals, and form a full duplex optical link.
In summary, the invention provides a full duplex wired and wireless hybrid optical access system based on polarization multiplexing, which reduces the complexity of a central station, improves the spectrum utilization rate and realizes the long-distance transmission of high-rate broadband signals; the hybrid ONU flexibly and conveniently provides wired or millimeter wave wireless selective access according to different requirements of users, so that the flexibility of the hybrid ONU access mode is improved; the central station reserves the coherent demodulation local oscillation light of the uplink optical signal, further simplifies the complexity of the central station and increases the realizability of the full duplex link; the mixed ONU only needs a continuous laser CWLD2 with fixed output wavelength, heterodyne beat frequency local oscillation light for wireless access of the downlink optical signal and uplink optical carrier wave for wireless access are provided, and the structure and cost of the mixed ONU are reduced.
While the invention has been described in connection with certain embodiments, it is not intended that the invention be limited thereto; for those skilled in the art to which the present invention pertains and the related art, on the premise of based on the technical scheme of the present invention, the expansion, the operation method and the data replacement should all fall within the protection scope of the present invention.

Claims (5)

1. The full duplex wired and wireless hybrid optical access system based on polarization multiplexing is characterized in that: the system comprises a central station, an uplink optical fiber transmission link and a downlink optical fiber transmission link between the central station and the mixed ONU, the mixed ONU and a wireless user terminal;
the central station comprises a downlink optical signal transmitting module and an uplink optical signal receiving module, wherein one part of output signals of the downlink optical signal transmitting module are reserved as coherent demodulation local oscillation light of uplink optical signals in the central station, and the other part of the output signals form downlink optical signals which are sent into the hybrid ONU through a downlink optical fiber transmission link;
the mixed ONU comprises a polarization beam splitter PBS2, a polarization controller PC3, two optical switches S1 and S2, a downlink wired access module, a downlink wireless signal transmitting module, a wireless access uplink signal receiving module and a wired access uplink optical signal transmitting module, wherein the PBS2 is used for dividing a received downlink optical signal into two paths of optical waves, one path of optical wave is sent to an input port of the S1 through the PC3, and the other path of optical wave is sent to the downlink wired access module; the downlink wireless signal transmitting module comprises a continuous laser CWLD2, a polarization beam splitter PBS3, a polarization controller PC5, an optical coupler OC, a photoelectric detector PD, an electric band-pass filter EBPF and a transmitting antenna which are sequentially connected, wherein the input end of the OC is also connected with a first output port of S1, the output end of the PBS3 is also connected with a wireless access uplink signal receiving module, and the transmitting antenna transmits the output signal of the EBPF to a wireless user terminal; the wireless access uplink signal receiving module comprises a receiving antenna, an output signal of the receiving antenna is sent to a Mach-Zehnder modulator (MZM), the input end of the MZM is also connected with the output end of the PBS3, and the output end of the MZM is connected with a first input port of the S2 through an Optical Band Pass Filter (OBPF); the downlink wired access module comprises a polarization controller PC4, an optical power beam splitter PS2 and an optical coherence receiver OCR2 which are sequentially connected, wherein the input end of the OCR2 is also connected with a second output port of the S1, and the output end of the PS2 is also connected with the wired access uplink optical signal transmitting module; the wired access uplink optical signal transmitting module comprises a second optical I/Q modulator, wherein the input end of the second optical I/Q modulator is connected with the output end of the PS2, and the output end of the second optical I/Q modulator is connected with the second input port of the S2; s2, after the output signal of the output port passes through an uplink optical fiber transmission link, the coherent demodulation local oscillation light of the reserved uplink optical signal of the concentric station is input into an uplink optical signal receiving module together;
The downlink optical signal transmitting module comprises a continuous laser CWLD1, a polarization beam splitter PBS1, a first optical I/Q modulator, a polarization beam combiner PBC and an optical power beam splitter PS1; wherein CWLD1 provides the required frequency f 0 Is a light wave of (2); the PBS1 is used for dividing the light wave output by the CWLD1 into two paths of light waves B1 and B2 which have the same frequency but mutually orthogonal polarization states; the first optical I/Q modulator is used for carrying out downlink basebandBaseband modulation of vector electric signals to a frequency f 0 On B1 with polarization state of X, generating optical signal for bearing downlink baseband vector electric signal; the PBC is used for combining an optical signal carrying a downlink baseband vector electric signal with an unmodulated polarization state of Y and a frequency of f 0 B2 of (B) to generate a downstream optical signal; PS1 is used for dividing B2 into two paths with equal power;
the uplink optical signal receiving module comprises an optical coherent receiver OCR1 and two polarization controllers PC1 and PC2, wherein the OCR1 is used for carrying out coherent demodulation on a wired or wireless access uplink optical signal to recover a wired or wireless access uplink baseband signal; the PC1 is used for adjusting the polarization state of reserved coherent demodulation local oscillation light, and the PC2 is used for adjusting the polarization state of a received wired or wireless access uplink optical signal;
the uplink optical fiber transmission link and the downlink optical fiber transmission link are standard single mode optical fiber SSMF; optical frequency f 0 193.1THz, linewidth of 0.1MHz, output optical power of 5dBm.
2. The polarization multiplexing-based full duplex wire-wireless hybrid optical access system of claim 1,
the method is characterized in that: the PBS2 is used for dividing a received downlink optical signal containing two mutually orthogonal polarization states into two paths of optical waves; PC3 is used to adjust the polarization state of B1 separated by PBS 2; s1 is used for bearing downlink baseband vector electric signals, wherein the polarization state is X, and the frequency is f 0 B1 of (2) are respectively routed to a downlink wired access module and a downlink wireless signal transmitting module; PC4 is used for adjusting the polarization state of B2 separated by PBS2 to be consistent with the polarization state of B1, and PS2 is used for separating the polarization state of the electrical signal which does not carry the downlink baseband vector and is separated by PBS2 into Y and f 0 B2 of (2) is divided into two paths with equal power; OCR2 is used for carrying out coherent demodulation on the downlink optical signal to recover the downlink baseband electric signal; CWLD2 is used for providing heterodyne beat frequency local oscillation light of downlink optical signal wireless access and wireless access uplink optical carrier wave, PBS3 is used for dividing light wave output by CWLD2 into two paths of light waves B3 and B4 with orthogonal polarization, PC5 is used for adjusting polarization state of B3, OC is used for dividing heterodyne beat frequency local oscillation light B3 and carrying downlink baseband The vector electric signals are coupled by B1 separated by PBS2, PD is used for heterodyne beat frequency detection, optical signals are converted into electric signals, EBPF is used for filtering out downlink radio access millimeter wave signals, and the transmitting antenna is used for transmitting the downlink radio access millimeter wave signals; the OBPF is used for filtering out an optical sideband carrying the wireless access uplink baseband vector electric signal; the second optical I/Q modulator is configured to baseband modulate the wired access uplink baseband vector electrical signal onto an optical carrier of the wired access uplink, to generate a wired access uplink optical signal.
3. The polarization multiplexing based full duplex wired/wireless hybrid optical access system according to claim 2, wherein: the wireless user terminal comprises a receiving antenna for receiving downlink wireless access electric millimeter wave signals, a transmitting antenna for transmitting wireless access uplink electric millimeter wave signals, a mixer and a radio frequency local vibration source; the mixer is used for down-converting a downlink wireless access electric millimeter wave signal into a downlink baseband electric signal and loading a wireless access uplink baseband vector electric signal onto an uplink millimeter wave carrier; the radio frequency local oscillation source is used for providing radio frequency local oscillation signals, coherently demodulating downlink radio access electric millimeter wave signals into downlink baseband electric signals, and up-converting radio access uplink baseband vector electric signals into uplink electric millimeter wave signals.
4. An access method applied to the full duplex wired and wireless hybrid optical access system based on polarization multiplexing as claimed in claim 3, comprising the following steps:
in the downstream optical signal transmitting module of the central station, the frequency output by the continuous laser CWLD1 is f 0 First, the light wave of the (B) baseband vector electric signal is divided into two paths of light waves B1 and B2 which have the same frequency but have mutually orthogonal polarization states through a polarization beam splitter PBS1, and then, the downlink baseband vector electric signal is baseband modulated to have the frequency f in the optical domain through a first optical I/Q modulator 0 And B1 with polarization state X; and the polarization state not modulated by the downlink baseband vector electric signal is Y, and the frequency is f 0 Is divided into two parts by an optical power beam splitter PS1, one part is at the centerThe station reserves coherent demodulation local oscillation light for uplink optical signals, the other part of the coherent demodulation local oscillation light is combined with B1 modulated by downlink baseband vector electric signals through polarization beam combiners PBC in a polarization mode to form downlink optical signals, the generated downlink optical signals only comprise two orthogonal polarization states of one frequency component, and only one polarization state carries the downlink baseband vector electric signals, so that the spectrum components are simple;
transmitting a downlink optical signal to a hybrid ONU through a standard single mode fiber SSMF, and firstly utilizing a polarization beam splitter PBS2 to make the frequency in the downlink optical signal equal to f 0 But the polarization states of the B1 and the B2 which are mutually orthogonal are separated, wherein the polarization state of the B2 which is output by a lower branch of the PBS2 is Y, the B2 which is not modulated by a downlink baseband vector electric signal is divided into two parts by an optical power beam splitter PS2 after the polarization state is regulated by a PC4, one part is used as coherent demodulation local oscillation light which is connected with a downlink optical signal in a wired way and is directly injected into a downlink wired access module, the other part is used as an optical carrier which is connected with an uplink in a wired way and is used for carrying the wired access uplink baseband vector electric signal and injecting the optical carrier into a wired access uplink optical signal transmitting module, and the downlink baseband vector electric signal which is output by an upper branch of the PBS2 and the B1 with an X-polarization state are respectively routed to the downlink wireless signal transmitting module or the downlink wired access module by an optical switch S1 after the polarization state is regulated by a polarization controller PC 3;
in the downlink wireless signal transmitting module, a continuous laser CWLD2 is utilized to provide heterodyne beat frequency local oscillation light for wireless access of downlink optical signals and optical carrier wave for wireless access of uplink, and the output frequency is f at first 1 ＝f 0 -f RF The light wave of (2) is divided into two branches B3 and B4 with orthogonal polarization by a polarization beam splitter PBS3, wherein the frequency is f 1 B3 with polarization state of X is used as heterodyne beat frequency local oscillation light of the wireless access of the downlink optical signal, the polarization state is adjusted by a polarization controller PC5, and then the heterodyne beat frequency local oscillation light is coupled with a carrier downlink baseband vector electric signal by an optical coupler OC and has frequency of f 0 B1 with polarization state of X is injected into a photoelectric detector PD after being coupled, and frequency f is generated based on heterodyne beat frequency RF ＝f 0 -f 1 Finally, the electric millimeter wave signal with the center frequency f is utilized RF Downstream baseband vector electric signal with 3 times bandwidthAn electric band-pass filter EBPF of main lobe bandwidth filters it out for wireless access, feeds to a transmitting antenna and transmits to a wireless user terminal with polarization state Y and frequency f 1 B4 of the wireless access uplink signal is injected into a wireless access uplink signal receiving module, reserved as a wireless access uplink optical carrier and used for bearing a wireless access uplink baseband vector electric signal;
in the wireless user terminal, the frequency is f RF After receiving the downlink radio access millimeter wave signal from the receiving antenna, the signal is mixed by a mixer with a frequency f RF A downlink baseband electric signal is recovered through coherent demodulation of a radio frequency local oscillation signal provided by a radio frequency local oscillation source, so that wireless access of a downlink is realized;
in the downlink wired access module, the frequency not modulated by the downlink baseband vector electric signal is f 0 B2 with polarization state Y is regulated to have polarization state which is equal to f with the carrier downlink baseband vector electric signal and frequency by a polarization controller PC4 0 The polarization state of B1 with the polarization state of X is kept consistent, and then the polarization state is divided into two parts by power such as an optical power beam splitter PS2, wherein one part of the polarization state and B1 are injected into an optical coherent receiver OCR2 together, B2 is used as coherent demodulation local oscillation light of B1 to carry out coherent demodulation of an optical domain on B1, a downlink baseband electric signal is recovered, the wired access of a downlink is realized, and meanwhile, the other part of optical power of B2 is used as a wired access uplink optical carrier to bear a wired access uplink baseband vector electric signal;
For the wireless access uplink, at the wireless user terminal, the wireless access uplink baseband vector electric signal and the frequency provided by the radio frequency local oscillation source are f RF After the radio frequency local oscillation signal of (2) is mixed by a mixer, the frequency is f RF Is transmitted to the hybrid ONU through a transmitting antenna; in the wireless access uplink signal receiving module of the hybrid ONU, the frequency received by the receiving antenna is f RF Is modulated by a Mach-Zehnder modulator MZM single sideband to a polarization state Y, frequency f, provided by CWLD2 1 ＝f 0 -f RF On the radio access uplink optical carrier B4, a center frequency f is reused 0 ＝f 1 +f RF An optical band-pass filter (OBPF) with the bandwidth of 3 times of the bandwidth of a main lobe of a wireless access uplink baseband vector electric signal outputs a frequency f 0 Filtering out an upper sideband carrying a wireless access uplink baseband vector electric signal to be used as a wireless access uplink optical signal;
for the wired access uplink, in the hybrid ONU, the frequency separated from the downstream optical signal by PBS2, which is not modulated by the downstream baseband vector electrical signal, is f 0 Part of the optical power of B2 with polarization state of Y is directly injected into a second optical I/Q modulator as a wired access uplink optical carrier wave to be modulated by a wired access uplink baseband vector electric signal baseband, and the frequency f is generated 0 Is connected with an uplink optical signal by a wire;
the generated wireless or wired access uplink optical signal is transmitted to the central station through the uplink optical fiber link after being selected by the optical switch S2, and the reserved frequency is f in the uplink optical signal receiving module of the central station 0 After the polarization state of the B2 of the partial optical power of (2) is adjusted by a polarization controller PC2, the B2 is used as coherent demodulation local oscillation light of a wireless or wired access uplink optical signal, and the coherent demodulation local oscillation light and the wireless or wired access uplink optical signal are injected into an optical coherent receiver OCR1 together, and after coherent detection, wireless or wired access uplink baseband signals are respectively obtained;
the downlink and the uplink can realize full duplex transmission of broadband signals, and form a full duplex optical link.
5. The access method according to claim 4, characterized in that: the optical coherent receiver OCR1 and OCR2 are composed of a two-input four-output 90-degree optical mixer and two pairs of balance PDs.
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