CN111769883A - Passive ONU scheme for coherent detection OFDM-PON fusion TDM - Google Patents
Passive ONU scheme for coherent detection OFDM-PON fusion TDM Download PDFInfo
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- CN111769883A CN111769883A CN202010552200.3A CN202010552200A CN111769883A CN 111769883 A CN111769883 A CN 111769883A CN 202010552200 A CN202010552200 A CN 202010552200A CN 111769883 A CN111769883 A CN 111769883A
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- 230000001427 coherent effect Effects 0.000 title claims abstract description 27
- 238000001514 detection method Methods 0.000 title claims description 21
- 230000004927 fusion Effects 0.000 title claims description 6
- 230000003287 optical effect Effects 0.000 claims abstract description 28
- 230000010287 polarization Effects 0.000 claims abstract description 28
- 239000000969 carrier Substances 0.000 claims abstract description 9
- 239000013307 optical fiber Substances 0.000 claims abstract description 6
- 230000008054 signal transmission Effects 0.000 claims abstract description 6
- 238000011144 upstream manufacturing Methods 0.000 claims description 7
- 230000005540 biological transmission Effects 0.000 abstract description 9
- 238000000034 method Methods 0.000 abstract description 8
- 239000006185 dispersion Substances 0.000 abstract description 3
- 230000010355 oscillation Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 5
- 239000000835 fiber Substances 0.000 description 4
- 230000003595 spectral effect Effects 0.000 description 3
- 229910003327 LiNbO3 Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000004913 activation Effects 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
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- 238000004891 communication Methods 0.000 description 1
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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
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/613—Coherent receivers including phase diversity, e.g., having in-phase and quadrature branches, as in QPSK coherent receivers
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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
- H04B10/60—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
Abstract
The invention discloses a method and a system technical scheme for realizing ONU passivity by fusing OFDM (orthogonal frequency division multiplexing) -PON (passive optical network) with TDM (time division multiplexing). And the OLT side is provided with a downlink signal transmission transmitting end of the OFDM-PON and an uplink signal transmission receiving end of the TDM-PON. At the OLT end, the light carrier emitted by the laser is divided into mutually orthogonal X and Y polarized carriers through the polarization beam splitter, the X polarized carrier loads information, and the Y polarized carrier does not load information. And a Splitter is arranged at the RN side, and the combined wave signal is transmitted along the optical fiber through the Splitter and then is broadcast to each ONU. At the ONU end, the X carrier is subjected to coherent reception, the Y carrier passes through the Splitter, and a part of the Y carrier passes through the polarization controller and then is used as a local oscillation light source of the X polarization signal; the other part is used as an uplink emission light source of the TDM-PON. Each ONU uses a TDMA mode to transmit signals in an uplink way, and the signals reach the OLT end to be received and demodulated. The invention can realize the passivity of the ONU, improve the transmission capacity and the anti-dispersion capability of the system, coexist with the existing TDM-PON system and realize the smooth upgrade of the next generation system.
Description
Technical Field
The invention belongs to an optical access network communication system, and particularly relates to a method and a system for realizing ONU (optical network unit) non-activation by integrating coherent detection OFDM (orthogonal frequency division multiplexing) -PON (passive optical network) with TDM (time division multiplexing).
Background
The rapid development of new service networks such as cloud computing and high definition video, the bandwidth demand of these services on the access Network is higher and higher, the bandwidth demand is rapidly increased, and a Passive Optical Network (PON) technology having the advantages of low cost, multi-user access, ultra-long distance transmission, high transmission bandwidth, and the like has been the first choice for solving the bandwidth bottleneck of the access Network. With the development and maturation of passive optical networks, FTTX technologies (a series of optical access technologies from fiber to the home, from fiber to the building, from fiber to the roadside, etc.) are beginning to be widely used in the global field. The current Passive Optical Network is mainly a Time Division Multiplexing-Passive Optical Network (TDM-PON). The uplink and the downlink of the TDM-PON both adopt single wavelength, the utilization rate of the user shared bandwidth to the wavelength bandwidth is low, and different types of services also need complex scheduling algorithms and technologies. With the increasing demand for bandwidth, the TDM-PON access network based on a single wavelength inevitably encounters a bottleneck. A Wavelength division multiplexing-Passive Optical Network (WDM-PON) is a novel Passive Optical Network system based on multi-Wavelength single Optical fiber transmission which is proposed recently, and the working principle is that each terminal user independently occupies one Wavelength channel, and the plurality of Wavelength channels are transmitted in the same trunk Optical fiber in a Wavelength division multiplexing mode. The number of users can be increased by simply increasing the wavelength and maintaining the security and transparency of the protocol without affecting the current users. The biggest disadvantage of WDM-PON is the high cost of the WDM equipment and tunable transmitters and receivers.
Since TDM-PON systems are currently deployed on a large scale worldwide. Other PON systems may not be a complete replacement for TDM-PON systems for a considerable period of time in the future. Therefore, how to make TDM-P0N and other P0N coexist on the same ODN network becomes a practical problem.
Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique based on multi-carrier transmission that divides the allocated spectrum into smaller sub-carriers. Each subcarrier is then modulated by data at a lower data rate. OFDM is an efficient modulation technique that has received much attention due to its high spectral efficiency and inherent resistance to chromatic and polarization mode dispersion. OFDM is largely classified into direct detection OFDM (DD-OFDM) and coherent detection OFDM (co OFDM) according to detection methods. The CO-OFDM technique has higher spectral efficiency and better receiver sensitivity than the DD-OFDM. However, conventional coherent detection typically requires an additional laser as a Local Oscillator (LO) for complex information manipulation, which is less attractive for cost-sensitive fiber access networks, especially in the Optical Network Unit (ONU) section. In most cases, the PON architecture also includes a laser in the ONU. To reduce the transmit part of the ONU, some implementations choose to use two wavelengths, while others choose to choose the re-modulation scheme in the upstream transmission. However, the two-wavelength scheme has a low spectral efficiency, and the remodulation scheme has a limited upstream bit rate.
Disclosure of Invention
The invention mainly solves the problems of ONU non-source of coherent detection OFDM-PON and fusion with the existing TDM-PON system.
In order to solve the problems, the invention provides a method and a system technical scheme for realizing the passivity of the ONU by combining the coherent detection OFDM-PON with the TDM. The OLT side is provided with a downlink signal transmission transmitting end of the OFDM-PON and an uplink signal transmission receiving end of the TDM-PON and is also provided with a polarization beam splitter/combiner. At the OLT end, the polarization beam splitter splits the optical carrier emitted by the laser into mutually orthogonal X and Y polarized carriers, the X polarized carrier carries information, and the Y polarized carrier does not carry information. Two orthogonal optical carriers are combined and transmitted out through the polarization beam combiner; a Splitter is arranged at the RN side, and the combined wave signal is transmitted along an optical fiber through the Splitter and then is broadcast to each ONU; the ONU side is provided with a downlink receiving end of a coherent OFDM-PON and an uplink sending end of a TDM-PON, and is also provided with a polarization beam splitter, a polarization controller and a beam splitter; after the information of the combined wave passes through the polarization beam Splitter, the X carrier is subjected to coherent reception, after the Y carrier passes through the Splitter, a part of the Y carrier is used as a local oscillation light source of an X polarization signal after passing through the polarization controller, and a local oscillation laser required by coherent detection is saved in the ONU; the other part is used as an uplink emission light source of the TDM-PON, and an additional signal emission light source is not needed. And each ONU transmits OOK signals which are uplink in a TDMA mode to an OLT end to be received and demodulated after passing through a wave combiner.
In the scheme, the light source is linearly polarized light with an angle of 45 degrees.
The invention can realize the passivity of the ONU, improve the transmission capacity and the anti-dispersion capability of the system, coexist with the existing TDM-PON system and realize the smooth upgrade of the next generation system.
Drawings
Fig. 1 illustrates a method and system for implementing ONU-humanization by combining coherent OFDM-PON with TDM according to the present invention.
Fig. 2 is a block diagram of the baseband coherent OFDM modulation principle of the present system.
Fig. 3 is a block diagram of the baseband coherent OFDM demodulation principle of the present system.
Fig. 4 is a schematic diagram of a 45 ° linearly polarized light carrier wave shown at a in fig. 1.
Fig. 5 is a schematic diagram of an orthogonal X, Y polarized optical carrier shown at b in fig. 1.
Fig. 6 is a schematic diagram of the optical carrier loading signal shown at c in fig. 1.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings:
fig. 1 shows a schematic diagram of a method and system for implementing ONU-humanization by coherent OFDM-PON fusion TDM. And the passive ONU system with the coherent OFDM-PON fused with the TDM is realized by combining the polarization multiplexing technology. As shown in fig. 1, at the OLT, 45 ° linearly polarized light from a Continuous Wave (CW) laser is split into mutually orthogonal X, Y optical carriers. The X polarization signal is modulated by an Intensity Modulator (IM) in an OFDM scheme, the modulated X polarization signal and the unmodulated Y polarization signal are combined by a polarization beam combiner, the combined optical signal is divided into a plurality of beams by the beam splitter after being transmitted for a certain distance through an optical fiber, and each beam enters an Optical Network Unit (ONU).
At the ONU, the two orthogonally polarized optical signals are separated by a polarization splitter. The Y polarized light passes through 1: and 2, a part of the splitter is used as a local oscillator after passing through the polarization controller, and the coherent detection of the X polarized light OFDM signal is completed by balanced homodyne detection consisting of four couplers, a phase shifter and four photodetectors. And the other part of the Y polarized light is used as an uplink optical carrier of the TDM. The light source loads OOK signals with modulated intensity, then combines modulated signals from different ONUs through TDMA, and the OLT controls information sent to upstream by each ONU.
Fig. 2 shows a CO-OFDM transmitter. First, a Pseudo Random Binary Sequence (PRBS) generator generates a random binary sequence, which is then transferred to a QAM sequence generator. The output signal is sent to an OFDM modulator and then further mapped to subcarriers by a serial-to-parallel converter, which performs a Fast Fourier Transform (FFT). The OFDM modulator produces in-phase (I) and quadrature (Q) components of the signal, which are then passed through a low-pass cosine roll-off filter and amplifier. The output in-phase (I) and quadrature (Q) components are modulated on an optical carrier using two LiNbO3 Mach-Zehnder modulators (MZMs), the outputs of the two LiNbO3 MZMs being combined using a power combiner. Fig. 3 shows a design of a CO-OFDM receiver. The polarization conversion light source and the balanced homodyne detection composed of four couplers, a phase shifter and four photodetectors are used for coherent detection of the X-polarized light OFDM signal. After the in-phase and quadrature-phase components of the optical OFDM are detected, they are fed to an OFDM demodulator. The output of the OFDM demodulator is fed to and gives an output to a QAM sequence decoder.
FIG. 4 is a 45 ° linearly polarized light from a laser; FIG. 5 is a diagram of orthogonal X, Y polarized carriers after passing through a polarizing beam splitter; fig. 6 shows a carrier with X-polarization loaded information and Y-polarization unloaded information.
From the above description we have proposed an OFDM-PON architecture that combines polarization multiplexing and coherent detection for optical access networks. The proposed architecture eliminates the local oscillator source required for coherent detection and enables a low cost ONU. TDMA is used for upstream transmission, so the OLT only needs one receiver, and upstream OOK modulation can simplify the complexity of the ONU transmitter, reduce system cost, and be efficient for upstream transmission. Therefore, the proposed architecture is helpful to enrich and perfect the technical system of the next-generation passive optical network and lay a theoretical and technical foundation for the green and intelligent passive optical network.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.
Claims (3)
1. A coherent detection OFDM-PON fuses passive ONU scheme of TDM, characterized by that:
an OLT side is provided with a downlink signal transmission transmitting end of an OFDM-PON and an uplink signal transmission receiving end of a TDM-PON, and is provided with a polarization beam splitting/combining device, the polarization beam splitting device divides optical carriers emitted by a laser into mutually orthogonal carriers, and after information is loaded, the two orthogonal optical carriers are combined by the polarization beam combining device and transmitted; a Splitter is arranged at the RN side, and the combined wave signal is transmitted along an optical fiber through the Splitter and then is broadcast to each ONU; and the ONU side is provided with a downlink receiving end of a coherent OFDM-PON and an uplink sending end of a TDM-PON, and is also provided with a polarization beam splitter and a polarization controller.
2. The scheme of the passive ONU of coherent detection OFDM-PON fusion TDM according to claim 1, wherein 45 ° linearly polarized light emitted by the laser passes through the polarization beam splitter to generate orthogonal X, Y polarized light, wherein coherent OFDM signals are loaded on the carrier of the X polarized light, and no information is loaded on the carrier of the Y polarized light.
3. The scheme of the passive ONU of coherent detection OFDM-PON fusion TDM according to claim 1, wherein after the Y polarized light reaches the beam splitter at the ONU end, a part of the Y polarized light is used as a coherent detection local oscillator light source of the X path polarized light signal through a polarization converter, thereby completing coherent detection; and the other part is used as an upstream light source of the TDM-PON to transmit an OOK signal with modulated intensity.
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| CN202010552200.3A CN111769883A (en) | 2020-06-18 | 2020-06-18 | Passive ONU scheme for coherent detection OFDM-PON fusion TDM |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115333640A (en) * | 2022-08-12 | 2022-11-11 | 武汉邮电科学研究院有限公司 | Coherent passive optical network receiver and method and device for expanding dynamic range thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115333640A (en) * | 2022-08-12 | 2022-11-11 | 武汉邮电科学研究院有限公司 | Coherent passive optical network receiver and method and device for expanding dynamic range thereof |
| CN115333640B (en) * | 2022-08-12 | 2024-01-16 | 武汉邮电科学研究院有限公司 | Coherent passive optical network receiver and method and device for expanding dynamic range of coherent passive optical network receiver |
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