Bandwidth-saving coherent transmission method and PON system

Abstract

The application discloses a kind of bandwidth saving coherent transmission method and PON system, it is related to optical access network technical field, including: in downlink transmission direction, OLT sending end generates M digital subcarriers, after digital-analog conversion, it is carried out double polarization modulation, as downlink signal is sent to ONU receiving end;Each subarea ONU receiving end carries out heterodyne coherent detection to the partial spectrum of downlink signal, and downlink signal occupies the single sideband spectrum of ONU end light source;In the direction of uplink transmission, the data of corresponding digital subcarrier is generated by ONU sending end, and single sideband modulation is carried out based on ONU end light source, as uplink signal is sent to the OLT receiving end of corresponding subarea, and uplink signal occupies another single sideband spectrum of ONU end light source;OLT receiving end carries out analog-digital conversion and digital signal processing after heterodyne coherent detection.The application selects subcarrier by configuring light source of different wavelength at ONU end to reduce device bandwidth, so that PON system reduces cost while maintaining transmission capacity, sensitivity and flexibility.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical access network, in particular to a coherent transmission method for saving bandwidth and a PON system. BACKGROUND

[0002] In recent years, with the promotion of 5G mobile Internet, cloud networking and high-definition video streaming services, the bandwidth demand of optical access network has increased dramatically. EPON (Ethernet Passive Optical Network) and GPON (Gigabit-Capable PON) have realized 1G / 2.5G to 10G transmission capability, and ITU-T and IEEE have recently released 25G PON and 50GPON standards. With the development of PON to 50Gb / s / λ and above, intensity modulation and direct detection technology is difficult to meet the power budget requirements in high-speed systems due to factors such as poor receiving sensitivity, high speed, and power fading caused by dispersion in long transmission distance.

[0003] Coherent reception is considered a strong candidate technology for super-100G PON due to its high spectral efficiency, high sensitivity, and high flexibility. Coherent technology uses digital signal processing technology to realize various compensations after the received signal is converted to the digital domain, but its complex structure also brings higher cost and complexity to the ONU (Optical Network Unit) end.

[0004] With the standard coherent detection scheme, a local oscillator (LO) and two polarization 90° mixing are needed, and finally detection is realized through four balanced photodetectors. Due to the low-cost requirement of PON systems, in order to be widely promoted in PON applications, the coherent reception needs to be simplified to reduce the cost.

[0005] Switching from internal difference detection to external difference detection can effectively reduce the number of components at the receiving end. Dual-polarization external difference reception only needs to include two digital-to-analog converters (DACs), two balanced photodetectors (BPDs), and two analog-to-digital converters (ADCs), reducing the number of required components to half of the standard coherent reception. However, for the scheme of using simplified coherent external difference reception at the receiving end, the disadvantage is that the bandwidth of the receiving end device needs to be increased, and the required device bandwidth is twice that of the internal difference coherent reception technology. SUMMARY

[0006] The present application provides a coherent transmission method for saving bandwidth and a PON system, which selects subcarriers by configuring light sources of different wavelengths at the ONU end to reduce the device bandwidth, so that the PON system reduces the cost while maintaining the transmission capacity, sensitivity and flexibility.

[0007] In a first aspect, the embodiments of the present application provide a bandwidth-saving coherent transmission method, which comprises the following steps:

[0008] In the downlink transmission direction, the OLT transmitting end generates M digital subcarriers based on digital signal processing, performs double polarization modulation after digital-to-analog conversion, and sends the downlink signal to the ONU receiving end. The ONU end includes a plurality of partitioned ONUs, each of which includes an ONU transmitting end and an ONU receiving end.

[0009] The ONU receiving end of each partitioned ONU performs heterodyne coherent detection on part of the frequency spectrum of the downlink signal, and performs analog-to-digital conversion and digital signal processing. The downlink signal occupies a single sideband spectrum of the ONU end light source, and different partitioned ONUs use ONU end light sources with different frequencies.

[0010] In the uplink transmission direction, the ONU transmitting end of each partitioned ONU generates data of corresponding digital subcarriers based on digital signal processing, performs single sideband modulation based on the ONU end light source after digital-to-analog conversion, and sends the uplink signal to the OLT receiving end of the corresponding partition. The uplink signal occupies another single sideband spectrum of the ONU end light source.

[0011] The OLT receiving end of each partition performs analog-to-digital conversion and digital signal processing after heterodyne coherent detection.

[0012] In combination with the first aspect, in an implementation, the ONU end is divided into an A zone and a B zone, wherein the A zone ONUs are numbered from 1 to N / 2, and the B zone ONUs are numbered from N / 2+1 to N.

[0013] For the A zone ONUs, the ONU receiving end uses an ONU end light source with a frequency of f2 as a local oscillator (LO) to perform heterodyne coherent detection on the signal of the left half sideband spectrum, and receives one or more subcarriers in the first to M / 2 subcarriers.

[0014] For the B zone ONUs, the ONU receiving end uses an ONU end light source with a frequency of f3 as a LO to perform heterodyne coherent detection on the signal of the right half sideband spectrum, and receives one or more subcarriers in the M / 2+1 to M subcarriers.

[0015] The left half sideband spectrum and the right half sideband spectrum are divided with the frequency f1 as the center, and f1 is the frequency of the light source used by the OLT transmitting end when performing double polarization modulation.

[0016] In combination with the first aspect, in an implementation, the ONU receiving end of each partitioned ONU performs heterodyne coherent detection on part of the frequency spectrum of the downlink signal, and performs analog-to-digital conversion and digital signal processing, which comprises:

[0017] The ONU receiving end of each subzone couples the downlink signal and the ONU end light source by using a coupler;

[0018] The balanced optical detector is used to detect the coupled signal and convert it into an electrical signal;

[0019] The ONU receiving end ADC is used to perform analog-digital conversion on the electrical signal;

[0020] The ONU receiving end DSP is used to perform digital signal processing on the data after analog-digital conversion.

[0021] In combination with the first aspect, in an implementation, the OLT receiving end of each subzone adopts a light source with the same frequency as the ONU end light source of the corresponding subzone to perform heterodyne coherent detection.

[0022] In combination with the first aspect, in an implementation, the ONU end light source is a distributed feedback laser or an external cavity laser.

[0023] The second aspect provides a bandwidth-saving coherent PON system, which comprises an OLT end and an ONU end;

[0024] The OLT end comprises an OLT sending end and a plurality of subzone OLT receiving ends, and the ONU end comprises a plurality of subzone ONUs, each of which comprises an ONU sending end and an ONU receiving end;

[0025] In the downlink transmission direction, the OLT sending end generates M digital subcarriers based on digital signal processing, performs double-polarization modulation after digital-analog conversion, and sends the downlink signal to the ONU receiving end;

[0026] The ONU receiving end of each subzone is used to perform heterodyne coherent detection on part of the frequency spectrum of the downlink signal, and perform analog-digital conversion and digital signal processing, wherein the downlink signal occupies a single-sideband spectrum of the ONU end light source, and the ONUs of different subzones adopt different frequency ONU end light sources;

[0027] In the uplink transmission direction, the ONU sending end of each subzone generates data of the corresponding digital subcarriers based on digital signal processing, performs single-sideband modulation based on the ONU end light source after digital-analog conversion, and sends the uplink signal to the OLT receiving end of the corresponding subzone, wherein the uplink signal occupies another single-sideband spectrum of the ONU end light source;

[0028] The OLT receiving end of each subzone performs analog-digital conversion and digital signal processing after heterodyne coherent detection.

[0029] With reference to the second aspect, in an implementation, the ONU end is divided into an A region and a B region, wherein the A region ONU is numbered from 1 to N / 2, and the B region ONU is numbered from N / 2+1 to N;

[0030] For the ONU in the A region, the ONU receiving end uses the ONU end light source with the frequency f2 as a local oscillator (LO) to perform heterodyne coherent detection on the signal in the left half spectrum, and receives one or more subcarriers in the first to M / 2 subcarriers;

[0031] For the ONU in the B region, the ONU receiving end uses the ONU end light source with the frequency f3 as a LO to perform heterodyne coherent detection on the signal in the right half spectrum, and receives one or more subcarriers in the M / 2+1 to M subcarriers;

[0032] The left half spectrum and the right half spectrum are divided with the frequency f1 as the center, and f1 is the frequency of the light source used when the OLT sending end performs dual-polarization modulation.

[0033] With reference to the second aspect, in an implementation, the ONU receiving end of each subregion includes an ONU end light source, a heterodyne coherent receiver, an ONU receiving end ADC, and an ONU receiving end DSP, and the heterodyne coherent receiver includes a coupler and a balanced optical detector.

[0034] The coupler is configured to couple the downlink signal and the ONU end light source;

[0035] The balanced optical detector is configured to detect the coupled signal and convert the coupled signal into an electrical signal;

[0036] The ONU receiving end ADC is configured to perform analog-to-digital conversion on the electrical signal;

[0037] The ONU receiving end DSP is configured to perform digital signal processing on the data after the analog-to-digital conversion.

[0038] With reference to the second aspect, in an implementation, the OLT receiving end of each subregion uses a light source with the same frequency as the ONU end light source of the corresponding subregion to perform heterodyne coherent detection.

[0039] With reference to the second aspect, in an implementation, the ONU end light source is a distributed feedback laser or an external cavity laser.

[0040] The technical scheme provided by the embodiments of the present application has at least the following beneficial effects:

[0041] The bandwidth-saving coherent transmission method in the application is as follows: in the downlink transmission direction, the OLT sending end generates M digital subcarriers based on digital signal processing, performs double polarization modulation after digital-to-analog conversion, and sends the downlink signal to the ONU receiving end; the ONU end includes a plurality of partitioned ONUs, each of which includes an ONU sending end and an ONU receiving end; the ONU receiving end of each partitioned ONU performs heterodyne coherent detection on part of the spectrum of the downlink signal, and performs analog-to-digital conversion and digital signal processing, wherein the downlink signal occupies a single sideband spectrum of the ONU end light source, and different partitioned ONUs use different frequency ONU end light sources; in the uplink transmission direction, the ONU sending end of each partitioned ONU generates corresponding digital subcarrier data based on digital signal processing, performs single sideband modulation based on the ONU end light source after digital-to-analog conversion, and sends the uplink signal to the corresponding partitioned OLT receiving end, wherein the uplink signal occupies another single sideband spectrum of the ONU end light source; the OLT receiving end of each partitioned ONU performs analog-to-digital conversion and digital signal processing after heterodyne coherent detection.

[0042] That is, the application uses simple heterodyne coherent reception at the ONU end, uses only one light source for transceiver sharing, and uses the method of selecting one of the light sources in different partitions, thereby reducing the required bandwidth of the receiver device, reducing the cost while retaining the advantages of high speed, large capacity, and high power budget of the coherent system. The innovative spectrum allocation method also improves the spectrum utilization rate. At the same time, the TFDM technology also makes the spectrum allocation of the network very flexible. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 Flowchart of an embodiment of the bandwidth-saving coherent transmission method of the application;

[0044] Figure 2 Structure block diagram of an embodiment of the bandwidth-saving coherent PON system of the application;

[0045] Figure 3 Downlink and uplink signal optical spectrum allocation diagram in the application. DETAILED DESCRIPTION

[0046] In order to enable personnel in the technical field to better understand the application scheme, the technical solutions in the embodiments of the application will be described clearly and completely below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0047] The terms "comprise", "comprising", "include", "including", "have" and "having" and any variations thereof in the specification and in the claims are intended to cover both the express and implicit described features. For example, a process, method, system, product, or apparatus that comprises a list of steps or elements is not necessarily limited to those listed steps or elements but can include other not-listed steps or elements. The terms "first", "second", and "third" and the like, are used to distinguish between similar objects and are not necessarily used to indicate the order or precedence of one over another. The terms "a" and "an" are used to refer to one or more than one, unless otherwise indicated by the context.

[0048] In the description of the embodiments of the present application, "exemplary", "for example", "e.g." or "for instance" are used on the basis that a person of ordinary skill in the art will be aware that one or more embodiments of the present application can include other embodiments as appropriate, and also on the basis that one of ordinary skill in the art will be aware of many ways for modifying or performing the embodiments of the present application. Any embodiment or design scheme described as "exemplary", "for example", or "for instance" in the embodiments of the present application should not be interpreted as being more preferred or advantageous than other embodiments or design schemes. In fact, the words "exemplary", "for example", or "for instance" are used to present related concepts in a specific way.

[0049] In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B; "and / or" in the text only describes the relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone. In addition, in the description of the embodiments of the present application, "multiple" means two or more than two.

[0050] In some of the processes described in the embodiments of the present application, a plurality of operations or steps are included in a specific order, but it should be understood that these operations or steps can be executed or performed in parallel or in an order different from that in which they appear in the embodiments of the present application. The serial number of the operation is only used to distinguish different operations, and the serial number itself does not represent any execution order. In addition, these processes can include more or fewer operations, and these operations or steps can be executed in sequence or in parallel, and these operations or steps can be combined.

[0051] In order to make the purposes, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0052] In a first aspect, the embodiments of the present application provide a bandwidth-saving coherent transmission method.

[0053] In an embodiment, referring to Figure 1 , Figure 1 The flowchart of an embodiment of the bandwidth-saving coherent transmission method of the present application is shown in FIG. 1. As shown in FIG. 1, the method comprises the following steps. Figure 1The bandwidth-saving coherent transmission method comprises:

[0054] S1, in the downlink transmission direction, the OLT (Optical Line Terminal) transmitting end generates M digital subcarriers based on digital signal processing, performs double polarization modulation after digital-to-analog conversion, and sends the downlink signal to the ONU receiving end, the ONU end includes a plurality of partitioned ONUs, and each partitioned ONU includes an ONU transmitting end and an ONU receiving end;

[0055] S2, each partitioned ONU receiving end performs heterodyne coherent detection on the part of the spectrum of the downlink signal, and performs analog-to-digital conversion and digital signal processing, wherein the downlink signal occupies a single sideband spectrum of the ONU end light source, and different partitioned ONUs use different frequency ONU end light sources;

[0056] S3, in the uplink transmission direction, each partitioned ONU transmitting end generates corresponding digital subcarrier data based on digital signal processing, performs single sideband modulation based on the ONU end light source after digital-to-analog conversion, and sends the uplink signal to the corresponding partitioned OLT receiving end, wherein the uplink signal occupies another single sideband spectrum of the ONU end light source;

[0057] S4, each partitioned OLT receiving end performs analog-to-digital conversion and digital signal processing after heterodyne coherent detection.

[0058] It is worth noting that digital subcarrier multiplexing carries information on several narrower digital carriers by means of digital signal processing. This method occupies a similar bandwidth to single carrier modulation (using the same modulation format and the same total transmission capacity), but has the advantages of better tolerance to fiber nonlinear effects and spectral flexibility. In addition, the digital subcarrier multiplexing (DSCM) based coherent system is particularly suitable for point-to-multipoint network architecture. By introducing frequency division multiplexing into the coherent PON system through digital subcarrier multiplexing, only one subcarrier information is modulated and demodulated by a single ONU, reducing the bandwidth requirement of the ONU and effectively reducing the cost.

[0059] The application is applied to the field of optical access network, and realizes a TFDM-PON bidirectional transmission system based on digital subcarrier multiplexing technology. Downlink adopts heterodyne coherent reception, uplink adopts standard coherent reception, and at the ONU end, a high-efficiency spectrum allocation mode is realized by selecting the wavelength of the light source, so as to reduce the bandwidth required by the device, reduce the cost, improve the spectrum utilization rate, and improve the flexibility of the system.

[0060] The above steps will be further described below in combination with Figure 2 and Figure 3 .

[0061] The TFDM-PON bidirectional transmission system structure is shown in Figure 2 As shown in the figure. At the OLT end, it includes OLT sending end DSP, OLT sending end DAC, dual polarization IQ modulator, three light sources with frequencies of f1, f2, f3, A area standard coherent receiver and OLT receiving end ADC and OLT receiving end DSP, B area standard coherent receiver and OLT receiving end ADC and OLT receiving end DSP. The light source can be a low-cost light source, such as a distributed feedback laser DFB. Of course, a better light source can also be used, such as an external cavity laser ECL.

[0062] At the OLT end, the sending signal is processed by digital signal processing to generate M digital subcarriers, which are converted into analog signals by OLT sending end DAC, and then modulated by dual polarization IQ modulator. The frequency of the modulated light source is f1. The M channels of the modulated light signal are received in two areas at the ONU end after passing through the ODN. The ONU end can be divided into two or more areas according to actual needs. In this embodiment, the ONU end is divided into two areas: A area and B area. The receiving signals of the OLT are divided into two paths for heterodyne coherent detection, and the LO frequencies used are f2 and f3 respectively.

[0063] At the ONU end, each ONU includes a heterodyne coherent receiver, an ONU receiving end ADC, an ONU receiving end DSP, an ONU sending end DSP, an ONU sending end DAC, a dual polarization IQ modulator, and an ONU end light source with a frequency of f2 or f3. The heterodyne coherent receiver includes a 3dB coupler and a balanced photodetector (BPD). The ONU selects the light source with a frequency of f2 or f3 as LO to heterodyne receive half of the spectrum of the downlink optical signal according to the area it belongs to. The sending signal is modulated by the same light source as the carrier for single sideband modulation and then sent uplink.

[0064] The N ONUs are divided into A area and B area, the numbering of the A area ONUs is 1~N / 2, and the numbering of the B area ONUs is N / 2+1~N. For the A area ONUs, a light source with frequency f2 is used as LO to perform heterodyne coherent reception on the signal of the left half spectrum, and one or more subcarriers in the first to M / 2 subcarriers are received. The light source with frequency f2 is also used as a modulation light source, and a double polarization IQ modulator is used to perform single sideband modulation on the sending data processed by the ONU sending end DSP to the optical signal, which is received in the A area heterodyne coherent receiver at the OLT end after passing through the ODN. For the B area ONUs, a light source with frequency f3 is used as LO to perform heterodyne coherent reception on the signal of the right half spectrum, and one or more subcarriers in the M / 2+1 to M subcarriers are received. The light source with frequency f3 is also used as a modulation light source, and a double polarization IQ modulator is used to perform single sideband modulation on the sending data processed by the ONU sending end DSP to the optical signal, which is received in the B area heterodyne coherent receiver at the OLT end after passing through the ODN. The left half spectrum and the right half spectrum are divided with frequency f1 as the center,

[0065] It is worth noting that since the ONUs in the A area and the B area only need to receive half of the number of subcarriers, the required bandwidth of the devices is reduced to 1 / 2 of that required for receiving complete signals. The optical spectrum diagram of the uplink and downlink signals is shown in Figure 3 The frequency difference between frequencies f1 and f2 is half of the spectrum of the OLT end sending signal, plus the required interval bandwidth. The frequency difference between frequencies f3 and f1 is also half of the spectrum of the OLT end sending signal, plus the required interval bandwidth.

[0066] The bidirectional TFDM-PON architecture realized by using the above scheme uses simple heterodyne coherent reception at the ONU end, and only one light source needs to be set at the ONU end. Since heterodyne coherent detection is used, in the downlink transmission direction, the ONU end light source can use a single sideband spectrum for coherent reception, and in the uplink transmission direction, the other single sideband spectrum of the ONU end light source can be used for modulation, so that the structure and algorithm of the ONU can be greatly simplified, and the system cost is greatly reduced.

[0067] In addition, the use of a light source that selects one of frequencies f2 and f3 reduces the required bandwidth of the receiver devices, reduces the cost while retaining the advantages of high speed, large capacity, and high power budget of the coherent system. The innovative spectrum allocation method also improves the spectrum utilization rate. At the same time, the TFDM technology also makes the spectrum allocation of the network very flexible.

[0068] In summary, the bandwidth-saving coherent transmission method in the application generates M digital subcarriers based on digital signal processing at the OLT transmitting end in the downstream transmission direction, performs double polarization modulation after digital-to-analog conversion, and sends the downstream signal to the ONU receiving end; the ONU end includes a plurality of partitioned ONUs, each of which includes an ONU transmitting end and an ONU receiving end; the ONU receiving end of each partitioned ONU performs heterodyne coherent detection on part of the frequency spectrum of the downstream signal, and performs analog-to-digital conversion and digital signal processing, wherein the downstream signal occupies a single sideband spectrum of the ONU end light source, and different partitioned ONUs use different frequency ONU end light sources; in the upstream transmission direction, the ONU transmitting end of each partitioned ONU generates corresponding digital subcarrier data based on digital signal processing, performs single sideband modulation based on the ONU end light source after digital-to-analog conversion, and sends the upstream signal to the corresponding partitioned OLT receiving end, wherein the upstream signal occupies another single sideband spectrum of the ONU end light source; the OLT receiving end of each partitioned ONU performs analog-to-digital conversion and digital signal processing after heterodyne coherent detection.

[0069] That is, the application uses simple heterodyne coherent reception at the ONU end, uses only one light source for transceiver sharing, and uses the method of selecting one of the light sources in different partitions, thereby reducing the required bandwidth of the receiver device, reducing the cost while retaining the advantages of high speed, large capacity, and high power budget of the coherent system. The innovative spectrum allocation method also improves the spectrum utilization rate. At the same time, the TFDM technology also makes the spectrum allocation of the network very flexible.

[0070] In a second aspect, the embodiments of the application also provide a bandwidth-saving coherent PON system.

[0071] In an embodiment, referring to Figure 2 , Figure 2 Figure 1 is a functional module schematic diagram of an embodiment of the bandwidth-saving coherent PON system of the application. As shown in Figure 2 Figure 2 , the bandwidth-saving coherent PON system includes an OLT end and an ONU end.

[0072] The OLT end includes an OLT transmitting end and a plurality of partitioned OLT receiving ends, and the ONU end includes a plurality of partitioned ONUs, each of which includes an ONU transmitting end and an ONU receiving end;

[0073] In the downstream transmission direction, the OLT transmitting end generates M digital subcarriers based on digital signal processing, performs double polarization modulation after digital-to-analog conversion, and sends the downstream signal to the ONU receiving end;

[0074] The ONU receiving end of each subarea is configured to perform heterodyne coherent detection on the partial spectrum of the downstream signal, and to perform analog-digital conversion and digital signal processing, wherein the downstream signal occupies a single side spectrum of the ONU end light source, and different subareas of the ONU adopt different frequencies of the ONU end light source;

[0075] In the uplink transmission direction, the ONU transmitting end of each subarea generates data of corresponding digital subcarriers based on digital signal processing, performs single sideband modulation based on the ONU end light source after digital-analog conversion, and sends the uplink signal to the OLT receiving end of the corresponding subarea, wherein the uplink signal occupies another single side spectrum of the ONU end light source;

[0076] The OLT receiving end of each subarea performs analog-digital conversion and digital signal processing after heterodyne coherent detection.

[0077] Further, in an embodiment, the ONU end is divided into an A area and a B area, wherein the numbering of the A area ONU is 1-N / 2, and the numbering of the B area ONU is N / 2+1-N;

[0078] For the ONU in the A area, the ONU receiving end adopts the ONU end light source with a frequency of f2 as a local oscillator (LO) to perform heterodyne coherent detection on the signal of the left half side spectrum, and receives one or more subcarriers in the first to M / 2 subcarriers;

[0079] For the ONU in the B area, the ONU receiving end adopts the ONU end light source with a frequency of f3 as a LO to perform heterodyne coherent detection on the signal of the right half side spectrum, and receives one or more subcarriers in the M / 2+1 to M subcarriers;

[0080] Wherein, the left half side spectrum and the right half side spectrum are divided with the frequency f1 as the center, and f1 is the frequency of the light source adopted by the OLT transmitting end when performing dual polarization modulation.

[0081] Further, in an embodiment, the ONU receiving end of each subarea includes an ONU end light source, a heterodyne coherent receiver, an ONU receiving end ADC, and an ONU receiving end DSP, and the heterodyne coherent receiver includes a coupler and a balanced optical detector;

[0082] The coupler is configured to couple the downstream signal and the ONU end light source;

[0083] The balanced optical detector is configured to detect the coupled signal and convert it into an electrical signal;

[0084] The ONU receiving end ADC performs analog-digital conversion on the electrical signal;

[0085] The ONU receiving end DSP is configured to perform digital signal processing on the data after analog-digital conversion.

[0086] Correspondingly, the OLT sending end comprises an OLT sending end DSP, an OLT sending end DAC and a first modulator. The OLT sending end DSP is configured to generate M digital subcarriers based on digital signal processing in the downstream transmission direction; the OLT sending end DAC is configured to perform digital-to-analog conversion; and the first modulator is configured to perform dual-polarization modulation on the digital-to-analog converted signal to generate a downstream signal for sending to the ONU receiving end. Preferably, the first modulator is a dual-polarization IQ modulator (DP-IQM).

[0087] The ONU sending end comprises an ONU sending end DSP, an ONU sending end DAC and a second modulator. The ONU sending end DSP is configured to generate data of corresponding digital subcarriers based on digital signal processing; the ONU sending end DAC is configured to perform digital-to-analog conversion; and the second modulator is configured to perform single-sideband modulation based on the ONU end light source to generate an upstream signal for sending to the OLT receiving end. Preferably, the second modulator is a dual-polarization IQ modulator.

[0088] The OLT receiving end comprises an OLT receiving end coherent receiver, an OLT receiving end ADC and an OLT receiving end DSP. The OLT receiving end coherent receiver is configured to perform coherent reception on the upstream signal; the OLT receiving end ADC is configured to perform analog-to-digital conversion on the coherent received signal; and the OLT receiving end DSP is configured to perform digital signal processing on the data processed by the OLT receiving end coherent receiver.

[0089] Further, in an embodiment, the OLT receiving end of each subzone adopts a light source with the same frequency as the ONU end light source of the corresponding subzone to perform heterodyne coherent detection.

[0090] Further, in an embodiment, the ONU end light source is a distributed feedback laser or an external cavity laser.

[0091] The above is merely a preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation based on the content of the specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A bandwidth-efficient coherent transmission method, characterized by, The bandwidth-saving coherent transmission method comprises the following steps: In the downstream transmission direction, the OLT sending end generates M digital subcarriers based on digital signal processing, performs double polarization modulation after digital-to-analog conversion, and sends the downstream signal to the ONU receiving end; the ONU end comprises a plurality of partitioned ONUs, each of which comprises an ONU sending end and an ONU receiving end; Each partitioned ONU receiving end performs heterodyne coherent detection on part of the frequency spectrum of the downstream signal, and performs analog-to-digital conversion and digital signal processing, wherein the downstream signal occupies a single sideband spectrum of the ONU end light source, and different partitioned ONUs use different frequency ONU end light sources; In the upstream transmission direction, each partitioned ONU sending end generates corresponding digital subcarrier data based on digital signal processing, performs single sideband modulation based on the ONU end light source after digital-to-analog conversion, and sends the upstream signal to the corresponding partitioned OLT receiving end, wherein the upstream signal occupies another single sideband spectrum of the ONU end light source; Each partitioned OLT receiving end performs analog-to-digital conversion and digital signal processing after heterodyne coherent detection; The ONU end is divided into A and B zones, wherein the A zone ONU is numbered 1~N / 2, and the B zone ONU is numbered N / 2+1~N; For the A zone ONU, the ONU receiving end uses an ONU end light source with a frequency of f2 as a local oscillator (LO) to perform heterodyne coherent detection on the signal of the left half sideband spectrum, and receives one or more subcarriers in the first to M / 2 subcarriers; For the B zone ONU, the ONU receiving end uses an ONU end light source with a frequency of f3 as a LO to perform heterodyne coherent detection on the signal of the right half sideband spectrum, and receives one or more subcarriers in the M / 2+1 to M subcarriers; Wherein, the left half sideband spectrum and the right half sideband spectrum are divided with the frequency f1 as the center, and f1 is the frequency of the light source used by the OLT sending end when performing double polarization modulation.

2. The bandwidth-efficient coherent transmission method of claim 1, wherein, The ONU receiving end of each partitioned ONU performs heterodyne coherent detection on part of the frequency spectrum of the downstream signal, and performs analog-to-digital conversion and digital signal processing, comprising: Each partitioned ONU receiving end couples the downstream signal and the ONU end light source using a coupler; A balanced optical detector is used to detect the coupled signal and convert it into an electrical signal; An ONU receiving end ADC is used to perform analog-to-digital conversion on the electrical signal; An ONU receiving end DSP is used to perform digital signal processing on the data after analog-to-digital conversion.

3. The bandwidth-saving coherent transmission method of claim 1, wherein: Each partitioned OLT receiving end uses a light source with the same frequency as the corresponding partitioned ONU end light source to perform heterodyne coherent detection.

4. The bandwidth-efficient coherent transmission method of claim 1, wherein, The ONU end light source is a distributed feedback laser or an external cavity laser.

5. A bandwidth-efficient coherent PON system, characterized by The bandwidth-saving coherent PON system comprises an OLT end and an ONU end; The OLT end comprises an OLT sending end and a plurality of partitioned OLT receiving ends, and the ONU end comprises a plurality of partitioned ONUs, each of which comprises an ONU sending end and an ONU receiving end; In the downstream transmission direction, the OLT transmitting end generates M digital subcarriers based on digital signal processing, performs double polarization modulation after digital-to-analog conversion, and sends the downstream signal to the ONU receiving end; The ONU receiving end of each subarea is configured to perform heterodyne coherent detection on part of the frequency spectrum of the downstream signal, and perform analog-to-digital conversion and digital signal processing, wherein the downstream signal occupies a single sideband spectrum of the ONU end light source, and different subareas of the ONU use different frequencies of the ONU end light source; In the upstream transmission direction, the ONU transmitting end of each subarea generates corresponding digital subcarrier data based on digital signal processing, performs single sideband modulation based on the ONU end light source after digital-to-analog conversion, and sends the upstream signal to the OLT receiving end of the corresponding subarea, wherein the upstream signal occupies another single sideband spectrum of the ONU end light source; The OLT receiving end of each subarea performs analog-to-digital conversion and digital signal processing after heterodyne coherent detection; The ONU end is divided into A area and B area, wherein the number of A area ONU is 1~N / 2, and the number of B area ONU is N / 2+1~N; For the ONU in the A area, the ONU receiving end uses the ONU end light source with a frequency of f2 as a local oscillator (LO) to perform heterodyne coherent detection on the signal of the left half sideband spectrum, and receives one or more subcarriers in the first to M / 2 subcarriers; For the ONU in the B area, the ONU receiving end uses the ONU end light source with a frequency of f3 as a LO to perform heterodyne coherent detection on the signal of the right half sideband spectrum, and receives one or more subcarriers in the M / 2+1 to M subcarriers; Wherein, the left half sideband spectrum and the right half sideband spectrum are divided with the frequency f1 as the center, and f1 is the frequency of the light source used by the OLT transmitting end when performing double polarization modulation.

6. The bandwidth-saving coherent PON system of claim 5, wherein: The ONU receiving end of each subarea comprises an ONU end light source, a heterodyne coherent receiver, an ONU receiving end ADC, and an ONU receiving end DSP, and the heterodyne coherent receiver comprises a coupler and a balanced optical detector; The coupler is configured to couple the downstream signal and the ONU end light source; The balanced optical detector is configured to detect the coupled signal and convert it into an electrical signal; The ONU receiving end ADC is configured to perform analog-to-digital conversion on the electrical signal; The ONU receiving end DSP is configured to perform digital signal processing on the data after analog-to-digital conversion.

7. The bandwidth-saving coherent PON system of claim 5, wherein: The OLT receiving end of each subarea uses a light source with the same frequency as the ONU end light source of the corresponding subarea to perform heterodyne coherent detection.

8. The bandwidth-efficient coherent transmission method of claim 5, wherein, The ONU end light source is a distributed feedback laser or an external cavity laser.

Images