Passive optical network transmission method and passive optical network system

Abstract

This application provides a passive optical network (PON) transmission method and a PON system, relating to the field of PON technology. The PON system includes an optical line terminal (OLT), an optical distribution network (ODN), and multiple optical network units (ONUs). The ODN is connected to the multiple ONUs via free-space channels. The method includes: the OLT transmitting a first optical signal to be transmitted to the ODN; the ODN converting the first optical signal to be transmitted into a first vector light and transmitting the first vector light to the ONUs via the free-space channels; and the ONUs obtaining downlink data based on the first vector light. The method further includes: the ONUs transmitting a second vector light to the ODN via the free-space channels; the ODN transmitting a signal to be processed to the OLT; and the OLT obtaining uplink data based on the signal to be processed. This avoids the dependence of the PON on fiber optic infrastructure and reduces system costs.

Description

Technical Field

[0001] This application relates to the field of passive optical network technology, and more specifically, to a passive optical network transmission method and a passive optical network system. Background Technology

[0002] Passive Optical Network (PON) is a point-to-multipoint fiber optic transmission and access technology that features a simple network structure, shared fiber optic resources, low cost, and no need for external active equipment.

[0003] However, current passive optical network technology mainly relies on physical fiber optic links, which makes fiber optic deployment difficult and costly in some areas with complex terrain (such as remote mountainous areas, deserts, and oceans); it also lacks flexibility in some scenarios that require temporary setup or mobility (such as disaster relief sites, mobile access scenarios for large events, etc.) and cannot quickly respond to temporary and mobile communication needs. Summary of the Invention

[0004] In order to at least overcome the above-mentioned shortcomings in the prior art, the purpose of this application is to provide a passive optical network transmission method and a passive optical network system.

[0005] In a first aspect, embodiments of this application provide a passive optical network transmission method, which is applied to a passive optical network system. The passive optical network system includes an optical line terminal (OLT), an optical distribution network (ODN), and multiple optical network units (ONUs). The OLT is connected to the ODN, and the ODN is connected to the multiple ONUs via free-space channels. The method includes: For a downlink optical carrier, the optical line terminal generates a downlink optical carrier and transmits a first optical signal to be transmitted obtained by modulating the downlink optical carrier to the optical distribution network; the first optical signal to be transmitted carries first user data. The optical distribution network converts the first optical signal to be transmitted sent by the optical line terminal into a first vector light, and sends the first vector light to the corresponding optical network unit through the free space channel; The optical network unit receives the first vector light transmitted by the optical distribution network and performs vector optical field demodulation on the first vector light to obtain downlink data; The method further includes: For the uplink optical carrier, the optical network unit modulates the uplink optical carrier to obtain a second optical signal to be transmitted, and transmits the second vector light obtained by converting the second optical signal to be transmitted to the optical distribution network through the free space channel; the second optical signal to be transmitted carries second user data; The optical distribution network receives the second vector light sent by the multiple optical network units respectively, performs vector optical field demodulation and beam combining on each second vector light, and sends the resulting optical signal to be processed to the optical line terminal. The optical line terminal receives the optical signal to be processed sent by the optical distribution network and demodulates the optical signal to obtain uplink data.

[0006] In one possible implementation, the optical line terminal includes a first laser generating module, a first beam splitting module, a signal modulation module, and a first beam combining module; The steps of generating a downlink optical carrier at the optical line terminal and transmitting a first optical signal to be transmitted by modulating the downlink optical carrier to the optical distribution network include: An initial optical signal is generated by the first laser generation module; the initial optical signal is a multi-wavelength laser. The initial optical signal is split by the first beam splitting module to obtain multiple downlink optical carriers corresponding to different wavelengths. The downlink optical carriers are modulated by the signal modulation module to obtain each modulated optical signal, and the modulated optical signal carries first user data using space-time coding. The first light combining module performs light combining processing on each of the modulated optical signals to obtain a first optical signal to be transmitted, and then sends the first optical signal to be transmitted to the optical distribution network.

[0007] In one possible implementation, the step of modulating each of the downlink optical carriers by the signal modulation module to obtain each modulated optical signal includes: Obtain first user data; The first user data is converted into downlink transmission symbols, and the downlink transmission symbols are grouped. Based on the grouping results, the downlink transmission symbols are subjected to space-time coding to obtain coded symbols; The encoded symbols are input to the modulation module through a first transmission dimension and a second transmission dimension; the first transmission dimension is the X-polarization state, and the second transmission dimension is the Y-polarization state. The coded symbols are modulated onto each downlink optical carrier by the modulation module to obtain each modulated optical signal.

[0008] In one possible implementation, the optical network unit includes a second laser generation module, a digital modulation module, and a first vector light field control module; The steps of the optical network unit modulating the uplink optical carrier to obtain a second optical signal to be transmitted, and converting the second optical signal to be transmitted into a second vector light, and transmitting the second vector light to the optical distribution network through the free space channel include: The uplink optical carrier is generated by the second laser generation module; The uplink optical carrier is modulated by the digital modulation module to obtain the second optical signal to be transmitted; The second optical signal to be transmitted is converted into a second vector light by the first vector light field modulation module, and the second vector light is transmitted to the optical distribution network through the free space channel.

[0009] In one possible implementation, the step of modulating the uplink optical carrier using the digital modulation module to obtain the second optical signal to be transmitted includes: Obtain second user data; The second user data is subjected to source coding and channel coding to obtain coded data; The second optical signal to be transmitted is obtained by the digital modulation module performing BPSK code modulation based on the encoded data and the uplink optical carrier.

[0010] In one possible implementation, the optical network unit further includes a signal processing module; The step of the optical network unit receiving the first vector light transmitted by the optical distribution network and performing vector optical field demodulation on the first vector light to obtain downlink data includes: The first vector light transmitted by the light distribution network is received by the first vector light field modulation module, and the first vector light is demodulated by vector light field to obtain the first Gaussian beam. The signal processing module performs photoelectric conversion and digital signal conversion on the first Gaussian beam to obtain downlink data.

[0011] Secondly, embodiments of this application also provide a passive optical network system, which includes an optical line terminal, an optical distribution network, and multiple optical network units; The optical line terminal is connected to the optical distribution network, and the optical distribution network is connected to multiple optical network units respectively through free space channels; The optical line terminal is used to generate a downlink optical carrier in the downlink direction and transmit a first optical signal to be transmitted obtained by modulating the downlink optical carrier to the optical distribution network; the first optical signal to be transmitted carries first user data. The optical distribution network is used to convert the first optical signal to be transmitted sent by the optical line terminal into a first vector light in the downlink direction, and to send the first vector light to the corresponding optical network unit through the free space channel; The optical network unit is used to receive the first vector light transmitted by the optical distribution network in the downlink direction, and to perform vector optical field demodulation on the first vector light to obtain downlink data; The optical network unit is used to modulate a second optical signal to be transmitted in the uplink direction based on the second user data and the uplink optical carrier, and to transmit the second vector light obtained by converting the second optical signal to be transmitted to the optical distribution network through the free space channel. The optical distribution network is used to receive the second vector light transmitted by multiple optical network units in the uplink direction, and to perform vector optical field demodulation and beam combining on each second vector light, and to send the resulting optical signal to be processed to the optical line terminal. The optical line terminal is used to receive the optical signal to be processed sent by the optical distribution network in the uplink direction, and to demodulate the optical signal to be processed to obtain uplink data.

[0012] In one possible implementation, the optical line terminal includes a first laser generating module, a first beam splitting module, a signal modulation module, a first beam combining module, a second beam splitting module, and an information demodulation module; The first laser generating module is used to generate an initial optical signal in the downward direction; the initial optical signal is a multi-wavelength laser. The first beam splitting module is used to perform beam splitting processing on the initial optical signal in the downlink direction to obtain downlink optical carriers corresponding to each wavelength; The signal modulation module is used to modulate each of the downlink optical carriers in the downlink direction to obtain each modulated optical signal, and the modulated optical signal carries first user data using space-time coding. The first optical combining module is used to perform optical combining processing on each of the modulated optical signals in the downlink direction to obtain a first optical signal to be transmitted; The second beam splitting module is used to perform beam splitting processing on the optical signal to be processed sent by the optical distribution network in the uplink direction to obtain the optical signal to be demodulated corresponding to each wavelength; The information demodulation module is used to demodulate the optical signal to be demodulated in the uplink direction to obtain uplink data.

[0013] In one possible implementation, the optical network unit includes a first vector light field modulation module, a signal processing module, a second laser generation module, and a digital modulation module; The first vector light field modulation module is used to demodulate the first vector light field in the downward direction to obtain a first Gaussian beam; The signal processing module is used to perform photoelectric conversion and digital signal conversion processing on the first Gaussian beam in the down direction to obtain downlink data; The second laser generating module is used to generate an uplink optical carrier in the uplink direction; The digital modulation module is used to modulate the uplink optical carrier in the uplink direction to obtain a second optical signal to be transmitted; the second optical signal to be transmitted carries second user data; The first vector light field modulation module is used to convert the second optical signal to be transmitted into a second vector light in the uplink direction.

[0014] In one possible implementation, the light distribution network includes a third beam splitting module, a second vector light field modulation module, and a second beam combining module; The third beam splitting module is used to perform beam splitting processing on the first optical signal to be transmitted in the downlink direction to obtain each optical signal to be modulated. The second vector light field modulation module is used to convert the optical signal to be modulated into a first vector light in the downlink direction; The second vector light field modulation module is used to perform vector light field demodulation processing on the second vector light sent by each of the optical network units in the uplink direction to obtain the second Gaussian beam corresponding to each of the second vector lights; The second beam combining module is used to combine each of the second Gaussian beams in the upward direction to obtain the optical signal to be processed.

[0015] Based on any of the above aspects, the passive optical network transmission method and passive optical network system provided in this application realize the connection between the optical distribution network and multiple optical network units through the free space channel. This can avoid the high dependence of the passive optical network on the optical fiber infrastructure, and can realize high bandwidth and low latency optical signal transmission without laying optical cables. It can be applied to complex scenarios where the cost of laying optical fibers is high or difficult. In addition, by converting the optical signal into a vector beam, the anti-turbulence capability of the passive optical network system can be effectively improved, while reducing the system cost and making information transmission more secure. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings required in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is one of the structural schematic diagrams of the passive optical network system provided in this embodiment; Figure 2 This is one of the flowcharts illustrating the passive optical network transmission method provided in this embodiment; Figure 3 This is the second flowchart illustrating the passive optical network transmission method provided in this embodiment; Figure 4 This is the second schematic diagram of the passive optical network system provided in this embodiment; Figure 5 This is a schematic diagram of the sub-steps of step S110 provided in this embodiment; Figure 6 This is a schematic diagram of the sub-steps of step S113 provided in this embodiment; Figure 7 This is a schematic diagram of the sub-steps of step S210 provided in this embodiment; Figure 8 This is a schematic diagram of the sub-steps of step S212 provided in this embodiment; Figure 9 This is a schematic diagram of the sub-steps of step S130 provided in this embodiment; Figure 10a This is a schematic diagram of the structure of radially vector-polarized light provided in this embodiment; Figure 10b This is a schematic diagram of the structure of angularly vector-polarized light provided in this embodiment.

[0018] Icons: 100 - Optical Line Terminal; 200 - Optical Distribution Network; 300 - Optical Network Unit; 110 - First Laser Generation Module; 120 - First Beam Splitting Module; 130 - Signal Modulation Module; 140 - First Beam Combining Module; 150 - Second Beam Splitting Module; 160 - Information Demodulation Module; 210 - Third Beam Splitting Module; 220 - Second Vector Light Field Control Module; 230 - Second Beam Combining Module; 310 - First Vector Light Field Control Module; 320 - Signal Processing Module; 330 - Second Laser Generation Module; 340 - Digital Modulation Module; 350 - User Information Processing Unit. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] It should be noted that, where there is no conflict, different features in the embodiments of this application can be combined with each other.

[0024] The inventors' research revealed that currently commonly used passive optical network technologies mainly include combining wavelength division multiplexing (WDM) with passive optical networks (PON), and combining WDM, PON, and free space optical communications (FSO). However, for free space channels with complex and variable link environments, atmospheric turbulence and other factors can easily lead to a decrease in signal quality and affect the stability of signal transmission.

[0025] In view of this, this embodiment provides a solution to the above problems, and the solution provided in this embodiment will be described in detail below.

[0026] This application provides a passive optical network (PON) transmission method, which can be applied to PON systems. Please refer to... Figure 1A passive optical network system may include an optical line terminal (OLT), an optical distribution network (ODN), and multiple optical network units (ONUs). The OLT can be connected to the ODN, and the ODN can be connected to multiple ONUs individually via free-space channels.

[0027] Please refer to Figure 2 , Figure 2 Example: A flowchart of a free-space optical communication method provided in this embodiment is shown. In the downlink direction, the passive optical network transmission method may include the following steps.

[0028] In step S110, the optical line terminal generates a downlink optical carrier and transmits a first optical signal to be transmitted obtained by modulating the downlink optical carrier to the optical distribution network; the first optical signal to be transmitted carries first user data.

[0029] In this embodiment, the optical line terminal can generate multiple downlink optical carriers of different wavelengths. For example, the wavelengths of the multiple downlink optical carriers can be λ1, λ2, ... λ1, λ2, ... λ2, respectively. n Then, multiple downlink optical carriers are modulated to carry the first user data, thereby obtaining the first optical signal to be transmitted, and the first optical signal to be transmitted is transmitted to the remote node of the optical distribution network through a short-distance optical fiber.

[0030] In step S120, the optical distribution network converts the first optical signal to be transmitted sent by the optical line terminal into a first vector light, and sends the first vector light to the corresponding optical network unit through the free space channel.

[0031] In this embodiment, the optical distribution network can receive a first optical signal to be transmitted sent by an optical line terminal, and divide the first optical signal to be transmitted according to wavelength, so that optical signals of different wavelengths can be transmitted to the corresponding optical network units respectively. Specifically, the first optical signal to be transmitted can be divided according to wavelength firstly, and then each divided optical signal can be converted into a first vector light, and the first vector light can be transmitted to the corresponding optical network unit through a free space channel.

[0032] Vector beams are a type of non-uniformly polarized light field in space whose polarization state varies with position. Due to their non-uniform polarization distribution, their vector topology exhibits a certain resistance to complex media such as atmospheric turbulence. Therefore, by converting the first optical signal to be transmitted into a first vector beam, the transmission stability and reliability of free-space optical communication in complex environments can be effectively improved.

[0033] In step S130, the optical network unit receives the first vector light transmitted by the optical distribution network and performs vector optical field demodulation on the first vector light to obtain downlink data.

[0034] In this embodiment, the optical network unit can receive the first vector light sent by the optical distribution network and perform vector optical field demodulation on the first vector light. After demodulation, the optical signal can be detected and processed by the simplified coherent receiving system to recover the downlink data. The downlink data can be the first user data sent by the optical line terminal.

[0035] Please refer to Figure 3 , Figure 3 Example: A flowchart of a free-space optical communication method provided in this embodiment is shown. In the uplink direction, the passive optical network transmission method may include the following steps.

[0036] In step S210, the optical network unit modulates the uplink optical carrier to obtain a second optical signal to be transmitted, and transmits the second vector light obtained by converting the second optical signal to be transmitted to the optical distribution network through the free space channel; the second optical signal to be transmitted carries second user data.

[0037] In this embodiment, the optical network unit can first generate an uplink optical carrier, and then modulate the uplink optical carrier to carry second user data, thereby obtaining a second optical signal to be transmitted. After obtaining the second optical signal to be transmitted, the second optical signal to be transmitted can be converted into a second vector light, and the second vector light can be transmitted to the optical distribution network through a free space channel.

[0038] In step S220, the optical distribution network receives the second vector light transmitted by the multiple optical network units respectively, performs vector optical field demodulation and beam combining on each second vector light, and sends the resulting optical signal to be processed to the optical line terminal.

[0039] In this embodiment, the optical distribution network can receive the second vector light sent by multiple optical network units respectively, and perform vector optical field demodulation and beam combining on the second vector light to obtain the optical signal to be processed. Then, the optical signal to be processed is transmitted to the optical line terminal through short-distance optical fiber.

[0040] In step S230, the optical line terminal receives the optical signal to be processed sent by the optical distribution network and demodulates the optical signal to be processed to obtain uplink data.

[0041] In this embodiment, the optical line terminal can receive the optical signal to be processed sent by the optical distribution network, perform waveform demultiplexing on the optical signal to be processed, and then demodulate the optical signal according to the wavelength to obtain uplink data. The uplink data can be the second user data sent by the optical network unit.

[0042] It should be noted that the passive optical network transmission methods for downlink optical carriers and uplink optical carriers are two independent processes with no temporal relationship.

[0043] Based on the above design, in the passive optical network transmission method provided in this embodiment, the connection between the optical distribution network and multiple optical network units is realized through a free space channel. This avoids the high dependence of the passive optical network on optical fiber infrastructure and enables high-bandwidth, low-latency optical signal transmission without the need to lay optical cables. It is suitable for complex scenarios where optical fiber laying is costly or difficult. In addition, by converting the optical signal into a vector beam, the anti-turbulence capability of the passive optical network system can be effectively improved, while reducing system costs and making information transmission more secure.

[0044] In one possible implementation, please refer to Figure 4 The optical line terminal may include a first laser generating module, a first beam splitting module, a signal modulation module, and a first beam combining module.

[0045] In the downward direction, please refer to Figure 5 Step S110 may include the following sub-steps.

[0046] Step S111: An initial optical signal is generated by the first laser generation module; the initial optical signal is a multi-wavelength laser.

[0047] In this embodiment, the first laser generation module can generate an initial optical signal according to the standard of optical communication application scenario. The initial optical signal can be a multi-wavelength continuous laser with equal channel spacing.

[0048] Step S112: The initial optical signal is split by the first beam splitting module to obtain multiple downlink optical carriers corresponding to different wavelengths.

[0049] In this embodiment, the initial optical signal generated in step S111 can be split by the first optical splitting module, and the initial optical signal can be divided into multiple downlink optical carriers of different wavelengths according to the wavelength.

[0050] Step S113: Modulate each of the downlink optical carriers through the signal modulation module to obtain each modulated optical signal, wherein the modulated optical signal carries first user data using space-time coding.

[0051] In this embodiment, the downlink optical carriers obtained in step S112 can be modulated by the signal modulation module to carry first user data using space-time coding, thereby obtaining a modulated optical signal. This can be used to combat the polarization fading of the optical signal in the free space channel.

[0052] Step S114: The first light combining module performs light combining processing on each of the modulated optical signals to obtain a first optical signal to be transmitted, and sends the first optical signal to be transmitted to the optical distribution network.

[0053] In this embodiment, the modulated optical signals obtained in step S113 can be combined using the first optical combining module, and then the power of the combined optical signal can be increased to obtain the first optical signal to be transmitted. The first optical signal to be transmitted is then transmitted to the optical distribution network via a short-distance optical fiber.

[0054] In the above design, wavelength division multiplexing (WDM) technology enables optical signals to be transmitted from the optical line terminal to the optical distribution network. This allows for parallel transmission of multiple channels on a single link, significantly improving bandwidth utilization and system capacity, and supporting a flexible dynamic bandwidth allocation mechanism.

[0055] In one possible implementation, please refer to Figure 6 Step S113 may include the following sub-steps.

[0056] Step S1131: Obtain the first user data.

[0057] Step S1132: Convert the first user data into downlink transmission symbols and group the downlink transmission symbols.

[0058] Step S1133: Perform space-time coding on the downlink transmission symbols according to the grouping results to obtain coded symbols.

[0059] Step S1134: Input the encoded symbols into the modulation module through the first transmission dimension and the second transmission dimension; the first transmission dimension is the X-polarization state and the second transmission dimension is the Y-polarization state.

[0060] Step S1135: The encoded symbols are modulated onto each of the downlink optical carriers by the modulation module to obtain each modulated optical signal.

[0061] In this embodiment, the first user data can be encoded using Alamouti to combat the polarization fading of the optical signal in free space. Alamouti encoding can be transmitted twice within two symbol periods, thus providing 50% redundancy.

[0062] Specifically, the information to be transmitted by the user can be acquired as the first user data, and source coding and channel coding can be performed on the first user data. This data is then mapped to downlink transmission symbols through QAM modulation. This process eliminates redundant information, improves transmission efficiency, and enhances anti-interference capabilities, combating atmospheric turbulence in free-space channels. The downlink transmission symbols are then grouped, with each pair of downlink transmission symbols forming a group, resulting in multiple symbol pairs. For example, and ,in, , Then, Alamouti encoding is performed on the downlink transmission symbols, and they are transmitted in the first transmission dimension and the second transmission dimension respectively within the first transmission time slot t. and Within the second transmission time slot 2t, transmissions are sent in the first and second transmission dimensions respectively. and The encoded symbols are input to the modulation module through a first transmission dimension and a second transmission dimension, wherein the polarization states of the first and second transmission dimensions are orthogonal, the first transmission dimension is the X-polarization state, and the second transmission dimension is the Y-polarization state. denoted as complex conjugate, and T denotes transpose.

[0063] After the encoded symbols are input into the modulation module, the modulation module can modulate the encoded symbols onto the downlink optical carrier to obtain a modulated optical signal, thereby enabling the first user data to be transmitted to the optical network unit.

[0064] In the X-polarization and Y-polarization states (represented by Jones vectors) The orthogonality of two consecutive pairs of symbols can be expressed as:

[0065] Here, H can represent the conjugate transpose of a matrix.

[0066] In some examples, when transmitting a symbol pair, the received symbols on the X and Y polarizations can be represented as:

[0067] Where H represents the transfer function of a linear noiseless channel, used to describe polarization effects, and its corresponding channel coefficients are: , , and Because the received signal has single polarization. The received signal can be written as:

[0068] To recover the two consecutive signs in X-polarization, we can obtain:

[0069] When an optical network unit receives an optical signal transmitted by an optical line terminal (OLT), it can use the zero-breaking criterion to decode the optical signal and recover the first user data. The encoded symbols transmitted by the OLT can be calculated in the following way:

[0070] because and Orthogonal, therefore ,in, Let H represent the determinant value, and I represent the identity matrix.

[0071] Therefore, even if a single polarization is detected, the system performance is not affected by any polarization rotation, and polarization tracking is not required, which significantly reduces the complexity of optical network units and hardware costs.

[0072] In one possible implementation, please refer again. Figure 4 The optical network unit may include a second laser generation module, a digital modulation module, and a first vector light field control module.

[0073] Please refer to Figure 7 Step S210 may include the following sub-steps.

[0074] Step S211: An uplink optical carrier is generated by the second laser generation module.

[0075] In this embodiment, an uplink optical carrier can be generated by a second laser generation module and input into a digital modulation module, wherein the uplink optical carrier is used to carry second user data.

[0076] Step S212: Modulate the uplink optical carrier using the digital modulation module to obtain the second optical signal to be transmitted.

[0077] In this embodiment, the uplink optical carrier can be modulated by a digital modulation module to carry the second user data, thereby obtaining a second optical signal to be transmitted, and the second signal to be transmitted is input into the first vector optical field control module.

[0078] Step S213: The second optical signal to be transmitted is converted into a second vector light by the first vector light field modulation module, and the second vector light is transmitted to the optical distribution network through the free space channel.

[0079] In this embodiment, the second optical signal to be transmitted can be converted into a second vector light by the first vector light field modulation module, and then transmitted to the optical distribution network through the free space channel.

[0080] In the above design, by converting the second optical signal to be transmitted into a second vector light, the stability and anti-interference ability of the optical signal in free space channel transmission can be effectively improved. Moreover, its high directivity and narrow beam characteristics can ensure the security of information transmission and effectively prevent the signal from being interfered with during transmission.

[0081] In one possible implementation, please refer to Figure 8 Step S212 may include the following sub-steps.

[0082] Step S2121: Obtain the second user data.

[0083] Step S2122: Perform source coding and channel coding on the second user data to obtain coded data.

[0084] Step S2123: The second optical signal to be transmitted is obtained by the digital modulation module performing BPSK code modulation based on the encoded data and the uplink optical carrier.

[0085] In this embodiment, second user data can be acquired first, and then source coding and channel coding can be performed on the second user data to obtain coded data. This eliminates redundant information and improves transmission efficiency. The coded data is then input into a digital modulation module, and combined with the uplink optical carrier input to the digital modulation module, BPSK code modulation is performed to generate a second optical signal to be transmitted, ensuring the anti-interference capability of the data during transmission. BPSK (Binary Phase Shift Keying) is a basic digital modulation technique that transmits binary information by changing the phase of the carrier. In BPSK modulation, two phase states (typically 0° and 180°) represent binary data "0" and "1", respectively.

[0086] In the above design, by modulating the coded data and the uplink optical carrier with BPSK code, phase noise caused by atmospheric turbulence can be effectively countered, ensuring reliable transmission in the free space channel and improving the transmission stability and reliability of the uplink.

[0087] In one possible implementation, please refer again. Figure 4 The optical network unit may further include a signal processing module.

[0088] Please refer to Figure 9 Step S130 may include the following sub-steps.

[0089] Step S131: Receive the first vector light sent by the light distribution network through the first vector light field modulation module, and demodulate the first vector light to obtain a first Gaussian beam.

[0090] Step S132: The first Gaussian beam is subjected to photoelectric conversion and digital signal conversion processing by the signal processing module to obtain downlink data.

[0091] In this embodiment, a first vector light transmitted by an optical distribution network through a free-space channel can be received by a first vector light field modulation module. The first vector light is then demodulated to restore a first Gaussian beam, which is then input into a signal processing module. Simultaneously, a second laser generation module generates a local oscillator light, which is also input into the signal processing module. The signal processing module mixes the local oscillator light with the first Gaussian beam, and then performs photoelectric conversion through the beat frequency effect, converting the optical signal into an electrical signal. Further, it performs analog-to-digital conversion to obtain downlink data.

[0092] Please refer to this again. Figure 4 This application also provides a passive optical network system, which may include an optical line terminal (OLT), an optical distribution network (ODN), and multiple optical network units (ONUs). The OLT is connected to the ODN, and the ODN is connected to the multiple ONUs via free-space channels.

[0093] An optical line terminal (OLT) can be used to generate a downlink optical carrier in the downlink direction and transmit a first optical signal to be transmitted, obtained by modulating the downlink optical carrier, to the optical distribution network. Specifically, when modulating the downlink optical carrier, Alamouti coding can be used to modulate the first user data onto the downlink optical carrier to obtain the first optical signal to be transmitted. This achieves space-time coding diversity gain and improves the downlink's anti-fading capability.

[0094] An optical distribution network can be used to convert a first optical signal to be transmitted from an optical line terminal into a first vector light in the downlink direction, and then transmit the first vector light to the corresponding optical network unit through a free space channel.

[0095] In this embodiment, the vector beam has strong anti-turbulence capability when transmitted in the free space channel, which can effectively suppress light intensity flicker and phase distortion caused by atmospheric disturbance. Therefore, after receiving the first optical signal to be transmitted, the optical distribution network can convert it into a first vector light with a specific vector topology, and transmit the first vector light stably to the corresponding optical network unit through the free space channel, effectively suppressing phase disturbance and polarization degradation caused by atmospheric turbulence.

[0096] The optical network unit can be used to receive the first vector light transmitted by the optical distribution network in the downlink direction, and demodulate the first vector light to obtain downlink data, wherein the downlink data can be the first user data transmitted by the optical line terminal.

[0097] The optical network unit can also be used to modulate a second optical signal to be transmitted in the uplink direction based on the second user data and the uplink optical carrier, and then transmit the second vector light obtained by converting the second optical signal to be transmitted to the optical distribution network through the free space channel.

[0098] In this embodiment, the optical network unit can be used to perform BPSK code modulation on the second user data and the uplink optical carrier to obtain the second optical signal to be transmitted, and convert it into a second vector light, which is then transmitted to the optical distribution network through a free space channel. This can effectively improve the transmission stability of the uplink signal in atmospheric turbulence environment.

[0099] The optical distribution network can also be used to receive second vector light transmitted by multiple optical network units in the uplink direction, perform vector optical field demodulation and beam combining on each second vector light, and send the resulting optical signal to be processed to the optical line terminal.

[0100] In this embodiment, the optical distribution network can be used to receive second vector light sent by multiple optical network units and perform vector optical field demodulation on the multiple second vector light. The demodulated beam is then combined to generate an optical signal to be processed. The optical distribution network can transmit the optical signal to be processed back to the optical line terminal through a short-distance optical fiber to complete the uplink data aggregation.

[0101] The optical line terminal (OLT) is used to receive optical signals to be processed from the optical distribution network in the uplink direction, and to demodulate the optical signals to obtain uplink data.

[0102] In this embodiment, the optical line terminal can be used to demultiplex the received optical signal to be processed and demodulate the uplink signal according to the wavelength to obtain uplink data, wherein the uplink data can be the second user data sent by the optical network unit.

[0103] In one possible implementation, please refer again. Figure 4 The optical line terminal may include a first laser generating module, a first beam splitting module, a signal modulation module, a first beam combining module, a second beam splitting module, and an information demodulation module.

[0104] The first laser generation module can be used to generate an initial optical signal in the downward direction; the initial optical signal is a multi-wavelength laser.

[0105] In this embodiment, the first laser generation module may include an optical frequency comb generation module (OFC). The optical frequency comb generation module can generate multi-wavelength continuous lasers with equal channel spacing according to the optical communication application scenario standards through electro-optic modulation, mode-locked laser, optical resonator, Kerr soliton comb and other technologies.

[0106] The first beam splitting module can be used to split the initial optical signal in the downlink direction to obtain downlink optical carriers corresponding to each wavelength.

[0107] In this embodiment, the first optical splitting module may include a wavelength demultiplexer (DeMUX), which can separate the initial optical signal of multiple wavelengths according to wavelength and output multiple single-wavelength downlink optical carriers. For example, the wavelengths of the multiple downlink optical carriers are λ1, λ2, ... λ n .

[0108] The signal modulation module can be used to modulate each downlink optical carrier in the downlink direction to obtain each modulated optical signal, and the modulated optical signal carries the first user data using space-time coding.

[0109] In this embodiment, the signal modulation module may include an application-specific integrated circuit (ASIC), a dual-polarization IQ modulator (DP-IQ Mod.), and a digital-to-analog converter (DAC). The ASIC is responsible for generating the first user data with space-time coding. The DAC converts the coded data into an analog electrical signal. The dual-polarization IQ modulator modulates each downlink optical carrier based on the analog electrical signal to generate a modulated optical signal carrying space-time coding information. Each modulated optical signal corresponds to a downlink optical carrier of one wavelength.

[0110] The first optical combining module can be used to combine the modulated optical signals in the downlink direction to obtain the first optical signal to be transmitted.

[0111] In this embodiment, the first optical combining module may include a multiplexer (MUX), which can be used to combine multiple modulated optical signals of different wavelengths into a single composite optical signal, namely the first optical signal to be transmitted.

[0112] In addition, the optical line terminal may also include an optical amplifier (Booster) and an optical circulator (Circ.). After the first optical combining module performs optical combining processing on each modulated optical signal, it can output the first optical signal to be transmitted to the optical amplifier. The optical amplifier is used to enhance the power of the first optical signal to be transmitted to compensate for the link loss in the subsequent transmission process. Then, the enhanced first optical signal to be transmitted is coupled to the optical fiber link for transmission through the optical circulator, ensuring that the signal maintains sufficient strength and signal-to-noise ratio during long-distance transmission, thereby improving the stability and reliability of downlink communication.

[0113] The optical circulator can also directionally transmit the optical signal to be processed received in the uplink direction to the second optical splitter module.

[0114] The second beam splitting module can be used to split the optical signal to be processed sent by the optical distribution network in the uplink direction to obtain the demodulated optical signal corresponding to each wavelength.

[0115] In this embodiment, the second beam splitting module may include a wavelength demultiplexer (DeMUX), which can separate multi-wavelength optical signals to be processed according to wavelength, output multiple single-wavelength optical signals to be demodulated, and allocate each optical signal to be demodulated to the corresponding information demodulation module according to the wavelength.

[0116] The information demodulation module can be used to demodulate the optical signal to be demodulated in the uplink direction to obtain uplink data.

[0117] In this embodiment, the information demodulation module includes a photodetector (PD) and a clock data recovery module (CDR). The photodetector can be used to convert the optical signal to be demodulated into an electrical signal, and the clock data recovery module can be used to extract the second user data from the electrical signal and ensure the synchronization and integrity of the data stream.

[0118] In one possible implementation, please refer again. Figure 4 The optical network unit may include a first vector light field control module, a signal processing module, a second laser generation module, and a digital modulation module.

[0119] The first vector light field modulation module can be used to demodulate the first vector light in the downward direction to obtain the first Gaussian beam.

[0120] In this embodiment, the first vector light field modulation module may include an optical antenna, a vortex half-wave plate (VHP), and a collimator. The optical antenna is used to receive the first vector light and achieve spatial coupling. The vortex half-wave plate is used to demodulate the vector light field, converting the information-carrying first vector light into a linearly polarized first Gaussian beam. The collimator is used to shape and collimate the demodulated first Gaussian beam and couple it into a single-mode fiber to ensure efficient conversion and stable reception of the signal during spatial transmission. The vortex half-wave plate in the first vector light field modulation module may be the same as the vortex half-wave plate that generates the first vector light in the optical distribution network.

[0121] The signal processing module can be used to perform photoelectric conversion and digital signal conversion on the first Gaussian beam in the downlink direction to obtain downlink data.

[0122] In this embodiment, the signal processing module may include a coupler (3dB-Coupler), a balanced detector (BPD), a transimpedance amplifier (TIA), an analog-to-digital converter (ADC), and an application-specific integrated circuit (ASIC). After the first vector light field modulation module demodulates the first vector light and couples it to a single-mode fiber, the coupler can be used to mix the first Gaussian beam and the local oscillation light generated by the second laser generation module and output it to the balanced detector. The balanced detector can be used to detect the mixed optical signal and achieve photoelectric conversion through the beat frequency effect to output an electrical signal. The transimpedance amplifier is used to amplify the electrical signal. The analog-to-digital converter can convert the amplified electrical signal into a digital signal. The ASIC can be used to demodulate and decode the digital signal to obtain downlink data.

[0123] The second laser generation module can be used to generate an uplink optical carrier in the uplink direction.

[0124] In this embodiment, the second laser generating module may include a laser (DFB). The laser generated by the laser can be split into two paths by a 3dB beam splitter. One path is used as a local oscillator light input to the coupler for mixing with the first Gaussian beam. The other path is used as an uplink optical carrier, which is loaded with second user data by a digital modulation module and then sent to the optical distribution network.

[0125] The digital modulation module can be used to modulate the uplink optical carrier in the uplink direction to obtain a second optical signal to be transmitted; the second optical signal to be transmitted carries second user data.

[0126] In this embodiment, the digital modulation module may include a Mach-Zehnder (MZM) modulator. The Mach-Zehnder modulator can acquire encoded second user data in the user information processing unit and load it onto the uplink optical carrier to obtain a second optical signal to be transmitted. After obtaining the second optical signal to be transmitted, it can be sent to the first vector optical field modulation module.

[0127] The first vector light field control module can be used to convert the second optical signal to be transmitted into a second vector light in the uplink direction.

[0128] In this embodiment, the second optical signal to be transmitted can be sequentially transmitted to the optical distribution network via the collimator, the vortex half-wave plate and the optical antenna in the first vector optical field modulation module. The collimator can be used to collimate the second optical signal to be transmitted into a parallel beam, the vortex half-wave plate can perform vector state modulation on the beam to generate a second vector light, and the optical antenna can be used to transmit the second vector light to the optical distribution network through a free space channel.

[0129] In one possible implementation, please refer again. Figure 4The light distribution network may include a third beam splitting module, a second vector light field modulation module, and a second beam combining module.

[0130] The third beam splitting module can be used to split the first optical signal to be transmitted in the downlink direction to obtain various optical signals to be modulated.

[0131] In this embodiment, the third beam splitting module may include a beam splitter. After the first optical signal to be transmitted is transmitted to the optical distribution network via a short-distance optical fiber, the beam splitter can split the first optical signal to be transmitted to obtain multiple optical signals to be modulated at different wavelengths. The multiple optical signals to be modulated at different wavelengths correspond to different optical network units. The third beam splitting module can also transmit the optical signals to be modulated to the corresponding second vector optical field control module through polarization-maintaining optical fiber according to the wavelength of the optical signals to be modulated.

[0132] The second vector light field modulation module can be used to convert the optical signal to be modulated into the first vector light in the downward direction.

[0133] In this embodiment, the second vector light field modulation module may include a collimator, a vortex half-wave plate (VHP), and an optical antenna. The optical signal to be modulated can be transmitted to the free space channel in sequence through the collimator, the vortex half-wave plate, and the optical antenna. The collimator can shape the optical signal to be modulated into a parallel beam, the vortex half-wave plate can convert the optical signal to be modulated from linearly polarized light into vector light to obtain the second vector light, and the optical antenna can couple the second vector light to the free space channel and transmit it to the corresponding optical network unit.

[0134] Specifically, vortex half-wave plates can be fabricated using an N-BK7 glass substrate and liquid crystal polymers (LCP) materials. In the LCP layer, the fast axis orientation of the liquid crystal molecules is consistent radially along the substrate and gradually changes angularly. They exhibit the same λ / 2 retardation across the entire device plane. Vortex half-wave plates possess polarization-dependent optical properties, and depending on the polarization state of the incident beam, they can be used to generate vector-polarized beams or vortex beams with a helical phase wavefront.

[0135] When the optical signal to be modulated is linearly polarized light, a vortex half-wave plate can generate a vector-polarized beam, meaning that the polarization direction at each point on the beam's cross-section is a non-uniformly distributed linearly polarized beam. When using an m=1 vortex half-wave plate, if the polarization direction of the incident linearly polarized light is parallel to the 0° fast axis of the m=1 vortex half-wave plate, the emitted beam will be a radially polarized beam. Please refer to [reference needed]. Figure 10a In a radially polarized beam, the linear polarization direction at every point on the cross-section is parallel to the radial direction. If the polarization direction of the incident linearly polarized beam is perpendicular to the 0° fast axis of the m=1 vortex half-wave plate, then the emitted beam is an angularly polarized beam. Please refer to [reference needed]. Figure 10bIn an angularly polarized beam, the linear polarization direction at every point on the cross-section is perpendicular to the radial direction. Therefore, the x-polarized and y-polarized light generated at the optical line terminal can be converted into radial and angular vector light after passing through a vortex half-wave plate, and then transmitted to the free-space channel by the optical antenna.

[0136] The second vector light field modulation module can be used to perform vector light field demodulation processing on the second vector light sent by each optical network unit in the uplink direction to obtain the second Gaussian beam corresponding to each second vector light.

[0137] In this embodiment, when the second vector light field modulation module receives the second vector light sent by multiple optical network units, it can receive the second vector light through an optical antenna and achieve spatial coupling, and demodulate the vector light field through a vortex half-wave plate to convert the information-carrying second vector light into a linearly polarized second Gaussian beam. Then, it can perform beam shaping and collimation on the demodulated second Gaussian beam through a collimator and send it to the second light combining module.

[0138] The second beam combining module can be used to combine each second Gaussian beam in the uplink direction to obtain the optical signal to be processed.

[0139] In this embodiment, the second optical combining module may include a combiner, which can combine multiple second Gaussian beams of different wavelengths into a single multiplexed optical signal to obtain the optical signal to be processed, and send the optical signal to be processed to the optical line terminal through a short-distance optical fiber.

[0140] In summary, the embodiments of this application provide a passive optical network transmission method and a passive optical network system. By using a free-space channel to connect an optical distribution network with multiple optical network units, the passive optical network can avoid the high dependence on optical fiber infrastructure and achieve high-bandwidth, low-latency optical signal transmission without laying optical cables. It is suitable for complex scenarios where optical fiber laying is costly or difficult. In addition, by converting the optical signal into a vector beam, the anti-turbulence capability of the passive optical network system can be effectively improved, while reducing system costs and making information transmission more secure.

[0141] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0142] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A passive optical network transmission method, characterized in that, This invention is applied to a passive optical network system, which includes an optical line terminal (OLT), an optical distribution network (ODN), and multiple optical network units (ONUs); the OLT is connected to the ODN, and the ODN is connected to the multiple ONUs via free-space channels. The method includes: For a downlink optical carrier, the optical line terminal generates a downlink optical carrier and transmits a first optical signal to be transmitted obtained by modulating the downlink optical carrier to the optical distribution network; the first optical signal to be transmitted carries first user data. The optical distribution network converts the first optical signal to be transmitted sent by the optical line terminal into a first vector light, and sends the first vector light to the corresponding optical network unit through the free space channel; The optical network unit receives the first vector light transmitted by the optical distribution network and performs vector optical field demodulation on the first vector light to obtain downlink data; The method further includes: For the uplink optical carrier, the optical network unit modulates the uplink optical carrier to obtain a second optical signal to be transmitted, and transmits the second vector light obtained by converting the second optical signal to be transmitted to the optical distribution network through the free space channel; the second optical signal to be transmitted carries second user data; The optical distribution network receives the second vector light sent by the multiple optical network units respectively, performs vector optical field demodulation and beam combining on each second vector light, and sends the resulting optical signal to be processed to the optical line terminal. The optical line terminal receives the optical signal to be processed sent by the optical distribution network and demodulates the optical signal to obtain uplink data.

2. The passive optical network transmission method according to claim 1, characterized in that, The optical line terminal includes a first laser generating module, a first beam splitting module, a signal modulation module, and a first beam combining module; The steps of generating a downlink optical carrier at the optical line terminal and transmitting a first optical signal to be transmitted by modulating the downlink optical carrier to the optical distribution network include: An initial optical signal is generated by the first laser generation module; the initial optical signal is a multi-wavelength laser. The initial optical signal is split by the first beam splitting module to obtain multiple downlink optical carriers corresponding to different wavelengths. The downlink optical carriers are modulated by the signal modulation module to obtain each modulated optical signal, and the modulated optical signal carries first user data using space-time coding. The first light combining module performs light combining processing on each of the modulated optical signals to obtain a first optical signal to be transmitted, and then sends the first optical signal to be transmitted to the optical distribution network.

3. The passive optical network transmission method according to claim 2, characterized in that, The steps of modulating each downlink optical carrier using the signal modulation module to obtain each modulated optical signal include: Obtain first user data; The first user data is converted into downlink transmission symbols, and the downlink transmission symbols are grouped. Based on the grouping results, the downlink transmission symbols are subjected to space-time coding to obtain coded symbols; The encoded symbols are input to the modulation module through a first transmission dimension and a second transmission dimension; the first transmission dimension is the X-polarization state, and the second transmission dimension is the Y-polarization state. The coded symbols are modulated onto each downlink optical carrier by the modulation module to obtain each modulated optical signal.

4. The passive optical network transmission method according to claim 1, characterized in that, The optical network unit includes a second laser generation module, a digital modulation module, and a first vector light field control module; The steps of the optical network unit modulating the uplink optical carrier to obtain a second optical signal to be transmitted, and converting the second optical signal to be transmitted into a second vector light, and transmitting the second vector light to the optical distribution network through the free space channel include: The uplink optical carrier is generated by the second laser generation module; The uplink optical carrier is modulated by the digital modulation module to obtain the second optical signal to be transmitted; The second optical signal to be transmitted is converted into a second vector light by the first vector light field modulation module, and the second vector light is transmitted to the optical distribution network through the free space channel.

5. The passive optical network transmission method according to claim 4, characterized in that, The step of obtaining the second optical signal to be transmitted by modulating the uplink optical carrier through the digital modulation module includes: Obtain second user data; The second user data is subjected to source coding and channel coding to obtain coded data; The second optical signal to be transmitted is obtained by the digital modulation module performing BPSK code modulation based on the encoded data and the uplink optical carrier.

6. The passive optical network transmission method according to claim 4, characterized in that, The optical network unit also includes a signal processing module; The step of the optical network unit receiving the first vector light transmitted by the optical distribution network and performing vector optical field demodulation on the first vector light to obtain downlink data includes: The first vector light transmitted by the light distribution network is received by the first vector light field modulation module, and the first vector light is demodulated by vector light field to obtain the first Gaussian beam. The signal processing module performs photoelectric conversion and digital signal conversion on the first Gaussian beam to obtain downlink data.

7. A passive optical network system, characterized in that, The passive optical network system includes an optical line terminal, an optical distribution network, and multiple optical network units; The optical line terminal is connected to the optical distribution network, and the optical distribution network is connected to multiple optical network units respectively through free space channels; The optical line terminal is used to generate a downlink optical carrier in the downlink direction and transmit a first optical signal to be transmitted obtained by modulating the downlink optical carrier to the optical distribution network; the first optical signal to be transmitted carries first user data. The optical distribution network is used to convert the first optical signal to be transmitted sent by the optical line terminal into a first vector light in the downlink direction, and to send the first vector light to the corresponding optical network unit through the free space channel; The optical network unit is used to receive the first vector light transmitted by the optical distribution network in the downlink direction, and to perform vector optical field demodulation on the first vector light to obtain downlink data; The optical network unit is used to modulate a second optical signal to be transmitted in the uplink direction based on the second user data and the uplink optical carrier, and to transmit the second vector light obtained by converting the second optical signal to be transmitted to the optical distribution network through the free space channel. The optical distribution network is used to receive the second vector light transmitted by multiple optical network units in the uplink direction, and to perform vector optical field demodulation and beam combining on each second vector light, and to send the resulting optical signal to be processed to the optical line terminal. The optical line terminal is used to receive the optical signal to be processed sent by the optical distribution network in the uplink direction, and to demodulate the optical signal to be processed to obtain uplink data.

8. The passive optical network system according to claim 7, characterized in that, The optical line terminal includes a first laser generating module, a first beam splitting module, a signal modulation module, a first beam combining module, a second beam splitting module, and an information demodulation module; The first laser generating module is used to generate an initial optical signal in the downward direction; the initial optical signal is a multi-wavelength laser. The first beam splitting module is used to perform beam splitting processing on the initial optical signal in the downlink direction to obtain downlink optical carriers corresponding to each wavelength; The signal modulation module is used to modulate each of the downlink optical carriers in the downlink direction to obtain each modulated optical signal, and the modulated optical signal carries first user data using space-time coding. The first optical combining module is used to perform optical combining processing on each of the modulated optical signals in the downlink direction to obtain a first optical signal to be transmitted; The second beam splitting module is used to perform beam splitting processing on the optical signal to be processed sent by the optical distribution network in the uplink direction to obtain the optical signal to be demodulated corresponding to each wavelength; The information demodulation module is used to demodulate the optical signal to be demodulated in the uplink direction to obtain uplink data.

9. The passive optical network system according to claim 7, characterized in that, The optical network unit includes a first vector light field modulation module, a signal processing module, a second laser generation module, and a digital modulation module; The first vector light field modulation module is used to demodulate the first vector light field in the downward direction to obtain a first Gaussian beam; The signal processing module is used to perform photoelectric conversion and digital signal conversion processing on the first Gaussian beam in the down direction to obtain downlink data; The second laser generating module is used to generate an uplink optical carrier in the uplink direction; The digital modulation module is used to modulate the uplink optical carrier in the uplink direction to obtain a second optical signal to be transmitted; the second optical signal to be transmitted carries second user data; The first vector light field modulation module is used to convert the second optical signal to be transmitted into a second vector light in the uplink direction.

10. The passive optical network system according to claim 7, characterized in that, The light distribution network includes a third beam splitting module, a second vector light field modulation module, and a second beam combining module; The third beam splitting module is used to perform beam splitting processing on the first optical signal to be transmitted in the downlink direction to obtain each optical signal to be modulated. The second vector light field modulation module is used to convert the optical signal to be modulated into a first vector light in the downlink direction; The second vector light field modulation module is used to perform vector light field demodulation processing on the second vector light sent by each of the optical network units in the uplink direction to obtain the second Gaussian beam corresponding to each of the second vector lights; The second beam combining module is used to combine each of the second Gaussian beams in the upward direction to obtain the optical signal to be processed.

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