Passive optical network system

Abstract

The invention provides a passive optical network system, relates to the field of optical communication, and can solve the problem of crosstalk between two optical signals. The system comprises a first optical line terminal, a second optical line terminal, a wavelength division multiplexer, a first power beam splitter, a first optical network unit and a second optical network unit. According to the invention, the optical signals with different light intensities are generated at the first optical line terminal and the second optical line terminal, the first optical signal is determined based on the light intensity in the first optical network unit, and the crosstalk problem between the two optical signals can be eliminated based on the selection of the light intensity in the first optical network unit; the optical signals with different wavelengths are generated at the first optical line terminal and the second optical line terminal, the second optical signal is determined based on the wavelength in the second optical network unit, and the crosstalk problem between the two optical signals can be eliminated based on wavelength selection in the second optical network unit.

Description

Technical Field

[0001] The present application relates to the field of optical communications, and in particular to a passive optical network system. Background Art

[0002] As users' demand for bandwidth grows, passive optical networks (PONs) need to provide higher downstream rates to meet users' demand for bandwidth. Considering the construction cost requirements, the most common solution is to upgrade PON, that is, to add optical line terminals (OLTs) and optical network units (ONUs) without changing the original deployed PON, that is, the original downstream signals and the newly added downstream signals must be transmitted in the same upgraded PON.

[0003] In order to achieve a higher downstream rate in the upgraded PON, wavelength division multiplexing technology is usually used to couple the original downstream signal with the newly added downstream signal to increase the downstream rate.

[0004] However, in the original PON, the coupled original downstream signal and the newly added downstream signal cannot be separated, which will cause crosstalk between the signals. Summary of the invention

[0005] The present application provides a passive optical network system, which can solve the crosstalk problem caused by coupling between the original downstream signal and the newly added downstream signal in the original PON.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a passive optical network system, comprising: a first optical line terminal, a second optical line terminal, a wavelength division multiplexer, a first power beam splitter, a first optical network unit, and a second optical network unit, wherein the output end of the first optical line terminal and the output end of the second optical line terminal are respectively connected to the input end optical fiber of the wavelength division multiplexer, the output end of the wavelength division multiplexer is connected to the input end optical fiber of the first power beam splitter, and the output end of the first power beam splitter is respectively connected to the input end optical fiber of the first optical network unit and the input end optical fiber of the second optical network unit; wherein:

[0008] The first optical line terminal is used to generate a first optical signal of a first wavelength and a first light intensity, and transmit the first optical signal to the wavelength division multiplexer; the second optical line terminal is used to generate a second optical signal of a second wavelength and a second light intensity, and transmit the second optical signal to the wavelength division multiplexer;

[0009] The wavelength division multiplexer is used to couple the first optical signal with the second optical signal, and transmit the coupled target optical signal to the first power beam splitter;

[0010] The first power beam splitter is used to transmit the target optical signal to the first optical network unit and the second optical network unit respectively;

[0011] The first optical network unit is used to determine the first optical signal from the target optical signal based on the light intensity of the optical signal; the second optical network unit is used to determine the second optical signal from the target optical signal based on the wavelength of the optical signal.

[0012] In combination with the first aspect above, in a possible implementation, the first optical line terminal includes a first laser diode and a first Mach-Zehnder modulator, the output end of the first laser diode is optically connected to the input end of the first Mach-Zehnder modulator, and the output end of the first Mach-Zehnder modulator is optically connected to the input end of the wavelength division multiplexer, wherein:

[0013] The first laser diode is used to generate an optical signal of a first wavelength; the first Mach-Zehnder modulator is used to modulate the optical signal of the first wavelength based on the amplitude shift keying technology to obtain a first optical signal of a first wavelength and a first light intensity, and load the data information to be transmitted into the first optical signal;

[0014] The second optical line terminal includes a second laser diode and a phase modulator, the output end of the second laser diode is optically connected to the input end of the phase modulator, and the output end of the phase modulator is optically connected to the input end of the wavelength division multiplexer, wherein:

[0015] The second laser diode is used to generate an optical signal of a second wavelength; the phase modulator is used to modulate the optical signal of the second wavelength based on the orthogonal modulation technology to obtain a second optical signal of a second wavelength and a second light intensity, and load the data information to be transmitted into the second optical signal.

[0016] In combination with the first aspect above, in a possible implementation, the phase modulator is used to modulate the optical signal of the second wavelength based on the orthogonal modulation technology to obtain a second optical signal of the second wavelength and the second light intensity, including:

[0017] The phase modulator is used to modulate the optical signal of the second wavelength based on the multi-order differential phase shift keying technology to obtain a second optical signal of the second wavelength and the second light intensity.

[0018] In combination with the first aspect above, in a possible implementation manner, the second optical network unit includes an optical filter, an input end of the optical filter is optically connected to an output end of the first power beam splitter, wherein:

[0019] The optical filter is used to filter the optical signals of other wavelengths except the second wavelength based on the wavelength of the optical signal to obtain the second optical signal;

[0020] The first optical network unit includes a photoelectric detector, the input end of the photoelectric detector is connected to the output end of the first power beam splitter by an optical fiber, wherein:

[0021] The photoelectric detector is used to filter the second optical signal greater than a preset light intensity threshold based on the light intensity of the optical signal, obtain the first optical signal, and acquire the data information carried in the first optical signal.

[0022] In combination with the first aspect above, in a possible implementation, the second optical network unit further includes a second power beam splitter, a plurality of delay interferometers and a photodetector, the input end of the second power beam splitter is optically connected to the output end of the optical filter, the output end of the second power beam splitter is optically connected to the input end of the plurality of delay interferometers, and the output ends of the plurality of delay interferometers are optically connected to the photodetector, wherein:

[0023] The second power beam splitter is used to split the second optical signal determined by the optical filter into multiple optical signals, and transmit the multiple optical signals to multiple delay interferometers respectively; the multiple delay interferometers are used to adjust the phase and delay of the optical signal transmitted through the second power beam splitter to obtain the adjusted optical signal; the photodetector is used to obtain the data information carried in the adjusted optical signal.

[0024] In combination with the first aspect above, in a possible implementation, the second optical network unit further includes a third power beam splitter and a second Mach-Zehnder modulator, the input end of the third power beam splitter is optically connected to the output end of the optical filter, and the output end of the third power beam splitter is optically connected to the input end of the second power beam splitter and the input end of the second Mach-Zehnder modulator, respectively, wherein:

[0025] The third power splitter is used to split the second optical signal determined by the optical filter into two optical signals, transmit one optical signal to the second Mach-Zehnder modulator, and transmit the other optical signal to the second power splitter; the second Mach-Zehnder modulator is used to load the data information to be transmitted into the optical signal transmitted by the third power splitter, so as to transmit the optical signal from the second optical network unit to the second optical line terminal.

[0026] In combination with the first aspect, in a possible implementation, the second optical network unit further includes a first circulator, and an input end of the first circulator is respectively connected to an output end of the optical filter and an output end of the second Mach-Zehnder modulator by optical fiber, wherein:

[0027] The first circulator is used to control the transmission direction of the optical signal from the second optical line terminal to the second optical network unit, or from the second optical network unit to the second optical line terminal.

[0028] In combination with the above first aspect, in a possible implementation, the second optical line terminal further includes a photodetector, which is used to receive an optical signal transmitted from the second optical network unit to the second optical line terminal and obtain data information carried in the optical signal.

[0029] In combination with the first aspect above, in a possible implementation, the second optical line terminal further includes a second circulator and a dispersion compensating optical fiber, the input end of the second circulator is connected to the input end of the wavelength division multiplexer through the dispersion compensating optical fiber, and the output end of the second circulator is connected to the photodetector optical fiber, wherein:

[0030] The second circulator is used to control the transmission direction of the optical signal from the second optical line terminal to the second optical network unit, or from the second optical network unit to the second optical line terminal; the dispersion compensating optical fiber is used to compensate for the dispersion generated during the transmission of the optical signal from the second optical line terminal to the second optical network unit, or from the second optical network unit to the second optical line terminal.

[0031] In combination with the first aspect above, in a possible implementation, the system further includes a variable optical attenuator, the input end of the variable optical attenuator is optically connected to the output end of the wavelength division multiplexer, and the output end of the variable optical attenuator is optically connected to the input end of the first power beam splitter, wherein:

[0032] The variable optical attenuator is used to control the intensity of the target optical signal.

[0033] In this application, the name of the above passive optical network system does not limit the device or functional module itself. In actual implementation, these devices or functional modules may appear with other names. As long as the functions of each device or functional module are similar to those of this application, they fall within the scope of the claims of this application and their equivalent technologies.

[0034] These and other aspects of the present application will become more apparent from the following description.

[0035] The above scheme brings at least the following beneficial effects: the passive optical network system provided by the present application can realize the coupling of optical signals of two different wavelengths through a wavelength division multiplexer, realize the coexistence of two optical signals in a passive optical network system, and thus realize the transmission of optical signals of two wavelengths in a passive optical network system. In addition, by generating a first optical signal of a first optical intensity at a first optical line terminal and generating a second optical signal of a second optical intensity at a second optical line terminal, the first optical signal is determined based on the intensity of the optical signal in the first optical network unit, and the two optical signals can be separated based on the intensity of the optical signal in the first optical network unit by generating optical signals of different optical intensities, and the optical signal required by the user can be retained in the first optical network unit, and the crosstalk problem generated between the two optical signals can be eliminated based on the selection of the optical intensity in the first optical network unit. By generating a first optical signal of a first wavelength at a first optical line terminal and generating a second optical signal of a second wavelength at a second optical line terminal, the second optical signal is determined based on the wavelength of the optical signal in the second optical network unit. By generating optical signals of different wavelengths, the two optical signals can be separated based on the wavelength of the optical signal in the second optical network unit, and the optical signal required by the user can be retained in the second optical network unit. Based on the selection of wavelength in the second optical network unit, the crosstalk problem between the two optical signals can be eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of a passive optical network system provided in an embodiment of the present application;

[0037] Figure 2 A schematic diagram of another passive optical network system provided in an embodiment of the present application;

[0038] Figure 3 A schematic diagram of another passive optical network system provided in an embodiment of the present application;

[0039] Figure 4 A schematic diagram of another passive optical network system provided in an embodiment of the present application;

[0040] Figure 5 A schematic diagram of another passive optical network system provided in an embodiment of the present application;

[0041] Figure 6 A flowchart of optical signal transmission in a passive optical network based on multi-order differential phase shift keying technology provided in an embodiment of the present application;

[0042] Figure 7 A schematic diagram of modulating an optical signal of a second wavelength based on sixth-order DPSK provided in an embodiment of the present application;

[0043] Figure 8 A schematic diagram of another passive optical network system provided in an embodiment of the present application;

[0044] Fig. 9 A schematic diagram of another passive optical network system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] The term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0047] The terms "first" and "second" and the like in the specification and drawings of this application are used to distinguish different objects, or to distinguish different processing of the same object, rather than to describe a specific order of objects.

[0048] In addition, the terms "including" and "having" and any variations thereof mentioned in the description of the present application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include other steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0049] It should be noted that, in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0050] In the description of the present application, unless otherwise specified, “plurality” means two or more.

[0051] The following explains the terms involved in the embodiments of the present application to facilitate the reader's understanding.

[0052] (1) Passive optical network (PON) is a pure medium network that uses optical fiber as the transmission medium. It includes optical line terminal (OLT), optical network unit (ONU), optical distribution network (ODN), etc. It can realize signal transmission through passive devices and has the advantages of large bandwidth, wide coverage, and easy maintenance. It has become the ultimate solution for fiber-to-the-home.

[0053] (2) OLT is a terminal device used to connect to the optical fiber trunk line and can send data information to the ONU in a broadcast manner.

[0054] (3) ODN is a fiber-to-the-home (FTTH) optical cable network based on PON equipment, which mainly provides an optical signal transmission channel between OLT and ONU.

[0055] (4) ONU is a terminal device connected through optical fiber and can provide multiple service interfaces to users.

[0056] (5) Wavelength division multiplexing (WDM) is a technology that transmits two or more wavelengths of optical signals simultaneously in the same optical fiber. It can combine optical signals of different wavelengths at the transmitting end and couple them into the same optical fiber for transmission, thereby improving the efficiency of data transmission.

[0057] As users' demand for bandwidth grows, PON needs to provide higher transmission rates to meet users' demand for bandwidth. To achieve higher transmission rates of PON, operators are developing from 10G PON to 50G PON and even 100G PON, that is, from 10Gb / s transmission rate to 50Gb / s and even 100Gb / s transmission rate. In the process of achieving 50Gb / s or 100Gb / s transmission rate based on 10G-level transmitters and receivers in the current network, new equipment will need to be added or new technologies will be adopted, which will increase the complexity of operation and cost expenditure.

[0058] It should be noted that, generally, a signal transmitted from the OLT to the ONU is called a downstream signal, and a signal transmitted from the ONU to the OLT is called an upstream signal.

[0059] In order to increase the transmission rate of the signal, multi-order modulation methods such as multi-order pulse amplitude modulation are currently used. However, when this method is used, the signal is easily affected by noise, resulting in a large sensitivity loss in the received signal. In addition, in addition to increasing the bit rate per wavelength to increase the transmission rate, the optical signal can also be coupled through WDM to increase the transmission rate of the downstream signal. Currently, WDM technology has been applied to the next generation passive optical network 2 (NGPON2) and 50G Ethernet passive optical network (EPON). In a WDM-based PON, the upstream signal transmitted by the ONU needs to be transmitted using optical signals of different wavelengths. Since one model of ONU can only be used to transmit an optical signal of one wavelength, this will lead to an "inventory problem", that is, different models of ONUs need to be used in a PON to transmit optical signals of different wavelengths. To this end, multiple standard production lines must be established, which will greatly increase the complexity and cost of the PON. In order to enable the transmission of optical signals of non-specific wavelengths in the same ONU, that is, to realize a transparent ONU, upstream remodulation is usually used to eliminate the ONU's dependence on wavelength.

[0060] In addition, from the perspective of PON construction cost, the main construction cost of PON comes from ODN, of which the construction cost of ODN accounts for nearly 80% of the total cost. In order to improve the utilization rate of the deployed ODN in the existing PON and avoid rebuilding the ODN, smooth upgrade is the best upgrade method in the process of upgrading from the original PON to the next generation PON, that is, adding OLT and ONU without changing the original deployment. In the smooth upgrade process of PON, the newly added OLT and ONU need to be directly added to the deployed ODN, and share the existing optical fiber facilities with the OLT and ONU in the original PON. The newly added OLT and ONU need to coexist with the OLT and ONU in the original PON in the upgraded PON until all users using the original PON in the network are upgraded to use the new network. The wavelengths of the optical signals used for transmission in the newly added OLT and the original OLT are different, that is, the original optical signal and the newly added optical signal must be transmitted in the same upgraded PON. In order to achieve the separation of the optical signals of the two wavelengths at the ONU, the separation of the optical signals can be achieved through an optical filter or a wavelength division multiplexer. Although the newly added ONU can be equipped with an optical filter or a wavelength division multiplexer to separate the two optical signals, the original ONU is not equipped with an optical filter or a wavelength division multiplexer. Installing an optical filter or a wavelength division multiplexer in the original ONU will bring additional modification costs, that is, the separation of the two wavelength optical signals cannot be achieved in the original ONU. In the original ONU, when the receiver receives a signal with two wavelengths of optical signals coexisting, crosstalk between the signals will occur, affecting the user experience.

[0061] The passive optical network system provided by the present application can realize the coupling of two optical signals of different wavelengths through a wavelength division multiplexer, realize the coexistence of two optical signals in a passive optical network system, and thus realize the transmission of optical signals of two wavelengths in a passive optical network system. In addition, by generating a first optical signal of a first optical intensity at a first optical line terminal and generating a second optical signal of a second optical intensity at a second optical line terminal, the first optical signal is determined based on the intensity of the optical signal in the first optical network unit, and the two optical signals can be separated based on the intensity of the optical signal in the first optical network unit by generating optical signals of different optical intensities, and the optical signal required by the user can be retained in the first optical network unit, and the crosstalk problem generated between the two optical signals can be eliminated based on the selection of the intensity in the first optical network unit. By generating a first optical signal of a first wavelength at a first optical line terminal and generating a second optical signal of a second wavelength at a second optical line terminal, the second optical signal is determined based on the wavelength of the optical signal in the second optical network unit. By generating optical signals of different wavelengths, the two optical signals can be separated based on the wavelength of the optical signal in the second optical network unit, and the optical signal required by the user can be retained in the second optical network unit. Based on the selection of wavelength in the second optical network unit, the crosstalk problem between the two optical signals can be eliminated.

[0062] The system of the embodiment of the present application will be described in detail below with reference to the accompanying drawings.

[0063] Figure 1 A schematic diagram of a passive optical network system provided in an embodiment of the present application. Figure 1 As shown, the passive optical network system includes: a first optical line terminal 101, a second optical line terminal 102, a wavelength division multiplexer 103, a first power splitter 104, a first optical network unit 105 and a second optical network unit 106.

[0064] Among them, the output end of the first optical line terminal 101 and the output end of the second optical line terminal 102 are respectively connected to the input end optical fiber of the wavelength division multiplexer 103, the output end of the wavelength division multiplexer 103 is connected to the input end optical fiber of the first power splitter 104, and the output end of the first power splitter 104 is respectively connected to the input end of the first optical network unit 105 and the input end optical fiber of the second optical network unit 106.

[0065] The first optical line terminal 101 is used to generate a first optical signal with a first wavelength and a first light intensity, and transmit the first optical signal to the wavelength division multiplexer 103 .

[0066] In a possible implementation, the first optical line terminal 101 includes a first laser diode 1011 and a first Mach-Zehnder modulator 1012, the output end of the first laser diode 1011 is optically connected to the input end of the first Mach-Zehnder modulator 1012, and the output end of the first Mach-Zehnder modulator 1012 is optically connected to the input end of the wavelength division multiplexer 103.

[0067] Among them, the first laser diode 1011 is used to generate an optical signal of a first wavelength; the first Mach-Zehnder modulator 1012 is used to modulate the optical signal of the first wavelength based on the amplitude shift keying technology to obtain a first optical signal of a first wavelength and a first light intensity, and load the data information to be transmitted into the first optical signal.

[0068] Exemplarily, the data information to be transmitted may be in the form of an electrical signal. Thus, the data information to be transmitted is loaded into the first optical signal by using the first Mach-Zehnder modulator 1012, so that the data information is transmitted from the first optical line terminal 101 to the first optical network unit 105 based on the first optical signal, which can effectively improve the transmission rate of the data information.

[0069] The second optical line terminal 102 is used to generate a second optical signal with a second wavelength and a second optical intensity, and transmit the second optical signal to the wavelength division multiplexer 103 .

[0070] In a possible implementation, the second optical line terminal 102 includes a second laser diode 1021 and a phase modulator 1022 , the output end of the second laser diode 1021 is optically connected to the input end of the phase modulator 1022 , and the output end of the phase modulator 1022 is optically connected to the input end of the wavelength division multiplexer 103 .

[0071] The second laser diode 1021 is used to generate an optical signal of a second wavelength; the phase modulator 1022 is used to modulate the optical signal of the second wavelength based on the orthogonal modulation technology to obtain a second optical signal of a second wavelength and a second light intensity, and load the data information to be transmitted into the second optical signal. Exemplarily, the number of phase modulators 1022 can be multiple, such as Figure 1 Three phase modulators 1022 are shown.

[0072] In this way, the data information to be transmitted is loaded into the second optical signal by using the phase modulator 1022, so that the data information is transmitted from the second optical line terminal 102 to the second optical network unit 106 based on the second optical signal, which can effectively improve the transmission rate of the data information. It should be noted that the data information loaded by the first optical signal and the data information loaded by the second optical signal can be the same or different, and the embodiment of the present application is not limited to this.

[0073] In a possible implementation, the orthogonal modulation technology may be differential phase shift keying (DPSK), polarization shift keying (PolSK), frequency shift keying (FSK), or the like.

[0074] Exemplarily, taking the orthogonal modulation technology as differential phase shift keying technology as an example, the phase modulator 1022 is used to modulate the optical signal of the second wavelength based on the multi-order differential phase shift keying technology to obtain a second optical signal of the second wavelength and the second light intensity.

[0075] In this way, the first optical line terminal 101 can generate an optical signal of a first wavelength and a first optical intensity, and the second optical line terminal 102 can generate an optical signal of a second wavelength and a second optical intensity. It is possible to generate two optical signals of different wavelengths in a passive optical network system, which is convenient for the subsequent separation of the two optical signals based on wavelength. It is also possible to generate two optical signals of different optical intensities in a passive optical network system, which is convenient for the subsequent separation of the two optical signals based on optical intensity. It is also possible to load data information to be transmitted onto the optical signal, thereby improving the rate of information transmission.

[0076] The wavelength division multiplexer 103 is used to couple the first optical signal with the second optical signal, and transmit the coupled target optical signal to the first power beam splitter 104 .

[0077] The first power beam splitter 104 is used to transmit the target optical signal to the first optical network unit 105 and the second optical network unit 106 respectively.

[0078] The first optical network unit 105 is used to determine the first optical signal from the target optical signal based on the optical intensity of the optical signal.

[0079] In a possible implementation, the first optical network unit 105 includes a photodetector 1051 , and an input end of the photodetector 1051 is optically connected to an output end of the first power beam splitter 104 .

[0080] The photodetector 1051 is used to filter the second optical signal greater than a preset light intensity threshold based on the light intensity of the optical signal, obtain the first optical signal, and acquire the data information carried in the first optical signal.

[0081] The preset light intensity threshold is a fixed threshold value pre-set in the photodetector 1051, such as a light intensity threshold with a larger value, which is used to separate the first light signal with a larger light intensity from the target light signal. In the embodiment of the present application, the light intensity of the first light signal is less than the light intensity of the second light signal, that is, the first light intensity is less than the second light intensity.

[0082] In this way, by setting the photodetector 1051 in the first optical network unit 105, the first optical network unit 105 can separate the two optical signals based on the light intensity of the optical signal. Specifically, based on the preset light intensity threshold set in the photodetector 1051, the first optical signal is determined from the target optical signal, and the separation of the two optical signals based on light intensity is achieved, thereby eliminating the crosstalk generated between the two optical signals and improving the user experience.

[0083] The second optical network unit 106 is used to determine the second optical signal from the target optical signal based on the wavelength of the optical signal.

[0084] In a possible implementation, the second optical network unit 106 includes an optical filter 1061 , and an input end of the optical filter 1061 is optically connected to an output end of the first power beam splitter 104 .

[0085] The optical filter 1061 is used to filter the optical signals of other wavelengths except the second wavelength based on the wavelength of the optical signal to obtain the second optical signal. Exemplarily, the optical filter 1061 may be pre-set with a parameter value of the second wavelength so as to implement the above-mentioned process of filtering the optical signals of other wavelengths except the second wavelength based on the parameter value of the second wavelength.

[0086] In this way, by setting the optical filter 1061 in the second optical network unit 106, the second optical network unit 106 can separate the two optical signals based on the wavelength of the optical signal. Specifically, based on the second wavelength set in the optical filter 1061, optical signals of other wavelengths except the second wavelength are filtered from the target optical signal to achieve wavelength-based separation of the two optical signals, thereby eliminating the crosstalk generated between the two optical signals and improving the user experience.

[0087] The passive optical network system provided by the present application can realize the coupling of two optical signals of different wavelengths through a wavelength division multiplexer, realize the coexistence of two optical signals in a passive optical network system, and thus realize the transmission of optical signals of two wavelengths in a passive optical network system. In addition, by generating a first optical signal of a first optical intensity at a first optical line terminal and generating a second optical signal of a second optical intensity at a second optical line terminal, the first optical signal is determined based on the intensity of the optical signal in the first optical network unit, and the two optical signals can be separated based on the intensity of the optical signal in the first optical network unit by generating optical signals of different optical intensities, and the optical signal required by the user can be retained in the first optical network unit, and the crosstalk problem generated between the two optical signals can be eliminated based on the selection of the intensity in the first optical network unit. By generating a first optical signal of a first wavelength at a first optical line terminal and generating a second optical signal of a second wavelength at a second optical line terminal, the second optical signal is determined based on the wavelength of the optical signal in the second optical network unit. By generating optical signals of different wavelengths, the two optical signals can be separated based on the wavelength of the optical signal in the second optical network unit, and the optical signal required by the user can be retained in the second optical network unit. Based on the selection of wavelength in the second optical network unit, the crosstalk problem between the two optical signals can be eliminated.

[0088] Figure 2 Another passive optical network system schematic diagram provided in the embodiment of the present application. Figure 2 As shown, in the system, the second optical network unit 106 further includes a second power beam splitter 1062, a plurality of time delay interferometers 1063 and a photodetector 1064. The input end of the second power beam splitter 1062 is optically connected to the output end of the optical filter 1061, the output end of the second power beam splitter 1062 is optically connected to the input ends of the plurality of time delay interferometers 1063, and the output ends of the plurality of time delay interferometers 1063 are optically connected to the photodetector 1064, respectively.

[0089] The second power beam splitter 1062 is used to split the second optical signal determined by the optical filter 1061 into multiple optical signals, and transmit the multiple optical signals to multiple delay interferometers 1063. The multiple delay interferometers 1063 are used to adjust the phase and delay of the optical signal transmitted by the second power beam splitter 1062 to obtain the adjusted optical signal. The photodetector 1064 is used to receive the adjusted optical signal and obtain the data information carried in the adjusted optical signal.

[0090] Exemplarily, the number of the multiple delay interferometers 1063 may be three, such as Figure 2 Three delay interferometers 1063 are shown. Among them, one delay interferometer 1063 can be correspondingly provided with two photodetectors 1064.

[0091] In this way, by setting up multiple delay interferometers 1063 in the second optical network unit 106, it is possible to demodulate the second optical signal modulated in the second optical line terminal 102 by adjusting the phase and delay of the optical signal, and by setting up a photodetector 1064, it is possible to receive the second optical signal transmitted from the second optical line terminal 102 to the second optical network unit 106, and obtain the data information carried by the optical signal therefrom to meet the needs of users.

[0092] Figure 3 Another passive optical network system schematic diagram provided in the embodiment of the present application. Figure 3 As shown, the second optical network unit 106 in the system also includes a third power splitter 1065 and a second Mach-Zehnder modulator 1066, the input end of the third power splitter 1065 is optically connected to the output end of the optical filter 1061, and the output end of the third power splitter 1065 is optically connected to the input end of the second power splitter 1062 and the input end of the second Mach-Zehnder modulator 1066 respectively.

[0093] Among them, the third power splitter 1065 is used to split the second optical signal determined by the optical filter 1061 into two optical signals, transmit one optical signal to the second Mach-Zehnder modulator 1066, and transmit the other optical signal to the second power splitter 1062; the second Mach-Zehnder modulator 1066 is used to load the data information to be transmitted into the optical signal transmitted by the third power splitter 1065, so as to transmit the optical signal from the second optical network unit 106 to the second optical line terminal 102.

[0094] In this way, the optical signal is divided into two signals through the third power splitter, and the second optical signal can be provided for the transmission signal transmitted from the second optical network unit to the second optical line terminal, that is, the uplink signal. After the uplink signal is loaded into the second optical signal, there is no need to provide an additional light source for the uplink signal, which can simplify the structure of the passive optical network system and reduce costs. In addition, the uplink signal can be transmitted in the second optical network unit based on the received second optical signal, and there is no specific requirement for the wavelength of the second optical signal, that is, a transparent ONU is realized.

[0095] like Figure 3 As shown, the second optical network unit 106 in the system also includes a first circulator 1067, the input end of the first circulator 1067 is respectively connected to the output end of the optical filter 1061 and the output end of the second Mach-Zehnder modulator 1066 by optical fiber, and the output end of the first circulator 1067 is connected to the input end of the third power splitter 1065 by optical fiber.

[0096] The first circulator 1067 is used to control the transmission direction of the optical signal from the second optical line terminal 102 to the second optical network unit 106 , or from the second optical network unit 106 to the second optical line terminal 102 .

[0097] like Figure 3 As shown, the wavelength of the optical signal generated by the second laser diode 1021 is represented by λ2, and the optical signal with the wavelength λ2 can be transmitted in two directions at the first circulator 1067.

[0098] In this way, the second optical network unit 106 can receive the optical signal transmitted from the second optical line terminal 102, and can also transmit the optical signal from the second optical network unit 106 to the second optical line terminal 102, so that information transmission in two directions can be realized to meet user needs.

[0099] Figure 4 Another passive optical network system schematic diagram provided in the embodiment of the present application. Figure 4 As shown, the second optical line terminal 102 in the system further includes a photodetector 1023, and the photodetector 1023 is connected to the input optical fiber of the wavelength division multiplexer 103, wherein:

[0100] The photodetector 1023 is used to receive the optical signal transmitted from the second optical network unit 106 to the second optical line terminal 102, and obtain the data information carried in the optical signal.

[0101] It should be noted that, in the first optical network unit 105, the data information acquired by the photodetector 1051 is data information transmitted from the first optical line terminal 101 to the first optical network unit 105. In the second optical network unit 106, the data information acquired by the photodetector 1064 is data information transmitted from the second optical line terminal 102 to the second optical network unit 106. In the second optical line terminal 102, the data information acquired by the photodetector 1023 is data information transmitted from the second optical network unit 106 to the second optical line terminal 102.

[0102] In this way, the optical signal transmitted from the second optical network unit 106 to the second optical line terminal 102 can be received, thereby realizing the transmission of information in the communication network.

[0103] like Figure 4 As shown, the second optical line terminal 102 also includes a second circulator 1024 and a dispersion compensating optical fiber 1025. The input end of the second circulator 1024 is connected to the input end of the wavelength division multiplexer 103 through the dispersion compensating optical fiber 1025, and is connected to the output end optical fiber of the phase modulator 1022. The output end of the second circulator 1024 is connected to the photodetector 1023 optical fiber.

[0104] Among them, the second circulator 1024 is used to control the transmission direction of the optical signal from the second optical line terminal 102 to the second optical network unit 106, or from the second optical network unit 106 to the second optical line terminal 102; the dispersion compensating optical fiber 1025 is used to compensate for the dispersion generated during the transmission of the optical signal from the second optical line terminal 102 to the second optical network unit 106, or from the second optical network unit 106 to the second optical line terminal 102.

[0105] like Figure 4 As shown, the wavelength of the optical signal generated by the second laser diode 1021 is represented by λ2, and the optical signal with the wavelength λ2 can be transmitted in two directions at the second circulator 1024.

[0106] In this way, the second optical line terminal 102 can receive the optical signal transmitted from the second optical network unit 106, and can also transmit the optical signal from the second optical line terminal 102 to the second optical network unit 106, so that information transmission in two directions can be realized to meet user needs.

[0107] Figure 5 Another passive optical network system schematic diagram provided in the embodiment of the present application. Figure 5 As shown, the system further includes a variable optical attenuator 107 , the input end of the variable optical attenuator 107 is optically connected to the output end of the wavelength division multiplexer 103 , and the output end of the variable optical attenuator 107 is optically connected to the input end of the first power beam splitter 104 .

[0108] The variable optical attenuator 107 is used to control the light intensity of the target optical signal.

[0109] In this way, during the optical signal transmission process, the intensity of the optical signal changes due to channel loss, modulation, etc., and the intensity of the optical signal can be adjusted by the variable optical attenuator 107 to ensure the normal transmission of the optical signal, and the normal optical signal can be received at the receiving end.

[0110] It should be noted that in order to detect the bit error rate of the received transmission information in actual situations, a bit error rate analyzer is provided in the passive optical network system, and the input end of the bit error rate analyzer is connected to the output end of the photodetector through a wire.

[0111] The passive optical network system provided by the present application can realize the coupling of two optical signals of different wavelengths through a wavelength division multiplexer, realize the coexistence of two optical signals in a passive optical network system, and thus realize the transmission of optical signals of two wavelengths in a passive optical network system. In addition, by generating a first optical signal of a first optical intensity at a first optical line terminal and generating a second optical signal of a second optical intensity at a second optical line terminal, the first optical signal is determined based on the intensity of the optical signal in the first optical network unit, and the two optical signals can be separated based on the intensity of the optical signal in the first optical network unit by generating optical signals of different optical intensities, and the optical signal required by the user can be retained in the first optical network unit, and the crosstalk problem generated between the two optical signals can be eliminated based on the selection of the intensity in the first optical network unit. By generating a first optical signal of a first wavelength at a first optical line terminal and generating a second optical signal of a second wavelength at a second optical line terminal, the second optical signal is determined based on the wavelength of the optical signal in the second optical network unit. By generating optical signals of different wavelengths, the two optical signals can be separated based on the wavelength of the optical signal in the second optical network unit, and the optical signal required by the user can be retained in the second optical network unit. Based on the selection of wavelength in the second optical network unit, the crosstalk problem between the two optical signals can be eliminated.

[0112] The passive optical network system provided by the present application divides the optical signal into two signals through a third power beam splitter, and can provide a second optical signal for the transmission signal transmitted from the second optical network unit to the second optical line terminal, and after the uplink signal is loaded into the second optical signal, it is not necessary to provide an additional light source for the uplink signal, which can simplify the structure of the passive optical network system and reduce costs. In addition, the uplink signal can be transmitted based on the received second optical signal in the second optical network unit, and there is no specific requirement for the wavelength of the second optical signal, that is, a transparent ONU is realized. By phase modulating the optical signal, the phase angles of the optical signal transmitted from the second optical line terminal to the second optical network unit and the optical signal transmitted from the second optical network unit to the second optical line terminal can be different, thereby avoiding crosstalk between optical signals of different propagation directions transmitted in the same optical fiber. And through multi-order DPSK, it is possible to realize that the code element carries more information, thereby realizing high-speed transmission of information.

[0113] like Figure 6 As shown, Figure 6 A flowchart of optical signal transmission in a passive optical network based on multi-order differential phase shift keying technology provided in an embodiment of the present application is applied to Figure 1 In the passive optical network system shown in FIG. 1 , the process includes the following steps:

[0114] S601. In a passive optical network system, three pseudo-random binary sequences PRBS1, PRBS2, and PRBS3 are generated based on MATLAB.

[0115] Among them, PRBS1 is applied to the first optical line terminal, PRBS2 is applied to the second optical line terminal, and PRBS3 is applied to the second optical network unit.

[0116] In this way, by generating a pseudo-random binary sequence, it is possible to facilitate the subsequent testing of the bit error rate in the subsequent transmission process and to verify the transmission performance of the system.

[0117] S602: In the second optical line terminal, PRBS2 is loaded into the second optical signal through three phase modulators.

[0118] (1) First, a second laser diode generates an optical signal of a second wavelength.

[0119] In a possible implementation, the second laser diode may generate an optical signal with a wavelength of 1340 nm.

[0120] (2) Then, in three phase modulators, the optical signal of the second wavelength is modulated based on the multi-order differential phase shift keying technology.

[0121] In a possible implementation, the optical signal of the second wavelength is modulated in the second optical line terminal based on a sixth-order differential phase shift keying technology. Figure 7 As shown, a schematic diagram of modulating the optical signal of the second wavelength based on 6th-order DPSK is introduced.

[0122] Taking PRBS2 as 1101000101 as an example, the process based on 6th-order DPSK modulation can be:

[0123] Step 1: Map the binary data to hexadecimal data by grouping PRBS2 with 5 bits each to obtain 6-order data. Use the following formula (1) to map the binary data to hexadecimal data.

[0124] 6×s1+s2=16×b1+8×b2+4×b3+2×b4+b5 (1)

[0125] In the above formula (1), b1, b2, b3, b4, and b5 represent the digits of each bit of binary data from left to right, and s1 and s2 represent the digits of each bit of hexadecimal data from left to right. In the embodiment of the present application, the binary data 1101000101 is mapped to hexadecimal data to obtain 6-order data 4205.

[0126] Step 2: Perform an inverse differential operation on the obtained 6-order data to obtain the precoded data. That is, starting from the second bit of the precoded data, each bit of the precoded data is the sum of the previous bit of the precoded data and the previous bit of the 6-order data. If the sum is greater than or equal to 6, subtract 6 from the sum to obtain the precoded data.

[0127] In the embodiment of the present application, the process of performing an inverse differential operation on the 6th order data 4205 is: the first bit of the precoded data is set to 0, then the second bit of the precoded data is equal to the first bit of the precoded data plus the first bit of the 6th order data, that is, 0+4=4. The third bit of the precoded data is equal to the second bit of the precoded data plus the second bit of the 6th order data, that is, 4+2=6. Because the sum is equal to 6, the third bit of the precoded data is actually 6-6=0. Each bit of the precoded data can be obtained by the above-mentioned inverse differential operation process, which will not be repeated here. The precoded data obtained after the inverse differential operation of the 6th order data 4205 is 04005.

[0128] Step 3: Map the precoded data to three different modulation data. The mapping process can obtain modulation data 1, modulation data 2 and modulation data 3 according to the following formulas (2), (3) and (4) respectively.

[0129] Modulation data 1 = s div 3 (2)

[0130] In the above formula (2), s represents the precoded data, div represents the comparison with each bit of the precoded data, and in formula (2), it means that each bit in the precoded data is compared with 3. If a certain bit in the precoded data is greater than or equal to 3, the bit data in the modulated data 1 is 1, and if a certain bit in the precoded data is less than 3, the bit data in the modulated data 1 is 0. In the embodiment of the present application, the modulated data 1 is 01001.

[0131] Modulation data 2 = (s mod 3) div 1 (3)

[0132] In the above formula (3), s represents the precoded data, mod represents the remainder operation, that is, taking the remainder after dividing each bit of the precoded data by 3, div represents the comparison with each bit of the precoded data, and in formula (3), it means that each bit in the precoded data is compared with 1, if a bit of data in the precoded data is greater than or equal to 1, then the bit of data in the modulated data 1 is 1, if a bit of data in the precoded data is less than 1, then the bit of data in the modulated data 1 is 0. In the embodiment of the present application, the modulated data 2 is 01001.

[0133] Modulation data 3 = (s mod 3) div 2 (4)

[0134] In the above formula (4), s represents the precoded data, mod represents the remainder operation, that is, taking the remainder after dividing each bit of the precoded data by 3, div represents the comparison with each bit of the precoded data, and in formula (4), it means that each bit in the precoded data is compared with 2. If a bit of data in the precoded data is greater than or equal to 2, the bit data in the modulated data 1 is 1, and if a bit of data in the precoded data is less than 2, the bit data in the modulated data 1 is 0. In the embodiment of the present application, the modulated data 3 is 00001.

[0135] It should be noted that when the pre-coded data is expressed in phase form, the 6 orders correspond to 0°, 60°, 120°, 180°, 240°, 300°, and 360°, respectively. In the embodiment of the present application, the phases of the optical signal corresponding to the pre-coded data 04005 are 0°, 240°, 0°, 0°, and 300°, respectively.

[0136] In another possible implementation, the optical signal of the second wavelength is modulated in the second optical line terminal based on the 8th-order differential phase shift keying technology. Different from the 6th-order differential phase shift keying technology, in step 1, the binary data needs to be mapped to octal data, and the phase form representation corresponding to the optical signal under the 8th-order modulation also changes accordingly.

[0137] In this way, through the multi-order differential phase-shift keying technology, the spectrum efficiency of the signal can be improved, that is, more data information can be transmitted in the same bandwidth, thereby improving the transmission efficiency.

[0138] In an embodiment of the present application, the spectral efficiency of the optical signal based on the 6th-order differential phase shift keying technology is 2.5b / s / Hz; the spectral efficiency of the optical signal based on the 8th-order differential phase shift keying technology is 3b / s / Hz, and based on this spectral efficiency, a transmission rate of 25Gb / s can be provided.

[0139] The phase modulator may also be used to modulate the phase of the second optical signal.

[0140] like Figure 7 As shown, in a possible implementation, the modulation angles of the three phase modulators are 180°, 60° and 60° respectively. The polarizer is used to convert the optical signal into polarized light and change the vibration direction of the optical signal.

[0141] In this way, the second optical line terminal can generate a second optical signal with a constant optical intensity, which is convenient for subsequent differentiation from the optical intensity of the first optical signal.

[0142] (3) Finally, the generated modulation data 1, modulation data 2, and modulation data 3 are generated into electrical signals through an electrical pulse generator, and the electrical signals are loaded into the second optical signal.

[0143] In a possible implementation, in actual use, when the electrical signal actually generated switches from a high level to a low level, or from a low level to a high level, it does not happen instantly, but there is a short switching time. To simulate actual use, the rising and falling edges of the electrical pulse generator are set to 10%.

[0144] In a possible implementation manner, a transmission rate of the second optical signal transmitted in the second optical line terminal is 12.5 Gb / s.

[0145] In this way, loading the electrical signal onto the optical signal can make the electrical signal more efficiently transmitted and improve the reliability of the data contained in the electrical signal during the transmission process.

[0146] S603 . In the first optical line terminal, use an electrical pulse generator to generate an electrical signal using PRBS1, and add the electrical signal to the first optical signal using a first Mach-Zehnder modulator.

[0147] In a possible implementation, in order to simulate the transmission rate of existing transmission signals in a passive optical network system in a real scenario, the transmission rate of the first optical signal transmitted in the first optical line terminal may be 10 Gb / s, 2.5 Gb / s or 1.25 Gb / s.

[0148] In a possible implementation, the optical signal is generated by a first laser diode, and the first laser diode can generate an optical signal with a wavelength of 1490 nm.

[0149] In a possible implementation, the rising edge and the falling edge of the electric pulse generator are set to 5%.

[0150] In a possible implementation, the modulation index of the first Mach-Zehnder modulator is 14 dB, wherein the modulation index of the Mach-Zehnder modulator refers to the extinction ratio of the signal modulated by the Mach-Zehnder modulator.

[0151] S604 . In the wavelength division multiplexer, couple the first optical signal with the second optical signal, and transmit the coupled target optical signal to the first power beam splitter via the visible light attenuator.

[0152] In a possible implementation, the target optical signal may be transmitted to the first power splitter via a 20 km standard single-mode optical fiber.

[0153] S605 , split the target optical signal into two optical signals at the first power beam splitter, transmit one optical signal to the first optical network unit, and transmit the other optical signal to the second optical network unit.

[0154] S606: In the first optical network unit, a photodetector is used to determine a first optical signal based on light intensity and receive the first optical signal. In the second optical network unit, an optical filter is used to determine a second optical signal based on the wavelength of the optical signal and transmit the second optical signal to a third power beam splitter.

[0155] S607. In the second optical network unit, the third power splitter splits the received second optical signal into two optical signals, transmits one optical signal to the second Mach-Zehnder modulator, and transmits the other optical signal to the second power splitter.

[0156] S608, PRBS3 is loaded onto the optical signal transmitted to the second Mach-Zehnder modulator via the third power beam splitter through the second Mach-Zehnder modulator. The optical signal transmitted to the second power beam splitter via the third power beam splitter is divided into three optical signals, and the optical signals are demodulated by three delay interferometers respectively, and then the demodulated optical signals are received by the photodetector.

[0157] In a possible implementation, the modulation index of the second Mach-Zehnder modulator is 14 dB.

[0158] In a possible implementation, the delay interferometer may be a Mach-Zehnder delay interferometer. The transmission delay time between the upper and lower arms of the Mach-Zehnder delay interferometer is 1 bit (80 ps), and phase shifts of 0°, 60°, and 180° are added respectively.

[0159] S609: Transmit the optical signal modulated by the second Mach-Zehnder modulator to the second optical line terminal through the optical fiber, and receive the optical signal by the photodetector.

[0160] In a possible implementation, the optical fiber used to transmit the optical signal may be a 20 km standard single-mode optical fiber.

[0161] It should be noted that if Figure 8 FIG. 1 is a schematic diagram of another passive optical network system provided by an embodiment of the present application. In the passive optical network system, a plurality of second optical line terminals, a plurality of second optical network units and a plurality of first optical network units may be included. The devices included in each of the second optical line terminals, the second optical network units and the first optical network units are the same as those described above. Figure 5 The components in the passive optical network system are the same, and the optical signal transmission process is also the same as above. Figure 6 The process of optical signal transmission is the same and will not be repeated here.

[0162] like Fig. 9 FIG. 1 is a schematic diagram of another passive optical network system provided by an embodiment of the present application. Figure 8The difference is that the output ends of the second optical line terminals are optically connected to the input end of the fine wavelength division multiplexer, and the input end of the coarse wavelength division multiplexer is optically connected to the output end of the first optical network unit and the output end of the fine wavelength division multiplexer respectively.

[0163] In this way, by selecting different types of wavelength division multiplexers, the requirements for different wavelength division multiplexers in different transmission distance scenarios and different technical requirements can be met, so as to provide better services for users.

[0164] Through the description of the above implementation methods, technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0165] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0166] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0167] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0168] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A passive optical network system, It is characterized in that The system comprises a first optical line terminal, a second optical line terminal, a wavelength division multiplexer, a first power beam splitter, a first optical network unit and a second optical network unit, wherein the output end of the first optical line terminal and the output end of the second optical line terminal are respectively connected to the input end optical fiber of the wavelength division multiplexer, the output end of the wavelength division multiplexer is connected to the input end optical fiber of the first power beam splitter, and the output end of the first power beam splitter is respectively connected to the input end optical fiber of the first optical network unit and the input end optical fiber of the second optical network unit; wherein: The first optical line terminal is used to generate a first optical signal of a first wavelength and a first light intensity, and transmit the first optical signal to the wavelength division multiplexer; the second optical line terminal is used to generate a second optical signal of a second wavelength and a second light intensity, and transmit the second optical signal to the wavelength division multiplexer; The wavelength division multiplexer is used to couple the first optical signal and the second optical signal, and transmit the coupled target optical signal to the first power beam splitter; The first power beam splitter is used to transmit the target optical signal to the first optical network unit and the second optical network unit respectively; The first optical network unit is used to determine the first optical signal from the target optical signal based on the light intensity of the optical signal; the second optical network unit is used to determine the second optical signal from the target optical signal based on the wavelength of the optical signal.

2. The system according to claim 1, It is characterized in that The first optical line terminal comprises a first laser diode and a first Mach-Zehnder modulator, the output end of the first laser diode is optically connected to the input end of the first Mach-Zehnder modulator, and the output end of the first Mach-Zehnder modulator is optically connected to the input end of the wavelength division multiplexer, wherein: The first laser diode is used to generate an optical signal of the first wavelength; the first Mach-Zehnder modulator is used to modulate the optical signal of the first wavelength based on the amplitude shift keying technology to obtain a first optical signal of the first wavelength and the first light intensity, and load the data information to be transmitted into the first optical signal; The second optical line terminal comprises a second laser diode and a phase modulator, the output end of the second laser diode is optically connected to the input end of the phase modulator, and the output end of the phase modulator is optically connected to the input end of the wavelength division multiplexer, wherein: The second laser diode is used to generate an optical signal of the second wavelength; the phase modulator is used to modulate the optical signal of the second wavelength based on the orthogonal modulation technology to obtain a second optical signal of the second wavelength and the second light intensity, and load the data information to be transmitted into the second optical signal.

3. The system according to claim 2, It is characterized in that The phase modulator is used to modulate the optical signal of the second wavelength based on the orthogonal modulation technology to obtain the second optical signal of the second wavelength and the second light intensity, including: The phase modulator is used for modulating the optical signal of the second wavelength based on a multi-order differential phase shift keying technology to obtain a second optical signal of the second wavelength and the second light intensity.

4. The system according to claim 1, It is characterized in that The second optical network unit comprises an optical filter, the input end of the optical filter is optically connected to the output end of the first power beam splitter, wherein: The optical filter is used to filter optical signals of other wavelengths except the second wavelength based on the wavelength of the optical signal to obtain the second optical signal; The first optical network unit comprises a photodetector, the input end of the photodetector is optically connected to the output end of the first power beam splitter, wherein: The photodetector is used to filter the second optical signal greater than a preset light intensity threshold based on the light intensity of the optical signal, obtain the first optical signal, and acquire the data information carried in the first optical signal.

5. The system according to claim 4, It is characterized in that The second optical network unit also includes a second power beam splitter, a plurality of delay interferometers and a photodetector, the input end of the second power beam splitter is optically connected to the output end of the optical filter, the output end of the second power beam splitter is optically connected to the input end of the plurality of delay interferometers, and the output end of the plurality of delay interferometers is optically connected to the photodetector, wherein: The second power beam splitter is used to split the second optical signal determined by the optical filter into multiple optical signals, and transmit the multiple optical signals to the multiple delay interferometers respectively; the multiple delay interferometers are used to adjust the phase and delay of the optical signal transmitted through the second power beam splitter to obtain an adjusted optical signal; the photodetector is used to obtain data information carried in the adjusted optical signal.

6. The system according to claim 5, It is characterized in that The second optical network unit also includes a third power beam splitter and a second Mach-Zehnder modulator, the input end of the third power beam splitter is optically connected to the output end of the optical filter, and the output end of the third power beam splitter is optically connected to the input end of the second power beam splitter and the input end of the second Mach-Zehnder modulator, respectively, wherein: The third power splitter is used to split the second optical signal determined by the optical filter into two optical signals, transmit one optical signal to the second Mach-Zehnder modulator, and transmit the other optical signal to the second power splitter; the second Mach-Zehnder modulator is used to load the data information to be transmitted into the optical signal transmitted by the third power splitter, so as to transmit the optical signal from the second optical network unit to the second optical line terminal.

7. The system according to claim 6, It is characterized in that The second optical network unit further includes a first circulator, an input end of the first circulator is respectively connected to an output end of the optical filter and an output end of the second Mach-Zehnder modulator by optical fiber, wherein: The first circulator is used to control a transmission direction of an optical signal from the second optical line terminal to the second optical network unit, or from the second optical network unit to the second optical line terminal.

8. The system according to claim 7, It is characterized in that The second optical line terminal also includes a photodetector, which is used to receive an optical signal transmitted from the second optical network unit to the second optical line terminal, and obtain data information carried in the optical signal.

9. The system according to claim 8, It is characterized in that The second optical line terminal further comprises a second circulator and a dispersion compensating optical fiber, the input end of the second circulator is connected to the input end of the wavelength division multiplexer through the dispersion compensating optical fiber, and the output end of the second circulator is connected to the photodetector optical fiber, wherein: The second circulator is used to control the transmission direction of the optical signal from the second optical line terminal to the second optical network unit, or from the second optical network unit to the second optical line terminal; the dispersion compensating optical fiber is used to compensate for the dispersion generated during the transmission of the optical signal from the second optical line terminal to the second optical network unit, or from the second optical network unit to the second optical line terminal.

10. The system according to claim 1, It is characterized in that The system further comprises a variable optical attenuator, the input end of the variable optical attenuator is optically connected to the output end of the wavelength division multiplexer, and the output end of the variable optical attenuator is optically connected to the input end of the first power beam splitter, wherein: The variable optical attenuator is used to control the light intensity of the target optical signal.

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