Patent Publication Number: US-2023133846-A1

Title: Converter and Transmission System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/CN2021/082267, filed on Mar. 23, 2021, which claims priority to Chinese Patent Application No. 202010614210.5, filed on Jun. 30, 2020. The disclosures of the aforementioned applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This application relates to the field of optical fiber communication, and in particular, to a converter and a transmission system. 
     BACKGROUND 
     As a broadband optical access technology, a passive optical network (PON) is characterized by a structure of point-to-multipoint physical topology. Signal interaction may be performed between a network device and a terminal device by using the PON. However, with diversified development of an application scenario in which the PON is applied, an amount of data exchanged a data quantity of interaction between the network device and the terminal device is increasingly large. 
     In many scenarios, an interface type of a data interface of the terminal device is different from an interface type of a PON interface of the network device. To implement signal interaction between the network device and the terminal device by using the PON, an intermediate device that is configured to implement an interconnection between the data interface on a side of the terminal device and the PON interface needs to be arranged between the network device and the terminal device. 
     In a conventional technology, the terminal device supplies power to the intermediate device, but some terminal devices do not have a power supply capability, such as a virtual reality (VR) helmet. As a result, the terminal device cannot supply power to the intermediate device, and signal interaction cannot be performed between the network device and the terminal device. 
     SUMMARY 
     This application provides a converter and a transmission system to reduce complexity of a network architecture of a PON and improve a success rate of signal interaction between a network device and a terminal device. 
     According to a first aspect, this application provides a converter. The converter includes a conversion unit. The converter is configured to connect to a first cable. The first cable is a photoelectric composite cable. The first cable includes an optical fiber configured to transmit an optical signal with a passive optical network PON protocol format and a first transmission line configured to transmit a first power supply current. The first transmission line is connected to the conversion unit, the conversion unit is further configured to connect to a data interface, and the data interface is configured to transmit an electrical signal with a target protocol format. The conversion unit is configured to obtain the first power supply current by using the first transmission line. The conversion unit is configured to receive the optical signal with the PON protocol format from the optical fiber. The conversion unit is configured to convert the optical signal with the PON protocol format into the electrical signal with the target protocol format. The conversion unit is configured to transmit the electrical signal with the target protocol format to the data interface. The conversion unit is configured to receive the electrical signal with the target protocol format from the data interface. The conversion unit is configured to convert the electrical signal with the target protocol format into the optical signal with the PON protocol format. The conversion unit is configured to transmit the optical signal with the PON protocol format to the optical fiber. 
     It can be learned that the network device can implement, by using the photoelectric composite cable connected between the network device and the converter, interaction that is of the optical signal with the PON protocol format with the converter and that is performed by the network device by using the photoelectric composite cable, and can further implement a purpose that the network device supplies power to the converter. This effectively avoids a case in which the converter cannot normally work because the converter is not powered, and can further reduce a quantity of cables connected between the network device and the conversion unit, thereby reducing complexity of a connection between the network device and the conversion unit. 
     Based on the first aspect, in an optional implementation, the converter further includes a power supply selection unit. The power supply selection unit is separately connected to the conversion unit, the data interface, and a photoelectric composite interface. The photoelectric composite interface is connected to the first cable. The power supply selection unit is configured to obtain the first power supply current from the photoelectric composite interface and is configured to obtain a second power supply current from the data interface. 
     It can be learned that the power supply selection unit can obtain the first power supply current and the second power supply current, and the power supply selection unit can select one power supply current from the first power supply current and the second power supply current to supply power to the conversion unit, thereby effectively ensuring successful power supply to the conversion unit. 
     Based on the first aspect, in an optional implementation, the converter includes the photoelectric composite interface. The photoelectric composite interface is separately connected to the first transmission line and the power supply selection unit, and the photoelectric composite interface is further separately connected to the optical fiber and the conversion unit. 
     Based on the first aspect, in an optional implementation, the converter includes the first cable. 
     Based on the first aspect, in an optional implementation, the converter includes the data interface, and the converter further includes a second transmission line and a data cable. The data interface is connected to the power supply selection unit by using the second transmission line, and the data interface is connected to the conversion unit by using the data cable. The second transmission line is configured to transmit the second power supply current. The data cable is configured to transmit the electrical signal with the target protocol format. 
     Based on the first aspect, in an optional implementation, the converter includes a second cable and the data interface connected to the second cable. The second cable includes a second transmission line and a data cable. The second transmission line is separately connected to the power supply selection unit and the data interface, and the data cable is separately connected to the conversion unit and the data interface. The second transmission line is configured to transmit the second power supply current, and the data cable is configured to transmit the electrical signal with the target protocol format. 
     Based on the first aspect, in an optional implementation, the power supply selection unit is configured to: when the first power supply current and the second power supply current are obtained, transmit the first power supply current to the conversion unit. 
     It can be learned that the power supply selection unit selects the first power supply current to supply power to the conversion unit. Because power supply of a first power source of the network device is stable, supplying power to the conversion unit by using the first power source ensures working stability of the conversion unit, and avoids a case in which a sudden power failure occurs and consequently the conversion unit cannot perform signal protocol conversion and transmission. In addition, supplying power to the conversion unit by using the network device can adapt to more application scenarios. 
     Based on the first aspect, in an optional implementation, the power supply selection unit is configured to transmit, to the conversion unit, a power supply current that is in the first power supply current and the second power supply current and that has a larger value of a preset parameter. 
     Based on the first aspect, in an optional implementation, the preset parameter is a current value, a voltage value, or a power value. 
     It can be learned that, supplying power to the conversion unit by using the power supply current that is in the first power supply current and the second power supply current and that has the larger value of the preset parameter improves efficiency of supplying power to the conversion unit. 
     Based on the first aspect, in an optional implementation, the photoelectric composite interface is a photoelectric composite socket. The photoelectric composite socket is configured to be inserted by a photoelectric composite plug of the first cable. A first end of the photoelectric composite plug includes a first through hole configured to be penetrated by the first cable, and a second end of the photoelectric composite plug includes a connector. A first end of the connector includes a second through hole configured to be penetrated by the optical fiber, and a second end of the connector has an opening. The optical fiber successively passing through the first through hole and the second through hole extends into the connector. When the photoelectric composite plug is inserted into the photoelectric composite socket, a position of the opening is opposite to a position of the conversion unit. The connector is configured to transmit, between the optical fiber and the conversion unit, the optical signal with the PON protocol format. 
     It can be learned that, the photoelectric composite plug is inserted into the photoelectric composite socket, so that the optical signal with the PON protocol format is transmitted between the conversion unit and the photoelectric composite cable. In addition, using a non-transparent connector can effectively avoid light leakage, thereby improving transmission efficiency of the optical signal with the PON protocol format. 
     Based on the first aspect, in an optional implementation, the first transmission line includes a first positive electrode transmission line and a first negative electrode transmission line. The photoelectric composite plug includes a first electric conductor and a second electric conductor. The first electric conductor is connected to a positive electrode of the first power source by using the first positive electrode transmission line, and the second electric conductor is connected to a negative electrode of the first power source by using the first negative electrode transmission line. The photoelectric composite socket includes a third electric conductor and a fourth electric conductor. When the photoelectric composite plug is inserted into the photoelectric composite socket, the first electric conductor and the third electric conductor are attached to each other in a connection relationship, the second electric conductor and the fourth electric conductor are attached to each other in a connection relationship, and the third electric conductor and the fourth electric conductor are separately connected to the power supply selection unit. 
     It can be learned that, the photoelectric composite plug is inserted into the photoelectric composite socket, so that a connection relationship between the first power source and the conversion unit can be directly implemented, thereby improving efficiency of supplying power to the converter by using the first power source. In addition, a stable structure between the photoelectric composite plug and the photoelectric composite socket effectively avoids detachment between the photoelectric composite plug and the photoelectric composite socket, thereby effectively improving stability of a connection relationship between the first power source and the converter. 
     Based on the first aspect, in an optional implementation, the data interface is a universal serial bus (universal serial bus, USB) interface. The conversion unit is configured to: convert the optical signal with the PON protocol format from the optical fiber into an electrical signal with an Ethernet protocol format, convert the electrical signal with the Ethernet protocol format into an electrical signal with a USB protocol format, and transmit the electrical signal with the USB protocol format to the data interface. The conversion unit is further configured to: convert the electrical signal with the USB protocol format from the data interface into the electrical signal with the Ethernet protocol format, convert the electrical signal with the Ethernet protocol format into the optical signal with the PON protocol format, and transmit the optical signal with the PON protocol format to the optical fiber. 
     It can be learned that, when no other component and/or network needs to be arranged between the network device and the terminal device, interaction between the optical signal with the PON protocol format transmitted by the network device and the electrical signal with the USB protocol format transmitted by the terminal device may be implemented. This effectively reduces complexity of the transmission system, can be efficiently applied to a plurality of PON-based scenarios, improves efficiency of signal interaction between the network device and the terminal device, and reduces network architecture costs for signal interaction between the network device and the intermediate device. 
     Based on the first aspect, in an optional implementation, the converter includes an optical fiber connector. The first cable is connected between the optical fiber connector and the photoelectric composite interface. The optical fiber connector is configured to transmit the optical signal with the PON protocol format. 
     Based on the first aspect, in an optional implementation, the first cable is configured to connect to the optical fiber connector, and the optical fiber connector is configured to transmit the optical signal with the PON protocol format. 
     Based on the first aspect, in an optional implementation, the optical fiber connector is a photoelectric composite connector, and the photoelectric composite connector is further configured to transmit the first power supply current. 
     Based on the first aspect, in an optional implementation, the first cable is connected to both the optical fiber connector and a power supply plug. The first transmission line is connected between the power supply plug and the power supply selection unit. The power supply plug is connected to the first power source, and the power supply plug is configured to transmit, to the power supply selection unit, the first power supply current from the first power source by using the first transmission line. 
     Based on the first aspect, in an optional implementation, a type of the optical fiber connector is any one of the following: a ferrule connector (FC) optical fiber connector, a subscriber connector (SC) optical fiber connector, a lucent connector (LC) optical fiber connector, a straight tip (ST) optical fiber connector, or a fiber distributed data interface (FDDI) optical fiber connector. 
     Based on the first aspect, in an optional implementation, the data interface is any one of the following: a USB interface, a USB Type-C interface (USB Type-C), a USB-to-serial adapter, a micro power Internet of Things USB adapter, a wireless network (Wi-Fi) adapter, a high-definition multimedia interface (HDMI), or an Ethernet link aggregation (Eth-Trunk) interface. 
     Based on the first aspect, in an optional implementation, the data interface is a USB interface, and the converter further includes a connection module. A first end of the connection module is connected to the USB interface, and a second end of the connection module is disposed as any one of the following: a USB Type-C interface, a USB-to-serial adapter, a micro power Internet of Things USB adapter, a Wi-Fi adapter, an HDMI interface, or an Eth-Trunk interface. 
     According to a second aspect, this application provides a transmission system. The transmission system includes a network device and a terminal device. The network device and the terminal device are connected by using a converter. The converter is shown in the first aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an example diagram of a network architecture of a passive optical network according to the conventional technology; 
         FIG.  2    is an example diagram of a network architecture of an embodiment of a transmission system according to this application; 
         FIG.  3    is an example diagram of a structure of a first embodiment of a converter according to this application; 
         FIG.  4    is an example diagram of a connection structure of an embodiment of a converter and a first cable according to this application; 
         FIG.  5    is an example diagram of a structure of an embodiment inside a converter according to this application; 
         FIG.  6    is an example diagram of a structure of a second embodiment of a converter according to this application; 
         FIG.  7    is an example diagram of a structure of a third embodiment of a converter according to this application; 
         FIG.  8    is an example diagram of a structure of a fourth embodiment of a converter according to this application; 
         FIG.  9    is an example diagram of a structure of a fifth embodiment of a converter according to this application; 
         FIG.  10    is an example diagram of a structure of an internal connection of an embodiment of a converter according to this application; 
         FIG.  11    is an example diagram of a cross-sectional structure of an embodiment of a photoelectric composite plug according to this application; and 
         FIG.  12    is an example diagram of a cross-sectional structure of an embodiment of a photoelectric composite socket according to this application. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The following clearly and completely describes the technical solutions in embodiments of this application with reference to the accompanying drawings in embodiments of this application. It is clear that the described embodiments are merely some rather than all of embodiments of this application. All other embodiments obtained by persons skilled in the art based on embodiments of this application without creative efforts shall fall within the protection scope of this application. 
     To better understand this application, a network architecture of an existing PON is first described below with reference to  FIG.  1   .  FIG.  1    is an example diagram of a network architecture of a passive optical network according to the conventional technology. 
     It can be learned from  FIG.  1    that, the PON  100  includes an optical line terminal (OLT)  101 , an optical distribution network (ODN)  102 , and a plurality of optical network units (ONUs)  103 . The OLT  101  is connected to the plurality of ONUs  103  in a point-to-multipoint manner by using the ODN  102 . The PON  100  may use a network type of a gigabit passive optical network (GPON), and the PON  100  may alternatively use a subsequent network type with a higher rate, such as a 25G passive optical network (25G PON), a 50G passive optical network (50G PON), or a 100G passive optical network (100G PON). 
     The ODN  102  may be a communication network that does not require any active device to implement signal interaction between the OLT  101  and the ONU  103 . The OLT  101  may serve as a medium between the ONU  103  and an upper-layer network, forward data obtained from the upper-layer network as downlink data to the ONU  103 , and forward uplink data obtained from the ONU  103  to the upper-layer network. For example, the upper-layer network may be an optical transport network (OTN). 
     The ONU  103  is configured to communicate with the terminal device located on a user side. A specific device type of the terminal device is not limited in this embodiment. For example, the terminal device may be a smartphone  110 , a VR helmet  11 , or an industrial camera  112  shown in  FIG.  1   . Description of the device type of the terminal device is an optional example, and is not limited. The terminal device may be alternatively a smart tablet, VR glasses, an industrial personal computer (IPC), a computer, a television, or the like. 
     It can be learned that in a network architecture of the PON shown in  FIG.  1   , the ODN  102 , the ONU  103 , and the like need to be disposed between the OLT and the terminal device to implement signal interaction. This increases complexity of the network architecture of the PON. A network architecture of the transmission system provided in this application is described below with reference to  FIG.  2   . 
     The transmission system shown in this embodiment includes the network device  201  and the terminal device. The terminal device is configured to perform signal interaction with the network device  201 . For specific descriptions of the terminal devices  110 ,  111 , and  112  shown in this embodiment, refer to  FIG.  1    for details. Details are not described again. This embodiment imposes no limitation on a specific device type of the network device  201 , provided that the network device  201  can perform signal interaction with the terminal device by using a converter  220 . For example, the network device  201  may be the OLT  101  shown in  FIG.  1   . 
     It can be learned from comparison between  FIG.  1    and  FIG.  2    that the network device  201  shown in the transmission system provided in this application can implement signal interaction with the terminal device only by using the converter  220 , and the ODN, the ONU, or the like does not need to be disposed. This reduces complexity of the network architecture of the transmission system, and improves reliability and efficiency of data transmission performed by the transmission system. Several structures of the converter provided in this application are described below. 
     Structure 1 
     The following description is provided with reference to  FIG.  3   .  FIG.  3    is an example diagram of a structure of a first embodiment of a converter according to this application. It can be learned from  FIG.  3    that the converter  300  shown in this embodiment includes a converter housing  301 , and the converter housing  301  includes a data interface  302  and a photoelectric composite interface  303 . As shown in this structure, an example in which both the data interface  302  and the photoelectric composite interface  303  protrude from the converter housing  301  is used for description. In another example, both the data interface  302  and the photoelectric composite interface  303  may be alternatively disposed in the converter housing  301 . This is not specifically limited in this embodiment. The data interface  302  is connected to the terminal device, and the photoelectric composite interface  303  is connected to the network device. 
     A specific interface type of the data interface  302  is not limited in this embodiment. For example, the interface type of the data interface  302  may be any one of the following: a USB interface, a USB Type-C interface, a USB-to-serial adapter, a micro power Internet of Things USB adapter, a Wi-Fi adapter, an HDMI interface, an Eth-Trunk interface, or the like. In this embodiment, an example in which an interface type of the data interface  302  is a USB interface is used, and the data interface  302  is a USB male connector interface. To implement a connection between the converter and the terminal device, the terminal device may include a USB female connector interface that matches the USB male connector interface. When the USB male connector interface is inserted into the USB female connector interface, a connection between the converter and the terminal device is implemented, and then interaction of the electrical signal with the USB protocol format may be performed between the terminal device and the converter. In another example, the data interface  302  may be alternatively a USB female connector interface, and the terminal device includes a USB male connector interface that matches the USB female connector interface, to implement a connection between the converter and the terminal device. 
     This embodiment imposes no limitation on a specific structure of the photoelectric composite interface  303 , provided that the photoelectric composite interface  303  is configured to connect to the first cable. For a specific connection structure, refer to  FIG.  4   .  FIG.  4    is an example diagram of a connection structure of an embodiment of a converter and a first cable according to this application. 
     The photoelectric composite interface  303  shown in this structure is configured to connect to a first cable  400 . Because the converter shown in this structure does not include the first cable  400 , the first cable  400  and the photoelectric composite interface  303  shown in  FIG.  4    are separated. In a scenario in which signal interaction between the network device and the terminal device needs to be implemented by using the converter, the first cable  400  may be inserted into the photoelectric composite interface  303 , to implement a connection between the network device and the converter  300 . 
     To implement the connection between the network device and the converter  300 , the network device includes an adaptation optical fiber connector. The adaptation optical fiber connector is a PON interface. Two ends of the first cable  400  respectively include an optical fiber connector  402  and a photoelectric composite plug  403 . When the optical fiber connector  402  is inserted into the adaptation optical fiber connector, a connection between the network device and the first cable  400  can be implemented. When the photoelectric composite plug  403  is inserted into the photoelectric composite interface  303 , a connection between the first cable  400  and the converter  300  can be implemented. 
     An internal structure of the converter is described below with reference to  FIG.  5   .  FIG.  5    is an example diagram of a structure of an embodiment inside a converter according to this application. It can be learned from  FIG.  5    that, the converter internally includes a power supply selection unit  311  and a conversion unit  310  that are interconnected. The power supply selection unit  311  is configured to supply power to the conversion unit  310 . When being powered by the power supply selection unit  311 , the conversion unit  310  may convert the optical signal with the PON protocol format from a network device into the electrical signal with the USB protocol format. The conversion unit  310  can further convert the electrical signal with a USB protocol format from the terminal device into the optical signal with the PON protocol format. 
     It should be noted that, in this embodiment, an example in which the converter internally includes a power supply selection unit is used for description. In another example, a power supply selection unit may not be disposed in the converter, and a first transmission line that is included in the first cable and that is configured to transmit a first power supply current may be directly connected to the conversion unit, so that the first transmission line can directly transmit the first power supply current to the conversion unit. 
     This embodiment imposes no limitation on specific device forms of the power supply selection unit  311  and the conversion unit  310 . The conversion unit  310  is used as an example. The conversion unit  310  may be one or more chips, or one or more integrated circuits. For example, the conversion unit  310  may be one or more field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), systems on chip (SoC), central processing units (CPUs), network processors (NPs), micro controller units (MCUs), programmable logic devices (PLDs) or other integrated chips, or any combination of the foregoing chips or processors. For description of the device form of the power supply selection unit  311 , refer to the description of the conversion unit  310 . Details are not described again. 
     To implement a function of the conversion unit  310 , power needs to be supplied to the conversion unit  310 . It can be learned that the conversion unit  310  shown in this embodiment is an active device. In this embodiment, power may be supplied to the conversion unit  310  by using the first power supply current from the network device and the second power supply current from the terminal device. It should be noted that, in this embodiment, an example in which a first power source that is configured to send a first power supply current to the conversion unit  310  is located in the network device is used for description. In another example, the first power source may be alternatively located outside the network device. In this embodiment, an example in which a second power source that is configured to send a second power supply current to the conversion unit  310  is located in the terminal device is further used for description. In another example, the second power source may be alternatively located outside the terminal device. 
     A process of transmitting the first power supply current to the power supply selection unit  311  is described below. 
     The first cable  400  shown in this embodiment is a photoelectric composite cable (PCC). The photoelectric composite cable is a cable that integrates an optical fiber and a first transmission line. The optical fiber included in the photoelectric composite cable is configured to transmit the optical signal with the PON protocol format. The first transmission line is configured to transmit the first power supply current, and the first power supply current is configured to supply power to the conversion unit  310 . 
     Specifically, a first power source is disposed in the network device shown in this embodiment, and the first transmission line included in the first cable  400  specifically includes a first positive electrode transmission line and a first negative electrode transmission line. The first positive electrode transmission line is connected to a positive electrode of the first power source, and the first negative electrode transmission line is connected to a negative electrode of the first power source. 
     The power supply selection unit  311  shown in this embodiment includes a first positive electrode (VCC) pin  501  and a first negative electrode (GND) pin  502 . The first VCC pin  501  is connected to the first positive electrode transmission line. Specifically, the first VCC pin  501  and the first positive electrode transmission line may be connected by using a conducting wire inside the converter. It can be learned that the power supply selection unit  311  is connected to the positive electrode of the first power source successively by using the first VCC pin  501  and the first positive electrode transmission line. The first GND pin  502  is connected to the first negative electrode transmission line. Specifically, the first GND pin  502  and the first negative electrode transmission line may be connected by using a conducting wire inside the converter. It can be learned that the power supply selection unit  311  is connected to the negative electrode of the first power source successively by using the first GND pin  502  and the first negative electrode transmission line, to implement that the first power source transmits the first power supply current to the power supply selection unit  311 . 
     A process of transmitting the second power supply current to the power supply selection unit  311  is described below. 
     The power supply selection unit  311  shown in this embodiment further includes a second VCC pin  503  and a second GND pin  504 . In this embodiment, an example in which the data interface  302  is a USB male connector is used, so that a USB female connector that can match the USB male connector is disposed in the terminal device. The USB male connector includes a first contact and a second contact. The first contact is connected to the second VCC pin  503 , and the second contact is connected to the second GND pin  504 . When the USB female connector includes a third contact and a fourth contact, and the USB male connector is inserted into the USB female connector, the third contact is connected to the first contact, and the fourth contact is connected to the second contact. The terminal device includes a third transmission line. The third transmission line is configured to implement a connection between the USB female connector and the second power source. It can be learned that, when the USB male connector is inserted into the USB female connector, the second power supply current of the second power source can be transmitted to the data interface  302  by using the third transmission line, to implement that the second power source transmits the second power supply current to the power supply selection unit  311 . 
     When the power supply selection unit  311  obtains both the first power supply current and the second power supply current, the power supply selection unit  311  may transmit one of the power supply currents to the conversion unit  310 . Specifically, the power supply selection unit  311  further includes a third VCC pin  505  and a third GND pin  506 . Both the third VCC pin  505  and the third GDN pin  506  are connected to the conversion unit  310 , so that when obtaining the first power supply current and the second power supply current, the power supply selection unit  311  can select one of the power supply currents and transmit the selected power supply current to the conversion unit  310  by using the third VCC pin  505  and the third GDN pin  506 , so that the conversion unit  310  implements a corresponding function when being powered. A function of the conversion unit  310  is described below. 
     To implement that the network device transmits the optical signal with the PON protocol format to the terminal device, the network device transmits the optical signal with the PON protocol format to the conversion unit  310  successively by using an adaptation optical fiber connector, an optical fiber connector  402 , and an optical fiber in the first cable  400 . The conversion unit  310  is configured to convert the optical signal with the PON protocol format into the electrical signal with the USB protocol format. 
     The data interface  302  shown in this embodiment is further separately connected to the conversion unit  310  and a data cable located in the terminal device. The data cable may be connected to a processing chip in the terminal device. It can be learned that the conversion unit  310  may transmit the electrical signal with the USB protocol format to the processing chip successively by using the data interface  302  and the data cable in the terminal device, so that the processing chip can process the electrical signal with the USB protocol format. 
     To implement that the terminal device transmits the electrical signal with the USB protocol format to the network device, the processing chip in the terminal device transmits the electrical signal with the USB protocol format to the conversion unit  310  successively by using the data cable in the terminal device and the data interface  302 . The conversion unit  310  may convert the electrical signal with the USB protocol format into the optical signal with the PON protocol format, and the conversion unit  310  transmits the electrical signal with the USB protocol format to the network device successively by using an optical fiber in the first cable  400 , the optical fiber connector  402 , and the adaptation optical fiber connector. 
     Structure 2 
     The following description is provided with reference to  FIG.  6   .  FIG.  6    is an example diagram of a structure of a second embodiment of a converter according to this application. It can be learned from  FIG.  6    that the converter  600  shown in this embodiment includes a converter housing  601 , and the converter housing  601  includes a photoelectric composite interface  603 . For specific descriptions of the converter housing  601  and the photoelectric composite interface  603 , refer to  FIG.  3    for details. Details are not described again in the example. 
     In this example, the converter  600  includes a second cable  604 , and the second cable  604  is connected between a data interface  602  and the converter housing  601 . For a specific description of the data interface  602 , refer to the foregoing structure 1 for details. Details are not described again. 
     Specifically, an internal structure of the converter housing  601  shown in this structure is shown in  FIG.  5   , and details are not described again. The second cable  604  includes a second transmission line and a data cable. The second transmission line is connected to the power supply selection unit  311 . When the data interface  602  is connected to the terminal device, the second power source in the terminal device may transmit the second power supply current to the power supply selection unit  311  by using the second transmission line. 
     The data cable included in the second cable  604  is connected to the conversion unit  310 . The terminal device may transmit the electrical signal with the target protocol format to the conversion unit  310  by using the data cable. For specific descriptions of the power supply selection unit  311  and the conversion unit  310 , refer to  FIG.  5    for details. Details are not described again. 
     Structure 3 
     The following description is provided with reference to  FIG.  7   .  FIG.  7    is an example diagram of a structure of a third embodiment of a converter according to this application. It can be learned from  FIG.  7    that the converter  700  shown in this embodiment includes a converter housing  701  and a data interface  702 . For specific descriptions of the converter housing  701  and the data interface  702 , refer to  FIG.  6    for details. Details are not described again in the example. 
     The converter  700  shown in this structure further includes a first cable  703  and an optical fiber connector  704 . The first cable  703  is connected between the optical fiber connector  704  and a photoelectric composite interface  705 . For specific descriptions of the first cable  703 , the photoelectric composite interface  705 , and the internal structure of the converter, refer to the foregoing structure 1. Details are not described again. In this embodiment, an example in which the converter  700  includes the optical fiber connector  704  is used for description. In another example, the converter  700  may alternatively include the first cable  703 , but does not include the optical fiber connector  704 , provided that the first cable  703  can be connected to the optical fiber connector  704 . The optical fiber connector  704  is described below. 
     The optical fiber connector  704  is a photoelectric composite connector, and the photoelectric composite connector is configured to transmit, to the first cable, the optical signal with the PON protocol format and the first power supply current from the first power source. It can be learned that, the optical fiber connector serving as the photoelectric composite connector has functions of transmitting the optical signal with the PON protocol format and transmitting the first power supply current. 
     A specific structure of the photoelectric composite connector is not limited in this embodiment. For example, the photoelectric composite connector has a ferrule assembly and a conductive terminal. The ferrule assembly is configured to connect a cable in the network device and an optical fiber included in the first cable, so that the ferrule assembly can obtain the optical signal with the PON protocol format by using the cable in the network device, and transmit the optical signal with the PON protocol format to the optical fiber included in the first cable. The ferrule assembly can further obtain, by using the optical fiber included in the first cable, the optical signal with the PON protocol format from the conversion unit, and transmit the optical signal with the PON protocol format to the cable in the network device. 
     The conductive terminal is made of conductor materials such as copper and copper alloys, and aluminum and aluminum alloys. The conductive terminal is connected to the first power source, and the conductive terminal is further connected to the first transmission line included in the first cable. In this way, the conductive terminal may obtain the first power supply current from the first power source, and transmit the first power supply current to the first transmission line of the first cable. 
     Because the optical fiber connector  704  can transmit the optical signal with the PON protocol format, and can further transmit the first power supply current, a quantity of devices of the converter is effectively reduced, and complexity of a structure of the converter is reduced. This helps improve density of the disposed converter in a specific space range. Through a plug-and-unplug connection between the optical fiber connector  704  and the network device, power supply and network access can be simultaneously implemented, thereby improving efficiency of constructing a transmission system. 
     Structure 4 
     The following description is provided with reference to  FIG.  8   .  FIG.  8    is an example diagram of a structure of a fourth embodiment of a converter according to this application. It can be learned from  FIG.  8    that the converter  800  shown in this embodiment further includes a connection module  801 . A first end  802  of the connection module  801  is connected to the data interface  803 . For a specific description of the data interface  803 , refer to the foregoing embodiment for details. Details are not described again. The connection module  801  is inserted into the data interface  803 . For example, if the data interface  803  is a USB female connector interface, the first end  802  of the connection module  801  is a USB male connector interface that matches the USB female connector interface. 
     For specific descriptions of the converter housing  804 , the photoelectric composite interface  805 , the first cable  806 , and the optical fiber connector  807  included in the converter shown in this structure, refer to  FIG.  7    for details. Details are not described again. 
     To enable the converter  800  shown in this embodiment to be applied to a plurality of scenarios, a second end  810  of the connection module  801  shown in this embodiment may include interfaces configured to adapt to different scenarios. For details, refer to the following example. 
     Example 1 
     The second end  810  of the connection module  801  may be a USB Type-C plug. The connection module  801  may connect, by using the second end  810 , to a terminal device that has a USB Type-C socket. It can be learned that the terminal device that has a USB Type-C socket can connect to the converter  800  in a manner of connecting to the second end  810 . The terminal device that has a USB Type-C socket may be various intelligent terminal devices, such as a smartphone and a tablet computer. 
     Example 2 
     The second end  810  of the connection module  801  may be a USB-to-serial adapter, and the USB-to-serial adapter is configured to connect to a terminal device in which a serial interface (SI) is disposed. For example, the terminal device in which the SI is disposed may be various intelligent industrial devices or intelligent traffic terminal devices. 
     Example 3 
     The second end  810  of the connection module  801  may be a micro power Internet of Things USB adapter, and access of a terminal device that supports various micro power Internet of Things protocols is implemented by using the micro power Internet of Things USB adapter. The micro power Internet of Things protocol may be any one of the following: 
     Bluetooth, narrowband Internet of Things (NB-IoT), long range (LoRa), or the like. 
     Example 4 
     The second end  810  of the connection module  801  may be a wireless network (Wi-Fi) adapter. The converter  800  with the Wi-Fi adapter can provide requirements for various terminal devices to access a network by using Wi-Fi. This avoids a dead zone of coverage of the Wi-Fi network, and improves a success rate of accessing the Wi-Fi network by the terminal device. 
     Structure 5 
     The following description is provided with reference to  FIG.  9   .  FIG.  9    is an example diagram of a structure of a fifth embodiment of a converter according to this application. It can be learned from  FIG.  9    that the converter  900  shown in this embodiment includes a converter housing  901 . A data interface  902  and a photoelectric composite interface  903  are disposed in the converter housing  901 . For descriptions of the converter housing  901 , the data interface  902 , and the photoelectric composite interface  903 , refer to the foregoing embodiment for details. Details are not described again. 
     The converter  900  shown in this embodiment further includes an optical fiber connector  904 . A difference between the optical fiber connector shown in this embodiment and the optical fiber connector shown in  FIG.  7    lies in that the optical fiber connector  904  shown in this embodiment does not have a function of transmitting the first power supply current, that is, the optical fiber connector  904  has only a function of transmitting the optical signal with the PON protocol format. For example, a type of the optical fiber connector  904  shown in this embodiment is any one of the following: an FC optical fiber connector, an SC optical fiber connector, an LC optical fiber connector, an ST optical fiber connector, or an FDDI optical fiber connector. 
     To implement power supply to the conversion unit, the converter shown in this embodiment further includes a power supply plug  905 . A first transmission line included in the first cable  906  is connected between the power supply plug  905  and the power supply selection unit. The power supply plug  905  is connected to the first power source, and the power supply plug  905  obtains the first power supply current from the first power source, and transmits the first power supply current to the first transmission line included in the first cable  906 . The first transmission line of the first cable  906  may transmit, to the power supply selection unit, the first power supply current from the first power source, so as to implement power supply for the power supply selection unit by using the first power source. 
     The first cable  906  is separately connected to the optical fiber connector  904  and the power supply plug  905 . Specifically, the optical fiber included in the first cable  906  is connected between the optical fiber connector  904  and the conversion unit. The optical fiber is configured to transmit the optical signal with the PON protocol format between the optical fiber connector  904  and the conversion unit. The first transmission line included in the first cable  906  is separately connected to the power supply plug  905  and the power supply selection unit, to transmit the first power supply current to the power supply selection unit. 
     It can be learned that the converter shown in this structure separately transmits, by using the optical fiber connector  904  and the power supply plug  905 , the optical signal with the PON protocol format to the conversion unit and the first power supply current to the power supply selection unit. This helps separately troubleshoot a power supply fault or a network access fault, improve identification of the power supply fault or the network access fault, and improve efficiency of troubleshooting the transmission system. 
     An internal structure of a converter is described below with reference to  FIG.  10   .  FIG.  10    is an example diagram of an internal connection structure of an embodiment of a converter according to this application. 
     The converter  1000  shown in this embodiment includes a conversion unit  310 , a memory  1020 , and a power supply selection unit  311 . For a manner in which the power supply selection unit  311  is connected to the conversion unit  310 , refer to  FIG.  5   . Details are not described again. The conversion unit  310  is connected to the memory  1020 . The conversion unit  310  specifically includes a first conversion module  1011  and a second conversion module  1012 . The first conversion module  1011  is connected to the second conversion module  1012 , and the first conversion module  1011  is connected to the memory  1020 . The second conversion module  1012  is separately connected to the data interface and the memory  1020 . 
     Specifically, the first conversion module  1011  is disposed opposite to a location of the optical fiber, that is, the first conversion module  1011  is located in a transmission direction of an optical signal with the PON protocol format transmitted by the optical fiber, so that the first conversion module  1011  can obtain the optical signal with the PON protocol format from the optical fiber, and the first conversion module  1011  can further transmit the optical signal with the PON protocol format to the optical fiber. The first conversion module  1011  and the second conversion module  1012  are separately connected to the power supply selection unit  311 , so that the power supply selection unit  311  can supply power to the first conversion module  1011  and the second conversion module  1012 . The memory  1020  is configured to store a computer program. When the first conversion module  1011  and the second conversion module  1012  are powered by the power supply selection unit  311 , the computer program stored in the memory  1020  can be read, to implement a corresponding function. Details are as follows: 
     In a process in which the network device needs to transmit the optical signal with the PON protocol format to the terminal device by using the converter, the network device transmits the optical signal with the PON protocol format to the optical fiber included in the first cable by using the optical fiber connector. The first conversion module  1011  is configured to obtain the optical signal with the PON protocol format from the optical fiber, and is configured to convert the optical signal with the PON protocol format into an electrical signal with an Ethernet protocol format, and transmit the electrical signal to the second conversion module  1012 . The second conversion module  1012  is configured to convert the electrical signal with the Ethernet protocol format into the electrical signal with the USB protocol format, and is configured to transmit the electrical signal to a data interface. Then, the data interface may transmit data with the USB protocol format to the terminal device. 
     In a process in which the terminal device needs to transmit the electrical signal with the USB protocol format to the network device by using the converter, the terminal device transmits the electrical signal with the USB protocol format to the second conversion module  1012  by using the data interface. The second conversion module  1012  is configured to convert the electrical signal with the USB protocol format into the electrical signal with the Ethernet protocol format, and transmit the electrical signal to the first conversion module  1011 . The first conversion module  1011  is configured to convert the electrical signal with the Ethernet protocol format into the optical signal with the PON protocol format, and is configured to transmit the optical signal to the network device by using the optical fiber. 
     A function of the power supply selection unit  311  is described below. Specifically, in this embodiment, different processes in which the power supply selection unit  311  supplies power to the first conversion module  1011  and the second conversion module  1012  based on different obtained power supply currents are specifically as follows: 
     Power Supply Process 1 
     If the power supply selection unit  311  obtains the first power supply current and the second power supply current, the power supply selection unit  311  transmits the first power supply current to the first conversion module  1011  and the second conversion module  1012 , so that the first conversion module  1011  and the second conversion module  1012  are powered by using the first power supply current. 
     Specifically, when the power supply selection unit  311  obtains the first power supply current and the second power supply current, it indicates that both the first power source in the network device and the second power source in the terminal device can supply power to the conversion unit  310 . The power supply selection unit  311  selects the first power source to supply power to the conversion unit  310 . 
     Optionally, with reference to  FIG.  5   , when the power supply selection unit  311  obtains the first power supply current and the second power supply current, the power supply selection unit  311  may disconnect a switch between the second VCC pin  503  and the third VCC pin  505 , and disconnect a switch between the second GND pin  504  and the third GND pin  506 , so that the second power supply current cannot be transmitted to the conversion unit  310 , and then the power supply selection unit  311  transmits only the first power supply current to the conversion unit. 
     Because power supply of the first power source of the network device is stable, supplying power to the conversion unit  310  by using the first power source improves working stability of the conversion unit  310 , and avoids a case in which a sudden power failure occurs and consequently the conversion unit  310  cannot perform data transmission. In addition, supplying power to the conversion unit  310  by using the network device can adapt to more application scenarios. 
     It should be noted that, in this embodiment, an example in which the first power supply current is used to supply power to the conversion unit  310  when the power supply selection unit  311  obtains the first power supply current and the second power supply current is used for description. This is not limited. For example, when the power supply selection unit  311  obtains the first power supply current and the second power supply current, the power supply selection unit  311  may alternatively transmit the second power supply current to the first conversion module  1011  and the second conversion module  1012 , so that the second power source is used to supply power to the first conversion module  1011  and the second conversion module  1012 . 
     Power Supply Process 2 
     When the power supply selection unit  311  obtains the first power supply current and the second power supply current, the power supply selection unit  311  may determine a power supply current that is in the first power supply current and the second power supply current and that has a larger value of a preset parameter. Then, the power supply selection unit  311  may transmit the power supply current having the larger value of the preset parameter to the conversion unit  310 . 
     For example, the preset parameter is a current value. It can be learned that the power supply selection unit  311  determines a larger value in a current value of the first power supply current and a current value of the second power supply current. If the power supply selection unit  311  determines that the current value of the first power supply current is larger than the current value of the second power supply current, the power supply selection unit  311  transmits the first power supply current to the conversion unit  310 . If the power supply selection unit determines that the current value of the first power supply current is smaller than the current value of the second power supply current, the power supply selection unit  311  transmits the second power supply current to the conversion unit  310 . 
     For another example, the preset parameter is a voltage value. It can be learned that the power supply selection unit  311  determines a larger value in a voltage value of the first power supply current and a voltage value of the second power supply current. If the power supply selection unit  311  determines that the voltage value of the first power supply current is larger than the voltage value of the second power supply current, the power supply selection unit  311  transmits the first power supply current to the conversion unit  310 . If the power supply selection unit determines that the voltage value of the first power supply current is smaller than the voltage value of the second power supply current, the power supply selection unit  311  transmits the second power supply current to the conversion unit  310 . 
     For another example, the preset parameter is a power value. It can be learned that the power supply selection unit  311  determines a larger value in a power value of the first power supply current and a power value of the second power supply current. If the power supply selection unit  311  determines that the power value of the first power supply current is larger than the power value of the second power supply current, the power supply selection unit  311  transmits the first power supply current to the conversion unit  310 . If the power supply selection unit determines that the power value of the first power supply current is smaller than the power value of the second power supply current, the power supply selection unit  311  transmits the second power supply current to the conversion unit  310 . 
     Power Supply Process 3 
     If the power supply selection unit  311  obtains only the first power supply current, it indicates that a circuit of the first power source supplying power to the conversion unit  310  is in an on state, but a circuit of the second power source supplying power to the conversion unit  310  is in an off state. The power supply selection unit  311  transmits the first power supply current to the conversion unit  310 , to supply power to the conversion unit  310  by using the first power source. 
     Power Supply Process 4 
     If the power supply selection unit obtains only the second power supply current, it indicates that a circuit of the second power source supplying power to the conversion unit  310  is in an on state, but a circuit of the first power source supplying power to the conversion unit  310  is in an off state. The power supply selection unit  311  transmits the second power supply current to the conversion unit  310 , to supply power to the conversion unit  310  by using the second power source. 
     It can be learned from the foregoing description that the first cable can transmit the first power supply current to the power supply selection unit  311 , and can further perform interaction of the optical signal having the PON protocol format with the conversion unit  310 . A specific implementation process is described below. 
     The following provides a specific description with reference to  FIG.  11    and  FIG.  12   .  FIG.  11    is an example diagram of a cross-sectional structure of an embodiment of a photoelectric composite plug according to this application.  FIG.  12    is an example diagram of a cross-sectional structure of an embodiment of a photoelectric composite socket according to this application. 
     Specifically, a bi-directional optical sub-assembly (BOSA) shown in this embodiment implements a connection between the optical fiber included in the first cable and the conversion unit, and a connection between the first transmission line included in the first cable and the power supply selection unit. The BOSA specifically includes a photoelectric composite plug  1100  and a photoelectric composite socket  1200 . Specifically, an end of the first cable includes the photoelectric composite plug  1100 , and the photoelectric composite interface is the photoelectric composite socket  1200 . When the photoelectric composite plug  1100  is inserted into the photoelectric composite socket  1200 , a connection between the first cable and the converter is implemented. 
     First, a structure of the photoelectric composite plug  1100  is described with reference to  FIG.  11   . 
     It can be learned from the foregoing description that the first cable shown in this application is a photoelectric composite cable, and the photoelectric composite cable includes an optical fiber  1110 , a first positive electrode transmission line  1111 , and a first negative electrode transmission line  1112 . The optical fiber  1110  is configured to transmit the optical signal with the PON protocol format, the first positive electrode transmission line  1111  is configured to connect to a positive electrode of the first power source, and the first negative electrode transmission line  1112  is configured to connect to a negative electrode of the first power source. 
     A first end of the photoelectric composite plug  100  includes a first through hole configured to be penetrated by the first cable. It can be learned that there are three first through holes shown in this embodiment, that is, a first through hole  1121  configured to be penetrated by the optical fiber  1110 , a second through hole  1122  configured to be penetrated by the first positive electrode transmission line  1111 , and a third through hole  1123  configured to be penetrated by the first negative electrode transmission line  1112 . 
     The photoelectric composite plug  1100  includes a first electric conductor  1130  and a second electric conductor  1131 . The first electric conductor  1130  is connected to the first positive electrode transmission line  1111 . It can be learned that the first electric conductor  1130  may be connected to the positive electrode of the first power source by using the first positive electrode transmission line  1111 , and the second electric conductor  1131  is connected to the first negative electrode transmission line  1112 . It can be learned that the second electric conductor  1131  may be connected to the negative electrode of the first power source by using the first negative electrode transmission line  1112 . Specific disposing manners and shapes of the first electric conductor  1130  and the second electric conductor  1131  are not limited in this embodiment. For example, both the first electric conductor  1130  and the second electric conductor  1131  are attached to a cavity wall of an inner cavity of the photoelectric composite plug  1100 , and the first electric conductor  1130  and the second electric conductor  1131  are attached to different locations on the cavity wall, to avoid a short circuit. 
     A second end of the photoelectric composite plug  1100  includes a connector  1140 . A second through hole  1141  is provided penetrating through a cavity bottom of the connector  1140 . The optical fiber  1110  in the photoelectric composite plug  1100  penetrates into the first through hole  1121 , and penetrates out of the second-through hole  1141  to extend into a cavity of the connector  1140 . 
     A second end of the connector  1140  has an opening  1142 . When the photoelectric composite plug  1100  is inserted into the photoelectric composite socket  1200 , a position of the opening  1142  is opposite to a position of the first conversion module, so that an optical signal (an optical signal with the PON protocol format) transmitted by the optical fiber  1110  can be transmitted to the first conversion module through the opening  1142  of the connector  1140 , to perform protocol conversion, or the optical signal sent by the first conversion module can be transmitted to the optical fiber  1110  through the opening  1142  of the connector  1140 . It can be learned that the connector  1140  shown in this embodiment is configured to transmit an optical signal between the optical fiber  1110  and the first conversion module. 
     To improve transmission efficiency of an optical signal and avoid light leakage in the connector  1140 , the connector  1140  shown in this embodiment is made of a non-transparent material. For example, in this embodiment, an example in which the connector  1140  is made of a ceramic material is used for description. 
     Next, a structure of the photoelectric composite socket  1200  is described with reference to  FIG.  12   . 
     The photoelectric composite socket  1200  includes a third electric conductor  1210  and a fourth electric conductor  1211 . When the photoelectric composite plug  1100  is inserted into the photoelectric composite socket  1200 , the first electric conductor  1130  and the third electric conductor  1210  are attached to each other in a connection relationship, the second electric conductor  1131  and the fourth electric conductor  1211  are attached to each other in a connection relationship, and the third electric conductor  1210  and the fourth electric conductor  1211  are separately connected to the power supply selection unit  311  by using conductive media such as conducting wires (for example, a conducting wire  1221  connected to the third electric conductor  1210  and a conducting wire  1222  connected to the fourth electric conductor  1211  that are shown in  FIG.  12   ). It can be learned that the first power supply current of the first power source may be transmitted to the power supply selection unit  311 . 
     Beneficial effects of the converter provided in this application are described below. 
     The converter shown in this embodiment is used. When no other component and/or network needs to be arranged between the network device and the terminal device, interaction between the optical signal with the PON protocol format transmitted by the network device and the electrical signal with the USB protocol format transmitted by the terminal device may be implemented. This effectively reduces complexity of the transmission system, can be efficiently applied to a plurality of PON-based scenarios, improves efficiency of signal interaction between the network device and the terminal device, and reduces network architecture costs for signal interaction between the network device and the intermediate device. 
     In addition, signal interaction between the network device and the terminal device is performed by using the converter, so that long-distance transmission between the network device and the terminal device is effectively implemented, and an amount of data exchanged between the network device and the terminal device can be increased by using the converter. 
     The network device can implement, by using the photoelectric composite cable connected between the network device and the conversion unit, that the network device transmits, by using a photoelectric composite cable, the optical signal with the PON protocol format to the conversion unit, and can further implement that the network device supplies power to the conversion unit. This effectively ensures that the conversion unit normally works, and can further reduce a quantity of cables connected between the network device and the conversion unit, and reduce complexity of a connection between the network device and the conversion unit. 
     The foregoing embodiments are merely intended for describing the technical solutions of this application other than limiting this application. Although this application is described in detail with reference to the foregoing embodiments, persons of ordinary skill in the art should understand that they may still make modifications to the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features thereof, without departing from the scope of the technical solutions of embodiments of this application.