JP2013214887A - Bidirectional optical communication network and bidirectional optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bidirectional optical communication network and a bidirectional optical communication system that can simply achieve, by optical communication, communication performed by an electric signal on the basis of a prescribed protocol.SOLUTION: In a first stage optical coupler 31, two optical output parts 31b, 31b are mutually connected by an optical fiber 41. In one of second stage optical couplers 32, 32, one of its optical output parts 32b, 32b is connected to one of optical input parts 31a, 31a of the optical coupler 31. In the other of the second stage optical couplers 32, 32, one of its optical output parts 32b, 32b is connected to the other of the optical input parts 31a, 31a of the optical coupler 31. This causes an optical signal input to each optical input part of the optical couplers 32, 32 to output from each optical input part of the optical couplers 32, 32 including itself.

Description

  The present invention relates to a bidirectional optical communication network and a bidirectional optical communication system in which a plurality of optical communication devices perform bidirectional communication using optical signals.

  Conventionally, a vehicle is equipped with a large number of electronic devices. Each electronic device is connected via a communication line and cooperates while exchanging information with each other. Control related to comfort is realized. When an electronic device mounted on a vehicle performs communication, CAN (Controller Area Network) is widely adopted as a communication protocol (see Non-Patent Documents 1 and 2).

  In the CAN communication protocol, a plurality of electronic devices are connected to a CAN bus configured by a twisted pair cable that transmits a differential signal, and each electronic device generally transmits and receives a digital signal represented by the differential signal. It is. CAN is a serial communication protocol, and only one electronic device among a plurality of electronic devices connected to the CAN bus can perform transmission processing, and the other electronic devices can perform transmission processing of one electronic device. Need to wait until it finishes. Therefore, when a plurality of electronic devices perform transmission processing simultaneously (that is, when a communication collision occurs), communication arbitration processing (arbitration) is performed in each electronic device, and the priority High communication is performed.

  In order to perform arbitration processing for communication collision, each electronic device outputs a transmission signal to the CAN bus and simultaneously detects the signal level of the CAN bus. Each electronic device determines that a communication collision has occurred when the signal level of the detected signal changes from recessive (inferior value) to dominant (dominant value) with respect to the transmission signal output by itself. To stop. The dominant signal is dominant over the recessive signal on the CAN bus. Therefore, even if a communication collision occurs, the electronic device that outputs the dominant signal can continue the transmission process.

  In recent years, since electronic devices mounted on vehicles tend to increase, it is necessary to connect many electronic devices to one CAN bus and perform communication between many electronic devices. In particular, EVs (Electric Vehicles) or HEVs (Hybrid Electric Vehicles) have more electronic devices than conventional vehicles, and more electronic devices need to communicate with each other. There is.

  However, in order to connect a plurality of electronic devices to the CAN bus, it is necessary to provide a plurality of branch portions in the CAN bus, and signal reflection is repeated due to factors such as impedance mismatch in the branch portions. There is a risk of ringing on the transmission line. Also, in places where many electronic devices and communication lines are concentrated, such as in the engine room of a vehicle, disturbance noise is generated in the CAN bus, particularly in the vicinity of electronic devices and communication lines that handle high-voltage signals. May be superimposed and communication failure may occur.

  Therefore, it is conceivable that an electronic device in the vehicle performs optical communication that is not affected by ringing, disturbance noise, or the like. For example, Patent Document 1 proposes a vehicle network system configured to perform optical communication by connecting a plurality of electronic devices mounted on a vehicle to a star network. The star network is configured to transmit optical signals in one direction from a plurality of optical input units to a plurality of optical output units by combining optical couplers. An electronic device connected to the network is connected to each one of the optical input unit and the optical output unit, transmits an optical signal to the optical input unit, and receives an optical signal from the optical output unit.

  In the arbitration process in the CAN protocol, each electronic device transmits itself, but if the signal transmitted through the communication line matches the signal transmitted by itself, the transmission process is continued. In this case, the transmission process is stopped. For this reason, it is necessary for the electronic device to be able to detect both signals transmitted from the electronic device itself and signals from others. The star network described in Patent Document 1 is configured such that an optical signal input to one optical input unit is output from all optical output units, and is suitable for arbitration processing in the CAN protocol. Has been. Patent Document 2 proposes a bidirectional optical communication network configured by connecting optical couplers in a tree shape. An electronic device connected to the bidirectional optical communication network can be connected to the network with one optical fiber and can transmit and receive optical signals bidirectionally with the optical fiber.

JP 2011-071638 A Japanese Patent Laid-Open No. 2006-262381

ISO 11898-1: 2003 Road vehicles--Controller area network (CAN)-Part1: Data link layer and physical signaling ISO 11519-1: 1994 Road vehicles--Low-speed serial data communication--Part1: General and definitions

  The vehicle network system described in Patent Document 1 needs to combine a large number of optical couplers in order to form a star network that transmits optical signals in one direction from a plurality of optical input units to a plurality of optical output units. It was. For example, in order to construct a star network with 8 inputs and 8 outputs, four 2-input 2-output optical couplers are used to create 8 optical input sections, plus 8 optical output sections. 4 are required. Since four optical couplers are used to connect the eight optical input units to the eight optical output units, a total of twelve optical couplers are required, resulting in an increase in the number of parts and an increase in cost.

  In addition, the bidirectional optical communication network described in Patent Document 2 configures a network that performs bidirectional optical communication by connecting optical couplers in a tree shape. For example, four 2-input 2-output optical couplers are used to connect eight electronic devices. Two optical couplers are used to connect the four optical couplers, and the total number of optical couplers may be six. In addition, two terminators each having a total reflection film are required. There was a problem that the types of parts required to construct a network increased.

  The present invention has been made in view of such circumstances, and an object of the present invention is to enable bidirectional communication that can be simply realized by optical communication based on a predetermined protocol that has been performed using electrical signals. An object is to provide an optical communication network and a bidirectional optical communication system.

  The bidirectional optical communication network according to the present invention is a bidirectional optical communication network in which an optical coupler having two optical input units and two optical output units is connected to a plurality of stages. A first optical coupler connected by a fiber; a second optical coupler having one of its optical output sections connected to one of the optical input sections of the first optical coupler; and an optical input section of the first optical coupler. And a third optical coupler to which one of the optical output sections is connected, and an optical signal is input / output between the optical input sections of the second optical coupler and the third optical coupler. It is characterized by.

  In the present invention, the optical signal input to the optical input unit of the second optical coupler is distributed by the second optical coupler and output from the two optical output units of the second optical coupler. The optical signal output from one of the optical output units of the second optical coupler is input to one of the optical input units of the first optical coupler. The optical signal input to one of the optical input units of the first optical coupler is distributed by the first optical coupler and output from each of the two optical output units of the first optical coupler. Since the two optical output units of the first optical coupler are connected by an optical fiber, the optical signal output from one optical output unit of the first optical coupler is input to the other optical output unit, and the first light The optical signal output from the other optical output unit of the coupler is input to one optical output unit. The optical signals input to the two optical output units of the first optical coupler are respectively distributed by the first optical coupler and output from the two optical input units. At this time, the optical signal input to one optical output unit of the first optical coupler is distributed and the optical signal output from one optical input unit and the optical signal input to the other optical output unit are distributed. And an optical signal output from one of the optical input units. Also, an optical signal input to one optical output unit of the first optical coupler is distributed and output from the other optical input unit, and an optical signal input to the other optical output unit is distributed. The optical signal output from the other optical input unit is combined. Optical signals output from the two optical input units of the first optical coupler are input to one of the optical output units of the second optical coupler and the third optical coupler, respectively, and are distributed by the second optical coupler and the third optical coupler. Are output from the respective optical input sections of the second optical coupler and the third optical coupler. Thus, since the optical signal input to the optical input unit of the second optical coupler is output from all the optical input units of the second optical coupler and the third optical coupler including itself, it is based on a protocol such as CAN. Optical communication is possible, the number of optical couplers is not increased, and a bidirectional optical communication network can be constructed simply with optical couplers.

  The bidirectional optical communication network according to the present invention is characterized in that each of the second optical coupler and the third optical coupler has a non-reflective termination at the other optical output unit.

  In the present invention, each of the second optical coupler and the third optical coupler has the other optical output unit terminated in a non-reflective manner, thereby preventing an extra reflected wave from being generated in the bidirectional optical communication network.

  The bidirectional optical communication network according to the present invention is a bidirectional optical communication network in which an optical coupler having two optical input units and two optical output units is connected to a plurality of stages. Two first optical couplers connected by a fiber, a second optical coupler having one of its optical output sections connected to one of the optical input sections of one of the first optical couplers, and the other first optical coupler. A third optical coupler to which one of the optical output units is connected to one of the optical input units of the optical coupler, and the other optical output unit of each of the second optical coupler and the third optical coupler is connected; An optical signal is input / output between the input portions of the second optical coupler and the third optical coupler.

  In the present invention, the optical signal input to the optical input unit of the second optical coupler is distributed by the second optical coupler and output from the two optical output units of the second optical coupler. The optical signal output from one of the optical output units of the second optical coupler is input to one of the optical input units of one of the first optical couplers. The optical signal input to one of the optical input units of the first optical coupler is distributed by the first optical coupler and output from each of the two optical output units of the first optical coupler. Since the two optical output units of the first optical coupler are connected by an optical fiber, the optical signal output from one optical output unit of the first optical coupler is input to the other optical output unit, and the first light The optical signal output from the other optical output unit of the coupler is input to one optical output unit. The optical signals input to the two optical output units of the first optical coupler are respectively distributed by the first optical coupler and output from the two optical input units. At this time, the optical signal input to one optical output unit of the first optical coupler is distributed and the optical signal output from one optical input unit and the optical signal input to the other optical output unit are distributed. And an optical signal output from one of the optical input units. Also, an optical signal input to one optical output unit of the first optical coupler is distributed and output from the other optical input unit, and an optical signal input to the other optical output unit is distributed. The optical signal output from the other optical input unit is combined. An optical signal output from one of the optical input units of the first optical coupler is input to one of the optical output units of the second optical coupler, distributed by the second optical coupler, and transmitted from each optical input unit of the second optical coupler. Is output. The optical signal output from the other optical output unit of the second optical coupler is input to the other optical output unit of the third optical coupler and distributed by the third optical coupler. Output from the input unit. Thus, since the optical signal input to the optical input unit of the second optical coupler is output from all the optical input units of the second optical coupler and the third optical coupler including itself, it is based on a protocol such as CAN. Bidirectional optical communication is possible, the number of optical couplers is not increased, and a bidirectional optical communication network can be constructed simply with optical couplers.

  The bidirectional optical communication network according to the present invention is characterized in that the other optical input unit of the first optical coupler is terminated without reflection.

  In the present invention, since the first optical coupler has the other optical input section terminated in a non-reflective manner, an extra reflected wave is prevented from being generated in the bidirectional optical communication network.

  A bidirectional optical communication system according to the present invention includes the above-described bidirectional optical communication network and a plurality of optical communication devices connected to the bidirectional optical communication network, and the plurality of optical communication devices have superiority and inferiority. Input / output of an optical signal represented by a binary value is performed.

  In the present invention, a plurality of optical communication devices are connected to a bidirectional optical communication network, and for example, the presence / absence of light in the optical communication network is made to correspond to a dominant (dominant value) / recessive (recessive value) signal value. As a result, each optical communication device can realize optical communication according to the CAN protocol as in the case of communication using differential signals.

  According to the present invention, the bidirectional optical communication network is configured by connecting an optical coupler having two optical input units and two optical output units in a plurality of stages. The first optical coupler is arranged in the first stage, and the second optical coupler and the third optical coupler are arranged in the second stage. In the first optical coupler, two optical output units are connected to each other by an optical fiber. The second optical coupler has one of its optical output units connected to one of the optical input units of the first optical coupler. The third optical coupler has one of its optical output sections connected to the other of the optical input sections of the first optical coupler. Thereby, since the optical signal input to each optical input unit of the second optical coupler and the third optical coupler is output from all the optical input units of the second optical coupler and the third optical coupler including itself, CAN Optical communication based on the above protocol is possible, the number of optical couplers is not increased, and a bidirectional optical communication network can be simply constructed mainly by optical couplers.

It is a schematic diagram which shows the structural example of the bidirectional | two-way optical communication system which concerns on this invention. It is a schematic diagram for demonstrating the structure of a 2 input 2 output optical coupler. It is a block diagram which shows the structural example of the bidirectional | two-way optical communication network by an optical coupler. It is a block diagram which shows the structure of an optical communication apparatus. It is a schematic diagram for demonstrating the process of manufacturing the optical coupler which connected light output parts. It is a schematic diagram for demonstrating the guide of an optical fiber. It is a block diagram which shows the other structural example of the bidirectional | two-way optical communication network by an optical coupler.

(Embodiment 1)
Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. FIG. 1 is a schematic diagram showing a configuration example of a bidirectional optical communication system according to the present invention. The bidirectional optical communication system 1 according to the present embodiment is configured by connecting a plurality of optical communication devices 6 mounted on a vehicle, for example, via an optical fiber 4 and a bidirectional optical communication network 2.

  FIG. 2 is a schematic diagram for explaining the configuration of the optical coupler 3 with two inputs and two outputs. FIG. 3 is a block diagram showing the configuration of the bidirectional optical communication network 2 using optical couplers. A bidirectional optical communication system 1 according to the present embodiment includes a bidirectional optical communication network 2 configured by seven two-input two-output optical couplers, an optical communication device 6 and the like.

  The optical coupler 3 is an optical coupler such as an optical fiber type (also referred to as a waveguide type) or a fusion type, and includes two optical input units 3a and 3a on one side and two optical output units 3b and 3b on the other side. Is provided. The optical signals input to the optical input units 3a and 3a are divided into two and output from the optical output units 3b and 3b. Conversely, the optical signals input to the optical output units 3b and 3b are divided into two and output from the optical input units 3a and 3a. Thus, the optical coupler 3 can input and output optical signals in both directions between the optical input unit and the optical output unit.

  The bidirectional optical communication network 2 shown in FIG. 3 is configured by connecting optical couplers in a plurality of stages using optical fibers. The first stage is an optical coupler 31, the second stage is composed of two optical couplers 32, and the third stage is composed of four optical couplers 33. In FIG. 3, the configuration of each optical coupler in each stage, the optical fiber connected to the optical coupler, and the non-reflective terminator are the same, so for simplicity, one optical coupler is assigned to each stage. Reference numerals are omitted for other optical couplers.

  The first-stage optical coupler 31 connects the optical output units 31 b and 31 b with an optical fiber 41. The optical input units 31a and 31a are connected to optical fibers 42 and 42, respectively. The optical signal input to one optical input unit 31a is distributed and output from the optical output units 31b and 31b. However, the optical signal is circulated by the optical fiber 41 connected to the optical output units 31b and 31b, and the optical output unit 31b. , 31b and distributed again by the optical coupler 31, and output from the optical input units 31a, 31a to the optical fibers 42, 42. Similarly, the optical signal input to the other optical input unit 31a is also output from the optical input units 31a and 31a to the optical fibers 42 and 42.

  In each of the two optical couplers 32 and 32 in the second stage, one optical output unit 32b is connected to one optical input unit 31a of the optical coupler 31 by an optical fiber 42, and the other optical output unit 32b is connected to a non-reflection terminator. Connect to 5. In each of the optical couplers 32 and 32, the optical signal input to each of the optical input units 32a and 32a is output from one optical output unit 32b. The optical signal output from the optical output unit 32 b of one optical coupler 32 is input to the optical input unit 31 a of the optical coupler 31 via the optical fiber 42. Since the optical signal input to the optical input unit 31a of the optical coupler 31 is output from the optical input units 31a and 31a to the optical fibers 42 and 42 as described above, it is output from the optical output unit 32b of one optical coupler 32. The optical signal is distributed to the optical signal input to the optical output unit 32 b and the optical signal input to the optical output unit 32 b of the other optical coupler 32. The optical signals input to the optical output units 32b of the optical couplers 32 and 32 are distributed by the optical couplers 32 and 32, and output from the optical input units 32a and 32a of the optical couplers to the optical fibers 43 and 43, respectively. .

  Each of the four optical couplers 33, 33,. Connect to the non-reflecting terminator 5. Further, the optical couplers 33, 33,... Connect the optical input units 33 a and 33 a to the optical communication device 6 through the optical fiber 44. In each of the optical couplers 33, 33,..., An optical signal input to each of the optical input units 33a and 33a is output from one optical output unit 33b. The optical signal output from the optical output unit 33 b of one optical coupler 33 is input to the optical input unit 32 a of the optical coupler 32 via the optical fiber 43. As described above, the optical signal input to the optical input unit 32a of one optical coupler 32 is output to the optical fibers 43 and 43 from the optical input units 32a and 32a of the optical couplers 32 and 32, respectively. The optical signals input to the optical output units 33b of the optical couplers 33, 33,... Are distributed by the optical couplers 33, 33,. It is output to the fibers 44 and 44.

  FIG. 4 is a block diagram showing a configuration of the optical communication device 6. The optical communication device 6 is a device in which an optical communication function is mounted on an electronic device such as an ECU (Electronic Control Unit) mounted on a vehicle (not shown). The optical communication device 6 includes a CPU (Central Processing Unit) 61, a CAN control unit 62, and an optical communication unit 63. The CPU 61 of the optical communication apparatus 6 executes various programs necessary for operation control and control of each unit in the apparatus by executing a program stored in advance in a ROM (Read Only Memory) or the like. . In addition, when it is necessary to exchange information with another optical communication device 6 during these processes, the CPU 61 gives a communication instruction to the CAN control unit 62 to communicate with the other optical communication device 6. It can be carried out.

  When transmitting data to another optical communication device 6, the CPU 61 gives the data to be transmitted to the CAN control unit 62. When receiving data from another optical communication device 6, the CAN control unit 62 gives the received data to the CPU 61. When receiving data to be transmitted from the CPU 61, the CAN control unit 62 converts the data into data for transmission according to the data format of the CAN protocol, and provides the data to the optical transmission unit 63a of the optical communication unit 63. Data transmitted / received by the CAN protocol is composed of a plurality of fields such as an arbitration field, a control field, a data field, a CRC (Cyclic Redundancy Check) field, and an ACK (ACKnowledgement) field. Stored in the data field. The arbitration field is data for arbitrating communication collisions. A value corresponding to the priority of transmission data is stored, and data “0 (dominant)” has a higher priority than data “1 (recessive)”. high.

  The CAN control unit 62 is provided with data received by the optical receiving unit 63b of the optical communication unit 63. Since the received data is in a CAN protocol data format, the CAN control unit 62 extracts necessary data from the data field of the received data and gives it to the CPU 61. Thereby, the CPU 61 can perform processing according to the received data from the other optical communication device 6.

  The optical communication unit 63 includes an optical transmission unit 63 a and an optical reception unit 63 b, and an electrical signal exchanged with the CAN control unit 62 and an optical signal exchanged with another optical communication device 6 Is used for mutual conversion. The optical transmission unit 63a of the optical communication unit 63 includes a light source such as a light emitting diode and a drive circuit for turning on / off the light source, and transmits transmission data provided as an electrical signal from the CAN control unit 62. It converts into an optical signal and outputs it to the optical fiber 4.

  The light receiving unit 63b of the optical communication unit 63 is configured to include a light receiving element such as a photodiode, and detects light input from the optical fiber 4. The optical receiving unit 63b can output an electrical signal corresponding to the light detected by the light receiving element, thereby receiving the optical signal transmitted by the other optical communication device 6 and converting it into an electrical signal, and performing CAN control. It can be given to part 62.

  Next, transmission of an optical signal by the bidirectional optical communication network 2 will be described. In FIG. 3, the arrows indicate the path and direction through which the optical signal output from one optical communication device 6 is transmitted. In the figure, the optical signal output from the top optical communication device 6 among the optical communication devices 6, 6,... Is input to the optical input unit 33 a of the optical coupler 33 through the optical fiber 44. The optical coupler 33 distributes the optical signal input to the optical input unit 33a and outputs it from the optical output units 33b and 33b. One of the optical signals output from the optical output units 33 b and 33 b is attenuated and terminated by the non-reflecting terminator 5, and the other is input to the optical input unit 32 a of the optical coupler 32 through the optical fiber 43. The optical coupler 32 distributes the optical signal input to the optical input unit 32a and outputs the optical signal from the optical output units 32b and 32b. Of the optical signals output from the optical output units 32 b and 32 b, one is attenuated and terminated by the non-reflection terminator 5, and the other is input to the optical input unit 31 a of the optical coupler 31 through the optical fiber 42.

  The optical coupler 31 distributes the optical signal input to the optical input unit 31a and outputs it from the optical output units 31b and 31b. Since the optical output units 31b and 31b are connected by the optical fiber 41, the optical signal output from one optical output unit 31b is input to the other optical output unit 31b and output from the other optical output unit 31b. The optical signal is input to one optical output unit 31b. The optical coupler 31 distributes the optical signals input to the optical output units 31b and 31b and outputs them from the optical input units 31a and 31a.

  At this time, the optical signal output from one optical input unit 31a and the optical signal input to the other optical output unit 31b among the optical signals obtained by distributing the optical signals input to one optical output unit 31b are distributed. Of the optical signals, the optical signal output from one optical input unit 31 a is combined and output from one optical input unit 31 a to the optical fiber 42. Similarly, the optical signal output from the other optical input unit 31a and the optical signal input to the other optical output unit 31b are distributed among the optical signals obtained by distributing the optical signals input to the one optical output unit 31b. Of the optical signals, the optical signal output from the other optical input unit 31 a is combined and output from the other optical input unit 31 a to the optical fiber 42.

  The optical signals output from the optical input units 31a and 31a of the optical coupler 31 to the optical fiber 42 are transmitted toward the optical communication device 6, are distributed by the optical coupler 32 and the optical coupler 33, and are bidirectional optical communication networks. 2 is input to all the optical communication devices 6 connected to 2. Optical signals output from other optical communication devices 6 other than the top optical communication device 6 can also be input to all the optical communication devices 6 in the same manner. Each optical communication device 6 is connected to the bidirectional optical communication network 2 by a single optical fiber 44, and bidirectional optical communication for inputting and outputting optical signals is performed by the optical fiber 44. As described above, since the optical signal output from one optical communication device 6 is input to all the optical communication devices 6 including itself, the optical communication device 6 outputs the output optical signal and the input optical signal. Can be used to perform mediation processing in the CAN protocol.

  In the bidirectional optical communication network 2, the optical signal output from the optical communication device 6 is distributed and transmitted by the optical couplers 31, 32, and 33, so that the level of the optical signal input to the optical communication device 6 decreases. In the bidirectional optical communication network 2 shown in FIG. 3, since the optical signal output from the optical communication device 6 passes through the optical coupler five times before being input to the optical communication device 6, there is no other transmission loss. The signal level is reduced by 15 dB. When the optical communication device 6 performs communication based on the CAN protocol, a threshold value is set in consideration of a decrease in signal level, and an optical signal input is detected. When the CAN protocol is realized in an optical communication network, for example, the presence / absence of light in an optical communication line may be associated with a dominant (dominant value) / recessive (inferior value) signal value.

  Next, the first-stage optical coupler 31 in the bidirectional optical communication network 2 will be described. As for the connection of the optical output units 31b and 31b of the optical coupler 31 by the optical fiber, for example, the other ends of the optical fibers 4 and 4 whose one ends are connected to the optical output units 31b and 31b may be connected by a connector. Then, the other ends may be fused and connected. FIG. 5 is a schematic diagram for explaining a process of manufacturing the optical coupler 7 in which the optical output units are connected to each other. The optical coupler 7 bends one optical fiber to form a ring portion 7a, and adds the optical fibers extending from both ends of the optical fiber of the ring portion 7a in parallel to form a parallel portion 7b. It is possible to manufacture the optical coupler 7 in which the juxtaposed portions 7b are fused and covered with a case 7c as necessary to connect the light output portions.

  FIG. 6 is a schematic diagram for explaining the guide of the optical fiber 4. In the optical coupler 31, the optical output portions 31b and 31b are connected by an optical fiber, but the optical fiber is looped at a radius of at least the minimum bending radius, and the shape is not stable and is difficult to handle. The guide ring 8 has an arc shape in which a part of the ring is omitted, and a cross section orthogonal to the circumferential direction has a cylindrical half shape in which the outer half of the cylinder is cut off. The radius A of the guide ring 8 is the same as or larger than the minimum bending radius of the optical fiber. The optical fiber 4 is guided by fitting the guide ring 8 from the inside to the optical fiber 4 having a loop shape. If the guide ring 8 is made of resin or the like, the guide ring 8 is flexible. If the optical fiber 4 is fitted after the arcuate outer shape is slightly narrowed, the workability is improved.

  As described above, according to the present embodiment, the bidirectional optical communication network 2 is configured by connecting the optical coupler 3 having two optical input units and two optical output units in a plurality of stages. The optical coupler 31 is arranged on the first stage, and the optical couplers 32 and 32 are arranged on the second stage. Furthermore, the number of optical communication devices 6 that can be connected to the bidirectional optical communication network 2 can be increased by increasing the number of stages such as optical couplers 33, 33,. In the first-stage optical coupler 31, the two optical output units 31 b and 31 b are connected by an optical fiber 41. One of the optical couplers 32 and 32 in the second stage is connected to one of the optical input units 31a and 31a of the optical coupler 31 with one of the optical output units 32b and 32b. The other of the second-stage optical couplers 32 and 32 has one of its optical output units 32b and 32b connected to the other of the optical input units 31a and 31a of the optical coupler 31. As a result, the optical signals input to the optical input units of the optical couplers 32 and 32 are output from the optical input units of the optical couplers 32 and 32 including the optical couplers 32 and 32, so that optical communication based on a protocol such as CAN is possible. Thus, the number of optical couplers does not increase, and a bidirectional optical communication network can be simply constructed mainly by optical couplers. Further, when four optical couplers 33 are arranged as the third stage, similarly, the optical signals input to the respective optical input units of the optical couplers 33, 33,... Are output from each of the optical input units. The same applies when the fourth and fifth stages are provided.

  In addition, according to the present embodiment, one of the optical output sections of the optical couplers 32 and 32 is non-reflective terminated by the non-reflective terminator 5 to prevent an extra reflected wave from being generated in the bidirectional optical communication network 2. .

  Further, according to the present embodiment, a plurality of optical communication devices 6 are connected to the bidirectional optical communication network 2, and for example, the presence / absence of light in the optical communication network is determined as a dominant (dominant value) / recessive (recessive value) signal. By making the values correspond to each other, each optical communication device 6 can realize optical communication according to the CAN protocol as in the case of communication using differential signals.

(Modification)
FIG. 7 is a block diagram showing another configuration example of the bidirectional optical communication network 2 using optical couplers. In the bidirectional optical communication network 2 shown in FIG. 7, two optical couplers 31 are provided in the first stage, two optical couplers 32 are provided in the first stage, and four optical couplers 33 are provided in the third stage.

  In the two first-stage optical couplers 31, 31, the optical output units 31 b, 31 b are connected by an optical fiber 41. One of the two optical couplers 32 and 32 in the second stage connects one optical output unit 32 b to one optical input unit 31 a of one optical coupler 31 through an optical fiber 42. The other of the two optical couplers 32 and 32 in the second stage connects one optical output unit 32 b to one optical input unit 31 a of the other optical coupler 31 through an optical fiber 42. The other optical output portions 32b of the two optical couplers 32 and 32 in the second stage are connected by an optical fiber 42a. The other optical input unit 31 a of each of the two first-stage optical couplers 31 and 31 is connected to the non-reflective terminator 5.

  Each of the four optical couplers 33, 33,. Connect to the non-reflecting terminator 5. Further, the optical couplers 33, 33,... Connect the optical input units 33 a and 33 a to the optical communication device 6 through the optical fiber 44.

  Transmission of an optical signal by the bidirectional optical communication network 2 shown in FIG. 7 will be described. As in FIG. 3, the arrows indicate the path and direction through which the optical signal output from the top optical communication device 6 is transmitted. Since the path leading from the optical communication device 6 to the third and second stages is the same as that in FIG. 3, the description is omitted for the sake of brevity. The optical signal output from the first optical communication device 6 is transmitted to the optical coupler 33 and the optical coupler 32, and is output from the optical output units 32 b and 32 b of the optical coupler 32.

  The optical signal output from one of the optical output units 32 b and 32 b is input to the optical input unit 31 a of the optical coupler 31 through the optical fiber 42. The optical signal input to the optical input unit 31a of the optical coupler 31 is output from the optical input units 31a and 31a through the optical fiber 41 connected to the optical output units 31b and 31b. An optical signal output from one of the optical input units 31 a and 31 a to the optical fiber 42 is input to one optical output unit 32 b of the optical coupler 32. The optical signal input to one optical output unit 32 b of the optical coupler 32 is distributed by the optical coupler 32 and the optical coupler 33 and input to the optical communication device 6. The optical signal output from the other of the optical input units 31 a and 31 a is attenuated by the non-reflecting terminator 5.

  The optical signal output from the other of the optical output units 32b and 32b is input to one optical output unit 32b of another optical coupler 32 in the second stage. The optical signal input to one optical output unit 32 b of the optical coupler 32 is distributed by the optical coupler 32 and the optical coupler 33 and input to the optical communication device 6. Therefore, the optical signal output from the top optical communication device 6 can be input to all the optical communication devices 6 connected to the bidirectional optical communication network 2 including itself.

  Optical signals output from other optical communication devices 6 other than the top optical communication device 6 can also be input to all the optical communication devices 6 in the same manner. Each optical communication device 6 is connected to the bidirectional optical communication network 2 by a single optical fiber 44, and bidirectional optical communication for inputting and outputting optical signals is performed by the optical fiber 44. As described above, since the optical signal output from one optical communication device 6 is input to all the optical communication devices 6 including itself, the optical communication device 6 outputs the output optical signal and the input optical signal. Can be used to perform mediation processing in the CAN protocol. When the CAN protocol is realized in an optical communication network, for example, the presence / absence of light in an optical communication line may be associated with a dominant (dominant value) / recessive (inferior value) signal value.

  As described above, according to the modification, the bidirectional optical communication network 2 is configured by connecting the optical coupler 3 having two optical input units and two optical output units in a plurality of stages. Optical couplers 31 and 31 are arranged in the first stage, and optical couplers 32 and 32 are arranged in the second stage. Each of the first-stage optical couplers 31, 31 has two optical output units 31 b, 31 b connected by an optical fiber 41. One optical coupler 32 of the second stage is connected to one of the optical input sections 31 a and 31 a of one optical coupler 31 and one of the optical output sections 32 b and 32 b. The other optical coupler 32 in the second stage is connected to one of the optical input portions 31a and 31a of the other optical coupler 31 with one of the optical output portions 32b and 32b. The other optical output portions 32b and 32b of the optical couplers 32 and 32 are connected by an optical fiber 42a. As a result, the optical signals input to the optical input units of the optical couplers 32 and 32 are output from the optical input units of the optical couplers 32 and 32 including the optical couplers 32 and 32, so that optical communication based on a protocol such as CAN is possible. Thus, the number of optical couplers does not increase, and a bidirectional optical communication network can be simply constructed mainly by optical couplers. Further, when four optical couplers 33 are arranged as the third stage, similarly, the optical signals input to the respective optical input units of the optical couplers 33, 33,... Are output from each of the optical input units. The same applies when the fourth and fifth stages are provided.

  Further, according to this embodiment, the other optical input unit 31 a of each of the optical couplers 31 and 31 is non-reflective terminated by the non-reflective terminator 5, and an extra reflected wave is generated in the bidirectional optical communication network 2. prevent.

  Further, according to the present embodiment, a plurality of optical communication devices 6 are connected to the bidirectional optical communication network 2, and for example, the presence / absence of light in the optical communication network is determined as a dominant (dominant value) / recessive (recessive value) signal. By making the values correspond to each other, each optical communication device 6 can realize optical communication according to the CAN protocol as in the case of communication using differential signals.

  The disclosed embodiments should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Bidirectional optical communication system 2 Bidirectional optical communication network 3 Optical coupler 31 Optical coupler (1st optical coupler)
32 Optical coupler (second optical coupler)
4 Optical fiber 5 Non-reflective terminator 6 Optical communication device

Claims (5)

In a bidirectional optical communication network in which an optical coupler having two optical input units and two optical output units is connected to a plurality of stages,
A first optical coupler in which two optical output portions are connected by an optical fiber;
A second optical coupler having one of its optical output sections connected to one of the optical input sections of the first optical coupler;
A third optical coupler having one of its optical output portions connected to the other of the optical input portions of the first optical coupler;
A bidirectional optical communication network characterized in that an optical signal is inputted and outputted between each optical input section of the second optical coupler and the third optical coupler. 2. The bidirectional optical communication network according to claim 1, wherein each of the second optical coupler and the third optical coupler has a non-reflective termination at the other optical output unit. In a bidirectional optical communication network in which an optical coupler having two optical input units and two optical output units is connected to a plurality of stages,
Two first optical couplers in which two optical output sections are connected by an optical fiber;
A second optical coupler in which one of the optical output sections is connected to one of the optical input sections of the first optical coupler;
A third optical coupler in which one of the optical output units is connected to one of the optical input units of the other first optical coupler;
The other optical output unit of each of the second optical coupler and the third optical coupler is connected so that an optical signal is input / output between the input units of the second optical coupler and the third optical coupler. Characteristic bidirectional optical communication network.   4. The bidirectional optical communication network according to claim 3, wherein the other optical input unit of the first optical coupler has a non-reflective termination.   5. The bi-directional optical communication network according to claim 1, and a plurality of optical communication devices connected to the bi-directional optical communication network, wherein the plurality of optical communication devices have a dominant value. And a bi-directional optical communication system that performs input / output of an optical signal represented by a binary value of a recessive value.

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