JP2002057678A - Optical communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect collision occurrence by inexpensive constitution for enabling miniaturization in a single-wire half duplex communication system. SOLUTION: This optical communication equipment 1 is composed of a transceiver circuit 3 and an optical communication unit 4. For the optical communication unit 4, closely arranged light emitting element 8 and light receiving element 9 are integrated together with a lens 10, and the light receiving element 9 receives a part of the optical signals of the light emitting element 8 and also receives the optical signals received through an optical fiber 2. At the time of outputting transmission signals by the light emitting element 8, the communication control circuit 5 of the transceiver circuit 3 inputs the received optical signal; by the light receiving element 9, compares them with the transmission signals, detects that the signals are received from the outside through the optical fiber 2 in the case that both do not match, and judges the occurrence of a collision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication apparatus in which a single optical fiber is used as a transmission line to perform half-duplex communication with a partner.

[0002]

In a conventional optical multiplex transmission / reception system, a full-duplex communication system is generally employed for bidirectional communication. Examples of such a communication system include a wavelength division multiplex system and a frequency division multiplex system. In these communication systems, as a system for performing communication with a remote place, a sufficient advantage is obtained in that the communication quality is improved by using an optical fiber having a large communication capacity as compared with a case where a conductor cable is provided. However, for example, there is the following inconvenience in terms of realizing communication over a short distance at low cost.

That is, in the wavelength division multiplex system,
Since optical signals of different wavelengths are simultaneously exchanged between the transmitting side and the receiving side, an optical device such as an optical filter for separating or synthesizing light of each wavelength is required, and the cost increases accordingly. The overall configuration becomes larger. In the frequency division multiplexing method,
Instead of using an optical device such as an optical filter, it is a communication system that performs analog modulation. Therefore, a great merit cannot be obtained in that it is inherently difficult to perform high-speed communication.

On the other hand, although the multiplexing method is not used and the above-mentioned disadvantages do not occur, there is a method using a single-wire half-duplex communication method using a communication path using an optical fiber as a single line.
Such a conventional example is disclosed, for example, in JP-A-55-73.
No. 450 or JP-A-61-107828. However, also in these devices, at both ends of the optical fiber as a communication path, it is necessary to split and combine transmission and reception light, and therefore, it is necessary to provide a duplexer, a combiner or a coupler. However, there is a situation that the cost cannot be avoided.

The present invention has been made in view of the above circumstances, and it is desirable to apply the present invention to short-distance communication and the like. Can be easily performed by a half-duplex communication method, and in this case, there is no need to provide an optical filter, a duplexer, a combiner, a coupler, or the like, and therefore, it is possible to achieve low cost and downsizing. An object of the present invention is to provide an optical communication device as described above.

[0006]

According to the first aspect of the present invention, when a transmission signal to the other party is generated, the signal is converted into an optical signal by a light emitting element and transmitted to the other party via an optical fiber. The element and the collision determination means detect the occurrence of a signal collision in the optical fiber as follows. That is, in the half-duplex two-way communication system, since only one node can transmit data to the transmission line, it is necessary to acquire the right to use the transmission line before starting transmission. Although no collision occurs in transmission performed in a state where the right to use a transmission path has been acquired, transmission may occur simultaneously from a plurality of nodes when such a right to use is acquired.

In the present invention, the light receiving element receives and monitors a part of the optical signal of the light emitting element and receives the optical signal transmitted from the other party via the optical fiber. When the right to use the optical fiber, which is the path, is acquired, the reception signal of the light receiving element matches the transmission signal. Therefore, the collision determination means can detect that no collision has occurred since the comparison result between the transmission signal and the reception signal matches.

On the other hand, when the right to use the transmission line is not acquired, transmission may occur from a plurality of nodes to the optical fiber. In this case, the light receiving signal of the light receiving element is changed to the light signal of its own light emitting element. In addition, an optical signal from the other party which is received by the light receiving element via the optical fiber is received. Therefore, the collision determination means determines that a collision has occurred when the comparison result between the transmission signal and the reception signal does not match.

[0009] In this case, the arbitration process is performed according to the process at the time of occurrence of a collision specified by the protocol of the communication system. In this way, since a part of the optical signal transmitted from its own light emitting element is monitored by the light receiving element, it is possible to determine the collision by comparing the transmitted signal with the received signal of the light receiving element, It is possible to easily and inexpensively perform the collision determination and the corresponding processing.

According to a second aspect of the present invention, in the first aspect of the present invention, since the light emitting element and the light receiving element are configured as an integrated module, an optical device for monitoring an optical signal from the light emitting element is provided. The collision determination operation can be performed easily and inexpensively without providing a separate device.

According to the third aspect of the present invention, in each of the above configurations, communication is performed with the other party using the IEEE 1394 communication protocol, and the collision determining means determines whether or not a collision has occurred. If the node is set as a parent node, TX_REQUEST from the other party that is a child node
It is determined that a signal has been received, and if its own node is set as a child node, the data_pre
Since it is configured to determine that the fix signal has been received, arbitration at the time of occurrence of a collision can be performed quickly and properly.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an electrical block configuration of the optical communication device 1, and optical communication is performed with another optical communication device by one optical fiber 2 as an optical transmission line. The optical communication device 1 includes a transceiver circuit 3 and an optical communication unit 4.

The transceiver circuit 3 comprises a communication control circuit 5 having a function as a collision determination means, and a transmission circuit 6 and a reception circuit 7 connected thereto. The communication control circuit 5 performs communication control to be described later, and
It is configured to perform arbitration in the event of a collision between transmissions to the server.

In this case, the communication control circuit 5 has a judgment circuit (not shown) for judging a collision therein. This is because, for example, the transmission signal given to the transmission circuit 6 and the reception circuit 7
This is a circuit provided with a comparison circuit for comparing with a reception signal input through the logic circuit and combining logic circuit elements and the like so that when they do not match, it is determined that a collision has occurred. The transmitting circuit 6 and the receiving circuit 7 are connected to the light emitting element 8 and the light receiving element 9 of the optical communication unit 4, respectively.

The optical communication unit 4 includes a light emitting element 8 and a light receiving element 9
Is formed integrally with the lens 10 using a translucent resin or the like, and the light emitting element 8 and the light receiving element 9 are arranged at close positions. The optical signal output from the light emitting element 8 is output to the optical fiber 2 via the lens 10 and is provided so that a part of the optical signal is incident on the light receiving element 9. Therefore, when transmitting the optical signal by the light emitting element 8, the optical signal transmitted to the optical fiber 2 can be monitored by the light receiving element 9. Also, the light receiving element 9
Receives a light signal incident through the optical fiber 2 in addition to the light signal of the light emitting element 8 and receives the light signal as a light receiving signal.
Output to

FIG. 2 shows an example in which optical communication is performed using two optical communication apparatuses 1 described above. In this example, the optical communication apparatuses 1a and 1b are configured such that the optical fiber 2 is set as a transmission line. I have. Each optical communication device 1a, 1b has a transceiver circuit 3a, 3b, an optical communication unit 4a, 4b.
Is provided. Although two optical communication devices 1a and 1b will be described here as an example, the present invention is applied to a general configuration in which a plurality of optical communication devices 1 are coupled to each other or via an optical fiber 2 while relaying or relaying. Is what you can do.

Next, the operation of the present embodiment will be described with reference to FIGS. In the following description, a description will be given of the occurrence of a collision at the time of communication between the nodes A and B and the detection operation thereof, with the optical communication device 1a as the node A and the optical communication device 1b as the node B. Since the communication system in the present embodiment is a half-duplex transmission system, only one node can transmit using the transmission path, that is, the optical fiber 2. That is, for example, when the node A is transmitting a transmission signal as shown in FIG. 4A as an optical signal to the optical fiber 2, the node B performs a receiving operation. As shown in ()), there is no transmission signal.

As a result, the waveform of the signal received by the light receiving element 9 of the node A matches the waveform of the transmission signal as shown in FIG. Then, during the transmission operation, the communication control circuit 5 of the node A monitors whether or not a collision has occurred by executing a collision detection processing program described later.

On the other hand, in the state where the use of the transmission signal to the optical fiber 2 is not ensured by the node A as described above, when the transmission request is made, the optical signal may be transmitted from the node B at the same time. appear. This is, for example, FIG.
As shown in (a), when node A is outputting a transmission signal (see (a) in the figure), node B starts transmission at the same time (see (b) in the figure). The received signal received by the light receiving element 9 is a logical sum of the two transmitted signals as shown in FIG. Therefore,
By comparing this with the transmission signal of node A, it is possible to detect that a collision has occurred.

The communication control circuit 5 carries out the above collision detection operation according to a collision detection processing program shown in FIG. In this process, when a transmission signal is being output (step S1), the communication control circuit 5 inputs the optical signal received by the light receiving element 9 and sets it as a reception signal (step S2). A comparison is made with the transmission signal (step S3). If the determination results match, no collision has occurred (step S4), and the process returns to step S1. If the determination results do not match, it is determined that a collision has occurred (step S5). Returning to step S1, the above processing is repeatedly executed.

When it is determined that a collision has occurred through the above-described collision detection processing, the communication control circuit 5 determines the occurrence of the collision according to the communication procedure at the time of the collision specified in the protocol of the communication system. The communication is continued by executing the processing.

According to this embodiment, as a half-duplex transmission system using a single optical fiber 2, a light emitting element 8 and a light receiving element 9 are arranged at close positions as an optical communication section 4 and integrated. Since a part of the optical signal transmitted from the light emitting element 8 is directly received by the light receiving element 9, there is no need to separately provide an optical device for separating and synthesizing the optical signal. Thus, the configuration can be made inexpensive and compact as a whole.

Further, according to the present embodiment, the occurrence of a collision is detected by the communication control means 5 from the reception signal and the transmission signal received by the light receiving element 9 of the optical communication section 4 described above. The collision can be detected with an inexpensive circuit configuration.

(Second Embodiment) FIGS. 6 and 7 show a second embodiment of the present invention, wherein the elements constituting the optical communication apparatus 1 are substantially the same as those of the first embodiment. Is IEEE
An apparatus configured to perform communication by a method based on the E1394 protocol is used. In this embodiment, an example in which five nodes A to E configured by five optical communication devices 1 are connected by an optical fiber 2 as shown in FIG. 6 will be described.

In FIG. 6, each of the nodes A to E is provided as having a plurality of ports, and has a node D as a root node and a node B and a node E as nodes.
Are connected by the optical fiber 2, and the nodes A and C are connected to the node B by the optical fiber 2. Here, nodes A, C, and E are child nodes,
Node B is recognized as a parent node with respect to nodes A and C.

The recognition of the parent node and the child node as described above is automatically set by recognizing when the network changes and resetting it, and executing a predetermined procedure defined in this protocol. It is supposed to be. In the case of a node D in which all ports are connected to child nodes, this is set as a root node. The root node is a node that can issue a right to use a transmission path forming a network, and a signal (TX_GRAN) indicating permission of communication in response to a request from a child node.
At the same time as transmitting T), a transmission rejection signal (data_prefix) is transmitted to the other child nodes.

Prior to starting communication, the node that has generated the communication request transmits a transmission request signal (TX_REQUEST) to the root node D as an optical signal on the transmission line (optical fiber 2). Upon receiving the transmission request signal, the root node D transmits a transmission permission signal (TX_GRANT) signal to that node, and transmits a transmission rejection signal (data_prefix) to all other nodes.

Therefore, for example, now, for example, node A and node E
And transmit the transmission request signal (TX_REQUEST) at the same time. In this case, the root node D transmits a communication permission signal to the node E that has received the transmission request signal first, and transmits a transmission rejection signal (data_prefix) to all other nodes.

In the above case, for example, node A and node B
In some cases, a transmission request signal is transmitted from the node A to the node B, and a transmission rejection signal is transmitted from the node B to the node A. Then, node A
5 and the node B, respectively.
Since the received signal as shown in FIG. 3C is input, the collision is determined by the above-described collision detection processing.

In the system using the IEEE 1394 protocol, the meaning of the transmission signal in that case can be recognized from the fact that a collision has occurred. Therefore, the communication control circuit 5 of each of the nodes A and B executes an arbitration processing program as shown in FIG.

That is, in the node B, the communication control circuit 5 first determines whether or not its own node for the communication partner at that time is the parent node. In the case of the node B, the node A is the parent node with respect to the node A. To (YE in step P1
("S" is determined), and it is recognized that the communication request signal has been received from the child node A (step P2), and the process returns to the main routine to execute the subsequent processing.

On the other hand, in the node A, which is a child node, the communication control circuit 5 determines "NO" in step P1, shifts to step P3, and shifts to step P3.
Recognizes that a transmission rejection signal has been transmitted, and then cancels the transmission request signal transmitted to the parent node (step P4), returns to the main program, and executes the subsequent processing.

As a result, arbitration (arbitration processing) of collision occurrence can be performed quickly and accurately at both the parent node and the child node. As a result, the subsequent communication processing is continued according to the specification of the IEEE 1394 protocol, and normal communication processing can be continued.

According to this embodiment, the same effects as those of the first embodiment can be obtained, and the IEEE13
In single-wire half-duplex communication according to the 94 protocol,
When a collision occurs, the arbitration process can be performed quickly and accurately.

(Other Embodiments) The present invention is not limited to the above embodiment, but can be modified or expanded as follows. In the first embodiment, the case of the nodes A and B has been described. However, a transmission path in which a plurality of nodes are provided so as to communicate with each other or a method in which communication is performed with another node while relaying is formed. It can also be applied to

The present invention can be applied not only to the IEEE 1394 protocol but also to a case where another communication protocol for performing single-wire half-duplex communication is used.

[Brief description of the drawings]

FIG. 1 is an overall electric block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a communication mode by two optical communication devices;

FIG. 3 is a flowchart of a collision detection processing program;

FIG. 4 is a diagram showing a transmission waveform of nodes A and B and a reception waveform of node A (part 1).

FIG. 5 is a diagram showing a transmission waveform of nodes A and B and a reception waveform of node A (part 2).

FIG. 6 is a view corresponding to FIG. 2, showing a second embodiment of the present invention;

FIG. 7 is a flowchart of an arbitration processing program;

[Explanation of symbols]

1 is an optical communication device, 2 is an optical fiber (transmission line), 3 is a transceiver circuit, 4 is an optical communication unit, 5 is a communication control circuit (collision determination means), 6 is a transmission circuit, 7 is a reception circuit, and 8 is light emission The element, 9 is a light receiving element, and 10 is a lens.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroki Kawatomi 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (Reference) 5K002 AA05 DA04 DA91 FA01 5K033 AA09 CB01 DA01 DA11 DB05 DB22

Claims (3)

[Claims] 1. An optical communication device in which a single optical fiber is used as a transmission path to perform half-duplex communication with a partner, when a transmission signal is received, the signal is converted into an optical signal and transmitted to the optical fiber. A light-emitting element that outputs, a light-receiving element that receives an optical signal transmitted by the other party through the optical fiber, receives a part of the optical signal output by the light-emitting element, and converts it into a received signal, Collision judgment means for judging that a collision has occurred between the transmission signal and the reception signal when the reception signal does not match with the transmission signal given to the light emitting element and does not match. Optical communication device. 2. The optical communication device according to claim 1, wherein the light emitting element and the light receiving element are configured as an integrated module. 3. The optical communication apparatus according to claim 1, wherein the optical communication apparatus communicates with the other party using an IEEE 1394 protocol, and wherein the collision determining unit determines that the collision has occurred. When it is determined, it is determined that a TX_REQUEST signal has been received from a partner that is a child node when the own node is set as a parent node, and that the parent node is set when the own node is set as a child node. An optical communication device configured to determine that a data_prefix signal has been received from a partner.