JPH05336134A - Optical local area network - Google Patents

Abstract

PURPOSE:To provide the local area network system having the efficient access control system in which information is branched and inserted on an optical transmission line passively and the transmission band is effectively used without loss of impartiality of an access right with respect to the loop optical local area network. CONSTITUTION:In the system where plural numbers of 1st transmitter-receiver 2-1-n-th transmitter-receiver 2-n each having a packet transmission means and a packet reception means, a monitor controller 3 are connected to one optical transmission line 4, one set of left and right direction photocouplers 5a-5j are provided on connecting points among the optical transmission line 4 and the 1st transmitter-receiver 2-1-n-th transmitter-receiver 2-n and the insertion of a packet onto the optical transmission line 4 and the distribution of the packet from the optical transmission line 4 are implemented in an optical signal level and the 2-way communication is realized.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a looped optical local area network. In a data processing system of a computer including a personal computer, a workstation and a database, it is necessary to transfer a large amount of data between these data processing systems, and it is not allowed to stop the network system when expanding / moving connecting devices. In addition, it is desirable that the transmitter / receiver not in use can be turned off.

Further, as the scale of the network system expands, there is a demand for a local area network system that is highly reliable and economical. Therefore, there is a need for a local area network system that is highly reliable, expandable, and economical, and that has access control adapted to a passive method that drops / inserts information on an optical transmission line as an optical signal.

[0003]

2. Description of the Related Art FIG. 19 is a diagram showing a conventional local area network, in which (A) shows a case of an active configuration and (B) shows a case of a passive configuration.

In FIG. 19, 70 is an optical transmission line for transmitting an optical signal. In addition, 71 is a transmission / reception device (node),
An optical / electrical conversion unit (O / E) 71a and a separation unit 71b are provided, and a multiplexing unit 71c and an electric / optical conversion unit (E / O) 71d are provided. Also, 74 is an optical coupler for making a passive configuration.

In the conventional optical local area network system, there is an active loop or active ring configuration for efficiently accommodating a large amount of data transfer in the optical transmission line 70.

In the case of the active configuration, as shown in FIG. 19 (A), at the time of reception, the multiplexed optical signal on the optical transmission line 70 is converted into an electric signal in the O / E 71a, and the demultiplexing unit is provided.
71b separates into each electric signal and receives.

At the time of transmission, the multiplexing unit 71c multiplexes both electric signals of the information from the own terminal and the received information for other nodes, and after converting into an optical signal by the E / O 71d, it is transmitted on the optical transmission line 70. Send to.

In such an active transmission system, the node 71 makes effective use of the transmission band by dropping / inserting data on the optical transmission line 70 by various access control systems.
The optical transmission line 70
Was returning data to.

However, in this active system, since optical signal → electrical signal → optical signal conversion is performed in all the nodes 71 on the optical transmission line 70 regardless of the presence / absence of information branching / insertion, when the node 71 fails. In addition to the significant spread of the network, the reliability will be significantly reduced and the communication will be interrupted when the network is expanded.

On the other hand, in the case of the passive configuration, FIG. 19 (B)
As shown in, when receiving, the multiplexed optical signal on the receiving optical transmission line 70a is branched into two by the optical coupler 74a, and one optical signal is transmitted as it is to the receiving optical transmission line 70a and the other optical signal is transmitted. The signal is converted into an electric signal by the O / E 71a, and separated into each electric signal by the separating unit 71b and received.

At the time of transmission, information from an own terminal is multiplexed into an electric signal by a multiplexing unit 71c, converted into an optical signal by an E / O 71d, and then inserted by an optical coupler 74b to transmit an optical transmission line. Dispatch on 70b.

However, in this passive system, two optical transmission lines, one dedicated for transmission and the other dedicated for reception, are required. Therefore, it is necessary to develop an efficient access system.

[0013]

Therefore, in the active configuration of the conventional example, there is a problem that when a node fails, the ripple is large and the reliability is remarkably lowered, and a communication interruption occurs when the network is expanded. is there.

The present invention provides a local area network system having an efficient access control system that passively drops / inserts information on an optical transmission line and can effectively use the transmission band without impairing the fairness of access rights. The purpose is to do.

[0015]

In order to achieve the above object, according to the present invention, a plurality of first transmission / reception devices 2 each having a monitor control device 3 and a packet sending means and a receiving means in one optical transmission line 4 are provided. -1 to n-th transmission / reception device 2-n are connected to each other, and a pair of left and right-sided light beams are connected at the connection point between the optical transmission line 4 and the first transmission / reception device 2-1 to n-th transmission / reception device 2-n. The couplers 5a to 5j are provided so that the packet is inserted into the optical transmission line 4 and the packet is distributed from the optical transmission line 4 at the optical signal level, and the communication can be performed in both left and right directions. To do.

The optical coupler 11 for exclusive use of transmission / reception in the left direction of the optical transmission line 4 and the electric / optical conversion unit 12 and the optical coupler 13 for exclusive use of transmission / reception in the right direction, the electric / optical conversion unit 14 and the reception direction determination unit 23 are provided. The first transmitting / receiving device 2-1 to the nth transmitting / receiving device 2-n are provided with the receiving direction determining means and the transmitting direction selecting portion 21. To be possible.

The token packet on the optical transmission line 4 is monitored, and when a token packet is detected, a busy mark signal is sent to the optical transmission line 4 to modify the token packet prior to the token packet analysis processing. The optical couplers 5a to 5j are provided as means for performing token access control at the optical signal level, and the first transceiver device 2-1 to the nth transceiver device 2-n detect a token packet before modification. The token frame format has a delay time for compensating the operation time until the operation.

Further, a means for detecting the free token 111 on the optical transmission line 4 and transmitting it to the left system or the right system according to the moving procedure of the free token 111 to perform a smooth access right relay is the monitoring control device. It is configured to prepare for 3.

Furthermore, a disconnection point 5 of the optical transmission line 4
Of the token packet and the data packet 114 when the failure is detected, the monitoring controller 3 is equipped with a bidirectional relay means.

Then, the disconnection point 5 of the optical transmission line 4 is detected, and when the failure is detected, the retransmitting means of the free token 111 is provided in each of the first transmitting / receiving device 2-1 to the nth transmitting / receiving device 2-n. ..

[0021]

The present invention is, as shown in FIG. 1, a single optical transmission line 4
A plurality of first transmitting / receiving devices 2-1 to n-th transmitting / receiving devices, each of which includes a monitoring control device 3 and a packet sending means and a receiving means
A pair of left and right optical couplers 5a to 5j are provided at the connection points of the 2-n, the optical transmission line 4, and the first transmitting / receiving device 2-1 to n-th transmitting / receiving device 2-n.

Therefore, it is possible to insert the packet on the optical transmission line 4 and distribute the packet from the optical transmission line 4 at the optical signal level and perform bidirectional communication. Further, the optical coupler 11 dedicated to transmission / reception in the left direction of the optical transmission line 4 and the electric / optical conversion section 12, and the optical coupler 13 dedicated to transmission / reception in the right direction, the electric / optical conversion section 14 and the reception direction determination section
Receiving direction determining means and transmitting direction selecting unit consisting of 23
The first transmission / reception apparatus
It is provided inside the 1st to n-th transceivers 2-n.

Therefore, independent transmission / reception control can be performed in the left-right direction by the first transmission / reception device 2-1 to the n-th transmission / reception device 2-n.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to FIGS. 1 to 3, and the method of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing the configuration of the system of the present invention, and describes a local area network system. Note that FIG. 2 is a diagram showing a configuration of a transmission / reception device according to an embodiment of the present invention, and the first transmission / reception device 2-1 will be described as an example. FIG. 3 is a diagram showing the configuration of the supervisory control device according to an embodiment of the present invention.

In the following description, the same circuits will be described using the same symbols, and the duplicated description will be omitted. In FIG. 1, the optical transmission line 4 is formed by, for example, an optical fiber configured in one loop for packet communication in both clockwise and counterclockwise directions.

In the optical transmission line 4, a plurality of first transmitting / receiving devices 2-1 to n-th transmitting / receiving devices 2-n are provided to the right optical couplers 5a, 5c, 5e, 5.
g, 5i are connected to the left-hand side optical couplers 5b, 5d, 5f, 5h, 5j, and the first transmitter / receiver 2-1 to nth transmitter / receiver 2-n are input / output devices such as a personal computer 1a. , 1c, computer 1b, workstation 1d, and bridge 1d connected to another network.

Regarding the transmission direction of light in the transmission / reception devices 2-1 to 2-n and the optical transmission line 4, the rightward optical couplers 5a, 5c, 5e, 5g and 5i can pass only rightward optical signals, while Left-handed optical coupler 5b, 5d, 5
Only optical signals pointing to the left can pass through f, 5h, and 5j.

By using this structure, it is possible to select transmission in one direction or both directions according to the packet to be transmitted, and it is also possible to receive in both directions. In FIG. 2, 5a is a rightward optical coupler and 5b is a leftward optical coupler.
The first transmitter / receiver 2-1 includes an optical interface unit 10, a transmission path selection control unit 20, a transmission / reception processing unit 30, and a transmission / reception buffer.
40 and an external interface unit 50.

In the following, the path of a packet such as data is shown by a thick line (-), and the path of a control signal is shown by a thin line (-). The optical interface unit 10 includes an optical coupler 11, an optical coupler 13, an electric / optical conversion unit (left system) 12 and an electric / optical conversion unit (right system) 14, and the optical coupler 11 and the electric / optical conversion unit are included. (Left system) 12 transmits and receives to the left of the optical transmission line 4. Optical coupler 13 and electrical / optical converter (right)
Similarly, for 14 as well, transmission and reception are performed rightward.

The transmission path selection control unit 20 includes a reception direction determination unit 23.
The receiving direction of the packet is determined by the transmission control unit 22.
In response to the instruction, the transmission direction selection unit 21 switches the packet transmission direction.

The transmission / reception processing unit 30 replaces the transmission line code conversion and the clock in the reception processing unit 35, and the reception packet processing unit
At 36, the packet header is analyzed and CRC (Cyclic Redundancy Check) is checked, and the packet addressed to itself is fetched and passed to the reception buffer 42.

In the case of a token packet, it is passed to the token controller 34. When a token packet arrives, the token control unit 34 immediately sends a busy mark signal from the transmission buffer 41 if there is a transmission request.

Thereafter, the token control unit 34 determines whether the token is a free token or a busy token. If the token is a free token, the transmission packet processing unit 32 transmits the data packet with the header and CRC to the transmission processing unit after the gap time has elapsed.
The token control unit 34 then sends a free token. The transmission processing unit 31 performs channel code conversion and preamble addition.

The transmission line fault monitoring unit 33 detects the disconnection of the packet data, and if the disconnection continues for a period of the round trip delay time of the optical transmission line 4 or more after sending the free token, the optical transmission line 4 is disconnected. Then, the free token is retransmitted in the direction opposite to the last free token transmission direction.

The transmission / reception buffer unit 40 is for matching the physical interface between the external interface unit 50 and the access of the optical transmission line 4 and waiting for transmission / reception data.

The external interface section 50 is a terminal accommodating adapter that can be changed according to the terminal device to be connected. Figure 3
As shown in FIG.
Optical interface 10 with the same configuration as 1 and transmission path selection controller
20 and a reception packet relay unit 60.

In the reception packet relay unit 60, the reception processing unit 35 switches the transmission path code conversion and the clock, and the reception packet processing unit 36 analyzes the packet header and checks the CRC to discard the error packet, In the case of a token packet, it is passed to the token control unit 34.

When a token packet arrives, the token control unit 34 determines whether it is a free token or a busy token, and if the token packet is a free token, it is passed to the transmission processing unit 31. In addition,
Regarding free token transmission, it is transmitted to the left system or the right system according to the token moving procedure of the transmission control unit 22. When sending a free token in the opposite direction, wait until the reception packet in the opposite direction is completed and then send it.

The transmission processing section 31 carries out channel code conversion and preamble addition. In addition, the transmission path failure monitoring unit 33 detects the disconnection of the packet data, and if the disconnection continues for more than the round trip delay time of the optical transmission path 4, it is determined that the optical transmission path 4 is disconnected and the received packet is detected. Is transmitted in the direction opposite to the received direction.

The contents of one embodiment of the present invention will be described in detail below with reference to FIGS. 4A and 4B are diagrams showing a frame format used in the present invention. FIG. 4A shows a token frame structure and FIG. 4B shows a data frame structure.

The token frame shown in FIG. 4A has a preamble (1/0 alternating signal), a frame ID, and an AAD.
(Access adjustment delay), used flag, and CRC (cyclic redundancy check).

The frame ID is, for example, 10011001 for identifying the token frame, and the AAD is for compensating the delay time of the operation from the detection of the token frame by the optical signal transmitter / receiver to the busy flag of the used flag. is there.

The used flag is used to acquire the right to use the optical transmission line, and is a window for making a busy mark. This used flag shifts the position of the busy mark signal due to the difference in the length of the optical fiber from the optical coupler to the transmitter / receiver and the phase difference of the clock between each device. It fits inside. (Example) Used flag ○ ○ ○ ● ● ● ○ ○ ● Indicates a busy mark (light emission), indicating that an optical transmission line is being used.

Extinguishing indicates that the optical transmission line is not used. Further, CRC is a check bit for the frame ID to the used flag when there is no busy mark signal.

The data frame shown in FIG. 4B has a preamble, a frame ID, a DA (destination address), and an SA.
(Source address), LENGTH (bits indicating the length of the frame), INFO (information), and CRC.

The frame ID is, for example, 10011011 for identifying a data frame, and the INFO is information of variable length or fixed length. Hereinafter, the operation of the present invention will be described in detail with reference to FIGS. Unless otherwise specified, the number of transmitting / receiving devices connected to the optical transmission line 4 is four.

First, FIG. 5 to FIG. 8 are diagrams showing a token capturing flow (No. 1) to (No. 4) according to an embodiment of the present invention. In addition, only the right-hand optical couplers 5a, 5c, 5 are shown in FIG.
All symbols of e, 5g and left-handed optical couplers 5b, 5d, 5f, 5h are shown, and some or all symbols are omitted in other drawings. In the following, it is explained that the second transmission / reception apparatus 2-2 has a transmission request.

FIG. 5A: A free token 111, which is a token packet, comes on the optical transmission line 4 from the left side of the system. Figure 5 (B): This free token 111 is a left-handed optical coupler 5d.
At the same time, it is branched to the second transmission / reception device 2-2, passes rightward on the optical transmission line 4, and is sent to the optical coupler 5c.

FIG. 6A: When the second transmitter / receiver 2-2 detects the frame ID of the received free token 111 and determines that it is a token packet, the busy mark 112 is preceded.
Signal is sent to the rightward optical coupler 5c, and the rightward optical coupler 5c sends the free token 111 on the optical transmission line 4 to the busy token 113.
Change to. After this, it is determined whether it is busy or free.

FIG. 6B: When the token packet is analyzed, it is a free token 111. Therefore, the data packet 114 not shown is prepared for transmission. If Busy Token 113
In the case of, the data packet 114 is not transmitted thereafter.

FIG. 7A: After a certain gap time has passed after the free token 111 has passed, the second transmitter / receiver 2-2 sends the data packet 114 to the left optical coupler 5d and the right optical coupler 5c. Send to.

FIG. 7B: The second transmitter / receiver 2-2 completes the transmission of the data packet 114. FIG. 8A: The second transmission / reception device 2-2 uses the data packet 114
After the completion of the transmission of, the free token 111 is transmitted to the rightward optical coupler 5c after waiting for a certain gap time.

FIG. 8B: The free token 111 circulates on the optical transmission line 4 and transfers the access right of the optical transmission line 4 to another transmission / reception device. 9 to 10 are diagrams showing free token relays (No. 1) to (No. 2) in the supervisory control device of one embodiment of the present invention. In the description below, it is assumed that the free token 111 is relayed from left to right.

FIG. 9A: The data packet 114 is received from the left side by the supervisory control device 3, and the free token is received from the right side.
111 is received. (The data packet 114 from the left arrived after being delayed due to the delay of the optical transmission line 4.) FIG. 9B: The free token 111 from the right has finished receiving, and the data packet 114 from the left is still being received. is there.

FIG. 10: After completion of the reception of the data packet 114 from the left side, the free token 111 is sent to the optical transmission line 4 on the left side after waiting a certain gap time. When sending the free token 111 to the receiving direction, the free token 111 waits for a certain gap time after the reception of the free token 111 in FIG. 7B.
Send 111 to the right.

11 to 15 are diagrams showing operations (No. 1) to (No. 5) when the optical transmission line is broken according to the embodiment of the present invention. In the following, it is assumed that the optical transmission line 4 between the third transmission / reception device 2-3 and the fourth transmission / reception device 2-4 has a disconnection point 5 or has been removed for network expansion work.

FIG. 11A: Immediately after being disconnected at the disconnection point 5, the third transmitting / receiving apparatus 2-3 sends the data packet 114 to both sides,
Then, the free token 111 was sent to the right-handed optical coupler 5e. FIG. 11 (B): The data packet 114 and the free token 111 sent to the right system disappear, and the data packet 114 sent to the left system reaches the monitor control device 3.

FIG. 12A: Since the monitoring control device 3 does not detect the packet within the loop delay time of the optical transmission line 4 by the data packet 114 from the right side, the failure of the disconnection point 5 of the optical transmission line 4 is detected. To detect. Then, the supervisory control device 3 switches the operation from the relay control of the free token 111 to the bidirectional relay control.

Finally, since the third transmitter / receiver 2-3 which has sent the free token 111 does not receive the packet from both directions even after the round trip delay time of the optical transmission line 4 has passed, the disconnection point 5 of the optical transmission line 4 Detect failures.

FIG. 12B: The third transmitter / receiver 2-3 retransmits the free token 111 in the opposite direction to the direction in which the free token 111 was last transmitted. Figure 13 (A): Free token 111 orbits in the opposite direction.

FIG. 13B: The supervisory controller 3 relays the free token 111. The data packet 114 is also relayed in the same manner, and the free token 111 is captured by the fourth transmitter / receiver 2-4.

FIG. 14A: Since the fourth transmitting / receiving apparatus 2-4 receives the free token 111 from the right direction, it sends the free token 111 to the left direction. Fig. 14 (B): The fourth transceiver 2-4 is a free token 111
Since the data packet 114 is not received from both directions even after the circulation delay time of the optical transmission line 4 has passed after the transmission, the failure at the disconnection point 5 of the optical transmission line 4 is detected. Next, the fourth transmitter / receiver 2-4 again sends the free token 111 in the opposite direction to the direction in which the free token 111 was sent last.

FIG. 15: The free token 111 is relayed in the monitor control device 3. The data packet 114 is also relayed. 16 to 18 are diagrams showing operations (1) to 3) at the time of failure of the supervisory control device according to one embodiment of the present invention, assuming that the supervisory control device 3 is in a failure state or a power-off state. explain.

FIG. 16A: For example, the fourth transmission / reception device 2-4 sends the free token 111 to the monitor control device 3. Figure 16 (B): Even after the round trip delay time of the optical transmission line 4 has passed,
Since the fourth transmitter / receiver 2-4 does not receive packets from both directions, the fourth transmitter / receiver 2-4 ends with a free token.
Send the free token 111 again in the direction opposite to the direction in which 111 was sent.

FIG. 17A: The free token 111 goes around the optical transmission line 4, and the free token 111 is captured by, for example, the first transmitter / receiver 2-1. Fig. 17 (B): The first transmitting / receiving device 2-1 is the free token 111
Received from the right, free token 11 to the left.
Sends 1.

FIG. 18: Since the first transmitter / receiver 2-1 does not receive packets from both directions even after the round trip delay time of the optical transmission line 4 has passed after sending the free token 111, the disconnection point 5 of the optical transmission line 4 Detect failures. Next, the first transmitting / receiving device 2-1 sends the free token 111 again in the opposite direction to the direction in which the free token 111 was sent last.

[0068]

As is apparent from the above description, according to the present invention, a network can be economically constructed with a single optical fiber. In addition to passively distributing and inserting information, and enabling bidirectional communication in a loop, it has high reliability against disconnection of optical transmission line and failure of supervisory control device, and it is suitable for network expansion work etc. However, it has excellent expandability because no communication interruption occurs.

Moreover, since the data packet can be transmitted in both directions and the token packet can be transmitted in one direction, there is an effect that the transmission band can be effectively used effectively without impairing the fairness of the access right.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a system of the present invention.

FIG. 2 is a diagram showing a configuration of a transmission / reception device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a supervisory control device according to an embodiment of the present invention.

FIG. 4 is a diagram showing a frame format used in the present invention.

FIG. 5 is a diagram showing a token capture flow (No. 1) according to an embodiment of the present invention.

FIG. 6 is a diagram showing a token capture flow (No. 2) according to an embodiment of the present invention.

FIG. 7 is a diagram showing a token capture flow (Part 3) according to an embodiment of the present invention.

FIG. 8 is a diagram showing a token capture flow (Part 4) according to an embodiment of the present invention.

FIG. 9 is a diagram showing a free token relay (No. 1) in the supervisory control device of one embodiment of the present invention.

FIG. 10 is a diagram showing a free token relay (No. 2) in the monitoring controller of one embodiment of the present invention.

FIG. 11 is a diagram showing an operation (No. 1) when the optical transmission line is broken in the embodiment of the present invention.

FIG. 12 is a diagram showing an operation (No. 2) when the optical transmission line is broken according to the embodiment of the present invention.

FIG. 13 is a diagram illustrating an operation (No. 3) when the optical transmission line is broken according to the embodiment of the present invention.

FIG. 14 is a diagram showing an operation (No. 4) when the optical transmission line is broken according to the embodiment of the present invention.

FIG. 15 is a diagram showing an operation (No. 5) when the optical transmission line is broken according to the embodiment of the present invention.

FIG. 16 is a diagram showing an operation (part 1) at the time of a failure in the supervisory control device according to the embodiment of the present invention.

FIG. 17 is a diagram showing an operation (No. 2) at the time of a failure of the supervisory control device according to the embodiment of the present invention.

FIG. 18 is a diagram showing an operation (part 3) at the time of a failure of the supervisory control device according to the embodiment of the present invention.

FIG. 19 is a diagram illustrating a conventional local area network according to an embodiment.

[Explanation of symbols]

 2-1 to 2-n are first transmitter / receiver to nth transmitter / receiver 3 are supervisory controllers 4 are optical transmission lines 5a, 5c, 5e, 5g, 5i are right-hand optical couplers 5b, 5d, 5f, 5h, 5j Is leftward optical coupler 11,13 is optical coupler 12 is electrical / optical converter (left system) 14 is electrical / optical converter (right system) 111 is free token 112 is busy mark 113 is busy token 114 is data packet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 8529-5K H04L 11/20 102 Z

Claims (6)

[Claims] 1. A supervisory control device (3) for one optical transmission line (4)
And a plurality of first transmitting / receiving devices (2-1) to n-th transmitting / receiving devices (2-n) each having a packet transmitting means and a receiving means are connected, and the optical transmission line (4) and the first transmitting / receiving means A pair of left and right optical couplers (5a to 5j) are provided at the connection points of the device (2-1) to the n-th transmission / reception device (2-n), and a packet is transmitted to the optical transmission line (4). Insertion and distribution of packets from the optical transmission line (4) are performed at the optical signal level,
An optical local area network that is characterized by enabling communication in both left and right directions. 2. An optical coupler (11) dedicated to transmission / reception in the left direction of the optical transmission line (4) and an electrical / optical conversion section (12), and an optical coupler (13) dedicated to transmission / reception in the right direction and electrical / optical conversion. The first transmitting / receiving device (2-1) to the nth transmitting / receiving device are provided with a receiving direction determining unit including a unit (14) and a receiving direction determining unit (23) and a transmitting direction selecting unit including a transmitting direction selecting unit (21). The optical local area network according to claim 1, wherein the optical local area network is provided in (2-n) to enable independent transmission / reception control in the left-right direction. 3. A token packet on the optical transmission line (4) is monitored, and when a token packet is detected, a busy mark signal is sent to the optical transmission line (4) prior to token packet analysis processing. The optical couplers (5a to 5j) are provided as means for modifying the token packet, access control of the token is performed at the optical signal level, and the first transceiver device (2-1) to the nth transceiver device (2-n) 3. The optical local area network according to claim 1, further comprising: a token frame format having a delay time for compensating an operation time from detecting the token packet to modifying the token packet. 4. Free token (1) on the optical transmission line (4)
11) is detected and transmitted to the left system or the right system according to the moving procedure of the free token (111), and the monitoring control device (3) is provided with means for performing a smooth access right relay. The optical local area network according to claim 1. 5. The monitoring controller for detecting bidirectional relay means for a token packet and a data packet (114) when detecting a fault at a disconnection point (5) of the optical transmission line (4).
The optical local area network according to claim 1, wherein the optical local area network is provided in (3). 6. A disconnection portion (5) of the optical transmission line (4) is detected, and when a failure is detected, a re-sending means of a free token (111) is provided with the first transmission / reception device (2-1) to n-th transmission / reception device (2-1). The optical local area network according to claim 1, characterized in that the optical local area network is provided for 2-n).