JPH0646039A - Optical fiber medium connector - Google Patents

Abstract

PURPOSE:To improve the resistance to fault, the maintainability, and the usefulness of a network without an influence of equipment of the other networks. CONSTITUTION:A single repeater connection interface(AUI) circuit 14, two pairs of optical fiber medium interface(MDI) circuits 2 and 7, link test functions 6 and 11 which discriminate whether respective optical fiber links are in the workable state or not, a link selecting mechanism 12 which determines the optical fiber link to use in accordance with the link test results, and a signal switching mechanism 13 which selects and connects one of two pairs of optical fiber links are provided. Thus, the optical fiber cable medium constituting the optical fiber inter-repeater link for use of inter-segment connection of a bus type local area network is duplexed, and the switching processing for the occurrence of a medium fault is automatized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-repeater link device for connecting between segments of a bus type local area network, and more particularly to a method for duplicating an optical link forming an optical inter-repeater link.

[0002]

2. Description of the Related Art Conventionally, in a bus type local area network of this type, an optical fiber medium connecting device used for an inter-repeater link device is composed of a single link consisting of a pair of transmitting and receiving optical fiber cables, It is common to have a pair of media connection interfaces (MDI). For example, ISO8802-3 FOIRL
The structure of the inter-repeater link defined by the (optical fiber inter-repeater link) standard is a repeater connected to the first segment and an optical fiber medium connection device (FOMAU) externally or internally connected to the repeater.
And a repeater connected to the second segment and a FOMAU externally or internally connected to the repeater, a link portion formed by a pair of optical fiber cables is defined.

Regarding the failure detecting means, a square wave signal having a constant cycle is output when there is no transmission data, and the level is monitored on the receiving side. If a failure is detected on the link, the FOMAU causes a failure on the repeater. It is specified that the repeater closes the link by issuing the notification.

[0004]

As a main application of an interrepeater link using an optical fiber, a connection between segments existing between different buildings is typical.
In such applications, the optical fiber cables that make up the optical link are installed in the air or underground outside the building,
The installation environment is far worse than the cables inside the building, and from the perspective of network reliability such as the possibility of disconnection due to physical external forces, there is a higher possibility of failure than other parts, and repair / replacement etc. Maintenance is significantly more troublesome than inside the building.

In addition, the bus system network has a configuration in which there is only one type of route between terminals (no loop route is allowed). Fig. 3 shows DTE18 ~ for each segment.
22, repeaters 15, 17, 24, 26, and FOMA
U1, 16, 23, 25 are provided, and since two independent inter-repeater link devices cannot be used simultaneously for such a segment, even if two systems are prepared in advance, switching is possible. It has the disadvantage that it requires manpower.

An object of the present invention is to provide an optical fiber medium connecting device which improves the fault tolerance, maintainability and usefulness of a network without affecting other network equipment.

[0007]

In order to achieve the above object, an optical fiber medium connecting apparatus according to the present invention comprises a medium connecting interface pair, a link test function pair, a link selecting mechanism, and a signal switching mechanism. And an optical fiber medium connecting device for an optical inter-repeater link for connecting segments of a bus type local area network with an optical fiber cable, wherein a pair of medium connecting interfaces are connected to a double-structured optical fiber link. The pair of link test functions is for identifying whether or not the duplex optical fiber link is in an operable state, and the link selection mechanism uses the optical fiber to be used according to the link test result. The link switching is determined, and the signal switching mechanism selects one of the determined optical fiber links of the duplex configuration. It is intended.

[0008]

The optical fiber cable forming the optical fiber interrepeater link for connecting the segments of the bus type local area network is duplicated, and the switching work at the time of failure becomes unnecessary.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 2 is a connection configuration diagram when the present invention is applied to an optical interrepeater link.

In FIG. 1, an optical fiber medium connecting device (hereinafter referred to as FOMAU) 1 of the present invention is an electro-optical converter (hereinafter referred to as A type optical link) connected to a first optical fiber link (hereinafter referred to as A system optical link). A medium connection interface (hereinafter referred to as MDI) 2 including an EO 4) and an optical-electrical converter (hereinafter referred to as OE) 5, a communication control unit 3 that controls transmission / reception data to and from the MDI 2, and communication control A link test function 6 provided in the section 3 for testing the operating state of the A-system optical link, and an MDI composed of EO9 and OE10 connected to a second optical fiber link (hereinafter referred to as B-system optical link).
7, a communication control unit 8 for controlling transmission / reception data to / from the MDI 7, and a link test function 11 provided in the communication control unit 8 for testing the operating state of the B-system optical link.

The link selection mechanism 12 which monitors the link test result and selects which of the A system optical link and the B system optical link is used controls the signal switching circuit 13 to cause the AUI circuit 14 to operate. The communication control unit 3 of the A system or the communication control unit 8 of the B system is connected to realize signal connection to the repeater 15 and the A system optical link or the B system optical link.

As an example of the link test functions 6 and 11, as defined in ISO8802-3, when there is no transmission signal to the optical link (when the transmission signal is not received from the repeater), the idle test is performed. A square wave pulse signal with a constant period called a signal is always sent, and the receiving side measures the received signal level of the pulse signal, and if it does not reach a certain level (detection of optical level drop), it is regarded as a link failure state and the repeater Has a function of outputting a failure state notification called an SQE signal, stopping transmission / reception, and waiting for the link to return to normal. With this function, if the optical reception level is restored and conditions are met, communication can be automatically restored.

If both the A-system optical link and the B-system optical link are normal, the A-system optical link and the B-system optical link are automatically operated by the link test function 6 and the link test function 11 after the power is turned on. Tested and ready to send and receive. In this state, idle signals are transmitted from EO4 and EO9, and idle signals are received by OE5 and OE10.

The link test function 6 notifies the link selection mechanism 12 that the A system optical link can be transmitted and received.
Similarly, the link test function 11 notifies the link selection mechanism 12 that the B-system optical link can be transmitted and received. The link selection mechanism 12 determines an available optical link from the notifications of the link test function 6 and the link test function 11.
If only one optical link is available, the available one is selected. If both optical links are usable as in this case, one is selected by a predetermined method.
However, when there is an incoming call from an optical link different from the selected optical link, the selected optical link is immediately switched to the called side.

If both optical links are in a failure state, the last selected optical link remains selected. If both optical links have failed since the power was turned on, the one selected when both optical links are normal is temporarily selected. When the link selection mechanism 12 selects an optical link, it sends a control signal to the signal switching circuit 13 to connect the communication control unit corresponding to the selected optical link and the signal of the AUI circuit 14 to correspond to the unselected optical link. The signal between the communication control unit and the AUI circuit 14 is logically cut off.

The AUI circuit 14 has a driver / receiver function for converting the signal level, and the signal switching circuit 13 is provided.
The signal to be switched by has a one-to-one correspondence with the signal between the repeater 15 and the AUI circuit 14. ISO8802-3FO
According to the IRL standard, three lines of DO (transmission data), DI (reception data), and CI (control signal: used for failure notification) are used. The switching circuit 13 switches this signal to the AUI for the communication control unit on the selected optical link side.
The repeater 15 is connected via the circuit 14.

Each communication control unit outputs a failure signal (SQE signal) to the CI circuit if the link test results in a failure state.

If a failure occurs in one of the links, for example, the A-system optical link, the link test function 6 notifies the link selection mechanism 12 of the failure, and the communication control unit 3 issues a failure signal, the link selection is performed. Since the mechanism 12 immediately switches the switching circuit 13 to the communication control unit 8, the fault signal is separated from the AUI circuit 14, and the repeater 15 does not see the fault occurrence. The communication control unit 8 backs up the communication function using a normal B-system optical link.

In this state, if the link test function 11 detects a decrease in the optical level of the B system optical link and a failure occurs, the link selection mechanism receives a failure notification, but switching is not performed because both systems have a failure. The failure signal of the communication control unit 8 reaches the repeater 15 through the AUI circuit 14, and the repeater 15 performs processing as a failure of the optical link.

If there is a recovery of the A system optical link from the state of failure of both systems, a signal from the link test function 6
Switching occurs and communication becomes possible using the A system optical link. 2, the FOMAU 1 of FIG. 1 is connected to the repeater 15 and forms the first segment together with the DTEs 18 to 20, and has the same function as that of FIG.
And repeaters 17, DTEs 21, 2 connected to it
2 to form a second segment, the first segment and the second segment FOMAU1 and FOMAU16
Are connected by two pairs of optical fiber cables, an A system optical link and a B system optical link. A system optical link and B
The optical links are physically separated from each other,
It can be expected that safety will increase.

When using the FOMAU of this system, when the optical fiber cable of the receiving side of the A-system optical link of the FOMAU of the own side is cut off from the repeater, the fault of the A-system optical link is recognized when transmitting by itself. Therefore, the transmission is switched to the B system, and the other party is also switched to the B system accordingly. However, after the occurrence of the failure, the other party has not recognized the failure of the A system before the first transmission. Therefore, there is a high possibility that the transmission from the other party will be transmitted to the A system, and the problem that the packet cannot be received may occur.

As one means for avoiding this, in the system which has recognized the fault, the pulse signal for link test is temporarily interrupted, the other side is switched to the other system, and then the link test pulse signal is sent again. A method of restarting and preparing for recovery from the failure may be adopted. The interruption period should be the shortest time that is sufficient to detect the occurrence of a failure and complete the switching.

(Second Embodiment) Next, a second embodiment will be described with reference to the drawings. FIG. 4 is a block diagram showing a second embodiment of the present invention.

In FIG. 4, an optical fiber medium connecting device (hereinafter referred to as FOMAU) 51 of the present invention is an electro-optical converter (hereinafter referred to as A type optical link) connected to a first optical fiber link (hereinafter referred to as A system optical link). A medium connection interface (hereinafter referred to as MDI) 52 including an EO) 53 and an optical-electrical converter (hereinafter referred to as OE) 54, and an input level of an optical signal received by the OE 54 are monitored to be below a certain level. And a light level drop detection circuit 55 for generating an alarm signal,
An MDI 56 composed of EO 57 and OE 58 connected to a second optical fiber link (hereinafter referred to as B system optical link),
The input level of the optical signal received by the OE 58 is monitored, and an optical level drop detection circuit 59 that generates an alarm signal when the level falls below a certain level, and the alarm signals of the optical level drop detection circuits 55 and 59 are monitored to monitor the A system optical signal. A link selecting mechanism 60 for selecting which of a link and a B-system optical link the received signal from which is used, and a connection signal for connecting the received signal from the MDI selected by the link selecting mechanism 60 to the communication controller 62 Received signal switching circuit 61, repeater 65 and A
The communication control unit 62 is connected via the UI circuit 64 and controls the transmission data to the EO 53 and EO 57 and the reception data switched.

Further, the communication control unit 62 has a link test function 63 equivalent to the ISO8802-3FOIRL standard as in the case of the first embodiment, and generates a pulse signal for the link test of the A system and the B system and is used for both links. When the optical level is lowered, the AUI circuit 64 can generate a fault signal (SQE) to the repeater 65.

When this embodiment is applied to an actual network, the configuration is the same as in FIG. However, in this case FO
FOMAU5 at MAU1 and FOMAU16
1 and its equivalent.

Upon receiving the transmission data from the repeater 65, the FOMA U51 of this embodiment drives the EO 53 and the EO 57 to constantly supply the transmission data to both the A-system and B-system optical links. At the time of receiving an optical signal, if there is no failure in both the A-system optical link and the B-system optical link, the reception signal is input from the OE 54 and OE 58 to the reception signal switching circuit 61. Since the optical level drop detection circuits 55 and 59 both notify the link selection mechanism 60 that there is no failure, the link selection mechanism 60 drives the reception signal switching circuit 61 based on a predetermined priority level for reception. One of the signals is sent to the communication control unit 62
Connect to.

For example, if the priority level of the A system is higher than that of the B system, the reception signal of the A system optical link when both systems are normal,
That is, the link selection mechanism 60 connects the reception signal switching circuit 61 so that the signal from the OE 54 is connected to the communication control unit 62.
To set. If the level of the reception signal of the OE 54 does not reach the level of the optical reception level reduction detection circuit 55 due to the disconnection of the A system optical link or the like in that state, the optical level reduction signal is notified to the link selection mechanism 60 and the link selection mechanism 60.
Controls the reception signal switching circuit 61 so that the reception signal from the B-system optical link, that is, the reception signal from the OE 58 is connected to the communication control unit 62.

When a failure occurs in both the optical link systems, the link level selection mechanism 60 includes the optical level drop detecting circuits 55 and 5.
Since the optical level lowering signals are notified from both 9 in this case, the failure is notified to the link test function 63 without controlling the reception signal switching circuit 61.

The link test function 63 generates a failure signal (SQE) to the repeater 65 via the AUI circuit 64 when both systems fail. In this state, if either one of the optical links recovers, the recovered system is used to recover the transmission / reception function.

[0032]

As described above, the optical fiber medium connection device of the present invention is equipped with a single repeater connection port and two systems of optical fiber medium connection interfaces, and can be used for one system of two systems. Even if a failure occurs, as long as the other system is normal, the faulty system is automatically blocked and switched to the normal system in the optical fiber medium connection device, and communication capacity can be maintained. , The optical inter-repeater link transmission medium can be easily duplicated without adding any function to the repeater or other network equipment connected to the segment, and the switching work at the time of failure is not necessary. It is possible to improve the fault tolerance, maintainability, and usability of the network without stopping the network.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing an example of a network configuration using an embodiment of the present invention.

FIG. 3 is a configuration diagram when a conventional device is used.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 1 optical fiber medium connection device (FOMAU) 2 MDI 3 communication control unit 4 EO 5 OE 6 link test function 7 MDI 8 communication control unit 9 EO 10 OE 11 link test function 12 link selection mechanism 13 signal switching circuit 14 AUI circuit 15 repeater 16 FOMAU 17 repeater 18 to 22 DTE 23, 25 FOMAU 24, 26 repeater 51 FOMAU 52 MDI 53 EO 54 OE 55 optical level drop detection circuit 56 MDI 57 EO 58 OE 59 optical level drop detection circuit 60 link selection mechanism 61 received signal switching Circuit 62 Communication control unit 63 Link test function 64 AUI circuit 65 Repeater

Claims (1)

[Claims] 1. An optical interrepeater having a pair of medium connection interfaces, a pair of link test functions, a link selection mechanism, and a signal switching mechanism, for connecting segments of a bus type local area network with an optical fiber cable. An optical fiber medium connecting device for a link, wherein a pair of medium connecting interfaces is connected to a double-structured optical fiber link, and a pair of link test functions operates a double-structured optical fiber link. The link selection mechanism determines the fiber optic link to be used according to the link test result, and the signal switching mechanism determines one of the duplex configurations. An optical fiber medium connection device for selecting an optical fiber link.