JP2859177B2 - Optical transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a CATV,
In particular, the present invention relates to a configuration of an optical transmission line for improving the reliability of an optical transmission system in an optical / coaxial hybrid (HFC) transmission system.

2. Description of the Related Art Conventionally, the main purpose of a CATV system is video distribution, and a video signal is distributed from a center through a transmission line extending in a tree shape from a single transmission line. In the conventional system, the downstream transmission path is mainly used for video distribution and maintenance. However, the upstream transmission path is not given much importance, for example, for the purpose of self-produced video relay and maintenance.

On the other hand, recently, experiments for commercializing two-way communication services such as cable videophone, television shopping, video games, and VOD have been actively conducted, and practical use of these communication services is expected in the very near future. Have been. In such communication services, it is essential to construct a highly reliable transmission system that minimizes the deterioration of communication quality due to failures of cables and devices constituting a transmission path.

However, there has been little study on a configuration for improving the reliability of the transmission path of such a two-way communication service. In a conventional tree-shaped transmission line configuration or a star-type transmission line configuration for an HFC system, when a communication service is introduced, when a failure occurs in an optical transmission line which is the most important trunk line, one or more units connected to an optical cable are connected. , And some or most of the users in the cell-divided distribution area are adversely affected by transmission quality degradation or interruption. In addition, recovery from a failure usually requires a long period of days or weeks, and the service must be stopped during the repair period.

An object of the present invention is to provide a configuration of an optical transmission line that can realize high reliability of an optical transmission system in a two-way communication service.

Means for Solving the Problems According to a configuration of the present invention for achieving the above-described object, an optical cable including one or more pairs of an optical fiber pair including an upstream optical fiber and a downstream optical fiber is provided. An optical transmission device comprising: a center unit coupled to an optical fiber; and one or more node units coupled to an optical fiber pair in the optical cable, wherein the center unit and the node unit are connected by two different paths,
(1) A center unit includes one or more optical couplers, one or more optical switches, a downstream optical transmitter coupled to a downstream optical fiber via the optical coupler, and an upstream optical fiber via the optical switch. And a second monitoring circuit coupled to the downstream optical transmitter and the upstream optical receiver and to an optical switch. The node unit includes an optical coupler, an optical switch, and the optical switch. A downstream optical receiver coupled to the downstream optical fiber; an upstream optical transmitter coupled to the upstream optical fiber via the optical coupler; and a first optical coupler coupled to the downstream optical receiver and the upstream optical transmitter and an optical switch. A monitoring circuit, wherein the first monitoring circuit receives an optical fiber fault signal from the downstream optical receiver, or receives an optical switch switching signal from the second monitoring circuit, and switches an optical switch of the node unit; A second monitor circuit for receiving an optical fiber failure signal from the upstream optical receiver or a first monitor circuit; Has a function of switching the optical switch of the center part in response to an optical switch switching signal from the optical receiver, and a function of transmitting an optical switch switching signal to the downstream optical transmitter by a signal from the upstream optical receiver. A configuration in which the distribution ratio is set such that transmission path losses of two different paths between the optical path and the center section are substantially equal to each other; and (2) the center section includes a plurality of optical couplers and a first optical coupler. A downstream optical transmitter coupled to the downstream optical fiber, an upstream optical receiver coupled to the upstream optical fiber via the second optical coupler, and a second monitor coupled to the downstream optical transmitter and the upstream optical receiver. circuit A plurality of optical switches, a downstream optical receiver coupled to the downstream optical fiber via the first optical switch, and an upstream optical transmitter coupled to the upstream optical fiber via the second optical switch. And a first monitoring circuit coupled to the downstream optical receiver and the upstream optical transmitter, wherein the first monitoring circuit receives an optical fiber fault signal from the downstream optical receiver or receives a signal from the second monitoring circuit. The second monitoring circuit has a function of receiving the optical switch switching signal and switching the optical switch of the node unit, and the second monitoring circuit has a function of transmitting the optical switch switching signal to the downstream optical transmitter by a signal from the upstream optical receiver. Each optical coupler has a configuration in which the distribution ratio is set so that the transmission path losses of two different paths between the node section and the center section are substantially equal to each other, and (3) the center section has one or more optical paths. Coupler and 1 Or a plurality of optical switches, a downstream optical transmitter coupled to the downstream optical fiber via the optical switch, an upstream optical receiver coupled to the upstream optical fiber via the optical coupler, the downstream optical transmitter and the upstream A second monitoring circuit coupled to the optical receiver and the optical switch, the node unit comprising: an optical coupler; an optical switch; a downstream optical receiver coupled to the downstream optical fiber via the optical coupler; And an upstream optical transmitter coupled to the upstream optical fiber via the optical fiber switch; and a first monitoring circuit coupled to the downstream optical receiver and the upstream optical transmitter and the optical switch. A function of switching an optical switch of a node unit in response to an optical fiber failure signal of the above or an optical switch switching signal from a second monitoring circuit, and switching of an optical switch by a signal from a downstream optical receiver The second monitoring circuit receives an optical fiber failure signal from the upstream optical receiver, or receives an optical switch switching signal from the first monitoring circuit, and receives the signal from the first monitoring circuit. The optical coupler has a function of switching an optical switch and a function of transmitting an optical switch switching signal to a downstream optical transmitter based on a signal from an upstream optical receiver. Each optical coupler transmits two different paths between a node unit and a center unit. A configuration in which a distribution ratio is set so that path losses are substantially equal to each other; and (4) a center unit includes a plurality of optical switches and a downstream optical transmitter coupled to a downstream optical fiber via the first optical switch. An upstream optical receiver coupled to an upstream optical fiber via a second optical switch; and a second monitoring circuit coupled to the downstream optical transmitter and the upstream optical receiver. Coupler and A downstream optical receiver coupled to the downstream optical fiber via the optical coupler, an upstream optical transmitter coupled to the upstream optical fiber via the second optical coupler, and coupled to the downstream optical receiver and the upstream optical transmitter. A first monitoring circuit having a function of transmitting an optical switch switching signal to an upstream optical transmitter in response to a signal from a downstream optical receiver, and a second monitoring circuit including an upstream optical receiver. And a function of receiving an optical fiber failure signal from the first monitoring circuit or an optical switch switching signal from the first monitoring circuit to switch the optical switch of the center unit. Each optical coupler has two functions between the node unit and the center unit. A configuration in which a distribution ratio is set so that transmission path losses of different paths are substantially equal to each other; and (5) a center unit includes: an optical coupler; and a downstream optical transmitter coupled to a downstream optical fiber via the optical coupler. When,
A switch for switching between the first and second upstream optical receivers by a signal from a first and second upstream optical receiver coupled to an upstream optical fiber and a second monitoring circuit, the downstream optical transmitter and the first And a second monitoring circuit coupled to the second upstream optical receiver and the optical switch, the node unit comprising: an optical coupler; an upstream optical transmitter coupled to the upstream optical fiber via the optical coupler; First and second downstream optical receivers coupled to a fiber, a switch for switching between the first and second downstream optical receivers based on a signal from a first monitoring circuit, and an upstream optical transmitter and first and second optical receivers A second monitoring circuit coupled to the second downstream optical receiver and the optical switch, wherein the first monitoring circuit receives an optical fiber fault signal from the downstream optical receiver or receives an optical switch from the second monitoring circuit; Receive switching signal A function of switching the optical switch of the node portion Te has a function to deliver light switching signal to the upstream optical transmitter by a signal from the downstream optical receiver, a second
The monitoring circuit receives the optical fiber failure signal from the upstream optical receiver, or receives the optical switch switching signal from the first monitoring circuit, and switches the center optical switch. It has a function of transmitting an optical switch switching signal to a downstream optical transmitter, and each optical coupler is set with a distribution ratio such that transmission path losses of two different paths between the node part and the center part are substantially equal to each other. It is each structure of a structure.

Next, a first embodiment of the present invention will be described with reference to FIG. An annular optical cable 11 constituting an optical transmission line is arranged in the service providing area. The output of the downstream optical transmitter (FTX) 1 of the center unit 13 is connected to the downstream optical fiber 9 of the optical cable 11 via the optical coupler (CP) 5, and an optical switch is provided at an arbitrary point on the transmission path of the downstream optical fiber 9. (SW) 4 is connected to a downstream optical receiver (FRX) 6 of the node unit.

In the center, an optical transmitter (FTX) 1 and an upstream optical receiver (RRX) 3 are connected to a head-end device 12.

The upstream optical transmitter (RT) of the node unit 14
X) 8 is connected to an upstream optical fiber 10 via an optical coupler (CP) 5, and an upstream optical receiver (RR) is connected via an optical switch (SW) 4 at a point on the center side of the upstream optical fiber 10.
X) Connect to 3.

A first monitoring circuit (SV1) 7 is arranged between a downstream optical receiver (FRX) 6 and an upstream optical transmitter (RTX) 8, and a downstream optical transmitter (FTX) 1 and an upstream optical receiver (RTX). RR
X) A second monitoring circuit (SV2) 2 is arranged between 3).

The light in the center section of the two different paths from the downstream optical transmitter (FTX) 1 to the downstream optical receiver (FRX) 6 of the downstream optical fiber 9 is almost equal in transmission path loss. The distribution ratio of the coupler (CP) 5 is set. In the same way as for the downstream, the optical coupler of the node part (RTX) 8 so that the transmission path loss of each of the two different paths from the upstream optical transmitter (RTX) 8 to the upstream optical receiver (RRX) 3 is almost equal. CP) 5 is set.

The downstream optical receiver (FRX) 6 has a function of determining the presence or absence of a received signal and issuing a downstream failure alarm to the first monitoring circuit (SV1) 7 when the signal is reduced or cut off.

[0008] The first monitoring circuit (SV1) 7 receives a downlink failure alarm or receives an optical switch switching signal issued from the second monitoring circuit (SV2) 2 and receives a node part optical switch (SW) 4. And a function of converting a downstream failure alarm into an optical switch switching signal and issuing the same to an upstream optical transmitter (RTX) 8.

The upstream optical receiver (RRX) 3 has a function of judging the presence or absence of a received signal and issuing an upstream failure alarm to the second monitoring circuit (SV2) when the signal is reduced or cut off.

The second monitoring circuit (SV2) 2 receives an uplink fault alarm or receives an optical switch switching signal issued from the first monitoring circuit (SV1) 7 to provide an optical switch (SW) 4 at the center. And a function of converting an upstream failure alarm into an optical switch switching signal and issuing the same to a downstream optical transmitter (FTX).

The first and second monitoring circuits 7, 2
Does not operate for a certain period of time after receiving the first fault alarm or the optical switch switching signal, even if it receives the next fault alarm or the optical switch switching signal, that is, has an inhibit function.

Next, the operation of this embodiment will be described in detail with reference to FIG. In FIG. 1, three cases in which a failure occurs on the path (here, the optical cable 11 on the upper side in FIG. 1 for both the upstream and the downstream) in which the optical switch 4 is initialized will be described. (1) At the time of failure of the downstream optical fiber 9 The downstream optical receiver (FRX) 6 determines the presence / absence of a signal received from the downstream optical fiber 9, and when the signal is reduced or cut off,
A downstream fault alarm is issued to the first monitoring circuit (SV1) 7. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into an optical switch switching signal, and issues it to the upstream optical transmitter (RTX) 8. The direction is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 1). The optical switch switching signal is transmitted from an upstream optical transmitter (RTX) 8-node unit optical coupler (C
P) 5-upstream optical fiber 10 (upper optical cable in FIG. 1)-center optical switch (SW) 4-input to the second monitoring circuit (SV2) 2 via upstream optical receiver (RRX) 3. . The monitoring circuit 2 receives the optical switch switching signal and switches the optical switch (SW) 4 on the center side to the opposite direction from the initial setting (in this embodiment, the lower optical cable in FIG. 1).

The above operation completes the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. (2) When a failure occurs in the upstream optical fiber 10 The upstream optical receiver (RRX) 3 determines the presence or absence of a received signal from the upstream optical fiber 10 and, when the signal is reduced or cut off, performs a second monitoring of the upstream failure alarm. Issue to circuit (SV2) 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues it to the downstream optical transmitter (FTX) 1. Then, the center side optical switch (SW) 4 In the direction opposite to the initial setting (FIG.
Switch to the lower optical cable). The optical switch switching signal is transmitted by a downstream optical transmitter (FTX) 1, a center optical coupler (CP) 5, a downstream optical fiber 9 (an upper optical cable in FIG. 1), a node side optical switch (SW) 4, and a downstream optical receiver ( The signal is input to the first monitoring circuit (SV1) 7 via the (FRX) 6. The first monitoring circuit (SV1) 7 receives the optical switch switching signal and sets the node optical switch (SW) 4 in a direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 1).
Switch to

The above operation completes the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. (3) When a failure occurs in the downstream optical fiber 9 and the upstream optical fiber 10 The downstream optical receiver (FRX) 6 determines the presence / absence of a signal received from the downstream optical fiber 9, and when the signal is reduced or cut off,
A downstream fault alarm is issued to the first monitoring circuit (SV1) 7. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into an optical switch switching signal, and issues it to the upstream optical transmitter (RTX) 8. The direction is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 1). The optical switch switching signal is transmitted from an upstream optical transmitter (RTX) to an optical coupler (C
P) 5-upstream optical fiber 10 (upper optical cable in FIG. 1)-center optical switch (SW) 4-input to the second monitoring circuit (SV2) 2 via upstream optical receiver (RRX) 3. . The upstream optical receiver (RRX) 3 determines the presence or absence of a received signal from the upstream optical fiber 10 and, when the signal is reduced or cut off, issues an upstream failure alarm to a second monitoring circuit (SV).
2) Depart at 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues it to the downstream optical transmitter (FTX) 1. Then, the center side optical switch (SW) 4 Is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 1). The optical switch switching signal is transmitted by a downstream optical transmitter (FTX) 1, a center optical coupler (CP) 5, a downstream optical fiber 9 (an upper optical cable in FIG. 1), a node side optical switch (SW) 4, and a downstream optical receiver ( FRX) 6 and the first monitoring circuit (S
V1) is input to 7.

If the initially set faults in the downstream optical fiber 9 and upstream optical fiber 10 occur at exactly the same time, the optical switch switching signal does not reach the counterpart monitoring circuit, and the first monitoring circuit (SV1) 7 in the node unit. Switches the node unit optical switch (SW) 4 in a direction opposite to the initial setting, and similarly, the second monitoring circuit (SV2) 2 in the center unit switches the center unit side optical switch (SW) 4 in a direction opposite to the initial setting.

The above operation completes the path switching operation from the upper path including the failure of the optical cable 11 in FIG. 1 to the lower path without the failure.

However, in the above cases (1), (2) and (3), the first monitoring circuit (SV1) 7 outputs the downstream switch alarm or the optical switch switching signal from the second monitoring circuit (SV2) 2. During a certain time after the node unit optical switch (SW) 4 is switched in the direction opposite to the initial setting in response to the signal which has arrived earlier, no operation is performed even if a failure alarm or an optical switch switching signal is received.

Similarly, the second monitoring circuit (SV2) 2
The center optical switch (SW) 4 is switched in the opposite direction to the initial setting in response to a signal that arrives earlier, either the uplink failure alarm or the optical switch switching signal from the first monitoring circuit (SV1) 7, and then continues for a certain period of time. No operation is performed even if a failure alarm or an optical switch switching signal is received.

The reason is as follows. After sending the optical switch switching signal to the optical transmitter, the monitoring circuit switches the optical switch in the opposite direction to the initial setting, but then receives an optical switch switching signal from the other party and switches the optical switch again to the initial setting direction. Would. For this reason, the monitoring circuit stops the operation for a certain period of time after switching the optical switch for the first time, stops the switching operation of the optical switch in this transmission system, and fixes the optical switch in the direction in which it was switched first. When a failure occurs in both the downstream and upstream optical fibers, the optical switch switching signal from the other party may arrive earlier depending on the timing of the failure and other conditions. Even in this case, the monitoring circuit switches the optical switch according to the signal that has arrived earlier.

Next, a second embodiment of the present invention will be described with reference to FIG. An annular optical cable 11 constituting an optical transmission line is arranged in the service providing area. Center part 13
Output of the downstream optical transmitter (FTX) 1 to an optical coupler (CP)
5 and connected to the downstream optical fiber 9 of the optical cable 11 at an arbitrary point on the transmission path of the downstream optical fiber 9 via the optical switch (SW) 4 at the downstream optical receiver (FR) of the node unit.
X) Connect to 6.

The upstream optical transmitter (RT
X) 8 is connected to an upstream optical fiber 10 via an optical switch (SW) 5 and an upstream optical receiver (RR) is connected via an optical coupler (CP) 4 at a point on the center side of the upstream optical fiber 10.
X) Connect to 3.

A first monitoring circuit (SV1) 7 is disposed between the downstream optical receiver (FRX) 6 and the upstream optical transmitter (RTX) 8, and the downstream optical transmitter (FTX) 1 and the upstream optical receiver (RTX) RR
X) A second monitoring circuit (SV2) 2 is arranged between 3).

It is to be noted that the light in the center section is set so that the transmission path loss of each of two different paths from the downstream optical transmitter (FTX) 1 to the downstream optical receiver (FRX) 6 of the downstream optical fiber 9 is substantially equal. The distribution ratio of the coupler (CP) 5 is set. Similarly to the downstream, the optical coupler of the center section is designed so that the transmission path loss of each of two different paths from the upstream optical transmitter (RTX) 8 to the upstream optical receiver (RRX) 3 is substantially equal. The distribution ratio of (CP) 5 is set.

The downstream optical receiver (FRX) 6 has a function of determining the presence or absence of a received signal and issuing a downstream failure alarm to the first monitoring circuit (SV1) 7 when the signal is reduced or cut off.

The first monitoring circuit (SV1) 7 receives the down-failure alarm or receives the optical switch switching signal issued from the second monitoring circuit (SV2) 2, and the two node unit optical switches (SV1). SW) 4 and a function of issuing an optical switch switching signal.

The upstream optical receiver (RRX) 3 has a function of determining the presence / absence of a received signal and issuing an upstream failure alarm to the second monitoring circuit (SV2) 2 when the signal is reduced or cut off.

The second monitoring circuit (SV2) 2 has a function of receiving an upstream fault alarm, converting the upstream fault alarm into an optical switch switching signal, and issuing the signal to a downstream optical transmitter (FTX).

The first and second monitoring circuits 7, 2
Does not operate for a certain period of time after receiving the first fault alarm or the optical switch switching signal, even if it receives the next fault alarm or the optical switch switching signal, that is, has an inhibit function.

Next, the operation of the second embodiment will be described in detail with reference to FIG. In FIG. 2, the optical switch 4
The following describes three cases in which a failure occurs in the route (here, the optical cable 11 on the upper side in FIG. 2 for both the upstream and the downstream) in which is initially set. (1) At the time of failure of the downstream optical fiber 9 The downstream optical receiver (FRX) 6 determines the presence / absence of a signal received from the downstream optical fiber 9, and when the signal is reduced or cut off,
A downstream fault alarm is issued to the first monitoring circuit (SV1) 7. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into an optical switch switching signal, and issues the signal to the upstream optical transmitter (RTX) 8. Then, the two node unit optical switches (SW) 4 is switched to the direction opposite to the initial setting (in the present embodiment, the lower optical cable in FIG. 2).

By the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. 2 is completed. (2) When a failure occurs in the upstream optical fiber 10 The upstream optical receiver (RRX) 3 determines the presence or absence of a received signal from the upstream optical fiber 10 and, when the signal is reduced or cut off, performs a second monitoring of the upstream failure alarm. Issue to circuit (SV2) 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues the same to the downstream optical transmitter (FTX) 1. The optical switch switching signal is transmitted from the downstream optical transmitter (FTX) 1 to the optical coupler (C
P) 5-Downlink optical fiber 9 (upper optical cable in FIG. 2)
-Node part side optical switch (SW) 4-Downlink optical receiver (F
RX) 6 and input to the first monitoring circuit (SV1) 7. The first monitoring circuit (SV1) 7 receives the optical switch switching signal and switches the two node unit optical switches (SW) 4 in the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 2).

With the above operation, the path switching operation from the upper path including the failure of the optical cable 11 in FIG. 2 to the lower path having no failure is completed. (3) When a failure occurs in the downstream optical fiber 9 and the upstream optical fiber 10 When there is a difference in the timing of occurrence of a failure, the downstream optical receiver (FRX) 6 determines whether there is a signal received from the downstream optical fiber 9, and At the time of decrease or disconnection, a down fault alarm is issued to the first monitoring circuit (SV1) 7. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into an optical switch switching signal, and transmits the upstream optical transmitter (RT
X) after issuing to 8, the two node unit optical switches (S
W) 4 is switched to the direction opposite to the initial setting (in the present embodiment, the lower optical cable in FIG. 2).

The upstream optical receiver (RRX) 3 determines the presence or absence of a received signal from the upstream optical fiber 10 and, when the signal is reduced or cut off, issues an upstream failure alarm to a second monitoring circuit (SV).
2) Depart at 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues the same to the downstream optical transmitter (FTX) 1. The optical switch switching signal is transmitted from the downstream optical transmitter (FTX) 1, center optical coupler (CP) 5, downstream optical fiber 9 (upper optical cable in FIG. 2), node side optical switch (SW) 4, downstream optical receiver ( FRX) 6 and a first monitoring circuit (SV
1) Input to 7.

However, the first monitoring circuit (SV1) 7
In response to a downstream failure alarm, an optical switch switching signal is issued,
The operation is not performed within a certain time after the two node unit optical switches (SW) 4 are switched in the direction opposite to the initial setting. Further, the second monitoring circuit (SV2) 2 receives the upstream failure alarm and sends the optical switch switching signal to the downstream optical transmitter (FT2) as described above.
X) No operation is performed within a certain period of time after issuing to (1). The reason is the same as in the case of FIG.

Similarly, in the above cases (1) and (2), the monitoring circuit does not operate for a certain period after first operating according to the fault alarm or the optical switch switching signal. The reason is the same as in the case of FIG.

If the initially set faults in the downstream optical fiber 9 and the upstream optical fiber 10 occur at exactly the same time, the optical switch switching signal does not reach the counterpart monitoring circuit, and the first monitoring circuit (SV1) 7 in the node unit. Switches the two node unit optical switches (SW) 4 in the opposite direction to the initial setting in response to the downlink failure alarm.

With the above operation, the path switching operation from the upper path including the failure of the optical cable 11 in FIG. 2 to the lower path having no failure is completed.

Next, a third embodiment of the present invention will be described with reference to FIG. An annular optical cable 11 constituting an optical transmission line is arranged in the service providing area. Center part 13
The output of the downstream optical transmitter (FTX) 1 is changed to an optical switch (S
W) Downlink optical fiber 9 of the optical cable 11 via 4)
To the downstream optical receiver (F) at the node via an optical coupler (CP) 5 at an arbitrary point on the transmission path of the downstream optical fiber 9.
RX) 6.

The upstream optical transmitter (RT
X) 8 is connected to an upstream optical fiber 10 via an optical switch (SW) 4, and an upstream optical receiver (RR) is connected via an optical coupler (CP) 5 at a point on the center side of the upstream optical fiber 10.
X) Connect to 3.

A first monitoring circuit (SV1) 7 is arranged between the downstream optical receiver (FRX) 6 and the upstream optical transmitter (RTX) 8, and the downstream optical transmitter (FTX) 1 and the upstream optical receiver (RTX) RR
X) A second monitoring circuit (SV2) 2 is arranged between 3).

It is to be noted that the light of the node unit is set such that the transmission path loss of each of two different paths from the downstream optical transmitter (FTX) 1 to the downstream optical receiver (FRX) 6 of the downstream optical fiber 9 is substantially equal. The distribution ratio of the coupler (CP) 5 is set. In the same manner as in the case of the downstream, the optical coupler of the center unit (uplink) so that the transmission path loss of each of the two different paths from the upstream optical transmitter (RTX) 8 to the upstream optical receiver (RRX) 3 is substantially equal. CP) 5 is set.

The downstream optical receiver (FRX) 6 has a function of determining the presence or absence of a received signal and issuing a downstream failure alarm to the first monitoring circuit (SV1) 7 when the signal is reduced or cut off.

The first monitoring circuit (SV1) 7 receives the down-failure alarm or receives the optical switch switching signal issued from the second monitoring circuit (SV2) 2, and receives the node part optical switch (SW) 4 And a function of converting a downstream failure alarm into an optical switch switching signal and issuing the same to an upstream optical transmitter (RTX) 8.

The upstream optical receiver (RRX) 3 has a function of determining the presence or absence of a received signal and issuing an upstream failure alarm to the second monitoring circuit (SV2) when the signal is reduced or cut off.

The second monitoring circuit (SV2) 2 receives an uplink fault alarm or receives an optical switch switching signal issued from the first monitoring circuit (SV1) 7 to provide an optical switch (SW) 4 in the center. And a function of converting an upstream failure alarm into an optical switch switching signal and issuing it to the downstream optical transmitter (FTX) 1.

The first and second monitoring circuits 7, 2
Does not operate for a certain period of time after receiving the first fault alarm or the optical switch switching signal, even if it receives the next fault alarm or the optical switch switching signal, that is, has an inhibit function.

Next, the operation of the third embodiment will be described in detail with reference to FIG. In FIG. 3, the optical switch 4
The following describes three cases in which a fault occurs in the path (here, the optical cable 11 on the upper side in FIG. 3 in both the upstream and downstream directions) in which the initialization is performed. (1) At the time of failure of the downstream optical fiber 9 The downstream optical receiver (FRX) 6 determines the presence / absence of a signal received from the downstream optical fiber 9, and when the signal is reduced or cut off,
A downstream fault alarm is issued to the first monitoring circuit (SV1) 7. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into an optical switch switching signal, and issues it to the upstream optical transmitter (RTX) 8. The direction is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 3). The optical switch switching signal is transmitted to the upstream optical transmitter (RTX) 8-node optical switch (SW) 4-upstream optical fiber 10 (upper optical cable in FIG. 3)-center optical coupler (CP) 5-upstream optical receiver (RRX). ) 3 to the second monitoring circuit (SV2) 2. The monitoring circuit 2 receives the optical switch switching signal and switches the optical switch (SW) 4 on the center side to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 3).

With the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path having no failure in FIG. 3 is completed. (2) When a failure occurs in the upstream optical fiber 10 The upstream optical receiver (RRX) 3 determines the presence or absence of a received signal from the upstream optical fiber 10 and, when the signal is reduced or cut off, performs a second monitoring of the upstream failure alarm. Issue to circuit (SV2) 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues it to the downstream optical transmitter (FTX) 1. Then, the center side optical switch (SW) 4 In the direction opposite to the initial setting (in this embodiment, FIG.
Switch to the lower optical cable). The optical switch switching signal is transmitted by a downstream optical transmitter (FTX) 1, a center optical switch (SW) 4, a downstream optical fiber 9 (upper optical cable in FIG. 3), a node side optical coupler (CP) 5, and a downstream optical receiver ( The signal is input to the first monitoring circuit (SV1) 7 via the (FRX) 6. The first monitoring circuit (SV1) 7 receives the optical switch switching signal and sets the node unit optical switch (SW) 4 in a direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 3).
Switch to

By the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. 3 is completed. (3) When there is a failure in the downstream optical fiber 9 and the upstream optical fiber 10 A case where there is a difference in the timing of failure occurrence will be described. The downstream optical receiver (FRX) 6 determines the presence or absence of a received signal from the downstream optical fiber 9 and issues a downstream failure alarm to the first monitoring circuit (SV1) 7 when the signal is reduced or cut off. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into an optical switch switching signal, and issues it to the upstream optical transmitter (RTX) 8.
W) 4 is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 3). The optical switch switching signal is transmitted from the upstream optical transmitter (RTX) 8 to the node unit optical switch (SW).
4-Upstream optical fiber 10 (upper optical cable in FIG. 3) -Center optical coupler (CP) 5-Upstream optical receiver (RRX)
3 and is input to the second monitoring circuit (SV2) 2. The upstream optical receiver (RRX) 3 includes an upstream optical fiber 10
It determines the presence or absence of a received signal from the controller, and issues an uplink failure alarm to the second monitoring circuit (SV2) 2 when the signal is reduced or cut off. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues it to the downstream optical transmitter (FTX) 1. Then, the center side optical switch (SW) 4 Is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 3). The optical switch switching signal is transmitted by a downstream optical transmitter (FTX) 1, a center optical switch (SW) 4, a downstream optical fiber 9 (upper optical cable in FIG. 3), a node side optical coupler (CP) 5, and a downstream optical receiver ( The signal is input to the first monitoring circuit (SV1) 7 via the (FRX) 6.

If the initially set faults in the downstream optical fiber 9 and upstream optical fiber 10 occur at exactly the same time, the optical switch switching signal does not reach the counterpart monitoring circuit, and the first monitoring circuit (SV1) 7 in the node unit. Switches the node unit optical switch (SW) 4 in a direction opposite to the initial setting, and similarly, the second monitoring circuit (SV2) 2 in the center unit switches the center unit side optical switch (SW) 4 in a direction opposite to the initial setting.

The above operation completes the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG.

However, in the case of FIG. 3, as in the example of FIG. 1, the two monitoring circuits stop operating for a certain period of time after operating with the first signal.

Next, a fourth embodiment of the present invention will be described with reference to FIG. An annular optical cable 11 constituting an optical transmission line is arranged in the service providing area. Center part 13
The output of the downstream optical transmitter (FTX) 1 is changed to an optical switch (S
W) Downlink optical fiber 9 of the optical cable 11 via 4)
To the downstream optical receiver (F) at the node via an optical coupler (CP) 5 at an arbitrary point on the transmission path of the downstream optical fiber 9.
RX) 6.

The upstream optical transmitter (RT
X) 8 is connected to an upstream optical fiber 10 via an optical coupler (CP) 5, and an upstream optical receiver (RR) is connected via an optical switch (SW) 4 at a point on the center side of the upstream optical fiber 10.
X) Connect to 3.

A first monitoring circuit (SV1) 7 is arranged between the downstream optical receiver (FRX) 6 and the upstream optical transmitter (RTX) 8, and the downstream optical transmitter (FTX) 1 and the upstream optical receiver ( RR
X) A second monitoring circuit (SV2) 2 is arranged between 3).

It is to be noted that the light of the node unit is so set that the transmission path loss of each of the two different paths from the downstream optical transmitter (FTX) 1 to the downstream optical receiver (FRX) 6 of the downstream optical fiber 9 is substantially equal. The distribution ratio of the coupler (CP) 5 is set. In the same way as for the upstream, the node-side optical coupler (such that the transmission path loss of each of two different paths from the upstream optical transmitter (RTX) 8 to the upstream optical receiver (RRX) 3 is substantially equal to each other. CP) 5 is set.

The downstream optical receiver (FRX) 6 has a function of determining the presence or absence of a received signal and issuing a downstream failure alarm to the first monitoring circuit (SV1) 7 when the signal is reduced or cut off.

The first monitoring circuit (SV1) 7 has a function of receiving a downstream fault alarm, converting the downstream fault alarm into an optical switch switching signal, and issuing the signal to an upstream optical transmitter (RTX) 8.
The upstream optical receiver (RRX) 3 has a function of determining the presence / absence of a received signal, and issuing an upstream failure alarm to the second monitoring circuit (SV2) 2 when the signal is reduced or cut off.

The second monitoring circuit (SV1) 2 receives the upstream fault alarm or receives the optical switch switching signal issued from the first monitoring circuit (SV1) 7, and receives the two center optical switches (SW). And (4) a function for switching (4).

The first and second monitoring circuits 7, 2
Does not operate for a certain period of time after receiving the first fault alarm or the optical switch switching signal, even if it receives the next fault alarm or the optical switch switching signal, that is, has an inhibit function.

Next, the operation of the fourth embodiment will be described in detail with reference to FIG. Referring to FIG.
The following describes three cases in which a failure occurs in the route (here, the optical cable 11 on the upper side in FIG. 4 for both the upstream and the downstream) in which is initially set. (1) At the time of failure of the downstream optical fiber 9 The downstream optical receiver (FRX) 6 determines the presence / absence of a signal received from the downstream optical fiber 9, and when the signal is reduced or cut off,
A downstream fault alarm is issued to the first monitoring circuit (SV1) 7. The first monitoring circuit (SV1) 7 receives the downstream fault alarm, converts the downstream fault alarm into an optical switch switching signal, and issues the same to the upstream optical transmitter (RTX) 8. The optical switch switching signal is transmitted from the upstream optical transmitter (RTX) 8 to the node unit optical coupler 5 to the upstream optical fiber 10 (upper optical cable in FIG. 1) to the center optical switch (SW) 4 to the upstream optical receiver (RRX) 3
Is input to the second monitoring circuit (SV2) 2 via.
The second monitoring circuit (SV2) 2 receives the optical switch switching signal and switches the two center optical switches (SW) 4 in a direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 4).

By the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. 4 is completed. (2) When a failure occurs in the upstream optical fiber 10 The upstream optical receiver (RRX) 3 determines the presence or absence of a received signal from the upstream optical fiber 10 and, when the signal is reduced or cut off, performs a second monitoring of the upstream failure alarm. Issue to circuit (SV2) 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues it to the downstream optical transmitter (FTX) 1. Then, the two center optical switches (SW) 4 is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 4).

By the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. 4 is completed. (3) When a failure occurs in the downstream optical fiber 9 and the upstream optical fiber 10 First, a case where there is a difference in the timing of occurrence of a failure will be described. The downstream optical receiver (FRX) 6 determines the presence or absence of a received signal from the downstream optical fiber 9 and issues a downstream failure alarm to the first monitoring circuit (SV1) 7 when the signal is reduced or cut off. The first monitoring circuit (SV1) 7 receives the downstream fault alarm, converts the downstream fault alarm into an optical switch switching signal, and issues the same to the upstream optical transmitter (RTX) 8. The optical switch switching signal is transmitted from an upstream optical transmitter (RTX) 8 -node unit optical coupler (CP) 5 -upstream optical fiber 10 (upper optical cable in FIG. 4) -center side optical switch (SW) 4 -upstream optical receiver ( RRX) 3 via the second monitoring circuit (SV2) 2
Is input to

The upstream optical receiver (RRX) 3 determines the presence or absence of a received signal from the upstream optical fiber 10 and, when the signal is reduced or cut off, issues an upstream failure alarm to the second monitoring circuit (SV).
2) Depart at 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into an optical switch switching signal, and issues it to the downstream optical transmitter (FTX) 1. Then, the two center optical switches (SW) 4 is switched to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 4).

However, the second monitoring circuit (SV2) 2
The operation is not performed within a fixed time after the two center optical switches (SW) 4 are switched in the opposite direction to the initial setting in response to the uplink failure alarm 8 (or the optical switch switching signal). Further, the first monitoring circuit (SV1) 7 does not operate within a certain time after issuing the optical switch switching signal. The reason is the same as in the case of FIG.

Similarly, in the above cases (1) and (2), the monitoring circuit does not operate after first operating according to the fault alarm or the optical switch switching signal. The reason is the same as in the case of FIG.

When the initially set faults in the downstream optical fiber 9 and the upstream optical fiber 10 occur at exactly the same time, the optical switch switching signal does not reach the monitoring circuit of the other party, and the second monitoring circuit (SV2) 2 of the center unit 2 Receives the upstream failure alarm or the earlier signal, and outputs the center optical switch (S
W) Switch 4 in the direction opposite to the initial setting.

The above operation completes the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG.

In the above embodiment, there is one node unit for the center unit, but a plurality of node units can be installed. In this case, a plurality of pairs of upstream and downstream optical fibers are arranged in an optical cable, and optical switches and optical couplers corresponding to the number of nodes are provided at the center. It is desirable that the plurality of nodes have any of the configurations shown in FIGS. 1 to 4 described above. However, it is technically possible to have different configurations in FIGS. 1 to 4 for each node. At this time, the monitoring circuit of the center is provided with a plurality of functions that can correspond to a plurality of types of nodes.

Next, a fifth embodiment of the present invention will be described with reference to FIG. An annular optical cable 11 constituting an optical transmission line is arranged in the service providing area. Center part 13
Output of the downstream optical transmitter (FTX) 1 to an optical coupler (CP)
5 and a first downstream optical receiver (FRX-A) 18 of the node unit and a second downstream light at an arbitrary point on the transmission path of the downstream optical fiber 9. Connect to receiver (FRX-B) 19.

In the center, the optical transmitter (FTX) 1 and the switch 15 are connected to the head-end device 12.

The upstream optical transmitter (RT
X) 8 is connected to the upstream optical fiber 10 via the optical coupler (CP) 5 and the first upstream optical receiver (RRX-A) 16 and the second upstream optical To the upstream optical receiver (RRX-B) 17.

On the node side, a first downstream optical receiver (FR
XA) 18 and a second downstream optical receiver (FRX-B) 19
Are connected to a first monitoring circuit (SV1) 7, and these optical receivers are switched by a switch 15. The switch is connected to the first monitoring circuit (SV1) 7. A second downstream optical receiver (FRX-B) 19 is coupled to the downstream optical fiber. The upstream optical transmitter (RTX) 8 is connected to the first monitoring circuit (SV1) 7. On the center side, both the first upstream optical receiver (RRX-A) 16 and the second upstream optical receiver (RRX-B) 17 use the second monitoring circuit (SRX).
V2) 2 and these optical receivers are connected to switch 1
5 is switched. The switch 15 is connected to the second monitoring circuit (SV2) 2. A first upstream optical receiver (RRX-A) 16 is coupled to the upstream optical fiber.
Further, the downstream optical transmitter (FTX) 1 is connected to the second monitoring circuit (SV
2) Connected to 2.

Two different paths from the downstream optical transmitter (FTX) 1 of the downstream optical fiber 9 to the first optical receiver (FRX-A) 18 or the second optical receiver (FRX-B) 19 The distribution ratio of the optical coupler (CP) 5 in the center portion is set so that the transmission path loss of each of them is substantially equal. As for the upstream, the upstream optical transmitter (RT
X) The node unit such that the transmission path loss of each of two different paths from the first upstream optical receiver (RRX-A) 16 to the second upstream optical receiver (RRX-A) 17 is substantially equal. The distribution ratio of the optical coupler (CP) 5 is set.

First Downlink Optical Receiver (FRX-A) 18
Has a function of judging the presence or absence of a received signal and issuing a downlink failure alarm to the first monitoring circuit (SV1) 7 when the signal is reduced or cut off.

The first monitoring circuit (SV1) 7 receives the downstream failure alarm or receives a switch switching signal issued from the second monitoring circuit (SV2) 2 and switches the node unit switch to the second downstream light. It has a function of switching to the receiver (FRX-B) 19 and a function of converting a downstream failure alarm into a switch switching signal and issuing the signal to the upstream optical transmitter (RTX) 8.

The second upstream optical receiver (RRX-B) 17
Has a function of determining the presence or absence of a received signal, and issuing an uplink failure alarm to the second monitoring circuit (SV2) 2 when the signal is reduced or cut off.

The second monitoring circuit (SV2) 2 receives the upstream failure alarm or receives the switch switching signal issued from the first monitoring circuit (SV1) 7 to switch the center switch 15 to the first upstream circuit. It has a function of switching to the optical receiver (RRX-A) 16 and a function of converting an upstream failure alarm into a switch switching signal and issuing it to the downstream optical transmitter (FTX) 1.

The first and second monitoring circuits 7, 2
Does not operate even after receiving the next fault alarm or switch switching signal within a certain period of time after receiving the first fault alarm or switch switching signal, that is, has an inhibit function.

Next, the operation of this embodiment will be described in detail with reference to FIG. In FIG. 5, three cases in which a fault occurs in the path (here, the optical cable 11 on the upper side in FIG. 5 for both upward and downward) in which the switch 15 is initialized will be described. (1) At the time of a failure of the downstream optical fiber 9 The first downstream optical receiver (FRX-A) 18 determines the presence or absence of a signal received from the downstream optical fiber 9, and issues a downstream failure alarm when the signal is reduced or cut off. First monitoring circuit (SV1) 7
To be issued. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into a switch switching signal, and issues the same to the upstream optical transmitter (RTX) 8. Then, the node unit switch 15 reverses the initial setting. The orientation is switched to the direction (in this embodiment, the lower optical cable in FIG. 5). The switch switching signal is transmitted from the upstream optical transmitter (RTX) 8-node unit optical coupler (C
P) 5-upstream optical fiber 10 (upper optical cable in FIG. 5)-input to the second monitoring circuit (SV2) 2 via the first upstream optical receiver (RRX-A) 16. The monitoring circuit 2 receives the switch switching signal and switches the center-side switch 15 in the opposite direction to the initial setting (in the present embodiment, the lower optical cable in FIG. 5).

By the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. 5 is completed. (2) When a failure occurs in the upstream optical fiber 10 The second upstream optical receiver (RRX-B) 17 determines the presence / absence of a signal received from the upstream optical fiber 10 and, when the signal is reduced or cut off, an upstream failure alarm. To the second monitoring circuit (SV
2) Depart at 2. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into a switch switching signal, emits it to the downstream optical transmitter (FTX) 1, and then turns the center-side switch 15 in the opposite direction to the initial setting. (In this embodiment, FIG.
Switch to the lower optical cable). The switch switching signal is transmitted from the downstream optical transmitter (FTX) 1 to the center optical coupler (C
P) 5-Downlink optical fiber 9 (upper optical cable in FIG. 5)
-It is input to the first monitoring circuit (SV1) 7 via the first downstream optical receiver (FRX-A) 16. The first monitoring circuit (SV1) 7 receives the switch switching signal and switches the node unit switch 15 to the direction opposite to the initial setting (in this embodiment, the lower optical cable in FIG. 5).

With the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. 5 is completed. (3) A case where there is a difference in the timing of occurrence of a failure when a failure occurs in the downstream optical fiber 9 and the upstream optical fiber 10 will be described. The first downstream optical receiver (FR
XA) 18 determines the presence or absence of a received signal from downstream optical fiber 9, and issues a downstream failure alarm to first monitoring circuit (SV1) 7 when the signal is reduced or cut off. The first monitoring circuit (SV1) 7 receives the downstream failure alarm, converts the downstream failure alarm into a switch signal, and transmits the upstream optical transmitter (RTX).
8, the node unit switch 15 is switched to the direction opposite to the initial setting (the second downstream optical receiver 19 side, ie, the lower optical cable in FIG. 5 in this embodiment). The switch switching signal passes through an upstream optical transmitter (RTX) 8, a node unit optical coupler (CP) 5, an upstream optical fiber 10 (an upper optical cable in FIG. 5), and a first upstream optical receiver (RRX-A) 16. Then, it is input to the second monitoring circuit (SV2) 2. Second
Upstream optical receiver (RRX-B) 19 determines the presence or absence of a received signal from the upstream optical fiber 10, and when the signal is reduced or cut off, issues an upstream failure alarm to the second monitoring circuit (SV2) 2
To be issued. The second monitoring circuit (SV2) 2 receives the upstream failure alarm, converts the upstream failure alarm into a switch switching signal, emits it to the downstream optical transmitter (FTX) 1, and then turns the center-side switch 15 in the opposite direction to the initial setting. (Second upstream optical receiver 17
Side, that is, in this embodiment, the lower optical cable in FIG. 5). The switch switching signal is transmitted to the downstream optical transmitter (FT
X) 1-center optical coupler (CP) 5-downlink optical fiber 9 (upper optical cable in FIG. 5) -first monitoring circuit (SV) via first downlink optical receiver (FRX-A) 18
1) Input to 7.

When the initially set faults in the downstream optical fiber 9 and the upstream optical fiber 10 occur at exactly the same time, the optical switch switching signal does not reach the counterpart monitoring circuit, and the first monitoring circuit (SV1) 7 in the node unit. Is the node switch 15
Is switched in the opposite direction from the initial setting (from the first to the second downstream optical receiver), and the second monitoring circuit (SV
2) 2 switches the center-side switch 15 in a direction opposite to the initial setting (from the first to the second upstream optical receiver).

By the above operation, the path switching operation from the upper path including the failure of the optical cable 11 to the lower path without the failure in FIG. 5 is completed.

However, in the cases of (1), (2) and (3), the first monitoring circuit (SV1) 7 outputs the down switch alarm signal or the optical switch switching signal from the second monitoring circuit (SV2) 2. No operation is performed even if a failure alarm or an optical switch switching signal is received within a certain time after the node unit switch 15 is switched in the direction opposite to the initial setting in response to any of the earlier incoming signals.

Similarly, the second monitoring circuit (SV2) 2
The center switch 15 is switched in the opposite direction to the initial setting in response to the early arrival signal of the uplink failure alarm or the switch switching signal from the first monitoring circuit (SV1) 7, and thereafter, the failure alarm or No operation is performed even if an optical switch switching signal is received.

The reason is as described in the example of FIG. In the example of FIG. 5, a switch using an electrical means can be adopted, and there is a merit in terms of cost as compared with the case where an optical switch is used at present.

The present invention relates to a configuration of a center and a node. One node is further connected to one or a plurality of coaxial transmission line systems corresponding to each area. The coaxial transmission line system includes a plurality of amplifiers and distributes video to, for example, hundreds of households.

On the coaxial transmission line, 10 to 50 MH in the upstream
z, 70 to 550 MHz (or 750 MH
z) band is used. 10 to 50 MHz on the upstream optical transmission line (100 to several hundred MHz when multiplexing)
band z), 70 to 550 MHz in the downstream optical transmission line
A band of up to 750 MHz is used.

As the monitoring device, a known device using a comparator or the like can be used. As the optical switch, a known waveguide matrix switch, magneto-optical switch, or mechanical optical switch can be used. A known coupler such as a half mirror type can be used as the optical coupler.

According to the above-described configuration, when a failure occurs in the path in which the optical switch is initialized and the received signal is interrupted, the optical receiver automatically detects the signal drop and issues a failure alarm. To emit. The monitoring circuit converts the fault alarm into an optical switch switching signal and transfers the signal, and performs an operation of switching the optical switch from the fault path to the normal path. For this reason, the transmission service can be stopped for a very short time required for the optical switch switching operation, and a faulty path can be repaired without stopping while operating on a normal path. A reliable optical transmission system can be constructed.

Further, even if the optical cable lengths of the faulty path and the normal path are unequal, the loss of each transmission path can be equalized by setting the distribution loss of the optical coupler. Service can be maintained without losing quality.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram showing a fifth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Downlink optical transmitter (FTX) 2 Second monitoring circuit (SV2) 3 Uplink optical receiver (RRX) 4 Optical switch (SW) 5 Optical coupler (CP) 6 Downlink optical receiver (FRX) 7 First monitoring Circuit (SV1) 8 Uplink optical transmitter (RTX) 9 Downlink optical fiber 10 Uplink optical fiber 11 Optical cable 12 Headend device 13 Center unit 14 Node unit 15 Switch 16 First uplink optical receiver (RRX-A) 17 Second Upstream optical receiver (RRX-B) 18 first downstream optical receiver (FRX-A) 19 second downstream optical receiver (FRX-B)

Claims (7)

(57) [Claims] An optical cable including one or more pairs of optical fiber pairs comprising an upstream optical fiber and a downstream optical fiber;
A center portion that couples to each optical fiber in the optical cable; and one or more node portions that couple to a pair of optical fibers in the optical cable .
An optical transmission device connected by different paths, wherein a center unit includes one or more optical couplers, one or more optical switches, and a downstream optical transmitter coupled to a downstream optical fiber via the optical coupler. An upstream optical receiver coupled to the upstream optical fiber via the optical switch; and a second monitoring circuit coupled to the downstream optical transmitter and the upstream optical receiver and the optical switch. An optical switch, a downstream optical receiver coupled to the downstream optical fiber via the optical switch,
An upstream optical transmitter coupled to the upstream optical fiber via the optical coupler; and a first monitoring circuit coupled to the downstream optical receiver, the upstream optical transmitter, and an optical switch, wherein the first monitoring circuit includes a downstream optical transmitter. A function of switching an optical switch of a node unit in response to an optical fiber failure signal from a receiver or an optical switch switching signal from a second monitoring circuit; The second monitoring circuit receives an optical fiber failure signal from the upstream optical receiver,
Each optical coupler has a function of switching an optical switch in the center part in response to an optical switch switching signal from a monitoring circuit of the optical communication device and a function of transmitting an optical switch switching signal to a downstream optical transmitter by a signal from an upstream optical receiver. An optical transmission device wherein a distribution ratio is set such that transmission path losses of two different paths between a node part and a center part are substantially equal to each other. 2. An optical cable including one or more pairs of optical fibers comprising an upstream optical fiber and a downstream optical fiber;
A center portion that couples to each optical fiber in the optical cable; and one or more node portions that couple to a pair of optical fibers in the optical cable .
An optical transmission device connected via different paths, wherein a center unit includes a plurality of optical couplers, a downstream optical transmitter coupled to a downstream optical fiber via a first optical coupler, and a second optical coupler. An upstream optical receiver coupled to the upstream optical fiber, and a second monitoring circuit coupled to the downstream optical transmitter and the upstream optical receiver. The node unit includes a plurality of optical switches and a first optical switch. A downstream optical receiver coupled to the downstream optical fiber via
An upstream optical transmitter coupled to an upstream optical fiber via an optical switch, and a first monitoring circuit coupled to the downstream optical receiver and the upstream optical transmitter. Or a function of receiving an optical fiber switching signal from the second monitoring circuit and switching the optical switch of the node unit in response to the optical fiber failure signal, and the second monitoring circuit receives the signal from the upstream optical receiver. It has a function of transmitting an optical switch switching signal to a downstream optical transmitter, and each optical coupler has a distribution ratio set such that transmission path losses of two different paths between the node part and the center part are substantially equal to each other. An optical transmission device, comprising: 3. An optical cable including one or more pairs of optical fiber pairs comprising an upstream optical fiber and a downstream optical fiber;
A center portion that couples to each optical fiber in the optical cable; and one or more node portions that couple to a pair of optical fibers in the optical cable .
An optical transmission device connected by different paths, wherein a center unit includes one or more optical couplers, one or more optical switches, and a downstream optical transmitter coupled to a downstream optical fiber via the optical switches. An upstream optical receiver coupled to the upstream optical fiber via the optical coupler; and a second monitoring circuit coupled to the downstream optical transmitter and the upstream optical receiver and to an optical switch. An optical switch, a downstream optical receiver coupled to the downstream optical fiber via the optical coupler, an upstream optical transmitter coupled to the upstream optical fiber via the optical switch, the downstream optical receiver and the upstream optical transmission A first monitoring circuit coupled to the optical receiver and the optical switch, the first monitoring circuit receiving an optical fiber fault signal from the downstream optical receiver or receiving an optical switch switching signal from the second monitoring circuit. The second monitoring circuit has a function of switching the optical switch of the optical unit and a function of transmitting an optical switch switching signal to the upstream optical transmitter by a signal from the downstream optical receiver. Receiving the signal or the first
Each optical coupler has a function of switching an optical switch in the center part in response to an optical switch switching signal from a monitoring circuit of the optical communication device and a function of transmitting an optical switch switching signal to a downstream optical transmitter by a signal from an upstream optical receiver. An optical transmission device wherein a distribution ratio is set such that transmission path losses of two different paths between a node part and a center part are substantially equal to each other. 4. An optical cable including one or a plurality of optical fiber pairs including an upstream optical fiber and a downstream optical fiber,
A center portion that couples to each optical fiber in the optical cable; and one or more node portions that couple to a pair of optical fibers in the optical cable .
An optical transmission device connected by different paths , wherein the center unit includes: a plurality of optical switches; a downstream optical transmitter coupled to a downstream optical fiber via a first optical switch;
An upstream optical receiver coupled to an upstream optical fiber via an optical switch; and a second monitoring circuit coupled to the downstream optical transmitter and the upstream optical receiver. The node unit includes: a plurality of optical couplers; A downstream optical receiver coupled to the downstream optical fiber via the first optical coupler, an upstream optical transmitter coupled to the upstream optical fiber via the second optical coupler, and the downstream optical receiver and the upstream optical transmitter. A first monitoring circuit for coupling, the first monitoring circuit having a function of transmitting an optical switch switching signal to an upstream optical transmitter by a signal from a downstream optical receiver, and the second monitoring circuit including a upstream monitoring circuit And a function of receiving an optical switch switching signal from the first monitoring circuit to switch the optical switch of the center unit. Each optical coupler has two different paths between the node unit and the center unit. Transmission line loss An optical transmission device, wherein a distribution ratio is set so as to be evenly distributed. 5. A cable comprising a plurality of sets of optical fiber pair consisting of uplink optical fiber and downstream optical fiber, and a center portion that binds to the optical fibers in the optical cable, a plurality of coupling the optical fiber pairs in the optical cable It has a node part, and the center part and the node part are connected by two different routes.
The optical transmission device according to claim 1, wherein the plurality of node units include different configurations selected from the configurations of the node units according to claim 1, 2, 3, or 4. 6. An optical cable including one or a plurality of optical fiber pairs comprising an upstream optical fiber and a downstream optical fiber;
A center portion that couples to each optical fiber in the optical cable; and one or more node portions that couple to a pair of optical fibers in the optical cable .
An optical transmission device connected by different routes, wherein a center unit includes an optical coupler, a downstream optical transmitter coupled to the downstream optical fiber via the optical coupler, and first and second optical couplers coupled to the upstream optical fiber. An upstream optical receiver, a switch for switching between the first and second upstream optical receivers based on a signal from a second monitoring circuit, and a switch including the downstream optical transmitter and the first and second upstream optical receivers The second to combine
Monitoring circuit, the node unit comprises an optical coupler, an upstream optical transmitter coupled to the upstream optical fiber via the optical coupler, a first and second downstream optical receiver coupled to the downstream optical fiber, A switch for switching between the first and second downstream optical receivers by a signal from a first monitoring circuit; and a second switch coupled to the upstream optical transmitter and the first and second downstream optical receivers and the switch.
A first monitoring circuit that receives an optical fiber failure signal from a downstream optical receiver or receives a switch switching signal from a second monitoring circuit to switch a node unit switch; The second monitoring circuit has a function of transmitting a switch switching signal to the upstream optical transmitter according to a signal from the receiver, and the second monitoring circuit receives an optical fiber failure signal from the upstream optical receiver, or receives a switch signal from the first monitoring circuit. It has a function of switching the switch of the center unit in response to the switching signal, and a function of transmitting a switch switching signal to the downstream optical transmitter by a signal from the upstream optical receiver. An optical transmission device, wherein a distribution ratio is set such that transmission path losses of two different paths are substantially equal to each other. 7. The optical transmission device according to claim 6, wherein one or a plurality of coaxial transmission systems are coupled to each node unit.