JPH1065698A - Branch type optical communication device - Google Patents

Abstract

(57) [Summary] (With correction) [PROBLEMS] To provide a dummy time for avoiding signal collision due to delay of signal light in a time slot, resulting in poor signal transmission efficiency. SOLUTION: A transmission master station 1 automatically measures a transmission line length of an annular trunk optical transmission line 2 and sends out an identification signal at a time interval corresponding to the transmission line length. A signal is received and its time interval is measured, and the transmission timing of the packet signal is delayed with respect to the frame timing information of the time division multiplexed signal output from the transmission master station 1 by the time interval of the identification signal and transmitted. The transmission master station 1 sends different identification signals from the beginning and end of the trunk optical transmission line 2, and
When the communication is performed with reference to the start end (end), the packet signal is transmitted with a time interval between the identification signal from the start end (end) and the identification signal from the end (start). This is a timing delay time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branch type optical communication apparatus, in which one master station (transmission master station) has at least one or more slave stations (transmission slave stations). One or more slave stations are connected to the optical fiber transmission line connected to the slave station via an optical splitter, so that signals can be transmitted from the master station to the slave stations, and from each slave station to the master station. The signal transmission from the slave station to the master station adopts a packet method by time division multiplexing.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a branch type optical communication apparatus. A monitoring system master station group A including a plurality of monitoring system master stations and a plurality of monitoring system slave stations B are composed of a transmission master station C. And can communicate with each other via the transmission slave station D.
A signal output from any of the master stations in the monitoring system master station group A to the monitoring system slave station B is transmitted from the transmission master station C to another monitoring station in the monitoring system master station group A. The signal is time-division multiplexed together with the signal output to B and output to the downstream trunk optical fiber transmission line E, is split by the optical splitter G on the way, and is output to each transmission slave station D. Each transmission slave station D demultiplexes the received time-division multiplexed signal and, if there is a signal directed to the monitoring system slave station B which is controlled by the own station (transmission slave station D), demultiplexes the signal. It is sent to the monitoring system slave station B. On the other hand, a signal output from one of the monitoring system slave stations B to the master station in the monitoring system master station group A is transmitted from the transmission slave station D to the other monitoring system slave station B in the monitoring system master station group A. Is packetized together with a signal or the like output to the master station, and the packet signal is joined to the upstream trunk optical fiber transmission line F via the optical branching device G. In this case, the packet signal transmission timing is set so that the merged packet signal does not collide with the packet signal from another transmission slave station D.
The transmission master station C deciphers the packet of the received packet signal and outputs the packet to the master station in the monitoring system master station group A to be transmitted.

When the time division multiplex channel control system is adopted in the branch type optical communication apparatus, a packet signal is transmitted from a transmission slave station D according to a time slot divided and set by a transmission master station C as shown in FIG. In this case, only one packet signal from one transmission slave station D exists in one time slot, and packet signals transmitted from different transmission slave stations D within the same time slot do not collide with each other. The time width of the time slot is defined as the time width of the packet signal plus twice or more the signal transmission time from the transmission master station C to the farthest transmission slave station D.

[0004]

In the branch type optical communication apparatus, the time width of the time slot is reduced by the time width of the packet signal in order to avoid collision of the packet signal output from the transmission slave station D to the upstream trunk optical fiber transmission line F. The time is set to the sum of the width and a dummy time that is at least twice the time required for the signal leaving the transmission master station C to reach the farthest transmission slave station D. Slots are a major problem in improving signal transmission efficiency, and in a system requiring high-speed multiplex transmission, transmission slots are greatly restricted. As for the variation correction of the transmission distance, there is a means for measuring the distance from the transmission master station C to the transmission slave station D in advance and manually setting the delay time. If the optical fiber length is changed or the transmission direction is changed, it is necessary to set again.

SUMMARY OF THE INVENTION It is an object of the present invention to automatically compensate for a variation in signal transmission delay time caused by a difference in transmission path length between a transmission master station and each transmission slave station, and to effectively use divided time slots. It is another object of the present invention to provide a branch type optical communication device capable of improving transmission efficiency.

[0006]

According to a first aspect of the present invention, there is provided a branch type optical communication apparatus comprising: a main optical line in which a start end and an end are annularly connected to a transmission master station, as shown in FIGS. Transmission line 2
And at least one or more transmission slave stations 4 via the optical splitter 3.
Is connected, and the signal transmitted from the transmission master station 1 to the transmission slave station 4 can be received by the transmission slave station 4 irrespective of whether the signal is input to any one of the start and end ends of the trunk optical transmission line 2 by the optical splitter 3. The packet signal transmitted from the station 4 to the transmission master station 1 is a branch type optical communication device that can receive the signal at the beginning and end of the trunk optical transmission line 2 by the optical splitter 3. , The signal output from the start or end of the trunk optical transmission line 2 is received at the end or start end of the optical transmission line 2, the transmission line length of the trunk optical transmission line 2 is automatically measured from the time difference, and the transmission path length is measured. The identification signals are alternately sent from the beginning and end of the trunk optical transmission line 2 at the time intervals corresponding to the following. The transmission slave station 4 receives the identification signal transmitted to the trunk optical transmission line 2 and sets the time interval. The transmission master station 1 measures the transmission timing of the packet signal of the It is characterized in that it has to be transmitted with a delay time interval content of the identification signal to the frame timing information of the time-division multiplexed signal to be output.

In the branch type optical communication apparatus according to the second aspect of the present invention, the transmission master station 1 alternately sends different identification signals from the starting end and the end of the trunk optical transmission line 2, and the transmission slave station 4
In addition to identifying whether the identification signal received via the optical splitter 3 is input from the beginning or end of the trunk optical transmission line 2, the identification signal is also input to the trunk optical transmission line 2.
When the communication is performed based on the start end of the packet signal, the time interval between the identification signal from the start end and the subsequent identification signal from the end end is defined as the delay time of the packet signal transmission timing,
When communication is performed with reference to the end of the trunk optical transmission line 2, the time interval between the identification signal from the end and the subsequent identification signal from the start is set as the delay time of the packet signal transmission timing. It is assumed that.

[0008]

FIG. 3 shows an embodiment of a branch type optical communication apparatus according to the present invention. The branch type optical communication device includes a monitoring system master station group 15 including a plurality of monitoring system master stations, a transmission master station 1 that integrates transmission / reception signals of each monitoring system master station, A trunk optical transmission line 2 having a ring shape by connecting the terminals, a plurality of transmission slave stations 4 connected via an optical splitter 3 and a branch optical transmission line 17 in the middle of the trunk optical transmission line 2; It comprises a monitoring system slave station 16 connected to each of the slave stations 4.

The trunk optical transmission line 2 and the branch optical transmission line 17
Has a downlink for transmitting the signal light from the transmission master station 1 to the transmission slave station 4 and an uplink for transmitting the signal light from the transmission slave station 4 to the transmission master station 1. The configuration is such that the uplink and the downlink are realized by independent optical fibers. Therefore, the trunk optical transmission line 2 is composed of the upstream optical fiber 10 and the downstream optical fiber 11, and the branch optical transmission line 17 is also composed of the upstream optical fiber 18 and the downstream optical fiber 19. The device 3 also includes an optical splitter 12 for upstream and an optical splitter 13 for downstream.

The upstream optical branching unit 12 is a combination of a 2: 2 branching unit and a 2: 2 branching unit, and as shown in FIG. The signal light transmitted to the optical fiber 18 is multiplexed and propagated to the upstream optical fiber 10 on the main line side as clockwise light and counterclockwise light. The downstream optical branching device 13 is a combination of a 2: 1 branching device, and both the signal light transmitted as clockwise light and the signal light transmitted as clockwise light to the downstream optical fiber 11 on the trunk side are respectively provided. In the same manner, the optical fiber is branched and propagated to the downstream optical fiber 19 on the branch line side.

The transmission master station 1 has optical receivers R at both the start and end of the upstream optical fiber 10 connected to the same station 1.
A and RB are provided, and any of them can receive signal light. That is, the signal light output from the transmission slave station 4 and transmitted clockwise through the upstream optical fiber 10 and the signal light transmitted counterclockwise are received in the same manner from either the beginning or end of the fiber 10. I can do it.

The transmission master station 1 has an optical transmitter T at both the beginning and end of the downstream optical fiber 11 connected to the same station 1.
A and TB are provided, from which signal light can be output, and the signal light can be transmitted to the downstream optical fiber 11 as clockwise light or as counterclockwise light. It is. As a result, the transmission slave station 4 can receive any signal light due to the characteristics of the optical splitter 13. An optical receiver RM is provided at the start and end of the downstream optical fiber 11 via an optical splitter 20, respectively, and the signal light output from the optical transmitter TA on the start end is transmitted to the end of the downstream optical fiber 11 at the end. The signal light which can be received by the optical receiver RM and which is output from the optical transmitter TB on the terminal side is transmitted to the optical receiver RM on the start side of the downstream optical fiber 11.
So that you can receive it.

In the branch type optical communication apparatus having the above configuration, in normal times, the signal of the monitoring system master station group 15 is output from the optical transmitter TA on the start end side and received by the individual transmission slave stations 4, The signal output from each transmission slave station 4 is collectively received by the optical receiver RA on the starting end. However, in the event of a system abnormality or the like, the transmission from the optical transmitter TB on the end side is performed by the transmission slave station RA. 4 to output a signal light or an optical receiver RB
, The signal light from the transmission slave station 4 can be received, and the optical transmitter TB and the optical receiver RB can be utilized as a backup function. The transmission master station 1 to the transmission slave station 4
The signal to be transmitted is also a packet signal similar to the signal transmitted by the transmission slave station 4 to the transmission master station 1, but the transmission master station 1 may be a continuous signal other than a packet signal. However, the signal output by the transmission master station 1 must include information such as a time slot number that determines the timing when the transmission slave station 4 transmits a packet signal.

In the branch type optical communication apparatus of the present invention, a predetermined identification signal A is carried on a packet signal output from the optical transmitter TA of the transmission master station 1. The packet signal including the identification signal A is received by each transmission slave station 4 through the downstream optical fiber 11, and is also received by the optical receiver RM at the end of the optical fiber 11 in the transmission master station 1. When a packet signal including the identification signal A is received by the optical receiver RM, a new identification signal B is transmitted from the optical transmitter TB to the downstream optical fiber 11, and the identification signal B is transmitted to each transmitter. The signal is received by the station 4 and received by the optical receiver RM on the start end side. Thereafter, the identification signal A is output each time the identification signal B is received by the optical receiver RA,
As a result, the identification signals A and B are alternately output to the downstream optical fiber 11 from the start end and the end. FIG. 2 shows the state of the identification signals A and B output from the transmission master station 1 and transmitted to the downstream optical fiber 11. From this figure, the transmission slave station 4 is closer to the transmission master station 1 than to the transmission master station 1. It can be seen that the reception interval of the identification signals A and B (corresponding to the delay time CN1) is long, and the farther the transmission slave station 4 is, the shorter the reception interval of the identification signals A and B is. That is, by measuring the reception intervals of the identification signals A and B, the transmission slave station 4 can measure the distance from the transmission master station 1. When the termination of the optical fiber 11 is used as a reference, that is, when the time from when the identification signal B is received to when the next identification signal A is received is used as a reference, the reception intervals of the identification signals B and A ( (Corresponding to the delay time CN2) has the opposite value in each of the transmission child stations 4. Optical fiber 11
Is effective when communication is performed by the optical transmitter TB and the optical receiver RB on the terminal side due to occurrence of an abnormality or the like in the system.

On the other hand, when each transmission slave station 4 receives the identification signals A and B alternately transmitted to the downstream optical fiber 11,
These identification signals A and B are identified, the reception timing of each identification signal A and B is detected, the time interval is measured, and this is set as the delay time CN1. Then, the transmission slave station 4 converts the data from the monitoring system slave station 16 held in the memory or the like in the own station 4 into a delay time C based on the reception time of the time slot information from the transmission master station 1.
N1 is delayed and output to the optical fiber 18. As can be seen from FIG. 2, the delay time CN1 becomes larger as it is closer to the transmission master station 1 and becomes smaller as it becomes farther from the transmission master station 1. Each transmission slave station 4 determines the respective delay time CN1 from the time slot information reception time. , And the packet signal is output, the packet transmission from the transmission slave station 4 is continuously received by the transmission master station 1 as shown in FIG. 5B. It can be seen from the comparison with the reception pattern at the transmission master station 1 by the conventional optical communication device shown in FIG. The packet transmission timing of the conventional transmission slave station 4 is transmitted immediately after receiving the time slot information from the transmission master station 1, and only one of the plurality of transmission slave stations 4 is allowed to transmit for one piece of timing information. Therefore, in this transmission method, the data arrival range at the transmission master station 1 is equal to the round trip time of the optical transmission path + the packet length, so that the time slot information interval needs to be (2τL + packet length) or more. Here, 2 indicates round trip, τ is the optical fiber delay time, and L is the maximum transmission path length.

Identification of the identification signals A and B in the transmission slave station 4 can be performed using a digital comparator or the like.
The time interval between the identification signals A and B can be measured using a counter circuit or the like. For example, when the digital comparator detects the identification signal A, the up counter circuit operates by using this as a trigger, and when the digital comparator detects the identification signal B, the up counter circuit is stopped by using this as a trigger. In the up counter circuit, a time interval from the detection of the identification signal A to the detection of the next identification signal B can be obtained as the counter value CN1, and this is recorded in a non-volatile memory or the like and held.
When the reception intervals of the identification signals A and B can be measured in this way, the transmission timing of the packet signal can be delayed using a down counter circuit or the like. For example, when the identification signal A is received by the transmission slave station 4 after the counter value CN1 is obtained, the down counter circuit outputs the counter value CN.
Call 1 and count it down. CN1 is 0
When it becomes, the down counter circuit sends out the data recorded in the memory in the transmission slave station 4 from the slave station 4. The above-described process of delaying the transmission of a packet signal by the transmission slave station 4 can of course be performed using another circuit. Means for delaying the counter value CN1 by one after the identification signal A is detected include: A data delay circuit such as a FIFO or a DPRAM may be used.

In the branch optical communication apparatus described above, the signal (identification signal A) output from the optical transmitter TA on the start end of the transmission master station 1 is received by the optical receiver RM on the end side.
The transmission path length of the trunk optical transmission path 2 (the transmission path length including the branch optical transmission path 19) can be ascertained from the signal input / output time difference. This measurement can be performed not only once but also repeatedly during the operation of the communication system. In this case, the fluctuation of the signal transmission time due to the change of the transmission path length is monitored, and the transmission is always communicated with the transmission master station 1. Efficient packet communication between the slave stations 4 can be performed. In addition, it is also possible to determine whether or not a transmission line failure has occurred by utilizing the fact that the identification signals A and B are transmitted periodically to the transmission line.

Further, the transmission master station 1 connects the optical transmitter TA with the optical transmitter T at a time interval corresponding to the transmission path length of the trunk optical transmission path 2.
B transmits identification signals A and B, and each transmission slave station 4 receives the identification signals A and B at the respective optical receivers R. The timing information is measured by a counter circuit or the like, and the time intervals CN1 and CN2 of the identification signals A and B are automatically set as the packet transmission delay time of the transmission slave station 4. Whether or not the automatic setting has been completed can also be confirmed by the transmission master station 1 by polling communication. After the sending delay time is automatically set,
The transmission master station 1 periodically transmits the identification signal A and the time slot information from the optical transmitter TA with a length equal to or longer than the packet transmitted by the transmission slave station 4. , And transmits a packet signal with a delay time of CN1 minutes. Thus, each transmission slave station 4 received by the transmission master station 1
Since the packet signals are transmitted almost continuously, there is no variation in the transmission delay time due to the difference in the transmission path length to each transmission slave station 4.

Conventionally, as shown in FIG. 5A, a long time slot corresponding to the optical transmission delay time is set, whereas in the present invention, as shown in FIG. For this reason, a short time slot can be set by reducing the dummy time for transmission, and the packet transmission of each transmission slave station 4 can be significantly speeded up as compared with the conventional case, and the throughput can be increased.

FIG. 4A shows a branch type optical communication apparatus according to the present invention.
When the communication shown in (1) is performed, for example, if a disconnection accident occurs between the transmission slave station 4 and the transmission slave station 4 in FIG. can do. In this case, since the subsequent transmission slave station 4 uses the optical transmitter TB and the optical receiver RB of the transmission master station 1 for communication, the communication path is reversed and the path length changes. Since each transmission slave station 4 sets the delay time by automatic setting, the transmission master station 1 periodically sends the identification signal A and the time slot information from the optical transmitter TA with a length equal to or longer than the transmission path length, and If the transmission master station 1 sends the identification signal B and the time slot information from the optical transmitter TB at regular intervals with a length equal to or longer than the packet signal, the transmission slave station 4 that has detected the identification signal A Thus, the delay time CN1 which is the time difference from the identification signal B can be adopted as the transmission delay time of the packet signal, and the transmission slave station 4 which has detected the identification signal B determines the time difference between the identification signal B and the identification signal A. A certain signal delay CN2 The adoption of a signal delay time, maintaining efficient communication by avoiding collision of packet signals as shown in FIG. 4 (b), can be continued.

[0021]

According to the branch type optical communication device of the present invention, the following effects can be obtained. 1. Since the packet transmission timing of each transmission slave station 4 is automatically corrected with respect to the optical transmission path length, the time slot allocated to one packet signal can be shortened, and the transmission efficiency of the packet signal can be greatly improved. it can. 2. Even if the optical transmission line length changes, the time slot can be changed in accordance with the change, so that it is possible to create a branch type optical communication system that is flexible in the change. 3. Even if there is a transmission path failure, monitoring is always performed and operation is performed automatically, so that there is an effect of improving the reliability of transmission.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a branch type optical communication device of the present invention.

FIG. 2 is a time chart for explaining signal timings in the communication device of FIG. 1;

FIG. 3 is a schematic diagram showing the entire configuration of a branch type optical communication device according to the present invention.

4A and 4B are time charts of signals in the branch type optical communication device according to the present invention, wherein FIG.
(B) shows an abnormal time.

FIG. 5A is a time chart of a signal in a conventional branch optical communication device, and FIG. 5B is a time chart of a signal in the branch optical communication device of the present invention.

FIG. 6 is a schematic diagram showing an example of a conventional branch type optical communication device.

FIG. 7 is a time chart for explaining signal timings in the branch optical communication device of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission master station 2 Trunk optical transmission line 3 Optical splitter 4 Transmission slave station

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H04B 10/12 H04J 3/00 H04L 12/56

Claims (2)

[Claims] At least one transmission slave station (4) via an optical splitter (3) to a trunk optical transmission line (2) having a start end and an end connected in a ring to the transmission master station (1). Is branched and connected,
A signal transmitted from the transmission master station (1) to the transmission slave station (4) is received by the transmission slave station (4) regardless of whether the signal is input to any of the start and end ends of the trunk optical transmission line (2) by the optical branching device (3). The packet signal transmitted from the transmission slave station (4) to the transmission master station (1) can be received by the optical branching device (3) at any of the beginning and end of the trunk optical transmission line (2). An optical communication device, wherein a transmission master station (1) receives a signal output from a start or end of a trunk optical transmission line (2) at an end or start of the same optical transmission line (2), and determines a time difference between the signals. Automatically measures the transmission line length of the trunk optical transmission line (2), transmits identification signals from the start and end of the trunk optical transmission line (2) at time intervals corresponding to the transmission line length, and transmits the identification signals to the transmission slave station (4). ) Is the trunk optical transmission line (2)
The transmission timing of the packet signal of the transmission slave station (4) is determined by the transmission timing of the time division multiplexed signal output from the transmission master station (1). A branch-type optical communication apparatus characterized in that the identification signal is transmitted with a delay of a time interval. 2. The transmission master station (1) sends different identification signals from the beginning and end of the trunk optical transmission line (2), and the transmission slave station (4) receives the identification signal via the optical splitter (3). Whether the identification signal to be input is input from the start end of the trunk optical transmission line (2) or input from the end end, and communication is performed based on the start end of the main optical transmission line (2). When performing the communication, the time interval between the identification signal from the start end and the subsequent identification signal from the end is used as the delay time of the packet signal transmission timing, and when performing communication based on the end of the trunk optical transmission line (2), 2. The branch type optical communication apparatus according to claim 1, wherein a time interval between the identification signal from the end and the subsequent identification signal from the start is set as the delay time of the packet signal transmission timing.