JP2001339420A - Method and system for optical transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of optical transmission by preventing the mutual collision of optical signals. SOLUTION: In a passive branching type optical communication system composed of star-like optical transmission lines 3 and 4, to which one optical converting master station 10 and plural optical converting slave stations 30-3n are connected through optical branchers 1 and 2, an optical signal transmitted from one optical converting slave station 30 is returned by a switcher 15 and a signal control circuit 22 of the optical converting master station 10 and a state under optical signal transmitting is reported to the respective optical converting slave stations 30-3n. When this notice is received, each of optical converting slave stations spontaneously stops the optical signal transmission of the present station and avoids the mutual collision of optical signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission line commonly used by an optical conversion master station and a plurality of optical conversion slave stations to optically transmit a signal sent from the outside to the optical conversion master station or the optical conversion slave station. The present invention relates to an optical transmission method for transmitting data via a path and a system therefor.

[0002]

2. Related Background Art Conventionally, in this type of optical transmission, there is a type in which a master station and a plurality of slave stations transmit a signal by a two-wire communication carrier system using an information line which is multidrop-connected by a metal wire. For example, among power distribution automation systems, there is a system used for a switch control system that controls the on / off state of a switch provided on a transmission and distribution line. In the above system, since a metal wire is used, a transmitted signal is affected by noise from a nearby radio station or a running truck, for example, and may not be accurately detected.

Therefore, as a countermeasure against the external noise, an optical conversion master station is connected to the master station (switch master station) and an optical converter slave station is connected to each slave station (switch slave station). Instead of this, a system has been created in which the optical conversion master station and a plurality of optical conversion slave stations are connected in a star configuration via an optical splitter provided on the optical transmission path, using an optical transmission path. In the system, periodic polling from the switch master station is transmitted from the optical conversion master station to each optical converter slave station to monitor and control the status of the switch slave station, for example, an emergency change such as a ground fault accident. When the error occurs, the spontaneous transmission from the slave station is transmitted from the optical conversion slave station to the optical conversion master station to notify the switch master station of the occurrence of the state change on the switch slave station side.

[0004]

However, when the metal line is used as an information line, the master station and each of the slave stations share a common line, so that it is possible to monitor each other's signals, so that a half-duplex line is used. Although the signals did not collide with each other, the optical splitter, due to the structure of the optical splitter, caused the optical signal to be folded back in the optical transmission between the optical conversion master station and each optical converter slave station via the optical splitter. However, when the state change occurs in a plurality of switch slave stations, there is a problem that optical signals may collide with each other on an optical transmission line.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an optical transmission method and system capable of preventing collision between optical signals and improving the reliability of optical transmission.

[0006]

In order to achieve the above object, according to the present invention, an optical conversion master station and a plurality of optical conversion slave stations are connected by an optical transmission line via an optical splitter, and the optical conversion base station is externally connected to the optical conversion station. An optical transmission for transmitting a signal transmitted to a conversion master station or an optical conversion slave station, wherein the optical conversion master station includes a first detection unit that detects an optical signal from the optical conversion slave station; Output means for returning the optical signal based on the detection result of the detecting means and outputting the optical signal to each of the slave stations, wherein the optical converter slave station detects an optical signal returned from the optical conversion master station. 2, and a stop unit for stopping transmission of an optical signal based on a detection result of the second detection unit, wherein the optical conversion master station transmits light transmitted from any of the optical conversion slave stations. The signal is turned back and output to each optical converter station, and the optical converter station is
An optical transmission method and system are provided in which an optical converter other than the optical converter that transmitted the optical signal detects the folded optical signal and stops transmitting the optical signal from its own station.

That is, in an optical repeater system in a passive branch type optical communication system in which one optical conversion master station and a plurality of optical conversion slave stations are connected by a star-shaped optical transmission line connected via an optical splitter. By returning the optical signal transmitted from one of the optical converter sub-stations to the optical conversion sub-station, a function of notifying the respective optical converter sub-stations is provided. Upon receiving the notification, the device voluntarily stops transmitting its own optical signal to avoid collision between optical signals.

[0008] In addition, a signal such as a coding rule is used for the optical signal, and the optical conversion master station detects a collision between optical signals based on a coding rule of the signal such as a coding rule from the optical conversion slave station. A first collision detecting unit that detects the collision, and the optical converter station includes a second collision detecting unit that detects a collision between the optical signals based on a code rule of the signal such as the folded code rule. , And the collision of optical signals from the optical converter station can be detected by utilizing the properties of signals such as coding rules.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an optical transmission method and system according to the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram showing an example of the configuration of an optical transmission system using the optical transmission method according to the present invention. In addition,
This embodiment will explain an example of a case where the present invention is used for a switch control system in a distribution automation system. In the figure,
In this embodiment, the optical conversion master station 10 and the plurality of optical conversion slave stations 3
0 to 3n are connected by optical transmission lines 3 and 4 via optical splitters (optical couplers) 1 and 2 to construct a star optical network. In addition, n is an arbitrary integer, and represents the number of optical converter slave stations constructing the switch control system here.

An optical conversion master station 10 includes a transformer 11 for inputting / outputting an electric signal (for example, an FSK transmission signal) to / from a switch master station (not shown) via a metal wire 1 and a predetermined transmission signal. An amplifier circuit 12 for amplifying to a level of
Transmits a transmission CD circuit 13 for detecting the presence or absence of a transmission signal, a transmission signal processing circuit 14 for performing signal encoding processing for communicating the transmission signal with the optical conversion slave stations 30 to 3n, and a transmission optical conversion master station 10. A switch 15 for switching connection to the optical transmission path 3 on the side or the optical transmission path 4 on the reception side, and an E / O circuit 16 for optically converting an electric signal passing through the switch 15 and transmitting the converted signal to the optical transmission path 4. An O / E circuit 17 for receiving and converting an optical signal transmitted from each of the optical converter stations 30 to 3n, an amplifier circuit 18 for amplifying the optical signal to a predetermined signal level, and detecting the presence or absence of an input optical signal A receiving CD circuit 19 for performing decoding processing on an optical signal which is an encoded signal;
An amplifier circuit 21 for amplifying the received reception signal to a predetermined level and outputting the amplified signal to the transformer 11; a switching control and a transmission signal processing circuit for the switch 15 based on signal detection of the transmission CD circuit 13 and the reception CD circuit 19; And a signal control circuit 22 for controlling the operation of the circuit 21. The signal control circuit 22 performs optical conversion relay of an electric signal input from the switch master station and relays an electric signal to the switch master station. In the above configuration, the transmission CD circuit 13 constitutes first detection means of the present invention, and the reception signal processing circuit 20 constitutes first collision detection means,
The switch 15 and the signal control circuit 22 constitute output means.

Since the optical converter stations 30 to 3n have the same configuration, the configuration of the optical converter station 30 will be described as a representative in this embodiment. The optical conversion slave station 30 is a metal wire 6
A transformer 31 for inputting / outputting an electric signal (for example, an FSK signal) to / from a switch slave station (not shown) through an amplifier, and an amplifier circuit 32 for amplifying a received transmission signal to a predetermined level
A transmission CD circuit 33 for detecting the presence or absence of a transmission signal; a transmission signal processing circuit 34 for performing signal encoding processing for communication with the optical conversion master station 10; An E / O circuit 35 for transmitting to the transmission line 3;
An O / E circuit 36 for converting an optical signal transmitted from the optical signal into an electric signal, a receiving CD circuit 37 for detecting the presence or absence of the optical signal, and an amplifier circuit 38 for amplifying the converted electric signal to a predetermined level A reception signal processing circuit 39 for decoding an optical signal as an encoded signal, an amplifier circuit 40 for amplifying a combined electric signal to a predetermined level, and a transmission CD circuit 33 and a reception CD circuit 37. It has a signal control circuit 41 for controlling the operation of the transmission signal processing circuit 34 and the amplifier circuit 40 based on signal detection, and performs optical conversion relay of an electric signal input from the switch slave station and transmission to the switch slave station. Relays electrical signals. In the above configuration, the reception C
The D circuit 37 constitutes a second detection means of the present invention, the reception signal processing circuit 39 constitutes a second collision detection means,
The transmission signal processing circuit 34 and the signal control circuit 41 constitute the stopping means of the present invention.

Optical conversion master station 10 and optical conversion slave stations 30 to 3n
In, the signal control circuit performs priority control of transmission and reception based on signals from the transmission CD circuit and the reception CD circuit. For example, the optical conversion master station gives priority to optical reception to an electrical signal on a first-come, first-served basis. The station gives first priority to the electric signal for optical reception. The operation of the system according to the present embodiment in such a configuration will be described below.

When an electric signal is input from the switch master station,
In the optical conversion master station 10, the transmission CD circuit 13 detects a transmission signal, the signal control circuit 22 switches the switch 15 to the transmission side, and the transmission signal processing circuit 14 encodes the electric signal. The light is converted by the O circuit 16 and transmitted to the optical transmission line 4. Then, the optical signal is distributed by the optical splitter 2 to each of the optical converter stations 30 to 3n.

Each of the optical converter slave stations 30 to 3n converts the optical signal into an electric signal by the O / E circuit 36, decodes the electric signal by the received signal processing circuit 39, and connects each of the optical signals via the metal line 6. Notify the switchgear slave station. The electric signal from the switch master station is, for example, as shown in FIG.
TX (Start of Text), address information specific to the destination switch slave station, a control type in which ACK information is indicated,
A control code indicating the control content, a data portion in which data is stored, and an ETX (End of Tex) indicating the end of the message.
t). Although the electric signal is transmitted to each switch slave station, as described above, address information unique to the switch slave station is added, and only one switch slave station whose address matches is returned. be able to.

At this time, the optical converter slave station connected to the switch slave station optically converts the electric signal and transmits it to the switch master station via the optical conversion master station. At this time, since there is only one optical converter station that transmits the optical signal, collision of the optical signal does not occur. In normal optical transmission, each switch slave station is called by polling control to perform signal transmission.
The above signal collision does not occur.

However, if a state change such as a ground fault occurs in a certain switch slave station, and a signal indicating the information (for example, a signal indicating a ground fault current) is transmitted to the switch master station, The optical conversion slave station connected to the switch slave station quickly converts the input electric signal into light and transmits the converted signal to the optical conversion master station. In the optical conversion slave station, since the signal from the outside is given priority on the first-come-first-served basis, even if the optical signal is received later, the signal from the switch slave station is not affected by cutting off the signal.

If a polling signal has already been input from the switch master station when the state change has occurred, the signal control circuit of the optical converter slave station immediately transmits the polling signal to the switch slave station. Since the transmission operation of the transmission signal processing circuit is stopped, the polling from the master station is preferentially processed by the signal detection function of the switch slave station. And after the end of the priority processing,
A notification of the state change is sent from the switch slave station.

The optical conversion master station promptly converts the optical signal received from the optical conversion slave station into an electric signal by the O / E circuit 17 and processes the signal by the reception signal processing circuit 20. While transmitting, the signal control circuit 22
Switches the switch 15 to the receiving side, and returns the signal to all the optical converter stations connected to the optical transmission line 4 in return. During the loopback, the transmission signal processing circuit 14
In this case, the transmission operation is stopped, so that the return transmission can be performed without affecting the return signal.

The information for notifying the return includes the transmission signal itself from the optical converter station, for example, as shown in FIG.
A dummy oscillator may be provided separately and a dummy signal may be oscillated based on the control of the signal control circuit 22. Since the optical transmission path is full duplex irrespective of two-fiber bidirectional / single-fiber bidirectional, there is no collision between upstream and downstream signals.

As for the optical conversion slave station connected to the switch slave station in which the state change has occurred, since the electrical signal from the switch slave station is detected first, the optical signal is received from the optical conversion master station later. Even so, the optical converter slave station controls the amplifier circuit 40 to high impedance so as not to transmit a signal to the switch slave station so as not to affect information indicating a state change. This control is performed by a logical judgment between the transmission CD circuit and the reception CD circuit.

For other optical converter slave stations, when no electric signal is received from each switch slave station,
The return signal from the optical transmission master station is passed as it is to the switch slave station connected below. As a result, the switch slave station recognizes that another switch slave station is transmitting, and outputs a signal indicating the state change even if a state change occurs while receiving a signal. Can be set not to send to stations. In addition, for example, a signal indicating a state change is a signal that the switch master station wants to recognize preferentially, so even when the optical converter slave station receives a loopback signal, a priority is given from the switch slave station to the optical converter slave station. In the optical converter receiving the signal, the transmission signal processing circuit temporarily stores the signal, and at the time when transmission to the optical conversion master station becomes possible, It is also possible to set to transmit a high signal.

As described above, the present embodiment is provided with a function of returning an optical signal transmitted from one optical converter slave station at the optical converter master station and transmitting the signal to each optical converter slave station for notification. Upon receiving the return signal, the optical converter slave station can spontaneously stop transmitting the optical signal of the local station and avoid collision between optical signals. In the present embodiment,
The case where one switch slave station is connected to one optical converter slave station has been described, but the present invention is not limited to this, and a multi-drop connection by a metal wire is provided under one optical converter slave station.
Even when a plurality of switch slave stations are connected, the optical transmission of the present invention can be performed regardless of the number of connected switches.

Next, a description will be given of how to cope with a case where a plurality of optical converter stations transmit simultaneously and an optical signal collision occurs. In the present embodiment, the properties (coding rule) of the above-mentioned coding rule signal are used by using a signal such as a coding rule for an optical signal transmitted on an optical transmission line. That is, as a means for notifying the reception of an optical signal collision on the optical transmission line and the notification to all the slave stations, the properties of signals such as coding rules are used. The code is CMI (Co
de Mark Inversion) code, MAN (Manchester) code, 4B5B code, and the like.
A case where a code is used will be described as an example.

For communication between the optical conversion slave station and the optical conversion master station, a CMI-coded optical signal is used as an optical signal. CM
The I code is a code conceived for the purpose of clock recovery and relay. The coding is such that data 0 is repeatedly inverted to '10' on the transmission line and data 1 is repeatedly inverted from '00' and '11' on the transmission line. It has regularity, is generated and processed by the transmission signal processing circuit 34 of the optical converter, and is output.

Therefore, "01" 0000 "and" 111 "
1 'is a pattern that cannot be obtained in a normal state. If the pattern is detected, this is regarded as a coding rule error. In the present embodiment, this coding rule error is actively used. When the optical conversion master station 10 receives optical signals from a plurality of optical conversion slave stations at the same time, the received signals are disturbed by the merging, and as a result appear as CMI coding rule errors. The receiving CD circuit 19 of this embodiment uses this property to detect a coding rule error and determine simultaneous incoming calls from a plurality of slave stations.

When the reception CD circuit 19 and the reception signal processing circuit 20 of the optical conversion master station detect a signal collision from a plurality of switch slave stations, the received signal (the optical signal having a coding rule error) is detected. The signal may be sent as it is, but as shown in FIG.
The dummy signal having information on the violation of the coding rule from 3 may be oscillated. For example, data 0 is sent out as binary information of '01'.

If the optical conversion slave station detects a coding rule error in the signal from the optical conversion master station 10, it may receive the electrical signal from the switch slave station earlier than the optical signal. The signal from the optical conversion master station is sent to the switch slave station. In this case, the electric signal from the switch slave station temporarily stores the signal in the transmission signal processing circuit of the optical converter slave station,
It is also possible to set so that the signal is transmitted when transmission to the optical conversion master station 10 becomes possible.

As a result, the switch slave station can recognize that a signal collision has occurred with another switch slave station. As described above, in the present embodiment, the collision of the optical signal is detected by the coding rule error generated in the signal by utilizing the property of the signal such as the coding rule, and this optical signal is transmitted back to the optical converter station because it is transmitted. The switch slave station connected to the optical converter slave station can reliably recognize the collision of the optical signal, thereby improving the reliability of signal transmission.

As described above, in the present embodiment, in a system in which a plurality of communication devices spontaneously transmit on a common metal line, the devices of the existing facilities (switch master station and switch slave station) can be modified without any modification. The electrical signal of the metal line can be optically relayed by the newly arranged optical conversion master station and optical conversion slave station. Further, in the present embodiment, the case of performing the optical relay is described, but is not limited thereto, for example, the switch master station and the optical conversion master station, the switch slave station and the optical converter slave station are configured in the same block, Optical transmission according to the present invention can be performed by a master station and a slave station having both a signal transmission / reception function and a relay function.

In this embodiment, the case where the coding rule of the CMI code is used has been described. However, the present invention is not limited to this, and it is also possible to use a coding rule such as a MAN code or a 4B5B code. The present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0031]

As described above, according to the present invention, an optical signal transmitted from a certain optical converter station is looped back by the optical converter master station and distributed to each optical converter station in the system for notification. Therefore, collision between optical signals can be prevented, and the reliability of optical transmission can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a configuration of an optical transmission system using an optical transmission method according to the present invention.

FIG. 2 is a diagram showing a frame configuration of a signal used in FIG. 1;

FIG. 3 is a configuration diagram showing another example of the configuration of the optical conversion master station shown in FIG. 1;

[Explanation of symbols]

 1, 2 branching device (optical coupler) 3, 4 optical transmission line 5, 6 metal wire 10 optical conversion master station 11, 31 transformer 12, 18, 21, 32, 38, 40 amplifier circuit 13, 33 transmission CD circuit 14, 34 transmission signal processing circuit 15 switcher 16, 35 E / O circuit 17, 36 O / E circuit 19, 37 reception CD circuit 20, 39 reception signal processing circuit 22, 41 signal control circuit 23 dummy oscillator

Continued on the front page F term (reference) 5K002 AA05 BA04 CA00 DA05 DA12 DA91 FA01 5K033 AA05 BA08 CA06 CB17 DA01 DA15 DB01 DB06 DB22 EA04

Claims (4)

[Claims] 1. An optical conversion master station and a plurality of optical conversion slave stations are connected via an optical transmission line via an optical splitter, and a signal sent from outside to the optical conversion master station or the optical conversion slave station is transmitted to the optical conversion master station. An optical transmission method for transmitting signals to each other via a transmission line, wherein the optical conversion master station wraps an optical signal transmitted from any of the optical conversion slave stations and outputs the signal to each of the optical conversion slave stations. An optical transmission method, wherein the slave station detects the folded optical signal, and the optical converter stations other than the optical converter station that transmitted the optical signal stop transmitting the optical signal from the local station. . 2. An optical signal such as a code rule is used as the optical signal, and the optical conversion master station and the optical converter slave station collide with each other based on a code rule of the transmitted code rule or the like signal. The optical transmission method according to claim 1, wherein 3. An optical conversion master station and a plurality of optical conversion slave stations are connected by an optical transmission line via an optical splitter, and a signal sent from outside to the optical conversion master station or the optical conversion slave station is transmitted to the optical conversion master station. An optical transmission system for transmitting signals to each other via a transmission path, wherein the optical conversion master station detects an optical signal from the optical conversion slave station, and a detection result of the first detection means. Output means for returning the optical signal to each of the optical conversion slave stations based on the above, wherein the optical conversion slave station detects the optical signal returned from the optical conversion master station. An optical transmission system, comprising: a stop unit for stopping transmission of an optical signal based on a detection result of the second detection unit. 4. An optical signal such as a code rule is used for the optical signal, and the optical conversion master station detects a collision between optical signals based on a code rule of the signal such as a code rule from the optical converter slave station. A first collision detecting unit that detects the collision, and the optical converter station includes a second collision detecting unit that detects a collision between the optical signals based on a code rule of the signal such as the folded code rule. The optical transmission system according to claim 3, wherein: