JPS6031132B2 - Optical communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical communication system used in a computer network.

As shown in Fig. 1, what is generally known as a small-scale optical communication system has a computer Co at the center, and a computer
,,C2...Cn (for example, KUIPNET of Kyoto University) and the center is a simple distributor A made of passive elements as shown in Figure 2, and the computer C is connected through this distributor A. , , C2 . . . Cn (for example, Xerox's FIBERNET) is a star network system.

Also, stations Cs, S, , S2 as shown in FIG.
, . . , Sn are connected in a ring and communicate with each other under the control of a control station Cs. In the system shown in FIG. 1, it is necessary to start up Co's computer even when communicating between C and C2.

Furthermore, the reliability of this Co computer governs the reliability of the entire network. The method shown in Figure 2 is superior in terms of handling and reliability because the line route is composed of passive elements A, but since there is no traffic control on the line route, the signals sent from the computer are It has the disadvantage of collision on the line.

In particular, as the communication frequency increases, collisions occur frequently and communication efficiency decreases. In the annular system shown in FIG. 3, for example, even when communicating between stations S and S2, the control station Cs and the remaining stations S
3...All stations of Sn need to be activated. Furthermore, this ring system has the disadvantage that if the line is disconnected or one of the connected stations fails, all communication becomes impossible. An object of the present invention is to provide an optical communication system that eliminates the above-mentioned drawbacks. The present invention physically has the same configuration as the optical star network shown in FIG. 2 above, but mechanically a loop is formed similarly to the system shown in FIG. 3 above.

That is, the present invention provides a network in which a plurality of stations are connected in a star shape by optical couplers and optical fiber cables, in which each station has an optical transmitter that transmits at a unique wavelength assigned to each station in advance; Each station is equipped with a plurality of optical receivers that receive signals of wavelengths specific to other stations, and a means for selecting a specific wavelength from among the received signals of a plurality of wavelengths, and each station receives signals of wavelengths specific to other stations. The feature is that if the signal is not information addressed to the station itself, a loop is formed by transmitting this information. FIG. 4 shows an embodiment of the present invention.

In the figure, 1 to 4 are stations S, , S2, and S3, respectively.
, Sn, 5 is an optical coupler A, and 6 to 9 are optical fiber cables. Each station must transmit only on a unique preassigned wavelength. Here, stations S,, S2, S3, and Sn are respectively Nagairi 2
, INPUT 3, INPUT n, INPUT. Furthermore, each station has an optical receiver for independently receiving signals of a plurality of wavelengths (though not necessarily all) other than its own wavelength. However, each station has the ability to select only one optical receiver, ie, to select a signal at one particular wavelength. Which wavelength signals each station selectively receives is determined by what kind of loop is created in this network. When creating a loop S, → S2 → S3 → Sn → S, station S2 selects wavelength input 2, and stations S3, Sn, and S select wavelength input 3, input n, and input, respectively. I'll do what I do. FIG. 5 shows an example of the configuration of a station used in the present invention.

In the figure, 21 is an input 2-optical receiver, 22 is an input-n optical receiver, and this station can receive signals of all wavelengths used in the network. 23 is a transmission/reception logic section, 24 is a unique wavelength transmitter, 25 is a signal processing device, and 26 is an optical splitter.

The transmission/reception logic section 23 has a wavelength selection circuit 27. The wavelength selection circuit 27 has a function of selecting a received signal of one of the optical receivers 20 to 22. The transmission/reception logic unit 23 supplies the selected received signal to the information processing device 25 if it is information addressed to its own station. Also, if the received signal is information destined for another station, the buffer
It is stored in shift register 28. This buffer shift register 28 has a size of one channel length. Therefore, when a station participates in the loop, its buffer shift register also participates in the loop, and the total length of the loop increases by one channel. Information to be transmitted from information processing device 25 to other stations is provided when buffer shift register 28 is empty. When that channel returns after going through the loop once, it continues to transmit information for one channel, or if transmission has ended, it returns to an empty channel and ends the process. The contents of buffer shift register 28 are provided beat by beat to transmitter 24 and converted into an optical signal at a station-specific wavelength.

This optical signal is outputted to the optical fiber cable 101 via the optical distributor 26. Now, in FIG. 4, it is assumed that station S starts transmitting to station S3 while each station is normally performing idle transmission.

First, S, inputs a signal with a source address (address of S,) and a destination address (address of S3) added.
Transmit by wavelength. This signal reaches each station via optical coupler A. For example, in S2, the received signal is received by the optical receiver 21 via the optical fiber cable 10, optical splitter 26, and optical fiber 12 shown in FIG. Since the wavelength selection circuit 27 of S2 selects the ^2 wavelength as described above, the transmission/reception logic section 23 checks the address of the received signal. Since this received signal is now to be sent to S3, the transmit/receive logic section 23 stores the received signal in the buffer shift register 28. Therefore, the received signal is supplied to the unique wavelength transmitter 24, converted into an optical signal of three input wavelengths unique to S2, and outputted to the optical fiber cable 01. At this time, in S3, the input 2 optical receiver 21 similarly receives the optical signal transmitted by S, but since the wavelength selection circuit 27 of S3 selects wavelength input 3, the transmission/reception logic section 23 does not operate. .

Similarly, Sn,S,does not operate on the optical signal transmitted by,S,. Next, the incoming three-wavelength optical signal transmitted by S2 (its contents are those transmitted by S) also reaches all the stations by the coupler A.

Of these, only S3 can selectively receive the three incoming wavelengths, so the transmission/reception logic section 23 of S3 checks this received signal. Since this received signal is from S3, the transmission/reception logic unit 23 of S3 supplies this information to the information processing device 25 of S3 via the transmission line 18, and also buffers, shifts, and sends a flag signal indicating that it has been received. Set in register 28. This flag signal is converted into an optical signal of wavelength ^n by a unique wavelength optical transmitter 24 via a transmission line 19, and then outputted to an optical fiber cable 10'. The above flag signal (
When the input wavelength (n wavelength) is converted to an input wavelength by Sn, S receives it and performs reception processing.

As a result, S confirms reception by the destination (S3) and transmits the next information. Next, in FIG. 4, S2 is S
A case will be described in which S, starts transmitting to S3 at the same time as S starts transmitting to S3.

It detects the flag indicating that the transmitted signal has been received, confirms that it has reached the other party, and then sends the next signal. At this time, S, transmits at two input wavelengths, is received and selected by S2, and this signal is
The data will be stored for 1 hour until the transmission of channel 1 to 3 is completed. Following the completion of transmission of the one channel, the storage signal is transmitted at three input wavelengths. S2 has one channel addressed to Sn, and S,
1 channel addressed to S3 is then transmitted. S3 selects a signal with three input wavelengths, and transmits the signal addressed to Sn on the first channel as it is at input N wavelength, and sends the signal addressed to S3 on the second channel to the information processing device 25 and adds a reception flag. Transmit on the 2nd channel at ^n wavelength. Sn
selects the input n wavelength signals, sends the first channel signal addressed to Sn to the information processing device 25, adds a reception flag, and transmits the wavelength, and the second channel signal enters as is and transmits the wavelength. do. S, receives and selects the signals of the input wavelength, and transmits the 11th channel signal addressed to S2 as it is at the input 2 wavelength, detects the own station source address of the 2nd channel and the reception flag of S3, and sends it to S3. After confirming that the signal has been received by the station, all signals included in channel 2 are erased and communication is terminated. If you wish to continue transmitting, you can use the second channel. −
The first channel signal transmitted from S2 with two incoming wavelengths is received and selected in S2, and is subjected to the same processing as in S above, and the communication is completed. As described above, even if a plurality of stations start transmitting at the same time, each station configures and transmits consecutive channels by temporarily storing one channel, so it is possible to prevent signal collisions on the network. In addition to the above description, the operation of the present invention will be described, which has the effect of making it possible to communicate with stations that are unable to communicate due to station failure, cable breakage, station non-participation, etc.

For example, as shown in FIG. 6, a communication operation will be described when communication becomes impossible due to a break in the optical fiber cable, a failure in station S3 itself, or a power cut.

On the network shown in FIG. 6, there are empty channel signals of wavelengths ^2, 3', and 3', and in this state, there are no signals of wavelengths n.

At this time, S selects the reception wavelength of the first station upstream of its own station to be the same as before the failure. S2 receives and selects the two incoming wavelengths in the same way as before the failure, and the Sn station should receive and select ^n under normal conditions, but since it does not exist on the network, the second upstream station from Sn's perspective is transmitting. There are three input wavelengths, and the three input wavelengths are received and selected in the first order. A new communication route is constructed avoiding such station S3 with which communication is impossible. In this state, S,
When it is transmitted to Sn, it is received and selected in S2, and is transmitted as it is at the input three wavelengths, received and selected at Sn, and a reception plug is added, and it is transmitted at the input wavelength and reaches S. The reception selects the signals of wavelengths S and 1, detects the reception flag of Sn, erases all signals including the source address, and ends the communication. As explained above, even if a non-participating station, a faulty station, or a cable break occurs, the entire system will not go down unlike in a ring network.

The features of the present invention are that collisions do not occur and that it is highly reliable.

Although this patent is physically a star network, it is functionally a loop network, which combines the best features of both network systems. That is, since it is functionally a loop network, transmission and reception are performed in an orderly manner, and there are no collisions of transmitted and received data on the bus or at the station entrance. Also, since multiple wavelengths are used, collisions at star couplers do not occur. In addition, since it is physically a star network, even if one station or optical fiber cable is disconnected, only that part will malfunction, and other parts will not be adversely affected.
All functions will not stop. Furthermore, since each station has optical receivers for all wavelengths as in the above embodiment, the signal of the wavelength unique to the station corresponding to the failure will no longer exist on the transmission path due to the above failure, so failures can be easily detected. It is possible to detect the presence of a fault and to automatically switch the wavelength selection circuit in response to this fault detection, so a new loop can be automatically created.

[Brief explanation of the drawing]

1 to 3 are diagrams showing the prior art, FIG. 4 is a diagram showing an embodiment of the present invention, FIG. 5 is a configuration diagram of a station used in the present invention, and FIG. 6 is a diagram showing an embodiment of the present invention. FIG. 3 is a diagram for explaining the operation. 1, 2, 3, 4...Station, 5...
Optical coupler, 6, 7, 8, 9... Optical fiber cable. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1 In a network in which multiple stations are connected in a star shape using optical couplers and optical fiber cables, each station has an optical transmitter that transmits at a unique wavelength assigned to each station in advance, and a network that connects other stations. a plurality of optical receivers receiving signals at wavelengths specific to the
and means for selecting a signal with a specific wavelength from among the received signals with a plurality of wavelengths, and when the signal with the wavelength selected by each station by the selection means is not information addressed to its own station, this An optical communication system characterized in that a loop is formed by transmitting information using the transmitter.