JPS60172840A - Optical star coupler with collision detection - Google Patents

Abstract

PURPOSE:To obtain an optical star coupler with low cost and high reliability by connecting one of output ports of optical star couplers to an input terminal of an optical signal collision detection/informing circuit and connecting one of input ports of an optical star coupler to an output terminal. CONSTITUTION:When collision takes place in an optical transmission line, an optical signal transmitted from communication equipments 2-1 and 2-3 confirming the reception of no signal from the optical star coupler 1 at almost same time passes through an input port 1-1 of the optical star coupler and causes collision in the optical star coupler 1. The signal enters the communication equipments 2-1, 2-2, 2-3 and Collision Detection (CD) circuit 4. The optical signals entering the CD circuit 4 and causing collision are detected for the collision, a collision notice signal is outputted from an output terminal 6 of the CD circuit 4, passes through the input port 1-1 of the optical star coupler 1 and informed to the communication equipments 2-1, 2-2, 2-3 via the optical star coupler 1. The through- put of the transmission line is improved by retransmission processing with the reception of collision informing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a CS MA/CD (Carrier 5
ense MuHi-Access / Corri
The present invention relates to a highly reliable optical star coupler in optical packet transmission using the S ion Detect41 on) procedure.

(Background Art) In contrast to the conventional polling method in which transmission is controlled by the control of a master station, a broadcasting method is known in which the output of each communication device is connected to the input of all communication devices using a star coupler. ing. In this case, collision detection is required to prevent two or more communication devices from transmitting at the same time. The communication system known as Ethernet is one such system.

As shown in FIG. 1, in the conventional optical fiber cable 3, CS
An optical star coupler 1 is used for optical transmission using the MA/C1,) procedure. There are two types of optical star couplers: passive types and active types that include optical repeaters, and those that use the passive type have a highly reliable optical transmission line. However, each communication device 2 requires an optical signal collision detection circuit (CI) circuit, and the communication device 2
The disadvantage was that the cost was high. Although active type optical star coupler 1 is still used, it has the advantage of low cost because it only requires one optical collision detection circuit in the optical star coupler. However, due to a defective element or a power outage, all communication becomes impossible, and a highly reliable transmission path cannot be realized.

(Invention Section M) In order to solve these drawbacks, the present invention is a passive optical star coupler in which an optical signal collision detection/reporting circuit is added, and will be described in detail below with reference to the drawings.

(Structure and operation of the invention) FIG. 2 shows an embodiment of the present invention, in which 0 is an optical star coupler with collision detection, l is a passive optical star coupler coupled by a light guide, and 1-1 is an optical star coupler. input port. 1-2
is the central power port of Hikari Star Kyutera, 2 is all communication equipment, 2-
1.2-2.2L3 is a transmission device, 3 is an optical fiber cable, and 4 is an optical signal collision detection/report circuit (hereinafter referred to as CD circuit).

5 is an input terminal of the CD circuit, and 6 is an output terminal of the CD circuit. In FIG. 2, communication according to the CS MA/CD procedure is shown.

An example of a case where no collision occurs in the optical transmission line is shown below. The optical signal transmitted from the communication device 2-1, which has confirmed that it does not receive the signal from the optical star coupler 1, is transmitted from the input port 1-1 of the optical star coupler → the optical star coupler 1 → the output port 1-2 of the optical star coupler. →Each communication device 2-1, 2-2,
2-3, and enters the CD circuit 4. Communication between the communication devices (2-1→2-2 or 2-1→2-3) is possible through this route.

An example of a collision occurring in an optical transmission line is shown below. Communication device 2 confirmed not to receive signals from optical star coupler l
The optical signals transmitted from -1 and 2-3 at approximately the same time pass through the optical star coupler input coupler -11-1 and cause a collision in the optical star coupler 1. This signal is transmitted to each communication device 2-
1, 2-2.

2-3 and CD circuit 4. The colliding optical signal entering the CD circuit 4 is detected as a collision, and a collision notification signal is sent to the CD circuit 4.
It is output from the output terminal 6 of the optical star coupler 1, and is reported to each communication device 2-1.2-2.2-3 via the optical star coupler 1 through the input port 1-1. Each communication device 2
-1, 2-2, and 2-3, upon reception of the collision notification signal, the throughput of the transmission path can be improved by performing retransmission processing, which is an algorithm for collisions in the CSMA/CD procedure.

As a collision notification signal, an alternating current optical pulse of a constant period is sent to all communication devices 2 for a constant period of time. In each communication device, there is a method of adding a simple circuit that determines a collision when receiving an AC optical pulse signal with a certain period (FIBERNET).
: A FIBER0PTICALETHERNET
” E, G RAWSON, 100C “8329C
1-5 (1983)). As another example, when redundant codes are used in optical signals, a high-level optical signal that includes a code conversion rule violation is used, and if the code conversion rule is detected in the code converter of each communication device, a collision is determined. It is something to do.

In this case, the high level optical signal can make the distance between the CD circuit and the optical star coupler l closer than that of the communication device 2.

The collision notification signal output from the CD circuit 5 is sent to the optical star coupler 1.
Since it returns via , a closed loop occurs and a collision condition may continue. C that can remove this condition
An example of the D circuit 4 is shown in FIG. This operation is shown below. In the CD circuit 4, the input signal at the input terminal 5 is subjected to photoelectric conversion by the optical-to-electrical converter 7, and collision detection is performed by the collision detector 8. The input signal is passed through the gate 9, drives the monostable multivibrator 1o, and opens the gate 13. . The output of the collision notification signal generator 12 passes through the open gate 13 and is converted into light by the electrical-to-optical converter 14, which is output from the output terminal 6 to report a collision. The output of the monostable multivibrator 1o is delayed by a delay device 11, and the gate 9 is closed to stop the optical signal collision detection operation.

When the collision notification signal is no longer present at the input terminal 5 of the CD circuit 4 and the output of the delay device 11 is no longer present, the gate 9 opens and the collision detection operation is restarted. In addition, delay device 1
1, the notification signal is sent out from the gate 13 and the electrical-to-optical converter 14. Output terminal 6. Input port l-
1. Optical star coupler 1. Output port 1-'2. Input terminal 5. The time it takes for the light to pass through the optical-to-electrical converter 7 and arrive at the collision detector 8) also needs to be set. If a collision signal is still detected at this point, the collision notification operation is started again. In this case, the output pulse width of the monostable multivibrator 10 is set to the communication device at the farthest end from the star coupler.
By setting the transmission time to at least twice the transmission time of \, the collision detection operation can be reliably restarted.

However, the notification signal can also be considered as a signal that strengthens the collision signal and sends it intermittently, so the monostable multivibrator 1
The output pulse width of 0 may be set to be smaller than the transmission time from the star coupler to the communication device at the farthest end.

Another example is shown in FIG. A closed loop is created by inserting a wavelength removal filter 15 between the input terminal 5 of the CD circuit and the optical-to-electrical converter 7, which allows the output light from all communication devices to pass through and removes only the wavelength λ of the output light from the CD circuit 4. Can be removed. Therefore, by detecting a collision caused by an optical signal from the communication device using the collision detector 8 and opening the gate 13 using the output thereof, a collision notification can be made as in FIG. 3. In this case, it goes without saying that the wavelength λ is a wavelength that can be received by each communication device.

(Effects of the Invention) As described above, according to the present invention, since an optical signal collision detection and notification circuit is added to a highly reliable passive optical star coupler,
A low-cost and highly reliable optical star coupler can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining a conventional optical star coupler, Fig. 2 is an embodiment of the present invention, and Figs. 3 and 4 are an embodiment of the optical signal collision detection/reporting circuit of Fig. 2. . 0... Optical star coupler with collision detection, 1... Optical star coupler, 2... All communication devices, 2-1, 2-2, 2
-3... Communication device, 3... Optical fiber, 4... Optical signal collision detection/report circuit (CD circuit), 5... Input terminal of CD circuit, 6... Output terminal of CD circuit , 7... Optical-electrical converter, 8... Collision detector, 9... Gate,
10... Monostable multivibrator, 11... Delay device, 12... Collision notification signal generator, ]3... Gate, 14
...Electric-optical converter, I5...Wavelength removal filter, λ
...14 output wavelengths. Patent applicant Nippon Telegraph and Telephone Public Corporation Patent application agent Megumi Yamamoto - Figure 1 Figure 2

Claims (3)

[Claims] (1) Consists of a passive optical star coupler that connects multiple input boats and multiple output boats with a light guide, and an optical signal collision detection/report circuit. One of the output ports of the optical star coupler is connected to the input terminal, and one of the input ports of the optical star coupler is connected to the output terminal of the optical signal collision detection/report circuit. Optical star coupler with detection. (2) A patent claim characterized in that the optical signal collision detection/report circuit stops the collision detection operation after detecting the optical signal collision, outputs the collision notification signal for a certain period of time, and then resumes the optical signal collision detection operation. The collision detection fl optical star coupler according to item 1. □ (3) A wavelength removal filter is inserted at the input of the circuit to prevent only the optical output signal of the optical signal collision detection/report circuit from entering the input terminal of the circuit. The optical star coupler with collision detection according to item 1.