JPS6041495B2 - Optical fiber transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission system in which a central device collects on/off signals of at least two switches in one or more terminals.

Collecting the on and off signals of a large number of switches into a central device is useful for example in steel production. It is needed as a collection of control signals in process control systems. Conventionally, this type of transmission system uses a transmission system that transmits electrical signals.

However, in factories where this type of transmission system is used, there is generally an extremely large amount of electrical noise. Therefore, expensive shielding measures are taken for the transmission system, and the electrical signal
A high voltage signal of about 0V is used. As a result, it is poorly compatible with electronic computers typically located in central equipment.

It is also extremely difficult to simplify the wiring harness by connecting this transmission system in a star or tee configuration. In order to eliminate these drawbacks, this invention introduces an optical fiber transmission system and uses reflected light within the optical fiber as a switch on/off signal.
The terminal switch is completely protected from any air noise, and the transmission system as a whole is extremely resistant to electrical noise.In addition, each switch and the central device can be easily connected in a tee or star configuration to simplify wires and harnesses. The central device can be simplified.

FIG. 1 shows an embodiment of the present invention, in which M is a central device, T is an optical transmitter, R is an optical receiver, SWI to SW3 are terminal switches, 1 to 4 are optical branch circuits, and 5 to 11 is an optical fiber.

An optical transmitter T of the central device M is transmitting light pulses to an optical fiber.

On the other hand, the optical receiver R receives the reflected light in the optical fiber 5 taken out by the optical branching circuit 1. The optical pulse sent out from the optical transmitter T is transmitted through an optical fiber 5 and an optical branch circuit 2.
, and reaches the SWI via the optical fiber 6. SWI is now OF
Assume that the switch changes from F to ON, and therefore the reflection at SW1 changes from almost zero to almost 100%. In this case, SWI is ON
The reflected light newly generated by the SWI passes through the optical fiber 6, the optical branch circuit 2, the optical fiber 5, and the optical branch circuit 1 again to reach the optical receiver. The optical receiver calculates the length of the optical fibers 5 and 6 based on the arrival time difference between the optical pulse sent from the optical transmitter and this received pulse, and converts this reflected pulse into SWI.
It is determined that this is a signal of For this purpose, the correspondence between the light propagation length and each switch must be established in advance. Similarly, it is possible to collect ON/OFF signals of each switch depending on the presence or absence of reflected pulses from SW2, SW3, . . . It goes without saying that the fibers interposed between the central device and each switch need to be constructed such that their lengths, for example, are varied so that each switch can be distinguished. FIG. 2 shows an example of the configuration of a terminal switch that can be used in an optical fiber transmission system according to the present invention.

6 is an optical fiber, 12 is a mirror, and 13 is a handle for cutting the switch.

A solid line indicates when the switch is on, and a broken line indicates when it is off. When the switch is turned on, almost 100% of the light propagated through the optical fiber 6 is reflected by the mirror 12. When the switch is off, there is no mirror 12, so the reflection of light is almost zero. As described above, according to the present invention, an optical fiber can be used as a transmission line, and a switch that is hardly affected by electrical noise as shown in FIG. 2 can be used as a terminal switch, and the system as a whole can be extremely resistant to electrical noise. Can be configured.

In addition, since each switch can be distinguished by the difference in the propagation time of the reflected light from each switch, it is possible to connect the so-called data buzz type as shown in Fig. 1, which greatly simplifies the wiring harness. This has the advantage that the central device can also be simplified. FIG. 3 shows another embodiment of the invention.

In place of the optical branching circuits 2 to 4 in FIG. 1 of the previously described embodiment, a star optical branching circuit 14 is used as shown in FIG. It is assumed that this branch circuit 14 has a function of branching the light propagating through the optical fiber 5 to the optical fibers 6 to 9. This embodiment is similar to the embodiment described with reference to FIG. 1, in that the on/off information of the terminal switch is received by the receiver R of the central device as the presence or absence of reflected pulses, except that the connection of the optical fibers is slightly different from that in FIG. However, it is effective when connecting so many switches that the loss of the optical branch circuit cannot be ignored. As described above, in the optical fiber transmission system according to the present invention, it is possible to realize a transmission system that is extremely resistant to electrical noise because it can be configured without intervening electrical signals at all except for the central device, and it is possible to realize a transmission system that is extremely resistant to electrical noise. Therefore, it is possible to easily connect wires in a tee shape or a star shape, which has the advantage of simplifying the wire connections and simplifying the central device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of this invention, FIG. 2 is a diagram showing an example of the configuration of a terminal switch that can be used in this invention, and FIG. 3 is a diagram showing another embodiment. . In the figure, 1 to 4 are optical branch circuits, 5 to 11 are optical fibers, 1
Reference numeral 4 indicates a star light distribution circuit, M is a central device, T is an optical transmitter, R is an optical receiver, and SWI to SW3 are terminal switches. In the drawings, the same or corresponding parts are denoted by the same reference numerals. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a transmission system where a central device collects the on/off signals of at least two or more switches in one or more terminals, the central device and each switch of the terminals are connected by optical fiber, and The terminal includes at least an optical transmitter that sends light to each switch through an optical fiber, and an optical receiver that detects the amount of reflection from each switch and the position where the reflected light is occurring. An optical fiber transmission system comprising an optical circuit that reflects light transmitted through an optical fiber to the same optical fiber with varying amounts of reflection depending on whether the optical fiber is turned off.