JPS6028419B2 - Optical transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission system, and more specifically, to an optical transmission system that performs low-loss transmission using a single mode fiber.

Prior Art and Problems Conventionally, optical transmission fibers include single mode fibers and multimode fibers.

However, although single mode fiber has the advantage of having a wide frequency band due to its small group delay, it has drawbacks such as large transmission loss and difficulty in connecting with a light source. A narrow multimode fiber is used. OBJECTS OF THE INVENTION An object of the present invention is to provide an optical transmission system that can perform low-loss transmission using a single mode fiber.

Structure of the Invention The features of the present invention for achieving the above object are as follows:
A plurality of electro-optical conversion elements are driven by a digital electric signal containing transmission information, each optical output signal from the plurality of electro-optical conversion elements is transmitted in parallel through a single mode fiber, and each transmitted optical signal is The objective is to combine the signals into one signal by majority vote processing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The system of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an optical transmission system to which an optical transmission method as an embodiment of the present invention is applied, and this optical transmission system sends a digital electrical signal S, corresponding to the required information to be transmitted, to a transmitting side 1. It has a signal source 2 that generates a signal, and a plurality of electrical-to-optical converters 3, 4, 5 connected in parallel to the output of the signal source 2, and each electrical-to-optical converter generates an electrical signal S, correspondingly. are converted into the same optical signals Sa, Sb, and Sc, respectively.

Each electro-optical converter can be, for example, a laser diode, and the number of electro-optical converters is three in the illustrated example, but can be any number greater than or equal to two. . The same three optical signals Sa, S obtained in this way
b and Sc are optical transmission lines 6 each made of a single mode fiber.
, 7, 8 to the receiving side 9. optical transmission line 6,
7 and 8, for example, set the length of each single mode fiber so that the phases of the optical signals Sa, Sb, and Sc coincide when they reach the input end of the receiving side 9. They are made equal. The receiving side 9 is provided with a majority circuit 10 for synthesizing the optical signals Sa, Sb, and Sc that have reached the same phase and obtaining one signal corresponding to each signal. Majority circuit 1 converts the optical signals Sa, Sb, and Sc from each optical transmission line 6, 7, and 8 into electrical signals, and converts these electrical signals into an output signal S2 by a majority logic circuit composed of logic circuits. I'm starting to get it. FIG. 2 shows an example of the configuration of such a majority circuit 10, in which the lights Sa, Sb, and Sc from each of the optical transmission lines 6, 7, and 8 are converted into electrical signals by optical electrical converters ○/E, and compared. 111 and a comparator 112, respectively.

Assuming that each signal level is "1" above a predetermined level and "0" below a predetermined level, in this example, since the input signal is ternary, the signals S'a, S'b, and S'C are binary numbers. When the display is 011, 101, 110, 111, that is, when at least two input signals are "1", the comparator 111 generates an output "1".

Therefore, if the above binary number is x (IQ Hayabusa), the comparator 1
1 1 generates an output “1” when xZ3 and an output “0” when x<3. Comparator 112 input signal is “1”
, "0", "0", that is, x is compared with 4, and if x=4, an output "1" is generated, otherwise it is set as "0", and the output is passed through the inverter 113. It is input to the AND circuit 114. In this way, x≧3 or more “01r,”1
0, “10r,”110'', “111”
100'' is removed and obtained as output S2.

Therefore, by increasing the number of parallel transmission paths, the transmission error rate can be significantly reduced.

It should be noted that the majority decision circuit may also perform majority decision processing without converting each optical signal into an electrical signal by optical means such as condensing light with a lens. FIG. 3 shows an example of the majority circuit 10 having such a configuration.
Light Sa, Sb, and Sc from each transmission line 6, 7, and 8 are collected by, for example, a spherical lens 105, and the output thereof is converted by an optical-to-electrical converter O/E.

At that time, if the intensity of the light is above a certain predetermined level, it will be “1”.
If it is below a predetermined level, the opto-electrical converter should be set to output "0". It goes without saying that the predetermined level is determined by the sum of the light intensities input from at least two optical fibers. The output signal S2 is amplified by the amplifier 11, and a signal of a predetermined level can be obtained from the output terminal 12. If the transmission distance is long, the signal from the output terminal 12 may be converted into an optical signal again in the same manner and transmitted through a plurality of single mode fibers.

When optical transmission is performed using the transmission system shown in Figure 1, the same optical signal is transmitted through a large number of single mode fibers, and on the receiving side, these are combined by majority voting. Even if a large transmission loss occurs, deterioration of the S/N ratio can be prevented, the transmission distance can be significantly lengthened, and the reliability of the system can be dramatically improved.

Furthermore, when performing majority processing, each optical signal is transmitted through a single mode fiber, so pulse dispersion is small and a high quality composite signal can be obtained even when majority processing is performed.
Furthermore, since the same optical signal is sent in parallel, when a laser diode is replaced, the conversion work can be performed without stopping the same line function. Effects of the Invention According to the system of the present invention, as described above, low-loss optical transmission can be performed using a single mode fiber.

Furthermore, according to the method of the present invention, maintenance of the apparatus can be performed with great ease.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an optical transmission system to which the method of the present invention is applied, and FIGS. 2 and 3 are block diagrams showing examples of majority circuits in the optical transmission system of FIG. 1. It is a diagram. 1... Transmission side, 2... Signal source, 3, 4, 5
...Electro-optical converter, 6, 7, 8... Optical transmission line, 9... Receiving side, 10... Majority circuit, 1
1...Amplifier, S. ...digital electrical signal,
S2...Majority circuit output signal, Sa, Sb, S
c... Optical signal. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 Drive a plurality of electro-optical conversion elements with a digital electrical signal containing information to be transmitted, and transmit each optical output signal from the plurality of electro-optic conversion elements in parallel through a single mode fiber, so that the information is transmitted. An optical transmission system characterized by combining each optical signal into a single signal through majority voting processing.