JPS59216335A - Optical transmission system - Google Patents

Abstract

PURPOSE:To make it possible to use light sources having the same wavelength and the same photodetectors by making frequencies of light emitting element driving subcarriers different from one another in an optical transmission system. CONSTITUTION:In case of the transmission from a terminal 1 to a terminal 1', the subcarrier from a subcarrier generator 8 is modulated to drive a light emitting element 3, and an optical signal is made incident to an optical fiber 5 through an optical coupler 6. The optical signal from the optical fiber 5 is branched in an optical coupler 7, and the electric signal from a photodetector 4' is allowed to pass through a band-pass filter, and a modulated subcarrier is outputted to the terminal 1'. In case of the transmission from a terminal 2 to a terminal 2', a light emitting element 3' is driven directly by the base band signal from the terminal 2, and an optical signal is made incident to the optical fiber 5. The output from a photodetector 4 is outputted from the terminal 2' through a low-pass filter 10. Since spectrums of modulation signals are different from each other, light sources having the same wavelength and the same photodetectors can be used.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a multiplexing system in optical transmission using optical fibers. (b) R-end technology and problems Using a single optical fiber, Wavelength multiplexing optical transmission, which uses a plurality of different wavelengths to perform transmission in the same direction or in both directions, has been practiced for some time. This method aims to achieve economical efficiency by transmitting a large amount of information using a single optical fiber, and is particularly suitable for transmitting broadband information such as a large number of image signals. It has the excellent characteristics of not only low loss and wide band, but also that it is not affected by electromagnetic conduction. By actively utilizing these features, it can be used in harsh environments such as factories, for example. It is considered to be used as a stable means of information transmission. In such applications, it is not always necessary to transmit high-speed and broadband signals, but rather low-speed signal transmission is often performed, and low cost is an important point. Wavelength multiplexing transmission as described above is not necessarily suitable because it uses an optical demultiplexer/multiplexer, multiple types of light emitting elements, and light receiving elements.

(c) Purpose of the Invention The purpose of the present invention is to overcome the above-mentioned drawbacks and provide a low-cost multiplex transmission method. (d) Structure of the Invention In an optical transmission method using optical fibers. , consists of a single optical fiber, a number of optical transmitters each using a light emitting element with the same emission wavelength as a light source, and an equal number of optical receivers, and each optical transmitter inputs the optical output of the light emitting element to the optical fiber. and a means for inputting the light from the optical fiber to the light receiving element of each optical receiving device, making the light emission of the light emitting element equal in each optical device, and providing a subcarrier for driving the light emitting element. This is achieved using an optical transmission system characterized by having different frequencies.

(e) Embodiment of the invention FIG. 1 shows an embodiment of the present invention.
FIG. 3 is a diagram showing the principle of the optical coupler used in the system configuration shown in the figure, and FIG. 3 is a diagram showing the spectral arrangement in the electrical domain of the variable-view signal used in the system configuration shown in FIG.

In the figure, 1.1', 2. '2' is a terminal, 3.3' is a light emitting element, 4.4 is a light receiving element, 5 is an optical fiber, 6.7 is an optical coupler, 8 is a subcarrier generator, 9 is a modulator, 10 is a low pass filter, 11 is a bandpass filter 0 To explain the operation below, the channel from terminal 1 to terminal 1 (hereinafter referred to as CH1) uses subcarrier 17 as shown in Figure 3. The baseband signal modulates the subcarrier from the subcarrier generator 8 to drive the light emitting element 3. The optical signal from the light emitting element enters the optical fiber 5 via the optical coupler 6. The optical coupler 7 branches the optical signal from the optical fiber 5 and inputs it to the light-receiving element 4.The electrical signal from the light-receiving element 4' is converted into a P wave by the band-pass filter 11 and outputs a modulated subcarrier to the terminal l. do.

On the other hand, the channel from terminal 2 to terminal 2 (hereinafter referred to as CH2) uses a baseband signal as shown in Figure 3.
In the optical coupler 6, the light emitting element 3' is directly driven by the baseband signal from the baseband spectrum 16), that is, from the terminal 2, and the generated optical signal is input to the optical fiber 5 via the optical coupler 7. The optical signal from the optical fiber 5 is branched and input to the light receiving element 4. The output from the light receiving element 4 is outputted to the terminal 2 via the low pass filter 10. An example of the configuration of the optical coupler is shown in FIG.

In the figure, 61.71 is a half mirror 162, 63, 64°7
2.73.74 are lenses.

The light emitted from the light emitting element 3 is converted into a parallel beam by the lens 62, passes through the half mirror 61, and then passes through the lens 6.
4 and enters the optical fiber 5.

The light propagating through the -1 optical fiber 5 is converted into a parallel beam by the lens 64, reflected by the Hara mirror 61, and received by the light receiving element 4 through the lens 63.

At this time, a part of the light emitted from the optical fiber 5 passes through the half mirror 61 and enters the light emitting element 3. For example, if a light emitting diode is used as the light emitting element 3, there will be no negative effect. 1. After passing through the lens 64, the light emitted from the light emitting element 3 is reflected at the end face of the optical fiber, passes through the half mirror 61 and the lens 63, and is received by the light receiving element 4, which can become an interfering sound wave that interferes with the original signal ch2. Although the same wavelength is used in , the spectra of the transformed signals in chi and ch2 are arranged as shown in Figure 3 in the electrical domain, and
Even in 0chi, where the signal of chi can be easily removed by the low-pass filter 10 shown in the figure, the influence of ch2 can be easily removed by the band-pass filter 11 shown in FIG.

Although baseband transmission is performed on one side as an example, it is also possible to use subcarriers with different frequencies.

(f) Effects of the Invention As described above, the method of the present invention can use light sources of the same wavelength and the same light receiving element, and does not require expensive optical demultiplexers or demultiplexers for wavelength multiplexing. The system can be configured at low cost and has high industrial value.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a system configuration showing an embodiment of the present invention, Fig. 2 is an example of the configuration of an optical coupler, and Fig. 3 is a spectrum in the 'I region air region of Mugi Chocho No. in Fig. 1. It is a figure showing arrangement. Figure A 3.3 is a light emitting element, 4.4' is a light receiving element, 5 is an optical fiber, 6.7 is an optical coupler, 1o is a low pass filter, and 11 is a band pass filter.

Claims (1)

[Claims] An optical transmission system using optical fibers consists of a single optical fiber, multiple optical transmitters whose light sources are light emitting elements with the same emission wavelength, and the same number of optical receivers. It has means for inputting the output to the optical fiber, and means for inputting the light from the optical fiber to the light receiving element of each optical receiving device, so that the light emission length of the light emitting element is equalized in each optical device, and the light emitted from the optical fiber is made equal in each optical device. An optical transmission method characterized by using different subcarrier frequencies for driving light emitting elements.