JPH01198127A - Bidirectional data transmission system - Google Patents

Abstract

PURPOSE:To inexpensively realize bidirectional data transmission by using a constituting element having a simple characteristic by transmitting main signals and bidirectional sub-data after performing wavelength multiplexing by using the same wavelength. CONSTITUTION:After main signals (a) and sub-data (b) are electrically multiplexed by means of an optical transmitter 1, LD light is modulated and multiplexed by means of an optical multiplexer-demultiplexer 3. Then the LD light is sent to an optical-fiber transmission line 4. On the other hand, sub-data (c) are outputted by an optical transmitter 7 as LED light and sent to the opticalfiber transmission line 4 after the LED light is multiplexed by means of an optical multiplexer-demultiplexer 5. Since such constitution using light emitting elements of the same wavelength is used for transmitting main signals and bidirectional sub-data, this system can be realized easily and inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bidirectional data transmission system for transmitting a main signal and bidirectional sub-data via an optical fiber transmission line.

[Conventional technology]

Conventionally, in optical communication using optical fiber as a transmission path, main signals and bidirectional sub-data are transmitted using two different wavelengths.
This is done by wave multiplexing and three wave multiplexing.

FIG. 7 shows a configuration example of a two-way data transmission system using two-wave multiplexing. In the figure, a, a' are main signals, b, b'
, c, c' are sub data, 1', 7' are optical transmitters, 2°
, 6" is an optical receiver. 12.13 is an optical multiplexer/demultiplexer,
4 is an optical fiber transmission line. Main signal a and sub data b
After being electrically multiplexed in the optical transmitter 1', it is sent out as an optical signal with a wavelength λ, and sent out to the optical fiber transmission line 4 via the optical multiplexer/demultiplexer 12. After transmission, it is demultiplexed by the optical multiplexer/demultiplexer 13, converted into an electrical signal by the optical receiver 6', and separated into main signal a' and sub data b' and output. The data C is sent out as an optical signal of wavelength λ2 by the optical transmitter 7', and is sent to the optical multiplexer/demultiplexer 13.
The signal is sent out to the optical fiber transmission line 4 through the . After transmission, the signal is demultiplexed by the optical multiplexer/demultiplexer 12, converted into an electrical signal by the optical receiver 2', and output as sub-data C''.

FIG. 8 shows a configuration example of a bidirectional data transmission system using three-wave multiplexing. In the figure, I Ll 5+7'' is an optical transmitter, 16.17.2''' is an optical receiver, and 18° 19 is an optical multiplexer/demultiplexer. The main signal a, sub data b and c are sent to λ3 and λ4 respectively by optical transmitters 14.15.7”.
．． λ, is converted into an optical signal of
7.2'' is converted into an electrical signal and the main signal a 1. Sub data l, l.

It is output as C.

[Problem to be solved by the invention]

However, according to such conventional bidirectional data transmission systems, two-wave multiplexing or three-wave multiplexing using different wavelengths is performed to transmit the main signal and bidirectional sub-data, so the optical There was a problem that the characteristics of the transmitter and the optical multiplexer/demultiplexer were severe, and the price was also high.

゛ [Means for solving the problem] The present invention was made to solve the above problem, and it transmits the main signal and bidirectional sub-data by performing wavelength multiplexing using the same wavelength. It is something.

[Effect]

Therefore, according to the present invention, it is possible to transmit a main signal and bidirectional sub-data using light emitting elements having the same wavelength.

〔Example〕

Hereinafter, the bidirectional data transmission method according to the present invention will be explained in detail.

FIG. 1 shows an example of the configuration of an embodiment of this bidirectional data transmission system. In the figure, 1.7 is an optical transmitter, 2, 6
is an optical receiver, and 3 and 5 are optical multiplexer/demultiplexers. In this figure, the same reference numerals and symbols as those in FIG. 7 indicate the same or equivalent components, and the explanation thereof will be omitted.

FIG. 2 shows the L of the light emitting device (LD) constituting the optical transmitter 1.
DD output wavelength (spectrum)-intensity characteristics. FIG. 3 shows the LE of the light emitting element (LED) that constitutes the optical transmitter
D optical output wavelength (spectrum)-intensity characteristics.

In FIG. 1, main signal a and sub data b are sent to optical transmitter 1.
After electrical multiplexing, the LD light is modulated and output, multiplexed by an optical multiplexer/demultiplexer 3, and sent to an optical fiber transmission line 4. After transmission, it is demultiplexed by an optical multiplexer/demultiplexer 5 and converted into an electrical signal by an optical receiver 6.
The main signal a'' and sub data b'' are separated and output. Further, the sub data C is outputted as LED light by the optical transmitter 7, demultiplexed by the optical multiplexer/demultiplexer 5 and sent to the optical fiber transmission line 4, and then demultiplexed by the optical multiplexer/demultiplexer 3 to form an optical The receiver 2 converts it into an electrical signal and outputs it as sub data c1.

Here, the output lights of the optical transmitters 1 and 7 (characteristic A shown in FIG. 2 and characteristic B shown in FIG. 3) both have a center wavelength λ.

, characteristic A is a narrow spectrum, and characteristic B is a broad spectrum. In addition, as shown in FIG. 4, the relative intensity is a narrow spectrum of the LD light output cass vector of characteristic A.
Compared to characteristic B, its relative strength is very large. The LED light output dregs vector of characteristic B has a wide spectrum, but its relative intensity is very small compared to characteristic A. In FIG. 4, C indicates ports 1-4 of the optical multiplexer/demultiplexer 3 (the port from the optical transmitter l to the optical fiber transmission line 4) and ports 4-6 of the optical multiplexer/demultiplexer 5 (the port from the optical fiber transmission line 4). D is the wavelength-loss characteristic of the 4-2 port of the optical multiplexer/demultiplexer 3 (from the optical fiber transmission line 4 to the optical receiver 2).
wavelength-loss characteristics of the 7-4 boat of the optical multiplexer/demultiplexer 5 (the boat from the optical transmitter 7 to the optical fiber transmission line 4); The wavelength-intensity characteristics are shown in FIGS. 5 and 6. LED light for sub-data transmission is added to the input vector to the optical receiver 6 shown in FIG. 5, but since the difference in intensity is large, the influence on the transmission characteristics is small. In addition, the input vector to the optical receiver 2 shown in Fig. 6 is a spectrum with a missing center spectrum, but since the spectrum of the LED light has a large spread, the residual spectral component is also large, and the missing spectrum has no effect on the transmission characteristics. The impact is small. Note that since the bit rate of sub-data is usually much smaller than that of the main signal, transmission using LED light is possible.

As described above, according to the bidirectional data transmission system according to this embodiment, the main signal and bidirectional sub data are transmitted using light emitting elements (LD, LED) of the same wavelength, so it is easy to use. It becomes possible to configure an optical transmitter and an optical multiplexer/demultiplexer using characteristic components, and the present method can be realized easily and inexpensively.

〔Effect of the invention〕

As explained above, according to the bidirectional data transmission system according to the present invention, the main signal and bidirectional sub data are transmitted by performing wavelength multiplexing using the same wavelength, so that light emitting elements of the same wavelength are used. , it is possible to transmit the main signal and bidirectional sub-data, and this method has the excellent effect of being able to be realized at low cost using components with simple characteristics.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a bidirectional data transmission system according to the present invention, and FIG. 2 is an LD optical output wavelength-intensity characteristic of an LD that constitutes an optical transmitter in this bidirectional data transmission system. Figure 3 is an LED optical output wavelength-intensity characteristic diagram of the LED constituting the optical transmitter in this bidirectional data transmission system, and Figure 4 is a wavelength-relative intensity characteristic and optical multiplexing component of the LD and LED output light. Wavelength-loss characteristic diagram of wave generator,
Figures 5 and 6 are wavelength-intensity characteristics diagrams of input light to the optical receiver, Figure 7 is a configuration diagram of a conventional two-wave multiplexing bidirectional data transmission system, and Figure 8 is a conventional three-wave multiplexing diagram. FIG. 1.7... Optical transmitter, 2.6... Optical receiver, 3.5
... Optical multiplexer/demultiplexer, 4... Optical fiber transmission line, a,
a''...Main signal, b, b'', c, c'...Sub data.

Claims (1)

[Claims] A bidirectional data transmission system in which a main signal and bidirectional sub-data are transmitted via an optical fiber transmission line, characterized in that the main signal and bidirectional sub-data are transmitted by wavelength multiplexing using the same wavelength. Bidirectional data transmission method.