JPS5975727A - Data transmission system - Google Patents

Abstract

PURPOSE:To multiplex a data signal and a transmission clock with simple constitution by composing a modulator of a pulse width modulation part which synchronizes with the transmission clock and a pulse insertion part which adds a pulse between modulated pulses at specific intervals of time, and a demodulator of a pulse removal part and a data clock regeneration part. CONSTITUTION:The pulse width modulation part 31a outputs modulated wide width pulses 61 and 62 synchronously with the transmission clock ST according to the level of the data signal SD, and the pulse insertion part 31b adds a pulse 63 having less width than the modulated pulses 61 and 62 between the modulated pulses at specific intervals of time a specific time after each modulated pulse rises. This insertion, however, is avoided in a specific insertion inhibition period before each modulated pulse rises. The pulse removal part 32a of the demodulator 32 removes the pulse 63 and the data clock regeneration part 32b regenerates the data signal RD and performs frequency division according to the number of the modulated pulses 61 or 62 following the signal RD to regenerate and output the clock RT.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission system, and more particularly to a data transmission system suitable for multiplex transmission of data signals and transmission clocks using optical fibers.

First, the prior art will be explained using FIG. 1 and FIG. 2. Fig. 1 is a configuration diagram of a conventional data transmission system of this type, in which 11 is a modulator that modulates the data signal SD, 12 is an optical transmitter that converts the modulated signal into electro-optic signals, 13 is an optical fiber, and 14 is a receiving device. Optical receiver that photoelectrically converts optical signals, 15
1 is a demodulator that demodulates a photoelectrically converted modulated signal; 16 is a synchronization circuit that outputs a received data signal RD; and 17 is a clock extraction circuit that outputs a received clock RT.

However, in this case, the data signal needs to be sent at a predetermined signal speed between the transmitter and the receiver, and
NRZ (Non R
When using a code formation such as (eturn to zero), it was necessary to devise a data format so that the same code does not continue for a long time. (If the same code continues for a long time, it becomes difficult to extract the clock.) On the other hand, in the case of synchronous optical data transmission, the transmission data signal is Several methods have been proposed for multiplexing and transmitting the clock and the transmission clock.

Among these methods, a method in which data signals and transmission clocks are sampled at high speed, serially encoded, and multiplexed is superior in that the signal speed of the data signal can be arbitrarily selected.

Figure 2 is a time chart for explaining the method of multiplexing the transmission data signal and the transmission clock in this method.
Figure 2(a) shows the waveform of the transmitted data signal 8D, and Figure 2(b) shows the waveform of the transmitted data signal 8D.
(c) shows the waveform of the transmission clock ST, respectively.
indicates serially multiplexed data. In FIG. 2, FS indicates a start bit, SD indicates sampling data of the data signal SD, ST indicates sampling data of the clock ST, and FP indicates a stop bit.

However, in this method, the multiplexed signal in the optical fiber ζ13 is about 10 to 3 times faster than the signal speed of the data signal SD.
It requires about 0 times the speed, and has the disadvantage that the circuit is considerably complicated.

However, there is still a method in which the transmitted data signal SD is simply subjected to a certain pulse width modulation in advance, and the rising edge or falling edge of the modulated pulse at this time is made to match the rising and falling edges of the data signal and the transmitting clock. However, this method has the disadvantage that when the signal speed becomes extremely slow, the DC state continues for a long time, making code errors more likely to occur.

The present invention has been made in view of the above, and an object of the present invention is to provide a data transmission system that can multiplex and transmit data signals and transmission clocks, and that has a simple configuration. .

A feature of the present invention is that a modulator that modulates a data signal and a transmission clock generates a modulation pulse with a narrow pulse width when the data signal is at the II O'' level in synchronization with the rising and falling edges of the transmission clock. When the level is "1", ・Modulation with a wide ξ pulse width ・Pulse width modulation on the pulse ・Pulse width modulation section and each of the above modulations ・Each modulation between the pulses ・Comparison with the ξ pulse width of the pulse After a predetermined period of time has elapsed from the rise of each modulation pulse, the pulse ξ with a narrow pulse width is
The demodulator, which consists of a pulse insertion section that adds pulses at predetermined intervals except during the insertion prohibited period before the rise of the pulse, demodulates the modulated signal after photoelectric conversion in the optical receiver, converts the modulated signal into each of the modulated signals.・Narrower ξ pulse width than the pulse ・Remove the pulse ・Regenerate the data signal from the pulse removal section and the output of this pulse removal section and continue this data signal by modulating the above pulse width with a narrow width ・Only a few dimensions of the pulse The present invention is comprised of a data/clock regenerating section that regenerates a transmission clock by dividing the frequency according to the number of modulation noises ξ having a wide noise width.

The embodiment of the present invention shown in FIG. 3 and FIGS. 4 to 6 are as follows.
This will be explained in detail using figures.

FIG. 3 is a block diagram showing an embodiment of the data transmission system of the present invention. In FIG. 3, 31 is the data signal SD
a modulator for manually modulating the and transmission clock ST; 12;
13 is an optical fiber; 14 is an optical receiver that converts the received optical signal into electricity; 32
is a demodulator that demodulates the photoelectrically converted modulated signal.
The evening signal RD and clock RT are output.

4 to 6 are time charts of different examples for explaining the modulation method in FIG. 3, and the signal speed becomes slower in the order of FIG. 4, FIG. 5, and FIG. 6. Figures 4 to 6
In the figure, (a) shows the waveform of the data signal SD, (b) shows the waveform of the transmission clock ST, and (C) shows the waveform of the modulation signal.

The modulator 31 in FIG. 3 is, as shown in FIGS. 4 to 6,
When the data signal SD is at the 0'' level in synchronization with the rising and falling edges of the transmission clock ST, the modulation pulse 61 has a narrow ξ pulse width, and when it is at the 1 level, the ξ pulse width is wide. The modulation pulse 62 modulates the ξ pulse width.The ξ pulse width modulator 31a and each modulating pulse 6
'l, between 62 (modulation) ξ cis between 61 and 61, 61 and 6
2, between 62 and 62, etc. ) modulated to ξcis6
A pulse 63 whose pulse width is narrower than the pulse width of 1 and 62 is added at a predetermined time interval after a predetermined time has elapsed from the rise (or fall) of each modulation pulse.
ξ cis insertion part 3 ], b. However, the ξ cis insertion unit 31b has the modulation noise ξ 61, 62
During the predetermined insertion prohibition period before the rising edge of , the .xi. pulse 63 is not added.

In addition, the demodulator 32 converts the optical signal received by the optical receiver 14 into a modulated signal obtained by optically converting the optical signal to each modulation/ξ system 61, 62.
The ξ cis removal unit 32a removes the ξ noise 63 having a narrower ξ noise width, and the data signal RD is reproduced and output from the output of the ξ cis removal unit 32a, and this data signal RD is subjected to subsequent modulation. The data/clock reproducing section 32b divides the frequency according to the number of .xi.systems 61 and reproduces and outputs the clock RT.

Therefore, the modulated signal shown in FIGS. 4 to 6 (c) is converted into an optical signal by the optical transmitter 12, transmitted through the optical fiber 13, and received by the optical receiver 14, and the optical signal is The signal is converted into an electric signal again to obtain a modulated signal, from which a data signal RD and a clock RT are regenerated by a modulator 32 and output.

As described above, according to the present invention, data signals and transmission clocks can be multiplexed and transmitted, and the configuration can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a conventional data transmission system, Fig. 2 is a time chart for explaining the conventional multiplexing method of data signals and transmission clocks, and Fig. 3 is an implementation of the data transmission system of the present invention. The configuration diagrams illustrating examples and FIGS. 4 to 6 are time charts of different examples for explaining the modulation method in FIG. 3, respectively. 12 - Optical transmitter, 13... Optical fiber, 14... Optical receiver, 3I... Modulator, 31a... Pulse width modulation unit, 311]... e-rus insertion unit, 32 - Demodulator, 32
a...e Lux removal unit, 321)...Data/clock recovery unit. 1F 1st day

Claims (1)

[Claims] 1. The data signal and the transmission clock are pulse-width modulated by a modulator, electrical-to-optical conversion is performed by an optical transmitter, and transmitted using an optical fiber. After photoelectric conversion by an optical receiver, demodulation is performed by a post-modulator. In the data transmission system, when the data signal is at ゛°0'' level in synchronization with rising and falling edges of the transmission clock, the modulator transmits
A ξ pulse width modulation unit that modulates the ξ pulse width to a modulation/ξ pulse with a narrow pulse width, and a ξ pulse width modulation unit that modulates the pulse width to a modulation pulse with a wide pulse width; After a predetermined period of time has elapsed from the rising edge of each modulation ξ, the pulse width is narrower than the ξ pulse width of the pulse.
The demodulator consists of a ξ pulse insertion section that adds pulses at predetermined time intervals except during the insertion prohibited period before the rise of the pulse;
a ξ rus removal unit that removes ξ rus having a narrow pulse width than each of the modulated pulses from the modulated signal from the optical receiver;
Reproducing a data signal from the output of the ξ pulse removal section, and dividing the data signal according to the number of subsequent modulated pulses with a narrow pulse width or the number of modulated pulses with a wide pulse width. What is claimed is: 1. A data transmission system comprising: a data clock regenerating section that regenerates a transmission clock using a data clock regenerating section.