JP2562093B2 - Ternary signal transmission method using optical transmission pulse - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ternary signal transmission method (method) using an optical transmission pulse, and relates to prevention of a decrease in the maximum light reception level on the receiving side.

[0002]

2. Description of the Related Art A digital code from a start bit to a final bit is represented by a double-flow NRZ code (including Manchester code) having a minimum pulse width T _W , and a period before the start bit and a period after the last bit are both zero. Converting the leveled ternary digital signal into an optical pulse signal and transmitting it, and demodulating it into the original ternary digital signal on the receiving side,
A conventional example of a ternary signal transmission method (method) using optical transmission pulses will be described with reference to FIGS.

A ternary signal generator 13 outputs a ternary signal as a bipolar Manchester code (MIL-STD-155).
3) (specified in Section 3) and is supplied to the modulator 14 and the zero level display pulse generator 15, respectively. The period before the double-current (bipolar) Manchester code, that is, the non-transmission period is set to the zero level. As shown in FIG. 4B, the double-current Manchester code is composed of a 3-bit length start signal which changes in the order of + V and −V (1.5-bit length each), a data consisting of a subsequent double-flow NRZ code, and a final bit. Is a signal to which a parity bit is added. After the final bit, the level is returned to zero again.

In Manchester code, the logical "1" is-
It is represented by a code that changes in the order of V, + V (each 1/2 bit length), and the logic "0" is represented by a code that changes in the order of + V, -V (each 1/2 bit length). . The rising and falling timing of each rectangular wave signal is a cycle T of 1/2 bit length.
It is synchronized with the clock pulse with _W (FIG. 4A). The modulator 14 generates a signal C (FIG. 4C) in which a clock pulse is gated by a positive rectangular wave of the input signal, and the signal C is input to the transmitter T. This pulse signal C is synchronized with the clock pulse and has a minimum pulse interval of three corresponding to the start pulse P _s and one or two corresponding to a positive rectangular wave of length T _W or 2T _W. T _W pulse (with its pulse width t
_{If w} , then _tw < _TW ).

[0005] In the zero-level display pulse generator 15, (and however delta <T _W) the last bit (parity bit) standing amounts pulse P ₁ and rise from the delta time of the P ₁ after
A pulse P _{2 which} rises later (the pulse width of P ₁ and P ₂ is _tw )
A zero level display pulse (Fig. 4D) consisting of
Input to the transmitter T. In the transmitter T, the input pulse signal (C) and the following zero level display pulse P ₁ ,
P _{2 and} P ₂ are converted into an optical pulse signal (E) (FIG. 4E) and sent to the optical fiber cable 16.

The optical power transmitted through the optical fiber cable 16 is
The loose signal is photoelectrically converted by the receiver R to generate a pulse signal
(F) (FIG. 4F) is a demodulator 17 and a zero level detector 18.
And supplied to. At the demodulator 17, the input signal (F) rises.
Both the rising and falling delay times are τ (τ is T_W-T_wTo
Equal or slightly larger) through a delay circuit of double current N
The RZ signal (G) is demodulated and supplied to the ternary signal reproduction circuit 19.
Be paid. This signal (G) is the first three
The pulse width is approximately 3T due to the connected pulse._WOne of
Start pulse P_sRestored to. Moreover, the pulse interval
2T_WA positive pulse of more than that has a pulse width of almost T
_WIs converted to a positive pulse equal to. Moreover, the pulse interval
T_WTwo consecutive pulses of are connected and the pulse width is
Gaho 2T_WIs demodulated into one positive pulse. Parite
Pulse P corresponding to bit₀'And the following pulse P
₁′, P₂The three pulses with 'are joined to form a pulse
Width is about 2T _WOne positive pulse P of + Δ_EDemodulated to
You.

The zero level detector 18 positively rises at the leading edge of the start pulse of the input signal (F) at a low level during reception standby, and two zero level display pulses P ₁ ′ and P ₂ ′ after the final bit. Is detected, a zero level detection signal (H) falling to zero level is generated and supplied to the ternary signal reproduction circuit 19. This signal (H) is at L (low) level (H level otherwise) corresponding to the zero level period of the original ternary signal.
This is the signal.

In the ternary signal reproduction circuit 19, the signal (G) is gated by the zero level detection signal (H), and the level after the last bit is set to zero level until the start pulse P _s rises. . At the same time, the pulse width of the final bit is shaped into T _W. The ternary signal (FIG. 4I) restored by this is input to the ternary signal receiver 20. If _two zero level display pulses P ₁ ′ and P ₂ ′ are not detected, an error signal is generated and the data received up to that point is invalidated.

[0009]

Waveform distortion occurs in the pulse (F) photoelectrically converted by the receiver R with respect to the optical pulse signal (E) sent from the transmitter T. Generally, as the level of the optical pulse input to the receiver R increases, the receiver R
The output pulse (F) has a wide width. Therefore, the upper limit value of the dynamic range of the input light pulse is one when the zero level display pulses P ₁ ′ and P ₂ ′ (the pulse interval of which is the smallest in the input pulse train) are connected by increasing the light receiving level. The pulse level is reached.

In the prior art, the zero level display pulse P
_Since the interval Δ between ₁ and P ₂ is set to be smaller than the minimum interval T _W of the other pulses, there is a drawback that the maximum light receiving level on the receiving side is reduced accordingly. An object of the present invention is to prevent a decrease in the maximum light receiving level, which is a conventional drawback.

[0011]

[Means for solving the problem] From start bit to final
Digital code up to bit is minimum pulse width T_WDouble current
Represented by the NRZ code, the period before the start bit and the
And the period after the last bit is set to zero level.
The optical signal is converted into an optical pulse signal (its pulse width t _w<T_W
And the minimum pulse interval is T_WEqual to)
It is converted and transmitted, and on the receiving side, the original three-level
Ternary signal transmission using optical transmission pulse demodulated to digital signal
In the present invention, the transmission side optical pulse signal is transmitted.
Following the last bit of the
Is the minimum pulse interval T_WOnly that minimum pulse
Interval T_WZero level display signal for light pulse of larger width
The width of the optical pulse received at the receiving side is zero than that
After detecting the level indication signal,
Set the level to zero level.

[0012]

Embodiments of the present invention will be described with reference to FIGS. In this figure, parts corresponding to those in FIGS. 3 and 4 are denoted by the same reference numerals, and redundant description will be omitted. Transmit optical pulse signal (E)
In view of the fact that the maximum light receiving level is determined by the minimum pulse interval T _W of the above, in the present invention, the minimum pulse interval T _W (for example, 500 ns) of the general data signal on the transmission side is used.
Zero level display with a narrower pulse interval Δ. Instead of the pulses P ₁ and P _2, a zero level display with a pulse width T _Z (for example 600 ns) rising at the trailing edge of the last bit and slightly larger than the minimum pulse interval T _W. The pulse P _Z is output from the zero level display pulse generator 15 (FIG. 2D). At the output of the transmitter T, the rising edge of the pulse P _Z is separated from the rising edge of the immediately preceding optical pulse by at least the minimum pulse interval T _W.

[0013] In the zero-level display pulse P _Z 'demodulator 17 at the receiving side, or as in the related art rise and delay times of the falling τ is equal to T _W -t _w, passing it from the slightly larger delay circuit The pulse P of the last bit immediately before
_It is connected to ₀ ′ to form one pulse P _0Z (FIG. 2).
G). The output signal (G) of the demodulator 17 is input to the start bit detection circuit 21 of the zero level detector 18, a pulse (H) (FIG. 2H) is generated at the rising of the start pulse P _S , and the multivibrator circuit (F / F / F) is given to the set terminal S of 22.

On the other hand, in the output (F) of the receiver R, in the zero level display signal detector 23 of the zero level detector 18, is the width of each pulse larger than the minimum pulse interval T _{W of the} transmitted light pulse (E)? Whether the pulse width is larger than T _W is determined to be a zero level display pulse, and the detection pulse (I) is immediately applied to the reset terminal R of the F / F 22. Output of F / F22 is pulse (H)
Rise at the leading edge of (start pulse P _S ) and pulse (I)
The signal (J) falls at the leading edge of (Fig. 2J). Since the L (low) level period of the signal (J) corresponds to the zero level period of the original ternary signal, it is also called a zero level detection signal. Three
In the value signal reproducing circuit 19, the demodulator output (G) is gated by the zero level detection signal (J), and the period until the rising of the start pulse P _{S and} the trailing edge of the final bit pulse are generated as in the conventional case. In the subsequent period, both are set to zero level, the ternary signal (K) is reproduced, and the ternary signal receiver 20
Given to. Since the final bit pulse P _Z ″ becomes longer than the minimum pulse interval T _W , the pulse width is the same as in the conventional case shown in FIG.
It can also be output after being shaped into T _W as shown in L.

[0015] Incidentally, after a delay circuit only with a delay time τ in the signal rising in place of the delay circuit of τ both the delay time of the signal rising and falling incorporated in the demodulator 17 (≒ T _W -t _w) Alternatively, a circuit in which a retriggerable monostable multivibrator circuit that outputs a rectangular wave having a time width τ is connected may be used. In the above description, the case where the double-flow NRZ code is the bipolar Manchester code (MIL-STD-1553) has been described, but this is an example and the present invention is not limited thereto.

[0016]

According to the prior art, the final bit of the transmitted light pulse is
As a zero level display pulse added immediately after the
The pulse interval Δ is the minimum pulse interval T of the general data signal._WThan
Even narrower pulse P₁, P₂Was used, while
In the invention, the pulse width is T_WOne larger pulse
P_ZFrom the immediately preceding optical pulse by at least the minimum pulse interval T
_WSince they are used separately, the transmitted optical pulse signal
Has a minimum pulse interval of T_WIs larger than the conventional Δ
You. Therefore, the maximum light reception level on the receiving side is prevented from decreasing.
Is done.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart of FIG.

FIG. 3 is a block diagram of a ternary signal transmitting / receiving apparatus using a conventional optical pulse.

FIG. 4 is a timing chart of FIG.

Claims (1)

(57) [Claims] 1. A three-valued digital code from a start bit to a final bit is represented by a double-current NRZ code having a minimum pulse width T _W , and a period before the start bit and a period after the final bit are both at a zero level. The digital signal is converted into an optical pulse signal (its pulse width t _w <T _W and the minimum pulse interval is equal to T _W ) and transmitted, and the receiving side receives the original three-value digital signal from the received optical signal. In the ternary signal transmission method using the optical transmission pulse for demodulation, the minimum pulse interval T _{W is} separated from the immediately preceding optical pulse by at least the minimum pulse interval T _W following the last bit of the transmission-side optical pulse signal. optical pulses _W larger width transmitted as a zero-level display signal, by detecting the zero level display signal than the width of the received light pulse on the receiving side, after the last bit of the demodulated signal Characterized in that to return the level to zero level, ternary signal transmission using optical transmission pulse.