JPS63298125A - Light receiver - Google Patents

Abstract

PURPOSE:To obtain accurate pulse width information even if an optical pulse level is fluctuated, in a receiver for the optical pulse having the information in the pulse width, by measuring a time interval between the differential output of the rise-up of the pulse and that of the fall-down of the pulse. CONSTITUTION:An optical pulse A is transduced into an electric signal A' in an optoelectronic transducer circuit 1. The signal A' is differentiated in a differentiating circuit 2. Differentiated waveforms B, which have the different polarities in rise-up and fall-down of the signal, are obtained. The waveforms B are amplified in an amplifier 3. Then, the rise-up differentiated waveform is made to be a pulse at a threshold value TH<+> in a pulse shaping circuit 4, and a signal C is obtained. The fall-down differentiated waveform is made to be a pulse at a threshold value TH<-> in a shaping circuit 5, and a signal D is obtained. A time E from the front edge of the signal C to the rear edge of the signal D is measured in a measuring circuit 7. A time F from the rear edge of the signal C to the front edge of the signal D is measured in a measuring circuit 7. An average G of the times E and F is operated in an operating circuit 8. The time G is hardly changed even if the level of the optical pulse is fluctuated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical receiver that detects an optical pulse width used in an optical pulse transmission system in which information is contained in the pulse width.

〔overview〕

The present invention uses an optical receiver that receives optical pulses with information in the pulse width to differentiate the received pulse and measure the time width between the rising differential output and the falling differential output, thereby changing the optical pulse level. Accurate pulse width information can be obtained even if the

[Conventional technology]

In optical transmission systems that use codes that contain information in the optical pulse width, it is necessary to accurately measure the optical pulse time width.

Especially 1. In a pulse waveform whose rise and fall times are finite, the pulse width differs depending on the measurement position of its amplitude. Generally, such pulse width is defined as the width at half the amplitude, and even if the amplitude changes, by always measuring the pulse width at the half of the amplitude, the correct pulse width, that is, the correct information can be obtained. be able to.

Even in optical pulse transmission, the arriving optical pulse has finite rise and fall times, so after converting the optical pulse into an electrical signal, it is necessary to always maintain a constant pulse amplitude in order to obtain correct pulse width information. In order to obtain such a constant amplitude, conventionally, automatic gain control or automatic discrimination level value control is performed to obtain a pulse of constant amplitude.

[Problem that the invention seeks to solve]

However, in optical receivers where optical power fluctuates quickly, optical signals with different optical powers arrive in a time-division manner, or optical signals arrive in bursts, the automatic gain control function or automatic discrimination level control function described above is required. Because of the delay in following the
There was a problem in that it was difficult to obtain the correct pulse width.

FIG. 3 is a diagram illustrating fluctuations in pulse width in conventional pulse width measurement.

A and A' in FIG. 3 show a light pulse input and a waveform obtained by converting this light pulse into an electric pulse. A shows the case where the optical power is large, and b shows the case where the optical power is small, and the amplitudes of the waveforms are different. TH is the threshold for pulse width measurement, and when the pulse is shaped using this threshold, the a waveform becomes Ha,
The b waveform becomes Hb, and its pulse width is 1. ．． 1. It will be different.

The present invention solves the above-mentioned problems, and provides an optical receiver that can obtain accurate pulse widths even for optical signals whose optical power fluctuates rapidly or optical pulses that arrive in bursts. With the goal.

[Means for solving problems]

The present invention provides an optical receiver that receives an optical pulse having information in its pulse width, which includes a differentiating circuit that differentiates an input pulse converted into an electrical signal, and an output of the differentiating circuit that determines each rise and fall of the input pulse. A pulse shaping circuit that generates pulses, the time (tl) from the start point of the pulse corresponding to the rising edge of the input pulse to the end point of the pulse corresponding to the falling edge of the input pulse, and the input from the end point of the pulse corresponding to the rising edge of the input pulse. The present invention is characterized in that it includes a circuit that measures the time (t2) from the falling edge of the pulse to the start point of the pulse, and an arithmetic circuit that averages these two times.

[Effect]

The pulse converted into an electrical signal is differentiated by a differentiating circuit and pulse-shaped.

The time t1 from the start point of the pulse corresponding to the rising edge of the pulse-shaped input pulse to the end point of the pulse corresponding to the falling edge of the input pulse, and the time t1 from the end point of the pulse corresponding to the rising edge of the input pulse to the rising edge of the input pulse. The time t2 until the end point of the pulse is measured, and the average of these two times t1 and t2 is calculated as the pulse width.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

The optical receiver of the present invention includes a differentiating circuit (2) that differentiates an input pulse converted into an electrical signal, and a pulse shaping circuit (4) that generates a pulse for each rising and falling edge of the input pulse from the output of this differentiating circuit. , 5), the time (1+) from the start point of the pulse corresponding to the rising edge of the input pulse to the end point of the pulse corresponding to the falling edge of the input pulse, and the time from the end point of the pulse corresponding to the rising edge of the input pulse to the falling edge of the input pulse. It is characterized by comprising a pulse interval measuring circuit (6, 7) that measures the time (t2) to the starting point of the pulse corresponding to , and an arithmetic circuit (8) that averages these two times.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a time chart showing waveforms at each point in FIG.

In FIG. 1, reference numeral 1 denotes a photoelectric conversion circuit, which converts an incoming optical pulse A into an electrical signal A'. 2 is a differentiating circuit for differentiating the electric signal A'. This differentiator circuit converts the electrical signal A'
It differentiates the electric signal A', and outputs a differential output B having different polarities at the rising and falling edges of the electrical signal A'.

This differential output B is amplified via an amplifier 3, then input to a pulse shaping circuit 4, and after being pulse shaped, is input to a pulse interval measuring circuit 6, 7, respectively.

The pulse interval measuring circuit 6.7 receives both the outputs C and D of the pulse shaping circuit 4.5, measures the time width of the differential waveform, and calculates the time width measurement values E and F of the pulse. Output to 8.

Next, the present invention will be explained in detail with reference to the time chart shown in FIG.

The arriving optical pulse A is converted into an electrical signal by the opto-electric conversion circuit 1, and the converted input pulse is input to the differentiating circuit 2. A differentiating circuit 2 differentiates the rising and falling edges of this pulse signal, and outputs differential waveforms B having different polarities. This differential waveform is generated by the pulse shaping circuit 4
．． 5, the pulse shaping circuit 4 converts the rising differential waveform with TH'' as the threshold, and the pulse shaping circuit 5 converts the falling differential waveform into pulses with TH- as the threshold, and shapes them into pulses C and D, respectively. These pulses C and D are each input to a pulse interval measuring circuit 6.7, and the pulse interval measuring circuit 6 measures the time interval t2 from the falling edge of pulse C to the rising edge of pulse D, and performs pulse interval measurement. The circuit 7 measures the time interval t from the rise of the pulse C to the fall of the pulse D.

A logic operation circuit 8 calculates a pulse width T=(tl+tz)/2 from the measured values E (tz) and F (t+), and outputs it as a pulse width signal G.

FIG. 4 is an explanatory diagram of the principle of pulse width measurement according to the present invention.

A and A' show the optical pulse input and the waveform obtained by converting it into an electric pulse. A indicates a case where the optical power is large, and b indicates a case where the optical power is small, and the amplitudes of the waveforms are different. B' indicates a differential waveform of the A' waveform, in which a is converted to a' and b is converted to b', which are similar waveforms in terms of waveforms. Differential waveform B'
The rising differential is pulse-shaped using TH'' as a threshold, and the falling differential is pulse-shaped using TH- as a threshold.

In the a' waveform, t+m is t in Figure 2, and tzb is the second
This corresponds to t2 in the figure. The rising differential waveform and the falling differential waveform are obtained as similar waveforms, and the threshold value T
H'' and TH- are set to have equal pulse widths in the rising and falling pulses after pulse shaping.

If a certain error range ±Δt is allowed for the pulse width T, the above-mentioned conditions can be relaxed, and the realization becomes easy.

In this way, even if the input level of the optical pulse changes, according to the present invention, correct pulse width information can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, accurate pulse width information can be obtained even if the input level of the arriving optical pulse changes rapidly or arrives in a burst form.

If the present invention is applied to an optical receiver using a high-speed optical transmission method, it is possible to obtain reception sensitivity with a low error rate even with respect to level fluctuations of input optical pulses.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a time chart of one embodiment of the present invention. Figure 3 is a time chart of the conventional example. FIG. 4 is a time chart explaining the present invention in detail. 1... Photoelectric conversion circuit, 2... Differential circuit, 3...
Amplifier, 4.5... Pulse shaping circuit, 6.7... Pulse interval measuring circuit, 8... Arithmetic circuit. −；・′ Iris 1 Tuko 3 Old

Claims (1)

[Claims] (1) In an optical receiver that receives optical pulses with information in the pulse width, a differentiating circuit (
2), and a pulse shaping circuit (4, 5) that generates a pulse for each rising and falling edge of the input pulse from the output of this differentiating circuit.
), the time (t_1) from the start point of the pulse corresponding to the rising edge of the input pulse to the end point of the pulse corresponding to the falling edge of the input pulse, and the time (t_1) from the end point of the pulse corresponding to the rising edge of the input pulse to the falling edge of the input pulse. circuits (6, 7) that measure the time (t_2) to the start point of the pulse
), and an arithmetic circuit (8) that averages these two times.