JPH04263521A - Repeater - Google Patents

Abstract

PURPOSE:To exactly identify and reproduce an input signal even when waveform deterioration is generated at a transmission line by comparing the output signal of a low-pass filter, which integrates the input signal, with the input signal as a threshold value by a comparator and generating an identification signal. CONSTITUTION:An LPF 2 composed of a CR circuit integrates an input signal (1) so as to apply the threshold value to a level converter 3 while following up the deterioration degree of the input signal (1). The input signal is transmitted to the differential amplification part of the next step after executing impedance conversion by a buffer part composed of a transistor 13 and a resistor 14 at the converter 3. Since the base potential of a transistor 20 is biased to the ECL intermediate level of -1.3V and turned to a reference voltage at the differential amplification part, a differential voltage between this reference voltage and the base voltage of a transistor 15 is outputted from the collector of the transistor 20. This differential voltage is applied as the base voltage of a transistor 24, and the identification signal in a form converted to the ECL level is outputted from the emitter of a transistor 24.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a repeater, and more particularly to a repeater having an automatic identification function such as an optical repeater.

[0002] In general, the pulse sent to the transmission line becomes a pulse that is attenuated by the transmission line and has noise added to it, so in order to be able to accurately distinguish it on the receiving side, an equalization amplification function and a timing recovery function are used. Although an identification and regeneration function is necessary, especially in optical transmission in recent years, it is desired to be able to eliminate the influence of wavelength dispersion of optical fibers as the distance between repeaters is increased, which is a demand for longer spans.

0003

2. Description of the Related Art FIG. 3 shows a well-known configuration example of a repeater as described above, which equalizes and amplifies an input signal that has been optical-to-electrically converted from an optical transmission line (not shown) or the like. Equalization amplifier section 4
, a timing reproducing section 5 that generates a reproduction timing signal on the reception side from this equalized and amplified pulse, and an identification and reproducing section 6 that identifies and reproduces the equalized and amplified signal using this reproduction timing signal, Furthermore, the identification reproduction section 6
A comparator 1 that compares the output signal of the equalization amplification section 4 with a certain threshold value Vth and converts it into a digital signal, and latches the output signal of this comparator 1 with the output signal from the timing regeneration section 5 to generate an identification reproduction signal. It is composed of a latch circuit 7.

0004

[Problem to be Solved by the Invention] The waveform of the input signal ■ to the comparator 1 in such a conventional repeater is shown in FIG.
As shown in Figure 2, the waveform deteriorates into a broadened shape due to the influence of wavelength dispersion in optical fibers due to longer spans, but at this time,
Since the comparison threshold Vth of the comparator 1 remains fixed, the waveform of the output signal (■) of the comparator 1 deteriorates as shown in the figure, and the pulse width becomes wider when the data is "1". In the case of 0'', the pulse width becomes narrow and the duty ratio changes. As a result, in the identification operation in the next-stage latch circuit, the illustrated "010"
There was a problem in that an error occurred in the input signal ``10011''.

Therefore, the present invention provides a repeater that uses a comparator to identify and reproduce an equalized and amplified input signal.
It is an object of the present invention to enable a comparison threshold value of a comparator to be changed in response to waveform deterioration of an input signal.

[0006]

[Means for Solving the Problem] FIG. 1 shows the principle of the configuration of a repeater according to the present invention. In order to generate a threshold value for a comparator 1, a low-pass filter 2 for integrating an input signal is provided. The identification signal is generated by comparing the output signal with the input signal using the threshold value.

[0007] Furthermore, in the present invention, the comparator 1
When configured with an L circuit, the output signal of the low-pass filter 2 is converted to an ECL level, and then the comparator 1
A level converter 3 may also be provided.

[0008]

[Operation] To explain the operation of the present invention with reference to FIG. 4, as mentioned above, due to the influence of wavelength dispersion of optical fibers, etc.
When the waveform of is degraded, when the input signal ■ is integrated by the low-pass filter 2, if the pulse width becomes wider or the level becomes higher, the output (center potential) of the filter 2 will also increase, and conversely, if the pulse width becomes narrower or the level becomes higher As Vth decreases, the output of the filter 2 also decreases, so the threshold value Vth follows and changes as shown by the dotted line in FIG. That is, the average level will also change according to the change in the duty ratio. Therefore, the output signal ■ of comparator 1 (see Figure 1) is as shown in the figure, when the input signal ■ is "01010011".
This means that it can be accurately identified as

In addition, when the filter 2 is used in this way, if the threshold value Vth becomes too large due to fluctuations in the input signal ■, if the comparator 1 is configured with an ECL circuit (when supporting high-speed operation) etc., the threshold value Vt
There is a possibility that h will not fall within the ECL identification level and will not be able to function as a threshold.

In such a case, in the present invention, the filter 2
It is preferable to add a level converter 3 after the comparator 1 and convert it to a level suitable for the ECL circuit before the comparator 1.

[0011]

[Embodiment] FIG. 2 shows an embodiment of the low-pass filter 2 and level converter 3 in the repeater according to the present invention shown in FIG. The level converter 3 is composed of a CR circuit consisting of a resistor 2 and a capacitor 3 between the resistor 2 and the capacitor 3.
A buffer section consisting of a transistor 13 and a resistor 14 is connected between the power supplies using the connection point between the transistor 13 and the capacitor 3 as an input terminal, and a buffer section consisting of a transistor 13 and a resistor 14 is connected between the power supplies using the connection point between the transistor 13 and the resistor 14 in this buffer section as an input terminal. A differential amplifying section consisting of transistors 15 and 20 and resistors 16 to 19, 21, and a transistor 2 of this differential amplifying section.
0 base with a constant bias voltage (-0.8V to -1.
-1.3V between ECL levels known as 8V)
a voltage divider section with resistors 22 and 23 connected in series between the power supplies to give a voltage, a transistor 26 and a resistor 27 to compensate for the same voltage level shift as the input buffer section, and the collector of the transistor 20 of the differential amplifier section. The buffer section includes a transistor 24 and a resistor 25, which are connected between power supplies to output an ECL level identification signal using a voltage as a base voltage.

Next, the operation of this embodiment will be explained.
In the low-pass filter 2, which consists of a circuit, the input signal ■
By performing an integral operation on the input signal (2), a threshold value Vth as shown by the dotted line in FIG.

In the level converter 3, impedance conversion is performed in a buffer section consisting of a transistor 13 and a resistor 14, and then the signal is sent to the next stage differential amplification section. In this differential amplification section, the base potential of the transistor 20 is biased to the ECL intermediate level of -1.3V as described above and serves as a reference voltage, so this reference voltage and the transistor 1
5 is output from the collector of the transistor 20, and this is given as the base voltage of the transistor 24, so that the emitter of the transistor 24 outputs an identification signal in the form of an ECL level. Become.

[0014]

[Effects of the Invention] As explained above, according to the repeater according to the present invention, the comparator generates the identification signal by comparing the output signal of the low-pass filter that integrates the input signal with the input signal using the threshold value. I configured it like this,
Even if waveform deterioration occurs in the transmission path, the discrimination level is always set to the optimum level, and accurate discrimination and reproduction is achieved.

Further, in the present invention, the comparator is ECL
When configured with a circuit, by further providing a level converter that converts the output signal of the low-pass filter to an ECL level and supplies it to the comparator, accurate identification and reproduction can be realized even when the input signal is high speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the principle of the configuration of a repeater according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a combination of a low-pass filter and a level converter used in a repeater according to the present invention.

FIG. 3 is a block diagram showing the overall configuration of a repeater according to a conventional example.

FIG. 4 is an operational waveform diagram in a conventional example and the present invention.

[Explanation of symbols]

1 Comparator 2 Low pass filter 3 Level converter In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] Claim 1: In a repeater that identifies and reproduces an equalized and amplified input signal using a comparator (1), the comparator (1) uses as a threshold the output signal of a low-pass filter (2) that integrates the input signal. A repeater characterized in that it generates an identification signal by comparing it with an input signal. 2. When the comparator (1) is configured with an ECL circuit, the output signal of the low-pass filter (2) is converted to an ECL level and the output signal of the comparator (1) is
2. The repeater according to claim 1, further comprising: a level converter (3) for providing a signal to the user.