JP2503572Y2 - Optical input disconnection alarm circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an optical receiver circuit, and more particularly to an alarm circuit for detecting a light input break.

[Prior Art] An example of a conventional alarm circuit will be described with reference to FIG.

As shown in FIG. 5, the conventional alarm circuit has an input signal
Limiter amplifier 21 for amplifying S _i and this limiter amplifier 21
Peak rectifier circuit 22 for rectifying an output signal S _o of the comparator 24 for comparing the Rifuarensu voltage V _R of the DC voltage V _P and Rifuarensu circuit 23 from Rifuarensu circuit 23 and the peak rectifier circuit 22 for generating a Rifuarensu voltage V _R And a buffer amplifier 25.

Then, the output signal amplified by the limiter amplifier 21
S _o is peak rectified by the peak rectifier circuit 22 and output as a DC voltage V _P.

The DC voltage V _P is compared with the reference voltage V _R from the reference circuit 23 by the comparator 24, and if the voltage is below a certain specified level, the output voltage of the comparator 24 is the buffer amplifier 25.
Is output as an alarm signal.

FIG. 6 is a block diagram showing an example of an optical receiver to which a conventional alarm circuit is applied.

In FIG. 6, the same reference numerals as those in FIG. 5 designate corresponding parts, 26 is a light receiving element, 27 is a preamplifier, 28 is an equalizing amplifier which receives the output of this preamplifier 27, and 29 is this A direct current regeneration circuit having the output of the equalizing amplifier 28 as an input, a discrimination circuit 30 having the output of the direct current regeneration circuit 29 as an input, a timing extraction circuit 31 and a limiter amplifier 32.

The alarm circuit shown in FIG. 6 amplifies the output signal of the timing extraction circuit 31 of the optical receiver which converts light into an electric signal,
It is configured to rectify and compare the obtained DC voltage V _P and the reference voltage V _R by the comparator 24 to detect the optical input interruption.

The input signal S _i to the limiter amplifier 21 is the output signal from the timing extraction circuit 31, and the amplitude becomes substantially zero (zero) when the light input is interrupted, so the alarm circuit operates and the alarm signal is issued.

[Problems to be solved by the device]

In the above-mentioned conventional alarm circuit, when the mark ratio of the transmission signal is extremely low (high), the timing extraction circuit 31
Becomes smaller and the output signal S _o of the limiter amplifier 21 also becomes smaller in amplitude. Therefore, the comparator 24 operates, an output voltage appears, and an alarm signal is output not only when the light input is interrupted but also when the mark ratio changes.

[Means for solving the problem]

The optical input disconnection alarm circuit of the present invention amplifies and rectifies the output signal of the timing extraction circuit of the optical receiver that converts light into an electric signal, and compares the obtained DC voltage with the reference voltage by the comparator. In the alarm circuit that detects light input interruption,
A mark ratio detection circuit whose DC output voltage changes according to the mark ratio change of the transmission signal input to the timing extraction circuit is provided, and the DC voltage from this mark ratio detection circuit is applied as a reference voltage to the comparator. It is the one.

[Action]

In the present invention, a mark rate detection circuit is provided to change the issuing point of the alarm signal according to the mark rate of the transmission signal.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an alarm circuit in the light input break alarm circuit of the present invention.

In the figure, 1 is a limiter amplifier for amplifying the input signal S _i , 2 is a peak rectifier circuit for peak rectifying the output signal S _o from the limiter amplifier 1 and outputting it as a DC voltage V _P , 3
Is a mark ratio detection circuit in which the DC output voltage changes according to the change of the mark ratio of the input transmission signal, 4 is a reference circuit to which the DC voltage V _m from this mark ratio detection circuit 3 is input, and 5 is a peak rectification circuit. A comparator for comparing the DC voltage V _P from 2 with the reference voltage V _R from the reference circuit 4, and 6 is a buffer amplifier having the output of the comparator 5 as an input.

The DC voltage from the mark ratio detection circuit 3 is applied to the comparator 5 as a reference voltage.

FIG. 2 is a block diagram showing a configuration example of an optical receiver to which the alarm circuit in the optical input disconnection alarm circuit of the present invention is applied.

In FIG. 2, the same reference numerals as those in FIG. 1 indicate corresponding parts, 7 is a light receiving element, 8 is a preamplifier, 9 is an equalizing amplifier which receives the output of the preamplifier 8, and 10 is a direct current. A reproducing circuit, 11 is an identification circuit having the output of the DC reproducing circuit 10 as an input, 12 is a timing extracting circuit having the output of the equalizing amplifier 9 as an input, and 13 is a limiter amplifier having the output of the timing extracting circuit 12 as an input. Is.

Further, the mark ratio detection circuit 3 for rectifying the equalized waveform signal S _r of the equalization amplifier 9 and outputting the DC voltage V _m to the reference circuit 4 of the alarm circuit is provided.

FIG. 3 shows the output characteristics of the mark ratio detection circuit 3,
The figure shows the output characteristics of the timing extraction circuit 12.

Next, the operation of the optical receiver shown in FIG. 2 will be described with reference to FIGS. 3 and 4.

First, when the mark ratio of the transmission signal is 1/2, the output amplitude of the timing extraction circuit 12 becomes maximum as is clear from FIG. 4, and similarly, the DC voltage (output DC voltage) V of the mark ratio detection circuit 3 is also increased. _m also becomes the maximum as shown in FIG. In response to this, the reference voltage V _R of the reference circuit 4 becomes high and the alarm signal emission level also becomes high.

Next, when the mark rate of the transmission signal becomes low (high),
The output amplitude of the timing extraction circuit 12 becomes small (see FIG. 4), and an alarm signal is issued in this state. However, at the same time, the DC voltage (output DC voltage) V _{m of the} arc rate detection circuit 3 also becomes small (see FIG. 3), so the reference voltage V _R becomes low and the alarm signal emission level becomes low.

As a result, even if the mark rate becomes low (high) and the output amplitude of the timing extraction circuit 12 becomes small, the level at which the alarm signal is emitted also becomes low accordingly, so that the alarm circuit does not malfunction.

[Effect of device]

As described above, according to the present invention, the mark rate detection circuit is provided to change the issuing point of the alarm signal according to the mark rate of the transmission signal, so that the mark rate becomes low (high) and the output of the timing extraction circuit. Even if the amplitude becomes small, the alarm circuit does not malfunction and the alarm signal is not issued.

Then, there is an effect that it is possible to prevent the alarm signal from being output due to the change of the mark ratio of the transmission signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an alarm circuit in an optical input disconnection alarm circuit of the present invention, and FIG. 2 is a block diagram showing an example of the configuration of an optical receiver to which the alarm circuit of FIG. 1 is applied. FIG. 4 is a diagram showing the output characteristic of the mark ratio detection circuit, FIG. 4 is a diagram showing the output characteristic of the timing extraction circuit, FIG. 5 is a block diagram showing an example of a conventional alarm circuit, and FIG. 6 is a conventional alarm circuit. FIG. 11 is a block diagram showing a configuration example of an optical receiver to which is applied. 1 ... Limiter amplifier, 2 ... Peak rectifier circuit, 3 ...
Mark ratio detection circuit, 4 ... Reference circuit, 5 ... Comparator, 6 ... Buffer amplifier, 7 ... Light receiving element, 8 ...
Preamplifier, 9 ... Equalizing amplifier, 10 ... DC regeneration circuit,
11 …… Identification circuit, 12 …… Timing extraction circuit, 13 …… Limiter amplifier.

Claims (1)

(57) [Scope of utility model registration request] 1. An optical input disconnection is detected by amplifying and rectifying an output signal of a timing extraction circuit of an optical receiver for converting light into an electric signal, and comparing the obtained DC voltage with a reference voltage by a comparator. In the alarm circuit, a mark ratio detection circuit whose DC output voltage changes according to the mark ratio change of the transmission signal input to the timing extraction circuit is provided, and the DC voltage from this mark ratio detection circuit is sent to the comparator. An optical input disconnection alarm circuit characterized by being applied as a reference voltage.