JPH0340539A - Device for detecting disconnection of optical signal input - Google Patents

Abstract

PURPOSE:To surely detect the disconnection of an optical signal input by deciding the 'disconnection' of the optical signal input when the decision of at least one of two optical input disconnection deciding circuits is 'disconnection'. CONSTITUTION:The detection device is provided with a logic circuit 8 for ORing the outputs of respective decided result of the 1st and 2nd optical input disconnection deciding circuits 4, 7. When the amplification gain of a timing component is small, the 1st circuit 4 is accurately driven, and in the case of a large gain, 2nd circuit 7 is accurately driven. When either one of the circuits 4, 7 decides 'disconnection', the 'disconnection' of the optical signal input is decided. Consequently, the disconnection of the optical signal input can be always accurately detected without being influenced by the amplification gain of the timing component.

Description

[Detailed Description of the Invention] [Summary] An RZ-modulated digital optical signal input disconnection detection device in an optical receiver for optical communications can reliably detect an optical signal without being affected by the magnitude of the gain of a timing amplification circuit. The purpose of this system is to detect an interruption in the optical signal input by detecting the peak value of the timing component extracted and amplified by the clock extraction circuit and comparing that peak value with a predetermined threshold. First to judge
The optical input disconnection determination circuit and the timing of the clock output from the clock extraction circuit determine the "interruption" of the optical signal input by comparing the output signal from the photoelectric conversion circuit with a predetermined threshold value. In order to determine that the optical signal input is "off" when at least one of the second optical input disconnection determination circuit and the first and second optical input disconnection determination circuits is "off", the first and second optical input disconnection determination circuits determine that the optical signal input is "off". A logic circuit that takes the logic of the output of each determination result of the second optical input disconnection determination circuit is provided.

[Industrial application field]

The present invention relates to an RZ modulated digital optical signal input disconnection detection device in an optical receiver for optical communication.

Optical communication systems require various failure detection functions in order to discover whether the system is operating normally or not and to discover failure points in the event of an abnormality. Among them,
The function of detecting whether an optical signal is being received or not, that is, whether the optical signal 9 input is disconnected, is an indispensable function of an optical receiver, and is required to operate normally in order to discover failure points.

[Prior Art] In a conventional optical signal input disconnection detection device, first, an optical signal is converted into an electrical signal, and then a timing component extracted from the signal waveform is amplified to detect the peak value of the timing component. By comparing the peak value with a predetermined threshold value, "disconnection" of optical signal input was detected.

[Problem to be solved by the invention]

However, if the gain of the amplifier circuit that amplifies the timing component is large, the amplifier circuit oscillates when the optical signal input is interrupted, and the peak value does not decrease, so that the optical signal input interruption may not be detected.

The present invention eliminates such conventional drawbacks and provides an optical signal input disconnection detection device that can reliably detect optical signal input disconnection without being affected by the magnitude of the gain of the timing amplification circuit. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the optical signal input disconnection detection device of the present invention, as shown in FIG. A timing component is extracted and amplified from the output signal of the circuit 1 and the photoelectric conversion circuit l, and the timing component is extracted from the output signal of the photoelectric conversion circuit l.
a clock extraction circuit 3 which outputs a clock having a phase different by half a wavelength from the output signal of the clock extraction circuit 3; and a clock extraction circuit 3 which detects the peak value of the timing component extracted and amplified by the clock extraction circuit 3, and sets the peak value to a predetermined threshold. The output from the photoelectric conversion circuit l is determined by the timing of the clock output from the first optical input disconnection determination circuit 4, which determines whether the optical signal input is disconnected by comparing with the value, and the clock extraction circuit 3. a second optical input disconnection determination circuit 7 that determines whether the optical signal input is disconnected by comparing the signal with a predetermined threshold; and the first and second optical input disconnection determination circuits 4.
In order to determine that the optical signal input is "OFF" when at least one of the determinations in 7 is "OFF", the first and second optical input disconnection determination circuits 4 and 7 output the determination results. It is characterized by having a logic circuit 8 that takes the logic of .

[Effect]

The RZ optical signal is converted into an electrical signal by a photoelectric conversion circuit 1, and the peak value of the timing component extracted and amplified by a clock extraction circuit 3 is compared with a threshold value by a first optical input disconnection determination circuit 4. , it is determined that the optical signal input is "off".

At the same time, a clock that differs by half a wavelength from the output signal of the photoelectric conversion circuit 1 is transmitted to the clock extraction circuit 3.
is manually input to the second optical input disconnection determination circuit 7, and according to the timing of the clock, the output signal from the photoelectric conversion circuit 1 is compared with a threshold value, and it is determined whether the optical signal input is "interrupted".

Then, the output from the first optical input disconnection determination circuit 4 and the output from the second optical input disconnection determination circuit 7 are input to the logic circuit 8, and one of the two optical input disconnection determination circuits 4.7 is input to the logic circuit 8. When the determination is "off", it is determined that the optical signal input is "off".

〔Example〕

Examples will be described with reference to the drawings.

FIG. 2 is a circuit block diagram of the embodiment. In the figure, 11 is an avalanche photodiode (APD) that inputs an RZ-modulated digital optical signal and converts it into an electrical signal, and this RZ electrical signal output is input to an equalization amplifier circuit 12 where it is equalized and amplified. .

The equalization amplifier circuit 12 detects the peak of the equalized waveform to control the gain, and also feeds back a control signal for controlling the multiplication factor of the APD to the APD bias control circuit 13. This provides automatic gain control. The output signal of the equalization amplifier circuit 12 is output to the identification circuit 5, and the inverted output signal is output to the clock extraction circuit 3 and the second optical input disconnection determination circuit 7.

31, 32, and 33 are a timing extraction circuit, a timing amplification circuit, and a limiter amplification circuit forming the clock extraction circuit 3. Here, a timing extraction circuit 31 first extracts a narrow band timing component from the output data of the equalization amplifier circuit 12, which is amplified by a timing amplifier circuit 32, and then converted into a clock pulse waveform by a limiter amplifier circuit 33. It is formed.

Then, the clock pulse outputted from the limiter amplifier circuit 33 is inputted to the identification circuit 5, and the identification circuit 5 converts the data signal inputted from the equalization amplifier circuit 12 into "1" or "1" at the timing of the clock. 0 is identified and the result is output together with the clock.

The branched output from the timing amplification circuit 32 is input to the first optical input disconnection determination circuit 4. First optical input disconnection determination circuit 4
is the same as the conventional one, in which the timing peak detection circuit 41 detects the peak value of the timing component, and the first comparison circuit 42 compares the peak value with a predetermined threshold value to detect the optical signal. Determination of the presence or absence of input, ie, detection of "off" of optical signal input.

When the determination is "off", the first comparison circuit 42 outputs a signal rlJ, for example.

The first optical input disconnection determination circuit 4 accurately detects optical signal input disconnection even when the gain of the timing amplification circuit 32 is small.

The second optical input disconnection determination circuit 7 is formed by an identification circuit 71, a peak detection circuit 72, and a second comparison circuit 73. Then, the output signal from the equalization amplifier circuit 12 and the limiter amplifier circuit 3 whose phase is shifted by half a wave with respect to the output signal.
The clock pulses from 3 are input to the identification circuit 71.

When the optical signal is input, the identification circuit 71
As shown in FIG. 3, the "L" level of the data signal is identified by the falling edge of the clock pulse which is half a wavelength out of phase with the data signal, and the value of the "L" level is detected by the peak detection circuit 72. Output to. As a result, the output of the identification circuit 71 is always at the "L" level of the emitter coupled logic (E CL ), regardless of the mark rate of the optical signal.

Therefore, the output of the peak detection circuit 72 is naturally ECL
This is the "L" level.

On the other hand, when the optical signal is "off", the input waveform (noise) of the identification circuit 71 is directly input to the peak detection circuit 72 as shown in FIG. The output from the circuit 72 is at the ECL rH'' level.

The output signal of such a peak detection circuit 72 is inputted to the second comparison circuit 73, and there, the above-mentioned "H" level and "L" level are input.
By comparing the threshold value set between the ``level'' and the threshold value set between the
Detection of “disconnection” is performed. When the determination is negative, the second comparison circuit 73 outputs a signal of "1".

When the gain of the timing amplification circuit 32 is small, the second optical input disconnection determination circuit 7 may not be able to accurately measure the optical signal input disconnection due to the small noise component shown in FIG. When the gain of the circuit 32 is large, it is not affected by the gain, and it is possible to accurately detect optical signal input interruption.

The outputs from the first and second comparison circuits 42.73 are inputted to a logic circuit (OR circuit) 8 that calculates a logical sum. Therefore, the output of one of the comparison circuits 42.73 is "l".
”, that is, “OFF”, the output from the OR circuit 8 is “1”.
”, it is determined that the optical signal input is “off”, and O
An alarm circuit 9 connected to the output end of the R circuit 8 issues an alarm by sound or light.

Note that the logic circuit can also be an AND circuit using logical product by taking negative logic.

〔Effect of the invention〕

According to the optical signal input disconnection detection device of the present invention, when the gain of timing component amplification is small, the first optical input disconnection determination circuit operates accurately, and when the gain of timing component amplification is large, the second optical input disconnection determination circuit operates. If the circuit operates correctly and one of them is determined to be "off", the optical signal input will be determined as "off", so the optical signal input will always be accurate without being affected by the magnitude of the gain of the timing component amplification. disconnection can be detected.

[Brief explanation of drawings]

FIG. 1 is a diagram of the principle of the present invention, FIG. 2 is a circuit block diagram of an embodiment, and FIGS. 3 and 4 are explanatory diagrams of the operation of the second optical input disconnection determination circuit. In the figure, 1... Photoelectric conversion circuit, 3... Clock extraction circuit, 4... First optical input disconnection determination circuit, 7... Second optical input disconnection determination circuit, 8... Logic circuit.

Claims (1)

[Claims] A photoelectric conversion circuit (1) that inputs an RZ-modulated digital optical signal, converts it into an electrical signal, and outputs it; and a timing component that extracts a timing component from the output signal of the photoelectric conversion circuit (1). a clock extraction circuit (3) that amplifies the output signal of the photoelectric conversion circuit (1) and outputs a clock having a phase different by half a wavelength from the output signal of the photoelectric conversion circuit (1);
a first optical input disconnection determination circuit (4) that determines whether or not the optical signal input is disconnected by detecting the peak value of the timing component extracted and amplified by and comparing the peak value with a predetermined threshold; ), and by comparing the output signal from the photoelectric conversion circuit (1) with a predetermined threshold value according to the timing of the clock output from the clock extraction circuit (3), the optical signal input is "cut off". and a second optical input disconnection determination circuit (7) that determines whether the optical signal is input when at least one of the first and second optical input disconnection determination circuits (4, 7) is determined to be “OFF” "
and a logic circuit (8) that takes the logic of the outputs of the determination results of the first and second optical input disconnection determination circuits (4, 7) in order to determine that the optical input disconnection determination circuit (4, 7) is disconnected. Optical signal input disconnection detection device.