JPH04365199A - Light receiver - Google Patents

Abstract

PURPOSE:To obtain an optical receiver which can send an input interruption alarm when an optical signal being inputted is interrupted and whose faulty part can be decided when a circuit fault occurs. CONSTITUTION:The operation abnormalities of a pre-amplifier 2, an equalizing amplifier 3, and a timing extraction circuit 4 are detected by a pre-amplifier abnormality detection circuit 6 to detect level abnormality, an equalizing amplification circuit abnormality detection circuit 7 and a timing extraction circuit abnormality detection circuit 8. The decision of input interruption or the decision of the faulty part is decided by an input interruption/circuit fault decision circuit 9a on the basis of this detection result.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver having a failure detection function.

0002

[Prior Art] Figure 4 shows, for example, the "Optical Communication Handbook"
(edited by Hisayoshi Yanai, September 1980, Asakura Shoten) is a block diagram showing a conventional optical receiver, and in the figure, 1 is a light receiving element, 2 is a preamplifier, 3 is an equalization amplifier circuit, 4 is a timing extraction circuit, 5 is an identification reproducing circuit, and 15 is an input disconnection alarm detection circuit.

Next, the operation will be explained. An input optical signal input to the light receiving element 1 is converted into an electrical signal, and is equalized and amplified via a preamplifier 2 and an equalization amplification circuit 3. A timing extraction circuit 4 generates a clock from the output of the equalization amplifier circuit 3 and outputs it. Further, the identification and regeneration circuit 5 identifies and regenerates the equalized output of the equalization amplifier circuit 3 using the clock generated by the timing extraction circuit 4, and outputs received data. At this time, the input disconnection alarm detection circuit 15 detects the timing extraction circuit 4.
The timing extraction component is monitored, and when the timing extraction component decreases, it is determined that the input optical signal has been cut off, and an input cutoff alarm is output. In this manner, conventional optical receivers detect interruption of an input optical signal using a decrease in the level of one electrical signal within the optical receiver as a criterion for determination.

0004

[Problems to be Solved by the Invention] Conventional optical receivers are configured as described above, so when an input disconnection alarm is sent out, the input optical signal is disconnected due to an abnormality in the transmission path, resulting in an input disconnection alarm. is transmitted, and the electrical signal level to the input disconnection alarm detection circuit 15 decreases due to a circuit failure in the optical receiver, causing an input disconnection even though the input optical signal is not actually disconnected. There was a problem in that it was difficult to determine whether a warning had been sent out or not.

The present invention was made to solve the above-mentioned problems, and when an input disconnection alarm is sent,
If the input optical signal is disconnected due to an abnormality in the transmission line and an input disconnection alarm is sent, or if the electrical level to the input disconnection alarm detection circuit drops due to a circuit failure in the optical receiver, the input optical signal is actually disconnected. It is an object of the present invention to provide an optical receiver having a failure detection function that can determine whether an input disconnection alarm is sent even though an optical signal is not disconnected.

[0006]

[Means for Solving the Problems] An optical receiver according to the present invention includes a light receiving element that converts an input optical signal into an electrical signal, an amplifier circuit that amplifies the electrical signal output from the light receiving element, and an output of the amplifier circuit. In an optical receiver that is equipped with an identification regeneration circuit that demodulates received data and converts an input optical signal into received data, an abnormality detection circuit that detects an abnormal level of the output of the circuit that constitutes the optical receiver is provided. This device is characterized by being provided with a determination circuit that determines the location of the failure based on the detection results.

Further, in the optical receiver having the above configuration, a plurality of the above abnormality detection circuits are provided corresponding to each circuit in the optical receiver, and the above judgment circuit determines a failure location from the level abnormality detection result by each abnormality detection circuit. It is characterized by determining.

[0008]

[Operation] In the optical receiver according to the present invention, the determination circuit determines the location of the failure based on the level abnormality detection result of the abnormality detection circuit.

[0009]Furthermore, level abnormalities are detected by an abnormality detection circuit at a plurality of locations within the optical receiver, and a fault location is determined by a judgment circuit based on each level abnormality detection result. If the optical receiver is disconnected, it detects the input disconnection and sends out an input disconnection alarm, and if a circuit failure occurs within the optical receiver, it detects the circuit failure and determines the location of the failure.

0010

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an optical receiver according to this embodiment. In the figure, numerals 1 to 5 are exactly the same as the conventional example. 6 is a preamplifier abnormality detection circuit that detects an abnormality in the preamplifier; 7 is an equalization amplifier circuit abnormality detection circuit that detects an abnormality in the equalization amplifier circuit; 8 is a timing extraction circuit abnormality detection circuit that detects an abnormality in the timing extraction circuit; 9a 10a to 10c are input disconnection/circuit failure determination circuits that determine input disconnection or circuit abnormality locations from the abnormality detection results from the preamplifier abnormality detection circuit 6, equalization amplifier circuit abnormality detection circuit 7, and timing extraction circuit abnormality detection circuit 8; Inverter gate, 1
1a to 11c are AND gates.

Next, the operation will be explained. An input optical signal input to the light receiving element 1 is converted into an electrical signal, and is equalized and amplified via a preamplifier 2 and an equalization amplification circuit 3. A timing extraction circuit 4 generates a clock from the output of the equalization amplifier circuit 3 and outputs it. Further, the identification and regeneration circuit 5 identifies and regenerates the equalized output of the equalization amplifier circuit 3 using the clock generated by the timing extraction circuit 4, and outputs received data.

At this time, the preamplifier abnormality detection circuit 6
The output level of preamplifier 2 is monitored, and if the output level of preamplifier 2 exceeds the specified range, it is determined that preamplifier 2 is abnormal and outputs "H", and if it is within the specified range, preamplifier 2 is normal. It is determined that this is the case, and outputs "L". Further, the equalization amplifier circuit abnormality detection circuit 7 monitors the electrical level within the equalization amplifier circuit 3, and determines that the equalization amplifier circuit 3 is abnormal when the electrical level exceeds a specified range. If it is within the specified range, it is determined that the equalization amplifier circuit 3 is normal and outputs "L". Similarly,
The timing extraction circuit abnormality detection circuit 8 monitors the electrical level of the timing extraction component in the timing extraction circuit 4,
If the electrical level exceeds the specified range, the timing extraction circuit 4 determines that it is abnormal and outputs "H," and if it is within the specified range, the timing extraction circuit 4 determines that it is normal. Outputs “L”.

Next, the input disconnection/circuit failure determination circuit 9a:
Based on the abnormality detection results from the preamplifier abnormality detection circuit 6, the equalization amplifier circuit abnormality detection circuit 7, and the timing extraction circuit abnormality detection circuit 8, an input disconnection or a circuit abnormality location is determined. Figure 1
Here, a case is shown in which the input disconnection/circuit failure determination circuit 9a is composed of inverter gates 10a to 10c and AND gates 11a to 11c. At this time, Table 1 shows the correspondence between the combinations of the abnormality detection results and the failure locations determined based on the combinations. In addition, in Table 1, the light receiving element 1, the preamplifier 2, the identification reproducing circuit 5, the preamplifier abnormality detection circuit 6
It is assumed that there is no failure in the equalization amplifier circuit abnormality detection circuit 7, the timing extraction circuit abnormality detection circuit 8, and the input disconnection/circuit failure determination circuit 9a.

[0014]

[Table 1]

In Table 1, when the combination of abnormality detection results indicates that the timing extraction circuit 4 is faulty, the AND gate 11a outputs "H" as a timing extraction circuit failure alarm. Similarly, when the equalization amplifier circuit 3 is recognized as having failed, the AND gate 11b outputs "H" as an equalization amplifier circuit failure alarm, and when it is recognized that the optical input has been interrupted, the AND gate 11c outputs "H" as an equalization amplifier circuit failure alarm. As a warning”
Outputs “H”. Also, if there is no abnormality, AND
Gate 11a, AND gate 11b, and AND gate 11c all output "L". In this way, from the abnormality detection results from the preamplifier abnormality detection circuit 6, the equalization amplifier circuit abnormality detection circuit 7, and the timing extraction circuit abnormality detection circuit 8, it is possible to determine whether the optical signal input to the optical receiver has been disconnected or It is possible to determine whether there is a failure in the equalization amplifier circuit 3 or the timing extraction circuit 4 in the optical receiver.

Example 2. Next, FIG. 2 is a block diagram of an optical receiver according to another embodiment of the present invention, in which a light-receiving element abnormality detection circuit 12 for detecting an abnormality in the light-receiving element 1 is added to the configuration of the optical receiver according to the first embodiment. In addition, the input disconnection/circuit failure determination circuit 9 is modified so that the detection result of the light receiving element abnormality detection circuit 12 can be inputted to the input disconnection/circuit failure determination circuit 9a.
b. Light receiving element abnormality detection circuit 12
monitors the output level of the light-receiving element 1, and if the output level of the light-receiving element 1 exceeds the specified range, it determines that the light-receiving element 1 is abnormal and outputs "H", and if it is within the specified range, it outputs "H". The light receiving element 1 is determined to be normal and outputs "L".

The input disconnection/circuit failure determination circuit 9b uses the abnormality detection results from the preamplifier abnormality detection circuit 6, the equalization amplifier circuit abnormality detection circuit 7, the timing extraction circuit abnormality detection circuit 8, and the light receiving element abnormality detection circuit 12. Determine where the input is disconnected or where the circuit is abnormal. Table 2 shows the combination of each abnormality detection result and the correspondence between the failure locations determined from it.
Shown below. In addition, in Table 2, the light receiving element 1, identification regeneration circuit 5, preamplifier output abnormality detection circuit 6, equalization amplifier circuit abnormality detection circuit 7, timing extraction circuit abnormality detection circuit 8, input disconnection/circuit failure determination circuit 9b, and light receiving It is assumed that there is no failure in the element abnormality detection circuit 12. Further, it is assumed that combinations of detection results other than those in Table 2 do not occur.

[0018]

[Table 2]

As can be seen from Table 2, the preamplifier abnormality detection circuit 6, the equalization amplifier circuit abnormality detection circuit 7, the timing extraction circuit abnormality detection circuit 8, and the light receiving element abnormality detection circuit 1.
Based on the abnormality detection results from 2, it can be determined whether the optical signal input to the optical receiver has been disconnected, or whether there is a failure in the preamplifier 2, equalization amplifier circuit 3, or timing extraction circuit 4 in the optical receiver. can be determined.

Example 3. Next, FIG. 3 is a block diagram of an optical receiver according to still another embodiment of the present invention. An input optical signal level abnormality detection circuit 14 for detecting an abnormality in the signal level is added, and the input optical signal level abnormality detection circuit 9b is modified so that the detection result of the input optical signal level abnormality detection circuit 14 can be inputted. This is a replacement for the circuit failure determination circuit 9c.

The input disconnection/circuit failure determination circuit 9c includes a preamplifier abnormality detection circuit 6, an equalization amplifier circuit abnormality detection circuit 7, a timing extraction circuit abnormality detection circuit 8, a light receiving element abnormality detection circuit 12, and an input optical signal level detection circuit 9c. Abnormality detection circuit 1
Based on the abnormality detection results from step 4, the input disconnection or circuit abnormality location is determined. Table 3 shows the correspondence between the combinations of abnormality detection results and the failure locations determined from them. In addition,
In Table 3, the identification reproducing circuit 5, the preamplifier abnormality detection circuit 6, the equalization amplifier circuit abnormality detection circuit 7, the timing extraction circuit abnormality detection circuit 8, the input disconnection/circuit failure determination circuit 9c, the light receiving element abnormality detection circuit 12, and the optical It is assumed that there is no failure in the input level abnormality detection circuit 14. Further, it is assumed that combinations of detection results other than those in Table 3 do not occur.

[0022]

[Table 3]

As can be seen from Table 3, the preamplifier abnormality detection circuit 6, the equalization amplifier circuit abnormality detection circuit 7, the timing extraction circuit abnormality detection circuit 8, the light receiving element abnormality detection circuit 12,
And from the abnormality detection result from the input optical signal level abnormality detection circuit 14, it is determined whether the optical signal input to the optical receiver has been disconnected or whether the light receiving element 1, preamplifier 2, or
It is possible to determine whether there is a failure in the equalization amplifier circuit 3 or the timing extraction circuit 4.

[0024] In the above embodiment, an example of a combination of failure detection of each circuit was shown, but the required circuit failure detection accuracy,
Combinations other than those described above may be selected depending on conditions such as implementation cost.

[0025]

As described above, according to the present invention, it is possible to obtain an optical receiver having a failure detection function in which a determination circuit determines a failure location based on a level abnormality detection result of an abnormality detection circuit.

Furthermore, level abnormalities are detected at multiple locations within the optical receiver, and the location of the failure is determined from the level abnormality detection results at each location, so that the input optical signal is not cut off due to an abnormality in the transmission path. If a failure occurs in the optical receiver, it is possible to detect an input disconnection and issue an input disconnection alarm, and if a failure occurs in the optical receiver, the failure can be sent and the location of the failure can be determined.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an optical receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an optical receiver according to another embodiment of the present invention.

FIG. 3 is a block diagram showing an optical receiver according to yet another embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional optical receiver.

[Explanation of symbols]

1 Light receiving element 2 Preamplifier 4 Timing extraction circuit 5 Identification and regeneration circuit 6 Preamplifier abnormality detection circuit 7 Equalization amplifier circuit abnormality detection circuit 8 Timing extraction circuit abnormality detection circuit 9a to 9c
Input disconnection/circuit failure determination circuits 10a to 10c
Inverter gates 11a to 11c AND gate

Claims (2)

[Claims] 1. A light receiving element that converts an input optical signal into an electrical signal, an amplifier circuit that amplifies the electrical signal output from the light receiving element, and an identification and regeneration circuit that demodulates received data from the output of the amplifier circuit. In an optical receiver that converts an optical signal into received data, an abnormality detection circuit is provided to detect an abnormality in the level of the output of the circuit that constitutes the optical receiver, and a judgment circuit is provided to determine the location of the failure based on the level abnormality detection result. An optical receiver characterized by: 2. The optical receiver according to claim 1, wherein a plurality of the abnormality detection circuits are provided corresponding to each circuit in the optical receiver, and the determination circuit detects a level abnormality from the level abnormality detection result by each abnormality detection circuit. An optical receiver characterized by determining a failure location.