JPH11205228A - Alarm monitor circuit for optical fiber amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the versatility of an aspect where the location of use of an optical fiber amplifier is not limited by expanding a dynamic range of a detection level. SOLUTION: An optical signal OP2 branched by a 2-branch optical coupler 1 is given to a photo diode 2 through an optical fiber F2, and a current signal IS subject to photoelectric conversion at a photodiode 2 is given to a logarithmic amplifier 3 for current voltage conversion. The logarithmic amplifier 3 amplifies a level of a received current signal IS linearly in terms of logarithm and given to a voltage comparator 4 as a voltage signal LA. The voltage comparator 4 compares the received voltage signal LA with a predetermined alarm threshold voltage signal TH and outputs the comparison result as an alarm signal AR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alarm monitoring circuit for an optical fiber amplifier (hereinafter referred to as an alarm monitoring circuit) applied to, for example, a large-capacity long-distance trunk system.

[0002]

2. Description of the Related Art In the field of optical communication, an optical fiber amplifier is an indispensable item in a long-distance backbone optical transmission system. In addition, a technique for monitoring the optical level in the transmission line is also indispensable, and particularly, the optical level monitoring in the input / output unit of the optical fiber amplifier is important.

Therefore, an alarm monitoring circuit incorporated in an optical fiber amplifier will be described below. FIG. 9 is a block diagram showing a conventional alarm monitoring circuit. In FIG.
1 is a two-branch optical coupler for branching a part of an optical signal, 92 is a photodiode for optical-to-electric conversion of an optical signal, 93 is a linear amplifier for current-to-voltage conversion of an electric signal and amplified, 94
Is a resistor for setting the amplification gain of the linear amplifier 93, 95 is a voltage comparator for comparing the signal output from the linear amplifier 93 with a certain threshold value and outputting a binary value, and 96A, 9
6B and 96C are optical fibers.

[0004] Subsequently, regarding the signal, OP1 is an optical signal, O
P2 is an optical signal branched by the optical coupler 91, IS is a current signal photoelectrically converted by the photodiode 92, VS is a voltage signal current-voltage converted by the linear amplifier 93, T
H is an alarm threshold voltage signal indicating an alarm issuance level serving as a comparison reference of the voltage comparator 95, and AR is a result obtained when the voltage signal VS is compared with the alarm threshold voltage signal TH by the voltage comparator 95. This is an alarm signal.

Next, the operation will be described. In the alarm monitoring circuit shown in FIG. 9, a part of the optical signal OP1 is branched by the two-branch optical coupler 91, and one optical signal OP2 of the two branched signals is input to the photodiode 92. The current signal IS photoelectrically-electrically converted by the photodiode 92 is input to a linear amplifier 93 for current-voltage conversion, amplified by an amount determined by a resistor 94, becomes a voltage signal VS, and is input to a voltage comparator 95. . In the voltage comparator 95, a predetermined alarm threshold voltage signal TH is compared with the voltage signal VS, and the comparison result is issued as an alarm signal AR.

[0006]

Since the conventional alarm monitoring circuit is configured as described above, the photodiode 9
2 and the linear amplifier 93 perform linear detection,
In this case, the logarithm (dBm) which is a unit of the light level is usually used.
Requires a wide dynamic range for detection. Therefore, the light level could be detected only at a specific level. That is, in many optical fiber amplifiers used in the optical transmission system, since the light detection level is different depending on the use place of the optical fiber amplifier, the installation place of the optical fiber amplifier is limited. There was a problem of lack of sex.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and expands the dynamic range of light level detection to improve versatility in that the use place of an optical fiber amplifier is not limited. It is an object of the present invention to obtain an alarm monitoring circuit capable of performing the operation.

[0008]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, an alarm monitoring device according to the present invention includes:
In an alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, an input current signal obtained by optical-to-electric conversion of an optical signal is current-to-voltage converted and logarithmically amplified. A current-voltage converter for obtaining a voltage signal, and an alarm issuing unit for issuing an alarm signal in accordance with the level of the voltage signal obtained by the current-voltage converter are provided.

According to the present invention, an input current signal obtained by optical-to-electric conversion of an optical signal is subjected to current-to-voltage conversion and logarithmically linearly amplified, and an alarm signal is issued in accordance with the level of the voltage signal. The dynamic range of the detection level is expanded by a simple configuration,
It is possible to improve the versatility of the optical fiber amplifier without limiting the place where it is used.

An alarm monitoring device according to the present invention is an alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein an input current signal obtained by optical-to-electric conversion of an optical signal is converted. Current-voltage conversion means for obtaining a voltage signal amplified logarithmically by current-voltage conversion, and level determination for determining whether the level of the voltage signal obtained by the current-voltage conversion means is equal to or higher than a certain level Means,
When the level judgment means obtains a judgment result of the predetermined level or more, the voltage signal obtained by the current-voltage conversion means is linearly amplified, and an alarm is issued in accordance with the level of the voltage signal obtained by the linear amplification. A first alarm issuance unit for issuing a signal; and if the level determination unit obtains a determination result of less than the predetermined level, an alarm signal is issued in accordance with the level of the voltage signal obtained by the current-voltage conversion unit. And a second alarm issuing means.

According to the present invention, high-level detection with low detection accuracy is compensated for by linear amplification, so that the same high detection accuracy is always obtained regardless of the level of the detection level. Since the amplifier can be inserted anywhere in the long-distance backbone optical transmission system,
It is possible to improve the versatility of the optical fiber amplifier without limiting the place where it is used.

According to another aspect of the present invention, there is provided an alarm monitoring apparatus for an optical fiber amplifier applied to a long-distance trunk optical transmission system, wherein an input current signal obtained by optical-to-electric conversion of an optical signal is obtained. A level determining means for determining whether or not the level is equal to or higher than a certain level; and a current for attenuating the input current signal by a logarithmic linear rate at a certain rate when the level determining means obtains a result equal to or higher than the certain level. Attenuating means, first alarm issuing means for performing a current-voltage conversion on the current signal attenuated by the current attenuating means, then linearly amplifying the signal, and issuing an alarm signal according to the level of the voltage signal; and the level determining means When the result of the determination is less than the predetermined level, the input current signal is subjected to current-voltage conversion and then linearly amplified, and the level of the voltage signal obtained by the linear amplification is obtained. Characterized by comprising a second warning issuing means for issuing an alarm signal in response to.

According to the present invention, the detection of the high level is attenuated to a level that can be linearly detected at the stage of the electric signal, so that the dynamic range of the detection level is expanded, and regardless of the magnitude of the detection level. The same high detection accuracy is always obtained, which allows the optical fiber amplifier to be inserted into any location in a long-distance backbone optical transmission system, thereby improving the versatility of the optical fiber amplifier without limiting the use place. It is possible.

An alarm monitoring device according to the present invention is an alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein the optical attenuating means for logarithmically attenuating an input optical signal; Monitoring means for issuing an alarm signal in accordance with the monitoring state of the optical signal attenuated by the light attenuating means.

According to the present invention, the level is logarithmically attenuated at the optical signal stage, and the logarithmic light level is detected as it is as a linear level. Therefore, the dynamic range of the detection level is expanded by a simple configuration. As a result, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, so that it is possible to improve the versatility of the optical fiber amplifier without limiting the use place.

According to another aspect of the present invention, there is provided an alarm monitoring device for an optical fiber amplifier applied to a long-distance backbone optical transmission system, comprising: a multi-branch means for equally multi-branching an input optical signal; A plurality of optical-to-electrical conversion means for obtaining a current signal by optically-to-electrically converting the plurality of optical signals branched by the branching means, and a plurality of current signals obtained by the plurality of optical-to-electrical conversion means A plurality of alarm issuing means for performing voltage conversion and then linearly amplifying each with a different gain, and issuing an alarm signal according to the level of each voltage signal obtained by the linear amplification. .

According to the present invention, the level detection is performed in accordance with the input light by performing multi-branch at the optical signal stage and then performing linear amplification with different gains, so that the dynamic range of the detection level is expanded. In addition, since the detection accuracy is improved, and the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, the versatility of the optical fiber amplifier can be improved without limiting the use place. It is possible.

The alarm monitoring device according to the next invention is an alarm monitoring circuit for an optical fiber amplifier applied to a long-distance trunk optical transmission system, which is connected in series and separates each input optical signal by a different branching ratio. A plurality of two-branching means for branching and outputting one to a subsequent stage and outputting the other for monitoring;
A plurality of light-to-electric conversion means for obtaining a current signal by performing light-to-electric conversion on each of the branched optical signals for monitoring; and And a plurality of warning issuing means for issuing a warning signal according to the level of each voltage signal obtained by the linear amplification after the conversion.

According to the present invention, the optical signal is branched so as to have different levels at each stage, and the level detection is performed according to each input light by linearly amplifying each optical signal. The dynamic range of the level has been expanded and the detection accuracy has been improved, which allows the optical fiber amplifier to be inserted into any part of a long-distance backbone optical transmission system. It is possible to improve versatility.

An alarm monitoring apparatus according to the next invention is an alarm monitoring circuit for an optical fiber amplifier applied to a long-distance trunk optical transmission system, which is connected in series and separates each input optical signal by a different branching ratio. A plurality of two-branching means for branching and outputting one to a subsequent stage and outputting the other for monitoring;
A plurality of light-to-electric conversion means for obtaining a current signal by performing light-to-electric conversion on each of the branched monitoring light signals, and a plurality of current signals obtained by the plurality of light-to-electric conversion means, Selecting means for selecting one of the current signals within the set signal level range; current-to-voltage conversion of the current signal selected by the selecting means, followed by linear amplification, and the voltage obtained by the linear amplification Alarm issuing means for issuing an alarm signal according to the signal level.

According to the present invention, an optical signal is branched so as to have different levels at the optical signal stage, and an optical signal within a preset signal level range is linearly amplified, thereby inputting only one point. Since the level detection is performed according to the light, the dynamic range of the detection level is expanded, and the detection accuracy is improved. As a result, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system. Therefore, it is possible to improve the versatility of the optical fiber amplifier in the aspect that the use place is not limited.

An alarm monitoring device according to the next invention is an alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, which converts an input current signal obtained by optical-to-electric conversion of an optical signal. First alarm issuing means for performing current-voltage conversion, then linearly amplifying, and issuing an alarm signal in accordance with the level of the voltage signal obtained by the linear amplification;
The voltage signal obtained by the linear amplification of the first alarm issuing means is connected to the linear amplification output of the alarm issuing means.
And a second alarm issuing unit that performs linear amplification with a gain different from that of the alarm issuing unit and issues an alarm signal in accordance with the level of the voltage signal obtained by the linear amplification.

According to the present invention, since the linear amplification is performed in multiple stages at the stage of the electric signal, the dynamic range of the detection level is expanded, whereby the optical fiber amplifier can be used for a long-distance backbone optical transmission system. Since the optical fiber amplifier can be inserted into any place, it is possible to improve the versatility of the optical fiber amplifier in the aspect that the use place is not limited.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the alarm monitoring circuit for an optical fiber amplifier according to the present invention will be described below in detail with reference to the accompanying drawings.

Embodiment 1 First, the configuration will be described. FIG. 1 is a block diagram showing an alarm monitoring circuit according to Embodiment 1 of the present invention. In the figure, 1 is a two-branch optical coupler for branching a part of an optical signal, 2 is a photodiode for performing optical-to-electrical conversion of an optical signal, and 3 is a current-to-voltage conversion of an electrical signal for logarithmic linear (function). Log amp to amplify,
4 is a log amplifier output signal L output from the log amplifier 3
A voltage comparator that compares A with a certain threshold value (warning threshold voltage signal TH) and issues a warning signal (binary) according to the comparison result, and F1, F2, and F3 are optical fibers, respectively. . In FIG. 1, the same signals as those shown in FIG. 9 (conventional example) are denoted by the same reference numerals, and description thereof will be omitted.

Next, the operation will be described. In the alarm / warning circuit for the optical fiber coupler shown in FIG. 1, a part of the optical signal OP1 transmitted through the optical fiber F1 is branched by the two-branch optical coupler 1, and the branched optical signal OP2 is transmitted through the optical fiber F2. The signal is input to the photodiode 2. The current signal IS that has been photoelectrically converted by the photodiode 2 is input to a log amplifier 3 for current-voltage conversion. In the log amplifier 3, the input current signal IS is logarithmically amplified and input as a voltage signal VS to the voltage comparator 4. In the voltage comparator 4, the input voltage signal VS
Is compared with a predetermined alarm threshold voltage signal TH, and the comparison result is issued as an alarm signal AR.

As described above, according to the first embodiment, since the log amplifier 3 is used, the light level expressed by a logarithm (dBm) is normally detected as a linear value as it is. With a simple configuration, the dynamic range of the detection level is expanded, and it is possible to cope with any setting of the light level. Accordingly, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, so that it is possible to improve the versatility of the optical fiber amplifier without limiting the use place.

Embodiment 2 In the first embodiment, the log amplifier 3 (see FIG. 1) is used to expand the dynamic range. However, as in the second embodiment described below, only the high light level is amplified. The detection accuracy may be improved. Note that the second embodiment
In the figure, the same configurations and signals as those in the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

First, the configuration will be described. FIG. 2 is a block diagram showing an alarm monitoring circuit according to Embodiment 2 of the present invention. In the figure, 5 is a log amplifier output signal LA
A voltage selector for selecting an output destination by comparing with a certain threshold value; 6 a resistor for setting the amplification gain of the linear amplifier 7;
Is a linear amplifier that linearly amplifies the signal calibrated by the resistor 6, 8 is a resistor that sets the amplification gain, 9 is a binary amplifier that compares the signal amplified by the linear amplifier 7 and the resistor 8 with a certain threshold. Is a voltage comparator.

Subsequently, regarding the signals, VTH is an alarm threshold voltage signal input to the voltage selector 5, LA1 and LA2 are log amplifier output signals output from the voltage selector 5, respectively, and TH1 is input to the voltage comparator 4. Alarm threshold voltage signal TH2, an alarm threshold voltage signal input to the voltage comparator 9, VS is a voltage signal amplified by the linear amplifier 7 and the resistor 8, and AR1 is a comparison result of the voltage comparator 4. The alarm signal AR2 is an alarm signal which is a comparison result of the voltage comparator 9.

In the above configuration, the voltage selector 5
The configuration of the two-branch optical coupler 1, the photodiode 2 and the log amplifier 3 in the first stage and the voltage comparator 4 in the second stage are the same as those in the first embodiment.

Next, the operation will be described. In the alarm monitoring circuit shown in FIG. 2, a part of the optical signal OP1 is branched by the optical coupler 1, and the branched optical signal OP2 is input to the photodiode 2. This photodiode 2
Is input to the log amp 3 for current-voltage conversion. In the log amplifier 3, the input current signal IS is logarithmically linearly amplified, and is input as a log amplifier output signal LA to the voltage selector 5.

The voltage selector 5 compares the predetermined alarm threshold voltage signal VTH with the log amplifier output signal LA. As a result, when the level of the log amplifier output signal LA is equal to or higher than the alarm threshold level, the log amplifier output signal LA1 is output to the path to the resistor 6 as a log amplifier output signal LA1. Output signal LA
2 is output to the path to the voltage comparator 4.

The log amplifier output signal LA 1 is linearly amplified by a gain determined by the resistors 6 and 8 in the linear amplifier 7 to become a voltage signal VS, which is input to the voltage comparator 9. In the voltage comparator 9, a predetermined alarm threshold voltage signal TH2 is compared with the input voltage signal VS, and the comparison result is issued as an alarm signal AR2.

On the other hand, when the log amplifier output signal LA2 is selected by the voltage selector 5, the log amplifier output signal LA2
2 is input to the voltage comparator 4 as it is. In the voltage comparator 4, a predetermined alarm threshold voltage signal TH1
Is compared with the log amplifier output signal LA2, and the comparison result is issued as an alarm signal AR1.

As described above, according to the second embodiment, not only can the dynamic range of the detection level be expanded by the log amplifier 3 as in the first embodiment, but also the Is compensated by the linear amplifier 7, so that the same high detection accuracy is always obtained regardless of the level of the detection level. This allows
Since the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, it is possible to improve the versatility of the optical fiber amplifier in terms of not restricting the use place.

Embodiment 3 In the second embodiment described above, the log amplifier 3 is used to expand the dynamic range of the detection level. However, as in the third embodiment described below, only the high-level detection portion is electrically operated. The detection accuracy may be increased by attenuating in stages. In the second embodiment, the first embodiment described above is used.
The same reference numerals are given to the same configurations and signals as those described above, and description thereof will be omitted.

First, the configuration will be described. FIG. 3 is a block diagram showing an alarm monitoring circuit according to Embodiment 3 of the present invention. In the figure, reference numeral 10 denotes a current selector which determines whether or not an input current signal is equal to or more than a certain threshold value by comparing the input current signal with a certain threshold value and then selects an output destination;
11 is a current attenuator for attenuating the current signal at a constant rate,
Reference numeral 12 denotes a resistor for setting an amplification gain, and reference numeral 13 denotes a linear amplifier for current-to-voltage conversion of an electric signal for amplification.

Subsequently, regarding the signals, ITH is a threshold current signal input to the current selector 10, IS1 and IS2 are current signals output from the current selector 10, respectively, IS1
1 is an attenuated current signal output from the current attenuator 11, VS1 is a voltage signal output from the linear amplifier 13 and the resistor 12, and VS2 is a linear amplifier 7 and the resistor 8
Is a voltage signal output from.

In the above configuration, the current selector 1
The configuration of the two-branch optical coupler 1 and the photodiode 2 in the stage preceding 0, and the configurations of the linear amplifier 7, the resistor 8 and the current comparator 9 in the stage following the current attenuator 11 are the same as those in the second embodiment. It is a structure of.

Next, the operation will be described. In the alarm monitoring circuit shown in FIG. 3, a part of the optical signal OP1 is branched by the optical coupler 1, and the branched optical signal OP2 is input to the photodiode 2. The current signal IS subjected to the photoelectric conversion by the photodiode 2 is input to the current selector 10.

In the current selector 10, a predetermined threshold current signal ITH is compared with an input current signal IS. As a result, when the level of the input current signal IS is equal to or higher than the threshold level, the input current signal IS becomes the current signal I
The signal is output to the path of the current attenuator 11 as S1. On the other hand, when the level of the input current signal IS is equal to or lower than the threshold level, the input current signal IS is output to the path of the linear amplifier 13 as the current signal IS2.

The current signal IS1 is logarithmically linearly attenuated by the current attenuator 11 at a constant rate, and the current signal IS1 is attenuated.
Becomes This attenuated current signal IS11 is input to a linear amplifier 7 for current-voltage conversion and amplification. In the linear amplifier 7, the attenuation current signal IS11 is linearly amplified by a gain determined by the resistor 8, and output to the voltage comparator 9 as the voltage signal VS2. When this voltage signal VS2 is inputted to the voltage comparator 9, it is compared with a predetermined alarm threshold voltage signal TH2, and the comparison result is an alarm signal A
Issued as R2.

On the other hand, when the current signal IS is output from the current selector 10 as IS2, the current signal IS2 is input to the linear amplifier 13 for current-voltage conversion and amplification. In the linear amplifier 13, the current signal IS2 is linearly amplified by a gain determined by the resistor 12, and is output as a voltage signal VS1. This voltage signal V
S1 is input to the voltage comparator 4. This voltage comparator 4
Then, a predetermined alarm threshold voltage signal TH1 is compared with an input voltage signal VS1, and the comparison result is issued as an alarm signal AR1.

As described above, according to the third embodiment, the detection of the high level is also attenuated to the level that can be linearly detected at the stage of the electric signal, so that the dynamic range of the detection level is expanded and , The same high detection accuracy is always obtained regardless of the level of the detection level. Accordingly, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, so that it is possible to improve the versatility of the optical fiber amplifier without limiting the use place.

Embodiment 4 FIG. In the first to third embodiments described above, the dynamic range of the detection level is expanded in the electric stage. However, as in the fourth embodiment described below, the dynamic range of the detection level is increased in the optical stage. You may enlarge it. In addition, this Embodiment 4
In the following, the same configurations and signals as those in the above-described first to third embodiments are denoted by the same reference numerals, and description thereof will be omitted.

First, the configuration will be described. FIG. 4 is a block diagram showing an alarm monitoring circuit according to Embodiment 4 of the present invention. In the figure, reference numeral 14 denotes an optical attenuator that attenuates the input light level in a logarithmic linear manner, and F4 denotes an optical fiber. OP3 is an optical signal output from the optical attenuator 14.

In the alarm monitoring circuit shown in FIG. 4, the configuration composed of the resistor 12, the linear amplifier 13, and the voltage comparator 4 used in the third embodiment is connected downstream of the two-branch optical coupler 1. In the fourth embodiment, since the dynamic range is expanded in the optical stage, the above-described optical attenuator 14 is connected between the two-branch optical coupler 1 and the photodiode 2 via optical fibers F2 and F4.

Next, the operation will be described. In the alarm monitoring circuit shown in FIG. 4, a part of the optical signal OP1 is split by the two-branch optical coupler 1, and the split optical signal OP2 is input to the optical attenuator 14 through the optical fiber F2. The optical attenuator 14 attenuates the input light level in a logarithmic linear manner with the input optical signal OP2 and outputs it as an optical signal OP3. The optical signal OP3 is input to the photodiode 2 through the optical fiber F4.

The current signal IS photoelectrically converted by the photodiode 2 is input to a current-voltage conversion linear amplifier 13 and is amplified by an amount determined by the resistor 12 to become a voltage signal VS and become a voltage comparator VS. 4 is input. In the voltage comparator 4, a predetermined alarm threshold voltage signal TH is compared with an input voltage signal VS, and the comparison result is issued as an alarm signal AR.

As described above, according to the fourth embodiment, the level is logarithmically attenuated at the optical signal stage, and the logarithmic light level is detected as it is as a linear level. Thereby, the dynamic range of the detection level can be expanded. Accordingly, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, so that it is possible to improve the versatility of the optical fiber amplifier without limiting the use place.

Embodiment 5 FIG. In the fourth embodiment, the dynamic range is expanded by using the optical attenuator 14 (see FIG. 4). However, as in the fifth embodiment described below, an optical signal is The dynamic range may be expanded by branching and detecting the level with a different gain at each branch destination. In the fifth embodiment, the same configurations and signals as those in the above-described fourth embodiment are denoted by the same reference numerals, and description thereof will be omitted.

First, the configuration will be described. FIG. 5 is a block diagram showing an alarm monitoring circuit according to Embodiment 5 of the present invention. 2, 2A, 2B, 2C, and 2D are photodiodes having the same configuration and function as the photodiode 2, respectively, and 4A, 4B, 4C, and 4D are electrical comparison devices having the same configuration and function as the electrical comparator 4, respectively. The resistors 12A, 12B, 12C, and 12D have the same configuration and function as the resistor 12, respectively, and have resistors 13A, 13B, 13C,
13D is a linear amplifier having the same configuration and function as the linear amplifier 13, and 15 is an input optical signal O
A multi-branch optical star coupler that branches and outputs P2 into four, and F31, F32, F33, and F34 are a star coupler 15 and photodiodes 2A, 2B, 2C, and 2D, respectively.
And an optical fiber for connecting to the optical fiber.

Subsequently, regarding signals, OP31, OP3
2, OP33, OP34 are optical signals branched by the multi-branch optical star coupler 15, IS1, IS2, IS3, respectively.
IS4 is a photodiode 2A, 2B, 2C,
2D opto-electrically converted current signals, VS1, VS2
VS3 and VS4 are linear amplifiers 13A and 13A, respectively.
B, 13C, 13D, the amplified voltage signals, TH1, T
H2, TH3 and TH4 are voltage comparators 4A and 4
B, 4C, 4D alarm threshold voltage signals supplied to
AR1, AR2, AR3, and AR4 are alarm signals that are comparison results of the voltage comparators 4A, 4B, 4C, and 4D, respectively.

Next, the operation will be described. In the alarm monitoring device shown in FIG. 5, a part of the optical signal OP1 is split by the optical coupler 1, and the split optical signal OP2 is input to the optical star coupler 15. The multi-branch optical star coupler 15 divides the input light level by one-fourth and outputs from each port. That is, the optical signals OP31, OP32, OP output from the multi-branch optical star coupler 15
33 and OP34 are input to the photodiodes 2A, 2B, 2C and 2D for photoelectric conversion, respectively.

The photodiodes 2A, 2B, 2C, 2D
Current signals IS1 and IS which have been converted from light to electricity, respectively.
2, IS3, and IS4 are input to current-voltage conversion linear amplifiers 13A, 13B, 13C, and 13D. In each of the linear amplifiers 13A, 13B, 13C, and 13D, resistors 12A, 12B, 12C,
Voltage signals VS1 and VS are amplified by an amount determined by 12D.
2, VS3, VS4 and the voltage comparators 4A, 4B, 4
C, 4D.

In each of voltage comparators 4A, 4B, 4C and 4D, a predetermined alarm threshold voltage signal T
H1, TH2, TH3, TH4 and the input voltage signal VS1,
VS2, VS3, and VS4 are compared, and the comparison results are issued as alarm signals AR1, AR2, AR3, and AR4, respectively.

As described above, according to the fifth embodiment, since four ports for level detection are provided, linear amplifiers 13A, 13B, 13C, 13
D, resistors 12A, 12B, 12 for setting the gain
If the values of C and 12D are appropriately changed and set, light levels are detected at different levels.

That is, the level detection according to the input light is performed by multi-branching at the optical signal stage and then linearly amplifying with different gains, so that the dynamic range of the detection level is expanded and the detection accuracy is improved. Can be improved. Accordingly, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, so that it is possible to improve the versatility of the optical fiber amplifier without limiting the use place.

Embodiment 6 FIG. In the fifth embodiment described above, the optical signal is branched at the optical stage using the multi-branch optical star coupler 15 (see FIG. 5). However, as in the sixth embodiment described below, the branching is performed. A two-branch optical coupler having a different ratio may be connected in multiple stages to branch an optical signal at the optical stage. In the sixth embodiment, the same components and signals as those in the fifth embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

First, the configuration will be described. FIG. 6 is a block diagram showing an alarm monitoring circuit according to Embodiment 6 of the present invention. In FIG. 1, 1A has the same configuration and function as the above-described two-branch optical coupler 1, and includes optical fibers F1 and F1.
2-branch optical coupler 1B, 1 connected to F2 and F3
Reference numerals C and 1D denote two-branch optical couplers each of which splits an input optical signal into two at different branch ratios and outputs the split signal. F41 denotes an optical fiber connecting the two-branch optical coupler 1B and the photodiode 2A. An optical fiber connecting the couplers 1B and 1C, F51 is an optical fiber connecting the two-branch optical coupler 1C and the photodiode 2B, F52 is an optical fiber connecting the two-branch optical couplers 1C and 1D, and F61 is a two-branch optical coupler 1D. F62 is an optical fiber connecting the two-branch optical coupler 1D and the photodiode 2D.

In the above configuration, the photodiode 2
The configuration and connection at the subsequent stage of A to 2D are as shown in FIG.
The description is omitted because it is the same as in the above-described fifth embodiment.
However, in the fifth embodiment described above, the resistors 12A, 12A
Although the resistance values of B, 12C, and 12D are set differently, in the sixth embodiment, the resistance values are all set to the same value. Regarding signals, OP41 and 42 are optical signals branched by the two-branch optical coupler 1B, OP51 and 52 are optical signals branched by the two-branch optical coupler 1C, and OP61 and 62 are two-branch optical couplers 1D. This is a branched optical signal.

Next, the operation will be described. In the alarm monitoring device shown in FIG. 6, a part of the optical signal OP1 is branched by the two-branch optical coupler 1A, and the branched optical signal OP1
2 is input to the two-branch optical coupler 1B. In the two-branch optical coupler 1B, the input light level of the optical signal OP2 is bifurcated at different branch ratios. One of the branched output optical signals O
P41 is input to the photodiode 2A, and the other output optical signal OP42 is input to the two-branch optical coupler 1C.

In the two-branch optical coupler 1C, similarly to the above-described two-branch optical coupler 1B, the input light level of the input optical signal OP42 is branched into two. One of the branched output optical signals OP51 is input to the photodiode 2B, and the other output optical signal OP52 is input to the two-branch optical coupler 1D. In the two-branch optical coupler 1D, similarly to the above-described two-branch optical couplers 1B and 1C, the input optical level of the input optical signal OP52 is bifurcated. One of the branched output optical signals OP61 is input to the photodiode 2C, and the other output optical signal OP62 is input to the photodiode 2D.

Thus, the photodiodes 2A,
The optical signals OP41 and OP5 are respectively applied to 2B, 2C and 2D.
After 1, OP61 and OP62 are input, signal processing is performed in the same manner as in the fifth embodiment. However,
In the linear amplifiers 13A to 13D, the resistors 12A to 1
The amplification is the same in that 2D has the same resistance value. As a result, each of the voltage comparators 4A, 4B, 4C, and 4D outputs a predetermined alarm threshold voltage signal TH.
1, TH2, TH3, TH4 and input voltage signals VS1, V
S2, VS3 and VS4 are compared, and the comparison results are issued as alarm signals AR1, AR2, AR3 and AR4, respectively.

As described above, according to the sixth embodiment, four ports are provided for branching and detecting the level so as to have different levels at the optical signal stage, and each optical signal level is Set differently. Therefore, if the detection level is set at a level with high sensitivity of the light receiving level in each of the photodiodes 2A, 2B, 2C, and 2D, the dynamic range of the detection level can be expanded and the detection accuracy can be improved. Accordingly, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, so that it is possible to improve the versatility of the optical fiber amplifier without limiting the use place.

Embodiment 7 In the sixth embodiment described above, amplification is performed on each of the four ports for level detection. However, as in the seventh embodiment described below, amplification is performed on only one of the four ports. You may. In the seventh embodiment, the same components and signals as those in the sixth embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

First, the configuration will be described. FIG. 7 is a block diagram showing an alarm monitoring circuit according to Embodiment 7 of the present invention. In the drawing, reference numeral 16 denotes a multi-input current selector for selecting and outputting only a signal within a predetermined detection level range among a large number of input current signals IS1 to IS4, and 17 a configuration and function similar to those of the resistor 12. Is a linear amplifier having the same configuration and function as the linear amplifier 13, and 19 is an electrical comparator having the same configuration and function as the electrical comparator 4. Also,
Regarding the signal, IS5 is a current signal selected and output by the multi-input current selector 16.

In the seventh embodiment, the configuration up to the previous stage of the multi-input current selector 15, that is, the photodiodes 2A to 2A
The configuration up to 2D is the same as that of the sixth embodiment.
A photodiode 2A is provided at a stage preceding the multi-input current selector 16.
To 2D, and the subsequent stage has a multi-input current selector 16
The resistor 17, the linear amplifier 18, and the current comparator 19, which amplify the one current signal selected in the above, are connected.

Next, the operation will be described. Note that the operation up to the multi-input current selector 16 is the same as in the above-described sixth embodiment, and a description thereof will be omitted. In the alarm monitoring device shown in FIG. 7, the photodiodes 2A, 2B, 2
The current signal IS that has been photoelectrically converted by C and 2D, respectively.
1, IS2, IS3, and IS4 are all input to the multi-input current selector 16. In this multi-input current selector 16,
From the input current signals IS1 to IS4, one signal within a predetermined detection level range is selected, and the selected signal is output as a current signal IS5.

The current signal IS 5 selected by the multi-input current selector 16 is input to a current-voltage conversion linear amplifier 18, and is amplified by an amount determined by the resistor 17 to obtain a voltage signal V 5.
S is input to the voltage comparator 19. In the voltage comparator 19, a predetermined alarm threshold voltage signal TH is compared with the input voltage signal VS, and the comparison result is issued as an alarm signal AR.

As described above, according to the seventh embodiment, there are four ports for level detection, and the respective optical signal levels are different, so that the sensitivity of the light receiving levels of the photodiodes 2A to 2D is good. If the detection level is set by the level, the dynamic range of the detection level can be widened and the detection accuracy can be improved. In particular, by providing the multi-input selector 15, linear amplification is performed on an optical signal within a preset signal level range. Therefore, level detection according to the input light of only one point can be performed.

As described above, also in the seventh embodiment, since the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, the versatility of the optical fiber amplifier in terms of the use place is not limited. It is possible to

Embodiment 8 FIG. In the present invention, the dynamic range of the detection level may be expanded by connecting linear amplifiers in multiple stages as in the eighth embodiment described below. In addition, this Embodiment 8
Here, the same configurations and signals as those in the above-described third embodiment are denoted by the same reference numerals, and description thereof will be omitted.

First, the configuration will be described. FIG. 8 is a block diagram showing an alarm monitoring circuit according to Embodiment 8 of the present invention. In the eighth embodiment, the two linear amplifiers 7 and 13 used in the third embodiment are applied. That is, in the subsequent stage of the two-branch optical coupler 1 and the photodiode 2, the configuration including the linear amplifier 13, the resistor 12, and the voltage comparison circuit 4 shown in FIG. 9 are connected in multiple stages. This multi-stage connection is realized by connecting the input of the resistor 6 to the output of the linear amplifier 13.

Next, the operation will be described. In the alarm monitoring device shown in FIG. 8, a part of the optical signal OP1 is split by the optical coupler 1, and the split optical signal OP2 is input to the photodiode 2. This photodiode 2
The current-to-electrical-converted current signal IS is input to a current-to-voltage conversion linear amplifier 13, amplified by an amount determined by the resistor 12, and input to the voltage comparator 4 as a voltage signal VS 1. In the voltage comparator 4, a predetermined alarm threshold voltage signal TH1 is compared with an input voltage signal VS1, and the comparison result is issued as an alarm signal AR1.

The voltage signal VS1 is supplied to the linear amplifier 7
The voltage is amplified by an amount determined by the resistors 6 and 8 and output as a voltage signal VS2, which is input to the voltage comparator 9. In the voltage comparator 9, a predetermined alarm threshold voltage signal TH2 is compared with the input voltage signal VS2, and the comparison result is issued as an alarm signal AR2.

As described above, according to the eighth embodiment, the linear amplifiers 13 and 7 are connected in series at the electric signal stage, and the values of the resistors 6, 8 and 12 are set appropriately. By doing so, it is possible to expand the dynamic range of the detection level. Accordingly, the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, so that it is possible to improve the versatility of the optical fiber amplifier without limiting the use place.

In the above-described fifth to seventh embodiments, the configuration in which the optical signal is branched into four is applied. However, the present invention is not limited to this.
Or five or more.

That is, in the case of the fifth embodiment, the number of branches may be variably set according to the number of output ports of the multi-branch optical star coupler. In the case of the sixth and seventh embodiments,
What is necessary is just to variably set the number of multistage connections of the two-branch optical coupler.

Further, in the above-described eighth embodiment, a case is shown in which two linear amplifiers are connected in series. However, the present invention is not limited to this, and the number of series connections is three or more. May be set.

[0082]

As described above, according to the present invention, an input current signal obtained by optical-to-electrical conversion of an optical signal is current-to-voltage converted and logarithmically amplified, and the voltage signal is amplified. A warning signal is issued according to the level, so the dynamic range of the detection level is expanded by a simple configuration, and this makes it possible to improve the versatility of the optical fiber amplifier without limiting the use place. An effect is obtained that a simple alarm monitoring device can be obtained.

According to the next invention, the high-level detection with low detection accuracy is compensated by linear amplification.
Regardless of the level of the detection level, the same high detection accuracy is always obtained, so that the optical fiber amplifier can be inserted into any place in the long-distance backbone optical transmission system. There is an effect that an alarm monitoring device capable of improving versatility in the above is obtained.

According to the next invention, the detection of the high level is attenuated to a level that can be linearly detected at the stage of the electric signal, so that the dynamic range of the detection level is expanded and the detection level is not affected. The same high detection accuracy is always obtained, which allows the optical fiber amplifier to be inserted anywhere in a long-distance backbone optical transmission system, thus improving the versatility of the optical fiber amplifier without limiting the use location There is an effect that an alarm monitoring device capable of performing the operation can be obtained.

According to the next invention, the level is logarithmically attenuated at the optical signal stage, and the logarithmic light level is detected as it is as a linear level. Therefore, the dynamic range of the detection level is expanded by a simple configuration. This allows the optical fiber amplifier to be inserted into any part of a long-distance backbone optical transmission system, thereby improving the versatility of the optical fiber amplifier in terms of not limiting its use location. There is an effect that a monitoring device can be obtained.

According to the next invention, the level detection according to the input light is performed by multi-branching at the optical signal stage and then performing linear amplification with different gains.
Since the dynamic range of the detection level is expanded and the detection accuracy is improved, the optical fiber amplifier can be inserted into any part of the long-distance backbone optical transmission system. An effect is obtained that an alarm monitoring device capable of improving the versatility of the present invention can be obtained.

According to the next invention, the optical signal is branched so as to have different levels at each stage, and the level detection corresponding to each input light is performed by linearly amplifying each optical signal. Since the dynamic range of the detection level is expanded and the detection accuracy is improved, the optical fiber amplifier can be inserted into any part of the long-distance backbone optical transmission system. An effect is obtained that an alarm monitoring device capable of improving the versatility of the present invention can be obtained.

According to the next invention, the optical signal is branched so as to have different levels at the stage, and the optical signal within the preset signal level range is linearly amplified to thereby make only one point. Since the level detection according to the input light is performed, the dynamic range of the detection level is expanded, and the detection accuracy is improved.
Thus, since the optical fiber amplifier can be inserted into any place of the long-distance backbone optical transmission system, an alarm monitoring device that can improve the versatility of the optical fiber amplifier without limiting the use place can be obtained. This has the effect.

According to the next invention, since the linear amplification is performed in multiple stages at the stage of the electric signal, the dynamic range of the detection level is expanded, whereby the optical fiber amplifier can be connected to a long-distance backbone optical transmission system. Since the optical fiber amplifier can be inserted into any place, an effect is obtained that an alarm monitoring device capable of improving the versatility of the optical fiber amplifier without limiting the use place can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an alarm monitoring circuit according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing an alarm monitoring circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing an alarm monitoring circuit according to Embodiment 3 of the present invention.

FIG. 4 is a block diagram showing an alarm monitoring circuit according to Embodiment 4 of the present invention.

FIG. 5 is a block diagram showing an alarm monitoring circuit according to a fifth embodiment of the present invention.

FIG. 6 is a block diagram showing an alarm monitoring circuit according to Embodiment 6 of the present invention.

FIG. 7 is a block diagram showing an alarm monitoring circuit according to a seventh embodiment of the present invention.

FIG. 8 is a block diagram showing an alarm monitoring circuit according to an eighth embodiment of the present invention.

FIG. 9 is a block diagram showing an alarm monitoring circuit according to a conventional example.

[Description of Signs] 1A to 1D 2-branch optical coupler, 2A to 2D photodiode, 3 log amplifier, 4, 4A to 4D, 9, 19
Voltage comparator, 5 voltage selector, 6, 8, 12, 12A ~
12D, 17 resistance, 7, 13, 13A to 13D, 18
Linear amplifier, 10 current selector, 14 optical attenuator,
15 Multi-branch optical coupler, 16 Multi-input current selector.

Claims (8)

[Claims] An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein an input current signal obtained by optical-to-electric conversion of an optical signal is subjected to current-voltage conversion to logarithmic linearity. Current-voltage conversion means for obtaining a voltage signal that has been amplified in advance, and alarm issuing means for issuing an alarm signal according to the level of the voltage signal obtained by the current-voltage conversion means. Alarm monitoring circuit for optical fiber amplifiers. 2. An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein an input current signal obtained by optical-to-electric conversion of an optical signal is subjected to current-voltage conversion to logarithmic linear. Current-voltage conversion means for obtaining a voltage signal which is amplified in a predetermined manner; level determination means for determining whether or not the level of the voltage signal obtained by the current-voltage conversion means is equal to or higher than a certain level; and When the determination result of the predetermined level or more is obtained, the voltage signal obtained by the current-voltage conversion unit is linearly amplified, and an alarm signal is issued according to the level of the voltage signal obtained by the linear amplification. (1) When a determination result of less than the predetermined level is obtained by the alarm issuing means and the level determination means, a warning is issued in accordance with the level of the voltage signal obtained by the current-voltage conversion means. Second to fire a signal
An alarm monitoring circuit for an optical fiber amplifier, comprising: an alarm issuing means. 3. An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein the level of an input current signal obtained by performing optical-to-electric conversion of an optical signal is not less than a certain level. And a current attenuating means for attenuating the input current signal at a constant rate in a logarithmic linear manner when the level determining means obtains a result equal to or higher than the certain level, and the current attenuating means. First alarm issuing means for performing a current-voltage conversion on the current signal attenuated by and then linearly amplifying and issuing an alarm signal in accordance with the level of the voltage signal; Is obtained, the input current signal is subjected to current-voltage conversion and then linearly amplified, and an alarm signal is issued according to the level of the voltage signal obtained by the linear amplification. An optical fiber amplifier alarm monitoring circuit, characterized by comprising 2 an alarm issuing means. 4. An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance trunk optical transmission system, wherein: an optical attenuator for attenuating an input optical signal in a logarithmic linear manner; and a light attenuated by the optical attenuator. An alarm monitoring circuit for an optical fiber amplifier, comprising: monitoring means for issuing an alarm signal in accordance with a signal monitoring state. 5. An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein: a multi-branch means for equally multi-branching an input optical signal; A plurality of light-to-electric conversion means for obtaining current signals by performing light-to-electric conversion on the respective light signals, and a plurality of current signals obtained by performing the current-to-voltage conversion on the plurality of current signals obtained by the plurality of light-to-electric conversion means are respectively different from each other. An alarm monitoring circuit for an optical fiber amplifier, comprising: a plurality of alarm issuing means for linearly amplifying a gain and issuing an alarm signal in accordance with the level of each voltage signal obtained by the linear amplification. 6. An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein the input optical signals are connected in series, each input optical signal is branched into two at different branching ratios, and one of them is provided in a subsequent stage. A plurality of two-branching means for outputting the other for monitoring and a plurality of lights for obtaining a current signal by optical-to-electrical conversion of each of the monitoring optical signals respectively branched by the plurality of two-branching means -Electrical conversion means, and a plurality of current signals obtained by the plurality of light-to-electric conversion means, respectively, current-voltage conversion and then linear amplification,
An alarm monitoring circuit for an optical fiber amplifier, comprising: a plurality of alarm issuing means for issuing an alarm signal according to the level of each voltage signal obtained by the linear amplification. 7. An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein the input optical signals are connected in series, each input optical signal is split into two at different splitting ratios, and one of the input optical signals is set at a later stage. A plurality of two-branching means for outputting the other for monitoring and a plurality of lights for obtaining a current signal by optical-to-electrical conversion of each of the monitoring optical signals respectively branched by the plurality of two-branching means -Electric conversion means; and selection means for selecting one current signal within a preset signal level range from among the plurality of current signals obtained by the plurality of light-electric conversion means; Means for current-voltage-converting the current signal selected by the means and then linearly amplifying the signal, and issuing an alarm signal in accordance with the level of the voltage signal obtained by the linear amplification. An optical fiber amplifier alarm monitoring circuit, characterized in that. 8. An alarm monitoring circuit for an optical fiber amplifier applied to a long-distance backbone optical transmission system, wherein an input current signal obtained by performing optical-to-electrical conversion of an optical signal is subjected to current-to-voltage conversion, and then linearized. A first alarm issuing means for amplifying and issuing an alarm signal in accordance with the level of the voltage signal obtained by the linear amplification, and a first alarm issuing means connected to the linear amplification output of the first alarm issuing means. The voltage signal obtained by the linear amplification is linearly amplified with a gain different from that of the first alarm issuing means,
A second alarm issuing means for issuing an alarm signal in accordance with the level of the voltage signal obtained by the linear amplification, and an alarm monitoring circuit for an optical fiber amplifier.