JP2002325037A - Light level monitor circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and surely realize a highly precise monitor. SOLUTION: When a photodiode 11 outputs currents based on the input of a light signal, the currents are converted into a voltage by a current/voltage converting circuit 12, and the voltage is amplified by two amplifiers 13 and 14 so as to be assigned to a low voltage band and a higher voltage band. A CPU 15 is incorporated with a judging part 17 for monitoring the data of two A/D converters 16a and 16b. When a low voltage band A and a high voltage band B are inputted from the amplifiers 13 and 14 through the A/D converters 16a and 16b, the determination part 17 determines which of the low voltage band A voltage data and the high voltage band B voltage data are normal data. Then, the normal voltage data are selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical level monitor circuit, and more particularly to an optical level monitor circuit suitable for use in an optical transmission system.

[0002]

2. Description of the Related Art In an optical transmission system, it is necessary to widen a detection range of a monitor light from a small value to a large value, and it is necessary to perform monitoring with high accuracy in accordance with the magnitude of the detection light. Therefore, as shown in FIG. 3, the conventional optical level monitor circuit includes a photodiode 1, a current / voltage conversion circuit 2, a high-precision AD converter (high-precision AD converter) 3, and a central processing unit (CPU) 4. It is provided with. Then, when the photodiode 1 outputs a current according to the input light, the current / voltage conversion circuit 2 converts the voltage based on the current, and the voltage is converted as data by the high-precision AD converter 3, whereby the data is converted. The data is monitored by the CPU 4 as a monitor value.

[0003]

The conventional optical level monitor circuit shown in FIG. 3 uses the high-precision AD converter 3, so that the input light can be monitored as data with high accuracy. It can be easily configured.

However, since the high-precision AD converter 3 is expensive, not only is the cost of the whole apparatus considerably high, but also the high-precision AD converter 3 itself has a long delivery time and cannot be easily obtained. There was a defect.

An object of the present invention is to provide an optical level monitor circuit capable of reliably and inexpensively realizing a high-precision monitor in view of the above circumstances.

[0006]

Means for Solving the Problems To solve the above problems, the present invention employs the following means. According to the present invention, a photoelectric conversion element that outputs an electric signal based on an input of an optical signal, a conversion circuit that converts the electric signal from the photoelectric conversion element into a voltage, and converts the converted voltage into a low voltage band and a high voltage higher than the low voltage band. A low-voltage amplifier and a high-voltage amplifier, which amplify the voltage by dividing the voltage into a voltage band and an A
A central processing unit having a built-in D converter, wherein the central processing unit includes a low-voltage band data obtained from the low-voltage amplifier and a high-voltage band obtained from the high-voltage amplifier. And monitoring the selected voltage data.

As described above, the low voltage band and the high voltage amplifier are divided into the low voltage band and the high voltage band.
The D converter converts the data as voltage data to monitor the optical signal, and the central processing unit selects the voltage data for each of the allocated voltage bands, so that even a low voltage requiring high accuracy is clear. As a result, the optical signal can be monitored as data over a wide range and with high accuracy. Therefore, a high-precision A / D converter as in the prior art is not required, and a normal A / D converter built in the central processing unit can be used. It can be manufactured at low cost.

[0008]

FIG. 1 is a block diagram showing an embodiment of the present invention.
A description will be given based on FIG. 1 and 2 show an embodiment of a light level monitor circuit according to the present invention. As shown in FIG. 1, the optical level monitor circuit includes a photodiode 11 as a photoelectric conversion element, a current / voltage conversion circuit 12, two amplifiers (AMPs) 13 and 14, a central processing unit (hereinafter, referred to as a central processing unit). CPU 15).

When the photodiode 11 outputs a current based on the input of the optical signal, the current is converted into a voltage by the current / voltage conversion circuit 12 and the voltage is reduced by the two amplifiers 13 and 14 to a low voltage. The signal is amplified by being divided into a band A and a higher voltage band B larger than the band A. In this case, for example, as shown in FIG. 2, one amplifier 13 takes in only a low voltage in the range between V0 and V1 and amplifies and outputs the same. The other amplifier 14 outputs a voltage (V1) in a larger range. To V2), and outputs the amplified signal. Therefore, these amplifiers 13 and 14 take in the voltage from the current / voltage conversion circuit 12 for each voltage band and amplify it. FIG. 2 is an optical monitor graph showing a voltage band by each of the amplifiers 13 and 14.

The voltage in the low voltage band A output from one amplifier 13 and the voltage in the high voltage band B output from the other amplifier 14 are output to the CPU 15 as they are. The CPU 15 incorporates AD converters (AD converters) 16a and 16b on the input side. The CPU 15 converts the voltage input from the amplifier 13 by the AD converter 16a and outputs the voltage input from the amplifier 14. AD
The conversion is performed by the converter 16b, so that each of them is monitored as voltage data.

That is, in this embodiment, the amplifier 1
3, 14 and the AD converter 1 built in the CPU 15
By using 6a and 16b, input light can be converted as data. Such AD converters 16a and 16b may be general ones built in the CPU 15.

The CPU 15 has a built-in judging unit 17 for monitoring data of the two AD converters 16a and 16b. When the low-voltage band A and the high-voltage band B are input from the two amplifiers 13 and 14 via the AD converters 16a and 16b, the determination unit 17 determines the voltage data of the low-voltage band A and the high-voltage band. By determining which of the B voltage data is legitimate data, the legitimate voltage data is selected.

The optical level monitor circuit configured as described above, when an optical signal is input to the photodiode 11,
The voltage is divided into two voltage bands A and B by the amplifiers 13 and 14 from the photodiode 11 via the current / voltage conversion circuit 12 and amplified. When the divided and amplified voltage bands A and B are output to the CPU 15, the respective voltages are applied to the AD converter 16 in the CPU 15.
The CPU 15 monitors the optical signal by being converted as voltage data by the signals a and 16b. In this case, C
The judging unit 17 of the PU 15 judges which of the voltage data of the respective voltage bands A and B is correct and selects it, so that the selected voltage data is monitored as an optical signal.

As described above, the amplifiers 13 and 14 distribute the voltage into the low voltage band A and the high voltage band B, respectively, and the AD converters 16a and 16b in the CPU 15 convert the voltages in the voltage bands A and B as voltage data. By doing so, the optical signal is monitored, and the determination unit 17 of the CPU 15 selects the voltage data for each of the divided voltage bands A and B, so that even a low voltage requiring high accuracy is clearly monitored. As a result, the resolution of the same bit is improved, so that the optical signal can be monitored as data over a wide range and with high accuracy.

Therefore, a high-precision A
Since the D converter 3 is not required, and the ordinary AD converters 16a and 16b built in the CPU 15 are sufficient, it is possible to suppress an increase in the cost of the entire apparatus and to manufacture the apparatus at low cost.

When the low-voltage band A is amplified by the amplifier 13, it is possible to accurately monitor not only a case where a very weak optical signal is input but also a case where an optical signal having a steep rise is input. Reliability can be improved.

Further, when the low voltage band A and the high voltage band B are divided by the amplifiers 13 and 14, the low voltage band A
Is amplified to increase its value to the high voltage band B.
In some cases. However, in such a case, the determination unit 17 of the CPU 15
Since a and 16b are constantly monitored and selected from both voltage data, good monitoring can be maintained even if the voltage in the low voltage band A becomes large enough to overlap the high voltage band B.

[0018]

As described above, according to the present invention, the optical signal is divided into a low-voltage band and a high-voltage band based on the optical signal, and the optical signal is monitored by the central processing unit selecting it. Therefore, the optical signal can be monitored as data in a wide range and with high accuracy, and the optical signal can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a light level monitor circuit according to the present invention.

FIG. 2 is an optical monitor graph showing a voltage band by an amplifier.

FIG. 3 is a configuration diagram showing a conventional optical level monitor circuit.

[Explanation of symbols]

 Reference Signs List 11 Photodiode as photoelectric conversion element 12 Current / voltage conversion circuit 13, 14 Amplifier (AMP) 15 Central processing unit (CPU) 16a, 16b A / D converter (A / D converter) 17 Judgment unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/14 10/26 10/28

Claims (1)

[Claims] 1. A photoelectric conversion element for outputting an electric signal based on an input of an optical signal, a conversion circuit for converting an electric signal from the photoelectric conversion element into a voltage, and converting the converted voltage into a low voltage band and higher. It has a low-voltage and high-voltage amplifier that amplifies by distributing and amplifying each voltage band to a high-voltage band, and a central processing unit with a built-in AD converter in the input unit.
The central processing unit selects and monitors the low-voltage band voltage data obtained from the low-voltage amplifier and the high-voltage band voltage data obtained from the high-voltage amplifier. Light level monitor circuit.