JPS59147273A - Quantity of electricity measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a large S/N ratio by composing a subtractor and an adder of an optical branch and a photodiode to offset base components of light signals therebetween. CONSTITUTION:Light from a light source 10 is applied to an optical sensor 20 to be modulated according to the quantity of electricity E to be measured, resolved into specific bidirectional polarized components intersecting each other with a photo detector 24 and then, transmitted to optical branches 71 and 72 through optical fibers 25 and 26. Signals entering photo diodes 81 and 82 undergoes a subtraction and outputted as signal proportional to the voltage E to be measured from an output terminal 60 through an amplifier 91. On the other hand, signals entering photo diodes 83 and 84 are subjected to an addition computation and inputted into an arithmetic amplifier 93 together with a reference voltage 94 to control light output of the light source 10 to a fixed value thereby stabilizing a signal fetched from the output terminal 60.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric Φ measurement device that utilizes polarization of light.

A conventional example of this type of device is shown in Figure 1. J go to the diagram,
10 is a light source made of a laser diode or a light emitting diode, 20 is a known optical sensor configured using an electro-optic effect element (or magneto-optic effect element), 31 and 32 are photodiodes, and 41° and 42 are current/voltage conversion functions. 51 is a subtracter, 52 is an adder, 60 is an output node
It is a terminal.

The constant optical power output from the light source 10 is the optical fiber 11.
is inputted to the lenser 20 via 〉. Photo Cui Δ
The output of -1' 31 is connected to a subtracter 51 and an adder 52 via an amplifier 41, and the output of the photodiode 32 is connected to a subtracter 51 and an adder 52 via an amplifier 42. In the device with this configuration a5, the output of the light source 10 is applied to the single-width photon 21 and the λ/4 plate 22 in the optical sensor 20, so that the light beam that becomes circularly polarized passes through the electro-optic effect element 23. The light undergoes a phase change proportional to the value of the voltage E to be measured, and becomes elliptically polarized light.

As a result, by passing through the analyzer 24, the light is decomposed into polarization components in two specific orthogonal directions, and the photoquote 31
．． 32. Therefore, p.

If /2 is the light intensity and S is the signal modulated by the optical sensor 2o, then the photoquote 31 is P.

The photoquote 32 outputs a signal represented by /2X (1→~S), and the photoquote 32 outputs a signal represented by Po /2x (1-8). The output of the photodiode 31 is applied to a subtracter 51 and an adder 52 via an amplifier 41, and the output of the photodiode 32 is applied to a subtracter 5 via an amplifier 42.
1 and the caulking device 52. As a result, the output of the subtracter 51 becomes PoS, and the output of the adder 52 becomes PO. P
The oS signal represents a voltage value proportional to a signal modulated according to the value of the electricity ff1E to be measured, and this voltage is taken out from the output terminal 60 and measured. On the other hand, the po signal is proportional to the light intensity, and this signal is given to the light source 10.
The output light of 0 is set to a constant value.

A device with such a configuration has already been proposed and proposed by the applicant as a highly stable device, but the photodiode 3
Since the output of 1.32 is directly given to the amplifier 41.42, if the degree of modulation at the optical sensor 20 is low, the amplifier 41.42 is sufficient for the pace component included in the output of the photodiode 31.32. It had the disadvantage that it was not possible to obtain a large SZN ratio. The present invention has been made to improve these drawbacks, and an embodiment thereof is shown in FIG. In FIG. 2, parts having the same configuration as in FIG. 1 are designated by the same reference numerals as in FIG. 1, and a redundant explanation thereof will be omitted. In FIG. 2, 83 and 100 are optical arithmetic circuits. In the circuit 100, 71.72 is an optical branch circuit, 8
1 to 84 are photodiodes. Reference numerals 91 and 92 are amplifiers having a large voltage/current conversion function, 93 is an operational amplifier, and 94 is a reference voltage source. The two polarized light components obtained from the optical sensor 20 described above are respectively connected to the optical fiber 2.
5.26, one is input to the optical splitter 71, and the other is input to the optical splitter 72. Photodio-1-81
and 82 are connected in parallel with opposite polarities to form a photoneutralizer 85. Photodiodes 83 and 84 have the same polarity and are connected in parallel to form an optical adder 86. The optical range calculator 85 is placed opposite the optical splitter 71 , and the optical adder 86 is placed opposite the optical splitter 72 . The optical splitter 71 divides the light from the optical sensor 20 into 1=1
Or, the branched light is split at a ratio of 1:11 (+1 is an arbitrary integer), and one of the branched lights is sent to the photodiode 81 that makes up the optical range calculator 85, and the other light is sent to the photodiode 84 that makes up the optical adder 86. It is incident. The optical splitter 72 also serves as the optical sensor 20.
One of the branched lights is incident on the photodiode 82 and the other is incident on the photodiode 83. The output of the optical range calculator 85 is connected to the output terminal 60 via an amplifier 91. The output of the optical adder 86 is connected to the light source 10 via a series circuit of an amplifier 92 and an operational amplifier 93. The operation of the device having such a configuration will be explained as follows.

Light from the light source 10 is applied to the optical sensor 20 and is modulated in accordance with the measured electricity @E as explained in FIG.

The modulation signal is as explained in Fig. 1<P/2X (1-
8), P/2x (1+S), and this signal is transmitted via an optical fiber 25.26 to an optical splitter 71.72. Of the lights branched 1:1 or 1:n by the optical splitter 71, one enters the photodiode 81 and the other enters the photodiode 84. Also, 1 in the optical splitter 72:
Of the lights branched at 1 or 1:n, one enters the photodiode 82 and the other (the other) enters the photodiode 83. The signals entered into the photodiodes 81 and 82 are subtracted. For example, the light When the splitter 71 branches at a ratio of 1:1, the subtracter 85 calculates P/4x (1+5) - P/4x (1+5) = P/2XS.The result of this calculation is proportional to the voltage E to be measured. The voltage signal is converted into a voltage signal through the amplifier 91 and taken out from the output terminal 60.

On the other hand, the signals incident on the photodiodes 83 and 84 are subjected to an addition operation. In this case as well, if the branching ratio in the optical splitter 72 is selected to be 1:1, the adder 86 will perform the calculation P,/4x (1+8> ten P/4X (1-8) = P,/2. A light intensity signal is obtained. This light intensity signal is fed back to the light source 10 via an operational amplifier 93. A reference voltage 94 is applied to the operational amplifier 10, and as a result, the light output of the light source 10 is It is controlled to a constant value.Thereby, the signal taken out from the output terminal 60 is stabilized.

In this way, in the device of the present invention, since the optical range adder 85 and the optical adder 86 are each constructed of an optical splitter and a photodiode, the base portions of the optical signals taken out from the subtracter cancel each other out. As a result, even signal components with a low degree of modulation can be sufficiently amplified by the amplifier, and an apparatus can be realized that can obtain a signal with a much larger S/N ratio than the apparatus shown in FIG.

In addition, in FIG. 2, an example is explained in which the voltage E is measured using an electro-optic effect element as the optical hinter 20, but if a magneto-optic effect element is used instead of the electro-optic effect element 23, the current can be measured. can be measured. Furthermore, if an electro-optic effect element and a magneto-optic effect element are used together, it becomes possible to measure electric power.

FIG. 3 is a circuit diagram of another embodiment of the present invention.

In FIG. 1, it is necessary to correct for loss in an optical connector (not shown) provided in the device and variations in sensitivity of the photodiode. In FIG. 3, optical attenuators 73 to 76 perform the correction, and are provided between the optical splitters 71 and 72 and each photodiode. Note that the other parts are the same as those in FIG. 1, so explanations will be omitted.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional device, and FIGS. 2 and 3 are circuit diagrams of an embodiment of the present invention. 10... Light source, 20... Light sensor, 71, 72.
... Optical splitter, 85 ... Subtractor, 86 ... Adder,
60...Output terminal.

Claims (1)

[Claims] The light from the light source is modulated by the optical sensor according to the amount of electricity to be measured, 11t1, and then divided into two polarized components, and the output of the light source is controlled to a constant value by the sum signal of both polarized components. What is claimed is: 1. An electric power measuring device that uses a subtracted signal of a polarized light component as an electric signal of the electric current m to be measured, characterized in that an operator circuit for performing the addition and subtraction is constructed using an optical splitter and a photodiode.