JPS60207073A - Optical power measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to accurately measure power by excluding loss by light transmission, by allowing same light output to be incident to a polarizer and a light detector so as to allow the same to advance through a light path to mutually opposite directions and calculating the difference of mutual light receiving outputs in opposite directions. CONSTITUTION:Light from a light emitting diode 11 is incident to a polarizer through a half mirror 12 and an optical fiber 13 and receives the rotation in a polarization direction by the Faraday effect of a magneto-optical effect element 4 and further receives the change in a phase proportional to applied valtage V by an electrooptical effect element 5 to be converted to an oval polarized wave. This light passes through an 1/4 wavelength plate 6, a light detector 7, an optical fiber 14 and a half mirror 15 to be received by a photodiode 16. The light from the light emitting diode 17 is incident to the half mirror 15 and the reflected light of the half mirror 12 is received by a photodiode 18. Then, outputs of the photodiodes 16, 18 are inputted to a differential amplifier 20 and difference voltage is outputted as a power signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Application This invention relates to an optical power measuring device that measures power using light.

(B) Background Art A device with ambiguous sensitivity has been proposed by the present applicant as a device for optically measuring power. FIG. 1 shows this device, and reference numeral 1 denotes a light emitting diode. Output light from the light emitting diode 1 is incident on a lens 2, condensed, and incident on a polarizer. The linearly polarized light that has passed through the polarizer 6 is processed by a magneto-optic effect element (Faraday element).
4, the direction of polarization rotates due to the Faraday effect. Furthermore, when the rotated linearly polarized wave is passed through a vertical electro-optic effect element (Pockels element) 5 to which voltage ■ is applied, the applied voltage V is caused by the Pockels effect.
It changes into elliptical polarization due to a change in phase compared to tlJ.

By further passing the resulting light through a wave plate 6, it is corrected so as to obtain good linearity with respect to the power to be measured. Furthermore, the light output from '/1 wavelength &6 passes through an analyzer 7 installed at the 10,000 position to the 10,000 position of the polarizer 6, passes through a lens 8, and is received by a photodiode 9. It will be done.

In the device described above, the light is received by the photodiode 9. If the average received light output is PO, then the light output P received by the photodiode 9 is given by the following equation.

P=P9/2 (1+5 ink, V-sink2V) −
(1) Here, , k2 is the magneto-optic effect element 4. This is a constant determined by the cut, length, thickness, etc. of the crystal of the electro-optic effect element 5.

11) Nii Oiteni, V<<”/, , k2I((”
/,])jA combination OP=-4(1+, V, -2I)'-(2). That is, the optical output P is the sum of the voltage (2) and the current (I) centered on P, O/2, that is, an output proportional to the electric power is obtained.

(c) Problem The optical output P received by the photodiode 9 is the effective power of voltage ■ and current ■ obtained as a DC signal, so if an optical fiber is used as a transmission path, for example, the effective power and transmission loss Both of these signals are obtained as DC signals, and there is a problem in that it is not possible to distinguish the changes between the two.

B) Purpose This invention was made based on the above circumstances, and its purpose is to provide an optical power measuring device that can eliminate p loss and measure accurate power by optical transmission. be.

(Embodiment) Hereinafter, an embodiment of the present invention will be explained based on FIG. 2. In FIG. 2, the same parts as in FIG. In Figure 2,
The light emitted from the light emitting diode 11 enters the half mirror 12, and the light transmitted through the half mirror 12 is transmitted through the optical fiber 15.
The light passes through the polarizer and enters the polarizer. The light emitted from the polarizer 6 is the magneto-optic effect element 4.1! Air optic effect element 5. After sequentially passing through the signature wavelength plate 6° analyzer 7 as described above, the light enters the optical fiber 14. The output light that has passed through this optical fiber 14 enters the half mirror 15, and this half mirror
150 reflected light is received by the first diode 16. - 10,000, - Light-emitting diode 1 on mirror 15
The light emitted from the light emitting diode 17 having the same light output as that of the optical fiber 14. Analyzer 7,1
4 wavelength plate6. Electro-optic effect element 5. Magneto-optic effect element 4
．． The light passes through the polarizer filter and the optical fiber 13 in order.
7 mirror 12. This half mirror 120 reflected light is received by the photodiode 18.

The anode of the photodiode 16 is grounded and connected to a cathode via a resistor 19, and the cathode is connected to a differential amplifier 20 constituted by an operational amplifier.
is connected to the positive input terminal of the - 10,000, the anode of the photodiode 18 is grounded and the resistor 19
It is connected to the cathode via a resistor 21 which is in the same line as , and this cathode is further connected to the negative input terminal of the differential amplifier 20 . The differential amplifier 20 amplifies the difference in voltages applied to its inner input terminals and outputs it as a component signal.

Thus, when the light emitted from the light emitting diode 11 passes through the magneto-optic effect element 4 in the X direction in FIG. undergoes a proportional phase change.

Average light received by this photodiode 16 f: ;? ';l 1. When it is set to '0', this received light power is 13. is P, = ”/ (1+sin k, V
−sin k2I) −(31) The received light power P of the photodiode 16 is applied as a considerable voltage to the positive input terminal of the differential amplifier 20 via the resistor 19. When the output light passes through the magneto-optic effect element 4 in the Y direction in FIG. Since the light is the same as the light in the X direction, it undergoes a phase change proportional to the collective voltage ■.
-sink2V) -(4). Further, the light-receiving puff P2 of the photodiode 18 is applied as a considerable amount of voltage to the negative input terminal of the differential amplifier 20 via the resistor 21.

The differential amplifier 20 calculates the difference in manually applied voltage, that is, P - P
:= Po'5ink V-5ink 2L -(5)
is amplified and output as a power signal. (5) is converted into (31
, (4), the term p*/ is canceled, and the obtained power signal is directly the product of voltage ■ and current ■. Here, since the light emitted from the light emitting diodes 11 and 17 travels in the same optical path in opposite directions as described above, the respective transmission losses of both the light emitting diodes 11 and 17 are the same. Therefore, equation (5), which is the difference between equations (3+ and +4), does not include optical transmission loss, and a power signal proportional only to the effective power is obtained.

In the above embodiment, the electro-optic effect element 5 is vertical, but it may also be horizontal, which is reciprocal to light, or the arrangement order of the magneto-optic effect element 4 and the electro-optic effect element 5 may be alternated. It's okay.

Furthermore, the positions of the polarizer 5 and the analyzer 7 can also be interchanged.

Also, an avalanche photodiode may be used in place of the light emitting diodes 11 and 17.

(to) Effect As explained above, according to the present invention, there is provided a polarizer.

A magneto-optic effect element, an electro-optic effect element, a '/4 wavelength plate, and an analyzer are arranged to form an optical path passing through them,
a light output means for inputting the same light output to the polarizer and the analyzer so as to travel in opposite directions on the optical path;
The present invention includes a light detection means for detecting the light outputs from the detector and the polarizer, respectively, and a means for calculating the difference between the mutually received light outputs in the opposite directions detected by the detection means and outputting a power signal. It is possible to accurately measure power in degrees Celsius without being affected by losses associated with optical transmission. Therefore, the reliability of power measurement using light is improved, and it can be suitably used in an integrated power meter, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram for pointing out problems with the optical power measuring device, and FIG. 2 is a block diagram showing a modification 911 of the present invention. 5... Polarizer 4... Magneto-optic effect element 5... Electro-optic effect element 6... 1/l
Wave plate 7...Analyzer 11.17...Light emitting diode 12.15...Half mirror 1, 14...Optical fiber 16.18...-Photodiode 19.21... ...Resistance 20...
...Differential amplifier patent applicant Sumitomo Electric Industries, Ltd. t-□- Figure 1 Figure 2

Claims (1)

[Claims] ([) A polarizer, a magneto-optic effect element, T11; an air-optic effect element, a long plate and an analyzer are arranged to form an optical path passing through them, and the Faraday effect and Pockels In an optical power measurement device that measures power by simultaneous effects, the light output means inputs the same light output to the polarizer and the analyzer so that the light path travels in mutually opposite directions; , a light detection means for detecting the light outputs from the analyzer and the polarizer, respectively, and a means for outputting a power signal by calculating the difference between the mutually received light outputs in the opposite directions detected by the light detection means. Optical power measurement device. (2) The light output means is a light emitting diode, a no-half mirror, and an original fiber, the light detection means is the half mirror and a photodiode, and the power signal output means is a differential amplifier. An optical power measurement device according to claim (1).