JPS6173032A - Photodetecting device - Google Patents

Abstract

PURPOSE:To easily detect light with unknown wavelength in a short time by splitting measured light to two optical paths, detecting the quantity of light from one optical path and the transmission wavelength peak of the light from the other optical path, and measuring and displaying both. CONSTITUTION:Light from an optical fiber 2 is made incident on a switching means 4. The switching means 4 moves up and down a mirror 6 which is slanted by, for example, 45 deg. periodically through a displacing mechanism 8 to split the light to the two optical paths. Then, the light of one optical path is inputted to, for example, an Si photodiode 10, etc., to detect the quantity of the light. Further, the light of the other optical path is made incident on a wavelength dispersing element 12 such as a plane diffraction grating. Then, the light dispersed according to the wavelength is incident on a position detecting element 14 to detect the wavelength. Then, the quantity of light detected by the photodetecting element 14 is corrected automatically with the wavelength obtained by the position detecting element 14. Therefore, the quantity of light is corrected automatically with the wavelength, so the light having unknown wavelength is easily detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a photodetection device applied to measuring the amount of light in an optical fiber.

(b) Prior art and its problems A light amount measuring device is used to measure transmission loss in optical fiber communications. The photodetection element installed in such a light amount measurement device, such as a Si photodiode or a Ge photodiode, has a wavelength dependence in photodetection sensitivity, so this must be compensated for in order to accurately measure the tip of the toe. There is a need.

Conventionally, in order to compensate for the wavelength sensitivity dependence of a photodetecting element, the measured light intensity value is corrected using the attached wavelength sensitivity curve of the photodetecting element, or the wavelength sensitivity curve is stored in memory in advance, and By manually setting the wavelength peak value, the measured light quantity is corrected based on the wavelength sensitivity curve stored in the memory. However, in order to perform such correction, it is necessary to know the transmission wavelength peak value of the light in advance or to separately measure the transmission wavelength peak value.

If the transmission wavelength peak is unknown, it cannot be corrected and the accuracy of the light intensity measurement value deteriorates, resulting in poor reliability of the data obtained. However, manually inputting the measured wavelength peak value into the apparatus takes time, and the measurement operation becomes complicated.

(C) [I] The present invention solves such problems in the conventional art, automatically compensates for the wavelength sensitivity characteristics of the photodetector, and makes it possible to measure and display both the light amount and the transmission wavelength peak at the same time. The purpose is to enable detection of unknown light easily and in a short time.

(iv) Structure In order to achieve the above-mentioned object, the present invention is provided with a switching means for switching the light to be measured into two optical paths, and (ii) a photodetecting element is provided on the one optical path switched by the switching means. , a wavelength dispersion element is placed on the other optical path, and
Further, a position detection element is provided at a condensing position of the dispersed light emitted from the wavelength dispersion element to constitute a photodetection device.

Therefore, the light to be measured is switched to two optical paths by the switching means,
The light intensity of one of the switched lights is measured using a photodetection element,
In parallel with this, the other light is dispersed according to its wavelength by a wavelength dispersion element, and its wavelength is detected by a position detection element. and,
The amount of light detected by the photodetector is corrected based on the wavelength detected by the position detector. As a result, the corrected light amount and the transmission wavelength peak are simultaneously measured.

(P) Examples The present invention will now be described in detail based on examples shown in the drawings.

FIG. 1 is a block diagram of the photodetector of this embodiment. The photodetector 1 includes a switching means 4 that switches the measured light emitted from the output end of the front fiber 2 into two optical paths. This switching means 4 includes a mirror 6 arranged at an angle of 45 degrees with respect to the incident optical path of the light to be measured, and a displacement mechanism 8 that periodically displaces the mirror 6 up and down in the figure. A photodetecting element I such as a Si photodiode or a Ge photodiode is placed on one optical path that is switched by the switching means 4.
A wavelength dispersion probe 12 such as a plane diffraction grating is disposed on the other optical path. Furthermore, a position detection element 14 such as a photodiode array is provided at a convergence position of the dispersed light emitted from the wavelength dispersion probe 12 according to the wavelength. In addition,! 6 is a collimating lens arranged between the optical fiber 2 and the switching means 4; I8;
is a condensing lens arranged between the wavelength dispersion probe I2 and the position detection element 14.

FIG. 2 is a block diagram of the photodetector I. In the figure, 20 is an input terminal for a light amount detection signal outputted from the photodetection element 1O, 22 is an input terminal for an apparatus detection signal composed of the position detection element 14, and 24 is a drive for the mirror 6 provided to the displacement mechanism 8. This is an input terminal that receives a signal or a human input. Further, 26 is a first detector that synchronously detects the light quantity detection signal with the drive signal, and 28 is a second detector that synchronously detects the position detection signal with the drive signal. 30 converts the synchronously detected position detection signal outputted from the second detector 28 into a wavelength detection signal, and transmits the converted wavelength detection signal to the position detection element 14.
32 is a memory in which the wavelength sensitivity curve of the photodetecting element lO as shown in FIG. A central control circuit that calculates the wavelength peak,
36 is a first display that displays the value of the amount of light calculated by the central control circuit 34; 38 is the value calculated by the central control circuit 34;
f-Suke Huge V-2/7'Il Old Lou Mi Jusu Flute 9 Lou Mo Yan 1 Puru.

In order to measure the three values of the light intensity and the wavelength peak of the light to be measured using this photodetecting device 1, first, a drive signal is applied to the displacement mechanism 8 of the switching means 4 to periodically displace the mirror 6. In this state, the light of the wavemeter 1111 emitted from the output end of the optical fiber 2 is converted into parallel light by the collimating lens 16 and is emitted toward the switching means 4. When the mirror 6 is away from the emitted light path, the emitted light to be measured continues straight and is received by the photodetecting element [0. When the mirror 6 is located on the emission optical path of the light to be measured, the light to be measured is reflected by the mirror 6 and directed toward the wavelength dispersion probe 12, which then emits the light at a constant angle according to its wavelength. distributed. This dispersed light is collected by a condensing lens 18 and focused on the position detection element 14 .

Drive signals applied to the displacement mechanism 8 for periodically displacing the mirror 6 are simultaneously input to the first and second detectors 26 and 28 via the input terminal 24, respectively. Further, when the photodetection element 10 receives the light to be measured, it outputs a light amount detection signal corresponding to dirt, and provides this light amount detection signal to the first detector 26 via the input terminal 20. Thereby, the first detector 26 synchronously detects the light amount detection signal with the drive signal, and sends the synchronously detected light amount detection signal to the central control circuit 34 .

On the other hand, when the position detection element 14 receives the measured light, it outputs a position detection signal corresponding to the position where the light was received, and provides this position detection signal to the second detector 28 via the input terminal 22. The second detector 28 synchronously detects the position detection signal with the drive signal, and transmits the synchronously detected position detection signal to the conversion circuit 3 of the next stage.
Send to 0.

Like the photodetector element 1O, the position detection element 14 has a certain wavelength sensitivity characteristic as shown by the solid line in FIG. 4, so the detected wavelength peak p1 is different from the wavelength peak p2 of the actual measured light. An apparent upward deviation Δ occurs. In order to correct this deviation Δ, the conversion circuit 30 stores a correction curve C as shown by the dashed line in the figure. Therefore, the position detection signal input to the conversion circuit 30 is first converted into a wavelength detection signal, and the wavelength detection signal is further corrected by the correction curve C to match the actual wavelength peak. be done. The corrected wavelength detection signal is then sent to the central control circuit 34. The central g11 circuit 3.1 calculates the corrected light amount based on the manually input wavelength detection signal, light amount detection signal, and the wavelength sensitivity curve of the photodetector IO stored in the memory 32, and displays the calculation result on the first display. Output to 36. Further, the wavelength peak value is calculated from the wavelength detection signal, and the calculation result is output to the second display 38. As a result, the amount of light to be measured is displayed on the first display 36, and the amount of light to be measured is displayed on the second display 36.
8, the wavelength peak value of the measured light is numerically displayed.

In this embodiment, a plane diffraction element is used as the wavelength dispersion element 12, but a concave diffraction element may be used instead. In that case, the condenser lens 18 can be omitted.

(f) Effects As described above, according to the present invention, the wavelength sensitivity characteristics of the photodetecting element can be automatically compensated, and both the light amount and the transmission wavelength peak can be measured and displayed simultaneously. Therefore, an excellent effect is achieved in that light of unknown wavelength can be detected easily and in a short time.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a block diagram of a photodetector, Fig. 2 is a block diagram of the same, Fig. 3 is a wavelength sensitivity characteristic diagram of a photodetector, and Fig. 4 is a position detection diagram. It is a wavelength characteristic diagram of an element. DESCRIPTION OF SYMBOLS 1..Photodetection device, 4..Switching means, 10..Photodetection element, 12.-Wavelength dispersion element, 14. Position detection element.

Claims (1)

[Claims] (1) A switching means is provided for switching the light to be measured into two optical paths, and a photodetecting element is arranged on one of the optical paths switched by the switching means, and a wavelength dispersion element is arranged on the other optical path. , and further comprising a position detection element provided at a condensing position of the dispersed light emitted from the wavelength dispersion element.