JP2862331B2 - Emission characteristics measurement method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emission characteristic measuring device for measuring a current-emission amount characteristic of a light emitting element such as a laser diode.

[Prior Art] FIGS. 3 and 4 show the characteristics of current versus light emission of a laser diode. In the figure, the horizontal axis _Ii represents the current value given to the light emitting element to be measured, and the vertical axis P represents the light emission amount of the light emitting element to be measured.

Emission amount P and from current I _i is This increases the boundary of current I _h in the light-emitting element such as a laser diode increases rapidly,
In the following I _h light emission amount P is small.

That lights above current I _h, is seen as a non-lighting state in the following I _h.

The reason why the current-light emission characteristic of the light emitting element is measured is as follows.

Light emitting elements such as laser diodes are used as light sources for optical modulators. Therefore, if the current-emission amount characteristic is curved as shown at point Q in the figure, the modulated light has indirect distortion and cannot be used as a light source of the modulator.

Therefore, the laser diode used as the optical modulator measures the current-light emission characteristic and determines whether or not the curved portion Q exists.

"Problem to be Solved by the Invention" In the current-emission amount characteristic of the laser diode, the curved portion Q has a relatively steep curve.

Therefore, to detect this curved portion Q, the measurement point P
Must be taken finely as shown in FIG. That is, when the measurement point P is roughly taken as shown in FIG. 3, the curved portion Q may be missed.

However, taking the measurement point P finely has a disadvantage that measurement takes time.

An object of the present invention is to propose a measurement method capable of measuring the current-light emission characteristic of a light-emitting element in a short time without overlooking the curve point Q by overcoming the contradictory conditions.

[Means for Solving the Problems] The light emission characteristic measuring method of the present invention supplies a measurement current of a magnitude specified for each measurement point, and measures an output light emission amount of a magnitude corresponding to the measurement current. A light-emitting characteristic measuring method for measuring a current-light emission amount characteristic of a diode to be measured, a boundary current value _Ih between a non-light-emitting region and a light-emitting region, a step value n of a measurement step width n · ΔI of the non-light-emitting region, The measurement step width ΔI of the light emitting area is input, and n is set in the non-light emitting area.
For each ΔI, while supplying the accumulated current to the measured diode, receiving data corresponding to the output light emission amount from the measured diode, and supplying the accumulated current to the measured diode for each ΔI in the light emitting region; The data corresponding to the output light emission amount from the diode to be measured is received, and the measured current and the output light emission amount corresponding to the measured current are output to the display means.

FIG. 1 shows an embodiment of the present invention. In this embodiment, in the region A where the light emitting element to be measured emits light, the interval between the measurement points P is taken at the boundary of the current value _Ih as a boundary, and in the non-light emitting region B, the interval between the measurement points P is n · ΔI The case where (n ≧ 2) is selected is shown.

Specifically, ΔI = 0.1 mA, n · ΔI = 2 mA, I _h = 70 mA,
When the maximum current I _{L is} 90 mA, the number of measurement points is 200 points in the light emitting area A and 35 points in the non-light emitting area B.

Therefore, according to the present invention, the total number of measurement points P is
235 points.

On the other hand, conventionally, the entire area of 0 to 90 mA is measured in steps of 0.1 mA, so that the number of measurement points P is 900 points.

For example, if the measurement time for one point is 20 ms, the conventional measurement method will be 900 × 20 ms = 18 seconds. On the other hand, according to the measuring method of the present invention, 235 × 20 ms = 4.7 seconds.

FIG. 2 shows the configuration of a measuring device that operates by the measuring method according to the present invention.

In the drawing, reference numeral 1 denotes a laser diode to be measured, 2 denotes a current source that supplies a current _Ii to the laser diode 1 to be measured, and 3 receives light 4 emitted from the diode 1 to be measured and converts the energy of the light 4 into an electric signal. 3 shows a light receiving element to be converted.

The light receiving element 3 outputs a current I _o corresponding to the energy of the light 4, converts this I _o into a voltage signal V by a current-voltage converter 5, and AD-converts the voltage signal V by an AD converter 6. Controller 7
To enter.

The controller 7 can be constituted by a microcomputer. As is well known, the microcomputer is a central processing unit CPU, a read-only memory ROM for storing a program for operating the central processing unit CPU in a predetermined order, and a memory RAM for temporarily storing data and the like.
And an input port INP and an output port OUP.

Numerical input means 8 is provided outside the AD converter 6 to the input port INP.
Is connected, and a boundary value I _h (expected value) between the light emitting area A and the non-light emitting area B of the laser diode 1 to be measured is input from the numerical value input means 8 and the step width of the measuring step P of the light emitting area A is defined. The current value ΔI to be measured and the n value for determining the measurement step width of the non-light emitting area B are input.

The central processing unit sets the measurement point P in the non-light emitting area B to n · in accordance with each set value inputted from the numerical value input means 8.
Outputs a control signal that varies in [Delta] I step from the output port OUP, a current I _i to be supplied to the test the laser diode 1 is changed in steps of n · [Delta] I giving the control signal to the current source 2.

When the current I _i to be supplied to the test laser diode 1 is equal to the boundary value I _h inputted from the numerical input means 8, either increases, the central processing unit CPU changes the step change in current I _i to [Delta] I, current Source 2 is controlled.

In this way, the non-illuminated area B is changed to change steps of the current I _i to be supplied to the laser diode 1 to be measured in the lighting area A, it is operated to take in close step change in the lighting area A.

Light 4 emitted from the laser diode 1 to be measured is received by the light receiving element 3, it is converted into a current I _o which corresponds to the energy of light 4. This current _Io is converted to a voltage signal by the current-voltage converter 5 and converted to a digital signal by the AD converter 6,
It is taken into the central processing unit CPU.

The measurement data taken into the central processing unit CPU is stored in the memory RAM, and is output from the output port OUP to the display 9.
Is output to display the values of the currents I _i that corresponds to the light emission amount. These numerical values can be printed by the printer 10 as needed.

[Effects of the Invention] As described above, according to the present invention, when the current-emission amount characteristic of the laser diode 1 is measured, the emission region A
Since the measurement step is taken densely and the measurement step is taken roughly in the non-light-emitting area B, the measurement time in the non-light-emitting area B can be shortened.

As a result, the current-emission amount characteristic of the laser diode can be measured efficiently, and it can be determined in a short time whether or not the laser diode can be used for the light source of the optical modulator. The advantage that inspection can be performed efficiently can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph for explaining a measuring method according to the present invention, FIG. 2 is a block diagram showing an example of a measuring apparatus for executing the measuring method according to the present invention, and FIGS. 3 and 4 illustrate conventional techniques. It is a graph for performing. A: light-emitting area, B: non-light-emitting area, P: measurement point, _Ih : boundary value.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01M 11/00 G01J 1/00 G01J 1/02 G01R 31/26

Claims (1)

(57) [Claims] 1. A measuring current having a magnitude designated for each measuring point is supplied, an output light emitting amount having a magnitude corresponding to the measured current is measured, and a current-light emitting characteristic of the diode to be measured is measured. in the light-emitting characteristic measurement method, specifying the demarcation current value I _h of the non-light-emitting region and the light emitting region, and the step value n of the measurement step width n · [Delta] I of the non-luminescent region, and a measurement step width [Delta] I of the light emitting region Supplying a measurement current to the diode to be measured every n · ΔI in the non-light-emitting area and for each ΔI in the light-emitting area, and receiving data corresponding to an output light emission amount from the diode to be measured. A method for measuring light emission characteristics, comprising outputting, to a display means, data corresponding to a current and a corresponding output light emission amount.