JPH05203491A - Light power meter - Google Patents

Abstract

PURPOSE:To enable easily indicating the stability of light power in real time by calculating the maximum, minimum and the standard deviation values from the digital measurement signals of the number specified by a window frame setter. CONSTITUTION:A measured signal S3 is converted 5 to a digital value P(i) and stored in a memory 7. Then, a certain number K of measured values going back from the latest contained digital value specified by a window frame setter 11 are read out of the memory 7. An arithmetic part 9 calculates from the K measured values, the maximum, minimum and standard deviation values indicating the stability of the light power of the received light and indicates at least one of them on an indicator 13. By this, the stability of the light power can be known in real time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical power meter having a function of determining whether or not the optical power of an object to be measured is stable.

[0002]

2. Description of the Related Art With the practical use of optical communication, optical measuring instruments that can easily measure the power of irradiated light (for example, laser light) have become widespread. In order to check whether such an optical measuring device measures the optical power correctly, it is necessary to calibrate it regularly. Calibration of the optical measuring device is performed as follows. First, light with stable output power is emitted from a light source, and this is measured with an extremely high-precision optical power meter (such a device is, for example, Japanese Patent Application No. 1-138347). Next, the direction of the light from the light source is switched to irradiate the optical measuring device to be calibrated, and the measured value is adjusted to be the same as the indicated value of the optical power meter.

In order to perform the above-mentioned calibration, it is premised that the optical power applied to the optical power meter is the same as the optical power applied to the optical measuring instrument to be calibrated, and therefore it is used. The output light of the light source requires extremely high stability. On the other hand, in many cases, the semiconductor laser light source used in the above cases takes time for the output light to stabilize after the power is turned on, and depending on the required stability, warm-up for several hours is required. Is.

Therefore, when high stability is required for calibration of the optical measuring instrument, it is necessary to confirm whether or not the output light of the light source has reached the desired stability. The stability is confirmed as follows. The optical power meter has a terminal for outputting a digital value (which may output an analog value) indicating the value of the measured optical power to the outside. A personal computer or a recorder is connected to this using this output terminal. Then, the measured change in the output light of the light source was displayed on the display of a personal computer or a recorder, and the stability was confirmed from the transition of the measured value. Figure 3
Is an example of data showing the temporal change of the output light of a certain light source. Then, after confirming that the output light of the light source has reached the desired stability, this light is alternately irradiated to the optical power meter and the optical measuring instrument to perform the calibration operation.

[0005]

As described above, in the prior art, in order to check the stability of the light output of the light source, external equipment such as a personal computer and a recorder is required,
It was not possible to measure easily.

An object of the present invention is to provide an optical power meter capable of displaying stability in real time by processing the measured value of the optical power which changes every moment.

[0007]

According to the present invention, there is provided a measuring device having a light receiving section for receiving a light beam and a measuring circuit section for outputting a signal (S3) according to the optical power applied to the light receiving section. , An AD converter for converting the measurement signal (S3) into a digital value P (i), a memory means for successively storing the digital values P (i) output by the AD converter, and a memory means for storing the memory value in the memory means. From the digital value P (i) stored in the window frame setter that specifies how many time-series consecutive digital values are to be taken out, and the digital value P (M) stored most recently is the starting point. The number of digital values (K) specified by the window frame setting device stored earlier is read from the memory means, and from the read digital value, the maximum digital value, the minimum digital value, The calculation unit that calculates the calculated value of the standard deviation and the maximum value obtained by this calculation unit. Digital value of the value,
At least one of the minimum digital value and standard deviation calculation value
And an indicator for displaying one.

[0008]

The operation unit reads K measurement values (digital values) designated by the window frame setting unit from the memory. Since the K digital values are K measured values traced back from the most recently stored digital value, the K digital values always mean the latest K measured values. To do. The calculation unit calculates the maximum value, the minimum value, and the standard deviation calculation value indicating the stability of the optical power of the received light from the K measured values. You can know the stability.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a configuration example of an optical power meter according to the present invention, FIG. 2 is a diagram showing a relation between a temporal transition of optical power and a "window", and FIG. It is a figure which shows the relationship of.

In FIG. 1, reference numeral 1 denotes a light receiving portion, which receives a light beam. The light receiving unit 1 can be composed of, for example, the following elements (not shown). That is, the light beam of the target is directly irradiated and the temperature rises according to the light power, the temperature reference jacket which is arranged close to the light absorber and is at a constant temperature, and the temperature reference jacket. On the other hand, a cooling element that constantly cools the light absorber, a heater that is embedded in the light absorber to heat the light absorber, and a temperature detector that outputs a signal according to the temperature difference between the temperature reference jacket and the light absorber. Composed of elements.

Reference numeral 3 denotes a measuring circuit section for introducing a signal S1 indicating a temperature difference introduced from a temperature detecting element and adding a feedback signal S2 to the heater so that the temperature difference becomes zero. That is, the temperatures of the light absorber and the temperature reference jacket are controlled to be equal. As a result, the optical power of the light beam can be measured.

The reason why measurement is possible will be described. It is assumed that the cooling action from the cooling element can be canceled by passing the heating current i1 through the heater in the state where the light beam is not irradiated. That is, it is assumed that when the heating current of the heater is i1, the temperatures of the light absorber and the temperature reference jacket are equal. When a light beam is irradiated in such a thermal equilibrium state, the light absorber is additionally heated by the amount of light power, so that the temperature of the light absorber rises with respect to the temperature reference jacket. Therefore, the measurement circuit unit 3 reduces the current i1 applied to the heater and controls so that the temperatures of the light absorber and the temperature reference jacket become equal. That is, the amount of decrease in heater current Δ _i
The optical power can be measured because there is a certain relationship between the optical power and the optical power.

The light receiving section 1 and the measuring circuit section 3 described above are known ones, for example, Japanese Patent Application No. 01-1383.
It is described in detail in Japanese Patent Publication No. 47, "Isothermal control calorimeter". The light receiving section 1 and the measuring circuit section 3 used in the present application
The configuration of is not limited to the configuration described in detail above, and the light receiving unit 1 that receives a light beam and the measurement circuit unit 3 that outputs a signal (S3) according to the optical power applied to the light receiving unit 1 That's enough.

An AD converter 5 converts the optical power measurement signal S3 into a digital value P (i). The measurement circuit unit 3 continuously outputs the measured value (analog value) of the optical power, but the AD converter 5 takes in this measured value at a certain sampling period, converts it into a digital signal, and outputs it. .. A memory 7 stores the digital values P (i) output from the AD converter 5 one after another.

Reference numeral 9 denotes a calculation unit, which has a maximum value search calculation function, a minimum value search calculation function, a standard deviation calculation function, and an average value calculation function. The calculation unit 9 reads the measured value data, which is the basis for performing these calculations, from the memory 7. Number of measured value data read from memory 7 K
Is the number specified by the window frame setting unit 11 described later.
Then, starting from the digital value P (M) most recently stored in the memory 7, the K digital values stored before this are read from the memory 7, and the maximum value is read from the read digital value. The digital value, the minimum digital value, the standard deviation calculated value, and the average value are calculated.

Reference numeral 11 denotes a window frame setting device, which specifies how many of the digital values P (i) stored in the memory 7 should be taken out in time series. Of course, the setting of numerical values to this window frame setting device 11 is of course not possible with FIG.
The operator of the device. Reference numeral 13 is a display unit, which is a calculation unit
Digital value of maximum value, digital value of minimum value obtained in
At least one of the calculated standard deviations is displayed. Usually, the measured optical power value is displayed in addition to these calculated values.

The operation of the apparatus of FIG. 1 configured as described above will be described with reference to FIGS. FIG. 3 is an example in which the optical power is measured every 4 minutes immediately after the light source (not shown) is turned on (unit: μW). Assuming that the required output stability of the light source is “standard deviation per 20 minutes is 0.1 μW or less”, the standard deviation of the optical power measured 5 times at 20 minutes / 4 minutes may be obtained. In this case, the memory 7 requires at least 5 data, and P (i-4) to P (i) at the i-th measurement
The maximum value Pa (i) is P (i-4), P (i-3), P (i-2), P (i-
1) Maximum value of P (i) Minimum value Pi (i) is P (i-4), P (i-3), P (i-2), P (i-
1), the minimum standard deviation σ (i) of P (i) is σ (, where α (i) is the average value of the five measurements from P (i-4) to P (i). i) = {[{P (i-4) -α (i)} ² + {P (i-3) -α (i)} ² +… + {P (i) -α (i)} ² ] / 4} ^1/2 = {[Σ {P (j) -α (i)} ² ] / 4} ^1/2 (1), and the calculated value is displayed on the display unit 13. It should be noted that Σ is an operation symbol indicating the addition sum when changing from j = i-4 to j = i.

The description will be supplemented. Part (a) of FIG. 3 shows the measured value P (i) of the optical power stored in each address i of the memory 7.
Is shown. The position of the pointer 15 is sequentially shifted so as to point to the address where the latest measured value is stored. Figure 3
The example shows that the most recent measurement value was written to address 20. Now, measured value P (20) = 108.1 at address 20
When 4 is written, the arithmetic unit 9 takes in five measurement value data within the frame of the window W shown in FIG. 3 from the position of the address 20 indicated by the pointer 15 (the window frame setting device in FIG. 1). (Assuming K = 5, which is indicated in 11).

Then, the arithmetic unit 9 calculates the maximum value Pa (20) = 108.14, the minimum value Pi (20) = 107.99, and the standard deviation σ (20) = 0.0340 from these five data. Explaining with the example of FIG. 2, the window W of FIG. 2 is the same as the window W of FIG. 3, and shifts in the direction of → with time, and the maximum value Pa and the minimum value Pi of the optical power data in this window W The calculation unit 9 will calculate the standard deviation σ. The device of FIG.
Current optical power measurement value P (20) = 108.14μW, maximum value Pa
(20) = 108.14 μW, minimum value Pi (20) = 107.99 μW, and standard deviation σ (20) = 0.0340 are displayed on the display unit 13.

As described above, in this example, the output stability of the light source is "standard deviation per 20 minutes is 0.1 μW or less".
Since it is assumed that the measured value P (15)
It can be seen that the desired stable value of the optical power was obtained when was stored. The apparatus of FIG. 1 can set a target output stable value in a setter (not shown), and compares the target stable value with the calculated standard deviation value. A signal to the effect can be issued.

In the above-mentioned example, "standard deviation within a fixed time" is shown as a criterion for stability, but in addition, "rate of power change within a fixed time" and "fluctuation within a fixed time" are also shown. You may make it judge by "amplitude" etc. In the case of the power change rate (differential value), Pd (i) = {P (i) −P (i-1)} / T _int T _int : The measurement time interval is calculated in advance and the Display maximum and minimum. In the case of fluctuation amplitude, the maximum value Pa (i) -minimum value Pi (i) may be displayed.

[0022]

As described above, according to the present invention, the stability of the light source can be measured by the optical power meter alone.
There is no need to prepare other devices such as personal computers and recorders. Further, when the trend of the optical power is displayed by a recorder or the like, the standard deviation, the differential value and the like cannot be directly read, so that reliable measurement could not be performed conventionally, but it becomes possible according to the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of an optical power meter according to the present invention.

FIG. 2 is a diagram showing a relationship between a temporal transition of optical power and a “window”.

FIG. 3 is a diagram showing a relationship between memory contents and various calculation data.

[Explanation of symbols]

 1 Light receiving part 3 Measuring circuit part 5 AD converter 7 Memory 9 Computing part 11 Window frame setting device 13 Display device

Claims (1)

[Claims] 1. A measuring device comprising a light receiving section for receiving a light beam and a measuring circuit section for outputting a signal (S3) according to the optical power applied to the light receiving section, wherein the measuring signal (S3) To an digital value P (i), a memory means for successively storing the digital values P (i) output by the AD converter, and a digital value P (i) stored in the memory means. Window frame setter that specifies how many time-series consecutive digital values are to be taken out, and the most recently stored digital value P (M) as the starting point The number (K) of digital values designated by the window frame setting device is read from the memory means, and the maximum digital value, the minimum digital value, and the standard deviation calculation value are calculated from the read digital values. The calculation part and the digital value of the maximum value obtained by this calculation part, the minimum Digital value, an optical power meter, characterized in that it and a display for displaying at least one of the calculated value of the standard deviation of.