JP2009105548A - Threshold measuring method and its apparatus of optical module circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress relaxation oscillation of input optical signal strength, and accurately measure the threshold. <P>SOLUTION: A threshold measuring apparatus 1 is provided with an optical attenuator 3 which attenuates an optical signal of fixed strength from an optical source 2, and inputs into an optical module circuit 6. Moreover, a multimeter 8 which detects an output optical signal, is connected to an output terminal of the optical module circuit 6. A control device 9 controls the optical attenuator 3 and the multimeter 8, and measures a lower threshold Pt1 and an upper threshold Pt2 of the optical module circuit 6 using a two division method. Moreover, when input optical signal strength is changed to a mean value Pmid by the two division method, the control device 9 gradually changes an attenuation amount of the optical attenuator 3 in a step. Thereby, it is possible to suppress the relaxation oscillation of the input optical signal strength. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and apparatus for measuring a threshold value of an optical module circuit having a hysteresis characteristic between an input optical signal intensity and an output electrical signal.

  An optical module circuit including a light receiving element such as a phototransistor or a photodiode is used for optical communication, an optical sensor, or the like. Some of these optical module circuits have hysteresis characteristics between the input optical signal intensity and the output electric signal in order to prevent malfunction due to noise, for example. In this case, the optical module circuit has an upper limit threshold value of the input optical signal strength at which the output electric signal is inverted while the input optical signal strength is changing from a small value to a large value, and a value from a large value to a small value of the input optical signal strength. And a lower limit threshold value of the input optical signal intensity at which the output electric signal is inverted while changing to. The hysteresis characteristic is a characteristic in which the upper limit threshold and the lower limit threshold are different, and the upper limit threshold is larger than the lower limit threshold.

  Conventionally, a method using a bisection method is known as a method for measuring an upper limit threshold and a lower limit threshold of an electronic circuit having such hysteresis characteristics (see, for example, Patent Document 1).

  In this bisection method, when the lower threshold is measured, an input signal equal to or greater than the initial search range is set as an initial value, and then the input signal is changed from the initial value to an intermediate value of the initial search range. Then, based on the output signal at the intermediate value, it is determined whether the region where the lower limit threshold exists is above or below the intermediate value in the initial search range, and the next search range is set to the original 1/2 based on the result. Refine to. This narrowing down operation is repeated until the search range becomes 0, and the input signal when the search range becomes 0 is measured as the lower limit threshold value.

  Similarly, when measuring the upper threshold, after setting an input signal that is equal to or less than the initial search range as an initial value, the input signal is changed from the initial value to an intermediate value of the initial search range. Then, based on the output signal at the intermediate value, it is determined whether the region where the upper limit threshold exists is above or below the intermediate value in the initial search range, and the next search range is determined from the result to the original 1/2. Refine to. This narrowing operation is repeated until the search range becomes 0, and the input signal when the search range becomes 0 is measured as the upper limit threshold value.

JP-A-11-72542

  By the way, there is an optical module circuit measuring apparatus that adjusts the input optical signal intensity by attenuating an optical signal having a constant intensity output from a light source using an optical attenuator. In this case, the optical attenuator adjusts the attenuation amount by rotating a disk-shaped attenuation plate having a different attenuation amount according to the angle by using a servo motor or the like.

  Further, in the measurement method according to Patent Document 1, the intermediate value gradually approaches the upper limit threshold and the lower limit threshold. On the other hand, when the input optical signal intensity is changed from a predetermined value (for example, an initial value) to an intermediate value, relaxation vibration tends to occur in the input optical signal intensity due to the operating characteristics of the optical attenuator (servo motor or the like). At this time, due to the relaxation oscillation, the input optical signal intensity temporarily exceeds the upper limit threshold and the lower limit threshold, and the output electrical signal changes different from the value for the intermediate value. As a result, when determining whether the upper limit threshold and the lower limit threshold are above or below the intermediate value in the search range, an incorrect range is determined, and there is a problem that a threshold measurement error or the like occurs.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an optical module circuit threshold measurement method capable of accurately measuring a threshold by suppressing relaxation oscillation of input optical signal intensity and The object is to provide such a device.

  In order to solve the above-described problem, the invention of claim 1 is directed to an upper limit threshold value at which the output electrical signal changes while the input optical signal intensity is changing from a small value to a large value, and a value with a large input optical signal intensity. A threshold value measuring method for an optical module circuit having a hysteresis characteristic between an input optical signal intensity and an output electrical signal, and a lower limit threshold value at which the output electrical signal changes in the middle of changing from a small value to a small value, When measuring the lower limit threshold, after setting the input optical signal intensity equal to or higher than the initial search range as the upper limit initial value, the input optical signal intensity is changed from the upper limit initial value to the intermediate value of the initial search range, the intermediate value Based on the output electrical signal, the region where the lower threshold value exists is determined whether it is above or below the intermediate value in the initial search range, and the next search range is narrowed down to ½ of the initial range based on the result. Inspect work It repeats until the range becomes 0, and the lower limit threshold measurement step for measuring the intermediate value when the search range becomes 0 as the lower limit threshold, and when measuring the upper limit threshold, lowers the input optical signal intensity below the initial search range. After setting as the initial value, the input optical signal intensity is changed from the lower limit initial value to the intermediate value of the initial search range, and the region where the upper limit threshold exists based on the output electrical signal at the intermediate value is determined as the initial search range. When it is above or below the intermediate value in the middle, the next search range is narrowed down to the original half from the result, and this narrowing operation is repeated until the search range becomes 0, and when the search range becomes 0 An upper threshold measuring step for measuring the intermediate value of the optical signal as an upper threshold, wherein the input optical signal intensity is adjusted by attenuating an optical signal having a constant intensity using an optical attenuator, and the input optical signal intensity is adjusted. Change to intermediate value When to be, has a configuration comprising an attenuation amount change step of stepwise changing the attenuation amount of the optical attenuator.

  According to a second aspect of the present invention, in the attenuation amount changing step, the amount of change when the input optical signal intensity is changed to an intermediate value is divided by the resolution based on the optical attenuator, and this value is expressed as a power series of a constant b. The attenuation amount of the optical attenuator is changed so that the input optical signal intensity changes in order from the higher order term to the lower order term of the polynomial.

  According to the invention of claim 3, the upper threshold value at which the output electrical signal changes while the input optical signal intensity is changing from a small value to a large value, and the middle when the input optical signal intensity is changing from a large value to a small value A threshold value measuring apparatus for an optical module circuit having a hysteresis characteristic between the input optical signal intensity and the output electric signal, and when measuring the lower limit threshold, After setting the input optical signal intensity equal to or higher than the search range as the upper limit initial value, the input optical signal intensity is changed from the upper limit initial value to the intermediate value of the initial search range, and the lower limit based on the output electric signal at the intermediate value It is determined whether the region where the threshold exists is above or below the intermediate value in the initial search range, and the next search range is narrowed down to ½ of the initial value from the result, and this narrowing work is performed until the search range becomes zero. repetition, Lower limit threshold measurement means for measuring an intermediate value when the search range becomes 0 as a lower limit threshold, and when measuring the upper limit threshold, input light signal intensity below the initial search range is set as a lower limit initial value, and then input The optical signal intensity is changed from the lower limit initial value to the intermediate value of the initial search range, and the region where the upper limit threshold exists based on the output electrical signal at the intermediate value is above or below the intermediate value in the initial search range. The next search range is narrowed down to 1/2 of the initial range from the result, and this narrowing operation is repeated until the search range becomes 0, and the intermediate value when the search range becomes 0 is measured as the upper threshold. The input optical signal intensity is adjusted by attenuating an optical signal having a constant intensity using an optical attenuator, and the input optical signal intensity is changed to an intermediate value. Of the optical attenuator It is configured to include the attenuation amount change means for stepwise changing the 衰量.

  According to a fourth aspect of the present invention, the attenuation amount changing means divides the amount of change when changing the input optical signal intensity to an intermediate value by the resolution based on the optical attenuator, and expresses this value as a power series of a constant b. The attenuation amount of the optical attenuator is changed so that the input optical signal intensity changes in order from the higher order term to the lower order term of the polynomial.

  According to the first and third aspects of the present invention, when the input optical signal intensity is changed to the intermediate value, the attenuation amount of the optical attenuator is changed stepwise, so that the input optical signal intensity is directly directed to the intermediate value. As compared with the case of changing to, the relaxation oscillation of the attenuation amount can be suppressed. For this reason, since the input light vibration intensity does not exceed (overshoot) from the intermediate value, errors in narrowing the search range can be eliminated, and the threshold value can be measured accurately.

  According to the second and fourth aspects of the present invention, the amount of change in the input optical signal intensity is divided by the resolution by the optical attenuator, and this value is changed from a higher-order term to a lower-order term of the polynomial expressed as a power series of the constant b. The attenuation amount of the optical attenuator is changed so that the input optical signal intensity changes sequentially. For this reason, the attenuation amount of the optical attenuator can be largely changed at first to quickly bring the input optical signal intensity close to the intermediate value. Further, since the change in the attenuation amount of the optical attenuator becomes smaller as the input optical signal intensity approaches the intermediate value, it is possible to prevent the input optical signal intensity from exceeding the intermediate value.

  Hereinafter, an optical module circuit threshold measurement device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  First, FIG. 1 shows a threshold measurement device 1 according to an embodiment of the invention, and the threshold measurement device 1 is composed of a light source 2, an optical attenuator 3, a multimeter 8, and the like which will be described later.

  The light source 2 includes a light emitting element such as a laser diode, for example, and outputs a light signal having a constant intensity. Further, the optical attenuator 3 variably attenuates the optical signal from the light source 2 and inputs the attenuated input optical signal I to the device under test 5 (Device Under Test) including the optical module circuit 6 via the optical channel selector 4. To do. Here, the optical attenuator 3 includes, for example, a disc-shaped attenuation plate having different attenuation amounts according to angles, and the attenuation amount is adjusted by rotating the attenuation plate using, for example, a servo motor. ing.

  The optical channel selector 4 selectively inputs an input optical signal I to either the device under test 5 or the optical power meter 7. The optical power meter 7 measures the intensity of the input optical signal I attenuated by the optical attenuator 3.

  The device under test 5 includes an optical module circuit 6. The optical module circuit 6 includes a light receiving element 6A such as a photodiode or a phototransistor. When the input optical signal I is input to the device under test 5, the optical module circuit 6 receives the input optical signal I using the light receiving element 6 </ b> A, and the current, voltage, etc. according to the input optical signal intensity are received. An output electrical signal E is output.

  Further, as shown in FIG. 6, the optical module circuit 6 has an input optical signal in which the output electrical signal E is inverted from a high level H to a low level L while the input optical signal intensity is changing from a large value to a small value. An intensity lower limit threshold Pt1 and an input optical signal intensity upper limit threshold Pt2 at which the output electric signal E is inverted from a low level L to a high level H while the input optical signal intensity is changing from a small value to a large value. is doing. At this time, the upper limit threshold Pt2 is larger than the lower limit threshold Pt1 (Pt2> Pt1).

  The multimeter 8 is connected to the output terminal of the optical module circuit 6 and detects the output electric signal E of the optical module circuit 6. The control device 9 is connected to the optical attenuator 3, the optical channel selector 4, the optical power meter 7 and the multimeter 8. And the control apparatus 9 controls these based on the threshold value measurement program mentioned later, and measures the minimum threshold value Pt1 and the upper limit threshold value Pt2 of the optical module circuit 6 using a bisection method.

  The threshold measurement apparatus 1 according to the present embodiment has the above-described configuration. Next, a threshold measurement program by the threshold measurement apparatus 1 will be described with reference to FIGS. Steps 2 to 11 show a measurement process for the lower limit threshold value Pt1, and steps 12 to 21 show a measurement process for the upper limit threshold value Pt2.

  First, in step 1, a value greater than or equal to the search range is set as the upper limit initial value Pmax, and a value less than or equal to the search range is set as the lower limit initial value Pmin.

  Next, in step 2, the magnitude of half of the initial search range (Pmax−Pmin) of the input optical signal I is calculated as the change ΔPs1 from the upper limit initial value Pmax to the intermediate value Pmid. In step 3, the change ΔPs1 is subtracted from the upper limit initial value Pmax to calculate the first intermediate value Pmid.

  Next, in step 4, as will be described later, a process for changing the input optical signal intensity from the upper limit initial value Pmax to the intermediate value Pmid is performed, and the input optical signal intensity is set to the intermediate value Pmid.

  Next, in step 5, it is determined whether or not the output electrical signal E is at a high level H. When it is determined “YES” in step 5, since the output electrical signal E is not inverted from the high level H to the low level L, the lower limit threshold value Pt1 is considered to be a value lower than the current intermediate value Pmid. . Therefore, in step 6, the current change ΔPs1 is halved as the change ΔPs1 from the current intermediate value Pmid to the next intermediate value Pmid. Thereafter, the process proceeds to step 7, and as a process of updating the intermediate value Pmid, a new change ΔPs1 is subtracted from the current intermediate value Pmid to calculate the next intermediate value Pmid.

  On the other hand, when “NO” is determined in Step 5, the output electric signal E is inverted from the high level H to the low level L, and therefore, the lower limit threshold value Pt1 is considered to be higher than the current intermediate value Pmid. Therefore, in step 8, the current change ΔPs1 is halved as the change ΔPs1 from the current intermediate value Pmid to the next intermediate value Pmid. Thereafter, the process proceeds to step 9, and as a process for updating the intermediate value Pmid, a new change ΔPs1 is added to the current intermediate value Pmid to calculate the next intermediate value Pmid.

  When Steps 7 and 9 are completed, the process proceeds to Step 10 to determine whether or not the updated change ΔPs1 is smaller than a predetermined convergence determination value R in order to determine whether or not the next search range has become zero. judge. If “YES” is determined in Step 10, the search range is substantially 0. Therefore, the process proceeds to Step 11, and the intermediate value Pmid calculated in Steps 7 and 9 is determined as the lower limit threshold value Pt1 ( Pt1 = Pmid).

  On the other hand, if “NO” is determined in step 10, the search range is not 0, and thus the processing from steps 4 to 10 is repeated.

  Next, in step 12, as the change ΔPs2 from the lower limit initial value Pmin to the intermediate value Pmid, half the initial search range (Pmax−Pmin) of the input optical signal I is calculated. In step 13, the change ΔPs2 is added to the lower limit initial value Pmin to calculate the first intermediate value Pmid.

  Next, in step 14, as will be described later, a process of changing the input optical signal intensity from the lower limit initial value Pmin to the intermediate value Pmid is performed, and the input optical signal intensity is set to the intermediate value Pmid.

  Next, in step 15, it is determined whether or not the output electrical signal E is at a low level L. When it is determined as “YES” in step 15, the output electric signal E is not inverted from the low level L to the high level H, so the upper limit threshold value Pt 2 is considered to be a value higher than the current intermediate value Pmid. . Therefore, in step 16, the current change ΔPs2 is halved as the change ΔPs2 from the current intermediate value Pmid to the next intermediate value Pmid. Thereafter, the process proceeds to step 17, and as a process for updating the intermediate value Pmid, a new change ΔPs2 is added to the current intermediate value Pmid to calculate the next intermediate value Pmid.

  On the other hand, when “NO” is determined in step 15, since the output electrical signal E is inverted from the low level L to the high level H, the upper limit threshold value Pt 2 is considered to be a value lower than the current intermediate value Pmid. Therefore, in step 18, the current change ΔPs2 is halved as the change ΔPs2 from the current intermediate value Pmid to the next intermediate value Pmid. Thereafter, the process proceeds to step 19, and as a process for updating the intermediate value Pmid, a new change ΔPs2 is subtracted from the current intermediate value Pmid to calculate the next intermediate value Pmid.

  When Steps 17 and 19 are completed, the process proceeds to Step 20 to determine whether or not the updated change ΔPs2 is smaller than a predetermined convergence determination value R in order to determine whether or not the next search range has become zero. judge. If “YES” is determined in the step 20, the search range is substantially 0. Therefore, the process proceeds to the step 21, and the intermediate value Pmid calculated in the steps 17 and 19 is determined as the upper limit threshold value Pt2 ( Pt2 = Pmid).

  On the other hand, if “NO” is determined in step 20, the search range is not 0, and thus the processes in steps 14 to 20 are repeated.

  Next, the process of changing the input optical signal intensity in step 4 from the upper limit initial value Pmax to the intermediate value Pmid will be described with reference to FIG.

  First, in step 31, the change amount between the upper limit initial value Pmax and the intermediate value Pmid is divided by the resolution based on the optical attenuator 3 as the change amount coefficient S 1. Here, since the input optical signal intensity is adjusted by the attenuation amount of the optical attenuator 3, the resolution is determined by the resolution of the attenuation amount of the optical attenuator 3.

  Next, in step 32, as shown in the following equation 1, the variation coefficient S1 is expressed by a power series of a constant b. However, the constant b is larger than 1 and smaller than the variation coefficient S1 (1 <b <S1).

  For example, when the variation coefficient S1 is 300 and the constant b is 2, the variation coefficient S1 can be expressed by a polynomial shown in the following formula 2.

Next, in step 33, the coefficient k _i of the low-order term of the polynomial expressed by a power series is adjusted so that all the coefficients k _i have values of 1 or more. Specifically, as shown in the following equation (3), 1 is subtracted from the coefficient k _{i + 1 of} the high-order term, and a constant b is added to the coefficient k _i of the low-order term. In the present embodiment, as will be described later, the input optical signal intensity is changed for each polynomial term. On the other hand, for example, when the variation coefficient S1 corresponds to the nth power of b, the upper limit initial value Pmax and the intermediate value Pmid are changed all at once, and relaxation oscillation occurs. In order to prevent such a sudden change in input optical signal intensity, the coefficient k _i is adjusted.

For example, when the variation coefficient S1 is 300 and the constant b is 2, the polynomial after the coefficient k _i is adjusted can be expressed as the following equation (4).

Next, in step 34, as shown in the following equation (5), the upper limit initial value Pmax is subtracted in the order of high-order terms to low-order terms, and the input optical signal intensity is set to P ₀ , Change in the order of P ₁ ,. Finally, the input optical signal intensity is made to coincide with the intermediate value Pmid.

For example, when the variation coefficient S1 is 300 and the constant b is 2, the first intensity P ₀ is changed to a value obtained by subtracting 128 from the upper limit initial value Pmax. The second intensity P ₁ is changed to a value obtained by subtracting 192 (= 128 + 64) from the upper limit initial value Pmax. The third strength P ₂ is changed to a value obtained by subtracting 224 (= 128 + 64 + 32) from the upper limit initial value Pmax. The fourth intensity P ₃ is changed to a value obtained by subtracting 256 (= 128 + 64 + 2 × 32) from the upper limit initial value Pmax. Following repeating the same procedure, in 12 th intensity P ₁₁ subtracts 300 from the upper limit initial value Pmax, to match the intermediate value Pmid. Accordingly, the upper limit initial value Pmax is gradually approached to the intermediate value Pmid in a stepwise manner. Then, when step 34 ends, the process returns.

  Next, the process of changing the input optical signal intensity in step 14 from the lower limit initial value Pmin to the intermediate value Pmid will be described with reference to FIG.

  First, in step 41, the change amount between the lower limit initial value Pmin and the intermediate value Pmid is divided by the resolution based on the optical attenuator 3 as the change amount coefficient S2.

  Next, in step 42, the change coefficient S2 is expressed by a power series of a constant b as shown in the following equation (6). However, the constant b is a value greater than 1 and smaller than the variation coefficient S2 (1 <b <S2).

Next, in step 43, the coefficient k _i of the low-order term of the polynomial expressed by a power series is adjusted so that all the coefficients k _i have values of 1 or more. Specifically, as in step 33, as shown in the following Expression 7, 1 is subtracted from the coefficient k _{i + 1 of} the high-order term, and a constant b is added to the coefficient k _i of the low-order term.

Next, in step 44, as shown in the following equation (8), an addition process is performed on the lower limit initial value Pmin in the order of high-order terms to low-order terms, and the input optical signal intensity is set to P ₀ , Change in the order of P ₁ ,. Finally, the input optical signal intensity is made to coincide with the intermediate value Pmid. Thus, the lower limit initial value Pmin is gradually approached to the intermediate value Pmid in a stepwise manner. Then, when step 44 ends, the process returns.

  The threshold value measuring apparatus 1 according to the present embodiment changes the input optical signal intensity to the intermediate value Pmid based on the above-described processing. Thereby, the input optical signal intensity is divided into a plurality of steps and gradually approaches the intermediate value Pmid. For example, when the variation coefficient S2 is 300 and the constant b is 2, as shown in FIG. 9, it is divided into 12 steps and gradually approaches the intermediate value Pmid. Here, as in the comparative example shown in FIG. 8, for example, when the input optical signal intensity is changed at a stroke from the upper limit initial value Pmax to the intermediate value Pmid, the input optical signal intensity is relaxed. Vibration occurs. In this case, the input optical signal intensity temporarily falls below the lower limit threshold value Pt1, and the output electrical signal E may be inverted by mistake. On the other hand, in the present embodiment, as shown in FIG. 7, the input optical signal intensity is divided into a plurality of steps and gradually approaches the intermediate value Pmid, so that the input optical signal intensity can be rapidly increased in one step. Compared with the case of changing, the relaxation oscillation of the input optical signal intensity can be suppressed.

  However, when the number of steps increases, the change time of the input optical signal intensity becomes longer, and the measurement efficiency decreases. Also, the number of steps tends to change according to the constant b. Therefore, the relationship between the constant b and the number of steps was examined. The result is shown in FIG. The result of FIG. 10 shows a case where the variation coefficient S1 (S2) is 1000.

From this result, it can be seen that as the constant b increases, the number of steps tends to increase. Considering this reason, in this embodiment, in order to prevent the input optical signal intensity from changing at a stretch, the coefficient of the low-order term of the power series is adjusted, and the coefficients k _i of all orders are positive. The value (k _i > 0) is set. For this reason, the coefficient (for example, k ₀ ) of the low-order term tends to increase, and the number of steps is considered to increase. From the above results, it is considered that the constant b is preferably set to a value of about 2 to 10 in order to perform processing with an appropriate number of steps.

  Thus, in the present embodiment, when the input optical signal intensity is changed to the intermediate value Pmid, the attenuation amount of the optical attenuator 3 is changed in a stepwise manner. As compared with the above, the relaxation oscillation of the attenuation can be suppressed. For this reason, since the input light vibration intensity does not exceed (overshoot) the intermediate value Pmid, errors in narrowing the search range can be eliminated, and the lower limit threshold value Pt1 and the upper limit threshold value Pt2 can be accurately measured. it can.

  Further, the amount of change in the input optical signal intensity is divided by the resolution of the optical attenuator 3, and this value is expressed in order from the higher order term to the lower order term of the polynomial expressed as a power series of the constant b. Change. For this reason, the attenuation amount of the optical attenuator 3 can be greatly changed at the beginning to quickly bring the input optical signal intensity close to the intermediate value Pmid. Further, since the change in the attenuation amount of the optical attenuator 3 decreases as the input optical signal intensity approaches the intermediate value Pmid, it is possible to prevent the input optical signal intensity from exceeding the intermediate value Pmid.

  In the above embodiment, steps 2 to 11 in FIG. 2 show a specific example of the lower threshold measurement process (lower threshold measurement means), and steps 12 to 21 in FIG. 3 represent the upper threshold measurement process (upper threshold measurement). A specific example of the means) is shown. Further, steps 31 to 34 in FIG. 4 and steps 41 to 44 in FIG. 5 show specific examples of the attenuation amount changing step (attenuation amount changing means).

It is a block diagram which shows the threshold value measuring apparatus by embodiment of this invention. It is a flowchart which shows the threshold value measurement program used with the threshold value measuring apparatus in FIG. It is a flowchart following FIG. 3 is a flowchart showing a process of changing the input optical signal intensity in FIG. 2 from an upper limit initial value to an intermediate value. It is a flowchart which shows the process which changes the input optical signal intensity | strength in FIG. 3 from a lower limit initial value to an intermediate value. FIG. 2 is a characteristic diagram showing a relationship between an input optical signal intensity and an output electric signal of the optical module circuit in FIG. 1. It is a characteristic diagram which shows the time change of the input optical signal strength at the time of using the threshold value measuring apparatus by this Embodiment, and an output electrical signal. It is a characteristic diagram which shows the time change of the input optical signal strength at the time of using the threshold value measuring apparatus by a comparative example, and an output electrical signal. It is a characteristic diagram which shows the change for every step of input optical signal intensity at the time of using the threshold value measuring apparatus by this Embodiment. It is a characteristic diagram which shows the relationship between the constant b of a power series, and the number of steps.

Explanation of symbols

1 Threshold Measurement Device 2 Light Source 3 Optical Attenuator 8 Multimeter 9 Control Device

Claims (4)

The upper limit threshold for changing the output electrical signal while the input optical signal intensity is changing from a small value to a large value, and the output electrical signal changing while the input optical signal intensity is changing from a large value to a small value A threshold measurement method of an optical module circuit having a lower limit threshold and having a hysteresis characteristic between an input optical signal intensity and an output electrical signal,
When measuring the lower limit threshold, after setting the input optical signal intensity equal to or higher than the initial search range as the upper limit initial value, the input optical signal intensity is changed from the upper limit initial value to the intermediate value of the initial search range, the intermediate value Based on the output electrical signal, the region where the lower threshold value exists is determined whether it is above or below the intermediate value in the initial search range, and the next search range is narrowed down to ½ of the initial range based on the result. A lower limit threshold measurement step of repeating the work until the search range becomes 0, and measuring an intermediate value when the search range becomes 0 as a lower limit threshold;
When measuring the upper threshold, after setting the input optical signal intensity below the initial search range as the lower limit initial value, the input optical signal intensity is changed from the lower limit initial value to the intermediate value of the initial search range, the intermediate value Based on the output electrical signal, the region where the upper limit threshold exists is judged whether it is above or below the intermediate value in the initial search range, and the next search range is narrowed down to the original 1/2 based on the result. An upper limit threshold measurement step of repeating the work until the search range becomes 0, and measuring an intermediate value when the search range becomes 0 as an upper limit threshold,
The input optical signal intensity is adjusted by attenuating a constant intensity optical signal using an optical attenuator,
A method for measuring a threshold value of an optical module circuit, comprising: an attenuation amount changing step of changing the attenuation amount of the optical attenuator stepwise when the input optical signal intensity is changed to an intermediate value.   In the attenuation amount changing step, the amount of change when changing the input optical signal intensity to an intermediate value is divided by the resolution based on the optical attenuator, and this value is expressed by a higher-order term of a polynomial expressed by a power series of a constant b. The method of measuring a threshold value of an optical module circuit according to claim 1, wherein the attenuation amount of the optical attenuator is changed so that the input optical signal intensity changes sequentially from low to high-order terms. The upper limit threshold for changing the output electrical signal while the input optical signal intensity is changing from a small value to a large value, and the output electrical signal changing while the input optical signal intensity is changing from a large value to a small value A threshold measurement device for an optical module circuit having a lower limit threshold and having a hysteresis characteristic between an input optical signal intensity and an output electrical signal,
When measuring the lower limit threshold, after setting the input optical signal intensity equal to or higher than the initial search range as the upper limit initial value, the input optical signal intensity is changed from the upper limit initial value to the intermediate value of the initial search range, the intermediate value Based on the output electrical signal, the region where the lower threshold value exists is determined whether it is above or below the intermediate value in the initial search range, and the next search range is narrowed down to ½ of the initial range based on the result. A lower limit threshold measuring means for repeating the work until the search range becomes 0, and measuring an intermediate value when the search range becomes 0 as a lower limit threshold;
When measuring the upper threshold, after setting the input optical signal intensity below the initial search range as the lower limit initial value, the input optical signal intensity is changed from the lower limit initial value to the intermediate value of the initial search range, the intermediate value Based on the output electrical signal, the region where the upper limit threshold exists is judged whether it is above or below the intermediate value in the initial search range, and the next search range is narrowed down to the original 1/2 based on the result. An upper limit threshold measurement unit that repeats the work until the search range becomes 0, and measures an intermediate value when the search range becomes 0 as an upper limit threshold;
The input optical signal intensity is adjusted by attenuating a constant intensity optical signal using an optical attenuator,
A threshold measuring device for an optical module circuit, comprising: an attenuation amount changing means for changing the attenuation amount of the optical attenuator stepwise when the input optical signal intensity is changed to an intermediate value.   The attenuation amount changing means divides the amount of change when the input optical signal intensity is changed to an intermediate value by the resolution based on the optical attenuator, and this value is expressed by a higher order term of a polynomial expressed by a power series of a constant b. 4. The threshold measuring apparatus for an optical module circuit according to claim 3, wherein the attenuation amount of the optical attenuator is changed so that the input optical signal intensity changes sequentially from low to high-order terms.

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