Control device, optical receiver, and optical transmitter

Abstract

To provide a control device, an optical receiver, and an optical transmitter capable of calculating a drive current value of a set attenuation amount at a set temperature.SOLUTION: The control device 1 includes a variable optical attenuator (VOA) 2, a temperature monitor 3 that measures a surrounding temperature of a VOA2, and a controller 5 that controls the VOA2. A storage section 12 of a control section 5 stores a 1st function approximated to a relation of a drive current for each attenuation at a reference temperature and a 2nd function to calculate a temperature correction magnification to correct the drive current between a surrounding temperature and the reference temperature. The calculation unit 13 calculates the drive current value at the reference temperature by substituting the set attenuation amount into the first function, calculates the temperature correction magnification by substituting the ambient temperature into the second function, and calculates the drive current value for obtaining the set attenuation amount at the ambient temperature based on the drive current value at the reference temperature calculated by the first function and the temperature correction magnification calculated by the second function. The drive control unit 14 drives and controls the variable attenuator 5 based on the calculated drive current value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device, an optical receiver, and an optical transmitter. [Background technology]

[0002] 21 is a block diagram showing an example of a conventional control device 100. The control device 100 includes a VOA (Variable Optical Attenuator) 101, an optical monitor 102, and a control unit 103. The VOA 101 is a variable attenuator that attenuates input light. The optical monitor 102 detects the signal intensity of the output light of the VOA 101. The control unit 103 adjusts the attenuation amount of the VOA 101 based on the detection result of the optical monitor 102.

[0003] Furthermore, the signal strength detected by the optical monitor 102 is highly temperature dependent, and the signal strength fluctuates depending on the temperature, making it impossible to detect accurate signal strength, and therefore the attenuation of the VOA 101 cannot be adjusted accurately.

[0004] Therefore, the control unit 103 of the conventional control device 100 corrects the drive current value for obtaining the set attenuation of the VOA 101 using sensitivity characteristics according to the environmental temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-9488 [Patent Document 2] US Patent Application Publication No. 2011 / 0206386 [Patent Document 3] Japanese Patent Application Publication No. 2019-134277 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-275705 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-274258 [Patent Document 6] US Patent Application Publication No. 2007 / 0230959 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional control device 100, in order to correct the drive current value for obtaining the set attenuation of the VOA 101 using the sensitivity characteristics according to the environmental temperature, data for preparing the sensitivity characteristics is required. Moreover, the control device 100 needs to prepare the sensitivity characteristics according to the environmental temperature, but in order to improve the correction accuracy, the amount of data on the sensitivity characteristics needs to be increased. Moreover, the control device 100 needs to perform complex arithmetic processing before calculating the drive current value of the VOA 101 using the prepared sensitivity characteristics.

[0007] Moreover, in the control device 100, if the control device 100 performs FB (Feedback) control to adjust the attenuation of the VOA 101 based on the monitoring result of the optical monitor 102 while performing FB control for a different purpose, for example, to control the output amplitude of the optical receiver, this results in multi-loop control, making the control difficult. Therefore, the processing load on the control device 100 to accurately calculate the drive current value to obtain the set attenuation is large.

[0008] In one aspect, an object is to provide a control device or the like that can reduce the processing load in calculating a drive current value for obtaining a set attenuation amount. [Means for solving the problem]

[0009] In one aspect, the control device disclosed herein includes a variable attenuator that attenuates input light, a temperature monitor that measures the ambient temperature of the variable attenuator, and a control unit that controls the variable attenuator. The control unit includes a memory unit, a calculation unit, and a drive control unit. The memory unit stores a first function that approximates the relationship between the drive current value for each attenuation amount of the variable attenuator at a reference temperature and a second function that calculates a temperature correction factor that corrects the drive current value between the ambient temperature and the reference temperature. The calculation unit calculates the drive current value at the reference temperature by substituting a set attenuation amount into the first function, and calculates the temperature correction factor at the ambient temperature by substituting the current ambient temperature into the second function. The calculation unit calculates a drive current value to obtain the set attenuation amount at the ambient temperature based on the drive current value at the reference temperature calculated using the first function and the temperature correction factor at the ambient temperature calculated using the second function. The drive control unit drives and controls the variable attenuator based on the drive current value calculated by the calculation unit. [Effects of the Invention]

[0010] According to one aspect of the control device disclosed in the present application, it is possible to reduce the processing load required to accurately calculate a drive current value for obtaining a set attenuation amount. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram illustrating an example of a control device according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of a quadratic curve that approximates the relationship between the attenuation amount and the drive current value for each reference temperature. [Figure 3] FIG. 3 is an explanatory diagram showing a graph in which drive current values ​​for each reference temperature are plotted as normalized values ​​with respect to a standard temperature. [Figure 4] FIG. 4 is a flowchart showing an example of the processing operation of the control unit related to the first setting processing. [Figure 5] FIG. 5 is a flowchart showing an example of the processing operation of the control unit related to the first calculation processing. [Figure 6]FIG. 6 is a block diagram illustrating an example of a control device according to the second embodiment. [Figure 7] FIG. 7 is an explanatory diagram showing an example of a quadratic curve that approximates the relationship between the attenuation amount for each reference wavelength and the drive current value. [Figure 8] FIG. 8 is an explanatory diagram showing a graph in which drive current values ​​for each reference wavelength normalized with respect to the reference wavelength are plotted. [Figure 9] FIG. 9 is a flowchart showing an example of the processing operation of the control unit related to the second setting processing. [Figure 10] FIG. 10 is a flowchart showing an example of the processing operation of the control unit related to the second calculation processing. [Figure 11] FIG. 11 is a block diagram illustrating an example of a control device according to the third embodiment. [Figure 12] FIG. 12 is a flowchart showing an example of the processing operation of the control unit related to the third calculation processing. [Figure 13] FIG. 13 is an explanatory diagram showing an example of a combination of measurement conditions for obtaining attenuation characteristics in the control device of the third embodiment. [Figure 14] FIG. 14 is a block diagram illustrating an example of a control device according to the fourth embodiment. [Figure 15] FIG. 15 is a flowchart showing an example of the processing operation of the control unit related to the third setting processing. [Figure 16] FIG. 16 is a flowchart showing an example of the processing operation of the control unit related to the fourth calculation processing. [Figure 17] FIG. 17 is a block diagram illustrating an example of a control device according to the fifth embodiment. [Figure 18] FIG. 18 is a flowchart showing an example of processing operations of the user device related to the user-side calculation process. [Figure 19] FIG. 19 is a flowchart showing an example of the processing operation of the control unit related to the fifth calculation processing. [Figure 20] FIG. 20 is an explanatory diagram illustrating an example of an optical transceiver according to this embodiment. [Figure 21] FIG. 21 is a block diagram showing an example of a conventional control device. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of a control device and the like disclosed in the present application will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. [Example]

[0013] FIG. 1 is a block diagram showing an example of a control device 1 according to a first embodiment. The control device 1 is a module having a VOA (Variable Optical Attenuator) 2, a temperature monitor 3, an optical monitor 4, and a control unit 5. The VOA 2 is, for example, an electroabsorption variable attenuator that variably attenuates input light according to a drive current. The VOA 2 is, for example, configured with a silicon photonics IC. The temperature monitor 3 is a sensor that measures the ambient temperature of the VOA 2. The optical monitor 4 measures the attenuation of the VOA 2 from the output power of the VOA 2, for example, from the signal intensity. A user device 50 sets various information in the control device 1 according to, for example, a setting operation.

[0014] The control unit 5 controls the VOA 2. The control unit 5 controls the VOA 2 using attenuation characteristics based on a reference temperature that have been acquired in advance. The control unit 5 calculates a drive current value for obtaining the set attenuation at the set temperature based on the attenuation characteristics based on the reference temperature, the set temperature of the VOA 2, and the set attenuation of the VOA 2. The control unit 5 then supplies a drive current equivalent to the calculated drive current value to the VOA 2. The control unit 5 acquires the set temperature from the temperature monitor 3 and the set attenuation from the user device 50.

[0015] The control unit 5 has a setting unit 11, a storage unit 12, a calculation unit 13, and a drive control unit 14. The setting unit 11 calculates a first function and a second function, which are part of the attenuation characteristics, and stores the calculated first function and second function in the storage unit 12. The first function is a quadratic curve that approximates the relationship between the drive current value for each attenuation of the VOA2 at a reference temperature, which will be described later. The second function is a formula that calculates a temperature correction factor that corrects the drive current value between the set temperature of the VOA2 and the reference temperature.

[0016] The calculation unit 13 calculates the drive current value at the reference temperature by substituting the set attenuation amount into the first function. The calculation unit 13 calculates the temperature correction factor at the set temperature by substituting the current ambient temperature as the set temperature into the second function. Furthermore, the calculation unit 13 calculates the drive current value for obtaining the set attenuation amount at the set temperature based on the drive current value at the reference temperature calculated using the first function and the temperature correction factor at the set temperature calculated using the second function, and sets the calculated drive current value in the drive control unit 14. The drive control unit 14 supplies a drive current corresponding to the set drive current value to the VOA2.

[0017] The optical monitor 4 is not used for FB control but is used to measure the attenuation of the VOA 2 required to calculate the attenuation characteristics.

[0018] Next, the operation of the control unit 5 for setting the first and second functions will be described. The optical monitor 4 sequentially measures the attenuation of the VOA 2 in advance under predetermined drive current conditions for at least three reference temperatures T1, T2, and T3. The predetermined drive current conditions are conditions in which the wavelength of the input light is the reference wavelength λ2 nm and the VOA 2 is driven at four drive current values, for example, 0 mA, I1 mA, I2 mA, and I3 mA. The drive current values ​​are not limited to four and can be changed as long as they are two or more. Each reference temperature is acquired from the temperature monitor 3. Furthermore, if the temperature difference between the temperature monitor 3 and the VOA 2 is always constant, the temperature state of the VOA 2 is less affected by the heat dissipation form of the control unit 5, enabling more accurate temperature correction. Therefore, it is desirable that the temperature monitor 3 be located near the VOA 2.

[0019] 2 is an explanatory diagram showing an example of a quadratic curve approximating the relationship between the attenuation and the drive current value at each reference temperature. The optical monitor 4 sequentially measures the attenuation of the VOA 2 at each drive current value of 0 mA, I1 mA, I2 mA, and I3 mA at the reference temperature T1. As a result, as shown in FIG. 2, the setting unit 11 obtains a quadratic curve approximating the relationship between the attenuation and the drive current value at the reference temperature T1 based on the attenuations A1, A2, and A3 that are the measurement results of the optical monitor 4 at the reference temperature T1. Then, the setting unit 11 calculates the drive current value I for each attenuation at the reference temperature T1 from the quadratic curve approximating the relationship between the attenuation and the drive current value at the reference temperature T1. VOA1 Formula 1 for calculating (A) is derived.

[0020]

number

[0021] The optical monitor 4 also sequentially measures the attenuation of the VOA 2 for each drive current value of 0 mA, I1 mA, I2 mA, and I3 mA at the reference temperature T2. As a result, the setting unit 11 obtains a quadratic curve approximating the relationship between the attenuation and the drive current value at the reference temperature T2, based on the attenuations A1, A2, and A3 that are the measurement results of the optical monitor 4 at the reference temperature T2, as shown in FIG. 2. Then, the setting unit 11 calculates the drive current value I for each attenuation at the reference temperature T2 from the quadratic curve approximating the relationship between the attenuation and the drive current value at the reference temperature T2. VOA2 Formula 2 is derived to calculate (A).

[0022]

number

[0023] In addition, the optical monitor 4 sequentially measures the attenuation amounts of the VOA 2 for drive current values of 0 mA, I1 mA, I2 mA, and I3 mA at the reference temperature T3. As a result, as shown in FIG. 2, the setting unit 11 obtains a quadratic curve that approximates the relationship between the attenuation amount and the drive current value at the reference temperature T3 based on the attenuation amounts A1, A2, and A3, which are the measurement results of the optical monitor 4 at the reference temperature T3. Then, the setting unit 11 derives Equation 3 for calculating the drive current value I VOA3 (A) at each attenuation amount at the reference temperature T3 from the quadratic curve that approximates the relationship between the attenuation amount and the drive current value at the reference temperature T3.

[0024] [Number]

[0025] By using these Equations 1 to 3, the control unit 5 can calculate the drive current value of the VOA 2 required for an arbitrary attenuation amount for each reference temperature. However, since it is limited to any one of the reference temperatures T1, T2, and T3, there remains a problem that the drive current value of the VOA 2 cannot be calculated at a set temperature other than the reference temperature.

[0026] Therefore, as a solution to such a problem, in the setting unit 11, based on the calculation results of Equations 1 to 3, with the reference temperature T2 as the reference temperature, the drive current values at each reference temperature for arbitrary attenuation amounts A4, A5, and A6 are normalized by the drive current value at the reference temperature T2. Note that it is desirable that the magnitude relationship of the reference temperatures is T1 < T2 < T3 [°C], and it is desirable that the magnitude relationship of the arbitrary attenuation amounts is A4 < A5 < A6 [dB]. Note that the arbitrary attenuation amounts may be set as A4 = A1, A5 = A2, and A6 = A3 as described above and can be changed as appropriate. FIG. 3 is an explanatory diagram showing a graph in which the values obtained by normalizing the drive current values for each reference temperature by the reference temperature T2 are plotted.

[0027] The setting unit 11 approximates the values obtained by normalizing the drive current values for each reference temperature by the reference temperature with a quadratic curve, and obtains Equations 4 to 6 from the quadratic curve for each approximated attenuation amount standard value. The setting unit 11 refers to the attenuation amount A4 shown in FIG. 3 and derives Equation 4 for calculating the attenuation amount standard value I nomal4 (T) with respect to the temperature T at the attenuation amount A4.

[0028]

number

[0029] The setting unit 11 refers to the attenuation A5 shown in FIG. 3 and calculates the attenuation standard value I for the attenuation A5 with respect to the temperature T. nomal5 Formula 5 is derived to calculate (T).

[0030]

number

[0031] The setting unit 11 refers to the attenuation A6 shown in FIG. 3 and calculates the attenuation standard value I nomal6 Formula 6 is derived to calculate (T).

[0032]

number

[0033] The setting unit 11 obtains the coefficients (α1, β1, γ1, α2, β2, γ2, α3, β3, γ3) of each order from Equations 4 to 6. The setting unit 11 calculates the average values ​​of the coefficients for each order (α=Average(α1, α2, α3), β=Average(β1, β2, β3), γ=Average(γ1, γ2, γ3)). Then, using these average values, the setting unit 11 calculates a normalized value of the drive current value with respect to temperature, that is, a temperature correction factor that is a correction factor for correcting the drive current value between a reference temperature and a set temperature. The set temperature is the ambient temperature of the VOA 2 measured by the temperature monitor 3. The solid line in FIG. 3 is a quadratic curve that shows the relationship between the temperature correction factor for correcting the drive current value between the reference temperature and the set temperature. The setting unit 11 calculates the temperature correction factor I using the average values ​​of the coefficients for each order (α=Average(α1, α2, α3), β=Average(β1, β2, β3), γ=Average(γ1, γ2, γ3)). nomal Formula 7 for calculating (T) is derived.

[0034]

number

[0035] Then, the setting unit 11 stores Equation 2 as a first function that calculates the drive current value for each attenuation amount at the reference temperature T2 and Equation 7 as a second function that calculates the temperature correction magnification in the storage unit 12. That is, the storage unit 12 stores only Equation 2 and Equation 7, i.e., the coefficients of Equation 2 and Equation 7.

[0036] Next, the operation of the control unit 5 for setting the drive current value for the VOA 2 to obtain the set attenuation amount at the set temperature and reference wavelength using the first and second functions will be described.

[0037] First, the set attenuation is, for example, a desired attenuation set in the VOA 2 by the user device 50. The set attenuation can also be set automatically in conjunction with, for example, the optical monitor 4. The set temperature of the VOA 2 is, for example, the ambient temperature of the VOA 2 measured by the temperature monitor 3 periodically or at required timing. In other words, the calculation unit 13 acquires the set attenuation and the set temperature of the VOA 2.

[0038] The calculation unit 13 calculates the drive current value at the reference temperature T2 by substituting the set attenuation into Equation 2. Furthermore, the calculation unit 13 calculates a temperature correction factor for correcting the drive current value between the reference temperature T2 and the set temperature by substituting the ambient temperature acquired from the temperature monitor 3 as the set temperature into Equation 7. Furthermore, the calculation unit 13 multiplies the drive current value calculated using Equation 2 by the temperature correction factor calculated using Equation 7 to calculate the drive current value required to obtain the set attenuation at the reference wavelength and set temperature, and sets the calculated drive current value in the drive control unit 14. The drive control unit 14 supplies a drive current corresponding to the set drive current value to the VOA2. As a result, the VOA2 can obtain the set attenuation at the set temperature and reference wavelength according to the drive current from the drive control unit 14.

[0039] 4 is a flowchart showing an example of the processing operation of the control unit 5 related to the first setting process. In FIG. 4, the setting unit 11 of the control unit 5 specifies an arbitrary reference temperature from among a plurality of reference temperatures when the wavelength of the input light is a reference wavelength (step S11). The reference temperatures are, for example, T1, T2, and T3. The setting unit 11 sequentially sets drive current values ​​of 0 mA, I1 mA, I2 mA, and I3 mA in the drive control unit 14 under the specified reference temperature and reference wavelength (step S12). As a result, the drive control unit 14 sequentially supplies drive currents corresponding to the set drive current values ​​to the VOA 2.

[0040] The setting unit 11 acquires the attenuation when the drive current is set to 0 mA, the attenuation A1 when the drive current is set to I1 mA, the attenuation A2 when the drive current is set to I2 mA, and the attenuation A3 when the drive current is set to I3 mA from the optical monitor 4 (step S13).

[0041] The setting unit 11 derives a first function for the specified reference temperature from a quadratic curve that approximates the relationship between the attenuation at the specified reference temperature and the drive current value from each attenuation amount for each drive current value (step S14). The setting unit 11 determines whether or not the first functions for all reference temperatures have been derived (step S15). The first functions for all reference temperatures are Equation 1 for reference temperature T1, Equation 2 for reference temperature T2, and Equation 3 for reference temperature T3.

[0042] If the first functions for all the reference temperatures have not been derived (step S15: No), the setting unit 11 determines whether or not there is an unspecified reference temperature among the three reference temperatures (step S16). If there is an unspecified reference temperature (step S16: Yes), the setting unit 11 proceeds to step S11 to specify the unspecified reference temperature.

[0043] Furthermore, when the first functions for all reference temperatures have been derived (step S15: Yes), the setting unit 11 substitutes the arbitrary attenuation amounts A4, A5, and A6 into Equation 1, Equation 2, and Equation 3 for each reference temperature (step S17). Then, the setting unit 11 calculates the drive current value for each reference temperature according to the arbitrary attenuation amounts A4, A5, and A6 (step S18).

[0044] The setting unit 11 derives a quadratic curve that approximates the relationship between the drive current value and the standard temperature T2 from the calculated drive current value for each reference temperature (step S19). Then, the setting unit 11 normalizes the drive current value for each reference temperature by the drive current value for the standard temperature T2 from the quadratic curve derived in step S19 (step S20).

[0045] The setting unit 11 derives Equation 4, Equation 5, and Equation 6 from a quadratic curve that approximates the relationship between the drive current value normalized by the drive current value at the reference temperature T2 (step S21). The setting unit 11 averages the coefficients for each order of Equation 4, Equation 5, and Equation 6, and derives Equation 7 as a second function that calculates a temperature correction factor for correcting the drive current value between the reference temperature T2 and the set temperature (step S22).

[0046] Then, the setting unit 11 stores in the memory unit 12 Equation 2, which calculates the drive current value corresponding to the set attenuation at the reference temperature T2, and Equation 7, which calculates the temperature correction multiplier for correcting the drive current value between the reference temperature T2 and the set temperature (step S23), and terminates the processing operation shown in Figure 4.

[0047] If there is no unspecified reference temperature (step S16: No), the setting unit 11 proceeds to step S17 to substitute any attenuation amount into Equation 1, Equation 2, and Equation 3 for each reference temperature.

[0048] 5 is a flowchart showing an example of the processing operation of the control unit 5 related to the first calculation process. In FIG. 5, the calculation unit 13 in the control unit 5 acquires a set attenuation amount and a set wavelength (step S31). The set attenuation amount and the set wavelength are acquired, for example, by settings in the user device 50. The set wavelength is a reference wavelength. The calculation unit 13 acquires a set temperature from the temperature monitor 3 (step S32). The set temperature is the ambient temperature of the VOA 2 measured by the temperature monitor 3.

[0049] The calculation unit 13 calculates the drive current value at the reference temperature T2 by substituting the set attenuation amount into Equation 2 (step S33). Furthermore, the calculation unit 13 calculates the temperature correction magnification by substituting the set temperature into Equation 7 (step S34).

[0050] The calculation unit 13 calculates a corrected drive current value by multiplying the drive current value at the reference temperature T2 calculated using Equation 2 by the temperature correction factor calculated using Equation 7 (step S35). Then, the calculation unit 13 sets the calculated corrected drive current value in the drive control unit 14 (step S36), and ends the processing operation shown in Fig. 5. Then, the drive control unit 14 supplies a drive current equivalent to the set drive current value to the VOA2. As a result, the VOA2 can ensure the set attenuation at the set temperature.

[0051] In the control device 1 of the first embodiment, the drive current value for obtaining the set attenuation at the set temperature is calculated simply by using Equation 2 and Equation 7 stored in the memory unit 12, and the calculated drive current value is set in the drive control unit 14. As a result, compared to the conventional technology, the amount of data can be reduced and complex calculation processing is not required, and the drive current value for the set attenuation at the set temperature can be calculated while correcting for fluctuations between the set temperature and the reference temperature. Furthermore, the advance preparation time for calculating the drive current value for obtaining the set attenuation in the VOA 2 can be shortened, and the calculation processing can be simplified while reducing the amount of data required. In other words, the drive current value for obtaining the set attenuation at the set temperature can be obtained while correcting for temperature dependency.

[0052] The control device 1 employs a FF (Feedforward) control method, eliminating the need for an optical monitor for FB (Feedback) control after the VOA 2. Moreover, because the control device 1 employs the FF control method, it can also solve the problem of multiple loops.

[0053] Furthermore, since the control device 1 has the temperature monitor 3 and control unit 5 installed within the module, a drive circuit is not required, making it possible to secure mounting area. In addition, the user device 50 does not need to perform the pre-measurements required for control, thereby reducing the time required for advance preparation.

[0054] For convenience of explanation, the case where the control device 1 has the built-in optical monitor 4 has been exemplified, but if the first function and the second function are stored in the storage unit 12 in advance, the optical monitor 4 becomes unnecessary.

[0055] In the control device 1 of the first embodiment, the case where the formulas 2 and 7 of the attenuation characteristics based on the reference temperature are used is exemplified. However, the attenuation characteristics are not limited to the reference temperature, and the attenuation characteristics based on the reference wavelength of the input light may be used, and an embodiment of this will be described below as the second embodiment. [Example]

[0056] 6 is a block diagram showing an example of a control device 1A according to the second embodiment. The same components as those in the control device 1 according to the first embodiment are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The control device 1 according to the first embodiment differs from the control device 1A according to the second embodiment in that it includes a control unit 5A that calculates a drive current value for a set attenuation amount using an attenuation amount characteristic based on a reference wavelength of input light.

[0057] The control unit 5A controls the VOA 2. The control unit 5A controls the VOA 2 using attenuation characteristics based on a reference wavelength of input light, which have been acquired in advance. The control unit 5A calculates a drive current value for obtaining a set attenuation at a set temperature and set wavelength based on the attenuation characteristics based on the reference wavelength, the set attenuation of the VOA 2, and the set wavelength of the input light. The control unit 5A then supplies a drive current equivalent to the calculated drive current value to the VOA 2. The user device 50 sets the set attenuation and set wavelength in the control device 1A.

[0058] The control unit 5A has a setting unit 11A, a storage unit 12A, a calculation unit 13A, and a drive control unit 14. The setting unit 11A calculates a third function and a fourth function, which are part of the attenuation amount characteristics, and stores the calculated third function and fourth function in the storage unit 12A. The third function is a mathematical expression of a quadratic curve that approximates the relationship between the drive current value for each attenuation amount of the VOA 2 at a reference wavelength, which will be described later. The fourth function is a mathematical expression that calculates a wavelength correction magnification that corrects the drive current value between the set wavelength and the reference wavelength.

[0059] The calculation unit 13A calculates the drive current value at the reference wavelength by substituting the set attenuation amount into the third function. The calculation unit 13A calculates the wavelength correction factor at the set wavelength by substituting the set wavelength into the fourth function. Furthermore, the calculation unit 13A calculates the drive current value for obtaining the set attenuation amount at the set wavelength based on the drive current value at the reference wavelength calculated using the third function and the wavelength correction factor at the set wavelength calculated using the fourth function, and sets the calculated drive current value in the drive control unit 14. The drive control unit 14 supplies a drive current corresponding to the set drive current value to the VOA2.

[0060] The optical monitor 4 is not used for FB control but is used to measure the attenuation of the VOA 2 required to calculate the attenuation characteristics.

[0061] Next, the operation of the control unit 5A that sets the third and fourth functions will be described. The optical monitor 4 sequentially measures the attenuation of the VOA2 in advance for at least three reference wavelengths: λ1 nm, λ2 nm, and λ3 nm under predetermined drive current conditions. The predetermined drive current conditions are conditions under which the VOA2 is driven at a reference temperature T2 with, for example, four drive current values: 0 mA, I1 mA, I2 mA, and I3 mA. The drive current values ​​are not limited to four, but can be changed as long as they are two or more. The reference temperature is acquired from the temperature monitor 3.

[0062] 7 is an explanatory diagram showing an example of a quadratic curve approximating the relationship between the attenuation and the drive current value for each reference wavelength. The optical monitor 4 sequentially measures the attenuation of the VOA 2 at each drive current value of 0 mA, I1 mA, I2 mA, and I3 mA at the reference wavelength λ1 under the reference temperature T2. As a result, as shown in FIG. 7, the setting unit 11A obtains a quadratic curve approximating the relationship between the attenuation at the reference wavelength λ1 and the drive current value, based on the attenuations A7, A8, and A9 that are the measurement results of the optical monitor 4 at the reference wavelength λ1. Then, the setting unit 11A obtains the drive current value I for each attenuation at the reference wavelength λ1 from the quadratic curve approximating the relationship between the attenuation at the reference wavelength λ1 and the drive current value. VOA7 Formula 8 is derived to calculate (A).

[0063]

number

[0064] The optical monitor 4 also sequentially measures the attenuation of the VOA2 at each of the drive current values ​​0 mA, I1 mA, I2 mA, and I3 mA at the reference wavelength λ2. As a result, the setting unit 11A obtains a quadratic curve approximating the relationship between the attenuation at the reference wavelength λ2 and the drive current value, based on the attenuations A7, A8, and A9 that are the measurement results of the optical monitor 4 at the reference wavelength λ2, as shown in FIG. 7. Then, the setting unit 11A obtains the drive current value I for each attenuation at the reference wavelength λ2 from the quadratic curve approximating the relationship between the attenuation at the reference wavelength λ2 and the drive current value. VOA8 Formula 9 is derived to calculate (A).

[0065]

number

[0066] Further, the optical monitor 4 sequentially measures the attenuation amounts of the VOA 2 at drive current values of 0 mA, I1 mA, I2 mA, and I3 mA at the reference wavelength λ3. As a result, as shown in FIG. 7, the setting unit 11A obtains a quadratic curve that approximates the relationship between the attenuation amount and the drive current value at the reference wavelength λ3 based on the attenuation amounts A7, A8, and A9, which are the measurement results of the optical monitor 4 at the reference wavelength λ3. Then, the setting unit 11A derives Equation 10 for calculating the drive current value I VOA9 (A) at each attenuation amount at the reference wavelength.

[0067] [Number]

[0068] By using these Equations 8 to 10, the control unit 5A can calculate the drive current value of the VOA 2 required for an arbitrary attenuation amount for each reference wavelength. However, since it is limited to any one of the reference wavelengths λ1, λ2, and λ3, there remains a problem that the drive current value of the VOA 2 cannot be calculated at a set wavelength other than the reference wavelength.

[0069] Therefore, as a solution to such a problem, the setting unit 11A normalizes the drive current values at each reference wavelength with respect to the drive current value at the reference wavelength λ2 based on the calculation results of Equations 8 to 10, using the reference wavelength λ2 as the reference wavelength. It is desirable that the magnitude relationship of the reference wavelengths is λ1 < λ2 < λ3, and it is desirable that the magnitude relationship of the arbitrary attenuation amounts is A10 < A11 < A12 [dB]. Note that the arbitrary attenuation amounts may be A10 = A7, A11 = A8, and A12 = A9 as described above and can be changed as appropriate. FIG. 8 is an explanatory diagram showing a graph in which the values obtained by normalizing the drive current values for each reference wavelength with respect to the reference wavelength λ2 are plotted.

[0070] The setting unit 11A approximates the values obtained by normalizing the drive current values for each reference wavelength with respect to the reference wavelength λ2 by a quadratic curve, and obtains Equations 11 to 13 from the quadratic curve for each approximated attenuation amount standard value. The setting unit 11A refers to the attenuation amount A10 shown in FIG. 8, and the attenuation amount standard value I for the wavelength λ at the attenuation amount A10 under the reference temperature T2nomal10 Formula 11 for calculating (λ) is derived.

[0071]

number

[0072] The setting unit 11A refers to the attenuation A11 shown in FIG. 8 and calculates the attenuation standard value I for the wavelength λ at the attenuation A11 under the reference temperature T2. nomal11 Formula 12 is derived to calculate (λ).

[0073]

number

[0074] The setting unit 11A refers to the attenuation A12 shown in FIG. 8 and calculates the attenuation standard value I for the wavelength λ at the attenuation A12 under the reference temperature T2. nomal12 Formula 13 is derived to calculate (λ).

[0075]

number

[0076] The setting unit 11A obtains the coefficients (δ1, ε1, ζ1, δ2, ε2, ζ2, δ3, ε3, ζ3) of each order from Equations 11 to 13. The setting unit 11A calculates the average values ​​of the coefficients for each order (δ=Average(δ1, δ2, δ3), ε=Average(ε1, ε2, ε3), ζ=Average(ζ1, ζ2, ζ3)). The setting unit 11A then uses these average values ​​to calculate a normalized value of the drive current value for the wavelength, i.e., a wavelength correction factor that is a correction factor for correcting the drive current value between the reference wavelength and the set wavelength. The set wavelength is the wavelength of the input light set by the user device 50. The solid line in FIG. 8 is a quadratic curve that shows the relationship between the wavelength correction factor for correcting the drive current value between the reference wavelength and the set wavelength. The setting unit 11A derives Equation 14 for calculating the wavelength correction magnification using the average values ​​of the coefficients for each order (δ=Average(δ1, δ2, δ3), ε=Average(ε1, ε2, ε3), ζ=Average(ζ1, ζ2, ζ3)).

[0077]

number

[0078] Then, the setting unit 11A stores, in the memory unit 12A, Equation 9 as a third function that calculates the drive current value for each attenuation amount at the reference wavelength λ2 and Equation 14 as a fourth function that calculates the wavelength correction magnification. That is, the memory unit 12A stores only Equation 9 and Equation 14, i.e., the coefficients of Equation 9 and Equation 14.

[0079] Next, the operation of the control unit 5A for setting the drive current value for obtaining the set attenuation of the VOA 2 at the set wavelength and reference temperature using the third and fourth functions will be described.

[0080] First, the set attenuation is, for example, the desired attenuation of the VOA 2 that the user device 50 sets in the control device 1A. The set attenuation can also be set automatically in conjunction with the optical monitor 4. The set temperature of the VOA 2 is, for example, the ambient temperature of the VOA 2 measured by the temperature monitor 3 periodically or at required timing. In other words, the calculation unit 13 acquires the set attenuation and the set temperature of the VOA 2.

[0081] The calculation unit 13A calculates the drive current value at the reference wavelength λ2 by substituting the set attenuation into Equation 9. Furthermore, the calculation unit 13A calculates a wavelength correction factor for correcting the drive current value between the reference wavelength and the set wavelength by substituting the set wavelength into Equation 14. Furthermore, the calculation unit 13A multiplies the drive current value calculated using Equation 9 by the wavelength correction factor calculated using Equation 14 to calculate the drive current value required to obtain the set attenuation at the reference temperature and the set wavelength. The calculation unit 13A sets the calculated drive current value at the reference temperature and the set wavelength in the drive control unit 14. The drive control unit 14 supplies a drive current value corresponding to the set drive current value to the VOA2. As a result, the VOA2 can obtain the set attenuation at the reference temperature and the set wavelength according to the drive current from the drive control unit 14.

[0082] 9 is a flowchart showing an example of the processing operation of the control unit 5A related to the second setting process. In FIG. 9, the setting unit 11A of the control unit 5A specifies an arbitrary reference wavelength from among a plurality of reference wavelengths at a reference temperature T2 (step S41). The reference wavelengths are, for example, λ1, λ2, and λ3. The setting unit 11A sequentially sets drive current values ​​of 0 mA, I1 mA, I2 mA, and I3 mA in the drive control unit 14 under the specified reference wavelength and at the reference temperature T2 (step S42). As a result, the drive control unit 14 sequentially supplies drive currents corresponding to the set drive current values ​​to the VOA2.

[0083] The setting unit 11A acquires the attenuation amount when the drive current is set to 0 mA, the attenuation amount A7 when the drive current is set to I1 mA, the attenuation amount A8 when the drive current is set to I2 mA, and the attenuation amount A9 when the drive current is set to I3 mA from the optical monitor 4 (step S43).

[0084] The setting unit 11A derives a third function of the specified reference wavelength from a quadratic curve that approximates the relationship between the attenuation of the specified reference wavelength and the drive current value from each attenuation amount for each drive current value (step S44). The setting unit 11A determines whether the third functions of all reference wavelengths have been derived (step S45). The third functions of all reference wavelengths are Equation 8 for reference wavelength λ1, Equation 9 for reference wavelength λ2, and Equation 10 for reference wavelength λ3.

[0085] If the third functions for all reference wavelengths have not been derived (step S45: No), the setting unit 11A determines whether or not there is an unspecified reference wavelength among the three reference wavelengths (step S46). If there is an unspecified reference wavelength (step S46: Yes), the setting unit 11A proceeds to step S41 to specify the unspecified reference wavelength.

[0086] Furthermore, when the setting unit 11A has derived the third functions for all reference wavelengths (step S45: Yes), it substitutes the arbitrary attenuation amounts A10, A11, and A12 into Equation 8, Equation 9, and Equation 10 for each reference wavelength (step S47). Then, the setting unit 11A calculates the drive current value for each reference wavelength according to the arbitrary attenuation amounts A10, A11, and A12 (step S48).

[0087] The setting unit 11A derives a quadratic curve that approximates the relationship of the drive current value to the reference wavelength λ2 from the calculated drive current value for each reference wavelength (step S49). Then, the setting unit 11A normalizes the drive current value at each reference temperature with the drive current value at the reference wavelength λ2 from the quadratic curve derived in step S49 (step S50).

[0088] The setting unit 11A derives Equation 11, Equation 12, and Equation 13 from a quadratic curve that approximates the relationship between the drive current value normalized by the drive current value of the reference wavelength λ2 (step S51). The setting unit 11A averages the coefficients for each order of Equation 11, Equation 12, and Equation 13, and derives Equation 14 as a fourth function that calculates a wavelength correction magnification for correcting the drive current value between the reference wavelength λ2 and the set wavelength (step S52).

[0089] Then, the setting unit 11A stores in the memory unit 12A Equation 9 for calculating the drive current value corresponding to the set attenuation amount of the reference wavelength λ2 and Equation 14 for calculating the wavelength correction magnification for correcting the drive current value between the reference wavelength λ2 and the set wavelength (step S53), and ends the processing operation shown in Figure 9.

[0090] Furthermore, if there is no unspecified reference wavelength (step S46: No), the setting unit 11A proceeds to step S47 to substitute an arbitrary amount of attenuation into formulas 8, 9, and 10 for each reference wavelength.

[0091] 10 is a flowchart showing an example of the processing operation of the control unit 5A related to the second calculation process. In FIG. 10, the calculation unit 13A in the control unit 5A acquires the set attenuation amount and the set wavelength (step S61). The set attenuation amount and the set wavelength are acquired from, for example, the user device 50. The calculation unit 13A acquires the set temperature from the temperature monitor 3 (step S62). The set temperature is the ambient temperature of the VOA 2 measured by the temperature monitor 3.

[0092] The calculation unit 13A calculates the drive current value at the reference wavelength λ2 by substituting the set attenuation amount into Equation 9 (step S63). Furthermore, the calculation unit 13A calculates the wavelength correction magnification by substituting the set wavelength into Equation 14 (step S64).

[0093] The calculation unit 13A calculates a corrected drive current value by multiplying the drive current value at the reference wavelength λ2 calculated using Equation 9 by the wavelength correction factor calculated using Equation 14 (step S65). Then, the calculation unit 13A sets the calculated corrected drive current value in the drive control unit 14 (step S66), and ends the processing operation shown in Fig. 10. Then, the drive control unit 14 supplies a drive current equivalent to the set drive current value to the VOA2. As a result, the VOA2 can ensure the set attenuation amount at the set wavelength.

[0094] In the control device 1A of the second embodiment, the drive current value for obtaining the set attenuation at the set wavelength is calculated simply by using Equation 9 and Equation 14 stored in the storage unit 12A, and the calculated drive current value is set in the drive control unit 14. As a result, compared to the conventional technology, the amount of data can be reduced and complex calculation processing is not required, and the drive current value for the set attenuation at the set wavelength can be calculated while correcting for the fluctuation between the set wavelength and the reference wavelength. Furthermore, the advance preparation time for calculating the drive current value for obtaining the set attenuation at the VOA 2 can be shortened, and the calculation processing can be simplified while reducing the amount of required data. In other words, the drive current value for obtaining the set attenuation at the set wavelength can be obtained while correcting for wavelength dependency.

[0095] The control device 1A employs the FF control method, which eliminates the need for an optical monitor for FB control after the VOA 2. Moreover, the control device 1A employs the FF control method, which also solves the problem of multiple loops.

[0096] Furthermore, since the control device 1A incorporates the temperature monitor 3 and control unit 5A within the module, a drive circuit is not required, making it possible to secure mounting area. In addition, the user device 50 does not need to perform the pre-measurements required for control, thereby reducing the time required for advance preparation.

[0097] For convenience of explanation, the control device 1A has been exemplified as having a built-in optical monitor 4, but if the third and fourth functions are stored in advance in the storage unit 12A, the optical monitor 4 is not necessary.

[0098] In the control device 1 of Example 1, an example is given in which Equation 2 and Equation 7 are used for the attenuation characteristics based on the reference temperature, and in the control device 1A of Example 2, an example is given in which Equation 9 and Equation 14 are used for the attenuation characteristics based on the reference wavelength. However, the present invention is not limited to these, and Equation 2 and Equation 7 based on the reference temperature and Equation 14 based on the reference wavelength may be used together, and such an embodiment will be described below as Example 3. [Example]

[0099] 11 is a block diagram showing an example of a control device 1B according to a third embodiment. The same components as those in the control device 1 (1A) according to the first and second embodiments are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The control device 1B according to the third embodiment differs from the control device 1 (1A) according to the first and second embodiments in that it includes a control unit 5B that calculates a drive current value for a set attenuation amount by using both Equation 2 and Equation 7 based on a reference temperature and Equation 14 based on a reference wavelength.

[0100] Control unit 5B has setting unit 11B, storage unit 12B, calculation unit 13B, and drive control unit 14. Setting unit 11B calculates Equation 2 and Equation 7 based on the reference temperature, and stores calculated Equation 2 as a first function and calculated Equation 7 as a second function in storage unit 12B. Setting unit 11B also calculates Equation 14 based on the reference wavelength, and stores calculated Equation 14 as a fourth function in storage unit 12B.

[0101] Next, the operation of the control unit 5B, which calculates the drive current value for obtaining the set attenuation amount at the set wavelength and set temperature using the first, second and fourth functions, will be described.

[0102] First, the set attenuation is, for example, the desired attenuation of the VOA 2 set by the user device 50. The set attenuation can also be automatically set in conjunction with the optical monitor 4. The set wavelength is, for example, the desired wavelength of the input light set by the user device 50. The set temperature is, for example, the ambient temperature of the VOA measured by the temperature monitor 3 periodically or at required timing. The calculation unit 13B acquires the set attenuation, the set wavelength, and the set temperature.

[0103] Calculation unit 13B calculates the drive current value at reference temperature T2 by substituting the set attenuation amount into Equation 2. Furthermore, calculation unit 13B calculates a temperature correction factor for correcting the drive current between the reference temperature and the set temperature by substituting the ambient temperature acquired from temperature monitor 3 as the set temperature into Equation 7. Furthermore, calculation unit 13B calculates a wavelength correction factor for correcting the drive current between the reference wavelength and the set wavelength by substituting the set wavelength into Equation 14.

[0104] The calculation unit 13B calculates the drive current value required to obtain the set attenuation at the set temperature and wavelength by multiplying the drive current value calculated by Equation 2 by the temperature correction factor calculated by Equation 7 and the wavelength correction factor calculated by Equation 14. Then, the calculation unit 13B sets the calculated drive current value in the drive control unit 14. The drive control unit 14 supplies the VOA2 with a drive current equivalent to the set drive current value.

[0105] 12 is a flowchart showing an example of the processing operation of the control unit 5B related to the third calculation process. In FIG. 12, the calculation unit 13B in the control unit 5B acquires a set attenuation amount and a set wavelength (step S71). The set attenuation amount and the set wavelength are acquired from, for example, the user device 50. The calculation unit 13B acquires a set temperature from the temperature monitor 3 (step S72).

[0106] The calculation unit 13B calculates the drive current value at the reference temperature T2 by substituting the set attenuation amount into Equation 2 (step S73). Furthermore, the calculation unit 13B calculates the temperature correction factor by substituting the set temperature into Equation 7 (step S74). Furthermore, the calculation unit 13B calculates the wavelength correction factor by substituting the set wavelength into Equation 14 (step S75).

[0107] The calculation unit 13B calculates a corrected drive current value by multiplying the drive current value at the reference temperature T2 calculated using Equation 2 by the temperature correction factor calculated using Equation 7 and the wavelength correction factor calculated using Equation 14 (step S76). Then, the calculation unit 13B sets the calculated corrected drive current value in the drive control unit 14 (step S77), and ends the processing operation shown in Fig. 12. Then, the drive control unit 14 supplies a drive current equivalent to the set drive current value to the VOA2. As a result, the VOA2 can ensure the set attenuation at the set temperature and set wavelength.

[0108] In the control device 1B of the third embodiment, the drive current value for obtaining the set attenuation at the set wavelength and set temperature is calculated simply by using Equation 2, Equation 7, and Equation 14 stored in the memory unit 12B, and the calculated drive current value is set in the drive control unit 14. As a result, compared to the conventional technology, the drive current value for the set attenuation at the set temperature and set wavelength can be calculated while correcting for variations between the set temperature and the reference temperature and variations between the set wavelength and the reference wavelength, while reducing the amount of data and requiring complex calculation processing. Furthermore, the advance preparation time for calculating the drive current value for obtaining the set attenuation in the VOA 2 can be shortened, and the calculation processing can be simplified while reducing the amount of data required. In other words, the drive current value for obtaining the set attenuation at the set temperature and set wavelength can be obtained while correcting for temperature dependency and wavelength dependency.

[0109] The control device 1B employs the FF control method, which eliminates the need for an optical monitor for FB control after the VOA 2. Moreover, the control device 1B employs the FF control method, which can also solve the problem of multiple loops.

[0110] 13 is an explanatory diagram showing an example of a combination of measurement conditions for obtaining attenuation characteristics in the control device 1B of Example 3. The setting unit 11B performs three measurements of drive current values ​​I1 mA, I2 mA, and I3 mA at the reference wavelength λ2 under the reference temperature T1. The setting unit 11B also performs three measurements of drive current values ​​I1 mA, I2 mA, and I3 mA at the reference wavelength λ2 under the reference temperature T2.

[0111] Furthermore, setting unit 11B performs three measurements of drive current values ​​I1 mA, I2 mA, and I3 mA at reference wavelength λ1 under reference temperature T2. Setting unit 11B performs three measurements of drive current values ​​I1 mA, I2 mA, and I3 mA at reference wavelength λ2 under reference temperature T2. Setting unit 11B performs three measurements of drive current values ​​I1 mA, I2 mA, and I3 mA at reference wavelength λ3 under reference temperature T2.

[0112] That is, the setting unit 11B can obtain Equation 2, Equation 7, and Equation 14 through a total of 15 measurement processes, as shown in Fig. 13. Moreover, since the order coefficients of each equation are three, and the order coefficients of the three equations are three, it is only necessary to store a total of nine coefficients in the storage unit 12B, and the amount of data can be minimized compared to the prior art.

[0113] In the control device 1B of Example 3, an example is given in which the drive current value at the reference temperature is calculated by substituting the set attenuation amount from the user device 50 into Equation 2, but this is not limited to this, and an embodiment thereof will be described below as Example 4. [Example]

[0114] 14 is a block diagram showing an example of a control device 1C according to the fourth embodiment. The same components as those in the control device 1B according to the third embodiment are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The control device 1C according to the fourth embodiment differs from the control device 1B according to the third embodiment in that the set attenuation amount acquired from the user device 50 is wavelength-corrected and the wavelength-corrected set attenuation amount is substituted into Equation 2.

[0115] Control unit 5C of control device 1C has setting unit 11C, memory unit 12C, calculation unit 13C, and drive control unit 14. Setting unit 11C calculates Equation 2 and Equation 7 based on the set temperature, and stores calculated Equation 2 as a first function and calculated Equation 7 as a second function in memory unit 12C. Setting unit 11C also calculates Equation 14 based on the set wavelength, and stores calculated Equation 14 as a fourth function in memory unit 12C.

[0116] Furthermore, the setting unit 11C calculates a fifth function and stores the calculated fifth function in the storage unit 12C. The optical monitor 4 sequentially measures the attenuation of the VOA2 at drive current values ​​of 0 mA, I1 mA, I2 mA, and I3 mA in advance at a reference temperature T2 and a reference wavelength λ2. The optical monitor 4 sequentially acquires the attenuation value at a drive current value of 0 mA, an attenuation A1 at a drive current value I1 mA, an attenuation A2 at a drive current value I2 mA, and an attenuation A3 at a drive current value I3 mA at the reference temperature T2 and the reference wavelength λ2.

[0117] Then, the setting unit 11C derives Equation 15, which calculates the attenuation for each drive current value at reference temperature T2, from a quadratic curve that approximates the relationship between the attenuation at reference temperature T2 and the drive current value from the attenuations A1, A2, and A3 for each drive current value. The setting unit 11C then stores the derived Equation 15 in the memory unit 12C as a fifth function.

[0118]

number

[0119] Next, the operation of the control unit 5C for setting the drive current value for obtaining the set attenuation amount at the set wavelength and set temperature using the first, second, fourth and fifth functions will be described.

[0120] First, the set attenuation is, for example, a desired attenuation set by the user device 50. The set wavelength is, for example, the wavelength of the input light set by the user device 50. The set temperature is, for example, the ambient temperature of the VOA 2 measured by the temperature monitor 3 periodically or at required timing. The setting unit 11C calculates the set attenuation after wavelength correction by multiplying the set attenuation by the wavelength correction factor. Therefore, the calculation unit 13C acquires the set attenuation, the set attenuation after wavelength correction, the set wavelength, and the set temperature.

[0121] The calculation unit 13C calculates the first drive current value at the reference temperature T2 by substituting the set attenuation amount after wavelength correction into Equation 2. Furthermore, the calculation unit 13C calculates the wavelength correction magnification for correcting the drive current value between the reference wavelength and the set wavelength by substituting the set wavelength into Equation 14.

[0122] The calculation unit 13C calculates the corrected second drive current value by multiplying the first drive current value at the reference temperature T2 calculated by Equation 2 by the wavelength correction factor calculated by Equation 14. The calculation unit 13C calculates the corrected attenuation amount by substituting the calculated corrected second drive current value into Equation 15.

[0123] Furthermore, calculation unit 13C calculates a third drive current value at reference temperature T2 by substituting the corrected attenuation amount into Equation 2. Furthermore, calculation unit 13C calculates a temperature correction factor for correcting the drive current between the reference temperature and the set temperature by substituting the ambient temperature as the set temperature into Equation 7. Then, calculation unit 13C multiplies the calculated third drive current value by the temperature correction factor to calculate a corrected fourth drive current value, and sets the calculated fourth drive current value in drive control unit 14.

[0124] The drive control unit 14 supplies a drive current corresponding to the fourth drive current value calculated by the calculation unit 13C to the VOA 2. As a result, the VOA 2 can obtain the set attenuation amount at the set temperature and the set wavelength according to the drive current from the drive control unit 14.

[0125] 15 is a flowchart showing an example of the processing operation of the control unit 5C related to the third setting process. In FIG. 15, the setting unit 11C of the control unit 5C sequentially sets drive current values ​​of 0 mA, I1 mA, I2 mA, and I3 mA in the drive control unit 14 at a reference temperature T2 and a reference wavelength λ2 (step S81). As a result, the drive control unit 14 sequentially supplies drive currents corresponding to the set drive current values ​​to the VOA2.

[0126] The setting unit 11C sequentially acquires from the optical monitor 4 the attenuation amount when the drive current is set to 0 mA, the attenuation amount A1 when the drive current is set to I1 mA, the attenuation amount A2 when the drive current is set to I2 mA, and the attenuation amount A3 when the drive current is set to I3 mA (step S82).

[0127] The setting unit 11C derives Equation 15, which is a fifth function for the reference temperature T2, from a quadratic curve that approximates the relationship between the attenuation of the reference temperature T2 and the drive current value from each attenuation amount for each drive current value (step S83). The setting unit 11C stores Equation 15 for the reference temperature T2 thus derived in the storage unit 12C (step S84), and ends the processing operation shown in FIG.

[0128] 16 is a flowchart showing an example of the processing operation of the control unit 5C related to the fourth calculation process. In FIG. 16, the calculation unit 13C in the control unit 5C acquires a set attenuation amount and a set wavelength (step S91). The set attenuation amount and the set wavelength are acquired from, for example, the user device 50. The calculation unit 13C acquires a set temperature from the temperature monitor 3 (step S92).

[0129] The calculation unit 13C calculates the set attenuation after wavelength correction by multiplying the set attenuation by the wavelength correction factor (step S93). The calculation unit 13C calculates the first drive current value at the reference temperature T2 by substituting the set attenuation after wavelength correction into Equation 2 (step S94). Furthermore, the calculation unit 13C calculates the wavelength correction factor by substituting the set wavelength into Equation 14 (step S95).

[0130] The calculation unit 13C calculates the corrected second driving current value by multiplying the first driving current value at the reference temperature T2 calculated using Equation 2 by the temperature correction factor calculated using Equation 7 and the wavelength correction factor calculated using Equation 14 (step S96).

[0131] The calculation unit 13C calculates the corrected attenuation amount by substituting the calculated corrected second drive current value into Equation 15 (step S97). The calculation unit 13C calculates the corrected attenuation amount by substituting the corrected attenuation amount calculated using Equation 15 into Equation 2 (step S98).

[0132] The calculation unit 13C calculates the temperature correction factor by substituting the set temperature into Equation 7 (step S99). The calculation unit 13C calculates a corrected fourth drive current value by multiplying the third drive current value at the reference temperature T2 calculated using Equation 2 by the temperature correction factor calculated using Equation 7 (step S100). The calculation unit 13C then sets the calculated corrected fourth drive current value in the drive control unit 14 (step S101), and ends the processing operation shown in FIG. 16. The drive control unit 14 then supplies a drive current equivalent to the set fourth drive current value to the VOA2. As a result, the VOA2 can ensure the set attenuation at the set temperature and wavelength.

[0133] In the control device 1C of the fourth embodiment, the drive current value for obtaining the set attenuation at the set wavelength and set temperature is calculated simply by using Equations 2, 7, 14, and 15 stored in the memory unit 12C, and the calculated drive current value is set in the drive control unit 14. As a result, compared to the conventional technology, the amount of data is reduced, complex calculation processing is unnecessary, and the drive current value for the set attenuation at the set temperature and set wavelength can be calculated while correcting for fluctuations between the set temperature and the reference temperature and between the set wavelength and the reference wavelength. Furthermore, the advance preparation time for calculating the drive current value for obtaining the set attenuation in the VOA 2 can be shortened, and the calculation processing can be simplified while reducing the amount of data required. In other words, the drive current value for obtaining the set attenuation at the set temperature and set wavelength can be obtained while correcting for temperature dependency and wavelength dependency.

[0134] The control device 1C employs the FF control method, which eliminates the need for an optical monitor for FB control after the VOA 2. Moreover, the control device 1C employs the FF control method, which also eliminates the problem of multiple loops.

[0135] In the fourth embodiment, the control device 1C executes all the calculation processes using the set wavelength and set attenuation amount acquired from the user device 50. However, a part of the calculation processes may be shared by, for example, the user device 50A, and such an embodiment will be described below as a fifth embodiment. [Example]

[0136] 17 is a block diagram showing an example of a control device 1D according to a fifth embodiment. The same components as those of the control device 1C according to the fourth embodiment are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The control device 1D according to the fifth embodiment differs from the control device 1C according to the fourth embodiment in that part of the calculation processing of the control device 1D is shared with the user device 50A.

[0137] The control unit 5D of the control device 1D has a setting unit 11D, a memory unit 12D, a calculation unit 13D, and a drive control unit 14. The setting unit 11D calculates Equation 2 and Equation 7 based on the set temperature, and stores the calculated Equation 2 as a first function and the calculated Equation 7 as a second function in the memory unit 12D. The setting unit 11D also calculates Equation 14 based on the set wavelength, and stores the calculated Equation 14 as a fourth function in the memory unit 12C. The setting unit 11D also stores the derived Equation 15 as a fifth function in the memory unit 12D.

[0138] Next, an operation for setting a drive current value for obtaining a set attenuation amount at a set wavelength and a set temperature using the first, second, fourth, and fifth functions will be described.

[0139] First, the set attenuation is, for example, a desired attenuation set by the user device 50A. The set wavelength is, for example, the wavelength of the input light set by the user device 50A. The set temperature is, for example, the ambient temperature of the VOA 2 measured by the temperature monitor 3 periodically or at required timing. The user device 50A obtains Formulas 2, 14, and 15 from the control unit 5D.

[0140] The user device 50A calculates the wavelength-corrected set attenuation by multiplying the set attenuation by the wavelength correction factor. The user device 50A calculates the first drive current value at the reference temperature T2 by substituting the wavelength-corrected set attenuation into Equation 2. Furthermore, the user device 50A calculates the wavelength correction factor for correcting the drive current value between the reference wavelength and the set wavelength by substituting the set wavelength into Equation 14.

[0141] The user device 50A calculates a corrected second driving current value by multiplying the first driving current value at the reference temperature T2 calculated using Equation 2 by the wavelength correction factor calculated using Equation 14. The user device 50A calculates a corrected attenuation amount by substituting the calculated corrected second driving current value into Equation 15. The user device 50A then notifies the controller 5D of the calculated corrected attenuation amount.

[0142] Furthermore, calculation unit 13C calculates a third drive current value at reference temperature T2 by substituting the corrected attenuation amount into Equation 2. Furthermore, calculation unit 13C calculates a temperature correction factor for correcting the drive current between the reference temperature and the set temperature by substituting the ambient temperature as the set temperature into Equation 7. Then, calculation unit 13C multiplies the calculated third drive current value by the temperature correction factor to calculate a corrected fourth drive current value, and sets the calculated fourth drive current value in drive control unit 14.

[0143] The drive control unit 14 supplies a drive current corresponding to the fourth drive current value calculated by the calculation unit 13C to the VOA 2. As a result, the VOA 2 can obtain the set attenuation amount at the set temperature and the set wavelength according to the drive current from the drive control unit 14.

[0144] 18 is a flowchart showing an example of the processing operation of the user device 50A related to the user-side calculation process. In FIG. 18, the user device 50A acquires Formulas 2, 14, and 15 from the control unit 5D (step S111). The user device 50A calculates the set attenuation amount after wavelength correction by multiplying the set attenuation amount by the wavelength correction magnification (step S112).

[0145] The user device 50A calculates the first drive current value at the reference temperature T2 by substituting the set attenuation amount after wavelength correction into Equation 2 (step S113). Furthermore, the user device 50A calculates the wavelength correction magnification by substituting the set wavelength into Equation 14 (step S114).

[0146] The user device 50A calculates a corrected second driving current value by multiplying the first driving current value at the reference temperature T2 calculated using Equation 2 by the temperature correction factor calculated using Equation 7 and the wavelength correction factor calculated using Equation 14 (step S115).

[0147] The user device 50A calculates the corrected attenuation by substituting the calculated corrected second drive current value into Equation 15 (step S116). The user device 50A notifies the controller 5D of the calculated corrected attenuation (step S117), and ends the processing operation shown in FIG.

[0148] 19 is a flowchart showing an example of the processing operation of the control unit 5D related to the fifth calculation process. In FIG. 19, the calculation unit 13D acquires the set temperature from the temperature monitor 3 (step S121). The calculation unit 13D calculates the third drive current value at the reference temperature T2 by substituting the corrected attenuation acquired from the user device 50A into Equation 2 (step S122).

[0149] The calculation unit 13D calculates the temperature correction factor by substituting the set temperature into Equation 7 (step S123). The calculation unit 13D calculates a corrected fourth drive current value by multiplying the third drive current value at the reference temperature T2 calculated using Equation 2 by the temperature correction factor calculated using Equation 7 (step S124). The calculation unit 13D then sets the calculated corrected fourth drive current value in the drive control unit 14 (step S125), and ends the processing operation shown in FIG. 19. The drive control unit 14 then supplies a drive current equivalent to the set fourth drive current value to the VOA2. As a result, the VOA2 can ensure the set attenuation at the set temperature and wavelength.

[0150] In the control device 1D of the fifth embodiment, the drive current value for obtaining the set attenuation at the set wavelength and set temperature is calculated simply by using Equations 2, 7, 14, and 15 stored in the memory unit 12C, and the calculated drive current value is set in the drive control unit 14. As a result, compared to the conventional technology, the amount of data is reduced, complex calculation processing is unnecessary, and the drive current value for the set attenuation at the set temperature and set wavelength can be calculated while correcting for fluctuations between the set temperature and the reference temperature and between the set wavelength and the reference wavelength. Furthermore, the advance preparation time for calculating the drive current value for obtaining the set attenuation in the VOA 2 can be shortened, and the calculation processing can be simplified while reducing the amount of data required. In other words, the drive current value for obtaining the set attenuation at the set temperature and set wavelength can be obtained while correcting for temperature dependency and wavelength dependency.

[0151] The user device 50A executes the calculations of the first drive current value calculated using Equation 2, the wavelength correction factor calculated using Equation 14, the second drive current value calculated using Equation 2, and the corrected attenuation amount calculated using Equation 15. As a result, the processing load imposed on the control device 1D for the calculations can be significantly reduced.

[0152] The control device 1D employs the FF control method, which eliminates the need for an optical monitor for FB control after the VOA 2. Moreover, the control device 1D employs the FF control method, which also solves the problem of multiple loops.

[0153] FIG. 20 is an explanatory diagram illustrating an example of an optical transceiver 70 according to this embodiment. The optical transceiver 70 shown in FIG. 20 is connected to an output optical fiber and an input optical fiber. The optical transceiver 70 includes a DSP (Digital Signal Processor) 72 and an optical transmitter / receiver 73. The optical transmitter / receiver 73 includes an optical transmitter 73A and an optical receiver 73B. The DSP 72 is an electrical component that performs digital signal processing. For example, the DSP 72 performs processing such as encoding transmission data, generates an electrical signal containing the transmission data, and outputs the generated electrical signal to the optical transmitter 73A. The DSP 72 also acquires an electrical signal containing reception data from the optical receiver 73B and performs processing such as decoding the acquired electrical signal to obtain the reception data.

[0154] The optical transmitter 73A has an optical modulator element 73A1 that modulates supplied light with an electrical signal output from the DSP 72, and outputs the transmission light modulated by the electrical signal to an optical fiber. The optical modulator element 73A1 has a built-in control device.

[0155] The optical receiver 73B has an optical receiver element 73B1 that receives an optical signal from an optical fiber, demodulates the received light using the supplied light, converts the demodulated received light into an electrical signal, and outputs the converted electrical signal to the DSP 72. The optical receiver element 73B1 has a built-in control device.

[0156] The control device in the optical transceiver 70 includes a variable attenuator that attenuates input light, a temperature monitor that measures the ambient temperature of the variable attenuator, and a control unit that controls the variable attenuator. The control unit includes a memory unit, a calculation unit, and a drive control unit. The memory unit stores a first function that approximates the relationship between the drive current value for each attenuation of the variable attenuator at a reference temperature and a second function that calculates a temperature correction factor that corrects the drive current value between the ambient temperature and the reference temperature. The calculation unit calculates the drive current value at the reference temperature by substituting a set attenuation into the first function, and calculates the temperature correction factor at the ambient temperature by substituting the current ambient temperature into the second function. The calculation unit calculates the drive current value to obtain the set attenuation at the ambient temperature based on the drive current value at the reference temperature calculated using the first function and the temperature correction factor at the ambient temperature calculated using the second function. The drive control unit drives and controls the variable attenuator based on the drive current value calculated by the calculation unit. As a result, the drive current value for the set attenuation amount at the set temperature can be calculated while correcting for the fluctuation between the set temperature and the reference temperature.

[0157] For convenience of explanation, the optical transceiver 70 has been illustrated as having an optical transmitter 73A and an optical receiver 73B built in, but the optical transceiver 70 may have either the optical transmitter 73A or the optical receiver 73B built in. For example, the control device may be applied to the optical transceiver 70 having the optical receiver 73B built in, and modifications can be made as appropriate.

[0158] Furthermore, the components of each unit shown in the figure do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0159] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or MCU (Micro Controller Unit)). Needless to say, the various processing functions may be executed in whole or in part on a program analyzed and executed by a CPU (or a microcomputer such as an MPU or MCU), or on hardware using wired logic. [Explanation of symbols]

[0160] 1. Control device 2 VOA 3 Temperature Monitor 5. Control section 11 Setting section 12 Storage section 13 Calculation section 14 Drive control unit

Claims

1. a variable attenuator for attenuating input light, a temperature monitor for measuring an ambient temperature of the variable attenuator, and a control unit for controlling the variable attenuator; The control unit a storage unit that stores a first function that approximates the relationship between the drive current value for each attenuation amount of the variable attenuator at a reference temperature, and a second function that calculates a temperature correction factor that corrects the drive current value between the ambient temperature and the reference temperature; a calculation unit that calculates a drive current value at the reference temperature by substituting a set attenuation amount into the first function, and calculates a temperature correction factor at the ambient temperature by substituting a current ambient temperature into the second function, and calculates a drive current value for obtaining the set attenuation amount at the ambient temperature based on the drive current value at the reference temperature calculated using the first function and the temperature correction factor at the ambient temperature calculated using the second function; a drive control unit that controls the drive of the variable attenuator based on the drive current value calculated by the calculation unit; A control device comprising:

2. The storage unit a third function that approximates the relationship between the drive current value for each attenuation amount of the variable attenuator at a reference wavelength, and a fourth function that calculates a wavelength correction factor for correcting the drive current value between a set wavelength and the reference wavelength, The calculation unit 2. The control device according to claim 1, wherein the control device calculates a drive current value at the reference temperature by substituting the set attenuation amount into the first function, calculates a temperature correction factor at the ambient temperature by substituting the current ambient temperature into the second function, and calculates a wavelength correction factor at the set wavelength by substituting the set wavelength into the fourth function, and calculates a drive current value for obtaining the set attenuation amount at the ambient temperature and the set wavelength based on the drive current value at the reference temperature calculated using the first function, the temperature correction factor at the ambient temperature calculated using the second function, and the wavelength correction factor at the set wavelength calculated using the fourth function.

3. 2. The control device according to claim 1, further comprising a setting unit that obtains the first function from a plurality of quadratic functions that approximate a relationship between a drive current value for each attenuation amount of the variable attenuator for each different reference temperature.

4. The setting unit 4. The control device according to claim 3, wherein coefficients of each order of a plurality of quadratic functions that approximate the relationship between the drive current value for each attenuation amount of the variable attenuator for each reference temperature are averaged, and a quadratic function using the averaged coefficients is obtained as the second function.

5. 3. The control device according to claim 2, further comprising a setting unit that obtains the third function from a plurality of quadratic functions that approximate the relationship between the drive current value for each attenuation amount of the variable attenuator for each different reference wavelength.

6. The setting unit 6. The control device according to claim 5, wherein coefficients of each order of a plurality of quadratic functions that approximate the relationship between the drive current value for each attenuation amount of the variable attenuator for each reference wavelength are averaged, and a quadratic function using the averaged coefficients is obtained as the fourth function.

7. The variable attenuator 2. The control device according to claim 1, wherein the control device is an electric field absorption type variable attenuator that controls the amount of attenuation in accordance with a drive current corresponding to the drive current value.

8. a setting unit that obtains a fifth function from a plurality of quadratic functions that approximate a relationship between a drive current value for each attenuation amount of the variable attenuator for each reference temperature; The calculation unit 3. The control device according to claim 2, further comprising: a drive current value at the reference temperature calculated by substituting the set attenuation amount into the first function; a temperature correction factor at the ambient temperature calculated by substituting the current ambient temperature into the second function; a wavelength correction factor at the set wavelength calculated by substituting the set wavelength into the fourth function; a corrected drive current value calculated based on the drive current value at the reference temperature calculated by the first function and the wavelength correction factor at the set wavelength calculated by the fourth function; a corrected attenuation value calculated by substituting the calculated corrected drive current value into the fifth function; a drive current value at the reference temperature calculated by substituting the corrected attenuation amount into the first function; and a drive current value for obtaining the set attenuation amount at the ambient temperature and the set wavelength calculated by multiplying the calculated drive current value at the reference temperature by the temperature correction factor.

9. a variable attenuator for attenuating input light, a temperature monitor for measuring an ambient temperature of the variable attenuator, and a control unit for controlling the variable attenuator; The control unit a storage unit that stores a first function that approximates the relationship between the drive current value for each attenuation amount of the variable attenuator at a reference wavelength, and a second function that calculates a wavelength correction factor that corrects the drive current value between a set wavelength and the reference wavelength; a calculation unit that calculates a drive current value at the reference wavelength by substituting a set attenuation amount into the first function, and calculates a wavelength correction factor at the set wavelength by substituting the set wavelength into the second function, and calculates a drive current value for obtaining the set value of the attenuation amount at the set wavelength based on the drive current value at the reference wavelength calculated using the first function and the wavelength correction factor at the set wavelength calculated using the second function; a drive control unit that controls the drive of the variable attenuator based on the drive current value calculated by the calculation unit; A control device comprising:

10. An optical receiver including an optical receiver element that converts received signal light into an electrical signal, The optical receiver element comprises: a variable attenuator for attenuating input light, a temperature monitor for measuring an ambient temperature of the variable attenuator, and a control unit for controlling the variable attenuator; The control unit a storage unit that stores a first function that approximates the relationship between the drive current value for each attenuation amount of the variable attenuator at a reference temperature, and a second function that calculates a temperature correction factor that corrects the drive current value between the ambient temperature and the reference temperature; a calculation unit that calculates a drive current value at the reference temperature by substituting a set attenuation amount into the first function, and calculates a temperature correction factor at the ambient temperature by substituting a current ambient temperature into the second function, and calculates a drive current value for obtaining the set attenuation amount at the ambient temperature based on the drive current value at the reference temperature calculated using the first function and the temperature correction factor at the ambient temperature calculated using the second function; a drive control unit that controls the drive of the variable attenuator based on the drive current value calculated by the calculation unit; An optical receiver comprising:

11. An optical transmitter including an optical modulator element that modulates guided light in response to an electrical signal, The optical modulator element comprises: a variable attenuator for attenuating input light, a temperature monitor for measuring an ambient temperature of the variable attenuator, and a control unit for controlling the variable attenuator; The control unit a storage unit that stores a first function that approximates the relationship between the drive current value for each attenuation amount of the variable attenuator at a reference temperature, and a second function that calculates a temperature correction factor that corrects the drive current value between the ambient temperature and the reference temperature; a calculation unit that calculates a drive current value at the reference temperature by substituting a set attenuation amount into the first function, and calculates a temperature correction factor at the ambient temperature by substituting a current ambient temperature into the second function, and calculates a drive current value for obtaining the set attenuation amount at the ambient temperature based on the drive current value at the reference temperature calculated using the first function and the temperature correction factor at the ambient temperature calculated using the second function; a drive control unit that controls the drive of the variable attenuator based on the drive current value calculated by the calculation unit; An optical transmitter comprising:

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