JP6542923B1 - Optical signal control device and optical signal control method - Google Patents

Abstract

An optical signal control device capable of accurately estimating the signal strength of a variable optical attenuator while reducing the preparation time and data amount in advance.
A variable light signal adjustment unit, a monitor unit monitoring the light signal intensity of the variable light signal adjustment unit, a correction unit correcting the light signal intensity monitored by the monitor unit, and adjustment of the variable light signal adjustment unit And an optical signal adjustment unit that calculates a value. The correction unit calculates the reference light reception sensitivity of the monitor unit at at least two reference temperatures using the sensitivity characteristic for the wavelength of the light reception sensitivity of the monitor unit approximated using the light reception sensitivity of the monitor unit at a predetermined wavelength and temperature. Correction using the reference light reception sensitivity to calculate the light reception sensitivity at the wavelength of the light signal and the temperature of the monitor unit, and using the light reception sensitivity at the wavelength of the light signal and the temperature of the monitor unit to correct the monitored light signal intensity The value is output to the light signal adjustment unit. The light signal adjustment unit calculates the adjustment value of the variable light signal adjustment unit using the correction value and the predetermined desired value, and outputs the adjustment value to the variable light signal adjustment unit.
[Selected figure] Figure 4

Description

  The present invention relates to an optical signal control apparatus and an optical signal control method for controlling the intensity of an optical signal to be transmitted and received in optical communication.

  In digital coherent optical communication, distortion of the signal generated in the transmission path is compensated by digital signal processing to enable large-capacity transmission of several tens of Gbit / s or more, thereby reducing the number of relays in the middle of transmission Long distance transmission is realized. Further, as to the signal modulation method, not only QPSK but also high multi-level modulation such as 16 QAM and 256 QAM can be applied, so that the transmission rate can be greatly increased.

  Further, X polarization and Y polarization can be used as means for increasing the capacity. By dividing the data signal into two, X polarization and Y polarization, combining polarization of the optical signals modulated by the X polarization and Y polarization signals, and transmitting them through one optical fiber , The transmission rate can be doubled. Here, when the optical signal strengths of the X polarization signal and the Y polarization signal are not well balanced, noise signals other than the desired main signal may remain at the time of polarization synthesis, and these signals are received on the receiving side. In order to restore efficiently, it is necessary to adjust the signal strength of the optical signal of each polarization on the transmission side.

  A variable optical attenuator (VOA: Variable Optical Attenuator) is known as an optical device for adjusting the signal strength of an optical signal. As a typical variable optical attenuator, there is one using a PLC type Mach-Zehnder interferometer in which a phase shifter is added to an optical waveguide. In the variable optical attenuator using this PLC type Mach-Zehnder interferometer, the amount of light attenuation can be adjusted to a desired value by the amount of adjustment to the phase shifter.

  Here, as a method of updating the adjustment amount of the variable optical attenuator, a feedback control method in which the adjustment amount of the variable optical attenuator is updated based on the difference between the desired value of the variable optical attenuator output and the current value is generally used. Are used in Generally, variable optical attenuators have non-linear control characteristics, and various methods have been proposed as methods of controlling the intensity of an optical signal to obtain a stable response (see, for example, Patent Documents 1 and 2). .

JP 2008-216755 A JP 2009-244351

  Here, in the conventional method of controlling the intensity of the optical signal, the current value of the variable optical attenuator output is detected by monitoring the output of the variable optical attenuator by a photo detector (PD: Photo Detector) or the like. Ru. Since the light reception sensitivity of this light detector changes depending on the wavelength and temperature, it is not possible to monitor the accurate current value, and it is not possible to calculate the accurate adjustment amount in the variable light attenuator for obtaining the desired light signal intensity. There was a problem that. In addition, although it is possible to estimate the accurate signal strength in the variable optical attenuator using the measured value of the output of the variable optical attenuator measured in advance, in that case, a huge amount of actually measured values is obtained in advance. There is a problem that it is necessary to store acquired data in a memory, it takes a lot of time for preparation in advance, and the apparatus is also upsized.

  The present invention has been made to solve the problems as described above, and reduces the preparation time and data amount in advance when calculating the adjustment amount for obtaining the desired light signal intensity in the variable optical attenuator. It is an object of the present invention to provide an optical signal control apparatus and an optical signal control method capable of accurately estimating the signal strength of a variable optical attenuator.

  In order to solve the problems as described above, an optical signal control apparatus according to the present invention includes: a variable optical signal adjustment unit; a monitor unit that monitors the optical signal intensity of an optical signal output from the variable optical signal adjustment unit; A correction unit that corrects the optical signal intensity of the optical signal monitored by the monitor unit, and an optical signal adjustment unit that calculates an adjustment value of the variable optical signal adjustment unit, the correction unit having a predetermined wavelength and temperature A reference sensitivity calculation unit that calculates reference light reception sensitivities of the monitor unit at at least two reference temperatures using sensitivity characteristics of the light reception sensitivity of the monitor unit with the wavelength approximated by using the light reception sensitivity of the monitor unit; An interpolation / extrapolation unit that calculates the light reception sensitivity at the temperature of the light signal and the wavelength of the light signal by using the reference light reception sensitivity by interpolation or extrapolation, and the wavelength of the light signal and the monitor unit of A correction value for correcting the light signal intensity monitored by the monitor unit using the light reception sensitivity at the time of the light signal adjustment unit, and the light signal adjustment unit is configured to output a correction value with the correction value. The adjustment value of the variable light signal adjustment unit is calculated using the desired value, and is output to the variable light signal adjustment unit.

  The reference sensitivity calculation unit approximates the sensitivity characteristic of the light reception sensitivity of the monitor unit with respect to the wavelength by a quadratic curve, and uses a quadratic function representing the quadratic curve to reference light reception at the at least two reference temperatures. The sensitivity is calculated, and the interpolation / extrapolation unit may calculate the light reception sensitivity at the wavelength of the light signal and the temperature of the monitor unit by linear approximation using the reference light reception sensitivity at the at least two reference temperatures. Good.

  Further, the quadratic curve is expressed by using a constant of a quadratic function obtained by using the light receiving sensitivity of the monitor unit measured in advance, and the reference sensitivity calculating unit is configured to calculate the at least three reference temperatures. The constant of the quadratic function may be stored.

  The reference sensitivity calculation unit approximates the sensitivity characteristic of the light reception sensitivity of the monitor unit with respect to the wavelength by a quadratic curve for each of the X polarization signal and the Y polarization signal of the optical signal, and the X polarization signal The deviation between the sensitivity characteristic of the X polarization signal and the sensitivity characteristic of the Y polarization signal to a quadratic function representing a quadratic curve approximating the sensitivity characteristic of one of the Y polarization signal and the Y polarization signal It may be multiplied by a quadratic function that represents a quadratic curve for adjustment.

  The reference sensitivity calculation unit approximates the sensitivity characteristic of the light reception sensitivity of the predetermined representative monitor unit with respect to the wavelength by a first quadratic curve, and the sensitivity characteristic of the light reception sensitivity of the monitor unit with respect to the wavelength is the first characteristic. The reference light receiving sensitivities at the at least two reference temperatures are approximated using a quadratic function which is approximated by a second quadratic curve expressed by multiplying the quadratic curve by the adjustment factor, and which represents the second quadratic curve. It may be calculated.

  Further, the first quadratic curve is expressed using a constant of a quadratic function obtained using the light receiving sensitivity of the monitor unit measured in advance, and the reference sensitivity calculating unit is configured to receive at least three reference temperatures. The constant of the quadratic function in may be stored.

  The reference sensitivity calculation unit may set sensitivity characteristics of the light reception sensitivity of the monitor unit with respect to the wavelength and adjustment coefficients of the first quadratic curve for each of the X polarization signal and the Y polarization signal of the optical signal. The sensitivity characteristic of the X polarization signal and the Y polarization signal are approximated by a second quadratic curve represented by multiplying and the adjustment coefficient of either one of the X polarization signal and the Y polarization signal The second curve may be multiplied by a quadratic function that represents a quadratic curve for adjustment to reduce the deviation between the sensitivity characteristics of.

  In order to solve the problems as described above, according to the optical signal control method of the present invention, a variable optical signal adjustment unit, a monitor unit that monitors the optical signal intensity of the optical signal output from the variable optical signal adjustment unit, A method of controlling an optical signal in an optical signal control device, comprising: a correction unit that corrects an optical signal intensity of an optical signal monitored by a monitor unit; and an optical signal adjustment unit that calculates an adjustment value of the variable optical signal adjustment unit. The monitor unit monitors the light signal intensity of the light signal output from the variable light signal adjustment unit; and the correction unit approximates the light reception of the monitor unit using the light reception sensitivity of the monitor unit. Calculating the reference light reception sensitivity of the monitor unit at at least two reference temperatures using the sensitivity characteristics for the wavelength of the sensitivity; and using the reference light reception sensitivity to determine the wavelength of the optical signal and the temperature of the monitor unit. Calculating the light reception sensitivity by interpolation or extrapolation, and using the light reception sensitivity at the wavelength of the light signal and the temperature of the monitor unit, a correction value for correcting the light signal intensity monitored by the monitor unit. The step of outputting to the light signal adjusting portion; the step of the light signal adjusting portion calculating the adjustment value of the variable light signal adjusting portion using the correction value and a predetermined desired value; and the variable light signal adjusting portion Outputting the adjustment value of the variable light signal adjustment unit to the variable light signal adjustment unit.

  According to the present invention, the signal strength of the variable optical attenuator is accurately estimated while reducing the preparation time and data amount in advance when calculating the adjustment amount for obtaining the desired signal strength in the variable optical attenuator. An optical signal control apparatus and an optical signal control method that can be

FIG. 1 is a view showing an example of the configuration of an optical transmitter provided with an optical signal control apparatus according to an embodiment of the present invention. FIG. 2 is a view showing an example of the configuration of an optical receiver provided with the optical signal control apparatus according to the embodiment of the present invention. FIG. 3 is a diagram showing sensitivity characteristics of the monitor unit of the optical signal control device according to the embodiment of the present invention. FIG. 4 is a diagram showing a configuration example of the optical signal control device according to the embodiment of the present invention. FIG. 5 is a diagram showing a configuration example of the optical signal control device according to the first embodiment of the present invention. FIG. 6 is an operation flowchart of the optical signal control apparatus according to the first embodiment of the present invention. FIG. 7 is a diagram for explaining the operation of the optical signal control apparatus according to the first embodiment of the present invention. FIG. 8 is a diagram for explaining a method of approximating sensitivity characteristics according to the first embodiment of the present invention. FIG. 9 is a diagram showing an example of the configuration of an optical signal control apparatus according to a second embodiment of the present invention. FIG. 10 is an operation flowchart of the optical signal control apparatus according to the second embodiment of the present invention. FIG. 11 is a diagram for explaining the operation of the optical signal control apparatus according to the second embodiment of the present invention. FIG. 12 is a diagram for explaining a method of obtaining the constant of the adjustment quadratic curve according to the second embodiment of the present invention. FIG. 13 is a view showing an example of the configuration of an optical signal control apparatus according to a third embodiment of the present invention. FIG. 14 is an operation flowchart of the optical signal control apparatus according to the third embodiment of the present invention. FIG. 15 is a diagram for explaining the operation of the optical signal control apparatus according to the third embodiment of the present invention. FIG. 16 is a diagram for explaining the operation using the adjustment coefficient according to the third embodiment of the present invention. FIG. 17 is a diagram for describing a method of approximating sensitivity characteristics of a representative individual according to the third embodiment of the present invention. FIG. 18 is a diagram for explaining a method of obtaining an adjustment coefficient according to the third embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing an example of the configuration of an optical transmitter provided with an optical signal control apparatus according to an embodiment of the present invention. The input signal input to the optical transmitter 1 is subjected to signal processing such as error correction coding in the transmission signal processing unit 4 and separated into an X polarization signal and a Y polarization signal. The respective signals of the X polarization signal and the Y polarization signal are represented by a horizontal (InPhase) signal and a quadrature (Quadrature) signal, and tuners as local signals in the modulation units (6-1, 6-2) The light signal of a bull laser diode (TLD: Tunable Laser Diode) 70-1 is converted into an optical signal by modulation. The modulated signal in the X polarization and the modulated signal in the Y polarization are supplied to the optical signal control apparatus 10, and are optical signals by the variable optical attenuator (VOA) (20-1, 20-2) which is a variable optical signal adjustment unit. After being adjusted in signal strength, they are polarization-combined and supplied to the optical fiber 3.

  In the optical signal control device 1, modulated signals in each polarization are polarization-combined by polarization combining 50 after the signal strength of the optical signal is adjusted by the VOAs (20-1, 20-2). The optical signal control device 10 controls the adjustment values of the monitor units (30-1, 30-2) that monitor the output of the VOAs (20-1, 20-2) and the VOAs (20-1, 20-2). A control unit (40-1, 40-2) is provided, and in the control unit (40-1, 40-2), a difference between an output value of the monitor unit (30-1, 30-2) and a predetermined desired value Adjust VOA (20-1, 20-2) so that becomes zero.

  Here, the light receiving sensitivity of the monitor unit (30-1, 30-2) changes depending on the wavelength of the input signal and the temperature of the monitor unit, and the characteristics thereof vary depending on each monitor unit, so VOA (20-1) , 20-2) control the adjustment value of the VOA (20-1, 20-2) so that the desired value does not depend on the wavelength, temperature, or individual. Furthermore, the VOA can also be controlled so that the ratio of the optical signal strength on the X polarization side to the Y polarization side becomes a desired ratio.

  Although a variable optical attenuator (VOA) is shown here as a variable optical signal adjustment unit for adjusting the intensity of an optical signal, any device may be applicable as long as it is an apparatus for adjusting the optical signal intensity.

  FIG. 2 is a view showing an example of the configuration of an optical receiver provided with the optical signal control apparatus according to the embodiment of the present invention. The optical signal received via the optical fiber 3 is supplied to the optical signal control device 10 and is separated into an X polarization signal and a Y polarization signal by the polarization separation circuit 60. The signal strength of each polarization signal is adjusted by the variable optical attenuator (VOA) (20-3, 20-4) so that the demodulation unit (7-1, 7-2) in the subsequent stage can perform efficient demodulation. Be done.

  In the demodulators (7-1, 7-2), each of the X polarization signal and the Y polarization signal is converted into an electric signal, and a horizontal (InPhase) signal and a quadrature (Quadrature) are extracted. The demodulated X polarization signal and Y polarization signal are supplied to the reception signal processing unit 5, and distortion and the like generated on the transmission path are compensated. The control method of the signal strength in the optical signal control apparatus 10 is the same as the control method on the transmission side.

  In the following description, the optical signal control apparatus on the transmission side will be described, but the same control method can be applied to the optical signal control apparatus on the reception side.

  FIG. 3 is a diagram showing sensitivity characteristics of the monitor unit of the optical signal control device according to the embodiment of the present invention. The horizontal axis is wavelength [nm], and the vertical axis is light receiving sensitivity [A / W]. The monitor unit configured by the light detector receives the optical signal power [W], and outputs a current or voltage corresponding thereto. The unit of reception sensitivity in the case where current is output is [A / W], but in the case of outputting a voltage, it can also be expressed in units of [V / W]. The characteristics in FIG. 3 are obtained by measuring the wavelength dependency of the reception sensitivity of the X polarization signal at a temperature of 0.degree.

  The example of FIG. 3 shows the result of measuring the reception sensitivity in seven devices of the individual a to the individual g at five wavelengths. The characteristics of the light receiving sensitivity with respect to the wavelength in each individual exhibit the characteristics of a mountain with respect to the wavelength, but the characteristics are different for each individual, and the wavelength at which the maximum light receiving sensitivity is obtained is also different. Although not shown, it is known that different sensitivity characteristics can be obtained for each individual even when the temperature is changed for the same wavelength.

  As described above, when the output of the variable optical attenuator is monitored by the monitor unit, the output of the monitor unit fluctuates depending on the wavelength and temperature of the optical signal, and the sensitivity characteristic also differs depending on each individual constituting the monitor unit. It will be. Furthermore, the sensitivity characteristics include the dispersion of the branching ratio from the variable optical attenuator to the monitor unit. In the present invention, the adjustment value of the variable optical attenuator is controlled so that the output of the variable optical attenuator becomes a desired value independent of the wavelength, temperature, individual, and branching ratio to the monitor.

  FIG. 4 is a diagram showing a configuration example of the optical signal control device according to the embodiment of the present invention. FIG. 4 shows a configuration example of the optical signal control apparatus 10 on the transmission side, and the control units (40-1 and 40-2) of the optical signal control apparatus 10 are monitor units (30-1 and 30-2). A correction unit (80-1, 80-2) that corrects the output of the circuit and a VOA adjustment unit (90-1, 90-2) that is an optical signal adjustment unit.

  Each polarization signal is polarization-combined after the signal strength is adjusted by the VOA. The monitor unit (30-1, 30-2) monitors the signal strength of each polarization signal, and the monitor value Pm output from the monitor unit (30-1, 30-2) is controlled by the control unit (40-). 1 and 40-2) are supplied to the correction units (80-1 and 80-2), and are corrected to accurate correction values according to the sensitivity characteristics of the monitor units (30-1 and 30-2). The monitor value as the current can be converted into a digital signal by the A / D converter and can be represented as digital data. The digital data is used to perform appropriate digital processing in the correction unit.

  The correction value output from the correction unit (80-1, 80-2) is supplied to the VOA adjustment unit (90-1, 90-2) and compared with a desired value determined in advance or provided from another device The adjustment value corresponding to the difference is output to the VOA (20-1, 20-2). The VOA (20-1, 20-2) outputs an optical signal of the signal intensity adjusted using this adjustment value. In addition, the control method of VOA (20-1, 20-2) can use the same control method by X polarization and Y polarization. Moreover, adjustment of VOA (20-1, 20-2) can be performed also with any signal of a digital signal and an analog signal.

<First Embodiment of the Present Invention>
FIG. 5 is a diagram showing a configuration example of the optical signal control device according to the first embodiment of the present invention. Although the case of X polarization is described in FIG. 5, in the first embodiment, the same control as that of X polarization is performed also in the case of Y polarization. Further, as each signal, either a digital signal or an analog signal can be used.

  In FIG. 5, when the wavelength of the optical signal is λ, and the temperature of the device at that time is T, the monitor value Pm output from the monitor unit has the wavelength λ and the device temperature T as shown in the following equation (1). It can be expressed as a variable function.

  Each individual of the device is denoted by k, and the sensitivity S in the case of polarization information P (X polarization or Y polarization), wavelength λ, and device temperature T is the wavelength λ and It can be expressed as a function with the device temperature T as a variable. The individual k, the polarization information P (X polarization or Y polarization), and the wavelength λ are known, and the device temperature T can be easily obtained by appropriately measuring. The sensitivity S in the case of X polarization can be expressed as the following equation (3).

  Here, it can be considered that the monitor value Pm outputted from the monitor unit is obtained by multiplying the optical signal power from the variable optical attenuator (VOA) by the sensitivity characteristic of the monitor unit. Therefore, the optical signal power from the variable optical attenuator (VOA), that is, the optical signal power before multiplication can be obtained by dividing the monitor value by the sensitivity of the monitor unit at that wavelength and temperature. The correction circuit 103 calculates the optical signal power before multiplication as a correction value by dividing the monitor value Pm output from the monitor unit by the sensitivity S as shown in the equation (4).

  VOA adjustment unit 90-1 calculates VOA adjustment value by dividing desired value [W] by correction value [W] when the value of output power from VOA is desired value [W]. . By supplying the VOA adjustment value to the control input of the VOA, the output of the VOA can be controlled to be equal to a desired value. This VOA adjustment value can be generated in accordance with the input signal format of the control input of the VOA.

  In the above description, the monitor value which is the output of the monitor unit is considered to be the light signal power from the VOA multiplied by the sensitivity characteristic of the monitor unit, but is not limited to the multiplication of the sensitivity characteristic. Corrections can be made to account for other effects. When other influences are taken into consideration, the correction value may be obtained by performing an operation opposite to the method of the influences.

  Next, a method of determining the sensitivity S in the case of the device individual k, X polarization, wavelength λ, and device temperature T will be described. The sensitivity S can be obtained by the reference sensitivity calculation unit 101 and the interpolation / extrapolation unit 102 in the correction unit 80-1 of FIG. The reference sensitivity calculation unit 101 includes a reference temperature selection unit, a constant acquisition unit, a sensitivity calculation unit, and a memory table A.

  The reference temperature is a temperature referred to determine the sensitivity characteristic to the temperature T, and is mainly selected between -5 ° C and + 85 ° C, preferably about 3 to 5 points, and each reference temperature The sensitivity characteristic of the light receiving sensitivity is measured in advance. Since the amount of data stored in the table A fluctuates according to the number of reference temperatures, the number more than the above-described number can be selected as long as the memory table can be saved.

The reference sensitivity calculated in the reference sensitivity calculation unit 101 indicates the light receiving sensitivity at a predetermined wavelength of the sensitivity characteristic at the selected reference temperature, and the sensitivity at a predetermined temperature and wavelength is estimated using this reference sensitivity. In the present embodiment, the sensitivity characteristic to the wavelength is approximated by a quadratic curve, and this quadratic curve is expressed by a quadratic function with the wavelength λ as a variable using the constants a, b and c. The constants a, b and c are determined in advance for each individual, each polarization, and each reference temperature, and are stored in the memory table A for each reference temperature. FIG. 5 exemplifies the case where the constants a, b and c of the quadratic curve with respect to _five reference temperatures T _{1 to} T ₅ are recorded.

The operation of the correction unit 80-1 will be described with reference to the flowchart of FIG. First, in step S1-1, the reference temperature selection unit selects two reference temperatures T _n and T _{n + 1} closest to the current apparatus temperature T. For example, if T ₂ <T <T ₃ , T ₂ and T ₃ are selected, if T <T ₁ , T ₁ and T ₂ are selected, and if T ₅ <T, then T ₄ and T ₅ Is elected.

Next, in step S1-2, the constant acquiring unit respectively stores the constants a, b, and c of the quadratic functions of the reference temperatures T _n and T _{n + 1 in} the individual k and the polarization P (X or Y) respectively. It is obtained from table A. In this case, the constant set at T _n and T _{n + 1} in the case of X polarization is expressed as the following equations (5) and (6).

In step S1-3, the sensitivity characteristic to the wavelength at the two reference temperatures T _n and T _{n + 1} is represented by the reference sensitivity calculation unit using the constant sets a, b and c. The following curve is used for approximation, and reference sensitivities S _kp (T _n , λ) and S _kp (T _{n + 1} , λ) at wavelength λ are calculated from the quadratic curve. This situation is shown in the left view of FIG. In this case, the reference sensitivities at T _n and T _{n + 1} in the case of X polarization are expressed as the following equations (7) and (8).

In step S1-4, the interpolation / extrapolation unit linearly approximates the sensitivity S _kp (T, λ) at the device temperature T from the two reference sensitivities at T _n and T _{n + 1} obtained by the reference sensitivity calculation unit. Ask by. This situation is shown in the right view of FIG. The calculation formula in the case of X polarization is expressed as the following formula (9). For example, in the case of T ₂ <T <T ₃ , the sensitivity S at the device temperature T and the wavelength λ is obtained by interpolation in the case of T <T _{1 and in} the case of T ₅ <T by the extrapolation.

In step S1-5, a correction value is calculated by dividing the monitor value by the sensitivity S _kp (T, λ) calculated in step S1-4. Further, the VOA adjustment value is calculated from this correction value so that the output of the VOA becomes a desired value. Although the X polarization has been described above, the same applies to the Y polarization.

The method of approximating the sensitivity characteristic of the individual k according to the first embodiment of the present invention will be described with reference to FIG. In the left view of FIG. 8, for example, in the reference temperature T _1, to approximate the sensitivity characteristics using the measured values obtained by measuring the sensitivity in three wavelengths lambda. When the sensitivity characteristic is approximated by a quadratic curve by a quadratic function as in the following equation (10), the constants a, b and c in the quadratic function can be easily obtained from the three measured values.

Further, as shown on the right side of FIG. 8, when obtaining from measured values of sensitivity to four or more wavelengths λ, the constants a, b, c of the quadratic function can be obtained by the least square method or the like. The table of FIG. 8 shows the constants a, b and c of the quadratic function at the reference temperatures T _{1 to} T ₅ , and are recorded in the memory table A for each individual k and polarization.

  As described above, in the first embodiment of the present invention, the sensitivity characteristic of the monitor unit is approximated by a quadratic curve with respect to the wavelength, and the light reception of the monitor unit at the device temperature is linearly approximated by predetermined reference temperatures. The sensitivity is calculated. The light receiving sensitivity can be determined from only three constants in the quadratic curve that approximates the sensitivity characteristic to the wavelength at the reference temperature, so the measurement time and data amount of the previously measured data, and the amount of recording in the memory accordingly Can be significantly reduced.

  In the conventional method, the light receiving sensitivity is measured in advance at fine intervals at wavelengths of 1527 nm to 1567 nm and temperatures of -5 ° C. to 85 ° C. in each polarization for each individual monitor unit, and the results are recorded in a memory table Was. For example, in the above wavelength and temperature, when 41 wavelength measurement points and 81 temperature measurement points, it is necessary to acquire 2 × 41 × 81 pieces of data for each individual. A memory area is required to record data.

  On the other hand, in the present embodiment, 2 × 5 × 5 pieces of data are measured in advance when, for example, there are 5 wavelength measurement points and 5 temperature measurement points in each polarization for each individual. In this case, in the memory table, for each polarization and each reference temperature, three constants for determining a quadratic curve representing the sensitivity characteristic with respect to wavelength, ie, 2 × 5 × 3 data are recorded. As long as it is sufficient, the amount of data to be measured in advance, the measurement time, and the amount of recording in the memory associated therewith can be significantly reduced as compared with the prior art. Furthermore, the number of measurement points can be three each for wavelength and temperature, and in this case, the measurement time and memory amount can be further reduced. Since the amount of measurement in advance and the amount of recording on the memory table in the present embodiment are much smaller than those in the prior art, the apparatus can be significantly miniaturized accordingly. Further, in the present embodiment, the dispersion of the branching ratio from the variable optical attenuator to the monitor unit is also included in the sensitivity characteristic and measured, and therefore can be compensated together.

Second Embodiment of the Present Invention
FIG. 9 is a diagram showing an example of the configuration of an optical signal control apparatus according to a second embodiment of the present invention. The configuration and operation of the correction circuit and the VOA adjustment unit in FIG. 9 are the same as in FIG. 5 of the first embodiment. In the second embodiment, the method of calculating the reference sensitivity in the reference sensitivity calculation unit 201 and the recorded content of the memory table B are different from those in the first embodiment. In the second embodiment, as in the first embodiment, in each of X polarization and Y polarization, the output of the variable optical attenuator (VOA) is a desired signal independent of wavelength, temperature and individual While adjusting to the intensity, it further reduces the difference in signal intensity between the X polarization and the Y polarization.

The operation of the correction unit 80-1 will be described with reference to the flowchart of FIG. In step S2-1, the reference temperature selection unit selects two reference temperatures T _n and T _{n + 1} closest to the device temperature T desired to be estimated, using the same method as that of the first embodiment.

In step S 2-2, the constant acquiring unit respectively sets the constants a, b, and c of the quadratic curves of the reference temperatures T _n and T _{n + 1 in} the individual k and the polarization P (X or Y) from the memory table B. get. In this case, the constant set at T _n and T _{n + 1} is expressed as the following equations (11) and (12). P represents either X polarization or Y polarization.

Here, the constant sets a, b and c of the quadratic curve at the reference temperatures T _n and T _{n + 1} can be obtained by the same method as the method described in FIG. 8 of the first embodiment.

In the second embodiment, further, the constant sets α _1k , β _1k and γ _{1k of} the adjustment quadratic curve are also acquired. This constant set reduces the deviation between the sensitivity characteristic of X polarization and the sensitivity characteristic of Y polarization, and adjusts the quadratic function for adjusting the sensitivity characteristic of X polarization to the sensitivity characteristic of Y polarization. It is a constant to find out.

A method of determining the constant set of the adjustment quadratic curve will be described with reference to FIG. Referring temperature T _n is selected, the formula (13), as in (14), the sensitivity characteristic of the X polarized wave of the reference temperature T _n, which is approximated by a quadratic curve, Y polarized wave of the reference temperature T _n The sensitivity characteristics of are determined.

Here, as shown in equation (15), the sensitivity characteristic of the reference temperature T _n of X polarized waves, in order to approach the sensitivity characteristic of the reference temperature T _n of the Y polarized wave, the reference temperature T _n of X polarized wave The sensitivity characteristic is multiplied by the adjustment quadratic curve (α _1k λ ² + β _1k λ + γ _1k ).

The constant sets α _1k , β _1k and γ _1k of the adjustment quadratic curve can be determined, for example, by the method shown in FIG. In the example of FIG. 12, M is the difference between X polarization and Y polarization of 10 log (monitor value / sensitivity actual measurement value), Y polarization sensitivity and X polarization at wavelength λ1 to wavelength λ3 and temperature T1 to temperature T3. Measure the sensitivity, M (wavelength λ1, temperature T1), M (wavelength λ1, temperature T2), M (wavelength λ1, temperature T3) ... M (wavelength λ3, temperature T1), M (wavelength λ3, temperature T2) , M (wavelength λ 3, temperature T 3) are determined, and the constant of the quadratic function is determined so that the sum of the maximum value and the minimum value of these approximates to zero.

  As a method of zero approximation, an existing method such as GRG nonlinear (nonlinear least squares method) can be used. GRG nonlinearity can be implemented by the MS Excel solver function or the like. Thereby, the constant of the adjusting quadratic curve is obtained for each individual k, and the obtained constant of the quadratic curve is recorded in advance in the memory table B. The constant of the adjustment quadratic curve can be set commonly to the temperature, but may be set for each temperature.

In step S2-3, for each polarization, the sensitivity characteristics for wavelengths at two reference temperatures T _n and T _{n + 1} are approximated using a quadratic curve, and further adjusted to the sensitivity characteristic of X polarization The reference sensitivities S _kp (T _n , λ) and S _kp (T _{n + 1} , λ) at the wavelength λ are calculated by multiplying the quadratic curve. The way of obtaining the reference sensitivity of the X polarization is shown in the left view of FIG. The reference sensitivity of the Y polarization can be calculated as in the case of the Y polarization of the first embodiment.

  In the above description, the sensitivity characteristic of X polarization is multiplied by the quadratic function representing the quadratic curve for adjustment, but the quadratic function representing the quadratic curve for adjustment is the sensitivity characteristic of Y polarization. It is also possible to ride.

In step S2-4, the sensitivity S _kp (T, λ) at the device temperature T is determined by linear approximation from the reference sensitivities of the two reference temperatures obtained by the reference sensitivity calculating unit by the interpolation / extrapolation unit. This situation is shown in the right-hand drawing of FIG. This is similar to the first embodiment.

In step S2-5, as in the first embodiment, a correction value is calculated by dividing the monitor value by the sensitivity S _kp (T, λ) calculated in step S2-4, and further, this correction value is calculated. The VOA adjustment value is calculated such that the output of the VOA becomes a desired value.

  In the second embodiment, compared to the first embodiment, it is possible to further reduce the difference in the intensity of the optical signal between the X polarization and the Y polarization. This makes it possible to reduce noise other than the desired main signal even in the case of polarization combining. In the second embodiment, it is necessary to make a prior measurement to obtain the constant of the adjustment quadratic curve, but since only three constants of the adjustment quadratic curve are added for each individual monitor unit. The amount of processing and data involved with this does not increase significantly as compared with the first embodiment. Further, also in the present embodiment, it is possible to compensate for the dispersion of the branching ratio from the variable optical attenuator to the monitor unit.

Third Embodiment of the Present Invention
FIG. 13 is a view showing an example of the configuration of an optical signal control apparatus according to a third embodiment of the present invention. The configurations and operations of the correction circuit 303 and the VOA adjustment unit 90-1 in FIG. 13 are the same as those of FIG. 5 of the first embodiment and FIG. 9 of the second embodiment. The calculation method of the reference sensitivity in the reference sensitivity calculation unit 301 and the recorded contents of the memory table C are different from those in the first and second embodiments.

  In the third embodiment, the sensitivity characteristic of an arbitrary individual is determined from the sensitivity characteristic of a representative individual, and the difference in signal strength between X polarization and Y polarization is further reduced. A representative individual refers to an individual having a reference sensitivity characteristic. The representative individual can be selected from a plurality of existing individuals, and can also be a fictitious individual having a reference sensitivity characteristic.

The operation of the correction unit 80-1 will be described with reference to the flowchart of FIG. In step S3-1, the reference temperature selection unit selects two reference temperatures T _n and T _{n + 1} closest to the device temperature T to be estimated. The method of selection is the same as in the first and second embodiments.

In step S3-2, the constant / coefficient acquisition unit calculates the representative individual r and the reference temperatures T _n and T _{n + 1} of the polarization P (X or Y) as shown in the following equations (16) to (21). Of the constant curves a, b, c and the coefficient B for the individual k, that is, the adjustment coefficient G and the constant set of adjustment quadratic curves for reducing the difference between X polarization and Y polarization, α, β, γ is acquired from the memory table C. P represents either X polarization or Y polarization.

FIG. 16 is a diagram for explaining the operation using the adjustment coefficient according to the third embodiment of the present invention. The left figure in FIG. 16 shows the approximated sensitivity characteristic (two-dot chain line) of the reference temperature T _n of a representative individual in X polarization, and the true sensitivity characteristic of the reference temperature T _n of an actual individual in X polarization (solid line) , And the approximated sensitivity characteristics (dashed-dotted line) of the reference temperature T _n of the actual individual in X polarization. Here, the approximated sensitivity characteristic of the reference temperature of the actual individual can be obtained by multiplying the sensitivity characteristic of the reference temperature T _n of the representative individual by the adjustment coefficient G _kx (T _n ).

Like the X-polarization, right view of FIG. 16 is approximated sensitivity characteristic (two-dot chain line) of the reference temperature T _n of representative individuals in Y polarization side, see the actual temperature of the individuals in the Y polarization T _n Of the actual individual's reference temperature T _n in Y polarization (dashed line). Similar to the X polarization, the approximated sensitivity characteristic of the reference temperature of the actual individual can be obtained by multiplying the sensitivity characteristic of the reference temperature T _n of the representative individual by the adjustment coefficient G _ky (T _n ).

In addition, as shown in the central view of FIG. 16, the sensitivity characteristic of X polarization is obtained by multiplying the sensitivity characteristic approximated by the reference temperature T _n of the actual individual of X polarization by the adjustment quadratic curve. The sensitivity characteristic of the reference temperature T _n of the actual individual of polarization can be approximated.

In step S3-3, as shown in the equations (22) to (25), in each polarization, the wavelength λ is obtained from the quadratic curve at the two reference temperatures of the representative individual and the coefficient B at the two reference temperatures. The reference sensitivities S _kp (T _n , λ) and S _kp (T _{n + 1} , λ) in are calculated, and further, the adjustment coefficient G of one side of the XY polarization is multiplied by the adjustment quadratic curve. This situation is shown in the left view of FIG. Here, an example in which the adjustment coefficient G of X polarization is multiplied by the adjustment quadratic curve may be described, but the adjustment quadratic curve may be multiplied by the sensitivity characteristic of Y polarization.

In step S3-4, the sensitivity S _kp (T, λ) at the device temperature T is determined by linear approximation from the reference sensitivities at the two reference temperatures obtained by the reference sensitivity calculating unit by the interpolation / extrapolation unit. This situation is shown in the right view of FIG. This is similar to the first and second embodiments.

In step S3-5, as in the first and second embodiments, the correction value is calculated by dividing the monitor value by the sensitivity S _kp (T _n , λ) calculated in step S3-4, and further calculated. From this correction value, the VOA adjustment value is calculated such that the output of the VOA becomes a desired value.

  In the present embodiment, as in the second embodiment, it is possible to reduce the difference in the intensity of the optical signal between the X polarization and the Y polarization. This can reduce noise other than the desired main signal in the case of polarization combining. Thus, the intensity of the optical signal of each polarization can be easily adjusted on the transmission side, and efficient restoration processing can be performed on the reception side. In addition, in a plurality of Mach-Zehnder modulators, it is possible to easily perform an operation or control to strengthen a signal having a desired frequency or weaken a signal of an unnecessary frequency by combining phases by adding phase differences to outputs. Is possible.

  FIG. 17 is a diagram for describing a method of approximating sensitivity characteristics of a representative individual according to the third embodiment of the present invention. The sensitivity characteristic of a representative individual is approximated by a quadratic curve by a quadratic function as in the first and second embodiments. Similar to the first and second embodiments, the constants a, b and c of the quadratic function can be easily obtained using the equation of the quadratic function and the least squares method.

The table shown in FIG. 17 shows constants a, b and c with respect to reference temperatures T _{1 to} T ₅ of X polarization and Y polarization of a representative individual, and are recorded in the memory table C. In addition, since the sensitivity characteristic of the representative individual indicates the sensitivity of the reference to the sensitivity characteristic of the actual individual, it is not necessary to necessarily obtain it by actual measurement, and if the sensitivity characteristic of the actual individual is indicated by the adjustment coefficient G The standard sensitivity characteristic of can also be used as a representative individual's sensitivity characteristic.

FIG. 18 is a view for explaining a method of obtaining a coefficient according to the third embodiment of the present invention. The adjustment coefficients G _kx and G _ky can be obtained by the least squares method or the like. Specifically, in the case of X polarization, the adjustment coefficient G _kx is calculated such that the value of Expression (26) is minimized. The adjustment factor G _{ky of} Y polarization can be calculated in the same manner. The table in FIG. 18 shows the adjustment coefficients G _kx and G _ky for the reference temperatures T _{1 to} T ₅ of the X polarization and the Y polarization for every arbitrary individual k, and these are for every arbitrary individual k It is recorded in the memory table C.

Further, the constants of the adjustment quadratic curve: α _2k , β _2k and γ _2k can be determined by the same method as in the second embodiment. In the example of FIG. 18, Y is the polarization sensitivity and X polarization at wavelength λ1 to wavelength λ3 and temperature T1 to temperature T3 as M is the difference between X polarization and Y polarization of 10 log (monitored value / measured sensitivity actual value) Measure the sensitivity, M (wavelength λ1, temperature T1), M (wavelength λ1, temperature T2), M (wavelength λ1, temperature T3) ... M (wavelength λ3, temperature T1), M (wavelength λ3, temperature T2) , M (wavelength λ 3, temperature T 3) are determined, and the constant of the quadratic function is determined so that the sum of the maximum value and the minimum value of these approximates to zero.

  As a method of zero approximation, GRG nonlinear (nonlinear least squares method) or the like can be used. GRG nonlinearity can be implemented by the MS Excel solver function or the like. Thereby, the constant of the adjustment quadratic curve is obtained for each individual k, and the obtained quadratic curve constant is recorded in advance in the memory table B. The constant of the adjustment quadratic curve can be set commonly to the temperature, but may be set for each temperature.

  In the third embodiment, for each polarization of a representative individual, for example, if there are 5 wavelength measurement points and 5 temperature measurement points, 2 × 5 × 5 pre-measurements are carried out. In each polarization of the individual of 2., 2 × 5 × 5 pre-measurements may be performed. In this case, in the memory table, three constants for determining a quadratic curve representing the sensitivity characteristic with respect to wavelength are recorded for each polarization and each reference temperature for each representative individual, that is, 2 × 5 × 3 data It is sufficient to record, for each individual, three constants of each polarization, an adjustment factor for each reference temperature, that is, 2 × 5 × 1, and an adjustment quadratic curve for each individual.

  While each of the first and second embodiments needs to record three constants of the quadratic curve at each polarization and each temperature for each individual, in the third embodiment, a representative individual is required. It is only necessary to record the three constants of the quadratic curve at each polarization and each temperature, and to record only the adjustment factor for each reference temperature for each actual individual. Also with regard to the adjusting quadratic curve, only three constants of the adjusting quadratic curve are added for each individual monitor unit. As described above, in the third embodiment, the amount of data to be measured in advance, the measurement time, and the amount of recording in the memory associated therewith are significantly reduced more than in the first and second embodiments. The size of the device can be reduced. Also in the present embodiment, it is possible to compensate for the dispersion of the branching ratio from the variable optical attenuator to the monitor unit.

  The present invention can be used as an optical signal control device for controlling the intensity of an optical signal to be transmitted and received in coherent optical communication.

  DESCRIPTION OF SYMBOLS 1 ... optical transmitter, 2 ... optical receiver, 3 ... optical fiber, 4 ... transmission signal processing part, 5 ... reception signal processing part, 6-1, 6-2 ... modulation part, 7-1, 7-2 ... Demodulation unit, 10: optical signal control device, 20-1 to 20-4, variable optical signal adjustment unit (VOA), 30-1 to 30-4, monitor unit, 40-1 to 40-4, control unit, 50 ... polarization synthesis, 60 ... polarization separation, 70-1, 70-2 ... tunable laser diode (TLD), 80-1, 80-2 ... correction unit, 90-1, 90-2 ... VOA adjustment unit, 101, 201, 301 ... reference sensitivity calculation unit, 102, 202, 302 ... interpolation / exterior unit, 103, 203, 303 ... correction circuit.

Claims (8)

A variable light signal adjustment unit,
A monitor unit that monitors the optical signal intensity of the optical signal output from the variable optical signal adjustment unit;
A correction unit that corrects the light signal intensity of the light signal monitored by the monitor unit;
And an optical signal adjustment unit that calculates an adjustment value of the variable light signal adjustment unit,
The correction unit is
It is closest to the temperature of the monitor using the sensitivity characteristic for the wavelength of the light sensitivity of the monitor for each of a plurality of reference temperatures approximated using the measured value of the light sensitivity of the monitor at a predetermined wavelength and temperature. A reference sensitivity calculation unit that calculates reference light reception sensitivity of the monitor unit at the wavelength of the optical signal in the sensitivity characteristics of two reference temperatures;
And an interpolation / extrapolation unit that calculates the light reception sensitivity at the temperature of the light signal and the temperature of the monitor unit by interpolation or extrapolation using the reference light reception sensitivity.
The correction value for correcting the light signal intensity monitored by the monitor unit is output to the light signal adjustment unit using the light reception sensitivity at the temperature of the monitor unit and the wavelength of the light signal.
The optical signal adjustment unit
An optical signal control apparatus configured to calculate an adjustment value of the variable light signal adjustment unit using the correction value and a predetermined desired value, and to output the calculated adjustment value to the variable light signal adjustment unit. The reference sensitivity calculation unit
The sensitivity characteristic for the wavelength of the light receiving sensitivity of the monitor unit is approximated by a quadratic curve, and the reference light receiving sensitivity at the at least two reference temperatures is calculated using a quadratic function representing the quadratic curve,
The interpolation / extrapolation unit is
The light according to claim 1, wherein the light reception sensitivity at the wavelength of the light signal and the temperature of the monitor unit is calculated by linear approximation using reference light reception sensitivities at the at least two reference temperatures. Signal controller. The quadratic curve is expressed using a constant of a quadratic function determined using the light receiving sensitivity of the monitor unit measured in advance, and the reference sensitivity calculating unit is configured to calculate the quadratic curve at at least three reference temperatures. The light signal controller according to claim 2, wherein a constant of a function is stored. The reference sensitivity calculation unit
For each of the X polarization signal and the Y polarization signal of the optical signal, the sensitivity characteristic of the light reception sensitivity of the monitor unit to the wavelength is approximated by a quadratic curve,
Between the sensitivity characteristic of the X polarization signal and the sensitivity characteristic of the Y polarization signal, a quadratic function representing a quadratic curve approximating the sensitivity characteristic of one of the X polarization signal and the Y polarization signal The optical signal control device according to claim 2 or 3, wherein the optical signal control device is multiplied by a quadratic function representing a quadratic curve for adjustment to reduce the deviation of. The reference sensitivity calculation unit
The sensitivity characteristic of the light reception sensitivity of a predetermined representative monitor unit to the wavelength is approximated by a first quadratic curve, and the sensitivity characteristic of the light reception sensitivity of the monitor unit to the wavelength is multiplied by the adjustment coefficient to the first quadratic curve. Calculating the reference light receiving sensitivities at the at least two reference temperatures by using a quadratic function that approximates the second quadratic curve represented by the equation and represents the second quadratic curve. The optical signal control apparatus as described in 1). The first quadratic curve is expressed using a constant of a quadratic function determined using the light receiving sensitivity of the monitor unit measured in advance, and the reference sensitivity calculating unit is configured to determine the at least three reference temperatures. The light signal controller according to claim 5, wherein a constant of a quadratic function is stored. The reference sensitivity calculation unit is configured to multiply the first quadratic curve by the adjustment coefficient with respect to the sensitivity characteristic of the light reception sensitivity of the monitor unit with respect to the wavelength of each of the X polarization signal and the Y polarization signal of the optical signal. And the sensitivity characteristic of the X polarization signal and the sensitivity of the Y polarization signal to the adjustment coefficient of either the X polarization signal or the Y polarization signal. The light signal control device according to claim 5 or 6, wherein the light signal control device is multiplied by a quadratic function that represents a quadratic curve for adjustment to reduce the deviation between the characteristics. A variable light signal adjustment unit; a monitor unit that monitors the light signal intensity of the light signal output from the variable light signal adjustment unit; a correction unit that corrects the light signal intensity of the light signal monitored by the monitor unit; An optical signal control method in an optical signal control device, comprising: an optical signal adjustment unit that calculates an adjustment value of the variable optical signal adjustment unit,
The monitor unit
Monitoring the optical signal intensity of the optical signal output from the variable optical signal adjustment unit;
The correction unit
With sensitivity to the wavelength of the light-receiving sensitivity of the monitor unit of the plurality of reference each temperature approximated using measured values of the light-receiving sensitivity of the monitor, the two closest reference temperature to the temperature of the monitor Calculating the reference light reception sensitivity of the monitor unit at the wavelength of the light signal in the sensitivity characteristic ;
Calculating the light reception sensitivity at the wavelength of the light signal and the temperature of the monitor unit by interpolation or extrapolation using the reference light reception sensitivity;
Outputting to the light signal adjustment unit a correction value for correcting the light signal intensity monitored by the monitor unit using the wavelength of the light signal and the light reception sensitivity at the temperature of the monitor unit;
The optical signal adjustment unit
Calculating an adjustment value of the variable light signal adjustment unit using the correction value and a predetermined desired value;
Outputting the adjustment value of the variable light signal adjustment unit to the variable light signal adjustment unit.