JP6502663B2 - Optical communication device - Google Patents

Description

  The present invention relates to an optical communication apparatus, and more particularly to an optical communication apparatus suitable for transmitting and receiving multilevel optical information transmitted through an optical fiber.

  With the explosive increase of mobile terminals and the spread of cloud computing etc., rapid increase of traffic continues in the data center in charge of information processing and transmission on the Internet and between the data centers. Most of such ultra-high-speed information transmission is realized by optical fiber transmission, and several kilometers to several tens of kilometers of optical fiber transmission line for connecting the inside and outside of the data center from the distance of several hundreds of meters connecting devices Speeding up of the speed is desired. Although a representative of the current high-capacity transmission standard is 100G Ethernet (IEEE 802.3 100GbE), the next-generation high-capacity optical fiber transmission standard is scheduled to increase to 400G Ethernet on the background of further increase in traffic.

  Since optical communication devices used for such optical fiber transmission need to be placed in large quantities in devices limited in size, power supply, and maximum heat generation, especially miniaturization, cost reduction, and power saving are required. It is done. As a factor of increase of the power consumption of the optical communication device, a heater or a cooler used for temperature stabilization of a light output part that modulates and outputs an optical signal such as a light source or an optical modulator may be mentioned. For this reason, in an optical communication apparatus used for optical fiber transmission, it is general to save temperature by minimizing temperature stabilization or by narrowing the range of temperature stabilization. However, the omission of such temperature stabilization greatly affects the performance of the optical communication device, particularly the light output unit.

A. E-L. A. Mohamed, et al., International Journal of Computer Science and Telecommunications Volume 2, Issue 6, September 2011. X. Song, et al., IEEE 802.3 400 GbE Study Group, Interium Meeting, Jan. 2014. (R. Hirai, H. Toyoda and N. Kikuchi, "Proposal of new 400 GbE signaling formats with 4 λ x 100 G configuration," IEEE 802.3 400 GbE Study Group, Interium Meeting, Jan. 2014. N. Kikuchi and R. Hirai, "Intensity-Modulated / Direct-Detection (IM / DD) Nyquist Pulse-Amplitude Modulation (PAM) Signaling for 100-Gbit / s / λ Optical Short-reach Transmission" in ECOC 2014, paper P .4.12

  For example, in a direct modulation method in which a light source is directly turned on / off, which is a typical configuration of a light output unit, a single light source function for emitting laser light and a single light modulator function for modulating an optical signal at high speed The modulation characteristics of the light output section are susceptible to fluctuations in the external environment, because In general, the light output unit of the direct modulation system has a characteristic that the output light intensity decreases and the modulation band sharply decreases when the operating temperature increases. In addition, when the laser drive current is increased, the output light intensity is increased and the modulation band is improved. When the modulation band changes due to changes in the operating temperature or laser drive current, waveform distortion occurs, closing the eye opening of the output light signal waveform, the reception sensitivity is significantly degraded, and the transmission distance is shortened. Optical fiber transmission becomes impossible.

  For this reason, in the past, development of lasers with minimal temperature dependency has been promoted, but the operating temperature range of the optical communication device is very large, for example, 0 to 85 degrees, and the reduction of the modulation band particularly at high temperatures is still This is a major limitation on the modulation speed and transmission distance of directly modulated lasers. In addition, since the change of the operating temperature largely changes the wavelength of the light source, in wavelength multiplex transmission using light sources of a plurality of wavelengths, the operating temperature range is, for example, +/− 10 degrees, etc. to keep the amount of wavelength change within a certain range. In general, the higher the operating temperature center, the higher the effect of preventing an increase in power consumption, and the problem is that the performance is limited due to the deterioration of the laser characteristics on the high temperature side.

  Also, in an optical communication apparatus using an external modulation method in which the light source and the light modulator are separated in the light output unit, since the light source and the light modulator are separated, temperature dependence such as direct modulation is used. Although the sex is somewhat mitigated, there are still major performance problems. In the external modulation method, low-cost, small-sized light modulators are semiconductor modulators that are highly dependent on temperature and wavelength, such as semiconductor electroabsorption modulators (EA modulators), phase modulators, MZ modulators, and IQ Modulators, polarization multiplexing IQ modulators, polymer modulators, etc. are used. It is known that the light absorption characteristic which is the operation principle of these modulators and the phase modulation characteristic accompanying this change depending on the temperature and the signal wavelength. For example, in a polymer modulator, a polymer used as a modulator material has high temperature dependency. Non Patent Literature 1 reports the modulation characteristics of a polymer modulator, in particular, the temperature characteristics of the polymer modulator shown in FIG. As shown in FIG. 12, the frequency band of the polymer modulator is reduced to 1⁄2 or less by the temperature rise. In addition, since the EA modulator, the phase modulator, and the like perform light modulation using the band structure of the semiconductor and its absorption characteristics, their frequency characteristics have temperature dependency. The inventors examined the modulation characteristics of the EA modulator and confirmed the temperature dependence of the frequency characteristics of the EA modulator. FIG. 13 is a diagram showing frequency characteristics of the EA modulator. As shown in FIG. 13, it can be seen that the modulation band (-3 dB band) of the EA modulator is greatly reduced from approximately 20 GHz to 10 GHz as the temperature rises from 25 degrees to 85 degrees Celsius.

  On the other hand, in optical communication devices used for next-generation optical fiber transmission represented by 400G Ethernet, when the optical modulation speed reaches several tens GBaud, the operating speed of the laser light source or optical modulator approaches the upper limit, and modulation The shortage of the band becomes remarkable, and even under ideal conditions, sufficient eye opening and extinction ratio are not obtained. In such a state, since the operating margin is insufficient, the information transmission becomes difficult if the modulation characteristic is merely changed due to the temperature change of the laser light source or the light modulator, and the slight change of the laser drive current. There is. Therefore, in order to overcome the limitations of the operating speed of the laser light source and the light modulator, application of multi-level modulation is being considered instead of conventional binary modulation. The binary modulation is to make the logic "1" and the logic "0" of the binary information signal to be transmitted correspond to the maximum and minimum of the light intensity, respectively. On the other hand, in one of the multilevel modulation, the multilevel information signal to be transmitted is made to correspond to a multilevel level using an intermediate level between the maximum and the minimum of the light intensity. For example, in Non-Patent Document 2, utilization of 4 to 16 pulse amplitude modulation (PAM) is studied.

  Here, FIG. 14 shows an example of the configuration of a conventional optical communication apparatus using multi-level modulation. The optical communication apparatus 100 shown in FIG. 14 uses an external modulation method, and the multi-level encoding unit 102 converts the digital information signal 101 input as a parallel digital signal into a multi-level signal such as PAM4, PAM8, and duobinary signal. Encode. Then, the analog multilevel signal analog-converted by the DA converter 115 is amplified to an amplitude A by the output stage amplifier unit 103, and then the bias voltage Vb is added by the bias T104, and the modulated signal 111 is added to the optical modulator 105. It is input. On the other hand, the laser drive current 112 is input to the semiconductor laser 106 serving as a light source, and light having an intensity corresponding to the laser drive current 112 is output from the semiconductor laser 106 and input to the light modulator 105. Then, the optical modulator 105 outputs the multilevel modulated light 108 obtained by modulating the laser light input from the semiconductor laser 106 by the modulation signal 111, and outputs the output optical fiber 107.

  The control unit 113 in FIG. 14 sets the setting value A of the amplitude, the bias voltage setting value Vb, and the laser driving current setting value If. For some operation parameters such as the laser drive current set value If and the bias voltage set value Vb, the output light intensity separately output from the optical modulator 105 is detected, and feedback control is performed so that the value becomes constant. In some cases. It is possible to compensate for the deterioration of the transmission performance of the optical signal output from the optical modulator 105 by controlling the analog electrical signal by the bias voltage setting value Vb, the laser driving current setting value If, etc. It was effective in binary modulation.

  However, in multi-level modulation, it is difficult to compensate for the degradation of the transmission performance of the output optical signal by the conventional method. This is because using multi-level modulation signals such as PAM signals, multi-level phase modulation signals, and QAM modulation signals that have high multi-level numbers, the number of eye openings in the output signal waveform is greater than when using conventional binary modulation signals. It is because it reduces sharply to one part. FIG. 15 is a diagram showing an output light waveform and its spectrum by PAM 4 signal modulation at a light modulation rate of 50 GBaud. As shown in FIG. 15, the output light waveform shows four levels of light intensity, and it can be seen that the eye opening is narrower than the binary level. And the spectrum gently spreads to around 50 GHz. For this reason, the eye opening amount and waveform distortion of the output optical signal waveform become extremely sensitive to changes in the modulation characteristics, and even if the modulation band and frequency characteristics of the laser light source or the optical modulator slightly change Will occur.

  Furthermore, the inventors have proposed the use of Nyquist PAM modulation using Nyquist pulses as a method for reducing the required bandwidth and achieving high-speed transmission as compared to the conventional PAM modulation (Non-Patent Document 3 and Non-Patent Document 3) Patent Document 4). In this case, the Nyquist filter for limiting the modulation band is provided between the multilevel encoding unit 102 and the optical modulator 105 shown in FIG. FIG. 16 is a diagram showing an output light waveform by Nyquist PAM modulation and its spectrum at a light modulation rate of 50 GBaud. As shown in FIG. 16, the output light waveform by Nyquist PAM modulation is a waveform with high peak intensity, but its spectrum is a substantially flat rectangle within the required band, and the required bandwidth is relaxed to R / 2 = 25 GHz. Can.

  However, while Nyquist PAM modulation is a very effective technique for reducing the required bandwidth of the light source and the optical modulator, the characteristics of the laser light source and the optical modulator change due to changes in the operating environment and operating conditions of the optical communication device. Have the problem of being susceptible to In Nyquist PAM modulation, as shown in FIG. 16, by keeping the spectrum shape of the output optical signal rectangular, the occurrence of intersymbol interference of the waveform is prevented, and if the spectrum shape is broken, a large degradation of transmission performance occurs. I will.

  As described above, the deterioration of the output light signal due to the characteristic change of the light output part is greatly increased while the modulation speed becomes extremely high due to the increase of the transmission capacity in recent years, and the light modulation is multi-valued. is there.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to correct a digital information signal to be transmitted so as to compensate for deterioration of an output light signal due to a characteristic change of a light output unit in an optical communication device. .

  (1) In order to solve the above problems, an optical communication apparatus according to the present invention comprises: converting means for converting a digital signal used to modulate an optical signal to be output into an analog multilevel signal; A light output unit that outputs the light signal, a characteristic data acquisition unit that acquires characteristic data of the light output unit, and compensation of a change in modulation characteristic of the light output unit according to the acquired characteristic data And a correction unit that corrects the digital signal converted by the conversion unit.

  (2) In the optical communication device according to (1), the characteristic data acquisition unit may acquire an operating temperature of the light output unit as the characteristic data.

  (3) The optical communication device according to (2), further including: a temperature sensor for measuring an operating temperature of the light output unit.

  (4) In the optical communication device according to any one of (1) to (3), the characteristic data acquisition unit may include a drive current value for driving a light source of the optical signal or the light output unit. Alternatively, a bias voltage to be set may be obtained.

  (5) The optical communication device according to any one of (1) to (4), further including: a storage unit that stores correction information for correcting the digital signal according to the characteristic data; The correction unit may acquire correction information corresponding to the acquired characteristic data from the storage unit and superimpose the correction information on the digital signal.

  (6) In the optical communication device according to (5), the storage unit stores the correction information according to the value of the acquired characteristic data, when the correction information is not stored in the storage unit. The image processing apparatus may further include an interpolation unit that interpolates the correction information corresponding to the value of the acquired characteristic data based on the correction information and outputs the interpolation information to the correction unit.

  (7) In the optical communication device according to (5) or (6), the correction information may be a value for flattening the frequency characteristic of the light output unit.

  (8) In the optical communication device according to (7), the correction unit is a digital filter that flattens the frequency characteristic of the light output unit, and the correction information is the frequency characteristic of the light output unit. It may be a set value that determines the transfer characteristic of the digital filter for flattening.

  (9) In the optical communication device according to any one of (5) to (8), the storage unit is configured of a storage medium in which the correction information can be rewritten or the storage unit can be exchanged. , May be.

  (10) The optical communication apparatus according to (9), further including: a signal terminal for writing the correction information in the storage unit, or communication means.

  (11) In the optical communication device according to any one of (1) to (10), a photoelectric conversion unit that converts a received light signal received from the outside into an electric signal, and an error of the converted electric signal And a decoding unit that decodes the equalized electrical signal and outputs it as an information signal.

  According to the present invention, an optical communication apparatus is provided which corrects a digital information signal to be transmitted to compensate for deterioration of an output light signal due to a characteristic change of the light output unit.

It is a figure showing an example of composition of an optical communication device concerning a 1st embodiment. It is a figure which shows the 1st example of the circuit which comprises the correction | amendment part of the optical communication apparatus which concerns on 1st Embodiment. It is a figure which shows the 2nd example of the circuit which comprises the correction | amendment part which concerns on 1st Embodiment. It is a figure which shows an example of the correction information table memorize | stored in the correction information storage part which concerns on 1st Embodiment. It is a figure which shows the frequency characteristic of the optical modulator concerning 1st Embodiment. It is a figure which shows an example of the frequency characteristic of the correction | amendment part which concerns on 1st Embodiment. It is a figure which shows the synthetic | combination frequency characteristic which synthesize | combined the frequency characteristic of a modulator, and the frequency characteristic of a correction | amendment part. It is a figure which shows an example of a structure of the optical communication apparatus which concerns on 2nd Embodiment. It is a figure which shows an example of a structure of the optical communication apparatus which concerns on 3rd Embodiment. It is a figure which shows an example of a structure of the optical communication apparatus which concerns on 4th Embodiment. It is a figure which shows an example of a structure of the optical communication apparatus which concerns on 5th Embodiment. It is a figure which shows the temperature characteristic of a polymer modulator. It is a figure which shows the frequency characteristic of an EA modulator. It is a figure which shows an example of a structure of the optical communication apparatus using the conventional multi-level modulation. It is a figure which shows the output light waveform and its spectrum by PAM4 signal modulation in light modulation speed | rate 50 GBaud. It is a figure which shows the output light waveform by Nyquist PAM modulation in the light modulation speed | rate 50 GBaud, and its spectrum.

First Embodiment
Hereinafter, a first embodiment of the present invention will be described in detail based on the drawings. In the drawings, the same or equivalent elements will be denoted by the same reference symbols, without redundant description.

  FIG. 1 is a diagram showing an example of the configuration of the optical communication apparatus according to the first embodiment. As shown in FIG. 1, the optical communication apparatus 200 according to the first embodiment includes a multi-level encoding unit 202, a correction unit 203, a DA converter 204, an output stage amplification unit 205, a bias T206, a semiconductor laser 208, and an optical modulator. A light output unit 207 including a light source 209, a constant voltage source 210, a constant current source 211, a control unit 212, a correction information storage unit 213, and a temperature sensor 214 are included. The optical communication apparatus 200 according to the first embodiment mainly has a function as an optical transmitter, and shows an example in which an external modulation system including the semiconductor laser 208 and the optical modulator 209 is adopted for the optical output unit 207. .

  In the first embodiment, the digital information signal to be transmitted is corrected so as to compensate for the deterioration of the output light signal due to the change in temperature which is one of the characteristic data that is an index of the characteristic change of the light output unit 207. Here, the degradation of the output optical signal includes distortion of the waveform shape or spectrum of the output optical signal, degradation of the band, and so on. In other words, the modulation characteristic change of the optical output unit that outputs such degraded optical signal It can be said that.

  The digital information signal 250 to be transmitted is a signal used to modulate an optical signal in the light output unit 207. In this embodiment, first, the digital information signal 250 to be transmitted is input as a parallel digital signal to the multi-level encoding unit 202, encoded into a multi-level signal, and input to the correction unit 203 to be corrected. , Converted by the DA converter 204 into an analog multilevel signal. Then, the analog multilevel signal is amplified to a predetermined amplitude by the output stage amplification unit 205, and the bias voltage is added by the bias T 206, and is input to the light output unit 207 as the modulation signal 251.

  The light output unit 207 includes the semiconductor laser 208 and the light modulator 209. The semiconductor laser 208 outputs laser light of an intensity corresponding to the laser drive current 252 to the light modulator 209. Then, the optical modulator 209 outputs an optical signal obtained by modulating the laser light input from the semiconductor laser 208 to an optical intensity according to the modulation signal 251 which is an analog multi-level signal as the output optical signal 257 to the output optical fiber 258 Do. In the first embodiment, an EA modulator is used as the light modulator 209. Since the EA modulator performs light modulation using the band structure of the semiconductor and its absorption characteristics, it has been described above that the frequency characteristics have temperature dependency. As a result, generally, when the operating temperature of the EA modulator rises, the band structure widens and the effect of light modulation is attenuated, so that the modulation efficiency of the modulation signal is reduced, the extinction ratio is degraded, and the optical loss increases and the modulation band decreases. Degradation of the output optical signal 257 occurs. Therefore, in the optical communication device 200 according to the first embodiment, the temperature sensor 214 is disposed in the vicinity of the light output unit 207 (especially, in the vicinity of the light modulator 209) to measure the operating temperature of the light output unit 207. There is. The temperature sensor 214 measures the temperature of the light output unit 207, and the measured temperature information is input to the control unit 212 as a temperature sensor signal 253.

  The control unit 212 sets the setting value A of the output amplitude of the analog multilevel signal by the output stage amplification unit 205 and the bias voltage setting value Vb for causing the constant voltage source 210 to output the bias voltage supplied to the light output unit 207. A laser current setting value If for causing the constant current source 211 to output a drive current for driving the laser 208 is set. These values are operating parameters for controlling the operating point of each component, and generally, values corresponding to the characteristics are determined based on the pre-measurement results of the output stage amplification unit 205, the optical modulator 209, and the semiconductor laser 208. It is stored and set when the optical communication device 200 is started up. Furthermore, for some operation parameters such as the bias voltage setting value Vb and the laser current setting value If, the output light intensity separately output from the light output unit 207 is detected, and feedback control is performed so that the value becomes constant. There is also a case to do. Thus, the bias voltage setting value Vb, the laser current setting value If, etc. are set according to the characteristics of the light modulator 209 and the semiconductor laser 208, and these values also become the characteristic data of the light output unit 207. obtain.

  In addition, the control unit 212 includes a characteristic data acquisition unit that acquires characteristic data of the light output unit 207, and digital information to compensate for the deterioration of the output optical signal 257 according to the value of the characteristic data acquired by the characteristic data acquisition unit. Correction information for correcting the signal 250 is output from the correction information storage unit 213 to the correction unit 203. In the present embodiment, the control unit 212 acquires the temperature sensor signal 253 output from the temperature sensor 214, and selects a correction information selection signal for selecting correction information based on the temperature information indicated by the acquired temperature sensor signal 253. 255 is output to the correction information storage unit 213. Here, the correction information selection signal 255 may be the temperature information indicated by the temperature sensor signal 253 as it is, or the temperature information converted into the address number of the correction information table stored in the correction information storage unit 213 or the like. It may be Then, the correction information corresponding to the correction information selection signal 255 is read out from the correction information table stored in the correction information storage unit 213 and is output to the correction unit 203 as a correction information setting signal 256. Note that the control unit 212 may be provided with communication means for communicating with an external information processing apparatus, and operation parameters and characteristic data may be acquired via the external communication signal 254.

  The correction unit 203 corrects the digital information signal by superimposing the correction information set by the correction information setting signal 256 on the digital information signal 250. The correction unit 203 may be a digital filter circuit whose output characteristics of the correction unit 203 are variable, and an example of two digital filter circuits will be shown below, but other digital filter circuits may be used.

  FIG. 2 is a diagram illustrating a first example of a circuit that configures the correction unit 203 of the optical communication device according to the first embodiment. As shown in FIG. 2, the correction circuit 300 is configured using a real tap FIR (finite impulse response) filter. The FIR filter is a digital filter used as a frequency characteristic equalizer in digital signal processing and digital communication, and is configured by arranging a delay circuit 301, a plurality of real tap multipliers 302, and an adder 303 in a ladder form. The correction circuit 300 illustrated in FIG. 2 is an 11-tap FIR filter using 11 real tap multipliers 302, and the transfer characteristic of the correction circuit 300 is determined by the setting value set in the real tap multiplier 302. In the present embodiment, the correction circuit 300 rewrites the 11 real values set in each real number tap multiplier 302 by the correction information setting signal 256 indicating the correction information input from the correction information storage unit 213, thereby achieving multiple corrections. The digital information signal 250 input from the value encoding unit 202 can be arbitrarily corrected. Thus, the correction circuit 300 can correct the digital information signal 250 to compensate for the deterioration of the output light signal 257. Here, increasing the number of real tap multipliers 302 improves the compensation accuracy, while the power consumption of the correction circuit 300 increases, so it is ideal to use several tens of real tap multipliers 302. .

  Next, FIG. 3 is a diagram illustrating a second example of a circuit that configures the correction unit 203 according to the first embodiment. As shown in FIG. 3, the correction circuit 310 is a frequency domain equalizer configured using FFT and inverse FFT. The frequency domain equalizer is also a digital filter used in digital signal processing and digital communication, and is configured by arranging 64 complex tap multipliers 312 between the FFT circuit 311 of period 64 and the inverse FFT circuit 313. By setting the value of each tap of these 64 complex tap multipliers 312, the output characteristic of the correction unit 203 is directly changed to obtain a free output characteristic.

  FIG. 4 is a view showing an example of the correction information table stored in the correction information storage unit 213 according to the first embodiment. The correction information table illustrated in FIG. 4 corresponds to the optical communication apparatus 200 shown in FIG. 1 and the configuration of the correction circuit 300 shown in FIG. That is, in the correction information table, values to be set in the respective real number tap multipliers 302 of the correction circuit 300, which are correction information for compensating for deterioration of the output light signal 257, are stored. In the correction information table illustrated in FIG. 4, the operating temperature T of the light output unit 207 as the characteristic data is set in the first column, and the operating temperature T is set in units of 1 ° C. Eleven tap weights W1 to W11 are set in the second and subsequent columns, and tap weight values W1 to W11 to be set to the taps of the eleven real tap multipliers 302 of the correction circuit 300 are stored. According to such a correction information table, correction information (tap weight) necessary for the correction by the correction unit 203 is read according to the operating temperature of the light output unit 207. Here, if the interval of the operating temperatures T in the correction information table is too wide, the quantization error of the correction information setting signal 256 becomes large, so the resolution of the temperature sensor 214 in FIG. Even if it occurs, it is necessary to suppress it to such an extent that the transmission performance is not affected.

  Here, the tap weight stored in the correction information table is a deterioration of the output light signal 257 according to the operating temperature T of the light output unit 207, that is, of the light output unit 207 (in the present embodiment, the light modulator 209). It is a value determined to compensate for the modulation characteristic change. The specific tap weight setting method will be described below. Here, as one of the modulation characteristics of the light output unit 207, the frequency characteristic of the light modulator 209 will be described as an example.

  FIG. 5 is a diagram showing the frequency characteristic of the light modulator 209 according to the first embodiment. FIG. 5 is a diagram showing the frequency characteristics of the optical modulator 209 according to the operating temperature of the optical modulator 209, and as the operating temperature of the optical modulator 209 changes to 0 ° C., 25 ° C., 50 ° C., the frequency The characteristics change, and the modulation band decreases (for example, the 3 dB light modulation band is about 21 GHz at 0 ° C. but decreases to 19 GHz at 25 ° C., and to 15 GHz at 50 ° C.). In addition, there is a possibility that the wavelength of the laser light input from the semiconductor laser 208 may change significantly due to the rise of the operating temperature of the light modulator 209, and in the case of an external modulator with large wavelength dependency like an EA modulator. The change of the wavelength of the input laser light may cause a large change in the frequency characteristic. Therefore, it is necessary to provide the correction unit 203 with a frequency characteristic that compensates for such a change in the frequency characteristic of the optical modulator 209.

  FIG. 6 is a diagram showing an example of the frequency characteristic of the correction unit 203 according to the first embodiment. FIG. 6 shows the frequency characteristics of the correction unit 203 according to the operating temperature of the light modulator 209, and the tap weight of the corresponding operating temperature of the correction information table shown in FIG. The frequency characteristic of the correction unit 203 is obtained. Here, it is ideal that the frequency characteristic of the correction unit 203 is a characteristic that cancels out the change of the frequency characteristic of the light modulator 209. Specifically, the frequency characteristics in the band of 0 to 20 GHz at three points of the operating temperatures of 0 ° C., 25 ° C., and 50 ° C. shown in FIG. 6 are the inverse of the frequency characteristics of the optical modulator 209 at each temperature shown in FIG. It is a characteristic.

  FIG. 7 is a diagram showing a combined frequency characteristic obtained by combining the frequency characteristic of the light modulator 209 shown in FIG. 5 and the frequency characteristic of the correction unit 203 shown in FIG. As shown in FIG. 7, the combined frequency characteristic is constant regardless of the operating temperature within the band of 0 to 20 GHz, and the modulation band does not decrease. As described above, by causing the frequency characteristic of the correction unit 203 to be inverse to the frequency characteristic of the light modulator 209 shown in FIG. It is possible to cancel out.

  Therefore, the tap weight values included in the correction information table are set so that the frequency characteristics of the correction unit 203 have such characteristics as to cancel changes in the frequency characteristics of the optical modulator 209 at each operating temperature. Here, in particular, when Nyquist PAM modulation is used, it is effective to set the tap weights such that the frequency characteristic of the correction unit 203 is inverse to the frequency characteristic of the optical modulator 209. As described above, in the Nyquist PAM modulation including the Nyquist filter for limiting the modulation band between the multilevel encoding unit 202 and the light output unit 207, the light modulator 209 outputs regardless of the temperature change of the light modulator 209. Since it is necessary to maintain the spectrum of the output optical signal 257, that is, the state in which the frequency characteristic of the optical modulator 209 is almost completely flat in the band, the target shape of the frequency characteristic of the optical modulator 209 is shown in FIG. It is sufficient to have a flat frequency characteristic shape as shown.

  The frequency characteristic shown in FIG. 6 is merely an example of the frequency characteristic of the correction unit 203, and the frequency characteristic is a constant error due to limitation of resolution of a circuit constituting the correction unit 203, measurement error, quantization error of operation parameters, etc. have. In addition, the target frequency characteristics are not necessarily completely flat within the 0 to 20 GHz band as shown in FIG. For example, as in the raised cosine type or Bessel low pass filter type, the frequency characteristic (that is, each tap weight) of the correction unit 203 is set such that the smooth right frequency characteristic with less sign interference becomes the target shape. May be In addition to the optical modulator 209, the optical communication system includes components such as the DA converter 204, the output stage amplifier 205, and the signal line, and these components individually have temperature dependency. For this reason, in general, even if only the change in the frequency characteristic of the optical modulator 209 is corrected, the frequency characteristic of the entire optical communication system does not necessarily match the above target shape. Therefore, to improve the transmission performance of the entire optical communication apparatus, not only the temperature dependence of the frequency characteristics of the optical modulator 209 alone as shown in FIG. 5 but also the temperature dependence of the frequency characteristics of the entire optical communication apparatus It is particularly effective to set the frequency characteristic and tap weight of the correction unit 203 so as to match a specific target shape in order to enhance the effect of the present invention.

  Also, in the frequency characteristic of the optical modulator 209 shown in FIG. 5, an example is shown in which the frequency modulation efficiency at DC (0 Hz), that is, the average optical loss of the optical modulator 209 is always 0 dB without changing at the operating temperature. However, it is not limited to this example. For example, the frequency characteristics of the correction unit 203 illustrated in FIG. 6 may be set to compensate for the change in light loss. In this case, although the combined frequency characteristic is always flat in FIG. 7, a change in the operating temperature causes a change in light loss. The influence of such a change in optical loss can be avoided by providing a sufficient level margin between the optical communication devices, and a separate stabilization control is performed so that the output light intensity of the output optical signal 257 becomes constant. You may go and avoid it. Similarly, the correction unit 203 may be configured to separately provide an equalizing circuit that corrects only the change of the frequency characteristic of the light modulator 209 due to the operating temperature and compensates for the change of the light loss. In such a configuration, the correction unit 203 only needs to compensate for the gradual deterioration of the frequency characteristic caused by the change of the operating temperature, so the circuit scale of the correction unit 203 can be greatly reduced, or the correction information storage unit 213 can It becomes possible to reduce the circuit scale and memory size.

  Further, although an example in which a digital filter is used for the circuit constituting the correction unit 203 has been shown, it may be realized by a high speed analog circuit. In this case, the correction unit 203 can be implemented as a high-speed FFE (forward equalizer) or DFE (decision feedback equalizer) of several to several tens of taps. Although FIG. 1 shows an example in which an analog multi-level signal is generated using a high speed DA converter, the present invention is not limited to this example. For example, in the case of binary signals, as it is, in the case of quaternary signals, high-speed binary signals are changed in amplitude and added, and in the case of duobinary signals, high-speed analog operation such as using a delay addition encoder May be used to generate an analog multilevel signal.

  In addition, although an example in which the operating temperature of the light output unit 207 is used as the characteristic data of the light output unit 207 according to the first embodiment has been described, the operation and modulation characteristics of the light output unit 207 may be affected. It may be characteristic data. For example, the bias voltage setting value Vb, the laser driving current setting value If, the amplitude A of the modulation signal 251, the intensity of the laser light input to the optical modulator 209, the optical intensity of the output optical signal 257 output from the optical modulator 209, These two or more characteristic data may be used in combination. In particular, in the case of the EA modulator, the operating temperature, the bias voltage setting Vb, the intensity of the laser light input to the optical modulator 209, and the like are known as characteristic data that greatly affects the operation of the EA modulator. In addition, for example, the characteristics of the light output unit 207, because the photocurrent, the photovoltage, the average light loss, the modulation degree of the modulation signal, the extinction ratio, etc. generated by the light absorption of the light modulator indirectly reflect the modulator operation. It is possible to use as data. In this case, a measuring device for measuring each characteristic data may be provided to acquire the value of the characteristic data, or an indication value of each characteristic data output from the control unit 212 may be acquired as the value of the characteristic data. . It is assumed that a correction information table corresponding to the type of characteristic data is stored in the correction information storage unit 213.

Second Embodiment
FIG. 8 is a view showing an example of the configuration of the optical communication apparatus according to the second embodiment of the present invention. As shown in FIG. 8, in the optical communication device 400 according to the second embodiment, the configuration of the light output unit 407, the configuration of the correction unit 403, the arrangement of the temperature sensor 414, and the constant voltage source 210 are the same as the first embodiment. It is the same except that there is a difference in the presence or absence. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

  The optical communication apparatus 400 according to the second embodiment shows an example in which the direct modulation method using the semiconductor laser 408 is adopted for the light output unit 407, and a change in temperature which is one of the characteristic data of the light output unit 407. The digital information signal 250 is corrected to compensate for the deterioration of the output light signal 257 due to

  The temperature sensor 414 is disposed at an arbitrary position in the optical communication device 400. In the first embodiment, the temperature sensor 214 is disposed in the vicinity of the light output unit 207. However, the temperature sensor 414 need not necessarily be disposed in the vicinity of the light output unit 407 as long as the temperature of the light output unit 407 can be reflected. The temperature sensor 414 is disposed inside the optical communication device 400 because the inside of the optical communication device 400 is maintained at substantially the same temperature if the heat generation of components such as the integrated circuit and the light output unit 407 disposed inside the optical communication device 400 is small. It is enough. Note that a temperature sensor inside the integrated circuit may be used.

  The light output unit 407 receives the laser drive current 452 which is a direct current component and the modulated electrical signal 451 which is a high frequency modulation component, and the light output unit 407 is a combined current obtained by combining both currents by an adder or bias T. The semiconductor laser 408 is driven. The intensity component of the laser beam output from the semiconductor laser 408 driven in this manner is directly modulated by the modulated electrical signal 451, and light intensity modulation proportional to the amplitude of the modulated electrical signal 451 is obtained.

  The correction unit 403 includes a correction circuit 411, a fixed equalization circuit 412, and an interpolation circuit 413. The correction circuit 411 is a circuit similar to the correction circuit 300 of FIG. 2 and the correction circuit 310 of FIG. The interpolation circuit 413 is a circuit provided to save the storage capacity of the correction information storage unit 213. For example, when the correction information selection signal 255 not corresponding to the correction information stored in the correction information storage unit 213 is input, the interpolation circuit 413 reads the correction information before and after the input value with reference to the correction information storage unit 213. The new correction information is generated by the linear interpolation, and is output to the correction circuit 411 as the correction information setting signal 256. Specifically, when an input value indicating 72.4 ° C. not present in the left end row (temperature T) of the correction information table shown in FIG. 4 is input as the correction information selection signal 255, the input value is around 72.4 ° C. The tap weights W1 to W11 of 72 ° C and 73 ° C, which are values, are read out, and the tap weight of 72 ° C and the tap weight of 73 ° C are ratioed to 6: 4 (absolute value ratio of difference between input value and each temperature) Linear interpolation is performed to generate new taps Wi (i = 1 to 11). By using such an interpolation circuit 413, the size of the correction information table stored in the correction information storage unit 213 can be greatly reduced. The algorithm of interpolation by the interpolation circuit 413 is not limited to the above-mentioned example, and, for example, interpolation with a higher-order function with higher accuracy using characteristic data of plural points, two-dimensional interpolation with plural characteristic data, etc. , Various interpolation algorithms may be used.

  The fixed equalization circuit 412 is a circuit for correcting the modulation characteristic change of the light output unit 407 as in the correction circuit 411, but in particular, the fixed portion of the modulation characteristic is provided separately. The number of taps and the number of stages of the correction circuit 411 (for example, FIR filter or frequency domain equalizer) are important parameters that determine the power consumption and frequency resolution of the correction circuit 411. Generally, the longer the length of the correction circuit 411, the more circuits The scale increases and the power consumption increases, but at the same time the frequency resolution increases, and sharp and complex frequency characteristic correction becomes possible. The steep and complex frequency characteristics of the entire optical communication apparatus 400 are generated by the characteristics of the integrated circuit used for reflection and amplification of the high-frequency line, and so are substantially fixed with respect to changes in the characteristic data of the light output unit 407. It is considered that the variation of each of the optical communication devices 400 is large. On the other hand, the frequency characteristics that change according to the characteristic data of the light output unit 407 such as temperature and laser drive current have characteristics that change gradually, and are considered to have common characteristics to the same type of device. Therefore, with regard to the steep and complicated frequency characteristics where the variation among the optical communication devices 400 is large, the fixed correction information which is fixed for each of the optical communication devices 400 is corrected by the fixed equalizing circuit 412 which is set beforehand, and the characteristic data of the light output unit 407 The correction circuit 411 performs correction according to the characteristic data using the correction information table for the gradual frequency characteristics that change due to the above.

  As described above, the correction information storage unit 213 is configured by separating the fixed equalization circuit 412 having a large number of taps and a complicated correction characteristic and the correction circuit 411 having a small number of taps and a variable correction characteristic. The power consumption of the correction circuit 411 can be reduced by significantly reducing the amount of memory required for the circuit or by mounting the fixed equalization circuit 412 with a large number of taps using a dedicated circuit specifically for fixing the correction characteristics. It becomes possible.

  Also, although an example using temperature as the characteristic data of the light output unit 407 according to the second embodiment is shown, other characteristic data may be used as long as it affects the operation of the light output unit 407 and the frequency characteristic. . In the case of the direct modulation method using the semiconductor laser 408 as in the second embodiment, the operating temperature and the laser drive current value are representative as characteristic data that affect the frequency characteristics of the light output unit 407. Further, since these characteristic data are closely related to, for example, the output light intensity, the modulation degree of the modulation signal, the extinction ratio, etc., the output light intensity, the modulation degree, the extinction ratio etc. are observed and used as characteristic data. May be

  The light according to the first embodiment includes any one of the arrangement of the light output unit 407, the correction unit 403, and the temperature sensor 414, or a combination of two according to the second embodiment. The present invention may be applied to a communication device.

Third Embodiment
FIG. 9 is a view showing an example of the configuration of the optical communication apparatus according to the third embodiment of the present invention. As shown in FIG. 9, the optical communication apparatus 500 according to the third embodiment has functions as an optical transmitter and an optical receiver, and the configuration as the optical transmitter is the same as the optical communication apparatus 200 according to the first embodiment. It is similar. Therefore, the first embodiment is the same as the first embodiment except that the configuration including the light transmitting unit 510 and the light receiving unit 520 and the integrated circuit 530 are different. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

  The optical communication apparatus 500 according to the third embodiment includes the light transmitting unit 510 and the light receiving unit 520, and a part of the light transmitting unit 510 and the light receiving unit 520 are disposed on the same integrated circuit 530. The integrated circuit 530 is responsible for modulation / demodulation of the optical multilevel signal and overall control of the optical multilevel signal, and the multilevel encoding unit 202, correction unit 203, DA converter 204, control unit 212, correction information storage unit 213, constant voltage source A constant current source 211, an AD converter 522, a reception side adaptive equalization unit 523, and a decoding unit 524 are included. The integrated circuit 530 is connected to the output stage amplification unit 205, the bias T 206, and the semiconductor laser 208 through an output terminal (output pin) 581. The output terminal 581 may be a physical dedicated pin or a signal output terminal for communication such as I2C or SPI shared among a plurality of devices. In addition, the temperature sensor signal 253 output from the temperature sensor 214 disposed in proximity to the light modulator 209 is input to the integrated circuit 530 through the input terminal 582 of the sensor signal provided in the integrated circuit 530. . The input terminal 582 may be a physical pin or a signal input terminal for communication.

  The configuration of the optical communication apparatus 500 shown in FIG. 9 is an example, and each component can be freely disposed inside or outside the integrated circuit 530 if manufacturing convenience and the like are satisfied. For example, the light modulator 209, the semiconductor laser 208, etc. may be manufactured using the same silicon process as the integrated circuit 530 such as silicon photonics technology, or may be integrally manufactured with the integrated circuit 530 by a method such as hybrid integration. . In addition, the constant current source 211, the constant voltage source 210, the DA converter 204, and the like disposed inside the integrated circuit 530 can be appropriately disposed outside the integrated circuit.

  The light receiving unit 520 includes a photodiode 521, an AD converter 522, a reception side adaptive equalization unit 523, and a decoding unit 524. The reception intensity modulation signal 572 which is a reception light signal input from the input optical fiber 571 is photoelectrically converted into an electric signal by the photodiode 521, and is input to the AD converter 522 in the integrated circuit 530. The received electrical signal is converted to a digital information signal 577 by the AD converter 522, and the error is adaptively equalized by the reception side adaptive equalization unit 523. This is a deterioration of the waveform mainly due to the frequency characteristics of the optical fiber transmission line and the reception side circuit. After the correction, the digital information signal 577 is restored by the decoding unit 524, and the digital information signal 577 is output to the outside of the optical communication apparatus 500 as a reception information signal.

  The reception side adaptive equalization unit 523 mainly corrects the deterioration of the transmission performance in the optical fiber transmission line and the light receiving unit 520, and a part of the change in the modulation characteristic of the light output unit 207. Specifically, the reception side adaptive equalization unit 523 operates to maximize the eye opening of the received signal waveform by, for example, a blind algorithm. Therefore, when the distortion of the output signal waveform is increased due to the deterioration of the modulation characteristic of the light output unit 207 and the eye opening of the received signal waveform input to the light receiving unit is reduced, the reception side adaptive equalization unit 523 Convergence is difficult and may cause significant transmission degradation. In addition, when the reception side adaptive equalization unit 523 equalizes the large band degradation generated in the light output unit 207, noise is excessively amplified, and a phenomenon of noise emphasis occurs in which the quality of the transmission signal is greatly degraded. . Since the resolution of the AD converter is also finite (usually about 6 to 8 bits), if the reception side adaptive equalization unit 523 performs excessive band equalization, the signal SN may be degraded. This means that if the reception-side adaptive equalization unit 523 performs correction such that high-frequency components are amplified, the amplitude of the low-frequency signal is relatively attenuated, so the effective amplitude of the signal is attenuated and the signal SN is to degrade. As described above, since the correction amount by the reception side adaptive equalization unit 523 is limited, it is desirable to prevent the deterioration of the output optical signal 257 on the optical transmitter side as much as possible. When the optical receiver is realized by high-speed analog signal processing, no compensation function exists at first, only a few taps of FFE / DFE compensation function only, or the compensation function is not sufficient. Is common.

  Therefore, by using the optical communication device 500 including the correction unit 203 of the light transmission unit 510 as shown in FIG. 9 and the reception side adaptive equalization unit 523 of the light reception unit 520, transmission in the entire optical communication device 500. It is possible to suppress the deterioration of the performance. In the optical transmission device 500, an unexpected change in modulation characteristics may occur in the light output unit 207 due to an environment (temperature, vibration, heat) in use, deterioration with time, and the like. For example, when deterioration of the output light signal occurs due to a change in characteristic data other than the characteristic data to be corrected by the correction unit 203 of the light transmission unit 510, an unexpected change in modulation characteristic of the light output unit 207 occurs. In this case, by using the correction unit 203 of the light transmission unit 510 and the reception side adaptive equalization unit 523 of the light reception unit 520 in combination, the correction unit 203 of the light transmission unit 510 may change the characteristics of the light output unit 207. The deterioration of the output light signal 257 can be corrected, and the reception side adaptive equalization unit 523 can correct the deterioration of the output light signal 257 that can not be completely corrected on the light transmission unit side and the change component of the transmission performance. Furthermore, when the correction unit 203 of the light transmission unit 510 and the reception side adaptive equalization unit 523 of the light reception unit 520 are used in combination, the interval of the characteristic data in the correction information storage unit 213 is set roughly to save memory. It is possible to

Fourth Embodiment
FIG. 10 is a diagram showing an example of the configuration of the optical communication device according to the fourth embodiment of the present invention. As shown in the figure, the optical communication apparatus according to the fourth embodiment is the same as the optical communication apparatus 500 according to the third embodiment except that the configuration of the optical transmission unit 610 is different. . Therefore, the same components as those of the third embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

  Similar to the optical communication apparatus 400 according to the second embodiment, the optical communication apparatus 600 according to the fourth embodiment adopts the direct modulation method using the semiconductor laser 408 for the light output unit 407 and uses it for correction by the correction unit 603. The example which made two types of characteristic data is shown. Since the modulation characteristics of the semiconductor laser 408 are very strongly dependent on the operating temperature and the laser drive current setting value If, one of the temperature or the laser drive current setting value If is made a constant value, and the correction unit is based on the other value change. It is ideal to make a correction according to 603. On the other hand, if the operating temperature range is wide, it becomes possible to reduce the amount of control of the cooler and heater used to stabilize the temperature of the semiconductor laser 408 and to reduce the power accordingly. In addition, since the laser light intensity output from the semiconductor laser 408 is determined by the laser drive current setting value If, in the case of preventing a change in the laser light intensity due to aging or environmental change, or when intentionally changing the laser light intensity. It is also necessary to change the laser drive current setting value If. Therefore, the control unit 212 of the optical communication apparatus 600 according to the fourth embodiment determines the first characteristic data signal (temperature) 683 based on the laser drive current setting value If and the temperature sensor signal 253 from the temperature sensor 214. The second characteristic data signal (laser current value) 684 is output to the interpolation unit 413. Then, the interpolation unit 413 refers to the correction information storage unit 213, and outputs a correction information setting signal 656 indicating correction information corresponding to the values of both characteristic data to the correction circuit 411.

  Such correction using a plurality of characteristic data is also applicable to other light modulators. For example, in the electro-absorption modulator integrated light source, the modulation characteristic changes depending on the operating temperature and the bias voltage, so that it is possible to effectively correct the modulation characteristic with the same configuration. Further, the modulation characteristic may be kept constant by changing the amplitude A and the laser drive current setting value If (or the bias voltage setting value Vb or the like) at the same time as using the operating temperature as the characteristic data. In such a configuration, it is possible to store correction information regarding each characteristic data in the correction information storage unit 213.

  Further, the integrated circuit 530 is provided with a correction information input terminal 685 for writing the correction information into the correction information storage unit 213 from the outside. By doing this, it becomes possible to rewrite the correction information that matches the semiconductor laser, the optical modulator, the driver, etc. used for the optical communication device 600 later in the correction information storage unit 213, and more accurate correction is possible. It becomes. Further, the correction information input terminal 687 of the same correction information is disposed in the optical communication apparatus 600, whereby after the entire optical communication apparatus 600 is assembled, correction characteristics are calculated from measured data in consideration of the entire characteristics, and individual light is calculated. It becomes possible to set correction information according to the characteristics of the communication device 600, and it is possible to further enhance the correction effect.

Fifth Embodiment
FIG. 11 is a diagram showing an example of the configuration of the optical communication device according to the fifth embodiment of the present invention. As shown in FIG. 11, the optical communication apparatus 700 according to the fifth embodiment is the same as the optical communication apparatus 500 according to the third embodiment except that the configuration of the integrated circuit is different. . Therefore, the same components as those of the third embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

  The optical communication device according to the fifth embodiment includes an integrated circuit 790, a signal integrated circuit 791-1, and a signal integrated circuit 791-2, and the signal integrated circuits 791-1 and 791-2 and the integrated circuit 790. And different integrated circuits. The integrated circuit 790 operates at a very low speed as compared with the signal processing integrated circuits 791-1 and 791-2, while it requires complex functions such as control of signal levels, so it is a general purpose processor with high versatility. To be realized.

  The correction information storage unit 213 is disposed outside the integrated circuit 790, and the correction information storage unit 213 and the integrated circuit 790 are connected via the storage unit read / write communication path 792. The correction information storage unit 213 is a general memory circuit such as a nonvolatile serial / parallel EPROM, a flash memory, etc., and may be removable if necessary. Further, the correction information storage unit 213 can be removed, and a usage form in which the correction information is written after the writing is also possible.

  Although FIG. 11 does not explicitly show the input terminal for inputting the correction information to the correction information storage unit 213, the control unit 212 receives the correction information from the outside as a part of the external communication signal 714 and stores it. It writes in the correction information storage unit 213 via the unit read / write communication path 792. Thus, the external communication signal 714 and its connection terminal substantially play a role equivalent to the correction information input terminal 685 or the correction information input terminal 687 provided in the integrated circuit 530 in the fourth embodiment of FIG. . In addition, the control unit 212 may acquire the characteristic data from the outside via the external communication signal 714.

  Further, although the interpolation unit is not explicitly shown in FIG. 11, the control unit 212 may share its function. Although the signal processing integrated circuit 791-1 and the signal processing integrated circuit 791-2 are separately illustrated in FIG. 11, both may be the same integrated circuit.

  The present invention is not limited to the above-described embodiment. For example, the optical communication apparatus may be provided with a temperature regulator such as a heater or a cooler used for temperature stabilization of the light output unit. In this case, if the optical communication device is always kept at the predetermined temperature, the power consumption increases. Therefore, setting may be made to allow temperature change within the predetermined range from the predetermined temperature. In addition, there is an operating temperature range in which the EA modulator etc. operates normally, and temperature adjustment may be performed when the operating temperature range is exceeded, and temperature adjustment may be stopped when in the operating temperature range. . As described above, the present invention can be applied to the case where temperature fluctuation occurs while the temperature regulator is not operating even if the optical communication device is provided with the temperature regulator.

  Furthermore, in the above embodiment, the intensity modulation method has been mainly described, but the invention is not limited to this. For example, it is driven by a phase modulation method applying an MZ modulator as an external modulator or an electric field modulation method applying an IQ modulator. Even in the case of

  100, 200, 400, 500, 600, 700 Optical communication device, 101, 250 digital information signal, 102, 202 multi-level coding unit, 103, 205 output stage amplification unit, 104, 206 bias T, 105, 209 light modulation , 106, 208, 408 semiconductor laser, 107, 258 output optical fiber, 108 multi-level modulation light, 109, 210 constant voltage source, 110, 211 constant current source, 111, 251 modulation signal, 112, 252, 452 laser drive Current, 113, 212 control unit, 115, 204 DA converter, 203, 403, 603 correction unit, 207, 407 light output unit, 213 correction information storage unit, 214, 414 temperature sensor, 254, 714 external communication signal, 253 temperature Sensor signal, 255 correction information selection signal, 256, 656 correction information setting signal, 257 output light signal, 00, 310, 411 correction circuit, 301 delay circuit, 302 real number tap multiplier, 303 adder, 311 FFT circuit, 312 complex tap multiplier, 313 inverse FFT circuit, 412 fixed equalization circuit, 413 interpolator, 451 modulation electric Signal, 510, 610 Optical transmitter, 520 Optical receiver, 521 Photodiode, 522 AD converter, 523 Receiver-side adaptive equalizer, 524 Decoder, 530, 790 Integrated circuit, 571 Input optical fiber, 572 Received intensity modulated signal , 577 digital information signal, 581 output terminal, 582 input terminal, 683 first characteristic data signal, 684 second characteristic data signal, 685, 687 correction information input terminal, 791-1, 791-2 integrated circuit for signal, 792 Storage unit write communication path.

Claims (11)

A converter for converting a digital signal used to modulate an optical signal to be output into an analog multilevel signal;
A light output unit that outputs the light signal modulated by the analog multilevel signal;
A characteristic data acquisition unit that acquires characteristic data of the light output unit;
A correction unit that corrects the digital signal converted by the conversion unit so as to compensate for the modulation characteristic change of the light output unit according to the acquired characteristic data;
A storage unit that stores correction information for correcting the digital signal according to the characteristic data;
Only including,
The characteristic data acquisition unit acquires an operating temperature of the light output unit as the characteristic data,
The correction unit acquires correction information according to the acquired characteristic data from the storage unit and superimposes the correction information on the digital signal.
The correction information is a value for correcting the frequency characteristic of the light output unit which changes in accordance with the operating temperature.
An optical communication device characterized by The optical communication device according to claim 1 ,
A temperature sensor for measuring an operating temperature of the light output unit;
It is characterized by A converter for converting a digital signal used to modulate an optical signal to be output into an analog multilevel signal;
A light output unit that outputs the light signal modulated by the analog multilevel signal;
A characteristic data acquisition unit that acquires characteristic data of the light output unit;
A correction unit that corrects the digital signal converted by the conversion unit so as to compensate for the modulation characteristic change of the light output unit according to the acquired characteristic data;
Including
The characteristic data acquisition unit acquires a drive current value for driving a light source of the light signal or a bias voltage set in the light output unit.
An optical communication device characterized by The optical communication device according to claim 3,
A temperature sensor for measuring an operating temperature of the light output unit;
It is characterized by An optical communication apparatus according to claim 1 or 2 ,
When the correction information corresponding to the value of the acquired characteristic data is not stored in the storage unit, the information corresponding to the value of the acquired characteristic data based on the correction information stored in the storage unit And an interpolation unit that interpolates correction information and outputs the result to the correction unit.
It is characterized by An optical communication apparatus according to any one of claims 1, 2 or 5 , wherein
The correction information is a value for flattening the frequency characteristic of the light output unit.
It is characterized by The optical communication device according to claim 6 , wherein
The correction unit is a digital filter that flattens the frequency characteristic of the light output unit, and the correction information is a set value that determines the transfer characteristic of the digital filter to flatten the frequency characteristic of the light output unit. ,
It is characterized by The optical communication device according to any one of claims 1, 2, 6, or 7 .
The storage unit is configured of a storage medium in which the correction information can be rewritten or the storage unit can be exchanged.
It is characterized by The optical communication device according to claim 8 , wherein
The signal processing apparatus further includes a signal terminal for writing the correction information in the storage unit, or a communication unit.
It is characterized by An optical communication apparatus according to claim 1 or 2,
And the equivalent circuit which compensates for the change of the light loss so that the output light intensity of the light signal becomes constant,
The correction unit compensates only for the change of the frequency characteristic caused by the change of the operating temperature.
It is characterized by An optical communication apparatus according to any one of claims 1 to 10, wherein
A photoelectric conversion unit that converts a received optical signal received from the outside into an electrical signal;
An adaptive equalization unit that equalizes an error of the converted electrical signal;
A decoding unit that decodes the equalized electrical signal and outputs it as an information signal;
Further include,
It is characterized by

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