JP6380403B2 - Carrier frequency deviation estimation apparatus and carrier frequency deviation estimation method - Google Patents

Description

  The present invention relates to a carrier frequency deviation estimation apparatus and a carrier frequency deviation estimation method, and more particularly to a carrier frequency deviation estimation apparatus and a carrier frequency deviation estimation method used in an optical communication system.

  Due to the spread of the Internet, the traffic volume of the backbone communication system is rapidly increasing. Therefore, practical application of an ultra-high-speed optical communication system exceeding 100 Gbps is expected. As a technique for realizing such an ultra-high-speed optical communication system, a digital coherent system combining an optical phase modulation system and a polarization multiplexing / demultiplexing technique has attracted attention (for example, see Patent Document 1).

  The conventionally used light intensity modulation method performs data modulation on the light intensity of the transmission laser beam, whereas the optical phase modulation method performs data modulation on the phase of the transmission laser beam. As the optical phase modulation method, a QPSK (Quadrature Phase Shift Keying) method, a 16QAM (Quadrature Amplitude Modulation) method, and the like are known.

  In the polarization multiplexing / demultiplexing technique, in an optical transmitter, two independent single-polarized optical signals whose carrier waves are arranged in the same frequency band and whose polarization states are orthogonal to each other are polarization-multiplexed. Then, in the optical receiver, the above-described two independent single-polarized optical signals are separated from the received optical signal. With such a configuration, according to the polarization multiplexing / demultiplexing technique, a double transmission rate can be realized.

  FIG. 5 is a block diagram showing a configuration of an optical receiver 500 using the related digital coherent scheme described above. The local oscillation light generation unit 501 transmits local oscillation light having the same frequency band as the received optical signal. The received optical signal and the local oscillation light are input to the 90 degree hybrid 510. Eight optical signals output from the 90-degree hybrid 510 are converted into electrical signals by the photoelectric conversion units 521 to 524, and further converted from analog signals to digital signals by AD converters (Analog-to-Digital Converter: ADC) 531 to 534. Is converted to The four digital signals generated in this way correspond to the next signal component of the received optical signal. That is, the real part and imaginary part of the signal component (X polarization signal) parallel to the polarization axis of the 90-degree hybrid 510, and the real part of the signal component (Y polarization signal) orthogonal to the polarization axis of the 90-degree hybrid 510, It is a signal corresponding to the imaginary part. The digital signals generated by the AD converters 531 to 534 are demodulated by the digital signal processing unit 540 and then decoded into bit strings by the symbol identification units 551 and 552.

  Next, the operation of digital signal processing in the optical receiver 500 using the related digital coherent method will be described in detail.

  FIG. 6 is a block diagram showing the configuration of the digital signal processing unit 540. An X polarization signal is generated as a complex number from the digital signal input from the AD converters 531 and 532 to the X polarization signal generation unit 611. Similarly, a Y polarization signal is generated as a complex number from a digital signal input from the AD converters 533 and 534 to the Y polarization signal generation unit 612.

  The frequency deviation coarse compensation units 621 and 622 compensate for the deviation (optical carrier frequency deviation) between the center frequency of the received optical signal and the transmission frequency of the local oscillation light with rough accuracy. This is because when the optical carrier frequency deviation becomes large due to the type of phase modulation method of the received optical signal and the optical SN (signal-to-noise) ratio, the polarization separation unit 640 disposed in the subsequent stage is normally operated. This is because it may not work. Another reason is that when a matched filter is used in the waveform distortion compensators 631 and 632 arranged in the subsequent stage, signal quality may deteriorate if there is a deviation between the received optical signal and the center frequency of the matched filter. is there. If the above-described problem does not occur, the frequency deviation rough compensation units 621 and 622 can be omitted.

  FIG. 7 is a block diagram illustrating a configuration example of the frequency deviation rough compensation unit 620 (621, 622). The frequency deviation rough estimation unit 623 estimates the frequency deviation using one of the two branched input signals, and the phase compensation amount calculation unit 624 calculates the phase compensation amount. The other signal waits in the delay unit 625 until the phase compensation amount is calculated. The phase compensation amount is calculated as the sum of products of the frequency deviation estimated value and the unit sample time (the reciprocal of the sampling rate in the AD converters 531 to 534). The input signal that has been waiting in the delay device 625 is phase rotated clockwise by the calculated phase compensation amount to compensate for the frequency deviation.

  The configuration of the frequency deviation rough compensation unit 620 is not limited to that shown in FIG. 7, and a configuration in which the frequency deviation is compensated by shifting the optical spectrum in the frequency direction in the frequency domain as shown in FIG. 8 can also be used. . In the configuration illustrated in FIG. 8, the input signal is subjected to fast Fourier transform (FFT) in the FFT unit 626 to a frequency domain signal. Thereafter, the data shift unit 627 frequency-shifts in the frequency direction opposite to the frequency deviation estimated value, and thereafter, the data is converted into a time-domain signal by an inverse fast Fourier transform (IFFT) process in the IFFT unit 628. . Note that computation distortion may occur at both ends of the processing units in the FFT and IFFT due to the assumption that the FFT and IFFT assume repeated signals. In such a case, processing such as overlap may be performed separately. .

  Further, as described in Patent Document 2, when using the local oscillation light generation unit 501 capable of controlling the oscillation frequency, the oscillation frequency of the local oscillation light is controlled in the direction opposite to the frequency deviation estimated value. It is also possible to compensate for the frequency deviation.

  An example of the configuration of the frequency deviation rough estimation unit 623 that roughly estimates the frequency deviation is described in Patent Document 2. FIG. 9 is a block diagram showing a configuration of a related frequency deviation rough estimation unit 623 described in Patent Document 2. The related frequency deviation rough estimation unit 623 shown in FIG. 9 calculates a product of two consecutive samples for each of the real part and the imaginary part of the input signal, calculates the difference between them, and then moves. A low-pass filter that performs processing such as averaging is transmitted. Since it is clear by simulation that the output value of the low-pass filter and the frequency deviation are proportional to each other within a predetermined frequency deviation range, the frequency deviation is estimated from the output value of the low-pass filter. It is possible.

  The waveform distortion compensators 631 and 632 illustrated in FIG. 6 transmit chromatic dispersion compensation, waveform shaping using a matched filter, nonlinear waveform distortion compensation, and the like to the signals input from the frequency deviation coarse compensation units 621 and 622. Various compensation processes are performed to improve quality.

  The polarization separation unit 640 separates the received optical signal into two digital signals corresponding to two independent optical signals that are polarization-multiplexed in the optical transmitter. As the polarization separation processing algorithm, CMA (Continuous Modulus Algorithm) or DD-LMS (Decision Decided Last Mean Square) can be used.

  The signals output from the polarization separation unit 640 are converted into signals that are oversampled by a factor of 1 in a state where the sample timing is optimized by the resampling units 651 and 652, respectively. The resampling units 651 and 652 can be arranged at other positions such as immediately before the polarization separation unit 640, but oversampling of signals input to the frequency deviation compensation units 661 and 662 is 1 time. There is a need.

  The frequency deviation compensation units 661 and 662 completely compensate for the optical carrier frequency deviation that the frequency deviation coarse compensation units 621 and 622 could not compensate. The phase deviation compensation units 671 and 672 compensate for the optical phase deviation.

  FIG. 10 shows the configuration of the frequency deviation compensation unit 660 (661, 662). The configuration of the frequency deviation compensator 660 is obtained by replacing the frequency deviation coarse estimator 623 included in the frequency deviation coarse compensator 620 shown in FIG. 7 with a frequency deviation estimator 663, and the other configurations are the same. That is, the frequency deviation compensation unit 660 includes a delay unit 625, a frequency deviation estimation unit 663, and a phase compensation amount calculation unit 624.

  FIG. 11 shows an example of the frequency deviation estimation unit 663. The configuration of the frequency deviation estimator 663 shown in FIG. 11 is a configuration that employs an algorithm called an M-th power algorithm or a Viterbi algorithm. In order to use this algorithm, it is necessary to input a signal that has been oversampled by a factor of 1 in a state where the sample timing is optimized. Since a signal oversampled by 1 is used, there is a limit to the range of frequency deviation that can be compensated.

  By using a digital coherent method combining the optical phase modulation method described above and polarization multiplexing / demultiplexing technology, it is possible to realize an ultra-high-speed optical communication system of 100 Gbps.

JP 2012-248944 A (paragraphs “0022” to “0052”) JP 2009-038801 A (paragraphs “0002” to “0015”, FIG. 1)

  However, the related frequency deviation estimation unit described above has a problem that it is difficult to accurately estimate the frequency deviation over a wide range because the range of the frequency deviation that can be estimated is limited. Furthermore, since it is necessary to use a large number of arithmetic units, there is a problem that when mounted on an integrated circuit, the circuit scale increases and power consumption increases.

  Thus, the related carrier frequency deviation estimation apparatus has a problem that it is difficult to accurately estimate the frequency deviation over a wide range without causing an increase in power consumption.

  An object of the present invention is to solve the above-described problem that it is difficult to accurately estimate a frequency deviation over a wide range without causing an increase in power consumption. It is to provide an estimation method.

  The carrier frequency deviation estimating apparatus according to the present invention includes a resampling unit that converts an input signal into an oversampling signal that is oversampled at a multiple of the symbol rate of the input signal, and two temporally continuous signals included in the oversampling signal. A time variation vector calculating means for calculating a time variation vector between the sample signals, a filter means for calculating an average value of the time variation vectors, a frequency deviation estimating means for calculating a carrier frequency deviation estimated value based on the average value, and Have

  The carrier frequency deviation compensation device of the present invention has a carrier frequency deviation estimation device for calculating a carrier frequency deviation estimation value, and a frequency deviation compensation means for compensating the carrier frequency deviation of the input signal based on the carrier frequency deviation estimation value, The carrier frequency deviation estimating apparatus includes a resampling unit that converts an input signal into an oversampling signal that is oversampled at a multiple of a symbol rate of the input signal, and two temporally continuous sample signals included in the oversampling signal. A time variation vector calculating unit that calculates a time variation vector between the filter unit, a filter unit that calculates an average value of the time variation vector, and a frequency deviation estimation unit that calculates a carrier frequency deviation estimated value based on the average value.

  According to the carrier frequency deviation estimation method of the present invention, an input signal is converted into an oversampling signal obtained by oversampling at a multiple of the symbol rate of the input signal, and two temporally continuous sample signals included in the oversampling signal are converted. Are calculated, an average value of the time variation vectors is calculated by filtering, and a carrier frequency deviation estimated value is calculated based on the average value.

  According to the carrier frequency deviation estimation apparatus and the carrier frequency deviation estimation method of the present invention, it is possible to accurately estimate the frequency deviation over a wide range without causing an increase in power consumption.

It is a block diagram which shows the structure of the carrier frequency deviation estimation apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the result of having calculated the relationship between a frequency deviation and a declination by numerical simulation using the carrier wave frequency deviation estimation apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows another result which computed the relationship between a frequency deviation and a declination by numerical simulation using the carrier wave frequency deviation estimation apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the carrier frequency deviation estimation apparatus which concerns on the 2nd Embodiment of this invention, and the carrier frequency deviation compensation apparatus using the same. It is a block diagram which shows the structure of the optical receiver using a related digital coherent system. It is a block diagram which shows the structure of the digital signal processing part with which the optical receiver using a related digital coherent system is provided. It is a block diagram which shows the structure of the frequency deviation rough compensation part with which a related digital signal processing part is provided. It is a block diagram which shows another structure of the frequency deviation rough compensation part with which a related digital signal processing part is provided. It is a block diagram which shows the structure of the related frequency deviation rough estimation part. It is a block diagram which shows the structure of the frequency deviation compensation part with which a related digital signal processing part is provided. It is a block diagram which shows the structure of the frequency deviation estimation part with which a related digital signal processing part is provided.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a carrier frequency deviation estimation apparatus 100 according to the first embodiment of the present invention. The carrier frequency deviation estimation apparatus 100 includes resampling means 110, time variation vector calculation means 120, filter means 130, and frequency deviation estimation means 140.

  The resampling unit 110 converts the input signal into an oversampling signal that is oversampled at a multiple of the symbol rate of the input signal. The time variation vector calculation means 120 calculates a time variation vector between two temporally continuous sample signals included in the oversampling signal. The filter means 130 calculates the average value of the time variation vectors. Then, the frequency deviation estimating means 140 calculates a carrier frequency deviation estimated value based on this average value.

  As shown in FIG. 1, the time variation vector calculation means 120 can be configured to include a delay device, a complex conjugate device, and an accumulator. Here, the delay unit delays the sample signal that precedes in time among the two sample signals output by the resampling means 110 by one sample time. The complex conjugate unit calculates a complex conjugate of the sample signal output from the delay unit and outputs a complex conjugate sample signal. Then, the accumulator calculates the product of the subsequent sample signal of the two sample signals and the complex conjugate sample signal.

  Further, as shown in FIG. 1, the frequency deviation estimating means 140 can be configured to include a declination angle calculating unit 141 and a frequency deviation calculating unit 142. Here, the deflection angle calculation unit 141 calculates the deflection angle from the average value of the time variation vectors calculated by the filter unit 130. Then, the frequency deviation calculation unit 142 calculates a carrier frequency deviation estimated value based on the relationship between the deviation angle and the carrier frequency deviation.

  Next, the operation of the carrier frequency deviation estimation apparatus 100 according to this embodiment will be described.

  As described above, the carrier frequency deviation estimating apparatus 100 converts the input signal into a signal having a predetermined sampling rate in the resampling means 110. Thereafter, the time variation vector calculation means 120 calculates the product of the complex conjugate of the sample at a certain time and the immediately preceding sample. The value of this product means a vector representing the time variation of the optical signal per one sample time (reciprocal of the sampling rate), that is, a time variation vector.

  The filter means 130 can be a low-pass filter that performs moving average processing or the like. Then, after the time variation vector described above passes through the filter means 130, the deflection angle calculator 141 calculates the deflection angle. Since this declination has a one-to-one correspondence with the frequency deviation as will be described later, the frequency deviation can be estimated.

  The relationship between the above-described declination and frequency deviation will be described with reference to FIG.

  FIG. 2 is a diagram illustrating a result of calculating the relationship between the frequency deviation and the deviation angle of the optical signal by a numerical simulation using the carrier frequency deviation estimation apparatus 100 according to the present embodiment. A 128 Gbps polarization multiplexed QPSK optical signal was used as the optical signal. FIG. 2 shows the results when oversampling after resampling is set to 1 ×, 2 ×, and 4 ×, respectively. As can be seen from FIG. 2, when the oversampling is performed at 2 times and 4 times, the frequency deviation and the declination are proportional to each other in a wide frequency range. On the other hand, it can be seen that there is no proportional relationship when oversampling is performed by a factor of 1.

  FIG. 3 shows the result of calculating the relationship between the frequency deviation and the deflection angle of an optical signal by a numerical simulation for a 256 Gbps polarization multiplexed 16QAM optical signal using the carrier frequency deviation estimation apparatus 100 according to the present embodiment. . Similar to the results shown in FIG. 2, when the oversampling is performed twice or four times, it can be seen that the frequency deviation and the declination are proportional to each other in a wide frequency range. On the other hand, it can be seen that there is no proportional relationship when oversampling is performed by a factor of 1.

  Based on the simulation results shown in FIGS. 2 and 3, the operation of the carrier frequency deviation estimation apparatus 100 according to the present embodiment will be described.

  As described above, in the carrier frequency deviation estimating apparatus 100 according to the present embodiment, the phase rotation amount caused by the frequency deviation slightly present in the time variation vector is extracted by the low-pass filter as the filter unit 130. Here, when the sampling rate is low, in other words, when oversampling is as small as 1 time, information on the amount of phase rotation included in the time variation vector is extremely small. Therefore, the relationship between the frequency deviation and the declination does not have a one-to-one correspondence, and as a result, it is difficult to normally estimate the frequency deviation. On the other hand, the carrier frequency deviation estimation apparatus 100 according to the present embodiment is configured to perform oversampling by multiple times in the resampling means 110, so that the frequency deviation and the deflection angle are in a proportional relationship. Therefore, it is possible to estimate the frequency deviation over a wide range. In addition, since the number of arithmetic units required for mounting does not increase, the circuit scale and power consumption do not increase.

  Next, the carrier frequency deviation estimation method according to this embodiment will be described. In the carrier frequency deviation estimation method of this embodiment, first, an input signal is converted into an oversampling signal that is oversampled at a multiple of the symbol rate of the input signal. Subsequently, a temporal variation vector between two temporally continuous sample signals included in the oversampling signal is calculated. Then, an average value of time variation vectors is calculated by filtering, and a carrier frequency deviation estimated value is calculated based on the average value.

  Also by the carrier frequency deviation estimation method according to the present embodiment, the frequency deviation and the declination are in a proportional relationship, and therefore it is possible to compensate for the frequency deviation over a wide range.

  As described above, according to the carrier frequency deviation estimating apparatus and the carrier frequency deviation estimating method of the present embodiment, the frequency deviation can be accurately estimated over a wide range without causing an increase in power consumption.

  Next, a carrier frequency deviation compensating apparatus using the carrier frequency deviation estimating apparatus 100 according to the present embodiment will be described. The carrier frequency deviation compensating apparatus of this embodiment includes a carrier frequency deviation estimating apparatus 100 that calculates a carrier frequency deviation estimated value, and a frequency deviation compensating unit that compensates the carrier frequency deviation of the input signal based on the carrier frequency deviation estimated value. Have. The configuration of the carrier frequency deviation estimation apparatus 100 is as described above with reference to FIG.

  Here, the configuration of the carrier frequency deviation compensator according to the present embodiment may be a configuration in which the frequency deviation rough estimator 623 is replaced with the carrier frequency deviation estimator 100 in the frequency deviation coarse compensator 620 shown in FIG. it can. That is, the frequency deviation compensation means included in the carrier frequency deviation compensation device of the present embodiment can be configured to include a phase compensation amount calculation unit and a phase compensation unit.

  The phase compensation amount calculation unit calculates the phase compensation amount for the input signal based on the estimated carrier frequency deviation value calculated by the carrier frequency deviation estimation apparatus 100 and the unit sampling time. The phase compensator compensates for the carrier frequency deviation by rotating the phase of the input signal by the phase compensation amount.

  Specifically, as described with reference to FIG. 7, the carrier frequency deviation estimation apparatus 100 uses one of the two branched input signals among the input signals input to the carrier frequency deviation compensation apparatus of the present embodiment. The frequency deviation is estimated, and the phase compensation amount calculation unit (624) calculates the phase compensation amount. The other signal waits in the delay unit (625) included in the phase compensation unit until the phase compensation amount is calculated. The phase compensation amount is calculated as the sum of products of the frequency deviation estimated value and the unit sample time. The input signal waiting in the delay unit (625) is phase-shifted clockwise by the calculated phase compensation amount to compensate for the frequency deviation.

  Further, the configuration of the carrier frequency deviation compensator of this embodiment can be configured such that the frequency deviation rough compensator 620 shown in FIG. . That is, a configuration in which the frequency deviation is compensated by shifting the optical spectrum in the frequency direction in the frequency domain can also be used.

  Specifically, the frequency deviation compensation means provided in the carrier frequency deviation compensation device of the present embodiment can be configured to include an FFT unit (626), a data shift unit (627), and an IFFT unit (628). . Here, the FFT unit (626) performs a fast Fourier transform process on the input signal of the carrier frequency deviation compensator. The data shift unit (627) shifts the frequency of the fast Fourier transform processed input signal output from the FFT unit (626) by the carrier frequency deviation estimation value calculated by the carrier frequency deviation estimation apparatus 100. The IFFT unit (628) performs an inverse Fourier transform process on the output signal of the data shift unit (627).

  According to the carrier frequency deviation compensating apparatus of the present embodiment described above, a wide range of carrier frequency deviation estimated values can be obtained by the carrier frequency deviation estimating apparatus 100, so that the frequency deviation can be compensated over a wide range.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the present embodiment, a case where a polarization multiplexing / demultiplexing technique is used will be described. FIG. 4 is a block diagram showing a configuration of a carrier frequency deviation estimating apparatus 200 and a carrier frequency deviation compensating apparatus 300 using the same according to the second embodiment of the present invention.

  The carrier frequency deviation estimation apparatus 200 according to the present embodiment includes a first carrier frequency deviation estimation apparatus 211, a second carrier frequency deviation estimation apparatus 212, and frequency deviation averaging means 220. Here, the configurations of the first carrier frequency deviation estimation device 211 and the second carrier frequency deviation estimation device 212 are the same as the configurations of the carrier frequency deviation estimation device 100 according to the first embodiment.

  The first carrier frequency deviation estimation device 211 and the second carrier frequency deviation estimation device 212 are respectively a first polarization input signal (X polarization input signal) and a second polarization input signal (Y polarization input signal). ) As an input signal. Here, the first polarization input signal and the second polarization input signal detect a polarization multiplexed optical signal obtained by polarization-multiplexing two single polarization optical signals which are arranged in the same frequency band and orthogonal to each other. Can be obtained.

  The first carrier frequency deviation estimation device 211 and the second carrier frequency deviation estimation device 212 calculate a first carrier frequency deviation estimation value and a second carrier frequency deviation estimation value, which are carrier frequency deviation estimation values, respectively. Output to the frequency deviation averaging means 220. Then, the frequency deviation averaging means 220 calculates a frequency deviation average value that is an average of the first carrier frequency deviation estimated value and the second carrier frequency deviation estimated value.

  Next, the carrier frequency deviation estimation method according to this embodiment will be described. In the carrier frequency deviation estimation method of this embodiment, the first polarization input signal and the second polarization input signal are used as input signals. Here, the first polarization input signal and the second polarization input signal are detected from a polarization multiplexed optical signal obtained by polarization multiplexing two single polarization optical signals that are arranged in the same frequency band and orthogonal to each other. It is obtained by doing.

  Then, a first carrier frequency deviation estimated value that is a carrier frequency deviation estimated value is calculated for the first polarization input signal, and a second carrier frequency deviation estimated value is calculated for the second polarization input signal. The estimated carrier frequency deviation is calculated. Thereafter, a frequency deviation average value that is an average of the first carrier frequency deviation estimated value and the second carrier frequency deviation estimated value is calculated.

  As described above, in the carrier frequency deviation estimation apparatus 200 and the carrier frequency deviation estimation method of the present embodiment, the carrier frequency deviation estimation value is obtained using each of the first polarization input signal and the second polarization input signal. The averaged frequency deviation average value is calculated. Thereby, since the influence by noise can be reduced, the accuracy of estimating the carrier frequency deviation can be improved.

  Next, the carrier frequency deviation compensating apparatus 300 according to the present embodiment will be described with reference to FIG.

  The carrier frequency deviation compensating apparatus 300 includes the above-described carrier frequency deviation estimating apparatus 200 and frequency deviation compensating means. The frequency deviation compensation means is configured to output a first polarization input signal (X polarization input signal) and a second polarization input signal (Y polarization input signal) based on the average frequency deviation calculated by the carrier frequency deviation estimation apparatus 200. ) To compensate for the carrier frequency deviation.

  The carrier frequency deviation compensating apparatus 300 will be described in further detail. The frequency deviation compensation means includes a phase compensation amount calculation unit for calculating a phase compensation amount for the input signal based on the average frequency deviation value and a unit sampling time, and a carrier frequency deviation by rotating the phase of the input signal by the phase compensation amount. A phase compensation unit for compensation. The configuration of the frequency deviation compensating means for the X polarization input signal and the Y polarization input signal is the same.

  Specifically, the carrier frequency deviation estimation apparatus 200 uses the one of the two branched X-polarization input signals and Y-polarization input signals of the X-polarization input signal and the Y-polarization input signal. The average value is calculated. The phase compensation amount calculation unit 311 (312) calculates the phase compensation amount based on the average frequency deviation value. The other signal of the X polarization input signal and the Y polarization input signal waits in the delay unit 321 (322) included in the phase compensation unit until the phase compensation amount is calculated. The phase compensation amount is calculated as the sum of products of the frequency deviation average value and the unit sample time. The X polarization input signal (Y polarization input signal) that has been waiting in the delay device 321 (322) is phase rotated clockwise by the calculated phase compensation amount, so that the carrier frequency deviation is compensated. The

  According to the carrier frequency deviation compensating apparatus 300 of the present embodiment described above, the accuracy of estimating the carrier frequency deviation by the carrier frequency deviation estimating apparatus 200 can be improved, so that the frequency deviation can be compensated with high accuracy. Become. Thereby, the transmission characteristic of an optical communication system can be improved.

  The present invention has been described above using the above-described embodiment as an exemplary example. However, the present invention is not limited to the above-described embodiment. That is, the present invention can apply various modes that can be understood by those skilled in the art within the scope of the present invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2013-210085 for which it applied on October 7, 2013, and takes in those the indications of all here.

100, 200 Carrier frequency deviation estimation device 110 Re-sampling means 120 Time variation vector calculation means 130 Filter means 140 Frequency deviation estimation means 141 Deflection angle calculation unit 142 Frequency deviation calculation unit 211 First carrier frequency deviation estimation device 212 Second carrier wave Frequency deviation estimator 220 Frequency deviation averaging means 300 Carrier frequency deviation compensator 311, 312 Phase compensation amount calculator 321, 322 Delay 500 Optical receiver using related digital coherent method 501 Local oscillation light generator 510 90 degree hybrid 521 to 524 Photoelectric conversion unit 531 to 534 AD converter (ADC)
540 Digital signal processing unit 551, 552 Symbol identification unit 611 X-polarization signal generation unit 612 Y-polarization signal generation unit 620, 621, 622 Frequency deviation rough compensation unit 623 Frequency deviation rough estimation unit 624 Phase compensation amount calculation unit 625 delay unit 626 FFT unit 627 Data shift unit 628 IFFT unit 631, 632 Waveform distortion compensation unit 640 Polarization separation unit 651, 652 Resampling unit 660, 661, 662 Frequency deviation compensation unit 663 Frequency deviation estimation unit 671, 672 Phase deviation compensation unit

Claims (10)

Resampling means for converting an input signal into an oversampling signal that is oversampled at a multiple of the symbol rate of the input signal;
A time variation vector calculating means for calculating a time variation vector between two temporally continuous sample signals included in the oversampling signal;
Filter means for calculating an average value of the time variation vectors;
The estimation means for calculating a carrier frequency offset estimate based on the average value, have a capital,
The time variation vector calculating means is a carrier frequency deviation estimating device comprising a delay device that delays a sample signal that precedes in time among the two sample signals by one sample time . In the carrier frequency deviation estimation apparatus according to claim 1,
The time variation vector calculating means includes :
A complex conjugate unit for outputting the calculated complex conjugate sample signal by the complex conjugate of a sample signal output from the pre-Symbol delayer,
Subsequent sample signal and further comprising carrier frequency offset estimation apparatus adder, multiplication and calculates the product of the complex conjugate sample signal of the two sample signals. In the carrier frequency deviation estimation apparatus according to claim 1 or 2,
The frequency deviation estimating means includes
A declination calculator for calculating a declination from the average value;
A carrier frequency deviation estimation device comprising: a frequency deviation calculator that calculates the carrier frequency deviation estimate based on the relationship between the declination and the carrier frequency deviation. A first carrier frequency deviation estimation device, a second carrier frequency deviation estimation device, and a frequency deviation averaging means, which are the carrier frequency deviation estimation device according to any one of claims 1 to 3,
Each of the first carrier frequency deviation estimation device and the second carrier frequency deviation estimation device is a polarization multiplexed optical signal obtained by polarization multiplexing two single polarization optical signals that are arranged in the same frequency band and orthogonal to each other. The first polarized wave input signal and the second polarized wave input signal obtained by detecting the signal are used as the input signals, and the first carrier frequency deviation estimated value and the second carrier frequency which are the carrier frequency deviation estimated values are used. Output deviation estimates respectively
The frequency deviation averaging means calculates a frequency deviation average value that is an average of the first carrier frequency deviation estimated value and the second carrier frequency deviation estimated value. A carrier frequency deviation estimating device for calculating a carrier frequency deviation estimated value, and a frequency deviation compensating means for compensating the carrier frequency deviation of the input signal based on the carrier frequency deviation estimated value,
The carrier frequency deviation estimating device is:
Resampling means for converting the input signal into an oversampling signal that is oversampled at a multiple of the symbol rate of the input signal;
A time variation vector calculating means for calculating a time variation vector between two temporally continuous sample signals included in the oversampling signal;
Filter means for calculating an average value of the time variation vectors;
The estimation means for calculating said carrier frequency deviation estimation value based on the average value, with a capital,
The time variation vector calculating means is a carrier frequency deviation compensating device comprising a delay device that delays a sample signal that precedes in time among the two sample signals by one sample time . In the carrier frequency deviation compensating apparatus according to claim 5,
The frequency deviation compensating means is
A phase compensation amount calculation unit for calculating a phase compensation amount for the input signal based on the carrier frequency deviation estimated value and a unit sampling time;
A carrier frequency deviation compensation device comprising: a phase compensation unit that compensates for the carrier frequency deviation by rotating the phase of the input signal by the phase compensation amount. In the carrier frequency deviation compensating apparatus according to claim 5,
The frequency deviation compensating means is
An FFT unit for performing a fast Fourier transform on the input signal;
A data shift unit that shifts the frequency of the fast Fourier transform processed input signal output by the FFT unit by the carrier frequency deviation estimation value;
An IFFT unit that performs an inverse Fourier transform process on an output signal of the data shift unit. In the carrier frequency deviation compensating apparatus according to claim 5 or 6,
A first carrier frequency deviation estimation device, a second carrier frequency deviation estimation device, and a frequency deviation averaging means, which are the carrier frequency deviation estimation devices;
Each of the first carrier frequency deviation estimation device and the second carrier frequency deviation estimation device is a polarization multiplexed optical signal obtained by polarization multiplexing two single polarization optical signals that are arranged in the same frequency band and orthogonal to each other. The first polarized wave input signal and the second polarized wave input signal obtained by detecting the signal are used as the input signals, and the first carrier frequency deviation estimated value and the second carrier frequency which are the carrier frequency deviation estimated values are used. Output deviation estimates respectively
The frequency deviation averaging means calculates a frequency deviation average value that is an average of the first carrier frequency deviation estimated value and the second carrier frequency deviation estimated value;
The frequency deviation compensation means compensates carrier frequency deviations of the first polarization input signal and the second polarization input signal based on the frequency deviation average value. The input signal is converted to an oversampling signal that is oversampled at a multiple of the symbol rate of the input signal,
Calculating a temporal variation vector between two temporally continuous sample signals included in the oversampling signal;
An average value of the time variation vector is calculated by filtering,
Calculate a carrier frequency deviation estimate based on the average value ,
A carrier frequency deviation estimation method for delaying a sample signal preceding in time among the two sample signals by one sample time when calculating the time variation vector . In the carrier frequency deviation estimation method according to claim 9,
A first polarization input signal and a second polarization input signal obtained by detecting a polarization multiplexed optical signal obtained by polarization multiplexing two single polarization optical signals whose center frequencies are arranged in the same frequency band and orthogonal to each other As the input signal,
Calculating a first carrier frequency deviation estimate that is the carrier frequency deviation estimate for the first polarization input signal;
Calculating a second carrier frequency deviation estimate which is the carrier frequency deviation estimate for the second polarization input signal;
A carrier frequency deviation estimation method that calculates a frequency deviation average value that is an average of the first carrier frequency deviation estimation value and the second carrier frequency deviation estimation value.

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