Optical signal reception apparatus, optical communication system, and method of generating compensation signal of optical signal reception apparatus
A frequency difference compensation unit ( 510 ) generates a carrier recovery signal by compensating for a frequency difference between a local light beam and an optical signal in a plurality of digital signals. A first symbol determination unit ( 521 ) determines the symbol position of the carrier recovery signal in which a frequency difference is compensated for, in accordance with the signal arrangement of multi-value modulation. A second symbol determination unit ( 522 ) determines the symbol position of the carrier recovery signal in which a frequency difference is compensated for, in accordance with a signal arrangement in which the number of multi-values of the multi-value modulation is reduced. A loop filter unit ( 540 ) and a compensation signal generation unit ( 550 ) temporarily generates a compensation signal using a determination result of the second symbol determination unit ( 522 ), and then regularly generates the compensation signal using a determination result of the first symbol determination unit ( 521 ).
1. An optical signal reception apparatus comprising:
an optical front end configured to generate a plurality of output light beams by causing an optical signal on which polarization multiplexing and multi-value modulation are performed and a local light beam to interfere with each other;
a signal conversion unit configured to generate a plurality of digital signals by photoelectrically converting and further analog-digital converting each of the plurality of output light beams;
a frequency difference compensation unit configured to generate a carrier recovery signal by compensating for a frequency difference between the local light beam and the optical signal with respect to the plurality of digital signals;
a first symbol determination unit configured to determine a symbol position of the carrier recovery signal in accordance with a signal arrangement of the multi-value modulation;
a second symbol determination unit configured to determine the symbol position of the carrier recovery signal in accordance with a signal arrangement in which the number of multi-values of the multi-value modulation is reduced; and
a compensation signal generation unit configured to generate a compensation signal in the frequency difference compensation unit,
wherein the compensation signal generation unit is configured to temporarily generate the compensation signal using a determination result of the second symbol determination unit, and then to regularly generate the compensation signal using a determination result of the first symbol determination unit, and
wherein the compensation signal generation unit is configured to temporarily generate the compensation signal using a symbol position indicated by the determination result of the second symbol determination unit and a differential value of a difference in an angle of deviation on a complex representation of the carrier recovery signal.
2. The optical signal reception apparatus according to claim 1 ,
wherein the signal arrangement of the multi-value modulation is a signal arrangement equal to or more than 16-QAM, and
wherein the signal arrangement in which the number of multi-values of the multi-value modulation is reduced is a signal arrangement of QPSK.
3. The optical signal reception apparatus according to claim 1 ,
wherein the compensation signal generation unit is configured to regularly generate the compensation signal using a symbol position indicated by the determination result of the first symbol determination unit and a difference in an angle of deviation on a complex representation of the carrier recovery signal.
4. An optical communication system comprising:
an optical signal transmission apparatus configured to transmit an optical signal on which polarization multiplexing and multi-value modulation are performed; and
an optical signal reception apparatus configured to process the optical signal,
wherein the optical signal reception apparatus includes:
an optical front end configured to generate a plurality of output light beams by causing the optical signal and a local light beam to interfere with each other;
a signal conversion unit configured to generate a plurality of digital signals by photoelectrically converting and further analog-digital converting each of the plurality of output light beams;
a frequency difference compensation unit configured to generate a carrier recovery signal by compensating for a frequency difference between the local light beam and the optical signal with respect to the plurality of digital signals;
a first symbol determination unit configured to determine a symbol position of the carrier recovery signal in accordance with a signal arrangement of the multi-value modulation;
a second symbol determination unit configured to determine the symbol position of the carrier recovery signal in accordance with a signal arrangement in which the number of multi-values of the multi-value modulation is reduced; and
a compensation signal generation unit configured to generate a compensation signal in the frequency difference compensation unit,
wherein the compensation signal generation unit is configured to temporarily generate the compensation signal using a determination result of the second symbol determination unit, and then to regularly generate the compensation signal using a determination result of the first symbol determination unit, and
wherein the compensation signal generation unit is configured to temporarily generate the compensation signal using a symbol position indicated by the determination result of the second symbol determination unit and a differential value of a difference in an angle of deviation on a complex representation of the carrier recovery signal.
5. The optical communication system according to claim 4 ,
wherein the signal arrangement of the multi-value modulation is a signal arrangement equal to or more than 16-QAM, and
wherein the signal arrangement in which the number of multi-values of the multi-value modulation is reduced is a signal arrangement of QPSK.
6. The optical communication system according to claim 4 ,
wherein the compensation signal generation unit is configured to regularly generate the compensation signal using a symbol position indicated by the determination result of the first symbol determination unit and a difference in an angle of deviation on a complex representation of the carrier recovery signal.
7. A method of generating a compensation signal of an optical signal reception apparatus in a frequency difference compensation unit, the optical signal reception apparatus including an optical front end, a signal conversion unit, a frequency, difference compensation unit, a first symbol determination unit, a second symbol determination unit and a compensation signal generation unit, wherein the method comprises:
generating, by the optical front end, a plurality of output light beams by causing an optical signal on which polarization multiplexing and multi-value modulation are performed and a local light beam to interfere with each other;
generating, by the signal conversion unit, a plurality of digital signals by photoelectrically converting and further analog-digital converting each of the plurality of output light beams;
generating, by the frequency difference compensation unit, a carrier recovery signal by compensating for a frequency difference between the local light beam and the optical signal with respect to the plurality of digital signals;
determining, by the first symbol determination unit a symbol position of the carrier recovery signal in accordance with a signal arrangement of the multi-value modulation;
determining, by the second symbol determination unit, the symbol position of the carrier recovery signal in accordance with a signal arrangement in which the number of multi-values of the multi-value modulation is reduced;
temporarily generating, by the compensation signal generation unit, the compensation signal using a determination result of the second symbol determination unit, and then regularly generating the compensation signal using a determination result of the first symbol determination unit; and
temporarily generating, by the compensation signal generation unit, the compensation signal using a symbol position indicated by the determination result of the second symbol determination unit and a differential value of a difference in an angle of deviation on a complex representation of the carrier recovery signal.
8. The method according to claim 7 ,
wherein the signal arrangement of the multi-value modulation is a signal arrangement equal to or more than 16-QAM, and
wherein the signal arrangement in which the number of multi-values of the multi-value modulation is reduced is a signal arrangement of QPSK.
9. The method of claim 7 , wherein the method further comprises regularly generating, by the compensation signal generation unit, the compensation signal using a symbol position indicated by the determination result of the first symbol determination unit and a difference in an angle of deviation on a complex representation of the carrier recovery signal.