Compensation coefficient calculation method
In a method in which a compensation coefficient calculating portion ( 6 ) calculates a compensation coefficient of a compensation portion ( 5 ) which compensates transmission characteristics of a signal, a known signal is extracted from the signal. Next, a pseudo-random number is added to the extracted known signal. Next, the compensation coefficient is calculated by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.
1. A compensation coefficient calculation method performed by a receiver receiving and converting an optical signal to a received signal which is an electrical signal, comprising:
receiving the optical signal to which a known signal is added, converting the optical signal into the received signal, and extracting the known signal from the received signal;
adding a pseudo-random number to the extracted known signal; and
calculating a compensation coefficient of compensation circuitry configured to equalize transmission characteristics of the received signal by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.
2. The compensation coefficient calculation method according to claim 1 , wherein the known signal is a long cycle/continuous known pattern,
the compensation circuitry further comprising an FIR filter, and
the calculating the compensation coefficient further comprising calculating a tap coefficient of the FIR filter based on the long cycle/continuous known pattern by using a minimal mean square error method algorithm.
3. The compensation coefficient calculation method according to claim 2 , further comprising:
generating a pseudo-random number; and
standardizing a magnitude of the pseudo-random number so that a ratio between average power of the known signal of the signal and average power of the pseudo-random number becomes a predetermined value,
wherein the standardized pseudo-random number is added to the known signal in the adding the pseudo-random number to the extracted known signal.
4. The compensation coefficient calculation method according to claim 2 , wherein the pseudo-random number has Gaussian distribution.
5. The compensation coefficient calculation method according to claim 2 , wherein the compensation circuitry is configured to comprise a butterfly type filter, and
the compensation coefficient is a tap coefficient of the butterfly type filter.
6. A compensation coefficient calculation method performed by a transmitter converting a transmission signal which is an electrical signal to an optical signal and transmitting the optical signal, comprising:
extracting a known signal from an output signal of compensation circuitry configured to equalize transmission characteristics of the transmission signal to which the known signal is added;
adding a pseudo-random number to the extracted known signal; and
calculating a compensation coefficient of the compensation circuitry by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.
7. The compensation coefficient calculation method according to claim 6 , wherein the known signal is a long cycle/continuous known pattern,
the compensation circuitry further comprising an FIR filter, and
the calculating the compensation coefficient further comprising calculating a tap coefficient of the FIR filter based on the long cycle/continuous known pattern by using a minimal mean square error method algorithm.
8. The compensation coefficient calculation method according to claim 7 , further comprising:
generating a pseudo-random number; and
standardizing a magnitude of the pseudo-random number so that a ratio between average power of the known signal of the signal and average power of the pseudo-random number becomes a predetermined value,
wherein the standardized pseudo-random number is added to the known signal in the adding the pseudo-random number to the extracted known signal.
9. The compensation coefficient calculation method according to claim 7 , wherein the pseudo-random number has Gaussian distribution.
10. The compensation coefficient calculation method according to claim 7 , wherein the compensation portion is configured to comprise a butterfly type filter, and
the compensation coefficient is a tap coefficient of the butterfly type filter.
11. A compensation coefficient calculation method performed by a receiver receiving and converting an optical signal to a received signal which is an electrical signal, comprising:
a step of receiving the optical signal to which a known signal is added, converting the optical signal into the received signal, and extracting the known signal from the received signal;
a pseudo-random number adding step of adding a pseudo-random number to the extracted known signal; and
a coefficient calculating step of calculating a compensation coefficient of a compensation portion configured to equalize transmission characteristics of the received signal by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.