Optical receiving apparatus

1. An optical receiving apparatus comprising:

a receiver that receives an optical signal modulated by a differential phase shift keying and that performs variable dispersion compensation and delay interference processing on the optical signal to demodulate the optical signal;

a setting unit that sets setting values at appropriate values for the variable dispersion compensation and the delay interference processing based on an error condition of the demodulated optical signal; and

a storage unit that stores the setting values set by the setting unit, wherein

the receiver is provided in plurality, and

when a new receiver is additionally provided, the setting unit sets the setting values for the new receiver based on the setting values stored in the storage unit.

2. The optical receiving apparatus according to claim 1 , wherein the receiver includes

a receiving unit that receives the optical signal;

a dispersion compensation unit that performs the dispersion compensation on the optical signal received by the receiving unit with a variable dispersion compensation amount;

a delay interference unit that performs the delay interference processing to cause interference between a branch component that is obtained as a result of the dispersion compensation and that is delayed by one bit, and a branch component that is obtained as a result of a phase control on the optical signal with a variable phase shift amount;

a demodulation unit that demodulates the optical signal that has been subjected to the delay interference processing, by photoelectrically converting into a demodulated electrical signal; and

a monitoring unit that monitors an error condition of the demodulated electrical signal, wherein

the appropriate values indicate an appropriate amount of the variable dispersion compensation and an appropriate amount of the variable phase shift amount.

3. The optical receiving apparatus according to claim 1 , wherein

the storage unit stores the setting values corresponding to each communication path of the receiver, and

when the communication path of the receiver is switched to another communication path, the setting unit sets the setting values based on setting values corresponding to the other communication path among the setting values stored in the storage unit.

4. The optical receiving apparatus according to claim 1 , wherein

the receivers respectively receive the optical signals of different wavelengths, and

the setting unit sets the setting values for the new receiver, based on setting values corresponding to a receiver having a wavelength closest to that of the new receiver, from among the setting values stored in the storage unit.

5. The optical receiving apparatus according to claim 1 , wherein

the receivers respectively receive the optical signals with the different wavelengths, and

the setting unit sets the setting values for the new receiver, based on the setting values stored in the storage unit, a wavelength of the receiver corresponding to the setting values, and a wavelength of the new receiver.

6. The optical receiving apparatus according to claim 1 , further comprising a setting-value receiving unit that receives setting values in a communication path from a communication device at a connection destination of the communication path corresponding to the receiver, wherein

the storage unit stores the setting values received by the setting-value receiving unit, and

when the receiver communicates with the communication device, the setting unit sets the setting values based on the setting values received by the setting-value receiving unit.

7. The optical receiving apparatus according to claim 1 , wherein

the storage unit stores the setting values periodically, and

when a change is made in the setting values with a change rate greater than a predetermined rate, the setting unit sets the setting values of the receiver after a predetermined time elapses from time of the change based on the setting values stored in the storage unit before the change is made.

8. The optical receiving apparatus according to claim 1 , wherein

the storage unit stores the setting values for every predetermined time period, and

the setting unit sets the setting values of the receiver based on setting values corresponding to a current time among the setting values stored in the storage unit.

9. An optical receiving method for an apparatus that includes a plurality of receivers each of which performs variable dispersion compensation and delay interference processing on an optical signal modulated by a differential phase shift keying to demodulate the optical signal, the optical receiving method comprising:

setting values at appropriate values for the variable dispersion compensation and the delay interference processing based on an error condition of the demodulated optical signal; and

storing the values set at the setting; and

setting, when a new receiver is additionally provided, the values for the new receiver based on the values stored at the storing.