Phase difference distribution estimation method and phase difference distribution estimation apparatus

A phase difference distribution estimation method, comprising:

• receiving an optical signal via a space;
• calculating, from the optical signal received in the receiving, a characteristic value related to a characteristic of the space through which the optical signal propagates;
• estimating a phase difference distribution of an optical signal received after a certain period of time, in accordance with the characteristic value calculated in the calculating;
• and
• controlling a phase of the optical signal in the receiving, in accordance with the phase difference distribution estimated in the estimating;
• specifying a first phase difference distribution being a phase difference distribution of the optical signal received at a first timing in the receiving and a second phase difference distribution being a phase difference distribution of the optical signal received at a second timing that is a timing after the first timing in the receiving;
• calculating a cross-correlation value on a displacement amount basis in accordance with the first phase difference distribution and a plurality of comparative distributions obtained by translating the second phase difference distribution in a plane perpendicular to an optical axis while changing the displacement amount;
• and
• calculating a threshold from a statistical value of the cross-correlation values,
• wherein, in the calculating of the characteristic value, the characteristic cross-correlation value that is a characteristic cross-correlation value equal to or more than the threshold and the displacement amount that is a characteristic displacement amount in calculating the characteristic cross-correlation value are calculated as the characteristic value.

A phase difference distribution estimation device, comprising:

• an optical receiver configured to receive an optical signal via a space;
• a processor, a circuitry or a combination thereof configured to:
• calculate a characteristic value indicative of layers of the atmosphere through which the optical signal propagates, from the optical signal received by the optical receiver, the layers of the atmosphere having different movement speeds;
• estimate a phase difference distribution of an optical signal received after a certain period of time, in accordance with the characteristic value;
• and
• control phase modulation of an optical signal by the optical receiver, in accordance with the phase difference distribution.