Receiving apparatus and receiving method

A receiving apparatus comprising:

• a receiver that receives signal light frequency-modulated by a signal obtained by adding a main signal and a signal obtained by superimposing a subcarrier on a control signal having a lower frequency than the main signal, and converts the signal light into an analog electric signal;
• and
• a processor that acquires a code sequence corresponding to the control signal on the basis of the analog electric signal,
• wherein the processor is configured to execute instructions to
• acquire a frequency offset amount of the signal light acquired on the basis of the analog electric signal,
• remove a signal other than a signal of a frequency band of the control signal from the frequency offset amount, and
• down-convert the signal of the frequency band of the control signal that is extracted by removal,
• derive a statistical value of the signal of the frequency band of the control signal that is down-converted to the baseband, and
• determine the code sequence corresponding to the control signal on the basis of the derived statistical value and the signal of the frequency band of the control signal that is down-converted to the baseband.

A receiving method executed by a receiving apparatus, the receiving method comprising:

• receiving signal light frequency-modulated by a signal obtained by adding a main signal and a control signal having a lower frequency than the main signal, and converting the signal light into an analog electric signal;
• acquiring a frequency offset amount of the signal light acquired on the basis of the analog electric signal;
• removing a high-frequency component of the frequency offset amount,
• extracting a symbol corresponding to the control signal, by down-sampling on the basis of the frequency offset amount from which the high-frequency component has been removed;
• deriving a statistical value of the frequency offset amount from which the high-frequency component has been removed;
• and
• determining a code sequence corresponding to the control signal on the basis of the extracted symbol and the derived statistical value.