Signal-to-noise ratio estimation method, optical transmission apparatus, and optical transmission system

An optical transmission apparatus comprising:

• a signal sequence extractor configured to extract at least one pair of signal sequences from a received signal including transmission data and the at least one pair of signal sequences;
• an inner product calculator configured to calculate an inner product value of the at least one pair of signal sequences extracted by the signal sequence extractor;
• a power calculator configured to calculate reception power of the at least one pair of signal sequences extracted by the signal sequence extractor;
• and
• an SNR calculator configured to calculate an SNR of the at least one pair of signal sequences on a basis of the inner product value calculated by the inner product calculator and the reception power calculated by the power calculator.

An optical transmission system comprising:

• an optical signal transmitter configured to insert at least one pair of signal sequences into transmission data and transmit the transmission data into which the at least one pair of signal sequences is inserted;
• a signal sequence extractor configured to extract the at least one pair of signal sequences from a received signal obtained by receiving the transmitted transmission data;
• an inner product calculator configured to calculate an inner product value of the at least one pair of signal sequences extracted by the signal sequence extractor;
• a power calculator configured to calculate reception power of the at least one pair of signal sequences extracted by the signal sequence extractor;
• and
• an SNR calculator configured to calculate an SNR of the at least one pair of signal sequences on a basis of the inner product value calculated by the inner product calculator and the reception power calculated by the power calculator.