Abstract: A reception apparatus includes: a receiving unit configured to coherently detect an optical signal and output an electrical signal containing a modulated signal and a pilot signal; a first compensating unit configured to detect a frequency of the pilot signal by performing a DFT of the electrical signal, and determine and compensate for frequency error in the electrical signal based on a reference frequency; a frequency converting unit configured to convert the frequency of the pilot signal after the compensating such that the frequency of the pilot signal is lowered by the reference frequency; and a second compensating unit configured to determine frequency error in the modulated signal after the compensating by performing a DFT on the pilot signal after the frequency converting and detecting a frequency of the pilot signal after the frequency converting.

Abstract: A reception apparatus includes: a receiving unit configured to coherently detect an optical signal and output an electrical signal containing a modulated signal and a pilot signal; a first compensating unit configured to detect a frequency of the pilot signal by performing a DFT of the electrical signal, and determine and compensate for frequency error in the electrical signal based on a reference frequency; a frequency converting unit configured to convert the frequency of the pilot signal after the compensating such that the frequency of the pilot signal is lowered by the reference frequency; and a second compensating unit configured to determine frequency error in the modulated signal after the compensating by performing a DFT on the pilot signal after the frequency converting and detecting a frequency of the pilot signal after the frequency converting.

Abstract: In this invention, a member generates unique information of an electronic file to be notarized by using a member terminal. Upon identifying the member by signature input, a notary server stores the unique information and the identification information of the member in a database, together with a registration key, in correspondence with each other, and transmits the registration key ID to the member. When a general user wants to check notarization of the electronic file, he/she uses a general user terminal to generate unique information by using the electronic file, and transmits it to the notary server, together with the electronic file and acquired registration key ID. The notary server transmits notary information to the general user if the received unique information coincides with the unique information in the database.