| 摘要 |
PROBLEM TO BE SOLVED: To provide the optical transmitter and the optical receiver that are configured so that communication of a file with high security is performed with a specific communication device of the user only at a minimum cost increase and a minimum device component increase and communication of the file is not performed with a general device of other parties in compliance with the standards while employing the communication device in compliance with the prescribed standards. SOLUTION: Additional data are prepared in addition to conventional transmission data to allow an opposite party to transmit a secret file, the additional data apply amplitude modulation to an optical signal and the modulated signal is sent to the opposite party with a transmission request. Two kinds of encoders 12, 13 are used for this purpose. The opposite party receiving the transmission request demodulates the additional data that are amplitude-modulated to decode the data and transmits the secret file (hidden file) only when the opposite party can decode the data regularly. A flag to identify the hidden file from a conventional data file is provided for each file and upon the receipt of the transmission request, the opposite party demodulates the additional data to read the flag and transmits the hidden file only when the opposite party can read the additional data regularly. |
