Quantum Encryption Communication Over a 192-km 2.5-Gbit/s Line With Optical Transceivers Employing Yuen-2000 Protocol Based on Intensity Modulation

New Quantum Cipher Optical Communication: Y-00

“…Synchronization of multi-level selection information is critical at this time between the transmitter and receiver. This information is changed at random in each bit between transmitter and receiver (Figure2) [17,18,[20][21][22].…”

“…But this quantum noise is effective between adjacent multi-value levels but it cannot affect entire signal area. For this reason, Y-00 enhances safety using various methods [5,17,18]. This quantum noise effect diffusion method is called Randomization.…”

“…By driving the optical external modulator using the Y-00 signal generated, the Y-00 encryption signal becomes an optical signal with valid quantum noise effect. [17,18]. …”

“…Optimum adjustment is made for the threshold level and timing by the Automatic Gain Control (AGC) amplifier and the threshold value controller. Furthermore, the decoder establishes bit synchronization and key synchronization for encryption of Y-00 [17,18]. …”

“…The measured latency value of the transmission system was 1.29 ms in total including the delay of fiber length. Furthermore, we made WDM transmission experiment multiplexing optical output signals from two opposed Y-00 units and verified error-free transmission at each wavelength [17,18,21]. …”