Digital chaos-masked optical encryption scheme enhanced by two-dimensional key space

- Maximum distance of 10-Gb/s transmission is 80 km without dispersion compensation or inline amplifier.
- The encrypted signal is analog and unrecoverable by post-processing techniques.
- The precise matches of amplitude and phase during decryption provide a large two-dimensional key space.

A digital chaos-masked optical encryption scheme is proposed and demonstrated. The transmitted signal is completely masked by interference chaotic noise in both bandwidth and amplitude with analog method via dual-drive Mach-Zehnder modulator (DDMZM), making the encrypted signal analog, noise-like and unrecoverable by post-processing techniques. The decryption process requires precise matches of both the amplitude and phase between the cancellation and interference chaotic noises, which provide a large two-dimensional key space with the help of optical interference cancellation technology. For 10-Gb/s 16-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal over the maximum transmission distance of 80 km without dispersion compensation or inline amplifier, the tolerable mismatch ranges of amplitude and phase/delay at the forward error correction (FEC) threshold of 3.8×10−3 are 0.44 dB and 0.08 ns respectively.