In this work, we have proposed a new physical layer encryption scheme to improve the
security of optical fiber communication systems. The secrecy scheme is
based on disturbance of the data cluster under the ZUC algorithm
(named for Zu Chongzhi, a famous mathematician in ancient China),
which is generated by optical XOR using a dual-drive Mach–Zehnder
modulator (DD-MZM). A base scrambling pseudo random binary sequence
(PRBS) generated by the ZUC stream cipher is introduced, which results
in a better scrambling effect and randomness in the key stream of the
block encryption structure. A simulation setup conducted in an
encrypted transmission of the 64×64 grayscale image over 80 km of optical
fiber shows that the authorized user can successfully decrypt the
received signal, while the eavesdroppers cannot derive useful
information with a bit error rate (BER) at approximately 0.5. In the
simulation, after setting the delay compensation to 3.125 ps, a
correct signal with a Q-factor as high as 11.3642 and a BER as low as 3.14295−30 can be obtained.