Author Affiliations
Shanghai Jiao Tong University, School of Electronic Information and Electrical Engineering, State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai, Chinashow less
Fig. 1. Experimental setup. (a) Chaotic transmitter and (b) the offline pilot-based chaotic coherent fiber transmission system. CW, continuous wave laser; MZM, Mach–Zehnder modulator; OC, optical coupler; DL, optical delay line; VOA, variable optical attenuator; PD, photodiode; EA, electrical amplifier. PM-IQM, polarization multiplexing-in-phase/quadrature modulator; SMF, single-mode fiber; EDFA, erbium-doped fiber amplifier; OSC, oscilloscope; DSP, digital signal processing; and NN, neural network.
Fig. 2. Pilot structure at the transmitter and the DSP module at the receiver. (a) Frame structure of pilot symbols; (b) pilot tone structure of chaotic encrypted carriers; (c) principle of FO compensation by pilot tone; and (d) receiver pilot-based DSP module. CD, chromatic dispersion; CPR, carrier phase recovery; RPE, residual phase estimation; and NN, neural network.
Fig. 3. Equalization algorithm process and constellations of the encrypted and decrypted QPSK signal. (a) Jointly LMS equalization and phase noise compensation by pilot symbols; (b) constellation of decrypted QPSK signals in the back-to-back case; (c) constellation of chaotic encrypted carrier; (d) constellation of decrypted QPSK signal by NN after 800 km fiber transmission.
Fig. 4. Experimental setup and results of real-time pilot-based coherent chaotic fiber transmission system. (a) Experimental setup; (b) pilot tone structure of chaotic encrypted carriers; (c) plot of chaotic time series collected from PD2 and NN synchronization; (d) constellation of decrypted QPSK signals in the back-to-back case; (e) constellation of chaotic encrypted carrier; and (f) constellation of decrypted QPSK signal by NN after 800 km fiber transmission.
Fig. 5. BER performance. BER performance of decrypted QPSK signal after 800-km fiber transmission (a) with the length of and (b) with the pilot rate of .