ABSTRACT
We propose and numerically investigate a chaotic optical coherent secure communication scheme, which supports long-haul secure transmission for signals in advanced modulation formats. A hybrid optical chaos system is designed with coordination of digital and analog signals. The hybrid entropy source provides a broadband analog optical chaos signal, which could serve as the carrier to load quadrature amplitude modulation (QAM) data. Simultaneously, a digital binary signal generated from the entropy source is transmitted to establish long-haul chaotic synchronization. Coherent detection is utilized at the receiver, and a digital signal processing (DSP) algorithm is adopted to reduce transmission distortion. A 5 Gbaud 16QAM signal is encrypted by a phase chaos carrier with the effective bandwidth of 5.8 GHz. A bit error rate (BER) below forward error correction (FEC) can be achieved after transmitting over 1600 km based on digital-signal-induced chaos synchronization technology. Optimal launch power is investigated to minimize nonlinear effects of transmission links. System security is guaranteed by the high dynamical complexity of the chaotic source and the sensitive time delay as the secret key.
ABSTRACT
Bistatic radar with the separate transmitter and receiver has some attractive merits, thus obtaining many attentions. However, in a traditional bistatic radar system, there are still many problems that hinder it from practical applications. Here we introduce a bistatic radar scheme using a well-designed optical chaos system, from which the analog chaos signal could be determined by generated random binary sequence. The broad bandwidth analog signal is used as surveillance signal and the digital signal are transmitted to the receiver by optical fibers. Finally, high spatial and velocity resolutions of radar system could be obtained by using the analog chaos signal. A high-quality regeneration of the reference signal at different locations can be established by transmitting the digital sequence. Moreover, the mutual interferences could be concealed since the analog surveillance signal and the transmitted digital sequence are delivered by different paths. These could be advantageous for radar applications.
