A scheme for broadband multi-channel chaotic signals generation

We propose and experimentally demonstrate a wideband multi-channel chaotic source using a weak resonator cavity Fabry-Perot laser diode (WRC-FPLD) with self-phase modulated optical feedback (SPMOF), in which, phase modulation is introduced into the external optical feedback loop to improve the bandwidth of the generated multi-channel chaotic signals. The experimental results show that under appropriate optical feedback intensity, WRC-FPLD with SPMOF can generate wideband multi-channel chaotic signals, when the feedback intensity is in the range of -45 dB to -15 dB, the lasing modes in the range of 1530 nm to 1570 nm can be simultaneously driven into chaos state. In addition, the time delay signature (TDS) characteristics of the generated multi-channel chaotic signals are also investigated. To highlight the advantages of the proposed scheme, we also conducted comparative experiments on the conventional optical feedback scheme without phase modulation. Using SPMOF scheme, the obtained bandwidth of multi-channel chaotic signals is improved obviously, the standard bandwidth reaches 11.5 GHz, the TDS of chaotic signal is suppressed to an indistinguishable level. Relative to traditional Fabry-Perot laser diode, WRC-FPLD used in the experiment has a smaller front reflectance, about 1/90 of the rear reflectance, and a longer cavity, so it can excite more lasing modes. The proposed scheme can generate wideband multi-channel chaotic signals with a small mode spacing, which is an ideal light source for the chaotic optical communication system using wavelength division multiplexing technology.