Proposal for all-optical format conversion based on a periodically poled lithium niobate loop mirror

We propose and simulate two novel schemes of 40 Gbit/s format conversion from non-return-to-zero to return-to-zero based on cascaded second-harmonic generation and difference-frequency generation in a periodically poled lithium niobate loop mirror. We investigate the conversion performance, including eye diagrams, conversion efficiency, pulse width, Q-factor, extinction ratio, and tunability. The proposed schemes can perform single-to-dual-channel format conversion. In addition, it is found that simultaneous multichannel format conversion as well as tunable multicasting format conversion can potentially be implemented with great flexibility.