Generation of a Frequency-Quadrupled Phase-Coded Signal With Large Tunability

A photonic approach for frequency-quadrupled phase-coded signal generation with large tunability is proposed and demonstrated. In the proposed scheme, a dual-parallel Mach-Zehnder modulator is used to generate two second-order optical sidebands, which are made orthogonally polarized in a Sagnac loop incorporating a fiber Bragg grating. Then, a polarization modulator is employed to perform phase coding with high coding rate. A distinct advantage of this approach is the capability to generate a phase-coded signal with a large frequency tuning range, from several megahertz to more than 100 GHz. A proof-of-concept experiment is carried out. The generation of a 2.5-Gb/s phase-coded signal with a frequency tuning from 13 to 30 GHz is experimentally verified.