Self-phase modulation based chirp generator

The paper discusses design and investigation of a new approach to chirp generation for the aim of frequency deviation increasing. The structure of device that implements chirp generation based on self-phase modulation in optical fibers is given. Self-phase modulation is an effect of nonlinear optics that causes spectrum broadening of a high-power light impulse during its propagation over the optical fiber. In some cases, the optical pulse transforms into a chirp what can be used in radio signal processing. Analytical expressions to assess the main parameters of the result signals are verified by computer simulation. The technique allows achieving chirps with pulse width over 50 ps and frequency deviation up to 20-30 GHz according to the type of a photodiode. The dependence of the chirp frequency deviation on parameters of optical fiber - fiber losses, optical fiber length and others - is also analyzed.