Z-domain model procedure for heterodyne digital optical phase-locked loop

Abstract

Although there are already some simulation tools modeling and s-domain modeling studied for heterodyne optical phase-locked loop (HOPLL), few studies about z-domain model of OPLL are reported. When the loop filter in HOPLL is implemented by digital circuit, the operation of HOPLL is controlled by digital signals which is called heterodyne digital optical phase-locked loop (HDOPLL) in this paper. It is easily deduced that the performance of HDOPLL can be analyzed more accurately by z-domain model. With a deep analysis, the problem about the nonlinear operation of optical related components can be circumvented, if the optical related components are grouped with phase frequency detector (PFD) during z-domain modeling. So the detail about the z-domain model procedure for HDOPLL is presented in the paper. Then for a case study, stability of HDOPLL is analyzed by an established z-domain model, and the correctness of z-domain model is verified by Simulink behavioral model of HDOPLL.