Photonic Lightwave Circuits

Integrated-optic waveguide devices become more and more complicated to realize high functionality. Numerical simulations are prerequisite for the design of waveguide devices. Planar lightwave circuits (PLCs) provide various important functionalities for optical wavelength division multiplexing (WDM), time division multiplexing (TOM), code division multiplexing (CDM) systems and fiber-to-the-home (FTTH) access networks. This paper reviews the recent progress and future prospects of waveguide device design and its application to FTTH access networks and photonic signal processing applications.

1. Optical splitters

Single-mode splitters are essential optical components for PDS-PON (passive double star type passive optical network) systems. For greater levels of splitting such as and , the excess loss and PDL of Y-branch splitters increase as more and more Y branches are cascaded. Funnel-type splitter configuration becomes advantageous for large port splitters [1]–[3]. In 1xN funnel splitter, an array of N output waveguides are positioned at the end of the slab region. The output waveguides are positioned so that they all point at the input waveguide. The width of the outer funnel waveguides is designed to be wider than that of the inner one to obtain a uniform coupling efficiency in all output waveguides. The overlap integral of the electric field between the radiated light and the local normal modes of the funnel waveguides gives the splitting ratio. Numerical simulation is required to precisely evaluate the structural parameters, such as the length of the slab, and the width and angle of each funnel waveguide.