OPTICS AND OPTOELECTRONICS VOLUME: 15 | NUMBER: 1 | 2017 | MARCH Comparision of Splitting Properties of Various 1×16 Splitters Catalina BUTSCHER 1, 2 , Dana SEYRINGER 1 , Michal LUCKI 2 1 Research Centre for Microtechnology, Vorarlberg University of Applied Sciences, Hochschulstrasse 1, 6820 Dornbirn, Austria 2 Department of Telecommunication Engineering, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, 16627 Prague 6, Czech Republic catalina.burtscher@fhv.at, dana.seyringer@fhv.at, luckimic@fel.cvut.cz DOI: 10.15598/aeee.v15i1.2014 Abstract. Optical Access Networks (OAN) mostly use optical splitters to distribute the services from Opti- cal Line Terminal (OLT) on the provider’s side to the subscribers in Optical Network Unit (ONU). Optical splitters are the key components in such access net- works as for example GPON and XG-PON by ITU-T. In this paper we investigate the optical properties of 1×16 Y-branch splitter and 1×16 MMI splitters based on different widths of multimode interference section and different lengths of the output ports. These two splitters were designed, simulated and the obtained re- sults of both were studied and compared with each other. Additionally, we show that the used standard waveg- uide core size (usually 6×6 μm 2 to match the diame- ter of the single mode input/output fibers, i.e. to keep the coupling loses as low as possible) supports not only propagation of the single mode but of the first mode too, leading to an asymmetric splitting ratio (increas- ing non-uniformity of split power over all the output waveguides). Decreasing waveguide core size, it is pos- sible to suppress presence of the first mode and this way to reduce non-uniformity. Keywords GPON, MMI splitter, multimode interference splitter, Optical Access Networks (OAN), Op- tical Network Unit (ONU), optical splitting, XG-PON, Y-branch splitter. 1. Introduction Optical splitters play an important role in the inte- grated optics allowing several customers to share the same connection, bringing high-speed networking, digi- tal television and telephone services to residences using fiber-optic cables [1]. There are two main approaches used to split one op- tical signal into N output signals. One of these ap- proaches is to use a MultiMode Interference (MMI) coupler, where the splitting of the optical signal is based on a self-imaging effect [1] and [2]. MMI split- ters feature a large splitting number and a stable split- ting ratio, ensuring good uniformity over all output sig- nals [3]. They exhibit good fabrication tolerance since the splitting is performed in a large multimode section. However, their main disadvantage results from the fact that the length of the MMI section is wavelength- dependent, i.e. MMI splitters are designed solely for one wavelength and can only operate in a narrow wave- length band. They are also polarization-dependent, but it was shown that for strong guidance waveguide structures this dependence is negligible [4]. Another possibility to split an optical signal is to make it as a cascade of one-by-two waveguide branches called Y-branch splitting. Y-branch splitters are the key components in Fiber-To-The-x (FTTx) net- works because they are polarization and wavelength- independent, i.e. one device can be used in the whole operating wavelength window. However, they have the disadvantage that the processing of branching points, where two waveguides start to separate, is technologi- cally very difficult, leading to an asymmetric splitting ratio of the split power over all the output waveguides. Furthermore, Y-branch splitters, especially high chan- nel optical splitters, are much larger in comparison to MMI splitters. In the MMI approach, optical properties of a splitter depend on the width of a multimode coupler. There- fore, in this paper we studied the splitting properties of c  2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 107