Linear and Triangle Order of NX3 Optical Directional Couplers

Abstract Fabrication of single-mode fiber coupler has wide ly expands. However, directional fiber coupler geometry always affects the power propagation either two or three ports. This paper describes power launching by NX3 single mode fiber, examined using a matrix transfer for linear and triangle order, calculated from the eigenvalue and th e eigenvector. This eigenvalue is referred to the coupling coefficient, where it can be expressed as an effective power transmitted to another fiber. The ratio of coupling coefficient between adjacent axial fibers varies, which can be achieved by adjusting separation of fiber and refra ctive index of core and cladding. A calculation has been shown in 3D that both power transmission and phase are affected by not only the geometry order, but also the variation of coupling coefficient, assuming the propagation constants, cross section, and separation of coupling length fiber axis are held constant. This calculation can be applied for any sources of wavelengt h and junction. Keywords : Optical directional coupler, power transfer , coupling coefficient, matrix transfer. 1. Introduction The great utilization of single mode fiber coupler has led to the extensive research and development. The development and fabrication of single-mode fiber coupler has been widely expanding for both tunable filter and optical wave guide switch in telecommunication and device sensor. Optical directional couplers are commonly used for several guided wave devices and for optical switching networks [1]. Directional couplers may refer as devices that used to combine and split optical signals. Significant interaction between three coupled waveguides will occur and thus lead to a significant power exchange between the waveguides [2]. For waveguides that are in parallel condition and propagating with the same phase velocities of guided modes causes the losses and the fraction of power or total power to be transferred from one waveguide to the other waveguides [3]. The power transfer is investigated by constructing a matrix transfer model. Then,