Riesen, NicholasLove, John2015-12-100018-9197http://hdl.handle.net/1885/64348This paper presents analytical descriptions of the behavior of weakly-guiding/weakly-coupled mode-selective fiber couplers, based on coupled-mode theory. Mode-selective couplers rely on the phase-matching of a higher-order mode in one fiber with the fundamental mode of a second, closely-positioned fiber. Their behavior is shown to be highly-dependent on the principle and azimuthal mode numbers of the higher-order mode, as well as its spatial-orientation. Zero coupling is shown to be possible for an asymmetric higher-order mode even when there is perfect phase-matching. The theory is also numerically simulated, and could assist in the future design of efficient mode-selective couplers for a wide range of optical communications and sensor systems.Keywords: Analytical description; Azimuthal mode number; Coupled-mode theory; Fiber couplers; Fundamental modes; Future designs; Higher-order modes; mode-splitting; Sensor systems; spatial mode-division-multiplexing (MDM); Fibers; Nonlinear optics; Optical communic Coupled-mode theory; mode-selective fiber couplers; mode-splitting; spatial mode-division-multiplexing (MDM)201210.1109/JQE.2012.21962592016-02-24