Asymmetrical off-on switches for crosstalk reduction in switching networks

An off-on switching scheme is introduced which blocks a waveguide path in t he passive off-state and transmits the signal in the active on-state. The o perating principle is based on the self-diffraction of a narrow guided beam when it escapes from a waveguide with two-dimensional confinement into a r egion of appropriate length with basically one-dimensional confinement. In particular, a remaining interface of the initial waveguide superimposes ref lection, which in sum results in a very efficient asymmetrical blow out of the guided power. In the active on-state, low-loss waveguiding is sustained when an electrode causes an appropriate refractive index change, e.g., due to the thermo-optical effect. Thus, the signal is received in the output w aveguide, the identical counterpart of the input guide. The switching behav iour is almost binary with minimal wavelength dependence. This makes the de vice useful for switching and modulation in a multi-wavelength optical netw ork. For a realistic polymeric waveguide configuration, simulations indicat e on-off signal ratios of > 30 dB. This satisfies the requirements for cros stalk reduction in switching networks.