Patent ID: 6870998
Filing Date: 2005-03-22
Classification: G02B,G02F

Abstract:
1. A variable optical attenuator comprising: a substrate; a polymeric waveguide having a core surrounded by a cladding, the waveguide being supported on the substrate; at least two refractive index varying means disposed in-line and spaced apart on an external surface of the waveguide along a propagation direction of an optical signal passing through the waveguide for generating a substantially localized refractive index gradient; and a controller for controlling the refractive index varying means for providing a predetermined attenuation to the optical signal; such that the optical signal propagating through the waveguide passes through a plurality of substantially localized varying refractive index regions for generating a transition loss to attenuate the optical signal by causing a shift of a mode field of the optical signal; wherein the refractive index varying means are temperature varying means for generating a substantially localized temperature gradient to produce the substantially localized refractive index gradient; and wherein the temperature varying means comprises laterally tapered temperature varying means extending across the waveguide for changing the mode field of the optical signal in a lateral and transverse direction to the propagation direction of the waveguide to reduce a polarization dependent loss.