An SOI-based optical arrangement for actively manipulating a lightwave signal propagating along a silicon-insulator-silicon capacitive, SISCAP, waveguide in an SOI-based structure, the SISCAP waveguide including a sub-micron surface silicon layer, SOI, layer of the SOI-based optical arrangement, a relatively thin dielectric layer overlying only a portion of the SOI layer and an upper silicon layer overlying only a portion of a combination of the SOI layer and the relatively thin dielectric layer, the arrangement for actively manipulating a lightwave signal comprising: at least one doped area formed in a SISCAP waveguide area of the SOI layer, the at least one doped area having a first conductivity type; at least one doped area formed in the upper silicon layer so as to overlap at least a portion of the at least one doped area formed in the SOI layer to create an active optical region, the at least one doped area in the upper silicon layer having a second, opposite conductivity type; and a plurality of separate electrical contact regions each associated with an electrode located at a predetermined distance from the active optical region in order to reduce optical loss and each separate electrical contact region in contact with a respective one of the doped areas, wherein the at least one doped area formed in the SISCAP waveguide area of the SOI layer and the at least one doped area formed in the upper silicon layer are processed to form complementary doped regions of a corresponding desired shape in proximity to the relatively thin dielectric layer leaving undoped areas in the SOI layer and the upper silicon layer in the active optical region so as to form the active optical region, the desired shape tailored in the direction of the waveguide such that a specific optical transfer function is achieved within the lightwave signal along the waveguide, wherein upon the application of a voltage to one or more of the separate electrical contact regions, the refractive indexes of the complementary doped regions will be modified to create regions for manipulating the properties of the propagating lightwave signal in a desired manner depending on the shapes of the doped regions. at least one doped area formed in a SISCAP waveguide area of the SOI layer, the at least one doped area having a first conductivity type; at least one doped area formed in the upper silicon layer so as to overlap at least a portion of the at least one doped area formed in the SOI layer to create an active optical region, the at least one doped area in the upper silicon layer having a second, opposite conductivity type; and a plurality of separate electrical contact regions each associated with an electrode located at a predetermined distance from the active optical region in order to reduce optical loss and each separate electrical contact region in contact with a respective one of the doped areas, wherein the at least one doped area formed in the SISCAP waveguide area of the SOI layer and the at least one doped area formed in the upper silicon layer are processed to form complementary doped regions of a corresponding desired shape in proximity to the relatively thin dielectric layer leaving undoped areas in the SOI layer and the upper silicon layer in the active optical region so as to form the active optical region, the desired shape tailored in the direction of the waveguide such that a specific optical transfer function is achieved within the lightwave signal along the waveguide, wherein upon the application of a voltage to one or more of the separate electrical contact regions, the refractive indexes of the complementary doped regions will be modified to create regions for manipulating the properties of the propagating lightwave signal in a desired manner depending on the shapes of the doped regions.