Latest developments: DWDM - revolution in optical communication promisses 100-fold transmission rate jump of fiber-optical cannels. Expected exponential growth of Internet facility and traffic, Fiber-To-The-Home (FTTH) national programs will demand enormous bandwidth. Paper discusses: Optical Integrated Circuits on SiO₂: Ge (SiON)/Si- structures (SiOIC) - the base element of Dense Wavelength Devision Multiplexer and spectral optical channel switch devices; the specificity of SiOIC's manufacturing, thick-layer PECVD and deep-trench RIE technological processes; and micromechanical technique of the fiber-planar optical wavequide connection. Other important topics: passive DWDM SiOIC's; functional principles of the planar optical DWDM and the volume analog; the Array Waveguide Grating (AWG) as a synthesis of the Michelson's Echelon and the Phased Antenna Array (PHASAR), and spectral selective Add-Drop SiOIC; DWDM optical switches; Waveguide thermooptical modulator and Mach-Zehnder 2x2 switch element; Controlled Add-drop and wavelength selective switch circuits examples; Challenge and prospect of optical switch on SiOIC's; fast optical switches on Silicon-on-Isolator (SOI) structures; and charge-controlled electrooptical modulators on plasma dispersion effect in Si-core waveguides.