Abstract: In the wavelength selective fiber optic switch, an optical fiber with a portion of cladding removed defines a window facilitating access to the radially evanescent field present when optical power is propagating through the optical fiber, defining a first transmission path. The cladding removed optical fiber, a secondary optical waveguide, and a grating structure form a grating assisted coupler. An adjustable positioning fixture changes the relative spacing of the fiber core, grating, and output waveguide between a decoupled position and a coupled position. The switch operates, in the decoupled position, to allow optical power to propagate unperturbed through the first transmission path, including optical power at said optical wavelength, and in the coupled position, to extract and reroute optical power at the optical wavelength to propagate through the second transmission path, while leaving unperturbed other wavelengths propagating through the first transmission path.