A data processing system may include: a first device; a second device; and an optical link connected between the first and second devices. The optical link may include a main optical waveguide configured to transmit an optical signal output from the second device; N sub-optical waveguides; N mode couplers, each configured to perform a mode coupling operation between the main optical waveguide and a respective one of the N sub-optical waveguides; and an optical wavelength filter connected to an output terminal of the main optical waveguide and an output terminal of each one of the N sub-optical waveguides. Each of the N sub-optical waveguides may include a first region formed at a first distance from the main optical waveguide; a second region formed at a second, greater distance from the main optical waveguide; and a third region for connecting the first and second regions.