Abstract: A waveguide PIN photodiode is provided. The waveguide PIN photodiode includes a lower light guide layer, a light absorption layer, an upper light guide layer, and a cladding layer. The lower light guide is formed on a substrate, and the light absorption layer is formed on the lower light guide layer. The upper light guide layer is formed on the light absorption layer, and the cladding layer is formed on the upper light guide layer. The lower light guide layer, the light absorption layer, and the upper light guide layer constitute a core layer, which is an optical waveguide, and graded index distribution is symmetrically formed in a depth direction, centering around the light absorption layer having a highest refractive index.

Abstract: A tunable semiconductor laser including a Fabry-Perot filter and an electrode array is disclosed. The propagation direction of the light beam in the cavity can be consecutively shifted applying electric field or current to the electrode and tuning can consecutively performed over the wide wavelength band by the consecutive shift of the angle of the intra cavity laser beam.

Abstract: A channel switching function is added to a wavelength division multiplexing passive optical network (WDM-PON) system, which is an access optical network system, and the potential transmission rate is increased by combining wide wavelength tunable lasers and a time division multiplexing (TDM) data structure and properly using the necessary optical components. In addition, when the wavelength of a light source or an arrayed waveguide grating (AWG) changes, the wavelength is traced and the magnitude of a transmitted signal is maximized without an additional detour line using a loop-back network structure. Furthermore, fewer thermo-electric controllers (TECs) are required for stabilizing the temperature of an optical line terminal (OLT) using wavelength tunable lasers, each laser electrically changing its wavelength.