A method and a system provide access to a communications medium that is suitable for allowing use of a plurality of Home Phoneline Network Association v2 frames in a centralized manner. The pixel unit driving circuit is used for driving a light-emitting device to emit light, and comprises a first thin film transistor, a second thin film transistor, a third thin film transistor and a storage capacitor. In particular, the concatenated optical spectrum transmission systems and methods provide a balance between fixed channel systems such as provided for by the International Telecommunication Union and a more flexible system enabled by coherent optical detection. The process can also be substantially automated and anticipatory. The method comprises imprinting a patterned sacrificial layer of etchable material that is positioned on a semiconductor surface that is in turn adjacent a light emitting active region, and thereafter etching the imprinted sacrificial layer and the underlying semiconductor to transfer an imprinted pattern into the semiconductor layer adjacent the light emitting active region. Radii of curvature of the arcuate portion and the first, second and third involute portions are determined so that a stress variation width in a stress state of a so-called partly reverse state caused by tensile stress and compression stress generated in the tooth bottom side area of the tooth before and after the meshing of the tooth can be uniformized.