A panel unit comprising a window glass panel, and a frame continuously formed on a peripheral edge of the window glass panel by extrusion molding and simultaneously bonded to the peripheral edge of said window glass panel. A hybrid skateboard deck combines at least one layer of bamboo sandwiched between at least two layers of conventional hardwood such as maple. Using this arrangement, the bidirectional adddrop multiplexer is capable of cutting off the relative intensity noise while avoiding the collision of the forward and reverse optical signals.