An optical fiber amplifier employing a prism to optimally couple pump energy into the pump core of a dual clad fiber. The meander slot antenna structure includes a substrate, a ground element, a feed conductor and a couple conductor. Alternatively, when the periods of the pits are abnormal, the optical pickup is moved inwardly with sensing the periods of the pits and judges whether the periods are normal or not. Because of the design of the multidescriptive coding used, the more representations are selected to recover the stereo audio signal, the higher the quality of the recovered signal.