The present invention relates to a 5-substituted hydantoin racemase, which efficiently catalyzes racemization reactions at a high optimum temperature for racemization reactions, DNA coding for the racemase, and processes for producing optically active amino acids. Said circuit configuration comprises a multitude of digital control loops connected in series and having quantizers. It is advantageous that the fiber coupler can be used in a SDH communication system, and the method also be used to manufacture the all-fiber CWDM multiplexer which covers the E-band wavelengths and the sub-components of the OADM. The multiband antenna also comprises a feeding port comprising a signal terminal.