An optical waveguide has: a core layer which includes at least one core portion for transmitting a light signal and at least two side cladding portions respectively provided at lateral sides of the core portion so as to be opposed to each other; and two cladding layers respectively provided at vertical sides of the core layer. The present invention especially relates to an agitator, which may be attached to the bottom, wall or cover of a mixing vessel. A first configuration comprising the TZ library and the first TZID version is selected.