A data expansion system that provides continuum of discrete wireless small cell coverage areas for mobile terminals includes a set of roadway reflectors configured to provide wireless broadband data services to a mobile terminal. The transmission module is a removable, replaceable, and interchangeable transmission module which can be selected from a plurality of transmission modules having different transmission types, each with a standardized input interface and a standardized output interface. The bobbin includes a wrapping axis extending through the first groove, and a driving portion extending from the wrapping axis. The first line is drawn on a point of the first chromaticity and an origin of axes of the chromaticity space, and the second line is drawn on a point of the second chromaticity and the origin of the axes of the chromaticity space. The optical disk apparatus includes an aberration adding unit that adds complementary aberrations to the first and second lights made incident on the volumetric recording medium, respectively.