An improved method and apparatus is provided for transmitting a WDM optical signal. The present invention also allows for treatment of the starting material with the near-critical or supercritical fluid. Identification data is obtained from the data frame at a data link layer to determine whether the data frame is a multicast frame. The wireless communication device also determines a reference subframe n\u2212nreference based on a limit and at least one limiting criterion. Exposure of the oxygen store to rich andor lean exhaust gas is maintained after this threshold value has been crossed to ensure that the oxygen store is indeed sufficiently filled after the oxygen intake storage capacity has been measured, or is sufficiently emptied after the oxygen removal storage capacity has been measured. The scanning provides that the homogenized scanned light beam at the screen has a coherence radius less than the original coherence radius of the beam.