The present invention has an object to provide a Mach-Zehnder optical modulator for achieving the reduction of wavelength chirping caused in a modulated light. The system includes a plurality of stacked repeaters, a stack bus linking the repeaters, and a single clock to which the plurality of repeaters is synchronized. The diffuser assembly has an end surface, and also has a plurality of outlet holes in a peripheral wall surface thereof. Therefore, this enables to reduce a processing amount of a JPEG 2000 CODEC. Another embodiment relates to determining the similarity based on at least one of an inner product, a length of the defined posture vector and a length of the detected vector. The second material layer has a transmittance higher than 50% in a wavelength range of 400 to 700 nm.