Abstract: In the disclosed optical signal processing device, the digital-to-analog conversion of the input optical signals is realized in an optical region, without converting the input optical signals into electric signals for the purpose of signal processing, by splitting input optical signals into plural sets, delaying the split optical signals for mutually different delay amounts while adjusting amplitudes of these optical signals, combining these optical signals, and gating these optical signals on a time axis. It is also possible to realize the processing of the optical signals that are multiplexed on a time axis such as interchanges of time-slots similarly.

Abstract: The present invention relates to skis that allows a human subject to walk by sliding of the legs back and forth in a motion similar to cross-country snow skis. In an embodiment, the present invention comprises: (a) two skis having a foot-support for the subject to secure a foot on the upper surface of each ski; (b) flaps secured to the bottom of each ski which allow the skis to frictionally interact with the water such that when the subject pushes back on one of the skis, the subject is propelled forward across the water; and (c) a frame connecting the two skis to each other that allows the skis to slide back and forth with respect to one another in a first direction (x) that is parallel to the length of the skis, and also maintains the skis at a constant distance apart from each other in the (y) direction, and at the same depth in the water in the (z) direction.