Tachypnea - Distinction from other breathing terms. 1  Different sources produce different classifications for breathing terms. 2  Some describe tachypnea as any rapid breathing. Hyperventilation is then described as increased ventilation of the alveoli (which can occur through increased rate or depth of breathing, or both) where there is a smaller rise in metabolic carbon dioxide relative to this increase in ventilation.
However, guidance is also possible, e.g., by the use of reflections, e.g. at metallic interfaces. Some waveguides also involve plasmonic effects at metals. Figure 1: Two different kinds of waveguides. Planar waveguides guide light only in the vertical direction, whereas channel waveguides guide in two dimensions.
One of the most common, and simplest, waveguide directional couplers is the Bethe-hole directional coupler. This consists of two parallel waveguides, one stacked on top of the other, with a hole between them. Some of the power from one guide is launched through the hole into the other.