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- Fundamental mode has no nodes and oscillation pattern is half-wavelength. This mode is main mode for single-mode optical fibers. It corresponds to the direct perpendicular angle of light incidence into the cable, so that single ray of light propagates in the center of the core, as most of the energy is concentrated in the center (where is the biggest standing wave amplitude).
- Higher order modes describe behavior of light, when it enters core at an angle (acceptance cone). Standing waves with bigger amount of peaks are considered to be of higher order.