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Does single-mode fiber have intermodal dispersion
Single mode fiber, due to its small core diameter, allows light to propagate in only one mode within the fiber. This characteristic results in extremely low intermodal dispersion, making optical signal transmission more stable and maintaining high quality over long distances. The group velocity associated with the fundamental mode is frequency dependent. Intermodal dispersion (also called modal dispersion) is the phenomenon that the group velocity of light propagating in a multimode fiber (or other waveguide) depends not only on the optical frequency (→ chromatic dispersion) but also on the propagation mode involved.
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Peak Measurement of Optical Power Meter
Optical power meters usually display time-averaged power. So for pulse measurements, the signal must be known to calculate the peak power value. However, the instantaneous peak power must be less than the maximum meter reading, or the detector may saturate, resulting in wrong average readings. Also, at low pulse repetition rates, some meters with data or tone detection may produce improper or no readings. A class of "high power" meters has some type of optical attenuating element.