Az úthossz "path length". Lehet a "difference in path length" fordulatot is alkalmazni. Figyeljünk azonban arra, hogy ténylegesen úthosszról, vagy optikai úthosszról van-e szó. Ez utóbbi ugyanis az úthossz szorozva a törésmutatóval (optical path length).

http://en.wikipedia.org/wiki/Interference_(wave_propagation)

http://en.wikipedia.org/wiki/Optical_path_length


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Note added at 8 mins (2010-03-19 10:46:01 GMT)
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"Abstract

Path length difference is the key parameter in two-beam interferometer, especially in low coherence interferometer. It determines the visibility of the interference fringes. In this study, we present a method to determine the path length difference between two arms of a fiber optic Mach–Zehnder interferometer by evaluating the peaks of power distribution of the interference spectrum with a wide band light source. The experimental results are in close agreement with the theoretical calculations."

Determination of path length difference by low coherence interference spectrum

Hui-Kang TengCorresponding Author Contact Information, a, Chia-Nan Changb and Kuo-Chen Langa

a Department of Electrical Engineering, Nan-Kai College, Nan-tou 542, Taiwan, ROC

b Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 100, Taiwan, ROC
Received 1 September 2003;
accepted 1 January 2004.
Available online 18 March 2004.