Propagation delay time difference measuring method between spatial channels and propagation delay time difference measuring apparatus between spatial channels

摘要

PROBLEM TO BE SOLVED: To provide a method and a device for measuring a difference in propagation delay time between spatial channels, with which the difference in propagation delay time between spatial channels is non-destructively measured at a discretionary distance point in a transmission path.SOLUTION: A method and a device for measuring a difference in propagation delay time between spatial channels according to the present invention include: measuring, for each mode, a spectral shift before and after a temperature/strain change; finding a cross-correlation between a mode-1 spectral shift before the temperature/strain change and a mode-2 spectral shift after the temperature/strain change; and determining delay time with which this cross-correlation is largest as inter-mode delay time between a mode 1 and a mode 2.SELECTED DRAWING: Figure 3