METHOD FOR MEASURING CUT-OFF WAVELENGTH OF OPTICAL FIBER

摘要

PURPOSE:To accurately measure the cut-off wavelength of LP11 mode of optical fiber by making said wavelength comparatively easy. CONSTITUTION:The lowest order mode LP01 is propagated within the optical fiber to be measured through continuously changing the wavelength of the light made incident to said fiber. The wavelength lambdaX in which the group delay time lag DELTAtau between the lowest order mode LP01 and the 2nd higher mode LP11 becomes zero is measured. Furthermore, the normalized frequency VX corresponding to the wavelength lambdaX and the cut-off normalized frequency VC corresponding to the cut-off wavelength lambdaC of mode LP11 are obtained by the theoretical calculation. The cut-off wavelength lambdaC of mode LP11 is decided by the equation VX/VC/lambdaC=lambdaX through using the obtained lambdaX, VX and VC.