CUTOFF WAVELENGTH MEASURING METHOD FOR SINGLE-MODE OPTICAL WAVEGUIDE

摘要

PURPOSE:To realize the easy, nondestructive cutoff wavelength measuring method for the single-mode optical waveguide by putting one end of an optical fiber in contact with or nearby one end of the single-mode optical waveguide. CONSTITUTION:The white light from a light source 262 is made into monochromatic light 261, which is entered into the optical fiber 23 where the light can be propagated in two modes with the cutoff wavelength of an optical waveguide 21, and a high-order mode removal part 25 which is formed by winding the fiber nearby the incidence end around a column removes the high-order mode and the light in single mode is entered into the optical waveguide 21. Its output is photodetected completely by a multimode optical fiber 24 for photodetection which is put in contact while having its optical axis aligned and while photodetection parts 281-283 measure the output light, the optical axes of the fiber 23 and waveguide 21 are aligned with each other, so that the output light intensity of 0.7-1.7mum in wavelength is measured at prescribed intervals. Consequently, the loss value varies abruptly right below the cutoff wavelength lambdaCW of the waveguide 21 as shown in a figure (a) and the wavelength dependency of variation in the loss value is reduced on a shorter wavelength side than said wavelength. The cutoff wavelength of the waveguide 21 is measured without any destruction.