| 摘要 |
PURPOSE:To eliminate an error caused by the elongation of an optical fiber, by calculating a relative group delay characteristic by passing a reference light signal fixed in a wavelength and a measuring light signal variable in a wavelength through the same optical fiber. CONSTITUTION:Two light signals to be modulated with wavelengths lambdak, lambdac, respectively emitted from a modulation applied variable wavelength light source 2 and a fixed wavelength light source 9 are simultaneously passed through an optical fiber 5 to be measured through a synthesizer 10. The emitted light from the optical fiber 5 is separated by a light splitter 11 and separated lights are respectively converted to electric signals by photoelectric converters 6, 7. Subsequently, by detecting the phase difference of modulated signals contained in two lights to be modulated with wavelengths lambdak, lambdac by a phase comparator 8, various relative group delay times of light with the wavelength of lambdak to light with the reference wavelength lambdac are calculated. Further, a light dispersing characteristic is obtained from these delay times. By this method, a time for measuring one relative delay time is made short and, therefore, an error due to the elongation of a fiber with the change in a temp. can be neglected. |
