Patent ID: 7064815

Claim:
A method to measure a chromatic dispersion in an optical transmission line, the method comprising: generating a test signal light intensity-modulated with a test data; inputting the test signal light to the optical transmission line; extracting first and second optical components from the test signal light output from the optical transmission line, each of the first and second optical components comprising one of the group consisting of a main signal light component of the test signal light, an upper sideband component of the test signal light, and a lower sideband component of the test signal light; measuring a time difference between the first and second optical components; and converting the measured time difference into the chromatic dispersion value, wherein the measuring a time difference between the first and second optical components comprises delaying the second optical component and calculating a correlation between the first optical component and the delayed second optical component while varying a phase difference between the first and second optical components.