Polarization mode dispersion measuring method and polarization mode dispersion measuring system

A polarization mode dispersion measuring system comprising:

• a light source for emitting a light having substantially uniform spectrum;
• a first polarizer for extracting a linearly polarized beam from the light emitted from the light source;
• a reference object having a predetermined polarization mode dispersion value, for emitting a polarization mode dispersion to the linearly polarized beam incident to one end side and extracted by the first polarizer, and emitting a light from the other end side;
• a polarization plane rotor for rotating a polarization plane of the light emitted from the reference object, and making the light incident to one end side of a measured object;
• a second polarizer for extracting a linearly polarized beam from a light emitted from the other end side of the measured object;
• and
• an optical spectrum analyzer for detecting a spectrum of a light emitted from the second polarizer, wherein
• at least one of a maximum value and a minimum value of a polarization mode dispersion value generated following the rotation of the polarization plane of the light is obtained, from the spectrum of the linearly polarized beam emitted from the other end side at one end side of the measured object detected by the optical spectrum analyzer, and
• the polarization mode dispersion value of the measured object is obtained by using optional two values among the predetermined polarization mode dispersion value, the maximum value of the polarization mode dispersion value, and the minimum value of the polarization mode dispersion value.

A polarization mode dispersion measuring system comprising:

• a light source for emitting a light having substantially uniform spectrum;
• a first polarizer for extracting a linearly polarized beam from the light emitted from the light source;
• a reference object having a predetermined polarization mode dispersion value, for emitting a polarization mode dispersion to the linearly polarized beam incident to one end side and extracted by the first polarizer, and emitting a light from the other end side;
• a polarization plane rotor for rotating a polarization plane of the light emitted from the reference object, and making the light incident to one end side of a measured object;
• a second polarizer for extracting a linearly polarized beam from a light emitted from the other end side of the measured object;
• spectrum detecting means for receiving the light extracted by the second polarizer, automatically analyzing the spectrum of the light, and detecting a wavelength distance between adjacent peaks (or between adjacent bottoms) of the spectrum, a first peak wavelength λ1, and a last peak wavelength λ2;
• and
• PMD calculating means for calculating a PMD value P (a differential group delay time Δτ) by automatically calculating the following expression from values detected by the spectrum detecting means:
• P=k(n−1)·λ1·λ2/(C·Δλ)
• where, k represents a mode coupling coefficient, C represents an optical speed, n represents a number of peaks, and Δλ=λ2−λ1.