Patent ID: 6657709
Filing Date: 2003-12-02
Classification: G01M,G02B

Abstract:
An apparatus for measuring a polarization-dependent loss, the apparatus comprising:(a) a light source; (b) a polarizer for converting a light irradiated from said light source into a polarized light; (c) a polarization scrambler for modulating polarization state of said polarized light with a frequency F, said polarization scrambler including: (c-1) optical fiber birefringence modulators including at least three cylindrical piezoelectric elements and optical fibers respectively wound around the outer walls of said piezoelectric elements without intermission, and (c-2) AC voltage sources synchronized to a common clock with respect to each of said optical fiber birefringence modulators for applying an AC voltage having a frequency corresponding to the multiple of an integer relatively prime with respect to a predetermined frequency F to said each optical fiber birefringence modulator; (d) a photodetector for, when the output light of the polarization scrambler passes through an object under test, detecting the optical power of the output light undergoes the object; (e) an ADC synchronized to the common clock, for providing an intensity profile of the output light with the period of 1/F; and (f) a digital signal processing unit for averaging the periodic intensity profile of the output light from said ADC to restrain a noise accompanying to each measurement.