US 2003/0111998 A1Published application

Apparatus and method for measuring polarization-dependent loss using repeated high speed polarization scrambling

AssigneeDonam Systems Inc.

InventorsYeon Wan Koh, Bong Wan Lee, Jung Won Kim

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Abstract

Disclosed is an apparatus and method for measuring a changing amount of insertion loss of an optical device depending on a polarization state of an incident light, i.e., a polarization-dependent loss. An incident light that is periodically subject to all polarization states passes through a testing optical device by a polarization scrambler including a piezoelectric element type optical fiber birefringence modulator, and an optical detector measures intensity of the passing light, in which the measured intensity values are averaged for birefringence modulation having a constant period, and then the polarization-dependent loss is computed from a ratio of maximum power to minimum power for the period. Use of the birefringence modulator shortens measuring time, and decreases an affect of external disturbance to the incident light that is incident into the testing optical component or occurrence probability of the external disturbance, so that the polarization-dependent loss can be precisely measured.

Claims6

Dependent claims

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.

6 more elements

Dependencies are inferred from the claim text.