(54) ACTIVE CONTROL AND DETECTION OF
TWO NEARLY ORTHOGONAL
POLARIZATIONS IN A FIBER FOR
(75) Inventors: Joanne Y. Law, Sunnyvale, CA (US);
Raymond K. L. Yeung, San Jose, CA
(US); Eric S. Johnstone, Redwood
City, CA (US); Kerry D. Bagwell,
Campbell, CA (US)
(73) Assignee: Agilent Technologies, Inc., Santa Clara, CA (US)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 347 days.
(21) Appl. No.: 11/156,103
(22) Filed: Jun. 17, 2005
(65) Prior Publication Data
US 2006/0285119 Al Dec. 21, 2006
G01B 9/02 (2006.01)
U.S. CI 356/484; 356/491
Field of Classification Search 356/484,
356/486, 487, 493, 491 See application file for complete search history.
U.S. PATENT DOCUMENTS 1,817,206 A * 3/1989 Calvani et al 398/152
A polarization control system includes a light source that generates two light beams with different polarization states and optical frequencies. A polarization state modulator changes the polarization states of the two light beams. A first detector path generates a first beat signal from the two light beams passing through a first polarizer. A second detector path generates a second beat signal from the two light beams passing through a second polarizer that is oriented substantially orthogonal to the first polarizer. An amplitude detector generates an amplitude beat signal from the first and the second beat signals. The system then uses the amplitude beat signal to determine how to adjust the polarization state modulator in order to generate the first and the second light beams with the desired polarization states.
22 Claims, 12 Drawing Sheets