The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 08, 2010
Filed:
Nov. 01, 2007
Boris Kershteyn, Marietta, GA (US);
Steven W. Cornelius, Dunwoody, GA (US);
Boris Kershteyn, Marietta, GA (US);
Steven W. Cornelius, Dunwoody, GA (US);
Ciena Corporation, Linthicum, MD (US);
Abstract
DQPSK modulator control is provided using a single monitor photodiode with a selectively injected dither tone. The dither tone signal is sequentially injected into arm modulators and/or to a modulator driver port in time slots. A tapped signal at the output of the modulator is monitored synchronously with injected dither (I arm, Q arm, or phase modulator in third slot). The recovered dither output from a single photodiode is processed in the same sequence as the dither injection to adjust the bias to the optimal point: I-arm at the null point, Q-arm at the null point, and phase modulator at the quadrature point. This technique can be used for any control where the rate of change of the monitored condition due to systemic or environmental conditions (e.g., temperature, aging, etc.) is slow enough to allow time slot dither injection, monitor, and control.