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:
May. 15, 2007
Filed:
Aug. 07, 2003
Howard Roy Stuart, East Windsor, NJ (US);
Howard Roy Stuart, East Windsor, NJ (US);
Lucent Technologies Inc., Murray Hill, NJ (US);
Abstract
A high-sensitivity signal-to-noise ratio (SNR) determining apparatus measures the in-band SNR of an optical data signal by detecting and demodulating the optical signal and analyzing a narrow bandwidth of the resulting electrical data spectrum at half the data clock frequency, or more generally, a predetermined frequency equal to a multiple M of one-half the clock frequency, f/2, where M is an integer equal to or greater than one, may be used. When the optical signal is a WDM signal, a tunable filter isolates a single channel for detection. The detected electrical signal is subjected to both an in-phase and quadrature narrowband RF demodulation using a local oscillator at precisely half the clock frequency. Using this technique, the magnitude of the data portion of the optical signal becomes the in-phase component and the magnitude of the noise present in the optical signal becomes the quadrature component. The ratio of the two demodulated signal components (in-phase and quadrature) is proportional to the SNR of the detected signal. The technique is inherently narrowband and offers very high sensitivity and does not require an optical pre-amplifier.