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:
Dec. 07, 2004
Filed:
Sep. 03, 2002
Barry John Vaughan, Ipswich, GB;
Keith Everett, Bury St Edmunds, GB;
Charles Graeme Ritchie, Ipswich, GB;
Agilent Technologies Inc., Palo Alto, CA (US);
Abstract
In an optical communications system, it is necessary to control the extinction ratio of a laser device ( ) of an optical transmission unit. The laser device ( ) is typically used to transmit a signal that can be approximated by a pseudo-random bit stream. The bit stream is monitored by collecting light from a back facet of the laser device ( ) using a photodiode ( ) in a control loop. Due to band limiting effects of the photodiode ( ) and parasitic circuit track capacitances, a feedback signal generated by the photodiode ( ) becomes distorted, leading to difficulties in controlling the extinction ratio. The present invention therefore provides an apparatus that simulates a signal generated by the photodiode ( ) and subsequent processing of the photodiode signal. The simulated signal and the processed photodiode signal are compared so as to generate a control signal for controlling modulation amplitude of the laser device ( ) and hence the extinction ratio.