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. 02, 2014
Filed:
Sep. 08, 2008
Marco Secondini, Rome, IT;
Fabio Cavaliere, Vecchiano, IT;
Marco Secondini, Rome, IT;
Fabio Cavaliere, Vecchiano, IT;
Telefonaktiebolaget L M Ericsson (publ), Stockholm, SE;
Abstract
A 2-QAM (e.g. 16-QAM) optical modulator comprising cascaded I-Q modulators. The first I-Q modulator applies 2(e.g. 4) QAM to an optical signal, having a constellation diagram with the 2(e.g., 4) constellation points located in quadrant I. The second I-Q modulator subsequently applies a quaternary phase-shift keying (QPSK) modulation scheme to the optical signal, thereby rotating the constellation points of the 2-QAM modulation scheme to quadrants II, III and IV, to produce a 2-QAM modulation constellation diagram. The rotation causes the 2-QAM modulator to inherently apply four quadrant differential encoding to the optical signal. A method of 2-QAM optical modulation is also provided and optical signal transmission apparatus comprising the 2-QAM optical modulator.