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:
Apr. 29, 2008
Filed:
Jun. 21, 2006
Daisuke Tanimura, Tokyo, JP;
Daisuke Tanimura, Tokyo, JP;
Yokogawa Electric Corporation, Tokyo, JP;
Abstract
The present invention provides a light transmitter with a stable IQ amplitude ratio relative to the characteristic change of a modulating system. The QPSK light modulator of the present invention includes a laser light source for outputting light; an optical demultiplexer for inputting light and branching it in two directions; two optical phase modulators for inputting respectively one of the branched lights; a π/2 phase shifter provided before or after one of the two optical phase modulators; an encoder for inputting I and Q signals into the optical phase modulators through drivers; and an optical multiplexer for synthesizing the outputs of the two optical phase modulators into a multiplexed, modulated light. The QPSK light modulator includes another optical demultiplexer after the optical multiplexer and a correcting section for correcting amplitude unbalance generated when light passes between the optical demultiplexers, by using output from the second optical demultiplexer.