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:
Nov. 28, 2000
Filed:
Jan. 04, 1999
Toshiro Yoshida, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
In an optical wavelength control apparatus for a laser diode, an optical branching circuit branches a laser beam from the laser diode into first, second, and third branched laser beams. An optical band-pass filter and optical low- and high-pass filters receive the first, second, and third branched laser beams and transmit laser beams having specific optical wavelengths therethrough as transmitted beams. First, second, and third photodiodes convert output beams from these filters into electrical signals and output them as analog voltages. A comparison amplifier compares the analog voltages output from the second and third photodiodes and outputs a comparison result signal. An operational amplifier performs differential amplification of a reference analog voltage from the first photodiode and the output signal from the comparison amplifier, and outputs a control signal. A temperature adjustment element is in tight contact with the laser diode and generates heat, a temperature of which is externally controlled. A temperature adjustment circuit controls the temperature of heat from the temperature adjustment element on the basis of the control signal.