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. 13, 1999
Filed:
Dec. 04, 1997
NEC Corporation, Tokyo, JP;
Abstract
An optical PLL circuit with high precision that has its simplified configuration. An optical-intensity modulator creates difference frequency information (N.times..DELTA.f) by modulating a received optical signal formed of signal optical pulses of a repetitive frequency (N.times.f0) with a reference signal of a frequency (f0+.DELTA.f) and implementing an AND operation of them. The signal is converted into an electric signal by a photo diode. A band-pass filter extracts only the low frequency component (N.times..DELTA.f). A frequency divider produces a frequency component .DELTA.f by dividing the extracted component by N. A multiplier receives the reference signal and the output signal f of a voltage-controlled oscillator and then creates the difference frequency component ((f0+.DELTA.f)-f). A phase comparator compares the low frequency component .DELTA.f with the difference frequency component ((f0+.DELTA.f)-f) and controls the voltage-controlled oscillator to set the phase difference between them to zero.