Patent ID: 6724786
Filing Date: 2004-04-20
Classification: H04B

Abstract:
An apparatus for attenuating optical signals communicated in an optical network comprising:optical signal generator for generating optical signals, each optical signal having a peaked spectrum function including a center wavelength; an optical filter element for receiving and filtering an optical signal, said optical filter element exhibiting a peaked passband function including a center wavelength; and, a wavelength-locked loop servo-control circuit for enabling real time alignment of said optical signal center wavelength with said peaked passband function of said optical filter element, said optical signal center wavelength capable of being aligned at a wavelength corresponding to maximum overlap with said center wavelength of said peaked passband function of said optical filter for maximum transfer of said output optical signal by said filter element and minimum overlap with said peaked passband function of said optical filter so that said output optical signal may be attenuated in said optical system, said wavelength-locked loop servo-control circuit comprising: a means for applying a dither modulation signal at a dither modulation frequency to said optical signal to generate a dither modulated optical signal through said optical filter element; a means for converting a portion of dither modulated optical signal to into a feedback signal; a means for generating an error signal comprising a vector cross product of said feedback signal and said dither modulated optical signal; and a means responsive to said error signal for adjusting the peak spectrum function of said optical signal according to a desired amount of optical signal attenuation, wherein said center wavelength of said optical signal is adjustable between said maximum overlap and minimum overlap with said center wavelength of said peaked passband function of said optical filter and becomes aligned for maximum overlap with said center wavelength of said peaked passband function of said optical filter when said frequency characteristic of said feedback error signal is two times said dither modulation frequency.