Patent ID: 6804042
Filing Date: 2004-10-12
Classification: H01S

Abstract:
A method for controlling the frequency and phase of a laser, comprising:sampling an output of the laser; providing the sampled output to first and second modulators; modulating the sampled output with a first frequency in the first modulator; modulating the sampled output with a second frequency in the second modulator; delaying the modulated output from the second modulator; combining the modulated output from the first modulator with the delayed modulated output from the second modulator, to generate a combined output; developing quadrature components based on the combined output; applying an arctangent function to the quadrature components; correlating the output of the arctangent function with a first reference signal to obtain a measure of peak frequency deviation of the laser; correlating the output of the arctangent function with a second reference signal to obtain a measure of phase offset, wherein the second reference signal is 90 degrees out of phase with the first reference signal; integrating the output of the arctangent function to obtain a mean frequency of the laser; comparing the obtained peak frequency deviation and the obtained phase offset, with respective set point values to generate frequency deviation error and phase offset error signals; and adjusting a control signal for modulating the laser, with the frequency deviation error signal, the phase offset error signal, and the obtained mean frequency.