Patent ID: 7813886

Claim:
A method of calibrating a frequency monitor having dual etalon signals in quadrature, the method comprising: a) providing calibration data in the form of triples (x i , y i , ν i ) indexed by i, wherein for each triple, x i is a first etalon signal at a known frequency ν i and y i is a second etalon signal at said known frequency ν i , and wherein said first and second etalon signals are substantially in quadrature; b) fitting an ellipse to the set of points (x i , y i ), wherein said ellipse is parametrically defined according to x=x 0 +A cos θ y=y 0 +B sin(θ+ε); c) calculating an angle parameter θ i of said ellipse for each of said points (x i , y i ); d) fitting a line to the set of points (θ i , ν i ) to provide a linear angle-frequency fit, wherein said line is parametrically defined according to ν=sθ+ν 0 ; e) providing said parameters s and ν 0 and said parameters A, B, x 0 , y 0 , and ε as ν(θ) calibration outputs; f) calibrating said frequency monitor having dual etalon signals in quadrature using said ν(θ) calibration outputs.