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US 5,371,597 AGranted
System and method for measuring polarization dependent loss
AssigneeAT&T Corp.
InventorsDavid L. Favin, Bruce M. Nyman, Gregory M. Wolter
Life of this patent
Estimating the term…
Abstract
Polarization dependent loss (PDL) of an optical component is computed in a deterministic method that requires only four measurements, each having a unique input state of polarization.
Claims15
A method for computing polarization dependent loss of an optical component, the method comprising the steps of:
- (a) generating an optical input signal;
- (b) polarizing said input signal to produce a polarized signal having a first known polarization state;
- (c) transmitting said polarized signal through said optical component to yield an output signal, wherein a transmissivity of the optical component is represented by a Mueller matrix, an intensity T.sub.O,a of said output signal being a product of first row elements m.sub.O0, m.sub.O1, m.sub.O2, and m.sub.O3 of said Mueller matrix and a Stokes vector representing said polarized signal;
- (d) measuring said intensity T.sub.O,a of said output signal;
- (e) repeating steps (b)-(d) for second, third and fourth polarization states to yield respective intensities T.sub.O,b, T.sub.O,c and T.sub.O,d, wherein each of said first, second, third and fourth polarization states are unique and one of said polarization states is not linear;
- (f) computing values for said first row elements m.sub.O0, m.sub.O1, m.sub.O2, and m.sub.O3 of said Mueller matrix using said intensities T.sub.O,a, T.sub.O,b, T.sub.O,c and T.sub.O,d, and
- (g) computing the polarization dependent loss (PDL) of the optical component from said first row elements m.sub.O0, m.sub.O1, m.sub.O2, and m.sub.O3 of said Mueller matrix.
4 more elements
A method for computing polarization dependent loss of an optical component using a test set, the method comprising the steps of:
- (a) generating an optical input signal;
- (b) polarizing said optical input signal to produce a polarized signal having a first known polarization state;
- (c) tapping off a portion of said polarized signal to produce a test signal and a reference signal;
- (d) measuring an intensity of each of said test signal and said reference signal for said first known polarization state with a power meter;
- (e) repeating steps (b)-(d) for second, third and fourth polarization states, wherein each of said first, second, third and fourth polarization states are unique and one of said polarization states is not linear;
- (f) introducing the optical component into the test set so that said test signal is passed through the optical component prior to step (d);
- (g) repeating steps (a)-(e);
- (h) using, for said first polarization state, said intensity of said reference signal and said test signal measured prior to step (f), and said reference signal measured after step (f), to normalize said intensity of said test signal measured after step (f), said normalized intensity T.sub.O,a representing an intensity loss at said first polarization state resulting from said optical component;
- (i) repeating step (h) for second, third and fourth polarization states to yield respective normalized intensities T.sub.O,b, T.sub.O,c and T.sub.O,d,
- (j) computing values for first row elements m.sub.O0, m.sub.O1, m.sub.O2, and m.sub.O3 of a Mueller matrix from said normalized intensities T.sub.O,a, T.sub.O,b, T.sub.O,c and T.sub.O,d, and
- (k) computing the polarization dependent loss (PDL) of the optical component from said first row elements m.sub.O0, m.sub.O1, m.sub.O2, and m.sub.O3 of said Mueller matrix.
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An apparatus for measuring polarization dependent loss of an optical component, comprising:
- laser means for generating an optical signal;
- polarization means for receiving said optical signal and for producing a polarized signal having one of four known polarization states, wherein each of said polarization states is unique and one of said polarization states is not linear;
- connection means for providing said polarized signal to the optical component;
- meter means for receiving said polarized signal from the optical component and for determining an intensity of said polarized signal;
- actuation means, coupled to said polarization means, for causing said polarization means to cycle through said four known polarization states;
- and
- controller means, coupled to said meter means, for computing the polarization dependent loss of said optical component based on said measured intensities of said polarized signals for said four known polarization states.
4 more elements
Dependencies are inferred from the claim text.