Polarization dependent loss measurement in photonic devices

A method of calibrating a device for measuring the polarization dependent loss of an optical device under test, comprising:

• a) generating at least four nominal polarization states of incident light with a multiple state polarization generator;
• b) passing said incident light through a substantially dot-product conserving polarization rotator at a first setting;
• c) measuring a transmission characteristic of said incident light through a standard optical component with a known polarization dependent loss at said first setting of said polarization rotator for each of said polarization states;
• d) repeating step c for a plurality of different settings of said polarization rotator;
• e) for each setting of said polarization rotator, calculating a polarization dependent loss value PDLi based on said measured transmission characteristics and said nominal polarization states;
• f) generating an error function of the form f = ∑ i = 1 K ⁢ ⁢ ( PDL i - PDL standard + δ ) 2
• where PDLstandard represents the polarization dependent loss of said standard optical component, δ represents a perturbation in the polarization dependent loss of said standard component introduced by external connectors, and K represents the number of settings of said polarization controller for which said transmission characteristics are measured;
• and
• g) minimizing said error function by adjusting the values of said nominal polarization states to estimate the actual polarization states produced by said multiple state generator.

A method of determining the polarization dependent loss of an optical device under test, comprising:

• a) generating at least four nominal polarization states of incident light with a multiple state polarization generator;
• b) passing said incident light through a substantially dot-product conserving polarization rotator at a first setting;
• c) measuring a transmission characteristic of said incident light through a standard optical component with a known polarization dependent loss value at said first setting of said polarization rotator for each of said polarization states;
• d) repeating step c for a plurality of different setting of said polarization rotator;
• e) for each set of nominal polarization states, calculating a polarization dependent loss value PDLi measured transmission characteristics and said nominal polarization states;
• f) generating an error function of the form f = ∑ i = 1 K ⁢ ⁢ ( PDL i - PDL standard + δ ) 2
• where PDLstandard represents the polarization dependent loss of said standard optical component, δ represents a perturbation in the polarization dependent loss of said standard component introduced by external connectors, and K represents the number of settings of said polarization controller for which said transmission characteristics are measured;
• g) minimizing said error function by adjusting the values of said nominal polarization states to estimate the actual polarization states;
• h) replacing said standard component by an optical device with an unknown polarization dependent loss;
• i) measuring the transmission characteristic through said optical device using the estimated actual polarization states determined in step g;
• and
• j) calculating the polarization dependent loss for said optical device using at least three of the estimated actual polarization states.

An arrangement for calibrating a polarization dependent loss measuring apparatus including a multiple state polarization generator for generating at least four polarization states of a beam of incident light, comprising:

• a) a light source for generating said beam of incident light;
• b) a dot-product conserving polarization rotator having multiple settings for performing different rotations on said incident light;
• c) a transmission characteristic measuring device for measuring a transmission characteristic of said incident light through said optical device for each of said nominal polarization states at each setting of said polarization rotator;
• and
• d) a processor programmed to calculate a polarization dependent loss value at each setting of said polarization rotator from said measured transmission characteristics and said nominal polarization states, generate an aggregate error value for all said settings of said polarization rotator based on a polarization dependent loss value of a standard component, and minimize said aggregate error value by adjusting the values of said nominal polarization states to estimate the actual polarization states produced by said multiple state polarization generator.