Optical Engineering term...?

Question

What are polarization Crosstalks? What des this term mean? i.e. "Polarization crosstalks are lower than -25dB."

Answer 1

Crosstalk is the ability of a singal in one conductor to distort the signal in an adjacent conductor. The amount of distortion is related to both the amplitude of the signals, the distance between the conductors, and what shileding (if any) is employed on one or both conductors).

Your sentence basically says that the chances of interference in conductor number 2 (caused by the signal in conductor number 1) is pretty small ... and the observed signal degradation is below 25 dB amplitude. ... In case you wer ewondering, a smaller dB number corresponds with a larger distortion. At 1 dB, you're basically cancelling out the signal in conductor 2 entirely.

Answer 2

Electromagnetic waves like light propagate in two linearly independent polarizations. Polarization cross talk is how much power ends up in the unwanted polarization when you excite the other. 25 dB means the unwanted polarization contains one part in 316 the power of the desired power.