Abstract: A polarization mode dispersion (PMD) compensator for compensation of PMD in polarization bit interleaved (PBI) optical signals is disclosed. The control uses spectral analysis of components of the electrical output, particularly analysis of a spectral component having a frequency corresponding to the bit frequency of the two bit streams which form the bit interleaved signal. Minimising this spectral component results in alignment of the signal in the system at 45 degrees to the two principal axes. An apparatus for measuring PMD based on spectral analysis is also disclosed.

Abstract: The use of regularly repeated small sections of pattern in making a complete optical grating may generate unwanted effects, such as side lobes, as a result of the regular repetition of defects in the small sections. Methods are described for disrupting the regularity of the occurrence of such defects in a grating made of a plurality of sections, thereby minimizing the likelihood of the occurrence of unwanted side lobes, for example.