Reduction of Interlayer Crosstalk of Multilayer Optical Disc by Using Phase-Diversity Homodyne Detection

We theoretically and experimentally studied the effects of phase-diversity homodyne detection on the interlayer crosstalk of a multilayer optical disc by comparison with those of conventional intensity detection. From analytical studies, we clarified the differences in interlayer crosstalk of both detections. Interlayer crosstalk consists of two noises, the intensity of the stray light $N_{1}$ and the interference between the signal and stray light $N_{2}$. The noise $N_{1}$, which is dominant between these two, drastically decreases with layer spacing in phase-diversity homodyne detection owing to mismatch in the phase distribution between reference and stray light compared with that in intensity detection. Simulations and experiments on a dual-layer Blu-ray Disc™ having a layer spacing less than 10 μm demonstrated that phase-diversity homodyne detection provided higher tolerance to interlayer crosstalk than the conventional intensity detection.