Optical storage has made significant progress since its first introduction as laser videodisc in the late 1970s. Granted, its growth has not been on the explosive 60% per year slope that magnetic storage has enjoyed over the last few years, but then it should not be expected to do so. Removability, backward compatibility and interchangability carry with them a demanding burden, called standards, that must be developed and agreed to by the entire industry. The customers demand this as they do not want a repeat of the VHS/Betamax situation a few years ago. In contrast, the only standard imposed on the magnetic storage industry is the interface; the media and recording technology are captive within the drive, thus permitting tremendous freedom and competition.
Progress has been substantial, however, with CD technology jumping from 680 MB to 4.7 GB with the introduction of DVD. Removable 3.5" magneto-optical (MO) has steadily grown from 128 MB to 640 MB, and 5.25" MO now contains 4.6 GB on a single platter. These advances have come through a combination of laser wavelength reduction, increases in the objective lens numerical aperture, better ISI and cross-talk management, and coding improvements. There is room for even greater advances in storage capacity as we make the transition to blue lasers, near-field optical recording, and multi-layer systems. Increases in storage capacities of 50 to 100 fold are not unreasonable to expect in the next 5 to 10 years.