By constantly finding ways to reduce signal attenuation, distortion, and susceptibility to external interference, copper PCB traces and cables have ruled the world of high-speed data transmission. These have long been expected to be replaced by fiber optics, and advanced signal conditioning, multi-level modulation, and error correction techniques have allowed engineers to design twinaxial copper cables that operate at 112 Gb/s, far beyond what was expected just a few years ago.

Each technology has its limitations, and high-speed copper channels may be approaching those dictated by the laws of physics. As the need for increased bandwidth continues to grow, fading reduces the effective length of the channel, also known as the reachable distance. In addition to extremely low attenuation, fiber optic links offer higher bandwidth capacity, making fiber an attractive alternative.

For many years, long-distance telecommunications lines have taken advantage of the reach of fiber optic cables. The cost and power consumption of the required electro-optical conversion process has become a major obstacle to the industry-wide adoption of external and especially internal fiber optic interconnects. Advances in silicon photonics and the performance characteristics of optical fibers are changing this equation.