Noise Immunity The question has been raised, "What about noise immunity, a major feature of the fiber optic SERCOS interface?" The answer is that 20 years ago when the SERCOS interface was developed, Industrial Ethernet was also in its infancy. Today's Industrial Ethernet provides adequate noise immunity for most applications, at a lower cost than fiber optics. A fiber-optic implementation of SERCOS III is planned for those high-noise-critical applications that still require it. This area of Industrial Ethernet is still being defined. For example standardized, small-size, low-cost Ethernet connectors, suitable for use in motion control applications, are not yet standardized.