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SPEEDING UP YOUR BACKPLANE

Designing for High Performance with PSI
by Michael Moore

Start ý A New Approach ý Current Standards ý The Next Generation ý Implementation Using PSI ý SERDES Requirements ý Integrated CDR and Encoding Functionality ý Jitter and Eye Diagrams ý High-Speed Memory ý Backplane Applications ý InfiniBand Applications ý Port-Side Applications ý Software Support ý Advantages of Optical Solutions ý Application Example ý Wrap-Up ý Sources and PDF

ADVANTAGES OF OPTICAL SOLUTIONS

Communication with fiber optics has many advantages over electrical- or wire-based interfaces. Some of the advantages of fiber over copper backplanes are:

• complete electrical isolation
• small media size
• lightweight
• absence of radiated emissions from optical media
• immunity from external electrical influences
• high data carrying capacity

These advantages make fiber optics the media of choice in electrically hostile or sensitive environments. All major issues of electromagnetic compatibility disappear, including radiated emissions, arcing, static discharge, ground loops, ground offsets, stray currents, and others.

The physical attributes of fiber-optic cable make is desirable in applications where safety may be a concern. When cut, optical fibers cannot cause fire or electric shock hazards and cannot cause a short circuit. When used with LEDs or low-power lasers, there is no optical eye hazard. Fiber-optic cable is also much lighter and smaller than copper cable for a given level of bandwidth. Optical fiber is a safe communications media in hostile environments such as underwater, harsh weather, or around explosive gasses.

These properties make serial links using optical fiber the ideal backplane solution in many applications. For example, absolute electrical isolation is required between medical equipment and patients, and fiber allows sensitive equipment to operate without electrical interference. Heavy electrical motors generate significant amounts of interference and ground offsets. Optical fiber is immune to these environmental factors.

Optical fiber also can be used in video, which requires high bandwidth and moderate distance between the camera and recording equipment. New video standards (such as SMPTE-292) specify fiber-optic interfaces. Other areas that benefit from optical fiber include in-flight entertainment, avionics, and general-purpose equipment.

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