An Error-Correcting Line Code for a HEP Rad-Hard Multi-GigaBit Optical Link

This paper presents a line encoding scheme designed for the GBT ASIC, a transceiver under development for a multigigabit optical link upgrade of the TTC system. A general overview of issues related to optical links placed in radiation environments is given, and the required properties of the line code discussed. A scheme that preserves the DC-balance of the line and allows forward error correction is proposed. It is implemented through the concatenation of scrambling, a Reed-Solomon error-correction scheme and the addition of an error-tolerant DC-balanced header. The properties of the code are verified for two different interleaving options, which achieve different error correction capability at different implementation costs. One of the two options was implemented in a fully digital ASIC fabricated in a 0.13 μm CMOS technology, and ASIC implementation details and test results are reported.