Studies of future readout links for the CMS experiment

The S-LINK64 extension (Simple Link Interface 64 bit) is a specification introduced by the CMS (Compact Muon Solenoid) experiment that defines a protocol, electrical interface and form factor for a point-to-point, high-speed 64-bit data link. It does not specify the implementation of the physical link. It extends the S-LINK specification developed at CERN. CMS developed an electrical implementation of this link operating at 400 MB/s in order to read out the detector. This paper studies a possible replacement of the existing S-LINK64 implementation by an optical link, based on 10 Gigabit Ethernet. The new link will employ commercial protocols in order to be able to receive the data by standard hardware components like PCs or network switches. Currently prototypes using multiple Gigabit Ethernet links are being developed and tested. The paper summarizes the status of these studies.