The VELO optical and power board

The optical and power boards (OPB) are part of the on-detector electronics system for the LHCb Vertex Detector (VELO) and they are used in LHCb upgrade 1 which is installed in the second long LHC shutdown period. The OPBs are assembled printed circuit boards (PCBs) that are located immediately outside of the VELO detector vacuum tank, in custom made mechanical crates. They perform the following main functions: optical-electrical conversion of the high-speed data and control signals that are sent to and from the detector module; DC/DC conversion of the supply voltage that is distributed to the detector module and to the components on the OPB; local slow control of the detector module and the OPB; and monitoring of the temperatures and supplied voltages of on the detector module and the OPB. The OPB operates in an environment with radiation, a magnetic field and limited cooling facilities, which is reflected in the design. This document gives and overview of the VELO electronics system and describes in detail the design of the OPB, providing diagrams to illustrate the functionality and tables to define the connectivity.