  The Compressed Baryonic Matter (CBM) experiment will investigate the quantum
chromodynamics (QCD) phase diagram at high net baryon densities and moderate
temperatures. CBM Time of Flight (TOF) system is composed of super modules
containing high performance Multi-gap Resistive Plate Chambers (MRPCs). During
the mass production, each super module assembled with MRPCs needs quality
evaluation, which includes time measurement and data readout. Read out
electronics encounter the challenge of reading data from a super module at a
speed of about 6 Gbps. In this paper, a read out method based on Peripheral
Component Interconnect Express (PCIe) over optical fiber is proposed for
CBM-TOF super module quality evaluation. The digitized data from super module
will be concentrated at the front-end electronics, and then be transmitted to a
PCIe switch module (PSM) over optical fiber using PCIe protocol. The PSM is
directly plugged into the motherboard via gold fingers at the backend data
acquisition server. With this readout method, a high-speed transmission rate
can be reached. Furthermore, a PSM can receives data from several super modules
simultaneously, which is important to improve the evaluation efficiency. This
readout method simplifies the architecture of readout electronics and supports
long distance transmission between frontend and backend.
