  The tRopIcal DEep-sea Neutrino Telescope (TRIDENT) is a future large-scale
next-generation neutrino telescope. In September 2021, the TRIDENT pathfinder
experiment (TRIDENT EXplorer, T-REX for short) completed in-situ measurements
of deep-sea water properties in the South China Sea. The T-REX apparatus
integrates two independent and complementary systems, a photomultiplier tube
(PMT) and a camera system, to measure the optical and radioactive properties of
the deep-sea water. One light emitter module and two light receiver modules
were deployed, which were synchronized by using White Rabbit (WR) technology.
The light emitter module generates nanosecond-width LED pulses, while the light
receiver module hosts three PMTs and a camera to detect photons. The submerged
apparatus and the data acquisition system (DAQ) perform real-time command and
data transmission. We report the design and performance of the readout
electronics for T-REX, including hardware modules, firmware design for digital
signal processing, and host-computer software.
