Silicon photonics enables the manufacturing of high-speed, low-power, integrated optical circuits with compact footprints, and recent studies have also shown it to have a high tolerance to radiation. The technology has, therefore, been identified as an excellent candidate for the development of the next generation of radiation-tolerant optical links for high-energy physics (HEP) experiments at CERN. This article presents the results of the characterization and modeling of building block devices and circuits for custom radiation-tolerant transceivers based on silicon photonics. We demonstrate a four-channel wavelength division multiplexing (WDM) transmitter (Tx) based on microring modulators (RMs) operating at 25 Gb/s per lane, and a polarization-insensitive receiver (Rx) based on germanium photodiodes (PD). Solutions for the thermal tuning of the RMs and on- chip active polarization control are also reported.