A 4×112 Git/s high speed PAM-4 transimpedance amplifier was designed in a 90 nm SiGe BiCMOS IC process. A shunt-feedback input stage was used to realize high bandwidth and low noise performance. A novel double Gilbert cell based variable gain amplifier was creatively proposed to accommodate input current with a wide dynamic range. The emitter degeneration technique was used to boost the bandwidth and improve the linearity of the circuit. The chip measurement results show that the optical receiver front-end can achieve a maximum transimpedance gain of 74 dBΩ, a bandwidth of 32 GHz, an input-referred noise current density of 5.6 pA·Hz-1/2, and a less than 5% total harmonic distortion with up to 3 mA input current. The transimpedance amplifier was further integrated into a 400G QSFP-DD optical module. The measurement results show that the module performance satisfies the sensitivity and transmission distance requirements of IEEE 400G Ethernet FR4 standard.