Low-temperature-dependence CMOS linear driver with serial peripheral interface for 64-Gbaud ultra-low power coherent optical transmitters

The authors used 65-nm CMOS technology to develop a linear four-channel driver IC with low temperature dependence and ultra-low power dissipation for 64-Gbaud coherent optical transmitters. The driver showed more than a 48-GHz 3-dB electrical bandwidth and less than 1-W power consumption in four-channel operation. By employing a circuit that suppresses the temperature dependence, they achieved 3-dB electrical bandwidth variation of 3.0 GHz and the gain variation of 1.5 dB under the −5 to 75°C and ±5% supply voltage variation conditions. The CMOS driver has all the necessary functions for a high-bandwidth coherent driver modulator such as a gain control, peaking control, peak detection and temperature monitoring, all of which functions can be controlled by a serial peripheral interface. A fabricated sub-assembly consisting of the CMOS driver and an InP modulator showed a 48-GHz 3-dB electro-optic bandwidth.