500-Gb/s/λ Operation of Ultra-Low Power and Low-Temperature-Dependence InP-Based High-Bandwidth Coherent Driver Modulator

For 64-Gbaud operation and beyond, we developed a power efficient high-bandwidth coherent driver modulator composed of a linear four-channel ultra-low power CMOS driver IC and an InP-based dual-polarization IQ modulator. The CMOS driver was fabricated in 65-nm CMOS technology and showed power dissipation of <1 W owing to the use of an open-drain configuration and a stacked current-mode architecture. Moreover, by optimizing the temperature of the thermoelectric cooler that controls the modulator operating temperature, the coherent driver modulator achieved consumed power of <2.5 W at case temperatures of −5 to 75 °C and <2.8 W under −5 to 85 °C. As far as we know, this is the lowest power dissipation for a coherent driver modulator with an InP modulator chip. In addition, by employing a circuit that suppresses temperature dependence of RF characteristics in the CMOS driver, we achieved the 3-dB electro-optical bandwidth of >44 GHz and the variation of 2.0 GHz under the 25° to 85 °C condition. Furthermore, we obtained good back-to-back bit-error-rate performance in up to dual polarization 80-Gbaud 16-QAM modulation.