Electro-optical co-design to minimize power consumption of a 32 GBd optical IQ-transmitter using InP MZ-modulators
This paper addresses the power reduction concepts of an electro-optical transmitter applicable for future small form factor modules such as CFP4. To satisfy the power restrictions of these standards, equations and detailed explanations of the relevant shares of overall power consumption are given. To improve the overall efficiency, an open-collector driver realized in a SiGe technology with f(T) = 190 GHz and f(max) = 200 GHz is proposed for driving an InP-based IQ MZ-modulator. This approach saves 30 % of the driver power and achieves an EVMrms of 8.7 % for a QPSK signal at 32 GBd. A detailed performance comparison to a structurally identical back terminated driver is presented. Further power reduction is demonstrated with a bias tee configuration for a single modulator. DPSK measurements show a very low power consumption of 290 mW at an EVMrms of 7.5 %. The presented bias tee solution simplifies the assembly without performance compromises. All drivers presented in this paper have differential input/output signals and were designed for a non 50 Ohm output impedance to optimize power consumption and performance.