Biasing method for InP Mach-Zehnder modulators directly coupled to RF driver circuits

An optical transmitter comprises a Mach-Zehnder interferometer directly coupled to driver circuit. The MZ interferometer comprises a pair of differentially driven MZ electrodes to impart RF signals tolight travelling through respective arms of the interferometer and to receive DC bias as a positive voltage via lower n-type cladding of the MZ interferometer. The lower n-type cladding is at a different positive DC potential to an upper plane RF ground of the MZ interferometer, but the lower n-type cladding and the upper plane RF ground have similar AC potential. The MZ interferometer also comprises a pair of resistors in series, to provide differential RF termination of the MZ electrodes, and a capacitive coupling between a virtual ground formed at a centre-point between the pair of resistors and an RF ground to provide common-mode RF termination. The DC supply for the driver circuit is applied to the centre-point of the RF termination. 一种光发射机包括直接耦合的MZ干涉仪和驱动器电路。所述MZ干涉仪包括差分驱动的MZ电极对，被配置为将RF信号赋予通过干涉仪的相应臂行进的光，并且经由所