High-Speed InP-Based Mach-Zehnder Modulator for Advanced Modulation Formats

We present a traveling-wave-electrode InP-based Mach-Zehnder (MZ) modulator that employs an n-p-i-n waveguide structure. The structure provides low electrical and optical propagation losses, which enables the modulator to operate at a high baud rate with a low driving voltage and a low optical insertion loss. We developed a compact 40-Gb/s differential phase shift keying (DPSK) tunable wavelength transmitter module, which incorporates a full C-band tunable laser and the MZ modulator in one package. The RF driving voltage for the MZ modulator is 3 V_pp in a push-pull drive configuration. Using the same design for the MZ modulator, we also developed a differential quadrature phase shift keying (DQPSK) modulator or optical IQ modulator, and acheived 80-Gb/s DQPSK modulation. Furthermore, we fabricated a compact dual-polarization (DP) QPSK modulator by using the hybrid integration of an InP twin-IQ modulator and a planar lightwave circuit (PLC) polarization multiplexing circuit (PMC). We successfully demonstrated 112-Gbit/s DP-QPSK signal generation.