A silicon Mach–Zehnder modulator (MZM) with quasi-TM mode propagation is investigated for non-return-to-zero on–off keying modulation. The quasi-TM PN phase shifter phase-loss characteristics have been determined and shown to exhibit better performance compared to quasi-TE phase shifter with the same waveguide cross-sectional area and device parameters. The phase shifter modulation efficiency is 1.02 V.cm. The MZM transfer characteristics are determined for the dual-arm push–pull driving scheme, and a traveling-wave electrode structure is employed to enhance the device bandwidth. A 3-dB bandwidth of 74 GHz is obtained at 2.5-V reverse bias. The modulator high-speed characteristics are studied for different data rates over single-mode fiber transmission. A 30-km fiber transmission with an open eye at 160 Gbps with 2-V peak-to-peak drive is obtained with an extinction ratio of 2.3 dB and bit-error-rate (BER) of ∼2.77 × 10 − 06. The effect of fiber dispersion on the BER shows dispersion tolerance from 0 to −1.73 ps . nm − 1 . km − 1 for 30-km fiber transmission below the hard-decision forward error correction threshold at 100-Gbps operation.
The mode, loss, and dispersion characteristics of a buried strip waveguide have been calculated for coarse wavelength division multiplexing wavelengths. Process simulation has been used to form the graded-index core by germanium implantation in silicon. Quasivectorial finite-difference method has been used to calculate the number of propagating modes, effective indices, material absorption, mode confinement, and the dispersion parameters. The scattering loss has been determined from the Payne–Lacey model. The zero dispersion for higher-order modes occurs in the O-band, which is suitable for short-reach multimodal applications. The usable waveguide length and number of modes have been characterized and are limited by the mode with highest propagation loss/dispersion and lowest mode confinement, respectively.
In this paper, a grating assisted MDM-PDM hybrid (de)multiplexer based on the silicon-on-insulator (SOI) platform has been proposed and analyzed using coupled mode theory with effective index method (EIM). The proposed device consists of a multimode wide waveguide and five single mode narrow waveguides. The quasi- TE/TM modes of the wide waveguide are phase matched with the respective contra-propagating fundamental quasi-TE/TM modes of the single mode narrow waveguides. The phase matching conditions are satisfied by using different period gratings, which are surface corrugated on the wide waveguide. The proposed device structure exhibits good crosstalk, insertion loss, and return loss values.
This paper analyzes a germanium-doped silicon traveling wave Mach-Zehnder modulator (TWMZM) for high speed operation at 1550 nm wavelength. Single arm drive modulator performance using non-return-to-zero on-off keying (NRZ-OOK) driving scheme has been investigated. The phase-loss characteristics of the graded-index silicon-germanium PN phase shifter have been determined numerically. The traveling wave electrode has been designed for 1.5 mm long phase shifter. The 3 dB modulation bandwidth of the designed TWMZM is calculated to be 31 GHz at -2 V and an error-free operation of 59 Gbps has been obtained for 2 V peak-to-peak drive voltage with an extinction of ~6 dB.