Performance investigation of PM-based wavelength remodulation scheme in bidirectional TWDM-PON

Signal remodulation mechanism is a promising cost-effective choice for future optical access networks. This paper investigates the scheme of the phase modulator to remodulate upstream data in the bidirectional WDM PON and TWDM PON system. The simulation results of downstream is carried out using two data formats such as RZ and NRZ at varying lengths of single mode fibers in this scheme. In addition, the upstream transmission compares different remodulators such as Phase modulator, Mach–Zehnder modulator (MZM) and Electroabsorption modulator. By analyzing the eye diagram and Q-value, the performance of upstream and downstream transmission is obtained. It is observed that the PM remodulation TWDM-PON with NRZ modulation format has better performance, which is a rational solution for NG-PON2 cost-effectiveness.

Demonstration of biaxially tensile-strained Ge/SiGe multiple quantum well (MQW) electroabsorption modulators with low polarization dependence

We demonstrate a novel biaxially tensile-strained Ge/SiGe multiple quantum well (MQW) electroabsorption modulator with low polarization dependence. The device is waveguide integrated and has a length of 900 μm. Suspended microbridge structure is utilized to introduce biaxial tensile strain to the Ge/Si0.19Ge0.81 MQWs. Light is coupled into and out of the waveguide through deeply etched facets at the ends of the waveguide. Both TE and TM polarized electroabsorption contrast ratios are tested by the use of polarization maintaining focusing lensed fiber and a linear polarizer. A polarization irrelevant contrast ratio of 4.3 dB is achieved under 0 V/2 V operation. Both simulations and experiments indicate that the demonstrated device has potential in waveguide integrated utilizations that have high requirements on polarization uniformity.