Gan Zhou

Integrated Polarization Beam Splitter for 100/400 GE Polarization Multiplexed Coherent Optical Communications

Monolithically integrated polarization management is a key objective for the next generation of high speed optical coherent receivers, and will enable transmission rates up to 400 Gbps. In this work we present a polarization beam splitter (PBS) based on an asymmetrical Mach-Zehnder interferometer (MZI) monolithically integrated with a coherent receiver. Thermal tuning is incorporated on the MZI arms to partially compensate fabrication errors. We propose a complete model that predicts that thermal tuning can furthermore be used to adjust the wavelength response of the PBS. Measurements on a fully integrated receiver validate this model. We show full tunability of the PBS response within the C-band, with a polarization extinction ratio in excess of 16 dB for devices with an estimated width error up to 75 nm.

An ultracompact multimode interference wavelength splitter employing asymmetrical multi-section structures

By using the film mode matching method, a novel design for asymmetrical multi-section 1.55/1.31 μm wavelength splitter based on multimode interference has been proposed and simulated, which can be effectively applied to wavelength multiplexer, self-biased photodiode, and other optical devices. Compared with the conventional wavelength splitter design, the length of the novel structure has been reduced to at least 1/5, showing better performance. The presented structure is also adequate for splitting other wavelengths and more tolerable fabrications.

Modeling of Multiple-Quantum-Well p-i-n Photodiodes

A model for multiple-quantum well (MQW) p-i-n photodiode (PD) is presented. The model accounts for the responsivity spectrum and the polarization-dependent loss. The important physical effects for modeling MQW PDs are the carrier transit time through the MQW layers and the free carrier density in the quantum wells. Furthermore, both effects influence the internal quantum efficiency and saturation of the optical absorption. The model is verified by comparing with the measurement results of a waveguide integrated MQW p-i-n PD. It is suitable for optimizing the design and describing the properties of MQW p-i-n PDs.

Waveguide integrated pin-photodiode array with high power and high linearity

We demonstrate waveguide integrated pin-photodiode arrays (WG-PDAs) by optically parallel connection of different numbers of photodiodes. A responsivity of 0.53A/W is achieved at 1550nm. At 40GHz, the WG-PDA chips with a 4-photodiode array show a RF output power of 10dBm and an OIP3 value of 26dBm. The WG-PDA chips with a 3-photodiode array generate a RF output power of 7.1dBm, 6.3dBm, 3.6dBm and 2.2dBm at 65GHz, 75GHz, 90GHz and 105GHz, respectively and an OIP3 value of 19dBm at 65GHz.

Waveguide integrated InP-based photodetector for 100Gbaud applications operating at wavelengths of 1310nm and 1550nm

We demonstrate a waveguide integrated pin-photodetector chip for 100Gbaud applications operating from the O-band to the L-band. By means of the photodetector chip 3rd order interception point measurements at highest reported frequencies up to 130GHz are presented.

Nonlinearities of High-Speed p-i-n Photodiodes and MUTC Photodiodes

The linearity, the RF output power, and the bandwidth for p-i-n photodiodes (PDs) and modified uni-traveling carrier (MUTC) PDs are analyzed for a variation of bias voltage and optical input power. Based on an equivalent circuit, equations for analytic calculation of these PD parameters are derived. Good agreement between the measurements and the calculated results of a p-i-n PD and a MUTC PD could be observed for frequencies up to 135 GHz. As a result, the linearity is improved and its photocurrent dependence can be reduced when the bandwidth of the PD is limited by the RC time constant.

PDL optimization in waveguide MQW pin photodiodes

In this paper, a simulation model is presented for optimizing the polarization dependent loss (PDL) of waveguide multiple-quantum well (MQW) pin photodiodes (PD). The model accounts for strain, carrier transit time through the MQW layers and free carrier density in the quantum wells.

56Gbaud DP-QPSK receiver module with a monolithic integrated PBS and 90° hybrid InP chip

A 56Gbaud dual polarization quadrature phase shift keying (DP-QPSK) receiver module is presented including an InP receiver chip. The chip consists of monolithically integrated polarization beam splitters (PBS), 90° hybrids and balanced photodiodes.

Monolithic integrated InP receiver chip for coherent phase sensitive detection in the C- and L-band for colorless WDM applications

We demonstrate a monolithically integrated coherent receiver PIC on an InP substrate with a 120° optical hybrid and 40GHz pin-photodetectors. Moreover, the performance of the device for colorless detection of 28Gbaud 16-QAM signals in the C- and L-band is investigated.