Guanyu Chen

Integrated switchable mode exchange for reconfigurable mode-multiplexing optical networks

We propose and experimentally demonstrate an on-chip switchable mode exchange utilizing a Mach-Zehnder interferometer assisted by a phase shifter. The switchable functionality, which is essential for an advanced and reconfigurable optical network, can be realized by controlling the induced phase difference. The measured extinction ratio is ∼24  dB over the C band for OFF-ON switchover. For demonstration, open and clear-eye diagrams can be observed when processing non-return-to-zero on-off keying signals at 10 Gb/s. The bit error rate measurements indicate a reasonable power penalty of less than 1 dB for two-mode exchange. The proposed device can further promote advanced and flexible mode-multiplexing optical networks.

On-chip WDM mode-division multiplexing interconnection with optional demodulation function.

We propose and fabricate a wavelength-division-multiplexing (WDM) compatible and multi-functional mode-division-multiplexing (MDM) integrated circuit, which can perform the mode conversion and multiplexing for the incoming multipath WDM signals, avoiding the wavelength conflict. An phase-to-intensity demodulation function can be optionally applied within the circuit while performing the mode multiplexing. For demonstration, 4 × 10 Gb/s non-return-to-zero differential phase shift keying (NRZ-DPSK) signals are successfully processed, with open and clear eye diagrams. Measured bit error ratio (BER) results show less than 1 dB receive sensitivity variation for three modes and four wavelengths with demodulation. In the case without demodulation, the average power penalties at 4 wavelengths are -1.5, -3 and -3.5 dB for TE₀-TE₀, TE₀-TE₁ and TE₀-TE₂ mode conversions, respectively. The proposed flexible scheme can be used at the interface of long-haul and on-chip communication systems.

Bandwidth improvement for germanium photodetector using wire bonding technology

We demonstrate an ultrahigh speed germanium photodetector by introducing gold wires into the discrete ground electrodes with standard wire bonding technology. To engineer the parasitic parameter, the physical dimension of the gold wire used for wire bonding is specially designed with an inductance of about 450 pH. Simulation and experimental results show that the bandwidth of the photodetector can be effectively extended from less than 30 GHz to over 60 GHz.

Phase regeneration for polarization-division multiplexed signals based on vector dual-pump nondegenerate phase sensitive amplification

The polarization-division multiplexing (PDM) technology is a practical method to double the transmission capacity, and the corresponding phase regeneration (PR) for PDM signals is meaningful and necessary to extend the transmission distance and increase the transparency for the phase-encoded PDM system. Those reported PDM PR schemes either utilized polarization-diversity technique or required special PDM format. In order to overcome these issues, the PR for the PDM phase-modulated signals is proposed and theoretically demonstrated in this paper, based on the vector dual-pump nondegenerate phase sensitive amplification (PSA). The theoretical model is established and the detailed characteristics are investigated to optimize the PR performance. Results show an obvious phase squeezing for the degraded 80 Gbit/s PDM differential phase-shift keying (DPSK) signals, and the error vector magnitude (EVM) of the regenerated signals on dual polarization states can be improved from 22.58% and 21.39% to 4.57% and 4.63%, respectively. Furthermore, the applicability of the proposed scheme for PDM quaternary-phase shift keying (QPSK) signals is investigated. The proposed scheme can be useful and promising in current PDM based coherent fiber-optic communication.

An SOI based polarization insensitive filter for all-optical clock recovery.

We propose and fabricate an SOI based polarization diversity scheme consisting of two 2D grating couplers and a micro ring resonator. Based on this scheme, all-optical polarization insensitive clock recovery has been demonstrated successfully.

On-chip switch for reconfigurable mode-multiplexing optical network.

The switching and routing is essential for an advanced and reconfigurable optical network, and great efforts have been done for traditional single-mode system. We propose and demonstrate an on-chip switch compatible with mode-division multiplexing system. By controlling the induced phase difference, the functionalities of dynamically routing data channels can be achieved. The proposed switch is experimentally demonstrated with low insertion loss of ~1 dB and high extinction ratio of ~20 dB over the C-band for OFF-ON switchover. For further demonstration, the non-return-to-zero on-off keying signals at 10 Gb/s carried on the two spatial modes are successfully processed. Open and clear eye diagrams can be observed and the bit error rate measurements indicate a good data routing performance.

An ultra-low crosstalk and broadband two-mode (de)multiplexer based on adiabatic couplers

A novel adiabatic couplers (ACs) based broadband and fabrication-tolerant two-mode multiplexer (MUX) is designed using silicon-on-insulator (SOI) platform. Being different from the previously reported ACs-based scheme, the converted and multiplexed signals are on conventional modes, rather than supermodes. The experimental results are in good agreement with the simulations. Over a wavelength range of 75 nm measured, the crosstalk is lower than −20 dB, and the insertion loss is ~1 dB. The eye diagram and bit error rate measurements validate the good performance of the proposed mode MUX. The investigation on fabrication tolerance indicates reasonable performance degradation for a large gap deviation from −30 to 30 nm and etching depth deviation from −50 to 50 nm.

A Low Crosstalk and Broadband Polarization Rotator and Splitter Based on Adiabatic Couplers

A low crosstalk and broadband polarization rotator and splitter (PRS) consisting of a bi-level adiabatic taper, a symmetric micro Y-junction and adiabatic couplers is proposed and demonstrated using a silicon-on-insulator platform. Due to the principle of mode evolution, the proposed PRS exhibits superior performance over a broad bandwidth. The waveguide with a thin ridge layer is introduced to reduce the crosstalk from TM0 mode and increase the coupling strength of TE0 mode. The proposed PRS is experimentally demonstrated with a loss about 1 dB and a crosstalk about -14 dB over a wavelength range of 100 nm.

Optical Phase Erasure and Wavelength Conversion Using Silicon Nonlinear Waveguide With Reverse Biased PIN Junctions

We demonstrate the optical phase erasure and wavelength conversion based on the nontransparency four-wave mixing simultaneously using the integrated silicon waveguide with reverse biased PIN junction. By optimizing the design of the waveguide, a conversion efficiency of

Wide Locking Range and Multi-Channel Clock Recovery Using a Silicon Microring Resonator

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