All-optical format conversions from NRZ to BPSK and QPSK based on nonlinear responses in silicon microring resonators

Yuanyuan Lu,Fangfei Liu,Min Qiu,Yikai Su

doi:10.1364/oe.15.014275

Abstract

We propose and numerically verify a novel scheme of all-optical format conversion from non-return-to-zero (NRZ) to binary phase-shift- keying (BPSK) at 160 Gb/s using cascaded microring resonators (CMRR) on a single silicon chip. The conversion is based on large phase shift and flattened intensity-response characteristics in the CMRR. A continuous-wave light experiences different phase shifts controlled by the power of an input NRZ signal with an ~8.8-dB extinction ratio, while maintaining approximately the constant intensity. All-optical format conversion from NRZ to quadrature phase-shift-keying (QPSK) is also demonstrated based on parallel NRZ/BPSK converters in a Mach-Zehnder interferometer structure.

Highlights

All-optical modulation-format conversion may become a key technology for future optical networks, which could employ different modulation formats according to the network scales and applications
Conversion from OOK to quadrature phase-shift-keying (QPSK) has been proposed based on four integrated semiconductor optical amplifiers (SOAs) in a MachZehnder interferometer (MZI) configuration [13]
The nonlinearity in highly nonlinear fiber (HNLF) or photonic crystal fiber (PCF) is attractive in format conversion due to its ultrafast nonlinear response

Summary

Introduction

All-optical modulation-format conversion may become a key technology for future optical networks, which could employ different modulation formats according to the network scales and applications. Format conversion from OOK to PSK can be realized using nonlinearity in semiconductor optical amplifiers (SOAs) [9, 10], cross-phase modulation (XPM) in highly nonlinear fiber (HNLF) [11], or XPM in photonic crystal fiber (PCF) [12]. Conversion from OOK to QPSK has been proposed based on four integrated SOAs in a MachZehnder interferometer (MZI) configuration [13]. We present a novel scheme for NRZ to binary phase-shift-keying (BPSK) format conversion by cascading microring resonators on a silicon chip. We propose NRZ to quadrature phase-shift-keying (QPSK) format conversion using a parallel NRZ/BPSK converter. The conversion is based on the nonlinear-resonance detuning characteristics caused by Kerr effects in silicon, which is feasible at 160 Gb/s or even higher bit rates [14].

Theory and operation principle

Simulation results and discussion

Conclusion