Abstract
Polarization insensitive wavelength conversion of a 40 Gb/s non-return-to-zero (NRZ) differential phase-shift keying (DPSK) data signal is demonstrated using four-wave mixing (FWM) in a silicon nanowire circuit. Polarization independence is achieved using a diversity circuit based on polarization rotators and splitters, which is fabricated by a simple process on the silicon-on-insulator (SOI) platform. Error-free performance is achieved with only 0.5 dB of power penalty compared to the wavelength conversion of a signal with well optimized input polarization. Additionally, data transmission over 161 km standard single-mode fiber (SSMF) is demonstrated at 40 Gb/s using optical phase conjugation (OPC) in the proposed circuit.
Highlights
All-optical wavelength converters (AOWCs) are key components to be employed in wavelength division multiplexing (WDM) optical communication systems in order to enable routing or resolve traffic bottleneck issues in networks nodes [1]
This power penalty caused by a reduced optical signal-to-noise ratio (OSNR) at the output of the converter could be decreased by having a higher conversion efficiency, which could be obtained using a higher input pump power
The eye closure is clearly due to the action of the polarization scrambler and not to the fact that the reference waveguide is shorter, since approximately the same conversion efficiency as with the 1.5 cm waveguide with polarization splitters and rotators (PSRs) was measured
Summary
All-optical wavelength converters (AOWCs) are key components to be employed in wavelength division multiplexing (WDM) optical communication systems in order to enable routing or resolve traffic bottleneck issues in networks nodes [1]. Since only one polarization needs to be processed after the first PSR, the scheme offers more freedom for dispersion engineering of the nonlinear silicon nano-waveguide in order to obtain broad-band high-efficiency wavelength conversion. To achieve polarization-insensitive wavelength conversion, a silicon Pol-D circuit based on a PSR has been designed. This test device consists of two fully etched apodized TE and TM input grating couplers [24] followed by a directional couplerbased mode combiner. It is negligible since a 150 μm long tapering length for the TM0-TE1 mode converter can guarantee a conversion efficiency higher than 99% [21]
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