All-optical 1310 to 1550 nm wavelength conversion by utilising nonlinear polarisation rotation in semiconductor optical amplifier - Electronics Letters

Introduction: One of the key components in all-optical communication networks using the whole low-loss bandwidth of the silica fibre is an ultra-wideband wavelength converter [1]. Use of all-optical ultrawideband wavelength converters enhances network flexibility, allowing an all-optical wavelength conversion between different transmission windows, and therefore avoiding the bottleneck of optical-electricaloptical conversion. This will become of particular importance at the network nodes interfacing metro-access systems employing the whole low-loss bandwidth of the silica fibre, and the core network traditionally centred in a 1550 nm window. A number of metro-access schemes utilising simultaneously 1310 and 1550 nm transmission windows have been proposed, e.g. [2, 3]. Ultra-wideband wavelength converters applied in metro-access systems have to deliver high performance while remaining cost-effective. A cost-effective alternative to 1310 to 1550 nm wavelength converters based on expensive LiNbO3 waveguides [4], are wavelength converters employing semiconductor optical amplifiers (SOAs). Previously demonstrated SOA-based 1310 to 1550 nm wavelength converters which were based on a split contact SOA [5] and a distributed feedback SOA [6] operated at bit rate below 1 Gbit=s. The highest reported, 1.25 Gbit=s error-free 1310 to 1550 nm wavelength conversion was achieved with an SOA operating in MachZehnder interferometer (MZI) configuration [1]. However, a complicated control mechanism is required and the bit rate is limited to below 2 Gbit=s. In this Letter, we report a novel all-optical 1310 to 1550 nm wavelength converter based on nonlinear polarisation rotation in an SOA. We demonstrate that error-free wavelength conversion from 1310 to 1550 nm can be realised at bit rate 20 Gbit=s by using a single SOA. The nonlinear polarisation rotation in the SOA had been applied previously for demultiplexing [7] or in-band wavelength conversion [8]. However, nonlinear polarisation rotation in the transparency region of the SOA has not been reported.