Polarisation and wavelength division multiplexing at 1.55 ?m for bandwidth enhancement of multimode fibre based access networks

We demonstrate how a combination of polarisation-division multiplexing (PDM) and wavelength-division multiplexing (WDM) applied to graded index 50 mum multimode fibres (MMF) at 1.55 mum can be used to greatly increase the available optical bandwidth. A proof of principle experiment demonstrated error-free data transmission over 3km of MMF, using two 100GHz-spaced wavelengths, each carrying two 2.5Gb/s orthogonal PDM multiplexed channels, resulting in a 10Gb/s data rate. Polarisation and wavelength demultiplexing were simultaneously achieved by use of a grating based monochromator. We also practically implemented this transmission scheme in an all-fibre experiment, replacing the monochromator by a more convenient polarisation-insensitive, 200GHz ITU grid spacing 62.5 mum MMF pigtailed WDM demultiplexer. Using two polarizations each on four wavelengths (2P x 4lambda), we repeatedly achieved error-free data transmission for both circularly and linearly polarisation-wavelength-division-multiplexed channels over a MMF span of 300m, featuring a 20Gb/s data rate. Overall, we have demonstrated a major increase in the MMF bandwidth-distance product up to 30GHz-km.