The ever growing demand for higher data rate is rapidly exhausting the capacity available for single-mode fibres (SMFs). During the last years, only a marginal increase in the maximum bit rate distance product using SMFs was observed, since the nonlinear Shannon limit is being reached. Moreover, it has been demonstrated that even if significant improvements of standard SMFs (SSMFs) are achieved, the capacity increase per fibre is limited.
Mode-division multiplexing (MDM) over few-mode fibres (FMFs) is emerging as an attractive solution for the required capacity increase with potential cost, space, and energy savings. An N-fold capacity increase, with N equal to the number of independent modes of the FMF, is obtained using MDM. However, FMFs require the usage of multiple-input multiple-output (MIMO) equalization as it needs to compensate for the combined effect of differential mode delay (DMD) and modal crosstalk (XT), which originates a channel impulse response (CIR) spread over time. In order to reduce the equalizer complexity the fibre DMD has to be reduced.
In the literature, different schemes to reduce or compensate DMD have been proposed: the usage of inherently low DMD FMFs (ILD-FMFs); the usage of FMFs with positive DMD followed by FMFs with negative DMD, usually referred as DMD compensated FMFs (DC-FMFs); or the usage of mode permutation within the transmission fibre, which averages the modes group velocities, thereby reducing the CIR length. The reported ILD-FMFs and DC-FMFs are not suitable for ultra-long haul transmission due to high DMD variation within the C+L band. Regarding the mode permutation scheme, an increase of the maximum distance reach by a factor of 5 has been shown. However, a practical implementation of mode permutation is still missing.
The main objectives of this work are the proposal of design rules for FMFs with an arbitrary DMD flattened over the C+L band, and the investigation of schemes for the practical implementation of mode permutation.
|Funding: Coriant Portugal, FCT|
|Start Date: 01-09-2010|
|End Date: 01-09-2014|
|Team: Henrique José Almeida da Silva, Daniel Diogo Trindade Fonseca, Filipe Marques Ferreira|
|Groups: Optical Communication Systems and Networking – Co|
|Partners: Coriant Portugal|
|Local Coordinator: Henrique José Almeida da Silva|