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Departmental Seminar

Nonlinear effects mitigation on WDM signals enabled by optical phase conjugation
When Jun 12, 2017
from 03:00 PM to 05:00 PM
Where Roberts Building 508
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Speaker: Dr Francesca Parmigiani

Title: Nonlinear effects mitigation on WDM signals enabled by optical phase conjugation


The reduced receiver sensitivity of higher order modulation formats means that their adoption often requires an increase in transmission power. Unfortunately, the presence of Kerr nonlinearity in optical fibre means that there is a limit to how high transmission powers can be made. Eventually, the signals become degraded due to nonlinear cross-talk, meaning that any further increase in transmission power actually decreases the capacity. A possible solution to overcome this limitation is to apply mid-link optical phase conjugation (OPC). For optimal performance, OPC should be performed at the exact mid-point of a link, whilst power and group phase evolution should be precisely symmetric about the point of conjugation. Many demonstrations of OPC, therefore, take advantage of the lab setting to meet these two criteria as best as possible. Of course, in the real world, we are unlikely to have such facility, and will most likely be dealing with links of uneven span lengths which are bulk-amplified with erbium-doped fibre amplifiers (EDFAs). It is therefore invaluable to deploy OPC in realistic links to understand truly the magnitude of the benefit we can expect to extract from a field-installed system.

In this talk, I will present nonlinear impairment mitigation of wavelength division multiplexed (WDM) signals, through mid-link OPC. We conduct our experiments on dispersion-managed and dispersion-unmanaged installed fibre links with periodic lumped amplification by conventional EDFAs. Our OPC configuration realizes efficient reuse of the signal bandwidth, avoiding the loss of half of the spectral band typical of most phase conjugating schemes. We demonstrate the operation of the system using both different advanced modulation formats and transmission distances.