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Challenges of chromatic dispersion and polarisation mode dispersion in today’s networks By Chris Dunford, Product Line Manager, Network Deployment and Operations, EXFO
Chris Dunford tells Broadband Journal about the importance of managing dispersion phenomena as part of comprehensive FIBRE characterisation to ensure high performance and reliability in high-speed FIBRE optic networks.
As networks operate at higher speeds, I guess challenges are aways likely. Fibre optic networks are the backbone of modern telecommunications, enabling high-speed data delivery within communities and globally. At higher speeds, phenomena like chromatic dispersion (CD) and polarisation mode dispersion (PMD) become significant challenges, impacting signal integrity and quality of service (QoS). Tell me about chromatic dispersion (CD) - how does it affect network performance? Chromatic dispersion is an inherent characteristic of optical fibres, resulting from material dispersion and waveguide dispersion. It causes different wavelengths to arrive at different times, leading to pulse broadening, potential overlap, distortion, signal degradation and bit errors. This reduces data rates and impacts connected systems and customers.
Ok, how do different types of optical fibres influence chromatic dispersion? Standard ITU-T G.652 optical fibres have “natural dispersion,” while alternatives like ITU-T G.653 Zero Dispersion-Shifted Fibres and ITU-T G.655 Non-Zero Dispersion-Shifted Fibres are designed to mitigate CD. Operators must know their fibre types to manage CD effectively, especially in mixed networks. Fair enough. In that case, what is this polarisation mode dispersion (PMD) I keep hearing about? PMD is a statistical phenomenon where imperfections in the fibre’s core or cladding cause different polarisation states to travel at different speeds, resulting in Differential Group Delay (DGD). This can impair signals and increase bit error rates.
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Volume 46 No.3 September 2024
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