Abstract
We present an analysis of clock recovery algorithms in both polarization division multiplexing systems and mode division multiplexing systems. The impact of inter-polarization time skew and polarization mode dispersion in single-mode fibers, as well as the combined impact of mode mixing and mode group delay spread in multi-mode fibers under different coupling regimes are investigated. Results show that although the clock tone vanishing has a known solution for single-mode systems, in multi-mode systems even for low group delay spread, strong coupling will cause clock tone extinction, making it harder to implement an effective clock recovery scheme.
Highlights
In the past few years, coherent communication techniques have established themselves as the main solution to overcome the capacity limitations of legacy intensity modulation/direct detection (IM-DD) systems in optical communications [1]
We showed through simulations that the inter-polarization time skew, polarization rotation, and polarization mode dispersion (PMD) can be compensated in optical systems employing single-mode fibers and, will not affect the performance of clock synchro√nization
It would need more than 10,000 km of a modern fiber with differential group delay (DGD) of 0.1 ps/ km in order to be able to see some impact of DGD on the clock recovery performance
Summary
In the past few years, coherent communication techniques have established themselves as the main solution to overcome the capacity limitations of legacy intensity modulation/direct detection (IM-DD) systems in optical communications [1]. The first implementations of DSP-based coherent optical receivers were deployed envisioning systems with 100 Gb/s per channel over single-mode fibers (SMF), and employing polarization division multiplexing (PDM) and advanced modulation formats such as m-ary phase-shift keying (M-PSK) and m-ary quadrature amplitude modulation (M-QAM) [2,8]. Such systems in combination with wavelength division multiplexing (WDM) can not satisfy future capacity demands.
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