Quantum key distribution (QKD) enables unconditionally secure communication guaranteed by the laws of physics. The last decades have seen tremendous efforts in making this technology feasible under real-life conditions, with implementations bridging ever longer distances and creating higher rates. Readily deployed glass fiber connections are a natural choice for distributing single photons nece...

Coherent detection employing multilevel modulation formats has become one of the most promising technologies for next generation high speed transmission systems due to the high power and spectral efficiencies. Using the powerful digital signal processing (DSP), coherent optical receivers allow the significant equalization of chromatic dispersion (CD), polarization mode dispersion (PMD), phase n...

In this paper we briefly review the work on dispersion compensating fibers (DCFs) in the last few years. Starting with the basic principle behind DCF, its need for upgrading the 1310 nm optical fiber links is discussed. The experimental and theoretical results of some researchers have been cited. The latest trend in optical communication has been to use dense wavelength division multiplexed (DW...