Polarization Stabilization in Optical Communications Systems

Abstract

The control of the state of polarization (SOP) of light remains one of the open issues in optical communications. In particular, the achievement of a stabilization of the SOP can find many applications in advanced optical communication systems: from the mitigation of polarization-mode dispersion to the development of novel multilevel modulation formats. In this paper, theoretical and experimental aspects of polarization stabilization are dealt with, and a novel algorithm to overcome the issues related to the practical availability of finite-range birefringent components and to solve the requirement for endless stabilization is also presented. The practical implementation of the polarization stabilizer is discussed, and experimental demonstrations based on liquid crystal and magnetooptical retarders are shown

QBER Estimation in QKD Systems With Polarization Encoding

“…We account for this aspect by modeling the angle between the obtained and the target SOPs in the Stokes space as (17) where is the angle without the feedback SOP control, and is the characteristic time decay of the obtained SOP to .…”

“…However, if the effects of polarization dependent losses are negligible, the relation between the SOP at the input and output of the fiber is unitary [16]. This means that the SOP changes can be reversed by compensating two non-orthogonal SOPs [10], [16], [17]. An active full polarization control scheme using two classical signals at different wavelengths is reported in [9] and [12].…”

Nonlinear Polarization Manipulation in Optical Fibers

“…In many fields of photonics, in particular in all-fiber based systems, the light state-of-polarization (SOP) remains one of the most elusive variables, which is still difficult to predict and control [1]. Indeed, despite the impressive progress in the manufacturing process of modern Telecom optical fibers, the residual birefringence combined with environmental surrounding stress and variations like bending, squeezing, vibrations or temperature fluctuations make the polarization of light unpredictable after only a few hundreds of meters of propagation.…”

Broadband polarization pulling using Raman amplification

“…Such polarization controllers provide a very fast response time, overcoming an important drawback of polarization control schemes based on optoelectronic elements [1]. Besides that, the possibility to convert unpolarized light to polarized light with unitary efficiency in terms of energy represents a huge advantage over the standard polarizers that waste 50% of the unpolarized light.…”