Liquid crystal technology has become, nowadays, one of the core technologies for implementing optical functions for WDM networks. Their advantage, with respect to other materials, is their unequalled engineering capability which is nowadays decisive in providing more flexible and cost effective systems. First, we briefly review the main driving physical features determining their optical and dynamic behaviour, illustrated through various pure or composite liquid crystal materials. Second, we discuss their suitability for use in some telecommunication requirements. Finally we give examples illustrating the huge variety of their possible effects, in particular when engineered with polymer chains.

Engineering liquid crystals for optimal uses in optical communication systems

Objective and background: We present a new version of Bossa Nova Technologies' passive polarization imaging
camera. The previous version was performing live measurement of the Linear Stokes parameters (S 0 , S 1 , S 2 ), and its
derivatives. This new version presented in this paper performs live measurement of Full Stokes parameters, i.e. including
the fourth parameter S 3 related to the amount of circular polarization. Dedicated software was developed to provide live
images of any Stokes related parameters such as the Degree Of Linear Polarization (DOLP), the Degree Of Circular
Polarization (DOCP), the Angle Of Polarization (AOP).
Results: We first we give a brief description of the camera and its technology. It is a Division Of Time Polarimeter using
a custom ferroelectric liquid crystal cell. A description of the method used to calculate Data Reduction Matrix (DRM) 5,9 
linking intensity measurements and the Stokes parameters is given. The calibration was developed in order to maximize
the condition number of the DRM. It also allows very efficient post processing of the images acquired. Complete
evaluation of the precision of standard polarization parameters is described. We further present the standard features of
the dedicated software that was developed to operate the camera. It provides live images of the Stokes vector
components and the usual associated parameters. Finally some tests already conducted are presented. It includes indoor
laboratory and outdoor measurements. This new camera will be a useful tool for many applications such as biomedical,
remote sensing, metrology, material studies, and others.

Full Stokes polarization imaging camera

We present a linear Stokes polarization camera working at visible wavelength. The camera is both compact and robust for use in field experiments and outdoor conditions. It is based on fast polarization modulator. Four polarization states images are acquired successively. Processing software allows live calculation, visualization and measurement of polarization images deduced from the acquired images. The architecture of the hardware, calibration results and sensitivity measurements is presented. Polarization image processing including polarization parameters computed are proposed. These parameters include linear Stokes parameters (S0, S1 and S2), usual polarization parameters (intensity, degree of linear polarization, and angle of polarization) and other polarization based parameters (polarized image, depolarized image, virtual polarizer, polarization difference). Color data fusion and vector overlay algorithms are presented. Finally experimental results and observations as well as possible applications are discussed.

Compact and robust linear Stokes polarization camera

We demonstrate an in-line polarization controller based on a hollow optical fiber filled with a nematic liquid crystal by fabricating thin-film electrodes on the cladding of a fiber. The polarization controller consists of three control sections with fixed optic axes, which operate as phase retarders. The phase retardation in each section is controlled by the magnitude of the applied electric field. The full wave retardation voltage of the polarization controller is approximately 85 V.

In-line polarization controller that uses a hollow optical fiber filled with a liquid crystal

In this letter, we report a fast and endless polarization controller based on lead lanthanum zirconate titanate (PLZT) ceramic programmable waveplates. A set of four volume electrodes placed in a cylindrical arrangement are drilled in an electrooptic ceramic plate. By using the Kerr effect, and taking advantage of the high electrooptic coefficient and fast response time of the PLZT, we thus, obtain a fast rotatable and variable waveplate. Then, cascading two of these waveplates produces an endless polarization controller.

Endless fiber-to-fiber polarization controller based on ceramic programmable waveplates

Endless smectic A* liquid crystal polarization controller

Cet article expose le principe d'un controleur de polarisation rapide, sans fin, pour la compensation dynamique de dispersion de mode de polarisation (PMD). On montre de quelle facon un tel composant peut-etre utilise comme une lame de phase variable a axe tournant, et les avantages qui en resultent pour l'optimisation des algorithmes de recherche de l'etat de polarisation. On presente quelques resultats experimentaux obtenus a partir d'une cellule a cristal liquide electrocline, alignee de maniere homeotrope et utilisee comme lame de phase variable, a axe tournant. On discute ensuite les performances d'un tel composant et de quelle facon il est possible d'ameliorer ses caracteristiques de maniere a repondre aux specifications exigees aujourd'hui par un systeme de compensation de PMD.

Thierry Sansoni

Papers

Endless smectic A* liquid crystal polarization controller

Fast liquid crystal end-less polarisation controller for first order PMD compensation