Snapshot Mueller matrix polarimetry was performed for static and dynamic analyses of surface-stabilised ferroelectric liquid crystal cells under an electric field. A strong correlation between the static (at fixed voltage) and dynamic (upon field reversal) polarimetric properties and the texture of ferroelectric liquid crystal cells was established. The birefringence properties were different between a rooftop/zigzag-textured cell and a stripe-textured cell. The trajectory of the optic axis, plotted over the transition between two addressed states, was analysed for each cell. The shape of the trajectories could be explained by a reversible motion of the smectic layers while switching.

In optical telecommunication the need for switchable reflecting devices has often been expressed for wavelength routing or optical monitoring.1 The conventional method to realize these filters is to design a Bragg filter. However, these structures are obtained with very expensive technologies, as they are produced on substrates or photo-written in optical fibers. In this article, we test the cholesteric liquid crystal (CLC), which is a self-organized material owning the optical properties structurally well suited to reach these technical objectives: The CLC has almost the same properties as nematic except for a helical structure of the director. The helical axis is perpendicular to the director and this helix is characterized by the pitch. This periodic structure exhibits a periodical birefringence modulation that causes selective reflections of a circularly polarized light. The dielectric tensor is also undergoing a precession along the helical axis. Due to this structure, these liquid crystals have unique and very attractive optical properties

his paper describes the development of discrete optical filters operating in the visible spectra aiming the Wavelength-Division Multiplexing (WDM) links over Poly-Methyl-Methacrylate (PMMA) polymer optical fibres (POFs). The fabrication of notch and dichroic filters was carried out using a nematic liquid crystal (LC) doped with appropriate chiral dopant. In order to have the reflection of above 80% for the desired wavelength we used approximately 20 layers of cholesteric LC in a planar Grandjean texture. In order to operate the device for any given input polarisation, the cholesteric liquid crystal (CLC) with left handed helix will reflect left circularly polarised light while the right handed helix will reflect the right handed circularly polarised light.

In the last few years there has been an explosion in the amount of traffic carried by the Internet which made a huge increase in demand for bandwidth in core optical networks and we have witnessed the extensive deployment of wavelength- division multiplexed (WDM) networks. These systems are configured to allow multiple channels at different wavelengths to share the same optical fiber, increasing the effective transmission rate on that fiber. Optical network architectures can be characterized as opaque or all- optical (transparent) or as a compromise between opaque and transparent networks. Transparent (or all-optical) network architecture was proposed to reduce the associated cost of opaque networks [1]. In transparent WDM networks, data is transmitted from its source to its destination in optical form. Switching/routing operations are being performed in the optical domain without undergoing any optical-to-electrical conversion. According to the state of the technology, various factors degrade the quality of an analog optical signal along its route. As the signal propagates in a transparent way, these impairments accumulate along the path, and limit the system reach and overall network performance. These physical layer constraints may be classified into linear and nonlinear impairments. In a transparent optical network, beside impairments that accumulate along the path there is an impact of failures which also propagates through the network and therefore cannot be easily localized and isolated. Failure management is one of the crucial functions and prerequisite for protection and restoration schemes. In order to realize the vision of transparency while offering strict QoS guarantees, it is necessary to monitor and control optical network.