Advances in telecom and datacom optical components

We review and contrast key technologies developed to address the optical components market for communication applications. We first review the component requirements from a network perspective. We then look at different material systems, compare their properties, and describe the functions achieved to date in each of them. The material systems reviewed include silica fiber, silica on silicon, silicon on insulator, silicon oxynitride, sol-gels, polymers, thin-film dielectrics, lithium niobate, indium phosphide, gallium arsenide, magneto-optic materials, and birefringent crystals. We then describe the most commonly used classes of optical device technology and present their pros and cons as well as the functions achieved to date in each of them. The technologies reviewed include passive, actuation, and active technologies. The passive technologies described include fused fibers, dispersion-compensating fiber, beam steering, Bragg gratings, diffraction gratings, holographic elements, thin-film filters, photo...

Optical communication components

Inhomogeneous polymer-dispersed liquid crystal devices having gradient droplet distribution were fabricated and their phase retardation characterized. The gradient refractive index profile can be used as switchable prism gratings, and positive and negative lenses with tunable focal lengths. Such a tunable electronic lens is a broadband device and can be used for unpolarized light.

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Inhomogeneous nanoscale polymer-dispersed liquid crystals with gradient refractive index

— Refractive indices of two photocurable polymers, NOA65 and NOA81 (Norland Optical Adhesive), and two series of Merck liquid crystals, E-series (E44, E48, and E7) and BL-series (BL038, BL003 and BL006), and two UCF high-birefringence liquid-crystal mixtures were measured using an Abbe refractometer in the visible spectral region and 15–55°C temperature range. Some liquid crystals have excellent index matching with NOA65 in the red, while some fit better in the blue spectral region. To validate this index-matching property found in the material level, we prepared some polymer-dispersed liquid-crystal devices. Good correlations between material and device performances are obtained.

Refractive-index matching between liquid crystals and photopolymers

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

An electrically tunable optical filter has been developed that uses a polymer containing fine droplets of nematic liquid crystal as the active cavity in a Fabry-Perot interferometer (FPI). This FPI filter, whose finesse was 62, had a free spectral range of 37 nm in the 1.55-/spl mu/m range with a full-width at half maximum of 0.6 nm and a transmission loss of 2.4 dB. The polarization dependent loss was smaller than 0.17 dB. The transmitted peak wavelength decreased with an electric field. This resulted in a tuning range of 10 nm at 300 V. The switching time was about 370 /spl mu/s.

S. Sakata

Papers

Tunable wavelength filter using nano-sized droplets of liquid crystal