Applications of Active Thin Film Coatings on Optical Fibers

ABSTRACTActive thin film coatings on optical fibers provide a variety of functions that are being used to develop active all-fiber optical devices. Two types of active coatings that are of interest for device development include resistive and piezoelectric coatings. Resistive coatings can be used to heat an optical fiber, while piezoelectric coatings can be used to strain the fiber. Localized changes in the fiber waveguiding properties can be achieved by electrically activating the fiber coating. These coated fibers show promise for applications such as optical phase shifters and modulators.Recent developments in the fabrication of diffraction gratings within the core of an optical fiber have provided the means for making a variety of intra-core reflection and band pass filters. By combining these passive intra-core fiber devices with active coatings, wavelength tunable devices have been demonstrated. Wavelength tunable devices are expected to have a variety of applications in telecommunications and sensing networks. A review of recent developments in fiber coating and analysis techniques, device fabrication, and applications of active all-fiber devices are presented along with a discussion of which coating materials are of interest in active devices.