Cladding mode

About: Cladding mode is a research topic. Over the lifetime, 1233 publications have been published within this topic receiving 17815 citations.

Long-period fiber gratings as band-rejection filters

Abstract: We present a new class of long-period fiber gratings that can be used as in-fiber, low-loss, band-rejection filters. Photoinduced periodic structures written in the core of standard communication-grade fibers couple light from the fundamental guided mode to forward propagating cladding modes and act as spectrally selective loss elements with insertion losses act as backreflections <-80 dB, polarization-mode-dispersions <0.01 ps and polarization-dependent-losses <0.02 dB.

Cladding-mode resonances in short- and long-period fiber grating filters

Abstract: The transmission of a mode guided by the core of an optical fiber through an ultraviolet-induced fiber grating when substantial coupling to cladding modes occurs is analyzed both experimentally and theoretically. A straightforward theory is presented that is based on the calculation of the modes of a three-layer step-index fiber geometry and on multimode coupled-mode theory that accurately models the measured transmission in gratings that support both counterpropagating (short-period) and co-propagating (long-period) interactions. These cladding-mode resonance filters promise unique applications for spectral filtering and sensing.

Mode transition in high refractive index coated long period gratings.

Abstract: In this work, the numerical and experimental investigation of the cladding modes re-organization in high refractive index (HRI) coated Long Period Gratings (LPGs) is reported. Moreover, the effects of the cladding modes re-organization on the sensitivity to the surrounding medium refractive index (SRI) have been outlined. When azimuthally symmetric nano-scale HRI coatings are deposited along LPGs devices, a significant modification of the cladding modes distribution occurs, depending on the layer features (refractive index and thickness) and on the SRI. In particular, if layer parameters are properly chosen, the transition of the lowest order cladding mode into an overlay mode occurs. As a consequence, a cladding modes re-organization can be observed leading to relevant improvements in the SRI sensitivity in terms of wavelength shift and amplitude variations of the LPGs attenuation bands.

Plasmon resonances in gold-coated tilted fiber Bragg gratings.

Abstract: The transmission spectrum of fiber Bragg gratings with gratings planes tilted at a small angle (2°-10°) relative to the fiber axis shows a large number of narrowband cladding mode resonances within a 100 nm wide spectrum. When a gold coating with a thickness between 10 and 30 nm is deposited on the fiber, the transmission spectrum shows anomalous features for values of the outside medium refractive index between 1.4211 and 1.4499. These features are shown to correspond to the excitation of surface plasmon resonances at the external surface of the gold film.

Optical fiber refractometer using narrowband cladding-mode resonance shifts.

Abstract: Short-period fiber Bragg gratings with weakly tilted grating planes generate multiple strong resonances in transmission. Our experimental results show that the wavelength separation between selected resonances allows the measurement of the refractive index of the medium surrounding the fiber for values between 1.25 and 1.44 with an accuracy approaching 1x10(-4). The sensor element is 10 mm long and made from standard single-mode telecommunication grade optical fiber by ultraviolet light irradiation through a phase mask.