PROPAGATION CHARACTERISTICS OF MICROSTRUCTURED SPECIALTY OPTICAL FIBERS

Abstract

We have studied propagation characteristics of some microstructured optical fibers which include holey fibers, photonic band gap fibers, segmented cladding fibers and other large mode area Fibers. in particular, we have proposed a novel large mode area optical fiber having multilayer cladding. The fiber is essentially a leaky structure employing alternate high and low refractive index layers in the cladding region. The mode propagation constant and the leakage loss of the first two modes of the fiber are calculated using the matrix method. The leakage loss of the LPI i mode is found to be two orders of magnitude higher than that of the fundamental node. To be specific, the leakage loss of the fundamental mode and the first higher order mode are found to be 6 dB/km and 335.5 dB/km respectively at 1550 nm of wavelength. The high differential loss between these two modes explains the effective single mode operation. The fiber has shown effective single mode operation in the wavelength range of 1000 - 1600 nm with a core diameter as large as 17 μ.n1. The mode field patterns of the first two modes are similar to that of a conventional fiber in the core region. Normalized propagation constant and the leakage loss of a leaky structure with a power law profile of index variation in the cladding layers are obtained and plotted with respect to profile parameter. These curves are universal in nature and the mode propagation constant and the leakage loss of fiber with any profile parameters can be easily obtained using these curves. The fiber is expected to find applications in optical communication systems employing dense wavelength division multiplexing (DWDM) and high power amplifiers and lasers. ix