Misalignment Considerations in Laser Diode to Single Mode Circular Core Dispersion-shifted/Dispersion-flattened Fiber Coupling via Hyperbolic Microlens on the Fiber Tip [ ]

We report the theoretical investigation of the coupling efficiency in presence of possible transverse and angular mismatches in case of laser diode to single-mode circular core dispersion-shifted/dispersion-flattened fiber coupling via hyperbolic microlens on the fiber tip. The study comprises first theoretical investigations of coupling optics involving the said type of coupler in presence of such mismatches. Employing ABCD matrix formalism for refraction of paraxial rays by a hyperbolic microlens on the fiber tip, we formulate analytical expressions for the coupling efficiencies in presence of the said two misalignments. Further, the lens transmitted spot size of the source should be equal to the spot size of the fiber in case of maximum coupling. In this connection, we use Petermann II spot size of the fiber in order to take care of non-Gaussian nature of field of such fibers and to make the prediction of the launch optics more realistic thereby. The investigations are made for two different wavelengths namely 1.3 μm and 1.5 μm in case of some typical dispersion managed optical fibers. Although, our simple method predicts the concerned coupling optics excellently, the evaluation of the concerned efficiencies and associated losses will involve little computations. The results present the relevant coupling efficiencies along with the tolerance with respect to the said kinds of mismatches and as such it will benefit the designers and packagers who are working in the field of optical technology.