A type of object in which this structure has a spiral shape efficiently couples the modes of a diode laser, allowing it to be used as a pump source. One system that uses multiple examples of this structure has very low microbending loss (-5[1])and can be tuned to compensate for dispersion. To prevent damage to it and increase its stability, this structure is coated by a buffer and a jacket. Two layers of this type of structure allow for propagation of multiple (*) wavelengths (-5[1])in the (-5[1])“double”-this structure geometry. (10[1])This component (-5[1])is generated (-5[1])by (-5[1])drilling patterned holes in silica in a photonic crystal-based design for the larger device it is part of. This structure (10[1])has a lower refractive (-5[1])index than the innermost layer, allowing for signals (-5[1])to be propagated (10[1])via total internal reflection. (10[1]-5[3])For 10 points, name this layer of an optical fiber that surrounds (-5[1])the core. (10[2])■END■ (10[8]0[10])