The present invention relates to a microstructured optical fiber including a photonic band gap-guided core; and at least one index-guided core. Another embodiment of the present invention relates to a microstructured optical fiber including a set of main cores; a microstructured region surrounding the set of main cores; and at least alignment core, the alignment cores having substantially different optical propagation properties than the main cores. The present invention also includes methods for coupling, monitoring, and locating discontinuities in the fibers of the present invention.