“…These require ments are satisfied for single crystal waveguides and long single crystals the axis of which coincides with the optical axis of the crystal [3,4] for orthorhombic, tet ragonal, hexagonal, and cubic syngonies [13,14]. In recent years, the attention of researchers turned to stresses that appear in waveguides due to three dimen sional deformations (stresses at waveguide ends, under varying temperature along the waveguide axis) [12,15]. In this case, stresses also can be reconstructed using a technique that has been developed in recent decades [7,10,16].…”