Abstract: A drop AOTF has a first AOTF that includes an optical fiber with a longitudinal axis, an acoustic wave propagation member with a proximal end and a distal end and an acoustic wave propagation member. The acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end of the acoustic wave propagation member. An optical circulator, with first, second and third ports, is coupled to the first AOTF at the third port. A mode coupler is coupled to the first AOTF. A orthogonal-polarization reflective mirror is coupled to the mode coupler.

Abstract: An optical add/drop multiplexer includes a mode converter. A first mode coupler is coupled to an input of the mode converter. A second mode coupler is coupled to an output of the mode converter. The mode converter includes an optical fiber with multiple cladding modes and a single core mode guided along a core. An acoustic wave propagation member is coupled to the optical fiber. The acoustic wave propagation member propagates an acoustic wave from its proximal to its distal end. At least one acoustic wave generator is coupled to the proximal end of the acoustic wave propagation member.

Abstract: An optical apparatus includes an optical fiber. A plurality of individual optical fiber deformation structures are positioned adjacent along a length of the optical fiber. Each of an individual optical fiber deformation structure introduces a mechanical or index deformation of a portion of the optical fiber to create perturbation in the optical modes in the fiber and provide a coherent coupling between two modes in the optical fiber.