Optical systems are disclosed which include one or more components such as an optical multiplexer, an optical demultiplexer, and, an optical amplifier. An optical device is included in the optical system and is configured to communicate with the optical component(s). The optical device includes a substrate proximate to which is disposed a first waveguide array. A second waveguide array is also provided that is disposed proximate the substrate so that a portion of the second waveguide array intersects a portion of the first waveguide array at a predetermined angle, so that a junction is formed. An index of refraction associated with the junction can be varied so that desirable effects can be implemented concerning optical signals transmitted through the waveguides.