Patent ID: 8538212

Claim:
A planar lightwave circuit comprising: a combined signal waveguide; a set of dispersed signal waveguides; a first slab waveguide; a first mirror optically connected to the first slab waveguide; a mirror assembly supporting the first mirror; a waveguide array; and a second slab waveguide, wherein the waveguide array optically connected the first slab waveguide and the second slab waveguide to provide an arrayed waveguide grating, wherein the combined signal waveguide or the set of dispersed signal waveguides is optically connected at an access edge to the first slab waveguide and the other of the combined signal waveguide or the set of dispersed signal waveguides is optically connected to the second slab waveguide and wherein an optical path through the first slab waveguide from the access edge is folded by providing an optical reflection from the first mirror to the array edge connecting the waveguide array and the appropriate element of the combined signal waveguide or the set of dispersed signal waveguides, wherein the configuration of the reflection off of the first mirror is at a reflection angle of no more than about 80 degrees and the ratio of the optical path distance from the access edge to the first mirror as compared to the optical path distance from the waveguide array to the first mirror being from about 0.5 to about 2, and wherein the mirror assembly comprises an actuator that pivots the first mirror in response to a change in temperature to change the angle to provide effectively temperature compensated transmission of light through the arrayed waveguide circuit over a selected temperature range.