Dimensionally stable device construction

An optical device disposed on a first major surface of a substrate, the device having input and output optical signal paths, sensing means associated with a said output optical signal path and arranged to detect a reduction of a signal on that path corresponding to a distortion of the substrate, means for applying a force to the substrate, and feedback control means responsive to the sensing means for controlling said force applying means so as to negate said distortion of the substrate.

An optical micro-electro-mechanical system (MEMS) device disposed on a first major surface of a substrate, the device having a first set of input optical waveguides, a second set of output optical waveguides, an array of switch elements disposed on said first major surface and each arranged to couple selectively optical signals between a respective input optical waveguide and output optical waveguide, signal sensing means associated with one or more of said output optical waveguides and arranged to detect a distortion of the substrate as a variation in amplitude of a signal carried on said one or more output optical waveguides, means for applying a force to the substrate, and feedback control means responsive to the sensing means for controlling said force applying means so as to negate said distortion of the substrate.

An optical device disposed on a first major surface of a substrate, the device having sensing means associated with the device for detecting distortion of the substrate, and means for applying a controlled force to the substrate so as to compensate for the effect of such distortion.

A method of distortion compensation of an optical device disposed on a laminar semiconductor substrate, the method comprising, detecting distortion of the substrate by measurement of an optical parameter of said optical device, and, in response to said distortion detection, applying a force to the substrate so as to negate such distortion.