An optical switching module has an optical waveguide substrate mounted on an electronic circuit substrate. According to a first aspect of the invention, the optical waveguide substrate has thin-film heaters, and the electronic circuit substrate has trimmable thick-film resistors for adjusting current...http://www.google.de/patents/US5513285?utm_source=gb-gplus-sharePatent US5513285 - Compact optical switching module including thin-film heaters and trimmed thick-film fixed resistors
