Abstract: A passive method is provided as alignment means for aligning an optical fiber with an optical element in assembling an optical module, while increasing alignment accuracy. A mount (28a) equipped with an optical element (3a) is positioned by abutment on a face (33c) of a projection (33a) formed inside a package (33) and on a side (33g) of a positioning pad (37) projecting from the bottom (33f) of the package. A mount (28b) equipped with an optical element (3b) is positioned by abutment on an inner wall (33b) of the package and on a face (33i) of a projection (33c) formed inside the package. Since the optical power of received or emitted light need not be monitored for fine adjustments of alignment, this method is less expensive.

Abstract: An oxygen sensor for determining the partial pressure of oxygen in a monitored gas environment includes a diffusion housing of zirconia based material having a gas diffusion aperture, an oxygen ion conductive plate of zirconia based material, a pair of electrode layers mounted on opposite sides of the conductive plate, and a sealing glass material sealingly bonding the conductive plate at one side to the housing to provide a diffusion chamber defined by the diffusion housing and the conductive plate. The electrodes are connectable to a power source for being supplied with an electric potential to pump oxygen ion out of the diffusion chamber through the conductive plate to flow a current through the electrodes which current is indicative of the partial pressure of the oxygen in the monitored gas environment. The sealing glass material contains SiO.sub.2, BaO, Na.sub.2 O and ZrO.sub.2.