A manufacturing method for a vacuum measuring cell provides first and second Al.sub.2O.sub.3 ceramic or sapphire housing bodies on opposite sides of an Al.sub.2O.sub.3 ceramic or sapphire membrane sealed to the bodies at its opposite peripheral edges. A reference vacuum chamber and a measuring vacuum chamber are on opposite sides of the membrane. An optical transparent window is provided in the first housing body and an optically reflective material is provided on a central region of the membrane. A lens is above the optical transparent window for optically linking to the optically reflective material on the membrane and an optical fiber outside the reference vacuum chamber and at a distance from the optical transparent window feeds light through the lens and window and in and out onto the optically reflective material on the membrane so that the level of membrane deflection is detected by a Fabry-Perot Interferometer.