A force sensor has been constructed in which the sensing element is a vibrating metallic glass element under tension. The external force changes the tension along the element, causing its resonance frequency to change. Modulated light guided through a fibre excites the element by photovoltaic conversion and the resonant oscillations are detected by light guided through a second fibre. The system has been calibrated to measure weight, providing a sensitivity better than 0.1 Hz/20 mg and measurement range of 2 kg. The effect of temperature on the operation of the unit has been investigated and suggestions for compensation are made.

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Micromechanical silicon cantilever structures of typical dimensions 1 mm x 80 pm x 5 pm have been excited by absorption of pulsed light from diode laser at 790 nm or a LED at 830 nm respectively. The excitation motion of the cantilevers was measured by means of a fiber -optic Michelson interferometer as well as a reflective multimode fiber optic pick up. In addition to the optical signal the electrical signal of a thin film piezoresistive transducer localized at the base of the cantilever has been measured. The optimal fiber position with respect to the cantilever was determined experimentally. At this position a signal to noise ratio of about 6 could be realized for the detected signal at 5 kHz bandwidth for optical power levels of 56 pW. Using a 125 pm diameter optical fiber this corresponds to an optical power density of 4.6 mW /mm2 which is below the critical value of 5 mW /mm2 suggested for explosive environments.

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