Development of an optical fiber flow velocity sensor.
A new optical fiber flow velocity sensor was developed by using an optical fiber information network system in sewer drainage pipes. The optical fiber flow velocity sensor operates without electric power, and the signals from the sensor can be transmitted over a long distance through the telecommunication system in the optical fiber network. Field tests were conducted to check the performance of the sensor in conduits in the pumping station and sewage pond managed by the Tokyo Metropolitan Government. Test results confirmed that the velocity sensor can be used for more than six months without any trouble even in sewer drainage pipes.
Optical in-fibre grating high pressure sensor
A high pressure fibre optic sensor using an in-fibre grating has been constructed. The wavelength of peak reflection from an in-fibre grating is tracked as it is pressurised, and a wavelength shift of 0.22 nm at 70MPa hydraulic pressure has been observed. This sensor is expected to be an attractive choice for ultrahigh-pressure monitoring.
Thermal variation of attenuation for optical fibers
Abstract Thermal variation of attenuation for multi-component and high-silica glass fibers has been measured at 0.63 μm wavelength in a temperature range from 20°C to 600°C. The multicomponent glass fibers have shown no increase in loss below 400°C, whereas the high-silica glass fibers have shown a drastic, exponential increase in loss with increasing temperature. The observed change of attenuation has been explained on the basis of the shift of the ultra-violet absorption band calculated from temperature change of refractive index. The increase in optical loss, calculated from the obtained data of refractive index and dispersion parameters at each temperature, shows good agreement with the observed increase in loss.