DUAL-WAVELENGTH REFERENCING OF OPTICAL-FIBER SENSORS

Dual wavelength configurations normally employed to eradicate the effects of variable signal losses in intensity-dependent optical sensors are discussed. Particular attention is paid to the referencing capability of each configuration in relation to the major sources of measurement contamination. Illustrative examples of generic type sensor system implementations are provided and assessed to identify areas of any serious shortcomings. It is found that while full referencing can be achieved with both single and dual LED systems the maximum achievable performance will be dependent on the extent of differential spectral effects which can occur because of a finite wavelength separation between the two optical signals.