New technique for measuring low fiber-optic attenuation usingdouble square-law detection

A new technique for precision measurement of low fiber-optic attenuation has been developed using double square-law characteristics in a subcarrier lightwave detection system. It magnifies the effect of a small attenuation four times and a 0.01 dB change in optical attenuation produces a 0.04 dB change in electrical attenuation. The present system is capable of measuring attenuation changes less than 0.01 dB with system resolution 0.001 dB