Why is singlemode fibre used for distributed strain sensing?
Singlemode fibre is used for distributed strain sensing due to the nature of the optical components required. Almost all of the components are standard telecommunications components, designed to operate around a wavelength of 1550nm using singlemode fibre. It is very difficult to use multimode fibre as the sensing fibre of the instrument is based on singlemode components, since a lot of light is lost trying to squeeze the light from the large multimode core into the much smaller singlemode core. The backscatter signal used in strain sensing is more powerful than that used for the temperature sensing, hence the relative lower power of using singlemode fibre can be tolerated.
