Strain and temperature characterisation of sensing head based on suspended-core fibre in Sagnac interferometer

The study of the strain and temperature characteristics of a sensing head based on a four-hole suspended-core fibre in a Sagnac interferometric configuration is reported. It is shown that, for the case of using an uncoated suspended-core fibre, a relatively large strain sensitivity is obtained (/spl simeq/1.94 pm/μ/spl varepsilon/), while the temperature sensitivity is small (/spl simeq/0.29 pm/°C), pointing to a temperature-independent strain sensor. When the fibre is coated, the strain sensitivity remains essentially the same, while the temperature sensitivity becomes much larger and with a value that changes with the localisation of the temperature variation range.