A power-interrogated sensor which allows for simultaneous measurement of temperature and torsion is proposed and experimentally demonstrated, which is based on utilization of paired helical long-period fiber gratings (HLPG) with opposite helicities. Unlike most of the previous fiber grating-based sensing system, here the paired HLPGs are simultaneously used as both the sensing and the interrogating elements and thus the bulk and high-cost wavelength-interrogating device can be eliminated. Moreover not only the torsion but also the torsion direction can be determined simultaneously. The temperature sensitivity obtained is estimated to be ~41 pm/°C within a range of 20-150 °C, and the torsion responsivities obtained are ~-1.414 nm/rad/m and ~1.276 nm/rad/m, respectively within a rotation angle of -360°~360°.

A long-cavity single-longitudinal-mode (SLM) Brillouin fiber laser is firstly demonstrated by utilizing an unpumped Erbium-doped fiber (EDF) loop. The utilized EDF enables to form a self-induced ultra-narrow grating filter, and thus guarantees the SLM operation.

Several kinds of phase-shifted long-period gratings (LPGs) have been fabricated using a high-repetitionrate CO 2 laser, where both the grating and the inserted phase shift are simultaneously produced in a commonly used single-mode fiber. Furthermore, using one of the fabricated phase-shifted LPGs, a temperature-insensitive sensor that allows for large axial strain measurement with a value up to 7600 με, is proposed and first demonstrated. Measurement accuracy for the strain ranging from 340 to 7600 με is estimated to be ±30 με, while the temperature is changed in a range of 20°C-140°C.

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