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We have investigated optical frequency-shift sensitivity of the transmittance channeled spectrum of cascaded-chirped long period fiber gratings (C-CLPGs) to an applied strain from the viewpoint of the sensor use. In the experiment, eight different kinds of C-CLPGs have been fabricated by changing the cascaded distance for two types of CLPGs and the strain-induced spectral shifts are measured by use of a cross-correlation technique which provides highly precise determination of the spectral shift. As a result, it is confirmed that the higher frequency-shift sensitivities of the C-CLPGs to the strain obtain with the higher order of cladding mode.

A novel tunable and switchable Erbium-doped fiber ring laser (EDFRL) is constructed from the viewpoint of sensor applications. The laser consists of a cascaded-chirped long period fiber grating (C-CLPG) and a variable optical attenuator (VOA). The oscillation wavelength is used for sensing a measurand. As a result, wavelength range selecting over about 1557.57 ~ 1570.68 nm with the tuning range within ~5.6 nm is demonstrated, and the sensitivity of ~ −0.22 nm/°C is recorded.