Strain and Temperature Characteristics of Cascaded-Chirped Long Period Fiber Gratings Depending on Order of Cladding Mode

Abstract

In this paper we have investigated optical frequency-shift sensitivities of the transmittance channeled spectra of cascaded-chirped long period fiber gratings (C-CLPGs) to the applied strain and temperature change from the viewpoint of the sensor use. In the experiment, several kinds of C-CLPGs have been fabricated by changing the cascaded distance between CLPGs and the strain- or temperature-induced spectral shifts for three different order of the cladding modes are measured simultaneously by use of a cross-correlation technique which provides highly precise determination of the spectral shift. As a result, it is confirmed that the frequency-shift sensitivities of the C-CLPGs to the strain and temperature are larger with the higher order of cladding mode, while the dependences for the temperature sensitivity is much less than that for the strain. In addition, the dependences for the cascaded distance are also investigated.

EDF laser displacement sensor based on bending characteristics of polarization-independent double-pass cascaded-chirped long-period fiber grating

“…In our laboratory, we have fabricated a cascadedchirped long-period fiber grating (C-CLPG), a development of the LPG, and proposed its sensor applications [11,12]. The C-CLPG is fabricated by inscribing two chirped LPGs (CLPGs) spaced at a certain distance from each other.…”

EDF sigma laser using double-pass cascaded-chirped long-period fiber grating with birefringence compensation effect and its application for strain measurement

“…In our laboratory, we have proposed the sensor applications of C-LPG and its further development, cascaded-chirped LPG (C-CLPG) which extends the wavelength range of the channeled spectrum by chirping in the grating period. We have reported a method based on the Fourier transform that utilizes the periodicity of the channeled spectrum, which enables highly precise measurement of strain and temperature, as well as multipoint and simultaneous measurement [8,9,11]. However, the method uses an incoherent broadband light source, so the output signal is a low signal-to-noise ratio; moreover, it requires the time-consuming acquisition of channeled spectrum and data processing.…”