Mechanically induced long-period fiber grating in side-hole single-mode fiber for temperature and refractive sensing

Sensing Characteristics of Side-Hole Fiber-Based Long-Period Grating

“…Fiber gratings, with a periodic refractive index (RI) distribution in the axial direction of the fiber, are widely applied in fiber sensing and optical communication due to their many advantages such as simple structure, high sensitivity, wellcontrolled wavelength-selective capability, and capability of remote interrogation of multiple sensors [9][10][11][12][13][14]. SHF-based fiber grating devices have attracted lots of research interest [11][12][13]. Simultaneous measurement of strain and temperature has been reported by using a fiber Bragg grating (FBG) recorded on the fusion splicing joint between an SHF and a single-mode fiber (SMF) [11].…”

“…Simultaneously measurement of pressure and temperature has also been realized by using an FBG imprinted on the SHF with an elliptical core [12]. In our previous study, a long-period grating (LPG) has been introduced mechanically in an SHF and been applied to temperature and RI measurements [13]. However, it is not convenient in practical applications because the mechanical part cannot be removed.…”

Refractive index sensing by a periodical pressure on a single-mode fiber

“…For the surrounding refractive index sensing, the periodical pressure induced LPFG can not be directly placed in the surrounding medium because of the pressure setup. Instead, a side-hole single-mode fiber is applied, where the medium is injected into the holes [7] . In the scheme, specially-designed side-hole fiber is required, which is inconvenient to connect to a standard single-mode fiber.…”

Mechanically induced long period gratings in ZBLAN fibers

“…Due to their unique spectral filtering properties, long period gratings (LPGs) are now common place in telecommunication and sensing applications [5][6][7]. In a LPG, the core mode is coupled to forward-propagating cladding modes for wavelengths λ m that satisfy λ m = Λ (n core -n cl m ), where Λ is the grating period, and n core and n cl m are the effective indices of the fundamental guided mode and m-th order cladding mode respectively [8].…”