Loss-Modulation-Based Wavelength-Range Shifting of Tunable EDF Ring Laser with Cascaded-Chirped Long-Period Fiber Grating for Temperature Measurement.

A novel tunable Erbium-doped fiber ring laser (EDFRL) with a cascaded-chirped long-period fiber grating (C-CLPG) as a wavelength selection filter is proposed from the viewpoint of the sensor use, in which a variable optical attenuator (VOA) is employed as an intracavity loss modulator to change the oscillation wavelength region so that the resultant tuning wavelength range is widened. In the demonstrative experiment for temperature measurements, oscillation over the wavelength range of 12.85 nm (1557.62~1570.47 nm), which is more than three times range of the previously presented laser and is equivalent to 64 °C in terms of temperature change, was achieved, while a single-wavelength oscillation was maintained. In addition, a practical technique for realizing a temperature measurement by combining with the VOA control is also discussed.

EDF ring laser using cascaded-chirped long period fiber grating for temperature measurement.

A novel tunable erbium-doped fiber ring laser (EDFRL) using a cascaded-chirped long period fiber grating (C-CLPG) as a wavelength selection element is proposed. The oscillation wavelength is determined by the one of the spectral peaks of the C-CLPG used, and the oscillation output provides a high signal to noise (S/N) ratio detection and a highly sensitive measurement of the temperature due to its high power and narrow spectral output. In the experiment, it is confirmed that the wavelength of the output shifts in accordance with the temperature-induced spectral shift of the C-CLPG transmittance spectrum and the temperature sensitivity is obtained to be ∼-0.2 nm/°C within the wavelength range of 1567.30 ∼ 1575.78 nm. The oscillation wavelength range is to be limited depending on the fringe spacing of the channeled spectrum of C-CLPG, which limits the temperature measurement range, but a data processing approach to solve this problem is additionally proposed and its availability is also presented.

Simultaneous multi-point measurement of strain and temperature utilizing Fabry-Perot interferometric sensors composed of low reflective fiber Bragg gratings in a polarization-maintaining fiber.

A fiber Bragg grating (FBG)-based multi-point sensing system for the simultaneous measurement of strain and temperature is proposed, with a Fabry-Perot interferometer (FPI) consisting of low reflective FBGs inscribed inside a polarization-maintaining (PM) fiber is introduced as a sensor head. A multi-point sensing method with high dynamic range and short measurement time can be realized by analyzing the reflection spectrum of low reflective FBG-FPIs, and a simultaneous measurement of strain and temperature using two orthogonal polarization modes is enabled by the high birefringence of a PM fiber. An experimental demonstration of multi-point measurement utilizing the proposed system is reported.