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A novel time-division-multiplexing fiber Bragg grating (FBG) sensor for multipoint temperature warning sensor is proposed and demonstrated. A multiwavelength pulsed laser based on a multichannel matched FBG is employed. The sensor array consists of multiple uniform FBGs at different positions and with different nominal wavelengths. When the temperature exceeds the threshold at a certain position, the light at the corresponding time slot and wavelength can be detected. The sensor provides a simple and flexible solution to locate the abnormal temperature increase with different tolerable thresholds at different locations. [ABSTRACT FROM PUBLISHER]

A new temperature sensing system, which utilizes a thin-film bandpass filter deposited on an optical fiber end face and dual-wavelength push-pull reflectometry, is proposed. The system has the following advantages over the fiber Bragg grating sensor: it can observe the temperature in a localized small area and it gets rid of microcrack growth caused by stripping of cover coating from a fiber. The feasibility of the system has been verified by simulation. [ABSTRACT FROM PUBLISHER]

In this letter, a demodulation algorithm for fiber Bragg grating (FBG) sensor is presented. The proposed demodulation algorithm evaluates the wavelength shift in the reflected spectrum of an FBG sensor. It computes the cross-correlation between the perturbed spectrum and the undisturbed spectrum. We compare the proposed algorithm with another three reported algorithms and then discuss the experimental results in respect of the reflective index of FBGs and other factors that may influence the sensing resolution. We report strain resolutions of 0.4 and 1.5 muepsiv in high reflective gratings and low reflective gratings, respectively [ABSTRACT FROM PUBLISHER]

A novel fiber Bragg grating (FBG) sensor system for static and dynamic measurements with a wavelength-swept fiber laser is proposed and demonstrated. In this system, both static and dynamic perturbation of each FBG in the sensor arrays can be interrogated simultaneously. The experiments demonstrated the strain resolutions of ∼1 με and 3.4 nε/√Hz at 500 Hz for static and dynamic measurements, respectively. [ABSTRACT FROM PUBLISHER]

A novel fiber Bragg grating (FBG) wavelength demodulation scheme based on a compound interference configuration is introduced. This scheme measures the strain-induced wavelength-shift of the FBG in terms of phase-shift signal. The sensing resolution and sensitivity were demonstrated to be 6.2 nε and 1.59°/με, respectively, which match the theoretical value of 1.61°/με very well. [ABSTRACT FROM PUBLISHER]

In this letter, we describe a very accurate and simple demodulation technique for fiber Bragg grating sensors. The technique is suitable for both single and twin Bragg gratings. A twin grating is composed of two identical gratings located at different positions in the same single-mode fiber. Our demodulation technique evaluates the wavelength position of the reflection spectrum with respect to the spectrum of an undisturbed sensor. To calculate the spectrum shift, it computes the autocorrelation product between the two reflection spectra. The demodulation method, which is very fast, has been tested experimentally with temperature sensors. It gives absolute measurements and provides high accuracy compared to a conventional temperature probe. [ABSTRACT FROM PUBLISHER]

We present, for the first time to our knowledge, experimental evidence showing that superimposed blazed fiber Bragg gratings may be fabricated and used to extend the dynamic range of a grating-based spectrometer. Blazed gratings of 4° and 8° were superimposed in germanosilicate fiber by ultraviolet inscription and used in conjunction with a coated charged-coupled device array to interrogate a wavelength-division-multiplexing sensor array. We show that the system can be used to monitor strain and temperature sensors simultaneously with an employable bandwidth which is extendable to 70 nm. [ABSTRACT FROM PUBLISHER]

We propose and numerically demonstrate a novel technique for estimating the spectral content of the perturbation on a Fiber Bragg grating (FBG) sensor. The system utilizes an FBG array as a wavelength reference for time-stamping the wavelength shift of the sensor. This technique has demonstrated a good agreement between the actual and estimated spectrum. In addition to having the advantage of selecting the operational window of the sensor, it also gives an absolute measurement of the perturbation. [ABSTRACT FROM PUBLISHER]

We propose a novel fiber Bragg grating (FBG) sensor system using a linear-cavity fiber laser scheme with a distributed Raman amplifier as a gain medium. The inhomogeneous broadening property of the distributed Raman amplifier is used for multiwavelength operation. The experiment shows that such a linear-cavity fiber Raman laser can provide a stable output with an optical signal-to-noise ratio over 50 dB even if the FBG is located at a 25-km remote sensing position. The feature of our proposed fiber laser can facilitate a long-distance or a large-scale fiber sensor system and can be easily extended for multipoint sensing applications. [ABSTRACT FROM PUBLISHER]

We report a vertical-pendulum-based fiber Bragg grating tilt sensor, which can detect the magnitude as well as the direction of the inclination from the horizontal direction. The sensor is insensitive to temperature, and preliminary results show that tilt angle accuracy and resolution of better than 0.1° and 0.007° can be easily achieved. [ABSTRACT FROM PUBLISHER]