Fiber lasers in optical sensors

Bragg Grating-Based Fiber-Optic Laser Probe for Temperature Sensing

“…Kim [1] has reviewed some of the fiber laser-based sensor devices produced over recent years, but as yet little work has been done on developing optical fiber laser-based systems for temperature sensing; for such measurements, some of the authors have used the fluorescence from rare-earth-doped fiber, especially using the thermal sensitivity of the decay time change [2]. Other relevant work has included a simple wavelength-matched Bragg grating laser cavity approach in rare-earth doped fiber to measure single-point strain and multipoint temperature, showing a linear temperature sensitivity of 0.011 nm/ C [3].…”

A wide temperature tunable fibre laser using a chirped grating and a type IIA fibre Bragg grating

“…where α = 1 ∂ ∂T is the coefficient of the thermal expansion and ξ = 1 neff ∂neff ∂T is the thermo-optic coefficient of the fibre [5].…”

“…Fibre Bragg grating (FBG)-based laser devices have been shown to be important for a range of sensor applications such as in strain measurement, temperature measurement or the simultaneous measurement of strain and temperature [1][2][3] in addition to their wide use in fibre optic communication systems in the wavelength band around 1550 nm [4]. Kim [5] has reviewed published work on such systems and their methodologies and principles for sensor applications, using fibre laser devices. Ball et al [6] have reported a wavelength-matched Bragg grating-based laser approach used to measure single-point strain and multipoint temperature with a linear thermal sensitivity of 0.011 nm • C −1 over a limited temperature range of less than 200 • C. A laser-based temperature sensor probe (using a normal type I grating in Ge-doped fibre) has been developed recently by some of the authors [2], operating from room temperature to 300 • C. An approach by Imai et al [7], using excitation at 1480 nm and creating amplified spontaneous emission (ASE), has also been reported to enable the development of an erbium-based temperature sensor to measure the ratio of the intensities of the fluorescence at two peaks in the spectrum at 1530 nm and 1552 nm, with a reported sensitivity of 0.007 • C −1 , on average, over the temperature range from −50 • C to 90 • C. Fibre laser-based devices offer significant improvement, when compared to passive FBG sensor schemes, through a higher signal-to-noise ratio (SNR) and a narrow linewidth, in addition to their well-known advantages of small size, light weight, immunity to electromagnetic interference, long-term reliability, wavelength-encoded measurement information and a potential multiplexing capability over a single fibre, with the signal amplification occurring in the optical domain rather than in the electronic.…”