We demonstrated a wavelength scanning time division multiplexing of 1000 ultra-weak fiber Bragg gratings (FBG) for distributed temperature sensing. The strong multiplexing capability and low crosstalk of the ultra-weak FBG sensors is investigated through both theoretical analysis and experiment. An automated FBG fabrication system was developed for fast 1000-FBG fabrication. The measurement accuracy of Bragg wavelengths for more than 80% FBGs is less than 20 pm, corresponding to 2 $^{\circ}$ C in temperature.

A Large Serial Time-Division Multiplexed Fiber Bragg Grating Sensor Network

Continuous-wave silica-based erbium-doped fibre lasers

A strain and temperature-sensing scheme based on a dual-wavelength fiber laser is demonstrated experimentally By measuring the change in the wavelength separation of the two lasing wavelengths and the shift of any of two lasing wavelengths, the measured strain and temperature are very linear and have a strain sensitivity of 015 pm/muepsiv over a range of 0-2400 muepsiv and a temperature sensitivity of 143 pm/degC over a range of 22degC-230degC, respectively

A Dual-Wavelength Fiber Laser Sensor System for Measurement of Temperature and Strain

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.

https://ir.nctu.edu.tw:443/bitstream/11536/27082/1/000189020000075.pdf

Long-distance FBG sensor system using a linear-cavity fiber Raman laser scheme

A novel fiber Bragg grating (FBG) sensing system based on a spectrum-limited Fourier domain mode-locking (SL-FDML) fiber laser is proposed. Multiple FBGs cascaded in a long fiber are utilized as both the sensors in the system and the wavelength-selected components in the SL-FDML fiber laser. Both wavelength-division multiplexing and spatial-division multiplexing techniques are demonstrated for interrogation of multiple FBGs by mapping the wavelength measurement to the time measurement and by adjusting the driving frequency of the SL-FDML fiber laser. The proposed FBG sensing system, employing techniques of the wavelength- and spatial-domain interrogation of multiple FBGs, can be used in remote and quasi-distributed multipoint sensing.

Multiple fiber Bragg grating interrogation based on a spectrum-limited Fourier domain mode-locking fiber laser

A wavelength-division-multiplexing technique for interrogating 10-cascaded fiber Bragg grating sensing elements based on a ring-compounded-cavity fiber laser is reported. A feedback control technique was introduced to a tunable Fabry-Perot filter that tracks the wavelength-shift of the sensor. The sensors were demodulated using an unbalanced scanning Michelson interferometer and a sensitivity of 1.682/spl deg///spl mu//spl epsi/ has been demonstrated.

Fiber-laser-based wavelength-division multiplexed fiber Bragg grating sensor system

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 n/spl epsiv/ and 1.59/spl deg///spl mu//spl epsiv/, respectively, which match the theoretical value of 1.61/spl deg///spl mu//spl epsiv/ very well.

Youlong Yu

Papers

Fiber-laser-based wavelength-division multiplexed fiber Bragg grating sensor system

A novel demodulation scheme for fiber Bragg grating sensor system