RESUMEN
A slope-assisted Brillouin optical time domain reflectometry system with large dynamic strain range was proposed and demonstrated using graded-index multi-mode fiber (GI-MMF) as sensing fiber. Analysis of the simulated and experimental results indicated that the Brillouin gain spectrum in GI-MMF could be broadened by controlling the coupling efficiency of optical and acoustic modes. The coupling efficiency could be controlled by adjusting lateral offset between single mode fiber (SMF) and GI-MMF. The system realized the maximum strain dynamic measurement of 3000 µÉ with the spatial resolution of 5 m along â¼1 km GI-MMF, and exhibited significant linear relationship between signal intensity and strain at vibrational frequency of 7.83 and 15.47 Hz. The measured error of vibration frequency was less than 0.2 and 1.5 Hz, respectively. The measured strain range of this system was more than three times that of traditional systems based on SMF and could be achieved at relatively low cost.
RESUMEN
An opto-microfluidic static pressure sensor based on a fiber Fabry-Perot Interferometer (FPI) with extended air cavity for enhancing the measuring sensitivity is proposed. The FPI is constructed in a microfluidic channel by the combination of the fixed fiber-end reflection and floating liquid surface reflection faces. A change of the aquatic pressure will cause a drift of the liquid surface and the pressure can be measured by detecting the shift of the FPI spectrum. Sensitivity of the sensor structure can be enhanced significantly by extending the air region of the FPI. The structure is manufactured by using a common single-mode optical fiber, and a silica capillary with the inner wall coated with a hydrophobic film. A sample with 3500 µm air cavity length has demonstrated the pressure sensitivity of about 32.4 µm/kPa, and the temperature cross-sensitivity of about 0.33 kPa/K.
