Bohnert Klaus, Frank Andreas, Rochat Etienne, Haroud Karim, Brändle Hubert
ABB Switzerland, Ltd., Corporate Research, CH-5405 Baden-Daettwil, Switzerland.
Appl Opt. 2004 Jan 1;43(1):41-8. doi: 10.1364/ao.43.000041.
A polarimetric Fabry-Perot fiber laser sensor for fluid pressure up to 100 MPa is investigated. The fluid acts on one of two elliptical-core fiber sections in the laser cavity, producing a shift in the differential phase of the two orthogonal polarization modes and thus a variation in the beat frequencies of the corresponding longitudinal laser modes. The second fiber section, with a 90 degrees offset in the core orientation, compensates for temperature-induced phase shifts. The dispersion in the birefringent fiber Bragg grating reflectors is employed to remove the near degeneracy of the polarization mode beat frequencies of a given order and to improve substantially the resolution of the sensor to a few parts in 10(6) of the free spectral range. Further investigations address the effect of the fluid on the integrity of the fiber, the influence of various fiber coatings on the sensor response, and the intrinsic stability of erbium-doped and undoped sensing fibers under fluid pressure.
研究了一种用于高达100MPa流体压力的偏振法布里-珀罗光纤激光传感器。流体作用于激光腔中两个椭圆芯光纤段之一，使两个正交偏振模式的差分相位发生偏移，从而使相应纵向激光模式的拍频发生变化。第二个光纤段，其纤芯取向有90度偏移，可补偿温度引起的相移。利用双折射光纤布拉格光栅反射器中的色散来消除给定阶数的偏振模式拍频的近简并性，并将传感器的分辨率大幅提高到自由光谱范围的10^6分之几。进一步的研究涉及流体对光纤完整性的影响、各种光纤涂层对传感器响应的影响以及掺铒和未掺铒传感光纤在流体压力下的固有稳定性。
