All
kinds of optical fiber FPI based biosensors have been proposed:
extrinsic FPI [14] with open air cavity for analyte entering provides
relatively high sensitivity, but the cavity is easily contaminated,
lowering its measurement accuracy, and the extrinsic FPI formed
by coating other materials [15,16] is sensitive to temperature;
intrinsic FPI [17] with in-fiber reflecting mirrors is difficult to fabricate;
inline FPI can be realized by femtosecond laser micromachining
[18] or splicing different kinds of fibers, especially the
inline FPI formed by photonic crystal fiber (PCF) and single mode
fiber (SMF) [19,20] has the additional advantages of easy fabrication,
low cost and low temperature cross-sensitivity.