Ultra-sensitive gas pressure sensor based on vernier effect with controllable amplification factor

We present an optical fiber gas pressure sensor based on two cascaded Fabry-Perot interferometer cavities, one is a section of capillary tube spliced with single mode fiber at its two ends and the other consists of a pair of in-fiber reflection mirrors inscribed by use of femtosecond laser micromachining. The cavity length difference of the two Fabry-Perot interferometers can be precisely controlled to achieve an extremely large sensitivity when vernier effect is utilized. The pressure sensitivity obtained is similar to 303.65 pm/kPa. Moreover, the temperature cross-sensitivity of the device achieved is as low as 0.124 kPa/degrees C. The device is flexible in design, easy in fabrication, convenient in operation and has high potential in medical, environmental monitoring and other industrial applications.