Temperature-independent tilted fiber grating vibration sensor based on cladding-core recoupling.

ABSTRACT

A novel structure in which a short optical fiber stub containing a weakly tilted Bragg grating is spliced to another slightly offset fiber. The total power reflected from this structure is independent of temperature and occurs in two well-defined wavelength bands, only one of which reflects a different amount of power as the fiber stub bends or vibrates. The smart sensing structure presents an extremely high sensitivity for microbending, and its frequency response has been tested to higher than 2 kHz so far in temperature-immune vibration measurements via cost-effective power detection.