An in-fiber Fabry-Perot interferometer with fiber Bragg grating mirrors (FBG-FPI) yields extremely narrow transmission peaks within the FBG reflection wavelength range. Periodical scanning of the laser light source is under influence of strain. A high signal-to-noise ratio interrogation is possible with high resolution and a wide range of vibration frequency can be analyzed since the laser wavelength can be easily scanned at high frequency. Furthermore, an inexpensive DFB laser can be utilized as a light source because the narrowness of the transmission peaks does not require broad wavelength scanning. In this paper, experimental investigation of dynamic characteristics of wavelength of DFB-LD is reported.
A Fabry-Perot interferometer with chirped FBGs as reflectors has hundreds of resonance peeks in the transmittance
spectrum and can be utilized as a sensor based on the dependency of the peak wavelengths on the influence applied to
the fiber. Because the width of the peak is narrow and the number of the peak is large, one may well expect high
resolution and/or large dynamic range in its operation. In this paper, we propose to use it for measuring vibration of solid.
We characterize the sensor for two kinds of interrogation methods: the intensity-modulation and wavelength-sweep
schemes. The sensor works well and the former scheme yields a lower minimum detectable strain while the latter gives
flexibility in the magnitude of the dynamic range. In addition, difference in finesse between shorter- and longerwavelength
regions allows us to design a sensor of different sensitivity by changing the operation wavelength.
A novel fiber optic sensor array is proposed and demonstrated by multiplexing intensity-based long-period fiber grating
(LPG) sensors, in which a simultaneous multipoint detection of mechanical vibrations as well as a highly sensitive
operation is realized. In the intensity-based detection scheme, multiple narrowband light sources are provided by use of
a broadband amplified spontaneous emission (ASE) source and fiber Bragg gratings (FBGs) with their wavelengths
adjusted to the spectral dips of the sensing LPGs. The LPG vibration sensor array is achieved by using a combination of
wavelength division multiplexing (WDM) and space division multiplexing (SDM) technique. In the experiment, the
LPG sensor array is constructed by multiplexing two LPG sensors in tandem and simultaneous multipoint vibration
detection without crosstalk is successfully demonstrated.