Photonic bandgap Bragg fiber sensors for bending/displacement detection

Abstract

We demonstrate an amplitude-based bending/displacement sensor that uses a plastic photonic bandgap Bragg fiber with one end coated with a silver layer. The reflection intensity of the Bragg fiber is characterized in response to different displacements (or bending curvatures). We note that the Bragg reflector of the fiber acts as an efficient mode stripper for the wavelengths near the edge of the fiber bandgap, which makes the sensor extremely sensitive to bending or displacements at these wavelengths. Besides, by comparison of the Bragg fiber sensor to a sensor based on a standard multimode fiber with similar outer diameter and length, we find that the Bragg fiber sensor is more sensitive to bending due to the presence of a mode stripper in the form of a multilayer reflector. Experimental results show that the minimum detection limit of the Bragg fiber sensor can be as small as 3 μm for displacement sensing.

Photonic crystal fiber interferometric vector bending sensor

“…To achieve such features, the optical fiber sensor community has proposed a number of sensing architectures. Most of them are based on Bragg gratings [1][2][3][4][5], long-period gratings (LPGs) [6][7][8][9][10][11][12], interferometers [13][14][15][16][17][18][19], or on intensity measurements involving optical fibers [20][21][22][23].…”

“…The disadvantage of some interferometric bending sensors is their complexity as they require several components that must be precisely aligned [16]. On the other hand, bending sensors based on intensity measurements require a mechanism to compensate fluctuations of the light source or attenuation losses [20][21][22][23].…”

Incomplete coupling triple-core photonic crystal fiber sensors for micro-bending angle detection

“…Spectral-based sensors can be implemented by long-period fiber gratings (LPGs) [1], fiber Bragg gratinga (FBGs) [2], etc. Fiber-grating bending sensors have shown many advantages [3]; they are more sensitive and allow multiplexed sensing of a lot of other measurands such as pressure, temperature and strain. However, they also have some drawbacks, for example, the fiber-grating devices are breakable, so that when they are used as sensors, a proper sensor packaging method is necessary; moreover, fiber-grating bending sensors normally require expensive equipment such as an optical spectrum analyzer (OSA) since the bending resolution of fiber-grating-based sensors is limited by the spectrometer resolution [4].…”