Tapered fiber Mach-Zehnder interferometers for vibration and elasticity sensing applications

Abstract

We demonstrate the optical measurements of heart-beat pulse rate and also elasticity of a polymeric tube, using a tapered fiber Mach-Zehnder interferometer. This device has two abrupt tapers in the Er/Yb codoped fiber and thus fractional amount of core mode is converted into cladding modes at the first abrupt taper. The core and cladding modes propagate through different optical paths and meet again at the second abrupt taper to produce interferences. The mechanical vibration signals generated by the blood vessels and by an inflated polymeric tube can perturb the optical paths of resonant modes to move around the resonant wavelengths. Thus, the cw laser signal is modulated to become pulses to reflect the heart-beat pulse rate and the elasticity of a polymeric tube, respectively.

Recent Developments in Micro-Structured Fiber Optic Sensors

“…Keeping the central protective jacket also enables large attenuation of the outer-cladding modes, which leaves only a few number of inner-cladding modes propagating along the bend-insensitive fiber and guarantees a more uniform spectral response for the dynamic sensing. Similar work using tapered Er/Yb codoped fiber interferometer has also been published in [49]. Novel short abrupt tapers have been proposed and fabricated with different taper configurations.…”

High extinction-ratio dual thin-taper fiber interferometer fabricated by arc-discharge and its performance as sensors

“…Especially, they have wide applications as fiber filters and sensors [1][2][3][4][5][6][7][8][9][10][11][12]. As we all know, the primary requirement for the fiber filter is its high extinction ratio (ER).…”

“…Generally, the common thin-taper SMF based MI is below 5 dB due to the unoptimized waist diameter of about 65 mm [10]. A high ER thintaper MI can be fabricated on the Er-Yb co-doped fiber (EYDF) with 50-mm waist diameter since the fiber has a high index contrast between the cladding and highly phosphorous doped core [11,12]. In addition, generally, there are two heating techniques for fabricating the dual thin-taper MIs, point flame and discharge.…”

Experimental study of liquid refractive index sensing based on a U-shaped micro-fiber

“…There are mainly two methods to modulate optical signals of the fiber. One is to make micro-structure in the fiber such as Fabry-Perot cavity [6][7][8], fiber Bragg grating (FBG) [9][10][11] and optical fiber interferometer [12,13], with which physical quantity can be measured through the changes of optical signals' intensity, phase and wavelength. Another is to make the optical fiber the fiber carrying evanescent field by corroding or drawing a fiber, such as U-shaped fiber [14,15], D-shaped fiber [16][17][18][19] and taped-fiber.…”

“…The measurement of refractive index has attracted many scholars to develop several methods, such as geometrical optics method [20,21], interference technique [12,13] and the sensitive surface plasmon method emerging in recent years [22]. In this paper, based on an ordinary single mode fiber, a U-shaped fiber with strong evanescent field is designed and fabricated.…”