Hao-Jan Sheng

High-sensitivity temperature-independent differential pressure sensor using fiber Bragg gratings.

By means of novel packaged-structure design, a temperature independent differential pressure sensor based on fiber Bragg gratings with high sensitivity is experimentally demonstrated. The differential pressure sensitivity of the sensor can reach to 821.87nm/MPa. This device can also be used for simultaneous measurement of temperature and differential pressure, which is suitable for applications involving measurement of liquid level, liquid density or specific gravity detection.

High-sensitivity simultaneous pressure and temperature sensor using a superstructure fiber grating

In this paper, we show that both pressure and temperature can be measured simultaneously by using a high-sensitivity fiber sensor. This sensor has a superstructure fiber grating (SFG) encapsulated in a polymer-half-filled metal cylinder, which has two openings on opposite sides of the wall of the polymer, to sense the pressure. The sensed pressure is transferred into axial extended-strain. The variation of pressures and temperatures will cause the variation of the center-wavelength and reflection of the SFG simultaneously due to the optical response of the SFG composed by the fiber Bragg grating (FBG) as well as long-period grating (LPG). Thus, the sensor can be used for measuring pressure and temperature simultaneously. It has a pressure sensitivity of 3 times 10-2 MPa-1, better than that using only a bare FBG. Temperature sensitivities in both 0.02 nm per degC and 0.16 dBm per degC have experimentally been obtained. This fiber sensor can be applied for boiler as well as for the underwater depth measurement

An Ultra-Sensitive Liquid-Level Indicator Based on an Etched Chirped-Fiber Bragg Grating

A novel ultra-sensitive liquid-level indicator using an etched chirped fiber Bragg grating is experimentally demonstrated with a sensitivity of 1.214 nm/mm for detecting tens of micro-meter liquid-level variation. The operation mechanism is based on the superposition wavelength-peak shift created by the overlap between the spectrum of the etched CFBG section immersed in the liquid and the spectrum of the rest of the grating in air. This sensor may be used to precisely measure the liquid-level variation in bio-hazardous systems or industrial containers that demand accurate interrogation of the amounts of the contents.

Optical Fiber Sensor Based on Air-Gap Long-Period Fiber Gratings

In this work, we propose a novel fiber sensor that is based on an air-gap long-period fiber grating (AG-LPG), which is fabricated by combining fiber side polishing with fiber lithography. Its sensing mechanism is based on the loss-peak wavelength shift of the AG-LPG as the refractive index around the sensing head varies. Experimental results show that the maximum sensitivity is 620 nm/unit index (1.1 nm/%) in the sensing of various sugar solution concentrations. This novel sensing head provides a simple, reliable, repeatable, accurate, and nondestructive approach for detecting various chemical solutions and mixing gases and for biomedical applications.

Random Rotary Position Sensor Based on Fiber Bragg Gratings

In this paper a new rotary position sensing structure based on a pair of fiber Bragg gratings (FBGs) is experimentally demonstrated with capability of detecting rotating angle of a rotor which is rotated in arbitrary direction or rotated in the same direction infinitely. Moreover, owing to its miniature size, this structure can also be used for small rotary apparatus as a tiny rotating position sensor. The operation mechanism is mainly based on the difference between the wavelength shifts of two FBGs respectively due to the axial strain caused by bending the cantilever towards the angular direction corresponding to the rotating position of rotary shaft. A deviation of 1.1 degrees for rotary angle detecting is obtained.

Acousto-optic-induced cladding-mode reflection in a blazed-superstructure fiber grating

The coupling phenomenon between the cladding mode and the core mode in a blazed-superstructure fiber grating is experimentally demonstrated in this letter by applying both transverse and longitudinal acoustic waves. This is based on the difference between the cladding-mode wave vector and the core-mode wave vector, which is equivalent to the acoustic wave vector. By this means, a reflectivity-tunable multiwavelength switchable comb filter would be developed for the applications in fiber optics.

A refractive-index fiber sensor by using no-core fibers

A simple, small-size, compact and high-sensitivity refractive-index sensor composed of a short no-core fiber (NCF) about 20 mm in length sandwiched between two pieces of single-mode fibers is proposed in this paper. The index measurement is experimentally demonstrated with the sensitivity of 7792.85 nm/ RIU in the range from 1.440 to 1.454 and 227.14 nm/ RIU in the range from 1.300 to 1.430. This sensing mechanism is based on the induced multi-mode interfering wavelength shift in the no-core fiber when the reflective index of the fiber outside is changed.

360

In this letter, a rotation sensor based on a chirped fiber grating for detecting the rotary position with a full 360 ° shaft is proposed. A full circle reading 9.9 nm of wavelength shift for detecting the shafts rotation angle is experimentally demonstrated. The sensor can be used to measure a rotors rotation angle in random directions while continuously rotating in the same direction. The operation mechanism is mainly based on the shift of the reflective wavelength peak of a chirped fiber grating caused by a rolled ball type magnet in accordance with the shafts rotated angle.

^{\circ}

A new rotational angle sensor composed of two FBGs glued axially on a metal-rod surface driven bent by attraction of a magnetic disk is proposed. Whenever an external force is applied in the end of this sensor, these two FBGs undergo a strain caused by a shaft rotation to result in their central wavelength shifts respectively. This sensor can precisely to detect the random rotation angle in both static and dynamic conditions. The nice sensing performance including linear response, fine resolution, negligible hysteresis, and long-term stability are experimentally demonstrated.

Rotation Sensor Using a Chirped Fiber Grating

We have designed an all optical high-sensitivity pressure sensor based on a fiber Bragg grating (FBG) encapsulated in a polymer-half-filled metal cylinder with the sensitivity of 1.87/spl times/10/sup -2/ Mpa/sup -1/. This sensor should be applied potentially for the measurement of mediums pressure, liquid level and depth underwater.