We propose a gelatin-coated long period fiber grating humidity sensor which has temperature compensation for low-error humidity detection. The output spectrum shows three resonance dips. The dip caused by gelatin-coated grating has humidity sensitivity of 0.09 nm/%RH and temperature sensitivity of 0.15 nm/°C. Another two dips caused by PDMS-coated grating have almost no response to humidity, which can be used for temperature compensation under low temperature and high temperature range, respectively. We come up with a coefficient matrix and experimentally obtain the humidity and temperature sensitivity of both resonance dips, thus temperature and humidity can be demodulated.
Optical fiber sensor technology is one of the main contents of modern information technology, which has a very important position in modern science and technology. Fiber optic sensor experiment can improve students' enthusiasm and broaden their horizons in college physics experiment. In this paper the main structure and working principle of fiberoptical sensor with intensity compensation model are introduced. And thus fiber-optical sensor with intensity compensation model is applied to measure micro displacement of Young's modulus measurement experiment and metal linear expansion coefficient measurement experiment in the college physics experiment. Results indicate that the measurement accuracy of micro displacement is higher than that of the traditional methods using fiber-optical sensor with intensity compensation model. Meanwhile this measurement method makes the students understand on the optical fiber, sensor and nature of micro displacement measurement method and makes each experiment strengthen relationship and compatibility, which provides a new idea for the reform of experimental teaching.
In this paper, the fabrication of a novel refractive index sensor based on helical long period grating (HLPG) written in a dual-hole elliptical core fiber (DHECF) was demonstrated and the sensing characteristic was experimentally investigated. Due to the structure of the DHECF, The proposed HLPG sensor could work with ultra-small dose testing samples. In addition, since the sample is isolated from the external environment, the testing is immunity to the external interference. The experimental results showed that the testing sensitivity of the sensor was 194nm/RIU with the refractive index range of 1.333 to 1.385. The proposed structure will have a good practicability in the microfluidic sensing system.
We propose a novel single fiber optical tweezers based on a graded-index multimode fiber (GIMMF), whose length is arbitrary (when the length is larger than 5mm). The optical fiber tweezers based on GIMMFs can propagate larger light field intensity and trap particles easily. The optical fiber tweezers based on precise length GIMMF had been achieved. In this paper, the optical fiber tweezers applies the GIMMF with arbitrary length, which ensure the fabrication of the optical tweezers based on the GIMMF simple, convenient and repeatability.
We propose a novel dual-channel Surface Plasmon Resonance (SPR) fiber sensors based on the incident angle adjusting method. By grinding fiber tip to form wedge-shape with different angles, we can easier adjust the incident angle in fiber, and then the SPR wavebands will change corresponding. The simulation and experiment demonstrate that the SPR wavebands will red-shift with increasing of the fiber grinding angle. Based on this, we cascade two fiber tips whose grinding angles are 5° and 15° respectively. Under the tests of the refractive index (RI) range from 1.333 to 1.385, the SPR wavebands are 576~683nm and 677~955nm respectively. Therefore, we can demodulate SPR signal by wavelength division multiplexing (WDM) technology. Sequentially, we can detect two analytes simultaneously. This dual-channel SPR fiber sensor has important significance in the fields of multichannel liquid refractive indices and temperature selfreference measurements.
We propose a novel method to gather or arrange multiple micro particles by using the thermal convection effect in the water. We fabricate the fiber tip to be a nonadiabatic-tapered shape and then plate a gold film on the fiber tip. The gold film coated on the fiber tip absorbs the light output from the fiber and then generate lots of heat in the water, which causes the thermal convection. The convection forces bring the micro particles moving towards the fiber tip where the temperature is much higher. By using this thermal convection effect, we can realize the multiple micro particles gathering or arranging quickly, easily and simply.
A novel hybrid Michelson-FP (M-FP) interference fiber sensor based on a twin-core fiber has been proposed. It consists
of an in-fiber integrated Michelson interferometer and an air FP cavities. The radial strain and axial strain sensing
properties are explored and analyzed. By using this novel structure, we can measure radial strain and axial strain
simultaneously.
We present a method to measure the polarization mode dispersion (PMD) of the LiNbO3 multifunctional integrated waveguide modulator (MFIWM) which is consist of a Y-waveguide, two extended polarization maintaining (PM) fibers, lead-in PM pigtail and lead-out PM pigtail. This method is based on an all-fiber time-domain scanning white light interferometer and utilizes fast Fourier transform (FFT) technology to obtain interferometric phase. The PMD of each part of MFIWM was measured and distinguished accurately. It’s demonstrated that, the PMD of Y-waveguide is 13.5 ps/nm/km@1555nm which is approximately 40~160 times of the PMD of PM fibers in the MFIWM under test.
We propose a calibration scheme of the white light interferometer based optical coherence domain polarimetry (OCDP), which could be used to measure the ultra-weak polarization mode crosstalk (PMC) or the ultra-high polarization extinction ratio (PER) of different polarization optical devices. The calibration depends on the first and second order PMC effect of different polarization devices in series. The first and second PMCs between 0 and -90dB, established by five pieces of polarization maintaining fiber (PMF) and a Y-waveguide, is used to prove its feasibility.
We propose and demonstrate a transverse self-accelerating Bessel-like beam generator based on a graded index multimode optical fiber(GIF). The single-mode fiber and the graded-index multimode fiber are spliced with a defined offset. The offset Δx and the GIF length L affect the final properties of the Bessel-like beam, here we choose the offset Δx=20μm and the GIF length L=430μm to be optimal. The beam accelerates along the designed parabolic path up to 250μm in z direction and 40μm in x direction, the curvature of bending is 16% (40μm/250μm, x/z). This transverse self-accelerating Bessel-like beam generator based on the graded index multimode optical fiber constitutes a new development for high-precision micro particles experiments and manipulations because of its simple structure, high integration and small size.
We propose and demonstrate a novel fiber surface plasmon resonance (SPR) sensor based on a twin-core fiber (TCF). We grind the TCF tip into a frustum wedge shape, and plate a 50nm sensing gold film on the end face, two 500nm reflected gold films on the side faces of the wedge. We launch light source into the core of the TCF by using the high accuracy three-dimensional adjusting mount and microscope objective system. This SPR probe can be combined with microfluidic chip, and realize the real-time monitoring of the refractive index (RI) sensing of flow liquid in the microfluidic channel. The probe successfully monitors the refractive index of liquid ranged from 1.33 to 1.37 and the average sensitivity reaches to 5213nm/RIU in the solution.
We propose and demonstrate a mode division multiplexing single fiber optical tweezers. By using this tweezers, one can trap a yeast cell and then launch it away from the fiber tip with a certain speed to a certain position without moving the optical fiber in a single fiber optical trapping apparatus. We excite both LP01 and LP11 mode beams in a same normal communication fiber core to generate the optical launching force and trapping force by molding the fiber tip into a special tapered-tip shape. A yeast cell of 6μm diameter is trapped and then being launched away. We construct the optical trapping and launching potential wells by controlling the power of two mode beams. This micro particle directional launching function expands new features of fiber optical tweezers based on the normal communication fiber, providing for the possibility of more practical applications in the biomedical research fields.
We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10μm) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.
A method of simultaneous evaluation for two branches of a multi-functional integrated optic chip (MFIOC) with a dual channel system is proposed. The difference between the two branches of the MFIOC can be tested simultaneously with a high precision. In the system, the chip is used as a 1×2 splitter and its two branches are combined by a 2×2 coupler. The characteristic peaks of the two branches are distinguished by selecting proper length of the extended fibers which connected to each polarization-maintaining (PM) pigtails. Temperature responses of the two branches of the MFIOC are experimented. Results show that the dual channel system can simultaneously measure the characteristics of the two branches of MFIOC with resolution of over -85 dB and dynamic range of 85dB.
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