At present, the domestic medical puncture robot is still in the research stage. To meet the need of accurate sensing of puncture force in the surgical process, this paper design and manufacture a high-sensitivity optical fiber puncture force sensor with the advantages of small size, high accuracy, anti-electromagnetic interference and good biological compatibility. In this paper, an extrinsic Fabry-Perot sensor is fabricated using the single mode optical fiber and the capillary tube by the method of arc discharge welding. The sensor is encapsulated in a steel needle to make a probe that can measure the puncture force. The calibration for the sensor is carried out. The experimental results show that the sensor has a measuring range of 0-17 N, a sensitivity of 20.66 nm/N, a resolution of 0.01N and a good linearity. The sensor has the advantages of simple manufacturing process and high sensitivity, which makes it have a good application potential in the field of medical puncture robot.
A multi-wavelength erbium-doped fiber laser with switchable output wavelength and tunable wavelength interval is designed and realized. The ring cavity structure is adopted. There are two independent sub-cavities in the ring cavity. One sub-cavity uses FBG-Sagnac ring filter as the frequency selection element, and the other sub-cavity uses fiber Bragg grating (FBG) as the frequency selection element. The performance of the FBG-Sagnac loop filter is analyzed by transmission matrix method and MATLAB simulation, and a dual-path erbium-doped fiber laser is built. At room temperature, by changing the state of optical attenuator and polarization controller, single, double and three wavelength outputs are obtained. In the mode of outputting a wavelength, the laser can realize free switching among the output wavelength of 1550.0 nm, 1550.8 nm and 1551.6 nm. In the mode of dual wavelength output, the output wavelength interval can be switched between 0.8 nm and 1.6 nm. In the mode of outputting three wavelengths, the wavelength interval of the output laser is 0.8 nm, it can be realized to meet the requirements of wavelength division multiplexing. In the stability test, the experimental results show that the laser has good stability.
Owing to the advantages of a wide transparency window (over 20 μm), a high optical nonlinearity (up to a thousand times greater than that of silica fibers), and strong confinement and dispersion engineering achievable, chalcogenide photonic crystal fibers (PCFs) are the best candidates for mid-infrared (mid-IR) supercontinuum generation (SCG). In this review, we introduce the background and the basic theory of the SCG firstly before describing several kinds of fabrication methods of the chalcogenide PCFs. Then, recent progress in the chalcogenide PCFs based mid-IR SCG are present.
We propose an intensity-modulated surface plasmon resonance (SPR) sensor based on a four-layer Kretschmann structural model. To achieve high-sensitivity intensity detection for the measured sample, a silver/gold (Ag/Au) composite film structure is proposed and optimized by a numerical simulation method, and then the chitosan thin film modified by glutaraldehyde cross-linked as an active layer for adsorbing measured sample is applied and immobilized onto the surface of the Ag/Au composite film by spin-coating technique. In addition, a reference beam is introduced into the system to raise its resolution and stability. Measurements are taken while varying the trace copper(II) ion (Cu2 + ) concentration from 0 to 5 ppm, and the SPR sensor is found to possess sensitivities of 0.9147 and 0.4466 ppm − 1 at Cu2 + concentrations of 0 to 3 and 3 to 5 ppm, respectively. The concentration resolution is 0.015 and 0.030 ppm for the trace Cu2 + concentration of 0 to 3 and 3 to 5 ppm, respectively.
We demonstrate a new scheme of cantilever-enhanced photoacoustic spectroscopy, combining a sensitivity-improved fiber-optic cantilever acoustic sensor with a tunable high-power fiber laser, for trace gas detection. The Fabry-Perot interferometer based cantilever acoustic sensor has advantages such as high sensitivity, small size, easy to install and immune to electromagnetic. Tunable erbium-doped fiber ring laser with an erbium-doped fiber amplifier is used as the light source for acoustic excitation. In order to improve the sensitivity for photoacoustic signal detection, a first-order longitudinal resonant photoacoustic cell with the resonant frequency of 1624 Hz and a large size cantilever with the first resonant frequency of 1687 Hz are designed. The size of the cantilever is 2.1 mm×1 mm, and the thickness is 10 μm. With the wavelength modulation spectrum and second-harmonic detection methods, trace ammonia (NH3) has been measured. The gas detection limits (signal-to-noise ratio = 1) near the wavelength of 1522.5 nm is achieved to be 3 ppb.
We demonstrate a high-sensitivity fiber-optic Fabry-Perot acoustic sensor based on a thin Parylene-C diaphragm. The vacuum thermal evaporation deposition method is used to fabricate the Parylene-C nanofilm, which possesses strong adhesion and good compactness. Based on these characteristics, the Parylene-C diaphragm is fabricated with 9 mm in diameter and 500 nm in thickness. The noise limited equivalent acoustic signal level is 33.5 μPa/Hz1/2 at the frequency of 30 Hz. The pressure sensitivities of the acoustic sensor are more than 1000 mV/Pa at the frequency from 10 Hz to 30 Hz. The fundamental resonance frequency of the Parylene-C diaphragm is about 13 Hz. The acoustic sensor is applied in a multiple trace gas detection system based on photoacoustic spectroscopy. The detection limits of acetylene (C2H2), carbon monoxide (CO) and carbon dioxide (CO2) are achieved to be 0.25, 0.32 and 1.1 parts-per-million, respectively.
Optical loss of fiber-optic connectors has a vital impact on fiber-optic-related systems. We analyze the contact loss caused by the endface geometry and the contact force. Based on analytical and simulated results, the analytical equations of the insertion loss (IL) and return loss (RL) as a function of the endface geometry and the contact force are derived. Then four fiber-optic connectors are experimentally tested. The experimental results are well consistent with the theoretical results, which show that there is an optimum relationship between the endface geometry and the contact force to ensure a low IL and a high RL.
We report a high-resolution optical refractometer based on the long-period grating Michelson interferometer. The interferometer phase shift depends on the refractive index that surrounds the fiber probe. A cross-correlation signal-processing method is used to demodulate the interferometer phase shift. Experimental results show that a resolution of 3×10−6 refractive index unit (RIU) can be obtained using this cross-correlation signal processing method. In addition, a measurement sensitivity up to 3×103 deg/RIU is showed as the surrounding refractive index changing from 1.33 to 1.42. Such high-resolution and low-cost optical refractometers would find more applications in chemical or biochemical sensing fields.
We demonstrate a hybrid sensing scheme, combining the incoherent optical frequency domain reflectometry (IOFDR) based Raman distributed temperature sensor (DTS) with the extrinsic Fabry-Perot interferometer (EFPI) based pressure sensor, for down-hole monitoring. The pressure measurement is compensated by a fiber Bragg grating (FBG) based temperature sensor. By using a laser diode as the common light source, a hybrid Raman/EFPI/FBG sensing system has been developed with a single fiber. The stimulated emission light and the spontaneous emission light of the laser diode are used for DTS and EFPI-FBG interrogations respectively. There can be no overlap between the spectral range of the Raman backscattered light and the spectral range of the reflected light from the EFPI-FBG sensor. Distributed temperature and pressure can thus be measured by using wavelength-division multiplexing (WDM) technology. Experimental results show that, both the distributed temperature and the key-point pressure can be measured alternatively with little interference.
As an emerging biosensing technology, Surface Plasmon Resonance (SPR) technique, characterized by high sensitivity, label-free detection and real-time monitoring, has been extensively applied in biochemical analysis, environmental monitoring and refractive index measurement. In this paper, an angle modulated SPR spectrometer with high resolution is designed and manufactured. First, according to the modeling and simulation for the SPR spectrometer, several key parameters such as the light source, the thickness of golden film and Cr film are determined. Then, an angle modulated SPR spectrometer system based on 5-layers Kretchmann prism structure is developed for biochemical analysis. System performance is tested after the SPR spectrometer established. We test the power stability of the laser first, which is up to 1.504% (5min). Different concentrations of glycerol are measured to demarcate the system. Then, we measured the deionized water ten times continuously, and a resolution of 1.5×10-5 RIU is achieved. At last, different concentrations of glucose solution are measured, and the resonance angles are used to calculate the refractive index of the glucose solutions, which is more accurate than the result of Abbe refractometer. The relationship between concentration and refractive index is presented by liner fitting.
The characteristics of a fiber-optic Fabry–Perot interferometric acoustic sensor are investigated. An improved phase-generator carrier-demodulation mechanism is proposed for obtaining a high harmonic suppression ratio and stability of the demodulation results. A gold-coated polyethylene terephthalate membrane is used as the sensing diaphragm. By optimizing the parameters and the demodulation algorithm, the signal-to-noise ratio (SNR) and distortion ratio of 50.3 dB and the total harmonic distortion of 0.1% at 114 dB sound pressure level (SPL) (@ 1 kHz) are achieved, respectively. The sensor shows good temperature stability; the variation of the response is within 0.6 dB as the temperature changes from −10°C to 50°C. A sensitivity of 40 mV/Pa at 1 kHz and a frequency response range of 100 Hz to 12.5 kHz are reached, respectively. The SNR of the system is 60 dB (Re. 94 dB SPL). The sensor may be applied to photoacoustic spectrometers as a high-performance acoustic sensor.
In order to reduce the polarization-induced impact on the incoherent optical frequency domain reflectometry based single-mode fiber-optic distributed temperature sensor, a synchronous polarization scrambling technique with a low-speed electrically driven polarization controller (EPC) is presented. The polarization-induced error is derived by error analysis. By simulating the distribution of the states of polarization on the Poincare sphere, optimized EPC driven parameters are selected. The polarization scrambling process is synchronous with the frequency response measurement of the Raman backscattered light. Additionally, the scrambling period is set to be equal to the measurement time of each frequency response. Experimental results show that the polarization-induced error is ∼±3°C, and it is basically in accord with the result of a theoretical error analysis. By using the synchronous polarization scrambling technique, the polarization-induced fluctuation of the measured temperature distribution has been almost eliminated.
Carbon coatings on optical sensors can protect them from being corroded by H2 and H2O. In this paper, a laserinduced
chemical vapor deposition device is presented to grow carbon films on the fiber Fabry-Perot sensor. The
scanning electron microscopy and Raman spectroscopy are used to analyze hermetic properties of the carbon coating.
Experimental results demonstrated that the carbon-coated sensor exhibited a good long-term stability in a 72MPa and
300°C environment. The fluctuation of the cavity length is only 1nm during seven months after a short-term decrease.
A novel fiber-optic anemometer based on a distributed Bragg reflector (DBR) fiber laser is reported in this paper. We
design a fiber laser pressure sensing setup and a Venturi tube is designed for wind speed measurement. This fiber optic
anemometer overcomes the drawbacks of the existing wind sensors with its unique advantages, such as immunity to
electromagnetic interference, compact structure, remote detection, multiplexing capability. The measuring range of the
anemometer is 8m/s~40m/s, the sensitivity is about 0.3m/s, and the short term repeatability can up to 0.35%.
Experimental results reveal that the sensitivity is impacted by power of pump laser which could be further improved.
This anemometer has high sensitivity and possibility for multiplexing application on a single fiber.
We present a novel fiber optic flow sensor system by using two fiber Bragg gratings (FBGs) and a cantilever beam
structure in this paper. This fiber optic flow sensor uses two FBGs that are bonded on both sides of a cantilever beam
to measure the flow rate by monitoring the FBG wavelength changes caused by the bending of the cantilever beam.
Cross sensitivity of the temperature dependence of the sensor can be compensated automatically. We fabricate the
FBG flow sensor and test it in the laboratory-scaled flow set-up. The testing results demonstrate its high resolution and repeatability for the fluid flow rate measurements. Based on the analysis of test results, the fiber optic flow system will be optimized in the materials of the cantilever beam and the process of sensor fabrication, so as to finally be used in the oil field.
Optical sensors based on nanoparticles induced Localized Surface Plasmon Resonance are more sensitive to real-time
chemical and biological sensing, which have attracted intensive attentions in many fields. In this paper, we establish a
simulation model based on nanoparticles imprinted polymer to increase sensitivity of the LSPR sensor by detecting the
changes of Surface Plasmon Resonance signals. Theoretical analysis and numerical simulation of parameters effects to
absorption peak and light field distribution are highlighted. Two-dimensional simulated color maps show that LSPR lead
to centralization of the light energy around the gold nanoparticles, Transverse Magnetic wave and total reflection become
the important factors to enhance the light field in our simulated structure. Fast Fourier Transfer analysis shows that the
absorption peak of the surface plasmon resonance signal resulted from gold nanoparticles is sharper while its wavelength
is bigger by comparing with silver nanoparticles; a double chain structure make the amplitude of the signals smaller, and
make absorption wavelength longer; the absorption peak of enhancement resulted from nanopore arrays has smaller
wavelength and weaker amplitude in contrast with nanoparticles. These simulation results of the Localized Surface
Plasmon Resonance can be used as an enhanced transduction mechanism for enhancement of sensitivity in recognition
and sensing of target analytes in accordance with different requirements.
Comparing to core-modes of optical fibers, some cladding-modes are more sensitive to the surroundings which are very
valuable to sensing application; recently, a novel type of FBG sensor with core-offset structure attracts more and more
interests. Normally, the forward core-mode is not only reflected and coupled to the backward core mode by the Fiber
Bragg Grating in the step-type photosensitive single mode fiber, but also coupled to the backward cladding-modes and
the radiation modes, eventually they will leak or be absorbed by the high refraction index coating layer. These backward
cladding-modes can also be used for sensing analysis. In this paper, we propose and develop a core-offset structure to
obtain the backward core-mode and backward cladding-modes by using the wavelength shift of the backward core-mode
and the power of the backward cladding-modes in Fiber Bragg Grating sensor, and the power of the backward
cladding-modes are independent from temperature variation. We develop a mode coupling sensor model between the
forward core-mode and the backward cladding-modes, and demonstrate two coupling methods in the core-offset
structure experimentally. The sensor is fabricated and demonstrated for refractive index monitoring. Some specific works
are under investigation now, more analysis and fabrication will be done to improve this cladding-mode based sensor
design for applicable sensing technology.
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