We verify the relationship between strain response wavelength of strain sensor and force magnitude and force point in practical engineering measurement. Six strain sensors with wavelength intervals of 2 nm were cascaded in a single channel and fixed on the surface of a thermal pipeline with an inner diameter of 50 cm and an outer diameter of 58 cm covered with thermal insulation material. The spacing of the fixed points is 1 m, and the package angle is 30° , 60°, 90°, 330°, 300° , 270° respectively. By changing the position of the external force point and the size of the force, through the theoretical analysis of the mechanical model, good results are obtained. The amplitude of the wavelength response can feedback the magnitude and position of the corresponding force.
A self-mixing chaotic laser which can generate ultra high frequency band is proposed.The system realize the generation of UWB through the modulation of dispersion fiber.The system enters into chaos state under optical feedback and delay feedback (the influence of dispersive fiber).In chaotic state, the Ultra bandwidth is observed on the electrospectrum analyzer by adjusting the length of dispersive fiber.In this paper, two waveforms with unimodal and bimodal are obtained by adjusting the temperature of the phase-shifting grating and adjusting the bias controller.The maximum bandwidth under single peak is 36.78GHz, and the maximum bandwidth under twin peaks is 40.57GHz.By comparison, the bandwidth generated under the bimodal peaks is larger and more complex.The experimental results show that the system bandwidth enlargement effect is very obvious in the case of the selected parameters.The system is suitable for chaotic optical communication and sensing.
A Fabry-Perot cavity with chirped fiber gratings(CFGs) has been proposed and experimental demonstrated We use an ordinary single-mode fiber manufacturing two CFGs with reflection center wavelength 1549.74 nm by ultraviolet irradiation methods of phase mask method, two chirp fiber gratings with the same parameters: the length of the grating region is 10 mm, reflectivity is 95%, and bandwidth is 2.72 nm, chirp rate of 2 nm/cm, 1, 3 and 5 cm of two CFGs spacing. The Fabry-Perot (FP) cavity is composed of two CFGs as reflection faces. When an optical signal is input into the resonant cavity, the wavelength within the bandwidth of the CFGs satisfies the resonance condition, so the resonance is formed within the bandwidth. The structure is analyzed theoretically and the relationship between resonance spectrum and parameters is discussed. Wavelength changes are monitored by a spectral analyzer in real time. The experimental results show that the tunable laser output can be realized in optical communication system by changing the structure and parameters of the resonator.
In this paper, we proposed a new approach to measured humidity by polymer-coated micro-nano Bragg grating. The FBG was written in a 21.85-μm –diameter micro-nano fiber by 244-nm UV laser. Humidity changed the force that acting on the micro-nano fiber, thus the bandwidth of the reflection spectra was introduced and humidity measurement was therefore realized. When the humidity increased, the linearity value was 99 % and the bandwidth changed 0.00312 nm/%. The linearity is 97% and 98% in the stages of humidity reduction in 90 to 65 %RH and 65 to 30 %RH, respectively.
A tunable self-mixing chaotic laser based on high frequency electro-optical modulation is proposed. A laser dynamics system is designed and tested for tunable chaotic laser generation and provides optical feedback and electro-optic modulation with two degrees of freedom. The chaotic laser is generated by optical feedback, and it becomes tunable by high frequency electro-optic modulation. The frequency is modulated from 0 to 6 GHz to test this system, and the spectrum of the chaotic laser is obtained with an electrical spectrum analyzer (ESA). The experimental results show the generation of a wide range of tunable chaotic lasers via electro-optic modulation. At the same time, this tunable chaotic laser has a highly sensitive dynamic response, free regulation, and wide band via adjustments in the feedback intensity and the modulation signal, and this system is proved to be suitable for applications in high-speed broadband communication and sensing.
This paper presents the design, fabrication, and characterization of a D-shaped fiber coated with polyvinyl alcohol (PVA) embedding an Au grating-based relative humidity (RH) sensor. The Au grating is fabricated on a D-shaped fiber to match the wave-vector and excite the surface plasmon, and the PVA is embedded in the Au grating as a sensitive cladding film. The refractive index of PVA changes with the ambient humidity. Measurements in a controlled environment show that the RH sensor can achieve a sensitivity of 5.4 nm per relative humidity unit in the RH range from 0% to 70% RH. Moreover, the surface plasmon resonance can be realized and used for RH sensing at the C band of optical fiber communication instead of the visible light band due to the metallic grating microstructure on the D-shaped fiber.
We propose a simple optical fiber current sensors based on the Lorentz force to measure the current. We use two copper carrying wires, and the two carrying wires are parallel fixed to the insulated coil spring. Then, the two optical fibers are vertically fixed on two copper, respectively. When the current input the wires, Loren magnetic force will be existed between wires. The force causes deformation of the spring and leads to the displacement of the fiber’s end faces. So the spectra should be changed. The experimental device is used to measure the current at range for the 1-5 A, the response time is about 0.1 seconds, and resolution sensitivity of the sensor is 10 nm/A. The results show that the device is simple and low costs. It has a potential applied in high current sensing.
A U-shaped optical fiber sensing system designed to measure the refractive index of liquid had been
proposed. The sensing mechanism of U-shaped optical fiber was discussed. A general single-mode
fiber was bent into U-shaped and partially cladding of U-shaped fiber was corroded by HF acid buffer
solution. Powers of different diameters of U-shaped fibers had been measured by many experiments.
The results showed that the diameter of U-shaped fiber cladding 40 μm and the diameter of U-shaped
was 1 cm were suitable to measure liquid refractive index. Then, this U-shaped optical fiber was
immersed in liquid, such as pure water, ethanol, acetone and isopropanol, respectively. The evanescent
field of the U-shaped fiber should be modulated by the liquid. The optical signal in the U-shaped fiber
was measured with the optical spectrum analyzers(OSA). Finally, the experimental results were
analyzed, and the spectra in the air was selected as a reference. The relative intensity was obtained for
the different liquid. These results showed that the relative intensity of the liquid had a good linear
relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low
cost, and it can also be applied in measuring the level of liquid.
We report the experimental demonstration of colloidal crystal deposited on the end face of fiber, as well as the side
cladding. The colloidal photonic crystals were fabricated through isothermal heating evaporation-induced self-assembly.
The resulted samples were characterized structurally by scanning electronic microscope (SEM) and optically by
transmission spectra analyzer. A moderately transmission dip at 1543 nm and 1546 nm wavelength coincides with the
photonic band gap expected for the 710 nm silica microspheres.
A method of fabricating a colloidal photonic crystal self-assembled onto an optical fiber's cladding is proposed. The coating of a single-mode fiber was removed, the cladding was exposed, and colloidal photonic crystal was overcladding through isothermal heating evaporation-induced self-assembly. The photonic crystal cylindrical annulus is characterized by optical and scanning electron microscopy. The optical characterization was analyzed and carried out followed by detailed discussion. The measurement results show a 1545.5-nm bandgap by optical transmission spectroscopy. The results also demonstrate a practical means of enveloping macro- or microcurved surfaces with three-dimensional photonic crystals.
Used digital speckle correlation method (DSCM) to measure is researched. The experiment is
designed and the laser irradiates a PZT which is driven by some signal to obtain the dynamic speckle
patterns. The dynamic speckle patterns are shot by CCD, then the DSCM is used to process the sequential
images and also the experiment is simulated. The movement of reflection target is controlled by PZT which
is driven by the different model signal. When the reflection target is moving, the dynamic speckle patterns
are shot by CCD, the sequential images are stored in computer through an image board. Then the digital
speckle correlation method is used to process the sequential images. There are three output parameters after
the images correlation calculation: (xi ,yi) and α that represent for position and moving direction of the
object, Initial (xi ,yi) is (0,0). (▵xi , ▵yi) represents pixel difference in coordinates of two adjacent images. α is the angle specifying the direction of the object's motion relative to the x-axis: αε[00,900]. Varying the
speed of the aluminum plate, variant values of (▵xi ,▵i) are obtained and varying the direction of
numeric control caterpillar track, variant values of α were obtained. From the obtained displacement and
the collected frequency, the vibration frequency was obtained. The experimental results show the DSCM
can confirm the frequency and displacement of vibration, and have a good agreement with the simulation
results, and the results show the digital speckle correlation method can be used to measure vibation.
A new method of fabricating three-dimensional colloidal crystals microstuucture fiber is
proposed. The cladding of single-mode fiber was eroded to 60nm by HF and The eroded cladding was
observed by microscopy and scanning electron microscopy. Colloidal photonic crystal was
self-assembled onto the eroded cladding through isothermal heating evaporation induced self-assembly,
and the colloidal photonic crystals cylindrical annulus embeded in fiber was characterized by scanning
electron microscopy. The results shows the colloidal photonic crystals well-orderedly self-assembled
onto the fiber cladding, and the results also demonstrate a practical means of coating macro- or
micro-curved surfaces with three dimensional photonic crystals.
Used digital speckle correlation method (DSCM) to realize orientation function of optical mouse is researched. The experiment is designed to obtain the dynamic speckle patterns which are shot by CCD, Then the DSCM is used to process the sequential images and also the experiment is simulated. The experimental results show the DSCM can confirm orientation function of the optical mouse, and have a good agreement with the simulation results, and the resolution we obtained is higher than the resolution of mouse on the market.
The growing three-dimensional nanostructures colloidal crystal on the end face of optical fiber by isothermal heating
evaporation induced self-assembly method is presented. The wet chemical etching technique is used to etch single mode
fiber to obtain a shallow circular cavity between the coating and cladding. The optical fiber with the etched cavity was
immersed upside into solution containing polymethylmethacrylate (PMMA). The PMMA spheres used here had an
average diameter of 690nm; it takes one week for the sphere particles to completely settle. The nanostructure
morphology of the colloidal crystal is examined by using the SEM. The colloidal crystal has a face-centered-cubic
(FCC) structure. The optical characterization of the colloidal crystal is also analyzed. The simulation and experiment
result show that the colloidal crystal formed by PMMA spheres has an obvious photonic band gap in the wavelength
1543nm that is typical wavelength of optical communication. The spectra feature of the optical fiber colloidal crystal is
measured by using optical sensing analyzer. The experimental results show the band gap at the 1543nm, consistent with
the simulation results.
The method of the three-dimensional nanostructures colloidal crystal growth on the end face of optical fiber by gravity
sedimentation method is presented. The end face of optical fiber is lapped by CNFIBERNET optical lapper. The optical
fiber we used is single mode fiber. We found that the cladding and core of optical fiber would be corroded and the
coating of optical fiber would be reserved when the bare optical fiber is taken into the HF buffer solution (HF:NH4F:H2O=3:7:10), and the cavity would be formed by the coating and cladding. This optical fiber is inserted into
the polymethylmethacrylate(PMMA) microspheres colloidal solution from the lower side, and gravity sedimentation
method is used to grow the PMMA colloidal crystal into the cavity. The three-dimensional nanostructures colloidal
crystal onto the end face of optical fiber can be obtained. The nanostructures is face-centered cubic (FCC) by using the
SEM. The RSOFT is used to simulate photonic band gap of FCC structure. Through the theory analysis and simulation,
the PMMA colloidal crystal formed by the diameter 695nm spheres will have an obvious photonic band gap in the
wavelength at 1550nm.
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