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A Mach–Zehnder interferometer (MZI) sensor based on a four-core sapphire-derived fiber (FSDF) for bending sensing is proposed and demonstrated. The MZI is formed by splicing a coupled FSDF between two single-mode fibers, delivering supermode interference among four LP01-like supermodes (LP01s modes) and eight LP11-like supermodes (LP11s modes). Benefiting from the different response of the field distribution of each supermode to curvature changes, MZI sensors with a variety of bending properties can be fabricated based on the interference of different supermodes in the FSDF. The experimental results show that the sensitivity of the FSDF-MZI sensor I based on the interference between the LP01s and the LP11s modes is about 4.5 dB/m−1 in the curvature range from 0.4 to 2.5 m−1. The FSDF-MZI sensor II based on the interference of two LP11s modes can realize bending sensing in ± Y directions. The sensitivity of FSDF-MZI sensor II in the curvature range of −10.0–5.0 m−1 is about −24.526 nm/m−1. It suggests that the proposed FSDF-MZI sensor has potential application in the field of structure health detection.

We demonstrate a novel fiber Bragg grating (FBG) temperature sensor based on lead sulfide (PbS)-doped silica optical fiber, prepared by atomic layer deposition (ALD) doping technique. The FBGs are fabricated using the phase mask method, without hydrogen loading. The temperature sensitivity of the FBG-PbS is found to be $\sim$ 19 pm/ $^\circ$ C within 20–150 $^\circ$ C, showing great linearity and repeatability. It is increased by approximately 60% compared to the temperature sensitivity of FBG in standard single mode fiber (SMF). Furthermore, the temperature characteristics of PbS-doped silica optical fiber are investigated. The thermal expansion coefficient and thermal-optic coefficient of PbS-doped silica fiber are 6.3 $\times\; 10^{-7}$ and 1.23 $\times\; 10^{-5}$ / $^\circ$ C, respectively. Moreover, the thermal-optic coefficient value of the PbS-doped silica optical fiber is nearly one order of magnitude higher than that of SMF. Therefore, the FBG based on PbS-doped silica optical fiber appears to be very attractive for the temperature sensing fields.

Optical fiber amplifier is a vital device in optical communication system, which can directly amplify optical signal. We theoretically propose a type of few-mode quantum dots-doped fiber amplifier (FM-QDFA) in this paper, capable of providing amplification for a number of linear polarization (LP) signal mode groups. The main part of the amplifier is a ring-core fiber doped with PbS quantum dots. And refractive index difference between the annular area and cladding is set to 0.035, which weakens the modal coupling between different LP mode groups. The simulation results show that the ring-core optical fiber not only supports transmission for LP(L=0∼6,1) signal mode group, but also provides relatively uniform gain for LP(L=1∼3,1) signal mode group across the wavelength band 1500 nm–1630 nm that covers the C + L band. For these three signal modes, we explore the differential modal gain (DMG) under 11 pump mode groups (LP(L=0∼10,1)). Noticing that the highest gain for LP(1,1) signal mode is approximately 31 dB obtained at the wavelength of 1530 nm and the DMG is less than 0.5 dB with a LP (7,1) pumping mode.

The magneto-optical properties for two kinds of novel doping silica optical fibers, Pb-doped optical fiber and Eu-doped optical fiber, are investigated. A measurement system is set up to analyze the Verdet constants of fiber samples, including Pb-doped optical fiber, Eu-doped optical fiber, single mode optical fiber (SMF) and Er-doped optical fiber (EDF). The system keeps extinction ratio (ER) and power of input linearly polarized light stable. For Pb-doped optical fiber and Eu-doped optical fiber, their Verdet constants are larger than that of SMF at different wavelengths (660, 808, 980, 1310, and 1550 nm), and their Verdet constants are increased with the decreasing of wavelength. Especially, the Verdet constant of Pb-doped optical fiber is 3.08 rad/T/m at 660 nm, which is 27.80% larger than that of SMF (2.41 rad/T/m) at corresponding wavelength. Verdet constant of Eu-doped optical fiber at 660 nm is −4.56 rad/T/m, which is 34.91% larger than that of EDF (−3.38 rad/T/m), and 89.21% larger than that of SMF at corresponding wavelength. Pb-doped silica optical fiber and Eu-doped silica optical fiber exhibit superior magneto-optical properties compared with SMF. Further, the magnetization of fibers are presented in the temperature range of 4–380 K. The magneto-optical property of Pb-doped optical fiber is more stable to temperature than that of EDF.

We have proposed and demonstrated a new refractive index (RI) modulation method based on crystallization in sapphire-derived fibers (SDFs), which are special fibers with a high concentration of alumina in the silica fiber core. Reheating and cooling an SDF with an arc discharge can generate mullite particles in the fiber core. Such crystallization can achieve a maximum RI modulation of ~0.015. Using the point-by-point arc discharge method, crystallization-based long-period gratings (LPGs) can be inscribed in the core of the SDF. Due to the highly modulated RI at the inscribed points, only three to four arc discharge points are required to achieve a strong resonant dip of up to 16 dB in the transmission spectrum of the SDF. The obtained results show that RI modulation by crystallization in SDFs has great potential for the fabrication of functional fiber components that can be applied in high-temperature and -pressure environments.

The influence of the linear birefringence on magneto-optical property measurement for optical fibers is investigated theoretically and experimentally. The evolution of polarization in fibers is simulated by the Jones matrix. To verify this theoretical model, a magneto-optical system is built to measure the input azimuth, output azimuth and ellipticity. The Faraday rotation of spun fibers with different pitches is measured. The Verdet constant increases, while the linear birefringence decreases as the pitch becomes smaller. For spun fibers with 1 mm pitch, the Verdet constant can be enhanced by about 20.7% at 660 nm, compared with that of the unspun fiber. The results indicate that smaller linear birefringence can provide more accurate Faraday rotation measurement.

We have proposed and demonstrated the fabrication of fiber-optic Fabry-Perot interferometer (FPI)-based fiber-optic sensor by 3D printing technology with digital optical processing (DLP) for water pressure sensing application. The mirrors of FPI are provided by the end face of the fiber and the inner surface of the printed resin sensor head. By analyzing the characteristics of the sensor head prepared by 3D printer, the interference contrast is enhanced through the optical fiber end face with an eight degrees angle. The obtained pressure sensitivity is 536.9 nm/MPa. This method of fiber optic pressure sensor has the characteristics of simple manufacturing process, mass production and high sensitivity. Keywords: fiber-optic sensor, 3D printing technique, pressure sensor, Fabry-Perot cavity.

Optical fiber is an important transmission medium in optical communication system. We have designed circular stepindex fiber and circular graded-index fiber for Orbital Angular Momentum (OAM) transmission. And we calculate the existing vector modes in fiber through the software COMSOL Multiphysics. The step-index fiber has a high refractive index ring which doped with PbS quantum dots between the core and the cladding. And the refractive index difference between the ring and the cladding reaches 0.035, which weaken the degeneracy of adjacent eigenmodes. Numerical analyses show the step-index ring core fiber can support the long-distance transmission for the OAM mode of |L|=1,5,6,7 in the wavelength range of 1530nm to 1565nm (|L| refers to the mode order of orbital angular momentum, called topological charge). In order to enhance its stability, we adjust the ring to be a graded refractive index profile, which increases the effective refractive index difference between the vector modes from the same mode order. This fiber design not only increases transmission stability, but also has a better manufacturing process than the step -index fiber. From the simulation results, we can find that the graded-index fiber with a gradation rate α =8 provides a relatively large effective refractive difference. The effective refractive difference is 1.68 × 10 −4 , 1.42 × 10 −4 and 2.44 × 10 −4 respectively corresponding to L=1, 5, and 6 at a wavelength of 1550 nm. While the effective refractive index difference is 1.65 × 10 −4 , 0.9 × 10 −4 and 1.52 × 10 −4 for the step-index optical fiber.

A method of generating the first-order orbital angular momentum (OAM) modes in a single-ring fiber is proposed and demonstrated through an all-fiber structure. The first-order OAM modes (L = ±1) refer to a combination of HE 21 even mode and HE 21 odd mode. According to the donut-like shape distribution of the HE 21 mode, a standard single-mode fiber can be utilized to excite the HE 21 mode in the ring fiber by a lateral-offset splicing. By adjusting the polarization of these two modes, the two first-order OAM modes can be excited separately. Based on this simple structure, the OAM modes can be generated in a broadband wavelength ranging from 1540 to 1580 nm. Moreover, the stable transmission of the generated OAM modes in a 7 m long such ring fiber has been demonstrated.

Silica optical fiber cladding materials were experimentally treated by a series of processes. The treatments involved quenching, irradiation, followed by annealing and subsequent re-irradiation, and they were conducted in order to improve the radiation hardness. The microstructural properties of the treated materials were subsequently investigated. Following the treatment of the optical fiber cladding materials, the results from the electron spin resonance (ESR) analysis demonstrated that there was a significant decrease in the radiation-induced defect structures. The ESR signals became significantly weaker when the samples were annealed at 1000 °C in combination with re-irradiation. In addition, the microstructure changes within the silica optical fiber cladding material were also analyzed using Raman spectroscopy. The experimental results demonstrate that the Si O Si bending vibrations at ω 3 = 800–820 cm −1 and ω 4 = 1000–1200 cm −1 (with longitudinal optical (LO) and transverse optical (TO) splitting bands) were relatively unaffected by the quenching, irradiation, and annealing treatments. In particular, the annealing process resulted in the disappearance of the defect centers; however, the LO and TO modes at the ω 3 and ω 4 bands were relatively unchanged. With the additional support of the ESR test results, we can conclude that the combined treatment processes can significantly enhance the radiation hardness properties of the optical fiber cladding materials.

Two kinds of Nb-doped silica fibers, an NbCl5-doped fiber and an Nb2O5-doped fiber, are fabricated and characterized in this Letter. First, the refractive index profiles of both fibers are obtained, and then their Raman spectra are measured with 785 nm exciting light. The Nb-doped fibers’ Raman spectra are compared with a conventional GeO2-doped single-mode silica fiber that is prepared with the same method and under the same conditions. As a result, the Raman gain coefficients of the Nb-doped silica fiber core are obtained. The experimental results show that Nb2O5 doping can enhance the Raman scattering intensity of the optical fibers.

A Ho-doped silica fiber with a high verdet constant is prepared by a modified chemical vapor deposition (MCVD) method. The phenomenon of the Faraday effect enhancement of a Ho-doped silica fiber is theoretically analyzed by the wave transition contribution analysis method based on the wave-particle duality of light. The Verdet constant of Ho-doped silica fiber is calculated with the wavelength range from 1310 nm to 1550 nm. Through experimental measurement, it is found that the Verdet constant of the Ho-doped silica fiber has a wavelength dependency. The experimental results show that the Verdet constant values of the Ho-doped silica fiber at 1310 nm and 1550 nm are 4.5 times and 1.6 times that of the conventional single-mode silica fiber, respectively.

In this study, the influence of ytterbium ions (Yb3+) on the fluorescence lifetime of erbium (Er)-doped silica optical fiber (EDF) is investigated. An Er/Yb co-doped fiber is fabricated by modified chemical vapor deposition (MCVD), along with the atomic layer deposition (ALD) method. Moreover, the spectral properties of this fiber, such as absorption, luminescence, excitation and emission spectra, and the fluorescence lifetime, are studied experimentally; the results of the experiments are then compared with those of the EDF. The results revealed the existence of a broadband luminescence spectrum at 800-1300 nm. The fluorescence lifetime of the Er/Yb co-doped fiber at 1531 nm is 11.77 ms, whereas that of the EDF is 10.16 ms. The lifetime of Yb3+ is 415 µs, which is 565 µs less than that of the Yb-doped fiber (980 µs), at 1033 nm. Simultaneously, various models of the Er-doped, Yb-doped, and Er/Yb co-doped fibers in three membered ring (3MR) structures were built, and their excited states were analyzed. The results indicated that an energy transfer is associated with the change in lifetime, and that the doping of Yb3+ significantly improves the fluorescence lifetime of Er3+ at 1533 nm.

The luminescence characteristics of PbS semiconductor in silica optical fiber are investigated. The luminescence spectrum covers a bandwith of 1100-1350 nm. And its luminescence intensity is related to pump power and fiber length. In addition, there are obvious absorption peaks at 1022 and 650 nm bands, whose corresponding average sizes and effective band gap are 4.32 nm and 1.21 eV, 2.65 nm and 1.91 eV, respectively.

Effect of the Yb3+ on fluorescence lifetime of Er-doped silica optical fiber was studied in paper. An Er/Yb co-doped fiber is fabricated by MCVD (Modified Chemical Vapor Deposition) with ALD (Atomic Layer Deposition). There exists a broadband luminescence spectrum at 800-1300 nm. The measurement results showed that the fluorescence lifetime of the Er/Yb co-doped fiber at 1533 nm was 11.26 ms, while that of the Er-doped fiber was 9.82 ms. It can be inferred that there is energy transfer in the change of lifetime.

Acupuncture in ST36 is of value for treating a number of diseases, improving immunity, and inducing analgesia. To better understand acupuncture for therapy, the mechanism of acupuncture was explored in this work by analyzing the Raman spectra of the acupoint ST36 using an optical fiber nanoprobe. The experimental results showed that the Raman spectrum of interstitial fluid in acupoint changed at the intensity of peaks, indicating that the component and the concentration of interstitial fluid was some changed by acupuncture. It indicates that Raman spectroscopy with optical fiber is a potential method for the mechanism study of the acupuncture in the future.

The Bi/Al-codoped silica optical fibers are fabricated by atomic layer deposition (ALD) doping technique combing with conventional modified chemical vapor deposition (MCVD) process. Bi2O3 and Al2O3 are induced into silica optical fiber core layer by ALD technique, with Bis (2,2,6,6-tetra-methyl-3,5-heptanedionato) Bismuth(III) (Bi(thd)3) and H2O as Bi and O precursors, and with Al(CH3)3 (TMA) as Al precursor, respectively. The structure features and optical properties of Bi/Al-codoped silica optical fibers are investigated. Bi2O3 stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence state of Bi element is +3. Concentration distribution of Si, Ge and O elements is approximately 24–33, 9 and 66 mol%, respectively, in fiber preform core and cladding layer region. Bi and Al ions have been also slightly doped approximately 150–180 and 350–750 ppm in fiber preform core, respectively. Refractive index difference of the Bi/Al-codoped fiber is approximately 0.58% using optical fiber refractive index profiler analyzer. There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm. The fluorescence peaks are at 1130 and 1145 nm with 489 and 705 nm excitations, respectively. Their fluorescence lifetimes are 701 and 721 μs, respectively. And then there are obvious fluorescence bands in 600–850 and 900–1650 nm with 532 nm pump exciting. There is a maximum fluorescence intensity peak at 1120 nm, and its full wave at half maximum (FWHM) is approximately 180 nm. These may mainly result from the interaction between Bi and Al ions. The Bi/Al-codoped silica optical fibers would be used in high power or broadly tunable laser sources, and optical fiber amplifier in the optical communication fields.

Spun-related effects on optical properties of silica optical fibers have been investigated experimentally. In addition to the previously known spun effects on polarization mode dispersion (PMD), we observed previously unknown spun-related effects on mode field diameter (MFD), cutoff wavelength and Verdet constant. These effects are significant at highly spun (short pitch length) fibers which are draw at high rotation rate and low drawing speed. By fabricating and testing spun fibers of varying pitch lengths, we found that MFD, cutoff wavelength and PMD all decrease as the pitch length decreases, while the fiber loss increases significantly when the pitch length is lower than 1.5 mm. We have also investigated the spun and annealing effects on Verdet constant of spun fibers. Our experimental results reveal that, by increasing the spun rate (i.e., decreasing the spun pitch length), the Verdet constant is increased appreciably. One relevant finding is that the increase of Verdet constant of spun fibers after annealing is inversely proportional to the pitch length. The overall Verdet constant increase, due to spun and annealing processes, can reach about 4.5% at 1550 nm wavelength in a spun fiber with 1.0 mm pitch.

In this paper, we have developed a Raman spectroscopy analytical method for the analysis of tetracycline hydrochloride. Surface enhanced Raman spectroscopy (SERS) was carried out with optical fiber nano-probe coated nanoparticles. Both normal and expired tetracycline hydrochloride were analyzed in direct detection mode and remote detection mode. The results showed that the surface-enhanced Raman spectra could provide chemical information for distinguishing normal drugs from the expired ones. It has been demonstrated that the drug could be analyzed rapidly by SERS with the optical fiber nano-probe.

Fiber-optic magnetic field sensing is an important method of magnetic field monitoring, which is essential for the safety of civil infrastructures, especially for power plant. We theoretically and experimentally demonstrated an optical fiber magnetic field sensor based on a single-mode-multimode-single-mode (SMS) structure immersed into the magnetic fluid (MF). The length of multimode section fiber is determined based on the self-image effect through the simulation. Due to variation characteristics of the refractive index and absorption coefficient of MF under different magnetic fields, an effective method to improve the sensitivity of SMS fiber structure is realized based on the intensity modulation method. This sensor shows a high sensitivity up to 0.097 dB/Oe and a high modulation depth up to 78% in a relatively linear range, for the no-core fiber (NCF) with the diameter of 125 μm and length of 59.8 mm as the multimode section. This optical fiber sensor possesses advantages of low cost, ease of fabrication, high sensitivity, simple structure, and compact size, with great potential applications in measuring the magnetic field.

Mechanical properties of single mode fiber deposited with Al 2 O 3 films by atomic layer deposition technique are investigated. Compared with bare optical fibers, tensile strength of the fibers with Al 2 O 3 film increase evidently.

A novel Pb/Bi co-doped fiber has been fabricated. Its On/off gain without ASE is 12 dB at 1110 nm and 3dB bandwidth is 180 nm by 0.2 m fiber, which indicates it is a promising active material.

Optical properties of PbS-doped silica optical fiber materials and theoretical simulation are investigated. PbS is deposited on silica optical fiber materials by Atomic Layer Deposition (ALD) technique with Pb(tmhd)2 and H2S as Pb and S precursors, respectively. Its stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence states of S and Pb element are −2 and +2, respectively. The Raman spectra further reveal that PbS has been doped into optical fiber materials almost without destroying irregular rings structure in silica material network. And there are distinct absorption bands at 248 and 352 nm. Fluorescence spectra are obtained with 330 and 350 nm pumping, two fluorescence peaks at 768 and 808 nm, respectively. In addition, the microstructure models for PbS-doped optical fiber materials are built on Gaussian09 platform, and its optical properties of the absorption and emission spectra are calculated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. There are obvious absorption and emission peaks at 325.7 and 769.8 nm, respectively, which are in good agreement with experiments.

Optical fiber nanoprobe with gold nanoparticles substrate on the surface was prepared by electrostatic self-assembly technology. Surface-enhanced Raman spectrum of the cells was measured using the optical fiber nanoprobe by remote detection method and direct detection method using confocal Raman micro-spectroscopy. The spectrum were analyzed with the detailed chemical components. The remote detection method using the optical fiber nanoprobe could make the probe inserting into the cells or tissue, and that may be helpful for the online SERS measurement of the cells in the biomedical research and diagnosis in the future.

Fused silica are common fiber materials which have macroscopic central symmetry without second-order nonlinearity. Studies have shown that thermal poling of fused silica fibers can destroy this macroscopic central symmetry, resulting in second-order nonlinearity or linear electro-optical effects. In this paper, a new type of double-hole optical fiber is designed. A two-dimensional (2D) numerical model is used to simulate the movement of ions and the formation of space charge region by finite element analysis. It is found that the single round square hole structure of the new double-hole fiber promotes the thermal poling process. The effective second-order nonlinear coefficient &chi, eff ( 2 ) of the new double-hole poled fiber is 0.28 pm/V at the core center, which is 0.05 pm/V higher than that of the circular double-hole poled fiber. In the fiber core, the radial distribution of the internal electric field and of &chi, eff ( 2 ) is calculated and analyzed. The results of this paper are of great significance for the application of thermally poled fibers on nonlinear all-fiber devices.

A europium-doped (Eu-doped) silica optical fiber is fabricated using modified chemical vapor deposition (MCVD) technology. Europium fluoride (EuFsub3/sub) material is introduced into the fiber core with a high temperature vaporizing technique. Its concentration is approximately 0.11 at %. The outer and core diameters of doped fiber are approximately 122 and 9 μm, respectively. Refractive index difference (RID) between core and cladding is approximately 2%. A magneto-optical effect measurement system, which is based on the Stokes polarization parameters method, is set up to analyze its magneto-optical properties. The Verdet constant of the Eu-doped optical fiber is -4.563 rad Tsup-1/supmsup-1/sup, which is approximately double than that of single mode fiber (SMF) at 660 nm.

A local microstructure model of Er-doped silica fiber is constructed and its absorption spectrum properties are calculated based on DFT and TD-DFT theory. An absorption spectrum of commercial Er-doped silica fiber is also measured.

A Pb/Bi co-doped silica fiber is fabricated by atomic layer deposition (ALD). The absorption bands are at 692 nm, ~800 nm and 1013 nm. There are broadband fluorescence spectra with 980 nm and 830 nm pumping.

Monitoring drug concentrations in vivo is very useful for adjusting a drug dosage during treatment and for drug research. Specifically, cutting-edge "on-line" drug research relies on knowing how drugs are metabolized or how they interact with the blood in real-time. Thus, this study explored performing in vivo Raman measurements of the model drug levofloxacin lactate in the blood using a nanoparticle-coated optical fiber probe (optical fiber nano-probe). The results show that we were able to measure real-time changes in the blood concentration of levofloxacin lactate, suggesting that this technique could be helpful for performing drug analyses and drug monitoring in a clinical setting without repeatedly withdrawing blood from patients.

In this paper, a novel surface-enhanced Raman scattering (SERS) sensor combined with fused biconical taper fiber (FBTF) and film coated with silver sols is proposed. This structure is designed to significantly increase the SERS active surface when the length of the taper is increased and the radius is reduced, since the penetration depth is inversely proportional to the taper radius and proportional to the taper length according to the fiber-optic evanescent-wave theory. Based on the SERS sensing principle, the feasibility of FBTF sensor is analyzed in this paper. As a result, the Raman spectrum of R6G is obtained from the fused biconical taper zone surface coating with the silver sols in our experiments. The detected concentration is up to 10−7mol/L.

Optical properties of tapered optical fiber deposited with PbS are investigated, which is deposited based on atomic layer deposition technique with Pb(tmhd)2 and H2S as Pb and S precursors. After deposition, morphology of PbS thin film is characterized by a scanning electron microscope, and the composition is confirmed by X-ray photoelectron spectroscopy and energy dispersive spectrum. Raman spectrum shows a typical peak at 204 cm − 1, which is assigned to the influence of the PbS structure, and it further reveals that PbS is deposited on the surface of the tapered optical fiber successfully. With a 980-nm pump laser diode, tapered optical fiber deposited with PbS applied to fiber amplifier exhibits a wide band optical gain at 1550 nm with the largest gain of 5.6 dB.

A cerium (Ce) and terbium (Tb) co-doped silica optical fiber (CTDF) is fabricated by the powder-in-tube technique. Its luminescence and energy transfer characteristics are investigated. The experimental results show that a strong excitation peak at 252 nm appears for the Tb-doped fiber materials. Another excitation peak with a similar intensity at 305 nm appears for the CTDF rod. The emission of Tb3+ ions at 542 nm is efficiently excited at 305 nm after Ce3+ ions doping in the silica fiber core. Moreover, the photoluminescence decay of CTDF rod materials at 542 nm is longer than that of Tb-doped fiber materials, from 1709.21 to 2173.17 μs. These results indicate that an obvious energy transfer process from Ce3+ to Tb3+ ions are achieved. Then, an energy level scheme with a local structure model of CTDF is built. Furthermore, numerical simulation results indicate that dipole-dipole interaction is the most-likely energy transfer mechanism. It is significant for the fabrication of Ce/Tb co-doped green emitting fiber lasers and remote fiber-optic radiation dosimeters.

ST36 is a commonly-used acupoint in traditional Chinese medicine (TCM) for treatment of inflammations, pains and gastrointestinal disturbs. For decades, the low power laser acupuncture has been widely applied as an alternative therapy to traditional metal needle acupuncture and achieved relatively fine therapeutic effect for ST36-related symptoms with reduction of uncomfortableness and infection risks. However its disadvantages of low penetrativity and lack of manipulation skills limit its potential performance. An optical fiber laser acupuncture introduced by the previous study combines traditional needling acupuncture and the laser stimulation together, making a stronger therapeutic effect and showing a potential value in clinical application. To evaluate its acupunctural effect on blood, mice are taken as experimental model and Raman spectroscopic technique is used to analysis the changes of blood components after stimulating on ST36. The results show that both the traditional needling acupuncture and optical fiber acupuncture could lead to some spectral changes of blood in mice. This study explores the optical fiber acupuncture's effect on blood in mice using Raman spectroscopy technique for mechanism of acupuncture therapy.

We fabricated a novel special silica optical fiber doped with nano-semiconductor material InP in double cladding layers by using conventional modified chemical vapor deposition (MCVD) process. During the deposition process, InP powder was placed at the entrance of silica substrate tube and vaporized by high temperature. With the help of nitrogen gas flow, the vaporized InP was carried into silica substrate tube and deposited on the inner surface in the form of nano-particle. The physical structure and amplification characteristics of the special fiber were investigated. From the refractive index distribution of the preform, we can observe obvious increase in inner cladding index, which attributes to InP dopant. By using 532 nm LD as pump, a broadband amplified spontaneous emission (ASE) was demonstrated in the wavelength range from 1,080 to 1,350 nm. The proposed nano- semiconductor doped fiber with optical amplification is expected to a wide application in optical fiber communications.

A Bi/Er co-doped fiber is fabricated by ALD. Absorption bands at 500, 700, 800, and 1000 nm are broadened due to Bi/Er co-doping. There exist broadband luminescence and on-off gain spectra with 980 nm pumping.

The Laser drawing process of germanium core optical fiber is studied numerically and experimentally in this paper. We analysed the changes in the maximum temperature, maximum velocity and surface profile over time. The final profile of dynamic simulation is in good agreement with the experimental result.

We have demonstrated a novel approach to construct a cascaded Mach-Zehnder interferometer (MZI) based on local crystallization of sapphire-derived fiber (SDF). When the SDF is spliced to standard single mode fibers, the crystallization of SDF occurs near the spliced points. Such crystallized points in SDF could excite and recombine two core modes, which leads to an in-fiber MZI. Moreover, by applying an arc discharge to the SDF, the crystallization could create a cascaded MZI with a temperature-insensitive feature, showing great potential in industrial sensing applications where the required sensors can endure high temperature as well as exhibit low cross-sensitivity from temperature.

Hypoxia is a disorder in which the tissues are not oxygenated adequately. The lack of oxygen may cause irreversible damage to the major organs such as the brain, heart and lungs. In severe cases, coma, seizures, and death may happen. In addition to the routine medication, acupuncture treatment has been applied as a complementary treatment to counter hypoxia. In this paper, the optical fiber acupuncture needle was fabricated using the optical fiber imbedding into the metal capillary tube with needle tip, therefore made it easy to insert into the body for the laser treatment. The laser optical fiber needle treatment to the ST36 acupoint conducted with the laser irradiation intra body. The normobaric hypoxia tolerance test results in mice show that the optical fiber needle treatment to the ST36 acupoint with laser acupuncture appears to improve the tolerance to hypoxia. The mice treated with laser acupuncture expressed high level of IL-1[Formula: see text] in serum. Our results suggest that laser optical fiber needle acupuncture may serve as a potential treatment for hypoxia.

A Ce-doped silica fiber material is prepared using powder-in-tube technique via sol-gel method. Its absorption and emission spectra are investigated from experimental and theoretical perspectives. The experimental results show an absorption band at 320 nm and a broad emission band at 430 nm, which comprises of two bands at 420 and 470 nm, respectively. In addition, a local microstructure model of the Ce-doped silica fiber material is developed and its structure parameters and fluorescence spectra are calculated using density functional theory. The theoretical results indicate a strong absorption peak at 336 nm and an emission peak at 486 nm. Furthermore, the spontaneous emission lifetime is also calculated to be approximately 64.82 ns. This confirms theoretically that the Ce-doped silica materials possess the scintillator characteristics. Moreover, an energy level diagram for the Ce-doped silica fiber material is constructed. It is significant for understanding the fluorescence properties of the Ce-doped silica fiber material at the microstructural level.

The Raman scattering enhancement characteristic of LaCl 3 and LaF 3 -doped silica fiber were researched. The experimental results show that doping can enhance the optical fiber Raman scattering intensity, and have a good Raman scattering enhancement effect.

Remote optical fiber sensors for radiation measurement are very useful in high radiation fields. In this paper, we fabricated scintillating optical fiber by using a cerium-doped silica rod. In the drawing process, we obtained different fiber samples by changing the drawing temperature and speed. The drawing temperature is from 1900 to 2200 °C and the speed is from 1 to 10 m/min. The experimental results showed that the optical rod physical properties such as viscosity, tension and scintillating efficiency can be controlled by the parameters of temperature and speed. The optical properties and chemical composition of the scintillating optical fiber have been analyzed by Raman spectra and X-ray fluorescence spectrometer (XRF-1800, SHIMADZU). The concentration of the doped cerium is 0.55%. Moreover, a test system is proposed to measure the scintillating performance of the fabricated optical fibers. For the scintillating properties, the effect of fiber length, the number of fiber bundle and the detection angle were analyzed. Experimental results showed that the optimal length of the cerium doped fiber is ~15 cm. The scintillating light intensity increases linearly with the number of the fiber bundle. With two low intensity 60Co (0.2784 μCi) and 137Cs (1.0865 μCi) gamma radiation sources, the scintillating light can be detected the gamma sources by using the scintillating fiber sensor which is connected a MMF.

We fabricated a silica optical fiber doped with InP sandwiched in the core and the inner cladding layers by using the conventional modified chemical vapor deposition process. We presented the experimental X-ray analysis on the optical properties and found that compound InP was contained in the fiber core after annealing process. Broadband photoluminescence observed in InP doped fiber was well coincided with those coming from the recombination of deep levels in InP. The occurrence of temperature-dependent photoluminescence both at the lower and room temperature would be related with the localized defects and their confinement in the micro-network structure of Si–O–Si. The Raman spectra reveal that Si–O–In vibration would disorder the silica ring structures and enervate their vibrations.

We fabricated Bi-doped silica fiber by atomic layer deposition doping technique. The refractive index difference of fiber is 0.58 %. The absorption peak is at 500 nm, 700 nm, 800 nm, and 1000 nm. The fluorescence peak is 1130 nm.

A miniature(Φ300μm) fiber optic EFPI pressure sensor using SU-8 photoresist is fabricated. Both pressure and temperature characteristics have been studied, and it shows a good linearity within 100~700Pa with a sensitivity of 0.765nm/kPa.

The optical properties of (PbS)n clusters (n=1-9) were studied theoretically. PbS was prepared on silica fiber materials by atomic layer deposition (ALD) technique. Theoretical calculations on absorption spectra were basically agreed with the experimental results.

A new technique of atomic layer deposition (ALD) has been the first introduced to fabricate PbS-doped silica fiber, whose optical properties are measured. The fiber exhibits photoluminescence property in the wavelength range 1100–1185 nm.

Recently, specialty fibers with various functional material doping have attracted significant attention. In this paper, we fabricated Nb-doped silica fiber and measured its resonant optical nonlinearity with long-period fiber gratings (LPFG) interferometer. The Nb-doped fiber was made with a combined MCVD and ALD technology. Then, we fabricated a pair of LPFGs and cascaded them as a Mach-Zehnder interferometer (MZI).By measuring the wavelength shifts of the interference fringe with the 532nm laser pump power, the resonant nonlinear refractive index of Nb-doped silica fiber around 1537 nm was estimated to be 8.12×10 -16 m 2 /W.