A Highly Sensitive Intensity-Modulated Optical Fiber Magnetic Field Sensor Based on the Magnetic Fluid and Multimode Interference

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

Synthesis and photovoltaic effect study for fullerene complexe C60Pd(Ph2PCH2PPh2)

Fulerene complexe C-60 Pd (Ph2PCH2PPh2) was perpared by the method of ligand substitution via the reaction of C-60 with Pd(Ph2PCH2PPh2)(2) under condition of a nitrogen atmosphere and refluxing, and the title compound was appraised and characterized by methods of elemental analysis, FT-IR, UV-vis, XPS and XRD. The results showed that the structure of purposeful product was that the Ph2PCH2PPh2 took up two coordination sites of the central metal, and C-60 took up another two sites in sigma-pi feeback pattern. The porperties on photoelectricity, redox and thermostability of the tide complexe were studied. The results of studying on photoclectricity showed that the photovoltaic effect of (n + n) heterojunction electrode formed by C60Pd(Ph2PCH2PPh2)/GaAs was supper, especially in the BQ/H(2)Q redox couple, and the greatest value of photovoltaic potential was up to 174 mV. The photovoltaic performance of C60Pd (Ph2PCH2PPh2)/GaAs electrode at 1 mum for thickness of C60Pd(Ph2PCH2PPh2) film was the best

Composition and strain analysis of Si1-xGex core fiber with Raman spectroscopy

The fabrication and characterization of Si1-xGex core fiber have attracted much attention because of its great application potential in new optoelectronic devices. In this work, by assembling two semi-cylindrical monocrystalline Si and Ge rods into a silica tube, we present a fabrication method to draw Si1-xGex core silica clad fiber with graphite furnace. Raman spectra analysis reveals that in all regions of the core formed the Si1-xGex alloy. The optical microscopic photograph shows that in the core of a diameter of 36 μm distributed the bright and dark regions, where it was further proved by Raman spectroscopy that the bright regions are Ge-rich areas and the dark regions are rich in silicon. By recording the Raman spectra of consecutive regions, it was found that with the increase of Ge content (x<0.5) the peak intensity of Si-Ge mode obviously increases, similar to the intensity of Ge-Ge mode, while the peak intensity of Si-Si mode decreases. Then we made a quantitative analysis of the components and strain by mapping the Raman spectra of the fiber core. The experimental results show that the Ge content mainly distributes between 0.1 and 0.8, concentrating between 0.2 and 0.3, and the strain distribution on the surface is obtained at the same time

Monitoring Junction Temperature of RF MOSFET under Its Working Condition Using Fiber Bragg Grating

When a high-power radio frequency (RF) metal oxide semiconductor field effect transistor (MOSFET) works in low-efficiency situations, considerable power is dissipated into heat, resulting in an excessive junction temperature and a likely failure. In this study, an optical fiber Bragg grating (FBG) sensor is installed on the die of a high-power RF MOSFET. The temperature change of RF MOSFET with the change of input signal is obtained by using the temperature frequency shift characteristic of the FBG reflected signal. Furthermore, the fast and repetitive capture of junction temperature by FBG reveals details of the temperature variation within each RF pulse, which is correctly correlated with input signals. The results show that besides monitoring the temperature accumulation of the chip for a long time, the FBG can also capture junction temperature details of the chip within each pulse period. Finally, a Cauer-type thermal model of the RF MOSFET was constructed based on the temperature information captured by the FBG

Ultraviolet Irradiation Effects on luminescent Centres in Bismuth-Doped and Bismuth-Erbium Co-Doped Optical Fibers via Atomic Layer Deposition

The effects of ultraviolet irradiation on luminescent centres in bismuth-doped (BDF) and bismuth/erbium co-doped (BEDF) optical fibers were examined in this study. The fibers were fabricated by modified chemical vapor deposition combining with atomic layer deposition method. The fibers were exposed to irradiation from a 193 nm pulsed wave argon fluoride laser, and an 830 nm wavelength laser diode pump source was employed for excitation. The experimental results showed that, for the BDF, the transmission loss was slightly reduced and the luminescence intensity was increased at the bismuth-related active aluminum centre (BAC-Al). Then, for the BEDF, the transmission loss was increased a little and the luminescence intensity was also increased at the BAC-Al centre. However, the luminescence intensity was decreased at approximately 1420 nm of the bismuth-related active silica centre (BAC-Si) for all fiber samples. One possible formation mechanism for luminescence intensity changes was probably associated with the valence state transfer of bismuth ions. The other possible mechanism was that the ArF-driven two-photon process caused luminescence changes in BAC-Al and BAC-Si. It was very important to reveal nature of luminescence properties of Bi-doped and Bi/Er co-doped optical fiber

Influence of Temperature on All-Silica Fabry-P&#x00E9;rot Pressure Sensor

An all-silica Fabry-P&#x00E9;rot interferometer (FPI) is demonstrated for high-temperature pressure monitoring. The pressure sensor is fabricated with single mode fiber and silica capillary by CO2 laser. Owing to slight mismatch of thermal expansion coefficient in all-silica structure, it can work stably under 600&#x00B0;C atmosphere. The influence of the temperature on the pressure sensor was investigated within a temperature range from 25&#x00B0;C to 700&#x00B0;C and a pressure range from standard atmosphere pressure to 4 MPa. The experimental results show that the wavelength shift versus the pressure at each temperature is linear, which indicates the proposed FPI pressure sensor has potential applications in industrial reactors, oil and gas wells, and so on

Generation, Transmission, and Amplification of OAM Modes in the PbSe-Doped Ring-Core Fiber Carrying 3D Printed Spiral Phase Plate

Vortex beams carrying orbital angular momentum (OAM) have increasingly attracted attention in the field of optical communication. However, transmission is still an issue due to transmission loss, especially in optical fibers. In this work, we proposed, designed, and fabricated micro spiral phase plates (SPPs) directly on an end facet of a piece of PbSe-doped ring-core fiber (RCF) through two-photon polymerization, realizing the integration of OAM beam generation, transmission, and amplification. The prepared RCF comprises a double-clad structure with a core-clad refractive index difference of 2.2% and the fluorescence range is 1150 nm–1700 nm. The intensity distribution of the OAM beam and the spiral interference fringes were obtained, which indicated that the OAM mode (|l|=1, 2, 3, 4) was generated and transmitted directly within the fiber. The small-signal amplification of four OAM modes was accomplished at 1550 nm under a pump power of 634 mW. The on–off gain is >13.2 dB for all modes and the differential mode gain (DMG) is <1.7 dB. The SPP-carrying RCF structure demonstrates the integration of generation, transmission, and amplification of higher-order OAM modes in all-fiber systems