Qun Han

Optical fiber magnetic field sensor based on single-mode–multimode–single-mode structure and magnetic fluid

An optical fiber magnetic field sensor based on the single-mode-multimode-single-mode (SMS) structure and magnetic fluid (MF) is proposed and demonstrated. By using a piece of no-core fiber as the multimode waveguide in the SMS structure and MF sealed in a capillary tube as the magnetic sensitive media, which totally immersing the no-core fiber, an all-fiber magnetic sensor was fabricated. Interrogation of the magnetic field strength can be achieved either by measuring the dip wavelength shift of the transmission spectrum or by detecting the transmission loss at a specific wavelength. A demonstration sensor with sensitivities up to 905 pm/mT and 0.748 dB/mT was fabricated and investigated. A theoretical model for the design of the proposed device was developed and numerical simulations were performed.

Magnetic Field Sensor Based on U-Bent Single-Mode Fiber and Magnetic Fluid

In this paper, an all-fiber magnetic field sensor based on a U-bent single-mode fiber and magnetic fluid (MF) is proposed and investigated. Because of the tunable refractive index and absorption coefficient of MF, the transmission spectrum will change with the magnetic field strength (H), which can be used to demodulate H through the wavelength shift or the intensity change. The influence of the diameter of the U shape to the performance of the sensor is investigated and discussed. In the experiments, the highest sensitivities achieved with wavelength and intensity demodulation are 0.374 nm/Oe and -0.4821 dB/Oe, respectively. The reproducibility of the sensor is studied as well.

Numerical characterization of Yb-signal-aided cladding-pumped Er:Yb-codoped fiber amplifiers

In this Letter, high-power cladding-pumped Er:Yb-codoped fiber amplifiers (EYDFAs) coseeded with a Yb-band signal are numerically characterized according to the wavelength and power of the aiding signal, the length of the gain fiber, and the wavelength of the pump. The results show that properly designing these parameters not only helps to suppress the parasitic lasing and improve the pump conversion efficiency but also helps to improve the output power stability of high-power EYDFAs.

A Hybrid Multimode Interference Structure-Based Refractive Index and Temperature Fiber Sensor

A novel all-fiber sensor based on cascaded singlemode-no-core-singlemode (SNS) and siglemode-multimode-singlemode (SMS) fiber structure is proposed and investigated. Simulation results show that for the given fibers, by appropriately choosing the lengths of no-core fiber and multimode fiber, the transmission spectrum will exhibit two distinguishable dips corresponding to SNS and SMS, respectively. The simultaneous measurement of liquids refractive index (RI) and temperature can be realized by monitoring the two dips central wavelength shifts. According to the simulations, a corresponding sensor is fabricated and tested. The experimental results demonstrate the feasibility of the sensor and show that the sensor has the RI and temperature sensitivities of 113.66 nm/RIU and 9.2 pm/°C, respectively.

U-bent single-mode–multimode–single-mode fiber optic magnetic field sensor based on magnetic fluid

A magnetic field sensor based on a U-bent single-mode–multimode–single-mode (SMS) fiber structure and magnetic fluid (MF) is presented and demonstrated experimentally. The U-bent and straight sensors are compared, and the influence of the diameter of the no-core fiber (NCF) on the sensitivity of the U-bent sensor is investigated. The experimental results show that the sensitivity of the sensor can be improved by bending the NCF and decreasing the NCF diameter. The following magnetic field sensitivities have been achieved: 3185.2 pm/mT and 5.6 dB/mT, based on dip wavelength and transmission loss demodulations, respectively.

An All-Fiber Optic Current Sensor Based on Ferrofluids and Multimode Interference

In this paper, an all-fiber optical current sensor based on ferrofluids and a singlemode-multimode-singlemode structure (SMS) with a piece of no-core fiber as the multimode section was proposed and experimentally investigated. The transmittance of the SMS that is sealed in a capillary with ferrofluids is highly sensitive to the surrounding magnetic field. Because the strength of the magnetic field is proportional to the current in the electric line, so the current can be measured. A demonstration sensor was fabricated and experimentally characterized. A sensitivity of 2.12 dB/A was achieved.

Sensor based on macrobent fiber Bragg grating structure for simultaneous measurement of refractive index and temperature.

A novel and compact all-fiber sensor based on a macrobent fiber Bragg grating (FBG) structure for simultaneous measurement of refractive index (RI) and temperature is proposed and experimentally investigated. The sensor can be easily fabricated by properly bending an FBG. The bending causes interference between the core mode and the whispering gallery mode, which induces another kind of dip in the transmission spectra of the sensor besides the sharp one of the FBG. Because the two kinds of dips respond differently to the surrounding RI and temperature, these two parameters can be unambiguously measured by the sensor. A sample sensor was fabricated and experimentally investigated, and RI sensitivity of 165.9276xa0nm/RIU in the range from 1.3330 to 1.3785 and temperature sensitivity of 31.7xa0pm/°C were achieved. This sensor provides a convenient and economical way for applications where temperature and RI have to be simultaneously measured.

Simultaneous Measurement of Refractive Index and Temperature Using a Cascaded FBG/Droplet-Like Fiber Structure

A simple and compact sensor based on a cascaded fiber Bragg grating (FBG)/droplet-like fiber structure is proposed for simultaneous measurement of refractive index (RI) and temperature. The sensor can be easily constructed by mechanically bending a section of coating-stripped single-mode fiber at an FBGs pigtail. In the transmission spectrum, two kinds of dips induced by FBG and droplet-like structure are observed. The central wavelength of the dip caused by droplet-like structure is susceptible to both of surrounding RI and temperature, while that caused by FBG is only dependent on temperature. A sensor with a 9.5-mm diameter of droplet-like structure is fabricated and experimentally studied. The experimental results demonstrate the feasibility of the proposed sensor and show that sensor possesses a high RI sensitivity of 157.8891 nm/RIU for the RI range from 1.3330 to 1.3785 and a temperature sensitivity of 10.3 pm/°C.

Reflective all-fiber current sensor based on magnetic fluids

A reflective all-fiber current sensor based on magnetic fluid (MF) is reported. The MF is used as the cladding of a piece of no-core fiber which is spliced between two sections of singlemode fiber to form a singlemode-multimode-singlemode structure. An intensity based interrogation scheme with a superluminescent diode as the light source and the dual-balanced detection method is used in the sensing system. The influence of the direction of the magnetic field on the sensitivity of the sensor is also experimentally investigated and analyzed.

Magnetic-Fluid-Coated Photonic Crystal Fiber and FBG for Magnetic Field and Temperature Sensing

A novel optical fiber sensor for simultaneous measurement of magnetic field and temperature is proposed and demonstrated. The sensor consists of a cascaded photonic crystal fiber (PCF) interferometer and fiber Bragg grating (FBG). The interferometer and the FBG are sealed in a capillary tube filled with magnetic fluid. The transmission spectrum of the sensor contains both the information of the interferometer and the FBG. The FBG is only sensitive to the temperature but the PCF interferometer is also sensitive to the magnetic field, which in turn can be used for the simultaneous measurement of magnetic field and temperature. A sensor was fabricated and investigated experimentally.