Chi Chiu Chan

Magneto-optical fiber sensor based on magnetic fluid

A novel tilted fiber Bragg grating (TFBG)-based magnetic field sensor by incorporating magnetic fluid is proposed and experimentally demonstrated. It is based on the refractive index change of magnetic fluid with external magnetic field. Magnetic field strength measurement is successfully achieved within a range from 0 to 196 Gauss by monitoring extinction ratio of the TFBGs cladding mode resonance, which is sensitive to surrounding refractive index.

Magneto-optical fiber sensor based on bandgap effect of photonic crystal fiber infiltrated with magnetic fluid

A magnetic field sensor based on combination of the magnetic fluid and the tunable photonic bandgap effect of photonic crystal fiber is proposed. The magnetic fluid with higher refractive index (>1.45) is prepared and filled into the air-holes of photonic crystal fiber to convert the index guiding fiber into photonic bandgap fiber. The proposed sensor takes full advantage of the ultrahigh sensitivity characteristic of photonic bandgap fiber and achieves a high sensitivity and resolution of 1.56 nm/Oe and 0.0064 Oe, respectively, which are 2-3 orders of magnitude better than other sensors based on magnetic fluid.

Temperature-Insensitive Magnetic Field Sensor Based on Nanoparticle Magnetic Fluid and Photonic Crystal Fiber

A novel magnetic field sensor based on the magnetic fluid and Mach-Zehnder interferometer is proposed. The sensor takes advantage of the tunable refractive index property of the magnetic fluid and the modal interference property of the collapsed photonic crystal fiber. The achieved sensitivity and resolution of the sensor are 2.367 pm/Oe and 4.22 Oe, respectively. The magnetic field sensor is insensitive to the temperature variation with a temperature coefficient of 3.2 pm/°C.

A Temperature-Insensitive Twist Sensor by Using Low-Birefringence Photonic-Crystal-Fiber-Based Sagnac Interferometer

An optical fiber twist sensor is proposed by using solid core low birefringence photonic crystal fiber (LB-PCF)-based Sagnac interferometer. The twist effects on the fiber are theoretically analyzed. The results show that the dip wavelength of the transmission spectrum shifts with the twist angle with a high sensitivity and resolution of 1.00 nm/0 and 0.010 , respectively. The sensor is also insensitive to environmental temperature change with an ultralow thermal dependent coeffiecient of -0.5 pm/0C.

A novel wavelength detection technique for fiber Bragg grating sensors

This letter reports a minimum variance shift technique for wavelength detection in fiber Bragg grating (FBG) sensors. The technique has been demonstrated to offer high detection accuracy even when the spectrum of the FBG is in partial overlap with a neighboring FBG within a wavelength division multiplexed sensor array.

Magnetic field sensor using tilted fiber grating interacting with magnetic fluid.

A novel magnetic field sensor using tilted fiber Bragg grating (TFBG) interacting with magnetic fluid is proposed and experimentally demonstrated. The TFBG is surrounded by magnetic fluid whose complex refractive index changes with external magnetic field. The guiding properties of cladding modes excited by the TFBG are therefore modulated by the external magnetic field. As a result, the magnetic field strength measurement is successfully achieved within a range up to 196 Gauss by monitoring extinction ratio of cladding mode resonance. Furthermore, temperature variation can be obtained simultaneously from the wavelength shift of the TFBG transmission spectrum.

High-efficiency 1040 and 1078 nm laser emission of a Yb:Y2O3 ceramic laser with 976 nm diode pumping.

We report a high-efficiency diode-end-pumped polycrystalline Yb:Y2O3 ceramic laser. Pumped by a 976 nm laser diode bar and with an absorbed pump power of 2.8 W, cw output power of 1.74 W at 1078 nm, and 0.73 W at 1040 nm were obtained. The slope efficiency was measured to be 82.4% for the 1078 nm laser emission and 57.1% for the 1040 nm laser emission.

Magneto-optic fiber Sagnac modulator based on magnetic fluids

A magneto-optic modulator with a magnetic fluid film inserted into an optical fiber Sagnac interferometer is proposed. The magnetic fluid exhibits variable birefringence and Faraday effect under external magnetic field that will lead to a phase difference and polarization state rotation in the Sagnac interferometer. As a result, the intensity of the output light is modulated under the external magnetic field. Moreover, the modulator has a high extinction ratio and can easily be integrated in a single-mode fiber system. The performance of the modulator is not affected by ambient temperature variation from room temperature to 40 °C.

Polyvinyl alcohol-coated hybrid fiber grating for relative humidity sensing.

A relative humidity (RH) sensor based on a hybrid fiber grating coated with polyvinyl alcohol is proposed and demonstrated experimentally. The hybrid fiber grating is formed by superimposing a normal fiber Bragg grating (FBG) and a tilted-FBG around the same position of a single-mode fiber so that it can work in the reflection mode. Optical power of the reflected signal changes with the refractive index of the moisture sensitive polyvinyl alcohol, and humidity measurement can be realized. Experimental results show that the measurement range is 30 to 95% with the maximum sensitivity of 0.737 nW∕% RH. The average response time is ∼2 s and the measurement is nearly insensitive to temperature. Compared with the wavelength detection method used in normal FBG-based relative humidity sensors, the intensity demodulation method in this report is simpler and more cost-efficient.

Humidity Sensor Based on a Multimode-Fiber Taper Coated With Polyvinyl Alcohol Interacting With a Fiber Bragg Grating

An optical fiber relative humidity (RH) sensor is proposed and experimentally demonstrated with a multimode-fiber taper coated with a layer of polyvinyl alcohol cascading with a fiber Bragg grating. The operation is based on the interaction between the optical evanescent field and the coating along the taper waist. Humidity changes the refractive index of the extended coating, thus transmission loss of the light signal is introduced and humidity measurement is therefore realized. The measurement sensitivity is enhanced since the light passes through the taper twice. A maximum sensitivity of 1.994 μW/%RH is achieved within the measurement range of 30-95%RH with the taper waist diameter of 50.2 μm. The average response time is ~2 s and the measurement is nearly insensitive to temperature.