A dual-parameter sensor based on a photonic crystal fiber (PCF) concatenated with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of magnetic field and temperature. Novel magnetic fluids (MF) with different concentration and surfactant are filled in the air holes of PCF. The magnetic field measurement property is only determined by PCF, while the temperature is co-determined by PCF and FBG. Experimental results show that the wavelength shift has a good linearity corresponding with temperature and magnetic field. Temperature and magnetic field sensitivity are proportional to concentration of MF and are affected by different surfactants. For PCF point, when polyethylene glycol is used as a surfactant and the magnetic fluid concentration is equal to 0.15, the highest magnetic field sensitivity is up to 924.63 pm/mT. The proposed sensor has a high sensitivity as well as cross-sensitivity resistance, which provides a promising candidate for dual-channel filtering or multi-parameter measurement applications.

Magnetic field and temperature dual-parameter sensor based on magnetic fluid materials filled photonic crystal fiber

The unique structural characteristic of no-core fiber (NCF) have extended the sensing applications based on multimode interference self-imaging, evanescent wave absorption and materials coating, which are widely used in the measurement of various physical, chemical and biological parameters An overview of the NCF-based sensing applications is spread out with specific emphasis on measurement methods, structural improvements and the combination of sensitive materials Different prototypes of NCF-based sensors are meticulously outlined First, the single NCF-based sensors with different analysis principles are reviewed, and the advantages of structural improvement including fiber taper, lateral-offset fusing and internal waveguide writing are compared Second, the cascading of NCF with fiber gratings or other structures to realize multi-parameter measurement and widen the application field are also discussed Then, NCF combines sensitive materials to measure physical/chemical parameters or coats metal film to excite surface plasmon resonance are addressed, and representative examples of the latest research progress are presented to confirm the potential value of NCF-based sensors in biosensing What’s more, the sensing characteristics of applying NCF structure in different ways are also introduced In a whole, this article detailedly summarizes the sensing applications, concludes the challenges and points out the research direction in the development of NCF-based sensors

Review of no-core optical fiber sensor and applications

A novel D-shaped fiber structure combined with a fiber Bragg grating for refractive index (RI) and temperature sensing is proposed and experimentally investigated. Thanks to the etched cladding of D-shaped fiber, the resulting interference is strongly influenced by the surrounding refractive index. By monitoring the dip wavelength of D-shaped fiber structure, the refractive index can be measured. Theoretical analysis and simulations were conducted to investigate the cladding mode propagating behavior influenced by the surrounding RI. Combined with the temperature sensing property of fiber Bragg grating (FBG), the possibility of simultaneously measuring the RI and temperature relies on monitoring the resonance dip of the D-shaped fiber modal interferometer and the Bragg wavelength of the FBG. Experimental results showed that the RI sensitivity of −31.79 nm/RIU within the range of 1.333 ~ 1.428, and a temperature sensitivity of 28.7 pm/°C can be obtained. The proposed sensor with simple configuration, low cost and easy fabrication is suitable for refractive index and temperature sensing applications.

Refractive Index and Temperature Sensor Based on D-Shaped Fiber Combined With a Fiber Bragg Grating

A high-sensitivity temperature sensor based on photonic crystal fiber Sagnac interferometer is proposed and studied. All holes of the PCF are filled with ethanol with capillarity. The cladding air holes are uniform arrangements. The two air holes around the core are removed to form new core modes with high birefringence. The sensitivities of the temperature can be up to −8.7657 and 16.8142 nm/
 $$^{\circ }$$
 C when temperature rises from 45 to 75 
 $$^{\circ }$$
 C and the fiber length is 5.05 cm. And when temperature rises from 10 to 45 
 $$^{\circ }$$
 C, the sensitivity can reach −7.848 and 16.655 nm/
 $$^{\circ }$$
 C with fiber length 2.11 cm. The performance of the selective-filled and the fully-filled PCF with temperature from 45 to 75 
 $$^{\circ }$$
 C and fiber length 5.05 cm are analyzed and compared. The fully filling can better achieve PCF’s sensing performance. The simple structure and high sensitivities make the temperature sensor easy to achieve. The temperature sensor with high sensitivities and good linearity has great application value for environmental temperature detecting.

A high-sensitivity temperature sensor based on Sagnac interferometer employing photonic crystal fiber fully filled with ethanol

We propose a highly-sensitive temperature sensor employing a Mach-Zehnder interferometer (MZI) based on silicon-on-insulator (SOI) platform The waveguide widths in the two MZI arms are tailored to have different temperature sensitivities but nearly the same group refractive indices A temperature sensor with an enhanced sensitivity of larger than 438pm/°C is experimentally demonstrated, which is over seven times larger than that of conventional silicon optical temperature sensor (about 60pm/°C for quasi-TM mode) Moreover, the sensor is easy to fabricate, only by a single mask, and no need of any polymer cladding, which makes it more robust, and can be used in lab-on-chip systems as a temperature monitor

Temperature sensor with enhanced sensitivity based on silicon Mach-Zehnder interferometer with waveguide group index engineering.

In this letter, a temperature sensor based on a fiber ring laser with a reflective Sagnac loop is proposed. The reflective Sagnac loop inserted into the fiber ring laser through a downlead optical fiber is used as the filter and sensing head to supply high temperature sensitivity. As the temperature varies, the transmission spectrum of Sagnac loop changes, leading to the shift of emission wavelength of a fiber ring laser. We obtain a temperature sensor system with a high temperature sensitivity of 1.739 nm/°C, a narrow 3-dB bandwidth less than 0.05 nm, and a high signal-to-noise ratio $\sim 50$ dB. Moreover, it is convenient to achieve the remote sensing by changing the length of the downlead optical fiber.

Temperature Sensor Based on Fiber Ring Laser With Sagnac Loop

In this paper, we propose and demonstrate a compact dual-parameter sensor for magnetic field intensity and temperature based on the singlemode no-core singlemode fiber. The no-core fiber (NCF) is coated with the magnetic fluid to detect the magnetic field and temperature simultaneously. The fundamental mode light launched from the singlemode fiber (SMF) will be decomposed into high-order modes lights in the NCF, and then, the high-order modes lights will finally interfere in the exit SMF. Because different interference dips have different sensitivities to the magnetic field intensity and temperature, the cross sensitivity of the magnetic field intensity and temperature can be effectively eliminated by monitoring two discrete interference dips. For the two dips monitored in the experiment, the proposed sensor has the magnetic field sensitivities of 7.43288 and 6.20037 pm/Oe, respectively, and the temperature sensitivities of −0.2469 and −0.28667 nm/°C, respectively. The proposed sensor is compact and easy to setup, and has good potential in applications.

Simultaneous Magnetic Field and Temperature Measurement Based on No-Core Fiber Coated With Magnetic Fluid

In this paper, a novel dual-parameter measurement scheme using a long-period grating (LPG) concatenated with polarization maintaining fiber (PMF) in a Sagnac loop was proposed and experimentally demonstrated to measure temperature and refractive index (RI) simultaneously. There are two types of dips in the output spectrum of the proposed sensor, which are formed by the LPG and Sagnac loop. Compared with the traditional Sagnac loop sensors using PMF only, the birefringence induced by the LPG changes the phase difference and makes the dips of the Sagnac loop sensitive to surrounding RI. Due to different interference mechanisms, the dual-parameter measurement is realized by Sagnac loop and LPG with different sensitivities to temperature and RI. Experiments show that in the output spectrum of the sensor, the dip of the LPG has the sensitivities of 0.201 nm/°C and −8.36 nm/RIU, and the dip of the Sagnac loop has the sensitivities of −1.06 nm/°C and −23.068 nm/RIU. The proposed sensor has a simple structure and great potential in biological, chemical, and ocean fields.

A Dual-Parameter Sensor Using a Long-Period Grating Concatenated With Polarization Maintaining Fiber in Sagnac Loop

In this paper, a remote magnetic field sensor based on intracavity absorption of evanescent field is experimentally demonstrated. A single-mode-no-core-single-mode (SNCS) fiber coated with magnetic fluid (MF) is inserted into a fiber ring laser through a circulator and a 3-dB coupler, and it works as the filter and sensing head simultaneously. As the light oscillates in the cavity of the fiber ring laser, intracavity absorption of the evanescent field will be induced in the interface of the no-core fiber and MF. We obtain a magnetic field sensor with a narrow 3-dB bandwidth that is less than 0.05 nm, a high signal-to-noise ratio ~40 dB, and magnetic sensitivity of 52.1 pm/mT and -0.3679 dBm/mT. Moreover, experiments show that it is convenient to achieve remote sensing by selecting different lengths of the transmission optical fiber connecting the circulator and 3-dB coupler, which has a slight impact on the sensitivity.

Remote Magnetic Field Sensor Based on Intracavity Absorption of Evanescent Field

In this paper, we propose a remote gas pressure sensor based on a fiber ring laser embedded with a Fabry–Perot (F–P) interferometer and a Sagnac loop. A compact optic-fiber F–P interferometer is inserted in the fiber laser and works as the sensing head for gas pressure detection. A wavelength selective filter based on optic-fiber Sagnac loop is used in the fiber laser. The sensitivity of −9.69 nm/kPa is obtained with a narrow 3-dB bandwidth less than 0.02 nm and high signal-to-noise ratio (SNR) ∼45 dB. Moreover, the excellent performance of the gas pressure sensor for remote detection is demonstrated.

Su Genghua

Papers

Temperature Sensor Based on Fiber Ring Laser With Sagnac Loop

Simultaneous Magnetic Field and Temperature Measurement Based on No-Core Fiber Coated With Magnetic Fluid

A Dual-Parameter Sensor Using a Long-Period Grating Concatenated With Polarization Maintaining Fiber in Sagnac Loop

Remote Magnetic Field Sensor Based on Intracavity Absorption of Evanescent Field

Remote Gas Pressure Sensor Based on Fiber Ring Laser Embedded With Fabry–Pérot Interferometer and Sagnac Loop