Sensitivity Adjustable In-Line High-Temperature Sensor Based on Metal Microwire Optical Fabry-Perot Interferometer

The detection of protein aggregates and its concentration, plays a relevant role in several fronts, namely at the detection of neurodegenerative diseases such as Alzheimer's, and the assessment of cellular stress linked to cell death. Evaluation of protein aggregation is an essential step of quality control in all stages of biopharmaceutical synthesis and transport, in order to guarantee the activity and desired immunogenicity of their products. The detection of protein aggregates often requires the use of expensive and complex techniques. Here we propose a fast and easy implementation solution, based on an optical fibre Fabry-Perot Interferometer (FPI) end tip resonator. The solution proposed revealed to be effective on the detection of protein aggregates, providing similar results as the ones obtained using a commercial spectrometer for fluorescence detection.

A microfluidic gas flowmeter based on optical fiber Fabry-Perot interferometer(FPI) was proposed and demonstrated. The sensor was formed by two embedded optical fibers with a microfluidic gas channel running across the two end faces. The gas flowrate was first tested by monitoring the shift of the resonancewavelength of the FPI. The intensity demodulation method was then applied to investigate thedynamic response of the sensor, by utilizing a tunable laser and a photodiode. The experimental results show that our proposed microfluidic gas flowmeter has high sensitivity and fast response.

A temperature sensor with two cascaded fiber Fabry-Perot interferometers (FPIs) is constructed and demonstrated, which works on envelope-based demodulation and exhibits a high temperature sensitivity. The sensor is fabricated by splicing a short segment of large mode area (LMA) fiber to a short segment of capillary tube fused with a section of single-mode fiber to form a cascaded FPI structure. Experimental results show that the temperature sensitivity achieves up to 249.22 pm/V by using envelope-based demodulation, which is much higher than the one obtained by directly tracing the resonant wavelength in the superposition interference spectrum or the one for a single FPI with air-cavity. Moreover, the proposed sensor is compact with dimension of <;1 mm. All the features make it promising for temperature measuring in many fields.

We have proposed and demonstrated a novel elastic optical fiber Fabry-Perot interferometer (FPI)-based ac magnetic field sensor with high magnetic sensitivity and correction of temperature crosstalk. The elastic FPI is formed by soft splicing using low Young's modulus polydimethylsiloxane material at the joint point of a hollow-core fiber and single-mode fibers and is fixed on a common supermendur rod, a kind of magnetostrictive material. AC magnetic field-induced length change of the magnetostrictive rod results in the obvious change of the FPI cavity length and finally is transduced to the intensity variation of the sensor signal, which makes the sensor highly sensitive to ac magnetic field. Taking advantage of the elastic FPI structure, the magnetic sensitivity (in terms of strain) is improved to 48 ppm/mT (75.01 pm/mT in terms of wavelength), compared with the low intrinsic sensitivity of the conventional magnetostrictive rod (usually below several ppm/mT and 0.39 ppm/mT in our case). Moreover, the impact of temperature cross-sensitivity is removed by retrieving the wavelength shift of the FPI interference spectrum based on the calibrated signal voltage versus wavelength shift. All the ac magnetic fields of different frequencies and intensities have been successfully detected and measured by our FPI sensor without the impact of temperature crosstalk. We believe such a simple, compact, and cost-effective sensor would be a promising candidate for accurate monitoring of ac magnetic field.

We demonstrated an ultrasensitive temperature sensor based on a unique fiber Fabry-Perot interferometer (FPI). The FPI was created by means of splicing a mercury-filled silica tube with a single-mode fiber (SMF). The FPI had an air cavity, which was formed by the end face of the SMF and that of the mercury column. Experimental results showed that the FPI had an ultrahigh temperature-sensitivity of up to -41 nm/°C, which was about one order of magnitude higher than those of the reported FPI-based fiber tip sensors. Such a FPI temperature sensor is expected to have potential applications for highly-sensitive ambient temperature sensing.

This paper presents a comprehensive review of optical fiber sensors (OFSs), including FBG, distributed optical fiber sensor and Fabry-Perot interferometer, and their applications within harsh environments, which include extremely high temperatures (from 275 °C to 1750 °C) and low temperatures (from −271.15 °C to −40 °C, namely cryogenic conditions: from 2 K to 233.15 K), and high levels of ionizing radiation (with a maximum gamma dose up to 2 GGy, and a maximum neutron fluence of approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5 \times 10^{19}$ </tex-math></inline-formula> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). After a brief introduction of the principles of OFSs and mechanisms of interrogation, this paper focuses on the existing works for the above three operating environments. Attention have been paid to material selection for fabricating fibers, effects of doping with rare earth elements, femtosecond laser engraving, pre-processing and post-processing (i.e., annealing) that are employed to overcome issues faced byOFSs in extreme temperatures and radiation environments. Application examples and practical test cases are also presented. Through these examples, the limitations in the current state-of-the-art are acknowledged and the key problems are identified. Potential solutions to some of these problems are also elucidated. A feature of this paper is the amalgamation of many research methodologies and outcomes in three seemingly distinct environmental conditions in one place so that different solution techniques can be integrated to advance OFS technologies, especially for extreme environment applications.

A highly sensitive, compact, and low-cost trace gas sensor based on photothermal effect in a hollow-core fiber Fabry-Perot interferometer (FPI) is described. The Fabry-Perot sensor is fabricated by splicing a piece of hollow-core photonic bandgap fiber (HC-PBF) to single-mode fiber pigtails at both ends. The absorption of a pump beam in the hollow core results in phase modulation of probe beam, which is detected by the FPI. Experiments with a 2 cm long HC-PBF with femtosecond laser drilled side-holes demonstrated a response time of less than 19 s and noise equivalent concentration (NEC) of 440 parts-per-billion (ppb) using a 1 s lock-in time constant, and the NEC goes down to 117 ppb (2.7×10-7 in absorbance) by using 77 s averaging time.

A U-shaped optical fiber inline microchannel was fabricated by femtosecond laser irradiation and subsequent selective chemical wet etching. A high quality micro-cavity embedded inside the channel was obtained to construct a Fabry-Perot interferometer (FPI). A fringe visibility of 20 dB in spectrum domain was achieved. High temperature survivability of this micro device was also demonstrated. The proposed assembly-free optical fiber inline interferometer is attractive for sensing applications in high-temperature harsh environments.

At present, the follow-up platform in the guidance device is mostly the direct drive mode of the motor. in order to reduce the weight and save space The way of wire rope indirect transmission is proposed. In the high-temperature environment, the wire rope will be thermally expanded during the transmission process, resulting in reduced transmission accuracy or even failed due to slippage, and similar problems may occur in the low temperature environment. Since the pre-tensioning device is not easy to set up in a small space, in this paper, the deformation of steel wire rope and transmission wheel in high and low temperature environment is calculated. By calculating the elongation of the steel wire rope in the high and low temperature environment and the thermal expansion of the transmission wheel, the advantages and disadvantages of the automatic tensioning effect of the rope system in high and low temperature environment can be analyzed and compared, which lays a foundation for the improvement of the whole transmission system.

In this work, an ultra-compact in-line fiber-optic Fabry-Perot interferometer is presented. The interferometric structure consists of a thin (<1 μm) amorphous silicon layer in line integrated into a standard single-mode optical fiber by means of an electric arc discharge technique. The device exhibits low loss (1.46 dB) and high interference fringe visibility (~30 % in linear scale) both in reflection and transmission due to the high refractive index contrast between silica and α-Si. A high linear temperature sensitivity up to 75 pm/°C is demonstrated in the range 15–52 °C. The proposed device is simple, compact, cost-effective, and attractive for point monitoring sensing application in ultra-high-temperature sensing in harsh environments.

Prolonged exposure to high humidity and high temperature environment can aggravate influenza virus infection through intestinal flora and Nod/RIP2/NF-κB signaling pathway

Temperature measuring is a daily procedure carried out worldwide in practically all environments of human activity, but it takes particular relevance in industrial, scientific, medical, and food processing and production areas. The characteristics and performance of the temperature sensors required for such a large universe of applications have opened the opportunity for a comprehensive range of technologies and architectures capable of fulfilling the sensitivity, resolution, dynamic range, and response time demanded. In this work, a highly sensitive fiber optic temperature sensor based on a double-cavity Fabry-Perot interferometer (DCFPI) is proposed and demonstrated. Taking advantage of the Vernier effect, we demonstrate that it is possible to improve the temperature sensitivity exhibited by the polymer-capped fiber Fabry-Perot interferometer (PCFPI) up to 39.8 nm/°C. The DCFPI is sturdy, reconfigured, and simple to fabricate, consisting of a semi-spherical polymer cap added to the surface of the ferrule of a commercial single-mode fiber connector (SMF FC/PC) placed in front of a mirror at a proper distance. The length of the air cavity (Lair) was adjusted to equal the thickness of the polymer cap (Lpol) plus a distance δ to generate the most convenient Vernier effect spectrum. The DCFPI was packaged in a machined, movable mount that allows the adjustment of the air cavity length easily but also protects the polymer cap and simplifies the manipulation of the sensor head.

We propose and demonstrate a cross-talk free simultaneous measurement system for temperature and external refractive index (ERI) implemented by dual-cavity Fabry-Perot (FP) fiber interferometer. The sensing probe consists of two cascaded FP cavities formed with a short piece of multimode fiber (MMF) and a micro-air-gap made of hollow core fiber (HOF). The fabricated sensor head was ultra-compact; the total length of the sensing part was less than 600 mum. Since the reflection spectrum of the composite FP structures is given by the superposition of each cavity spectrum, the spectrum measured in the wavelength domain was analyzed in the Fourier or spatial frequency domain. The experimental results showed that temperature could be determined independently from the spatial frequency shift without being affected by the ERI, while the ERI could be also measured solely by monitoring the intensity variation in the spatial frequency spectrum. The ERI and the temperature sensitivities were approximately 16 dB/RIU for the 1.33-1.45 index range, and 8.9 nm/ degrees C at low temperature and 14.6 nm/ degrees C at high temperature, respectively. In addition, it is also demonstrated that the proposed dual-cavity FP sensor has potential for compensating any power fluctuation that might happen in the input light source.

High sensitivity temperature sensor based on fiber air-microbubble Fabry-Perot interferometer with PDMS-filled hollow-core fiber

A novel sensitivity-enhanced intrinsic fiber Fabry-Perot interferometer (IFFPI) high temperature sensor based on a hollow-core photonic crystal fiber (HC-PCF) and modified Vernier effect is proposed and experimentally demonstrated. The compact all fiber IFFPIs are easily constructed by splicing one end of the HC-PCF to a leading single mode fiber (SMF) and applying an arc at the other end of the HC-PCF to form a pure silica tip. The Vernier effect is formed by three beams of lights reflected from the SMF-PCF splicing joint, and the two air/glass interfaces on the ends of the collapsed HC-PCF tip, respectively. This Vernier effect based fiber sensor can stand with high temperature up to 1200°C, in this work, and experimental results exhibit good linearity, stability and repeatability. The temperature sensitivity can be further enhanced by reducing length of pure silica tip—that is, simply optimizing the discharge time and intensity. The fabrication of the sensitivity-enhanced IFFPI is straightforward, reproducible and low cost, which shows a potential for practical applications in various industrial processes.