High-sensitivity and large-dynamic-range refractive index sensors employing weak composite Fabry-Perot cavities

Most sensors face a common tradeoff between high sensitivity and large dynamic range. We demonstrate here an all-fiber refractometer based on a dual cavity Fabry-Perot interferometer (FPI), which possesses the advantage of both high sensitivity and large dynamic range. Since the two composite cavities have a large cavity length difference, one can observe both fine and coarse fringes, which correspond to the long cavity and short cavity, respectively. The short cavity FPI and the use of an intensity demodulation method, mean that the individual fine fringe dips correspond to a series of quasi-continuous highly sensitive zones for refractive index measurement. By calculating the parameters of the composite FPI, we find that the range of the ultra-sensitive zones can be considerably adjusted to suite the end requirements. The experimental trends are in good agreement with the theoretical predictions. The co-existence of high sensitivity and large dynamic range in a composite FPI is of great significance to practical RI measurements

Enhancing the Visibility of Vernier Effect in a Tri-Microfiber Coupler Fiber Loop Interferometer for Ultrasensitive Refractive Index and Temperature sensing

In this paper a Vernier effect based sensor is analyzed and demonstrated experimentally in a tri-microfiber coupler (Tri-MFC) and polarization-maintaining fiber (PMF) loop interferometer (Tri-MFC-PMF) to provide ultrasensitive refractive index and temperature sensing. The main novelty of this work is an analysis of parameters of the proposed Tri-MFC-PMF with the objective of determining the conditions leading to a strong Vernier effect. It has been identified by simulation that the Vernier effect is a primary factor in the design of Tri-MFC-PMF loop sensing structure for sensitivity enhancement. It is furthermore demonstrated experimentally that enhancing the visibility of the Vernier spectrum in the Tri-MFC-PMF allows to achieve an ultrahigh refractive index and temperature sensitivity with improved measurement accuracy. Specifically it is shown that small values of the total phase difference (pi/16+Npi)~(pi/4+Npi), where N is an integer, accumulated over the PMF loop and Tri-MFC loop result in a strong Vernier effect. Experimentally an ultrahigh refractive index sensitivity of -20588 nm/RIU and temperature sensitivity of 0.019 nm/C are demonstrated by utilizing the stronger Vernier effect with clear Vernier spectrum. This analysis of the parameters may be useful to future researchers seeking to increase the measurement accuracy of sensors by enhancing the spectral visibility of the Vernier effect in other types of fiber optic interferometers

An optical fiber tip micrograting thermometer

An ~12 µm long Bragg grating was engraved in an ~5 µm diameter optical fiber tip by focused ion beam (FIB) milling. An ~10-dB extinction was achieved at 1570 nm with only 11 indentations. The grating was used for temperature sensing, and it exhibited a temperature sensitivity of ~22 pm/°C

Photonic crystal fiber half-taper probe based refractometer

A compact singlemode - photonic crystal fiber - singlemode fiber tip (SPST) refractive index sensor is demonstrated in this paper. A CO2 laser cleaving technique is utilised to provide a clean-cut fiber tip which is then coated by a layer of gold to increase reflection. An average sensitivity of 39.1 nm/RIU and a resolvable index change of 2.56 x 10-4 are obtained experimentally with a ~3.2 µm diameter SPST. The temperature dependence of this fiber optic sensor probe is presented. The proposed SPST refractometer is also significantly less sensitive to temperature and an experimental demonstration of this reduced sensitivity is presented in the paper. Because of its compactness, ease of fabrication, linear response, low temperature dependency, easy connectivity to other fiberized optical components and low cost, this refractometer could find various applications in chemical and biological sensing

Characterization of miniature fiber-optic Fabry-Perot interferometric sensors based on hollow silica tube

Sejatinya, Islam Nusantara bukanlah sesuatu yang baru. Penebalan kata “Nusantara” yang dikawinkan dengan “Islam” bukan hanya menegaskan nama, melainkan juga karakter untuk menunjukkan corak atau warna dari sebuah entitas yang heterogen. Keragaman sebagai salah satu tipologi Islam Nusantara adalah buah dari pergumulan panjang antara agama dan budaya; antara teks dengan konteks yang saling melengkapi satu sama lain sehingga menelurkan Islam yang ramah, inklusif dan fleksibel. Berangkat dari pijakan epistemologis dan historis, artikel ini coba menyuguhkan diskursus lama yang kembali mencuat di seputaran pertengahan tahun 2015 seiring dengan dihelatnya Muktamar dua ormas besar: NU dan Muhammadiyah. Hadirnya artikel ini sebetulnya juga ingin menjawab kasak-kusuk yang menuding bahwa Islam Nusantara hanya identik dengan kaum Nahdliyin. Sehingga term Islam Nusantara tidak lain dianggap sebagai nama baru dariIslam tradisionalis.Essentially, Islam Nusantara isn’t a new phenomenon. Bolding of both “Nusantara” with “Islam” not only affirmation about name but also character to show type or colour from the heterogenous entity. Diversity as one of Islam Nusantara typology is the result of a long struggle between religionand culture; between text and context that complement each other so that Islam spawned a friendly, inclusive and flexible. Start from the historical and epistemological approach, this article try to presents a classical discourse the back sticking around mid-2015 in line with the holding of the congress two major organizations: NU and Muhammadiyah. Actually, the presence o fthis article is also want to answer the rumors that accuse Islam Nusantara only synonymous with the Nahdliyin. Thus, Islam Nusantara considered as the new name of traditionalism Islam.</p

FIBER - OPTIC TEMPERATURE AND FLOW SENSOR SYSTEM AND METHODS

A fiber optic sensor, a process for utilizing a fiber optic sensor, and a process for fabricating a fiber optic sensor are described, where a double-side-polished silicon pillar is attached to an optical fiber tip and forms a Fabry-Perot cavity. In an implementation, a fiber optic sensor in accordance with an exemplary embodiment includes an optical fiber configured to be coupled to a light source and a spectrometer; and a single silicon layer or multiple silicon layers disposed on an end face of the optical fiber, where each of the silicon layer(s) defines a Fabry-Perot interferometer, and where the sensor head reflects light from the light source to the spectrometer. In some implementations, the fiber optic sensor may include the light source coupled to the optical fiber, a spectrometer coupled to the optical fiber, and a controller coupled to the high speed spectrometer