Showing papers on "Optical fiber published in 2016"
TL;DR: This record-breaking implementation of the MDIQKD method provides a new distance record and achieves a distance that the traditional Bennett-Brassard 1984 QKD would not be able to achieve with the same detection devices even with ideal single-photon sources.
Abstract: A protocol for secure quantum communications has been demonstrated over a record-breaking distance of 404 km.
737 citations
TL;DR: Sensors for Organic Species, New Schemes and Materials, and New SensingSchemes 220 Molecularly Imprinted Polymer (MIP)-Based Sensors 221 Photonic Crystals 223 Author Information 223 Corresponding Authors 223 Notes 223 Biographies 223 Acknowledgments 223 References 223
Abstract: Xu-dong Wang*,† and Otto S. Wolfbeis*,‡ †Department of Chemistry, Fudan University, 200433 Shanghai, P. R. China ‡Institute of Analytical Chemistry, Chemoand Biosensors, University of Regensburg, D-93040 Regensburg, Germany ■ CONTENTS Books, Reviews, and Articles of General Interest 204 Sensors for (Dissolved) Gases and Vapors 204 Hydrogen 204 Hydrocarbons 206 Oxygen 206 Carbon Dioxide 208 Nitrogen Oxides 208 Other Gases 208 Ammonia 209 Ethanol 209 Other Volatile Organic Compounds (VOC)s 210 Sensors for Humidity, Water Fractions, Hydrogen Peroxide, and Hydrazine 211 Humidity 211 Water Fractions in Organic Solvents 212 Hydrogen Peroxide 213 Sensors for pH Values, Ions, and Salinity 213 pH Values 213 Ions 214 Salinity and Ionic Strength 215 Sensors for Organic Species 216 Glucose Sensing 216 Sucrose 217 Oils 217 Other Organics 217 Biosensors 218 Nucleic Acid-Based Biosensors (DNAand Aptamer-Based) 218 Immunosensors 218 Enzymatic Biosensors 219 Other Biosensors 220 New Schemes and Materials 220 New Sensing Schemes 220 Molecularly Imprinted Polymer (MIP)-Based Sensors 221 Photonic Crystals 223 Author Information 223 Corresponding Authors 223 Notes 223 Biographies 223 Acknowledgments 223 References 223
348 citations
TL;DR: A core-clad fiber made of elastic, tough hydrogels is highly stretchable while guiding light and when stretched, the transmission spectrum of the fiber is altered, enabling the strain to be measured and also its location.
Abstract: A core-clad fiber made of elastic, tough hydrogels is highly stretchable while guiding light. Fluorescent dyes are easily doped into the hydrogel fiber by diffusion. When stretched, the transmission spectrum of the fiber is altered, enabling the strain to be measured and also its location.
317 citations
TL;DR: In this paper, the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR, was investigated.
Abstract: Different aspects of probabilistic shaping for a multispan optical communication system are studied. First, a numerical analysis of the additive white Gaussian noise (AWGN) channel investigates the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR. It is shown that if a small penalty of at most 0.1 dB SNR to the full shaping gain is acceptable, just two shaped PMFs are required per quadrature amplitude modulation (QAM) over a large SNR range. For a multispan wavelength division multiplexing optical fiber system with 64QAM input, it is shown that just one PMF is required to achieve large gains over uniform input for distances from 1400 to 3000 km. Using recently developed theoretical models that extend the Gaussian noise (GN) model and full-field split-step simulations, we illustrate the ramifications of probabilistic shaping on the effective SNR after fiber propagation. Our results show that, for a fixed average optical launch power, a shaping gain is obtained for the noise contributions from fiber amplifiers and modulation-independent nonlinear interference (NLI), whereas shaping simultaneously causes a penalty as it leads to an increased NLI. However, this nonlinear shaping loss is found to have a relatively minor impact, and optimizing the shaped PMF with a modulation-dependent GN model confirms that the PMF found for AWGN is also a good choice for a multi-span fiber system.
278 citations
TL;DR: A dielectric grating that can launch surface plasmon resonance (SPR) modes efficiently on the other side of flat metal films, which is similar to the conventional prism coupling mechanism, was proposed in this paper.
Abstract: We propose a dielectric grating that can launch surface plasmon resonance (SPR) modes efficiently on the other side of flat metal films, which is similar to the conventional prism coupling mechanism. Importantly, this structure can excite SPR under the normal incident light, which is particularly suitable for the integration with optical fiber tips. By launching the SPR mode near the wavelength of 1.55 $\mu\text{m}$ with a very narrow resonance line width (∼4 nm), this structure is promising for the development of high-performance portable, flexible, and real-time refractometric sensing applications.
266 citations
TL;DR: Graphene as a novel material has laid a foundation for its applications in optical fiber sensors, due to its unique properties, especially the optical properties as mentioned in this paper, which has received world-wide attention due to their high sensitivity, small size, good anti-electromagnetic disturbance ability and other potential advantages.
Abstract: Graphene as a novel material has laid a foundation for its applications in optical fiber sensors, due to its unique properties, especially the optical properties. On the other hand, optical fiber sensors have received world-wide attention due to their high sensitivity, small size, good anti-electromagnetism disturbance ability and other potential advantages. In this paper, the developments of graphene in the applications of optical fiber sensors were reviewed from four aspects. Firstly, the common preparation methods of graphene were introduced. Next, the optical properties of graphene have been concluded. And then, some typical optical fiber chemical and biological sensors based on graphene, such as temperature sensors, biological sensors and gas sensors, were reviewed. It was shown that graphene had a great potential in the optical fiber sensing technology. Furthermore, the deficiencies and challenges of the graphene in the applications of optical fiber sensors were analyzed. In a whole, the unique advantages of graphene have present their versatility and importance in the application fields of optical fiber sensors.
252 citations
TL;DR: The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg Grating technology in addition to being able to excite cladding modes resonantly as discussed by the authors.
Abstract: The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device opens up a multitude of opportunities for single-point sensing in hard-to-reach spaces with very controllable cross-sensitivities, absolute and relative measurements of various parameters, and an extreme sensitivity to materials external to the fiber without requiring the fiber to be etched or tapered. Over the past five years, our research group has been developing multimodal fiber-optic sensors based on TFBG in various shapes and forms, always keeping the device itself simple to fabricate and compatible with low-cost manufacturing. This paper presents a brief review of the principle, fabrication, characterization, and implementation of TFBGs, followed by our progress in TFBG sensors for mechanical and biochemical applications, including one-dimensional TFBG vibroscopes, accelerometers and micro-displacement sensors; two-dimensional TFBG vector vibroscopes and vector rotation sensors; reflective TFBG refractometers with in-fiber and fiber-to-fiber configurations; polarimetric and plasmonic TFBG biochemical sensors for in-situ detection of cell, protein and glucose.
210 citations
TL;DR: To the best of the knowledge, this is the broadest MIR SC generation observed so far in optical fibers and facilitates fiber-based applications in sensing, medical, and biological imaging areas.
Abstract: We experimentally demonstrate mid-infrared (MIR) supercontinuum (SC) generation spanning ∼2.0 to 15.1 μm in a 3 cm-long chalcogenide step-index fiber. The pump source is generated by the difference frequency generation with a pulse width of ∼170 fs, a repetition rate of ∼1000 Hz, and a wavelength range tunable from 2.4 to 11 μm. To the best of our knowledge, this is the broadest MIR SC generation observed so far in optical fibers. It facilitates fiber-based applications in sensing, medical, and biological imaging areas.
207 citations
TL;DR: In this paper, the authors present an overview of the Lab on Fiber technologies and devices with special focus on the design and development of advanced fiber optic nanoprobes for biological applications and discuss the strategies, main achievements and related devices developed in the “Lab on Fiber roadmap.
Abstract: This review presents an overview of “Lab on Fiber” technologies and devices with special focus on the design and development of advanced fiber optic nanoprobes for biological applications. Depending on the specific location where functional materials at micro and nanoscale are integrated, “Lab on Fiber Technology” is classified into three main paradigms: Lab on Tip (where functional materials are integrated onto the optical fiber tip), Lab around Fiber (where functional materials are integrated on the outer surface of optical fibers), and Lab in Fiber (where functional materials are integrated within the holey structure of specialty optical fibers).
This work reviews the strategies, the main achievements and related devices developed in the “Lab on Fiber” roadmap, discussing perspectives and challenges that lie ahead, with special focus on biological sensing applications.
202 citations
20 Jan 2016
TL;DR: In this article, a novel architecture conducive to monolithic on-chip integration is presented, which enables the scalable fabrication of high-performance polarization sensors with exceptional stability, compactness, and speed.
Abstract: In-line polarimeters perform nondestructive polarization measurements of optical signals, and play a critical role in monitoring and controlling the polarization environment in, for example, optical networks. While current in-line polarimeters are constructed with multiple optical components, either fabricated into an optical fiber or using free-space optics, we present here a novel architecture conducive to monolithic on-chip integration. This enables the scalable fabrication of high-performance polarization sensors with exceptional stability, compactness, and speed. The method relies on the detection of the highly polarization-dependent scattered field of a subwavelength antenna array known as a metasurface, and is shown here to provide polarization state measurements matching those of a state-of-the-art commercial polarimeter.
200 citations
TL;DR: The experimental observations agree well with numerical simulations, which show that the Kerr nonlinearity underlies the self-cleaning process, which may find applications in ultrafast pulse generation and beam-combining.
Abstract: We observe a nonlinear spatial self-cleaning process for femtosecond pulses in graded-index (GRIN) multimode fiber (MMF). Pulses with ∼80 fs duration at 1030 nm are launched into GRIN MMF with 62.5 μm core. The near-field beam profile at the output end of the fiber evolves from a speckled pattern to a centered, bell-shaped transverse structure with increasing pulse energy. The experimental observations agree well with numerical simulations, which show that the Kerr nonlinearity underlies the process. This self-cleaning process may find applications in ultrafast pulse generation and beam-combining.
TL;DR: This work uses numerical techniques to design an anti-resonant hollow-core fiber having one layer of non-touching tubes to determine which structures offer the best optical properties for the delivery of high power picosecond pulses.
Abstract: We investigate hollow-core fibers for fiber delivery of high power ultrashort laser pulses. We use numerical techniques to design an anti-resonant hollow-core fiber having one layer of non-touching tubes to determine which structures offer the best optical properties for the delivery of high power picosecond pulses. A novel fiber with 7 tubes and a core of 30µm was fabricated and it is here described and characterized, showing remarkable low loss, low bend loss, and good mode quality. Its optical properties are compared to both a 10µm and a 18µm core diameter photonic band gap hollow-core fiber. The three fibers are characterized experimentally for the delivery of 22 picosecond pulses at 1032nm. We demonstrate flexible, diffraction limited beam delivery with output average powers in excess of 70W.
TL;DR: By developing a systematic approach to fiber-based SPR designs, this work identifies and discusses future research opportunities based on a performance comparison of the different approaches for sensing applications.
Abstract: Surface Plasmon Resonance (SPR) fiber sensor research has grown since the first demonstration over 20 year ago into a rich and diverse field with a wide range of optical fiber architectures, plasmonic coatings, and excitation and interrogation methods. Yet, the large diversity of SPR fiber sensor designs has made it difficult to understand the advantages of each approach. Here, we review SPR fiber sensor architectures, covering the latest developments from optical fiber geometries to plasmonic coatings. By developing a systematic approach to fiber-based SPR designs, we identify and discuss future research opportunities based on a performance comparison of the different approaches for sensing applications.
TL;DR: The underpinning of this work is a grating architecture—a gold-coated highly tilted Bragg grating—that excites a spectral comb of narrowband-cladding modes with effective indices near 1.0 and below that opens research directions for highly sensitive plasmonic sensing in gas.
Abstract: Surface plasmon polaritons (SPP) can be excited on metal-coated optical fibres, enabling the accurate monitoring of refractive index changes. Configurations reported so far mainly operate in liquids but not in air because of a mismatch between permittivities of guided light modes and the surrounding medium. Here we demonstrate a plasmonic optical fibre platform that overcomes this limitation. The underpinning of our work is a grating architecture—a gold-coated highly tilted Bragg grating—that excites a spectral comb of narrowband-cladding modes with effective indices near 1.0 and below. Using conventional spectral interrogation, we measure shifts of the SPP-matched resonances in response to static atmospheric pressure changes. A dynamic experiment conducted using a laser lined-up with an SPP-matched resonance demonstrates the ability to detect an acoustic wave with a resolution of 10−8 refractive index unit (RIU). We believe that this configuration opens research directions for highly sensitive plasmonic sensing in gas. Fibre sensors are key to many minimally-invasive detection techniques but, owing to an index mismatch, they are often limited to aqueous environments. Here, Caucheteur et al. develop a high-resolution fibre gas sensor with a tilted in-fibre grating that allows coupling to higher-order plasmon modes.
TL;DR: This work demonstrates real-time distributed measurement with an intrinsically one-end-access reflectometry configuration by using a correlation-domain technique and discusses some drawbacks of this ultrahigh-speed configuration, including the reduced measurement accuracy, lowered spatial resolution and limited strain dynamic range.
Abstract: Optical fibre sensors based on Brillouin scattering have been vigorously studied in the context of structural health monitoring on account of their capacity for distributed strain and temperature measurements. However, real-time distributed strain measurement has been achieved only for two-end-access systems; such systems reduce the degree of freedom in embedding the sensors into structures, and furthermore render the measurement no longer feasible when extremely high loss or breakage occurs at a point along the sensing fibre. Here, we demonstrate real-time distributed measurement with an intrinsically one-end-access reflectometry configuration by using a correlation-domain technique. In this method, the Brillouin gain spectrum is obtained at high speed using a voltage-controlled oscillator, and the Brillouin frequency shift is converted into a phase delay of a synchronous sinusoidal waveform; the phase delay is subsequently converted into a voltage, which can be directly measured. When a single-point measurement is performed at an arbitrary position, a strain sampling rate of up to 100 kHz is experimentally verified by detecting locally applied dynamic strain at 1 kHz. When distributed measurements are performed at 100 points with 10 times averaging, a repetition rate of 100 Hz is verified by tracking a mechanical wave propagating along the fibre. Some drawbacks of this ultrahigh-speed configuration, including the reduced measurement accuracy, lowered spatial resolution and limited strain dynamic range, are also discussed. An optical fibre sensing scheme that measures strain with a high spatial resolution and a very high sampling rate has been developed. Optical fibre sensors based on Brillouin scattering are promising for monitoring structural health. The system built by Yosuke Mizuno of Tokyo Institute of Technology and colleagues measures the frequency shift induced in the fibre’s Brillouin gain spectrum on stretching the fibre. This frequency shift is converted into a phase delay of a sinusoidal waveform, which enables the direct detection of the frequency shift. The approach allows single-point strain measurements to be performed at a rate of up to 100 kilohertz at any point along the fibre. Distributed measurements at multiple points along the fibre are also possible, although at lower repetition rates. Importantly, the scheme only requires access from one end of the fibre.
TL;DR: The field of hybrid optical fibers is one of the most active research areas in current fiber optics and has the vision of integrating sophisticated materials inside fibers, which are not traditionally used in fiber optics.
Abstract: The field of hybrid optical fibers is one of the most active research areas in current fiber optics and has the vision of integrating sophisticated materials inside fibers, which are not traditionally used in fiber optics. Novel in-fiber devices with unique properties have been developed, opening up new directions for fiber optics in fields of critical interest in modern research, such as biophotonics, environmental science, optoelectronics, metamaterials, remote sensing, medicine, or quantum optics. Here the recent progress in the field of hybrid optical fibers is reviewed from an application perspective, focusing on fiber-integrated devices enabled by including novel materials inside polymer and glass fibers. The topics discussed range from nanowire-based plasmonics and hyperlenses, to integrated semiconductor devices such as optoelectronic detectors, and intense light generation unlocked by highly nonlinear hybrid waveguides.
TL;DR: This work proposes and experimentally demonstrate an ultimately optimized distributed fiber sensor capable of resolving 2100000 independent points, which corresponds to a one-order-of-magnitude improvement compared to the state- of-the-art.
Abstract: Distributed fiber sensing possesses the unique ability to measure the distributed profile of an environmental quantity along many tens of kilometers with spatial resolutions in the meter or even centimeter scale. This feature enables distributed sensors to provide a large number of resolved points using a single optical fiber. However, in current systems, this number has remained constrained to a few hundreds of thousands due to the finite signal-to-noise ratio (SNR) of the measurements, which imposes significant challenges in the development of more performing sensors. Here, we propose and experimentally demonstrate an ultimately optimized distributed fiber sensor capable of resolving 2100000 independent points, which corresponds to a one-order-of-magnitude improvement compared to the state-of-the-art. Using a Brillouin distributed fiber sensor based on phase-modulation correlation-domain analysis combined with temporal gating of the pump and time-domain acquisition, a spatial resolution of 8.3 mm is demonstrated over a distance of 17.5 km. The sensor design addresses the most relevant factors impacting the SNR and the performance of medium-to-long range sensors as well as of sub-meter spatial resolution schemes. This step record in the number of resolved points could be reached due to two theoretical models proposed and experimentally validated in this study: one model describes the spatial resolution of the system and its relation with the sampling interval, and the other describes the amplitude response of the sensor, providing an accurate estimation of the SNR of the measurements. A distributed fiber sensor has been developed that can resolve more than 2 million points along its length. The system, built by Andrey Denisov and co-workers from Ecole Polytechnique Federale de Lausanne, offers a spatial resolution of just 8.3 mm over a distance of 17.5 km. This has been achieved by combining phase-modulation correlation-domain analysis with temporal gating of the pump signal and a theoretical model to optimize the signal-to-noise ratio. The measurement time varies cubically with the number of sample points. Consequently, a measurement of 300 000 points corresponding to a resolution of 5 cm takes only 4 min. Thus, the researchers say that a coarse scan of the whole fiber can be quickly made prior to a finer resolution scan of the region of interest.
TL;DR: The proposed optical fiber/microfluidic plasmonic biosensor represents an appealing solution for rapid, low consumption and highly sensitive detection of analytes at low concentrations in medicine as well as in chemical and environmental monitoring.
TL;DR: In this paper, electron waves can be confined to and guided along the edges of monolayer and bilayer graphene sheets, analogous to the guiding of light waves in optical fibres.
Abstract: Experiments show that electron waves can be confined to and guided along the edges of monolayer and bilayer graphene sheets, analogous to the guiding of light waves in optical fibres.
20 May 2016
TL;DR: In this paper, an optomechanical fiber sensor that addresses liquids outside the cladding of standard, 8/125μm single-mode fibers with no structural intervention is presented.
Abstract: The analysis of chemical species is one of the most fundamental and long-standing challenges in fiber-optic sensors research. Existing sensor architectures require a spatial overlap between light and the substance being tested and rely either on structural modifications of standard fibers or on specialty photonic crystal fibers. In this work, we report an optomechanical fiber sensor that addresses liquids outside the cladding of standard, 8/125 μm single-mode fibers with no structural intervention. Measurements are based on forward stimulated Brillouin scattering by radial, guided acoustic modes of the fiber structure. The acoustic modes are stimulated by an optical pump pulse and probed by an optical signal wave, both confined to the core. The acoustic vibrations induce a nonreciprocal phase delay to the signal wave, which is monitored in a Sagnac interferometer loop configuration. The measured resonance frequencies and excitation strengths of individual modes agree with the predictions of a corresponding quantitative analysis. The acoustic reflectivity at the outer cladding boundary and the acoustic impedance of the surrounding medium are extracted from cavity lifetime measurements of multiple modes. The acoustic impedances of deionized water and ethanol are measured with better than 1% accuracy. The measurements successfully distinguish between aqueous solutions with 0, 4%, 8%, and 12% concentrations of dissolved salt. The new fiber-sensing paradigm might be used in the monitoring of industrial processes involving ionic solutions.
TL;DR: This work presents the first experimental realization of coherent Bragg scattering off a one-dimensional system-two strings of atoms strongly coupled to a single photonic mode-realized by trapping atoms in the evanescent field of a tapered optical fiber, which also guides the probe light.
Abstract: Up to 75% of light reflects from just 2000 atoms aligned along an optical fiber, an arrangement that could be useful in photonic circuits.
TL;DR: In this paper, the synthesis of stable silver nanoparticles in flower extract of Acmella oleracea and its dopamine sensing properties are reported, and a surface plasmon resonance (SPR) based fiber optic sensor has been fabricated using green synthesized silver particles as sensing material.
Abstract: Facile green synthesis of stable silver nanoparticles in flower extract of Acmella oleracea and its dopamine sensing properties are reported. UV–visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and particle size analysis were performed to ascertain the formation of silver nanoparticles. Aqueous dopamine sensing study of green synthesized silver nanoparticles was carried out. Further surface plasmon resonance (SPR) based fiber optic sensor has been fabricated using green synthesized silver nanoparticles as sensing material. The response time of the sensor is 6 min and the detection limit is 2 × 10−7 M.
TL;DR: The analysis and results presented in this paper constitute the first demonstration of distributed bending sensing, providing the cornerstone to further develop it into a fully distributed three-dimensional shape sensor.
Abstract: A theoretical and experimental study on the response of Brillouin scattering in multi-core optical fibers (MCF) under different curving conditions is presented. Results demonstrate that the Brillouin frequency shift of the off-center cores in MCF is highly bending-dependent, showing a linear dependence on the fiber curvature. This feature is here exploited to develop a new kind of distributed optical fiber sensor, which provides measurements of a distributed profile mapping the longitudinal fiber shape. Using conventional Brillouin optical time-domain analysis with differential pulse-width pairs, fully distributed shape sensing along a 1 km-long MCF is practically demonstrated. Experimental results show a very good agreement with the theoretically expected behavior deduced from the dependence of the Brillouin frequency on the strain induced by the fiber bending over a given core. The analysis and results presented in this paper constitute the first demonstration of distributed bending sensing, providing the cornerstone to further develop it into a fully distributed three-dimensional shape sensor.
TL;DR: A novel all-fiber-optic humidity sensor comprised of a WS2 film overlay on a side polished fiber (SPF) that can achieve optical power variation of up to 6 dB in a relative humidity (RH) range of 35%-85%.
Abstract: We demonstrate a novel all-fiber-optic humidity sensor comprised of a WS2 film overlay on a side polished fiber (SPF). This sensor can achieve optical power variation of up to 6 dB in a relative humidity (RH) range of 35%-85%. In particular, this novel humidity fiber sensor has a linear correlation coefficient of 99.39%, sensitivity of 0.1213 dB/%RH, and a humidity resolution of 0.475%RH. Furthermore, this sensor shows good repeatability and reversibility, and fast response to breath stimulus. This WS2 based all-fiber optic humidity sensor is easy to fabricate, is compatible with pre-established fiber optic systems, and holds great potential in photonics applications such as in all-fiber optic humidity sensing networks.
20 Mar 2016
TL;DR: In this article, a mid-IR fiber gas laser using feedback in an optical cavity is presented, which uses acetylene gas in a high-performance silica hollow-core fiber as the gain medium, and lases either continuous wave or synchronously pumped when pumped by telecom-wavelength diode lasers.
Abstract: Mid-infrared (IR) lasers are currently an area of rapid development, with several competing technologies. In traditional gas lasers, the effective interaction length is limited and the system as a whole is bulky and inflexible, limiting their applications. Standard gain fibers cannot be used in the mid-IR because the glass forming the fiber core is not transparent at these longer wavelengths. In this Letter, we report the demonstration of a mid-IR fiber gas laser using feedback in an optical cavity. The laser uses acetylene gas in a high-performance silica hollow-core fiber as the gain medium, and lases either continuous wave or synchronously pumped when pumped by telecom-wavelength diode lasers. We have demonstrated lasing on a number of transitions in the spectral band of 3.1–3.2 μm. The system could be extended to other selected molecular species to generate output in the spectral band up to 5 μm, and it has excellent potential for power scaling.
TL;DR: In this article, a fiber optic relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) coated with graphene oxide (GO) film was presented.
Abstract: A fiber optic relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) coated with graphene oxide (GO) film was presented. Amplitudes of the cladding mode resonances of the TFGB varies with the water sorption and desorption processes of the GO film, because of the strong interactions between the excited backward propagating cladding modes and the GO film. By detecting the transmission intensity changes of the cladding mode resonant dips at the wavelength of 1557 nm, the maximum sensitivity of 0.129 dB/%RH with a linear correlation coefficient of 99% under the RH range of 10–80% was obtained. The Bragg mode of TFBG can be used as power or wavelength references, since it is inherently insensitive to RH changes. In addition, the proposed humidity sensor shows a good performance in repeatability and stability.
TL;DR: It is experimentally demonstrate that pumping a graded-index multimode fiber with sub-ns pulses from a microchip Nd:YAG laser leads to spectrally flat supercontinuum generation with a uniform bell-shaped spatial beam profile extending from the visible to the mid-infrared at 2500 nm.
Abstract: We experimentally demonstrate that pumping a graded-index multimode fiber with sub-ns pulses from a microchip Nd:YAG laser leads to spectrally flat supercontinuum generation with a uniform bell-shaped spatial beam profile extending from the visible to the mid-infrared at 2500 nm. We study the development of the supercontinuum along the multimode fiber by the cut-back method, which permits us to analyze the competition between the Kerr-induced geometric parametric instability and stimulated Raman scattering. We also performed a spectrally resolved temporal analysis of the supercontinuum emission.
TL;DR: In this article, a fiber optic SPR sensor based on MMF-FBG-MMF (Multimode Fiber-Fiber Bragg Grating-Multi-mode Fiber) structure has been proposed and applied to dual-parameter measurement.
Abstract: Fiber optic SPR (Surface Plasmon Resonance) sensor based on MMF-FBG-MMF (Multi-mode Fiber–Fiber Bragg Grating–Multi-mode Fiber) structure has been proposed and applied to dual-parameter measurement– liquid refractive index and temperature. The fabrication method of this proposed sensor is simpler than other kinds of fiber optic SPR sensors. The basic sensing principle of fiber optic SPR sensors has been provided and the dual-parameter measurement system has been set up. The changes of NaCl resolution refractive index and temperature have been detected and analyzed. The refractive index sensitivity of the proposed sensor has reached 2556.8 nm/RIU, and the temperature sensitivity has been improved to 172 pm/°C.
TL;DR: The authors' MCF bending sensor was found to be highly sensitive (4094 pm/deg) to small bending angles and it is capable of distinguishing multiple bending orientations.
Abstract: In this Letter, we demonstrate a compellingly simple directional bending sensor based on multicore optical fibers (MCF). The device operates in reflection mode and consists of a short segment of a three-core MCF that is fusion spliced at the distal end of a standard single mode optical fiber. The asymmetry of our MCF along with the high sensitivity of the supermodes of the MCF make the small bending on the MCF induce drastic changes in the supermodes, their excitation, and, consequently, on the reflected spectrum. Our MCF bending sensor was found to be highly sensitive (4094 pm/deg) to small bending angles. Moreover, it is capable of distinguishing multiple bending orientations.
TL;DR: This work demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection.
Abstract: New optical fiber based spectroscopic tools open the possibility to develop more robust and efficient characterization experiments. Spectral filtering and light reflection have been used to produce compact and versatile fiber based optical cavities and sensors. Moreover, these technologies would be also suitable to study N-photon correlations, where high collection efficiency and frequency tunability is desirable. We demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection. As we do not observe any significant fine structure splitting for the neutral exciton transition within our spectral resolution (46 μeV), metamorphic QD single photon emission studied with our all-fiber Hanbury Brown & Twiss interferometer could lead to a more efficient analysis of entangled photon sources at telecom wavelength. This all-optical fiber scheme opens the door to new first and second order interferometers to study photon indistinguishability, entangled photon and photon cross correlation in the more interesting telecom wavelengths.