Silica Optical Fibers Research Articles

Performance comparison and mechanism of electron irradiation “Capsule” type and “Panda” type polarization maintaining silica optical fiber

Using electron irradiation with energy of 160 keV and 1 MeV, it is found that the irradiation induced loss of “Capsule” type polarization maintaining silica optical fiber is significantly more serious than that of “Panda” type polarization maintaining silica optical fiber. With the help of loss spectra, FTIR and XPS analysis methods, the difference mechanism of irradiation resistance between the two kinds of optical fiber is discussed from the perspective of defects and preparation technology.

(INVITED) On the evolution of nanoparticles in nanoparticle-doped optical fibers

The doping of dielectric nanoparticles (NPs) into the cores of silica fibers doped with a rare earth (RE) has proven to be an effective approach for controlling the spectroscopic performance of the rare earth. However, little is understood about the chemical and structural evolution of the NPs during fiber preform fabrication, or how any process-induced changes in the NPs affect the optical properties of the resultant fiber. In this work, rare-earth-doped alkaline-earth (AE) fluoride [RE:(AE)F2, RE = Yb, Eu; AE = Ca, Sr, Ba] nanoparticles were synthesized, suspension-doped in a silica preform fabricated using modified chemical vapor deposition (MCVD), and their evolution from as-synthesized to processed into a final preform were thoroughly studied. A thermal profile of the preform during fabrication was developed based on optical-pyrometer temperature measurements and used for time/temperature/structural correlations. A series of characterization methods, including x-ray diffraction, electron microscopy, optical spectroscopy, and thermochemical analyses were employed to study the NP phase and structure evolution. The fluoride NPs are shown to react with the core-glass soot, eventually oxidizing and amorphizing under the thermal treatment associated with the preform fabrication. This work sets the foundation for understanding the composition and structure of RE:(AE)F2 NPs in silica optical fiber cores, and aids in the understanding and tailoring of the optical properties of the resultant fiber.

Broadband tunable light emitters based on composition graded nanomaterials grown over silica optical fiber

In this study, growth and characterization of a full composition graded ZnCdSSe quaternary alloys on top of a silica optical fiber were demonstrated. The growth took place in a single furnace run using ZnS and CdSe as precursor materials and various characterization methods were utilized to figure out the chemical, structural and optical properties of the nanostructures. The results are very promising and shows that broadband tunable light emitters can be obtained using a non-standard and more functional substrate. The light emitted from the materials not only cover the full visible spectrum but also could be coupled into to the fiber core and might open a new era where different wavelengths are needed to be achieved from a single fiber tip. Achievement for the growth of widely tunable materials over a silica fiber is very valuable and paves the way for new applications including but not limited to medical surgery, sensing, optical communication, displays, lighting, decorations, and so on.

Design and Characterisation of an Optical Fibre Dosimeter Based on Silica Optical Fibre and Scintillation Crystal

In nuclear power plants, particle accelerators, and other nuclear facilities, measuring the level of ionising gamma radiation is critical for the safety and management of the operation and the environment’s protection. However, in many cases, it is impossible to monitor ionising radiation directly at the required location continuously. This is typically either due to the lack of space to accommodate the entire dosimeter or in environments with high ionising radiation activity, electromagnetic radiation, and temperature, which significantly shorten electronics’ lifetime. To allow for radiation measurement in such scenarios, we designed a fibre optic dosimeter that introduces an optical fibre link to deliver the scintillation radiation between the ionising radiation sensor and the detectors. The sensors can thus be placed in space-constrained and electronically hostile locations. We used silica optical fibres that withstand high radiation doses, high temperatures, and electromagnetic interference. We use a single photon counter and a photomultiplier to detect the transmitted scintillation radiation. We have shown that selected optical fibres, combined with different scintillation materials, are suitable for measuring gamma radiation levels in hundreds of kBq. We present the architecture of the dosimeter and its experimental characterisation with several combinations of optical fibres, detectors, and scintillation crystals.

Thermoluminescence kinetic parameters of proton-irradiated germanium doped flat-shape optical fibres

Glow curve is a key element in thermoluminescence (TL) studies as it provides on-the-ground understanding on the trapping mechanism inside the crystal lattice and hence stability of the TL material. In the present work, luminescence mechanism of the in-house fabricated germanium doped (Ge-doped) flat-shape silica optical fibres have been investigated following irradiation by 150-MeV proton beams. Results of TL dose-response showed that there is a linear relationship between TL response and proton doses from 1 to 10 Gy, with a coefficient of determination close to one. The structure of glow curve remains unchanged throughout the studied dose range with a maximum glow peak dominated at temperature of within 250–290 °C. A Tmax-Tstop plot reveals not only horizontal regions but also smooth slopes, indicative of the presence of a continuum distribution of glow peaks and trap depth. A computerised glow curve deconvolution analysis of the respective fibre glow-curves demonstrated that they were composed of five strongly overlapping peaks underlying a broad TL spectrum, obtaining figures of merit in the range of 0.56–1.64%. The main physical kinetic parameters (activation energy and frequency factor) of the fitted glow peaks were obtained using GlowFit software. The data suggest that the TL glow peaks of the Ge-doped silica optical fibres obey second-order kinetics.

Influences of Bi and Yb ions on the emission efficiency of an Er-doped silica optical fiber

We investigate the spectral characteristics of three kinds of home-made active silica fibers, namely, Er-doped fiber (EDF), Bi/Er co-doped fiber (BEDF), and Bi/Er/Yb co-doped fiber (BEYDF), and thus explore the influences of Bi and Yb ions on the absorption and emission performances in the EDF. Compared with the EDF, the absorption cross section at 980 nm and the fluorescent lifetime at 1535 nm in the BEDF are enhanced by 1.2 × 10−25 m2 and 0.68 ms, respectively. Found that the fluorescent intensity in the BEDF is higher, and the emission slope efficiency of Er ions in the BEDF is more than doubled. Moreover, compared with the BEDF, the absorption intensity and bandwidth around 980 nm in the BEYDF are significantly enhanced and broadened, and its fluorescent lifetime at 1535 nm is improved by 1.08 ms. Their fluorescent intensities are increased with the increase of the pump power. Also found that the emission slope efficiency of Er ions in the BEYDF is more than doubled. Furthermore, their local microstructural models are also built up, and their energy levels and excited state characteristics are analyzed based on the density functional theory. These results indicate that co-doping Bi and Yb ions into the EDF could improve the optical characteristics of Er ions, especially the emission efficiency, which is potentially applied in optical amplifier and laser systems, and so on.

Influence of launch beam distribution on power flow and angular division multiplexing in seven-core silica optical fibers

We analyze the effect of launch beam distribution on space-division multiplexing (SDM) performance in multimode multicore silica optical fibers (MM MC SOF) with seven cores. The time-independent power flow equation (TI PFE) is used to explore the effect of the width of the distribution of the Gaussian launch beam on power flow in each of the seven cores. We show that the optical fiber length at which the equilibrium mode distribution (EMD) and steady-state distribution (SSD) are obtained is greatly influenced by the width of the Gaussian launch beam distribution. We further show that when the width of the Gaussian launch beam distribution widens, the optical fiber length at which angular division multiplexing (ADM) in each of the seven cores can be realized with minimal crosstalk between neighboring angular optical channels decreases. We demonstrate that, for increasing the capacity of an optical fiber transmission system, an SDM system with two- and three-channel ADM and multicore optical fiber multiplexing can be implemented with the proposed seven-core MM MC SOF at optical fiber lengths up to ≈1 km (2 ADM channels × 7 cores) and ≈200 m (3 ADM channels × 7 cores), respectively. Such characterization of MM MC SOFs under various launch conditions is important for building a multicore optical fiber SDM transmission system.

Green Technology Solution for Small-World Communication Using Plastic Optical Fiber (POF) and Light Emitting Diode (LED)—Design and Application

Plastic optical fiber (POF) has become a dominant technology, with potential to be fully utilized in a small-world communication system because it has many advantages over existing systems. Among several high-speed solutions, POF can be considered as one of the most promising technologies because of its attractive features, such as efficiency, user friendly, environmentally friendly, low maintenance and economic metric, compared to silica fiber optics. POF devices are divided into several types based on fabrication techniques and continue to spread to a number of applications that have a high impact in the world of communication today. This paper will discuss the overall POF technology and sustainable solutions for small-world communication from device fabrication, device types, configurations and applications. Discussion will focus on the technologies that have been developed in our laboratory concerning a user-friendly approach, energy efficiency, ease of maintenance and high-performance solution. The performance of our optical splitter is comparable to commercialized devices that are less than 5 dB of insertion loss and 0.53 dB of excess loss. This sustainable solution in high-speed communication is the first reported up to this time.

Luminescence and laser properties of RE-doped silica optical fibers: The role of composition, fabrication processing, and inter-ionic energy transfers

Silica glass doped with rare-earth ions remains one of the most frequently used materials for fiber lasers and amplifiers, owing to various advantages such as high thermal resistance, mechanical and chemical durability, high transparency up to 2.2 μm, and last but not least, a proven and relatively cheap technology. However, the performance of fiber lasers and amplifiers based on silica glass is limited by several drawbacks, including low solubility of rare earths, which causes a high rate of inter-ionic energy transfers processes, or high phonon energy of the silica lattice, which leads to non-radiative decay via multiphonon relaxation. Both obstacles can be countered by various strategies, with the most perspective being the addition of suitable co-dopants. The luminescence properties and laser characteristics of the final optical fiber are thus strongly dependent on the composition, as well as the fabrication processing of the material. In this review, we summarize the basic concepts and recent developments in the role of various co-dopants of rare earth ions, the fabrication processes used in the making of high-silica fibers and the inter-ionic energy-transfers, with respect to their influence on the luminescence and laser properties of the fibers.

Co-Doping Effect of Bismuth Ions on the Gain Characteristics of Er-Doped Silica Optical Fiber

By examining the spectral and amplification characteristics of Er-doped silica fiber (EDSF) and Bi/Er co-doped silica fiber (BEDSF), an active doped silica fiber with broadband- and flat-gain is investigated. Results show that the bandwidth of BEDSF with a gain greater than 20 dB is approximately 50 nm. Moreover, in the entire C-band, the gain of BEDSF exceeds 26 dB with a fluctuation range of approximately 2 dB. The excellent performance may mainly come from the role of bismuth ions. Further analysis demonstrates that the emission and gain cross-sections are enhanced, the bandwidth is broadened, and the flatness is also optimized by co-doping Bi ions. The fluorescence lifetime of Er3+ is lengthened by 1.82 ms, illustrating that there may exist energy transfer from Bi-related active centers to Er3+. The results indicate that the proposed BEDSF has significant potential application in optical fiber amplifiers, lasers, sensors, and so on.

Tapered Optical Fibers Coated with Rare-Earth Complexes for Quantum Applications.

Crystals and fibers doped with rare-earth (RE) ions provide the basis for most of today’s solid-state optical systems, from lasers and telecom devices to emerging potential quantum applications such as quantum memories and optical to microwave conversion. The two platforms, doped crystals and doped fibers, seem mutually exclusive, each having its own strengths and limitations, the former providing high homogeneity and coherence and the latter offering the advantages of robust optical waveguides. Here we present a hybrid platform that does not rely on doping but rather on coating the waveguide—a tapered silica optical fiber—with a monolayer of complexes, each containing a single RE ion. The complexes offer an identical, tailored environment to each ion, thus minimizing inhomogeneity and allowing tuning of their properties to the desired application. Specifically, we use highly luminescent Yb3+[Zn(II)MC (QXA)] complexes, which isolate the RE ion from the environment and suppress nonradiative decay channels. We demonstrate that the beneficial optical transitions of the Yb3+ are retained after deposition on the tapered fiber and observe an excited-state lifetime of over 0.9 ms, on par with state-of-the-art Yb-doped inorganic crystals.

Influence of the monovalent bismuth on optical properties in Bi-doped silica optical fiber

Monovalent bismuth-related centers are studied by using first-principle methods in Bi-doped silica optical fiber. On the basis of 6-membered ring (6MR) model, the nBi-doped 6MR models are constructed for studying geometric and optical properties. With the quantity of monovalent bismuths increasing from one to three in 6MR model, the optical absorption intensity showed a trend of first increase and then decrease. The transition energy levels of monovalent bismuth-related model are studied with the time-dependent density functional theory (TDDFT). Our results showed that the 3P1 → 3P0 transition of Bi + ion gives rise to near-infrared (NIR) luminescence around 1270 nm.

Assessment of Cracking in Masonry Structures Based on the Breakage of Ordinary Silica-Core Silica-Clad Optical Fibers

This paper presents a study on the suitability and accuracy of detecting structural cracks in brick masonry by exploiting the breakage of ordinary silica optical fibers bonded to its surface with an epoxy adhesive. The deformations and cracking of the masonry specimen, and the behavior of pilot optical signals transmitted through the fibers upon loading of the test specimen were observed. For the first time, reliable detection of structural cracks with a given minimum value was achieved, despite the random nature of the ultimate strength of the optical fibers. This was achieved using arrays of several optical fibers placed on the structural element. The detection of such cracks allows the degree of structural danger of buildings affected by earthquake or other destructive phenomena to be determined. The implementation of this technique is simple and cost effective. For this reason, it may have a broad application in permanent damage-detection systems in buildings in seismic zones. It may also find application in automatic systems for the detection of structural damage to the load-bearing elements of land vehicles, aircraft, and ships.

Fabrication of anodic aluminum oxide on silica optical fiber with nanopore channels oriented off surface normal

AbstractAluminum coating on silica optical fiber was anodized by applying an electric field off‐axis to surface normal of the fiber coating with simulation of the electric field lines between angularly positioned anode and cathode as a guide. The nanostructure features, including nanopore orientation, of the resultant anodized aluminum oxide (AAO) were characterized using scanning electron microscopy. This unique off‐axis electric field arrangement enabled the formation of AAO with uniformly tilted nanopore channel arrays. Nanopore channels with tilting angles around 10°–20° relative to surface normal of AAO were obtained. These results are in general agreement with the simulated electric field lines between the anode and cathode.

A Panda fiber temperature sensor up to 900°C

The use of Panda-type polarization-maintaining (PM) fiber for the localized sensing of high temperatures was analyzed with simulations and experiments up to 900°C. Accuracy and repeatability of the results started to decline above 800°C. Fused silica optical fiber melts at 1700°C, which sets an ultimate limit for measurable temperatures. In practice, optical fiber birefringence restricts the maximum temperature to 1060°C where PM fiber loses its ability to maintain polarization. Three sensor fibers (4, 5 and 10 cm long) were spliced at 45° angles to input/output fibers and calibrated in an oven from room temperature to 850–900°C temperature range. Two superluminescent light-emitting diodes (SLEDs) were coupled together as a broadband light source. Birefringence-induced change of the polarization in the sensor fiber was measured with a polarization splitter and an optical spectrum analyzer (OSA) as a function of the wavelength. Temperature-dependent birefringence generates a sinusoidal reflection spectrum from the input polarization mode to the orthogonal output polarization mode. Temperature changes could be concluded from variations in these spectra. Finally, a small fusion device, NORTH, at DTU, Denmark was successfully used as a testbed to make sure that the sensors can handle transportation and the instrumentation required for vacuum operation and still produce sensible data from a harsh environment.

A cross-validation study of Ge-doped silica optical fibres and TLD-100 systems for high energy photon dosimetry audit under non-reference conditions

This study compares the practicality of Ge-doped silica optical fibres as a potential remote dosimeter for radiotherapy postal dosimetry audit in non-reference conditions with a commercial thermoluminescence dosimeter (TLD-100). The optical fibre system consists of two types of fibres: cylindrical (CF) and flat fibres (FF). The dosimetric characteristics of the systems were investigated and compared, with particular attention to dose linearity, energy dependence, reproducibility, and fading. Measurements of absorbed doses of CF, FF, and TLD-100 were made, along with uncertainty budgets. A preliminary test was performed under non-reference conditions to evaluate the variations in absorbed doses measured with CF and FF versus TLD-100. For both 6 MV and 10 MV photon beams, CF, FF, and TLD-100 show a linear dose-response from 1 Gy to 3 Gy with a coefficient of determination (R2) greater than 0.99, minimal energy dependence, and good reproducibility with less than 3% deviation. The highest fading rates were 37.6%, 63.4%, and 14.2% for CF, FF, and TLD-100, respectively, at day 106 after irradiation. For irradiation with a photon beam of 6 MV, the combined relative standard uncertainty of absorbed dose determined from CF, FF, and TLD-100 measurements was estimated to be 4.3%, 5.56%, and 0.74%, respectively. Preliminary absorbed dose measurement tests under non-reference conditions showed that the mean ratios of Ge-doped silica optical fibres to TLD-100 for on-axis dose, wedge transmission, and output factor were 1.014, 0.991, and 1.013, respectively. The Ge-doped silica optical fibre systems have dosimetric performance commensurate with the TLD-100 and can be used as a potential remote dosimeter for mailed dosimetry audits if appropriate correction factors are applied to the absorbed dose measurements.

Thermally drawn multifunctional fibers: Toward the next generation of information technology

AbstractAs the fundamental building block of optical fiber communication technology, thermally drawn optical fibers have fueled the development and prosperity of modern information society. However, the conventional step‐index configured silica optical fibers have scarcely altered since their invention. In recent years, thermally drawn multifunctional fibers have emerged as a new yet promising route to enable unprecedented development in information technology. By adopting the well‐developed preform‐to‐fiber manufacturing technique, a broad range of functional materials can be seamlessly integrated into a single fiber on a kilometer length scale to deliver sophisticated functions. Functions such as photodetection, imaging, acoustoelectric detection, chemical sensing, tactile sensing, biological probing, energy harvesting and storage, data storage, program operation, and information processing on fiber devices. In addition to the original light‐guiding function, these flexible fibers can be woven into fabrics to achieve large‐scale personal health monitoring and interpersonal communication. Thermally drawn multifunctional fibers have opened up a new stage for the next generation of information technology. This review article summarizes an overview of the basic concepts, fabrication processes, and developments of multifunctional fibers. It also highlights the significant progress and future development in information applications.image

A Review of Apta-POF-Sensors: The Successful Coupling between Aptamers and Plastic Optical Fibers for Biosensing Applications

Aptamers represent the next frontier as biorecognition elements in biosensors thanks to a smaller size and lower molecular weight with respect to antibodies, more structural flexibility with the possibility to be regenerated, reduced batch-to-batch variation, and a potentially lower cost. Their high specificity and small size are particularly interesting for their application in optical biosensors since the perturbation of the evanescent field are low. Apart from the conventional plasmonic optical sensors, platforms based on silica and plastic optical fibers represent an interesting class of devices for point-of-care testing (POCT) in different applications. The first example of the coupling between aptamers and silica optical fibers was reported by Pollet in 2009 for the detection of IgE molecules. Six years later, the first example was published using a plastic optical fiber (POF) for the detection of Vascular Endothelial Growth Factor (VEGF). The excellent flexibility, great numerical aperture, and the large diameter make POFs extremely promising to be coupled to aptamers for the development of a sensitive platform easily integrable in portable, small-size, and simple devices. Starting from silica fiber-based surface plasmon resonance devices, here, a focus on significant biological applications based on aptamers, combined with plasmonic-POF probes, is reported.

Mode Coupling and Steady-State Distribution in Multimode Step-Index Organic Glass-Clad PMMA Fibers

Mode coupling and power diffusion in multimode step-index (SI) organic glass-clad (OGC) PMMA fiber is examined in this study using the power flow equation (PFE). Using our previously proposed approach we determine the coupling coefficient D for this fiber. When compared to standard multimode SI PMMA fibers, the multimode SI OGC PMMA fiber has similar mode coupling strength. As a result, the fiber length required to achieve the steady-state distribution (SSD) in SI OGC PMMA fibers is similar to that required in standard SI PMMA fibers. We have confirmed that optical fibers with a plastic core show more intense mode coupling than those with a glass core, regardless of the cladding material. These findings could be valuable in communication and sensory systems that use multimode SI OGC PMMA fiber. In this work, we have demonstrated a successful employment of our previously proposed method for determination of the coupling coefficient D in multimode SI OGC PMMA fiber. This method has already been successfully employed in the previous research of mode coupling in multimode SI glass optical fibers, SI PMMA fibers and SI plastic-clad silica optical fibers.

Real-time measurement of parametric influences on the refractive index and length changes in silica optical fibers.

In this paper, we present a simple cascaded Fabry-Perot interferometer (FPI) that can be used to measure in real-time the refractive index (RI) and length variation in silica optical fibers caused due to external physical parameters, such as temperature, strain, and radiation. As a proof-of-concept, we experimentally demonstrate real-time monitoring of temperature effects on the RI and length and measure the thermo-optic coefficient (TOC) and thermal expansion coefficient (TEC) by using the cascaded FPI within a temperature range of 21-486°C. The experimental results provide a TEC of 5.53 × 10-7/°C and TOC of 4.28 × 10-6/°C within the specified temperature range. Such a simple cascaded FPI structure will enable the design of optical sensors to correct for measurement errors by understanding the change in RI and length of optical fiber caused by environment parameters.