Single-mode Optical Fiber Research Articles

Modulating anti-dark vector solitons

Theoretical analysis of the modulation of anti-dark vector solitons is conducted in this work. The simulation depends on a single-mode optical fiber out-cavity modulation system model that works at 1 μm. The anti-dark vector soliton’s initial state is assumed to be polarization-/group-velocity-locked, with same/different central wavelengths in orthogonally polarized directions. After soliton parameter modulation, modulated anti-dark vector solitons at the output port will demonstrate different properties in orthogonal directions. For example, two symmetrically located frequency peaks always exist for output orthogonal modes when the input state is polarization-locked. And a dual-wavelength anti-dark vector soliton with temporal pulse oscillation can be generated by changing the projection angle with the help of a polarization beam splitter, when the input vector soliton’s group-velocity is locked. These modulation results are instructive for the study of out-cavity modulating optical fiber vector soltions with different pulsed properties.

Моделирование влияния деформации изгиба в одномодовом оптическом волокне на показатель преломления сердечник – оболочка

Рассматривается модель деформированного одномодового оптического волокна. Приводится математическая модель деформационных составляющих. Произведена оценка показателей преломления в трех взаимно перпендикулярных направлениях. Найдены случаи, в которых распространение света по изогнутому волокну происходит как по одноосному кристаллу. Определено, что значения показателя преломления изогнутого оптического волокна отличаются от показателя преломления недеформированного волокна. The article addresses the model of a deformed single-mode optical fiber. A mathematical model of deformation fibers is given. Cases have been found where the propagation of light along a bent fiber occurs as though along a uniaxial crystal. A certain value of the refractive index of a bent optical fiber differs from the refractive index of the undeformed fiber.

The Impact of Gamma Irradiation on Optical Fibers Identified Using Long Period Gratings

This paper compares the impact of gamma irradiation on various optical fibers, where the evolution in their optical properties could be identified using long period gratings (LPG) there induced. The LPGs were fabricated in broad spectrum of commercially available single-mode optical fibers - from standard to unconventional ones - using the electric arc discharge method. The fused silica fiber material contained such dopant as Ge, F, B/Ge and P. The gamma exposure has been performed with a dose rate of 2.6 kGy/h for 20 h (a total dose of 52 kGy). Subsequently, the recovery effect was monitored during the following 48 h. The wavelength shift and power change of the LPG attenuation bands during irradiation were investigated in real time. Moreover, to identify the impact of gamma treatment on the fiber properties, the thermal response of the gratings was studied before and after the irradiation. Depending on the fiber, significant differences have been observed in the grating responses. The highest radiation-dependent resonance wavelength shift has been found for B/Ge fiber (∼10 nm at maximum dose). Moreover, for these LPGs no response saturation within the applied dose levels has been observed together with very low recovery effect, what differentiate these LPGs from the other tested in this experiment. Finally, concerning the changes in optical power at the resonance wavelength, the LPG induced in P-doped fiber has shown a strong irradiation-induced attenuation reaching 18 dB with a negligible recovery effect. The findings reported in this work are crucial for optical fiber and optical fiber sensors application in environments exposed to radiation.

Core multi-layer dispersion on single-mode optical fiber

Optical technology has experienced extraordinary developments in recent years and the development of optical fibers continues to be carried out for various applications, namely optical sensors, long-distance communications, and health monitoring so that they can be applied in monitoring high temperatures in petroleum plants. Optical fiber has properties that cannot interfere with electromagnetic waves, which is an advantage compared to conventional cables besides optical fibers are able to transmit data quickly and reach very far across continents. However, the signal in the optical fiber that is carried in the form of pulses can experience widening, this widening is a result of changes in the refractive index, constituent materials, and losses due to fiber optic connection which will decrease the quality of the received signal. One way to reduce the pulse widening in a single-mode optical fiber is to split the fiber core into several layers to obtain zero dispersion in the single-mode optical fiber. Another thing is that we can influence the effect of the inner layer of the fiber core on the desired zero dispersion. After designing the optical core by making several layers, it was found that the dispersion was not found in the 6 and 7 core layers while the fibers with layers 2, 3, 4, and 5 had different wavelengths for zero dispersion. Furthermore, the effective area or area that is passed by the optical signal and the largest fiber mode diameter is obtained on 3-layer fibers with a value of 230.0454 mm2 and 17.1144 mm each seen from the delay of layer groups 2, 5, 6, and 7 experiencing a group decline for each wavelength while fiber With layers 3 and 4 experiencing an increase in group delay from the experimental data it was found that cores with 6 and 7 layers would not find the desired zero dispersion while optical fibers with the best layers transmit signals were cores with 3 layers.

Design considerations and experimental investigations on fiber ball lens systems for optical metrology

Optical fibers play an important role in general and, in particular, in the field of sensors. As part of a sensor system, quite often fibers are coupled by a ball lens. For efficient usage, the fiber ball lens systems (FBLSs) have to be optimized. The present work presents analytic expressions for the design parameters of such systems. FBLSs comprise sections of a single-mode optical fiber, a coreless fiber (CLF) and a ball lens. Their geometric dimensions have to be optimized for their use in different applications in optical metrology. The derived expressions facilitate the optimum parameter choice, which is usually done by expensive numerical simulations. For comparison and validation of the results by experiments, FBLSs with different ball lens radii and CLF sections have been prepared by a fusion splicer technique. Their characteristics were investigated in the optical spectral ranges at 630 nm and 1550 nm. Experimental methods comprising far-field, near-field and reflection/transmission measurements with optical fibers validate the theoretical considerations. To our knowledge, this is the first time that simple analytic approaches have been applied to the fabrication of FBLSs. This facilitates and quickens their general design for different applications in optical metrology significantly.

Effect of multilayered coating of single-mode optical fibers on distributed temperature and strain measurement in mortar specimens

This study aims to characterize the effects of multilayered coatings on the performance of distributed fiber optic sensors (DFOS) when the coatings experience softening and melting at high temperatures. Two strain sensors (B-DFOS and W-DFOS) and one temperature sensor (Y-DFOS) were calibrated. They were either embedded along the centerline of a mortar bar or bonded on the surface of the specimen. The Y-DFOS was found to be no longer strain-free at high temperature since the softened sheath, aramid yarns, buffer, and polymer coatings became viscous and adhered to their surrounding mortar above softening temperatures 263–320 °C. Both the B-DFOS and W-DFOS captured uneven strain distributions along the mortar specimen due to non-uniform temperature distribution, mortar heterogeneity, and temperature-dependent strain transfer efficiency. The W-DFOS showed higher measured strains than the calculated thermal-induced strains at 100 °C - 300 °C due to the high thermal expansion coefficient of the additional buffer layer. The B-DFOS gave smaller measured strains than the thermal-induced strains at 300 °C - 500 °C. The displacement calculated by integrating the measured strains along the length of each mortar specimen was related to the applied temperature by parabolic regression equations.

Study of the Feasibility of Decoupling Temperature and Strain from a ϕ-PA-OFDR over an SMF Using Neural Networks.

Despite several existing techniques for distributed sensing (temperature and strain) using standard Single-Mode optical Fiber (SMF), compensating or decoupling both effects is mandatory for many applications. Currently, most decoupling techniques require special optical fibers and are difficult to implement with high-spatial-resolution distributed techniques, such as OFDR. Therefore, this work's objective is to study the feasibility of decoupling temperature and strain out of the readouts of a phase and polarization analyzer OFDR (ϕ-PA-OFDR) taken over an SMF. For this purpose, the readouts will be subjected to a study using several machine learning algorithms, among them Deep Neural Networks. The motivation that underlies this target is the current blockage in the widespread use of Fiber Optic Sensors in situations where both strain and temperature change, due to the coupled dependence of currently developed sensing methods. Instead of using other types of sensors or even other interrogation methods, the objective of this work is to analyze the available information in order to develop a sensing method capable of providing information about strain and temperature simultaneously.

Mid-infrared refractive index sensor with high sensitivity and wide detection range based on multimode interference in tellurite optical fibers

In this paper, a section of tellurite no-core optical fiber (NCF) is compactly sandwiched between two segments of tellurite single-mode optical fibers (SMF) to form multimode interference (MMI) sensor for refractive index (RI) measurement. Theoretical investigation reveals that the sensitivity of this MMI-based RI sensor can be enhanced by reducing the diameter of the NCF. As the NCF diameter is lowered to 20 µm, the sensor presents good RI sensing performance in the mid-infrared range of 2–5 µm and the sensitivity rises with the increase of the wavelength. At 4–5 µm and within the detectable RI range of 1.36–1.63, the maximum sensitivity is 3069.1 nm/RIU. The proposed sensor combines the material superiority of tellurite glass and the structural advantage of the SMF-NCF-SMF sensing unit, exhibiting high sensitivity and wide detection range in terms of RI sensing. It provides a new method for detecting the concentration of toxic organic compounds with high RI.

Low‐Temperature Synthesis of Silicon Oxynitride‐Doped Si for Tunable Bragg Gratings Homogeneously Deposited on Si, SiO2, and Borosilicate Substrates and the tip of SM and PM Optical Fibers (Advanced Optical Materials 12/2023)

In article number 2300094, Ali Karatutlu and colleagues describe the synthesis of silicon oxynitride-doped silicon and their use in Bragg gratings on bulk substrates and the tip of optical fibers with high reflectivity over 22 dB, including single-mode and polarization-maintaining optical fibers.

Coupling Efficiency of a Spot Size Converter for Optical Fiber-Chip Connections

The light propagation in optical waveguide must be able to maintain low propagation loss, low coupling loss and scattering loss condition, especially in the junction. In this research, a spot size converter is proposed to preserve the lowest coupling loss. This optical converter is composed of a single mode optical fiber (SiO2) including inversed taper. The optical input signal from the optical fiber is launched into photonic integrated circuits and then coupled into the Si-Slab waveguide. Furthermore, linear form with the length dependence has been studied to obtain the optimal position of optical fiber and the chip and analyzed the coupling efficiency of it. The purpose of this research is to procure the optimal form of spot size converter. The simulation result shows the coupling loss of linear form is 0.62 dB and 0.24 dB on TE and TM mode condition respectively. Along with the increase in the taper length, the coupling loss obtained tends to decrease as well. So that, it can be assumed the design of a linear form with 100 μm taper length provides the highest coupling efficie ncy.

Compact highly sensitive Fabry-Perot temperature and gas pressure sensing probe fabricated by a femtosecond laser and PDMS.

A high sensitivity optical fiber temperature and gas pressure sensor with integrated micro-cavity is proposed. First, a single-mode optical fiber (SMF) is spliced with a section of capillary, and then the sensitive material polydimethylsiloxane (PDMS) is filled into the capillary to form a Fabry-Perot interferometer (FPI). Finally, a femtosecond laser is used to ablate the fiber core of the SMF to form the third reflecting surface, constituting two cascaded FPIs. When two FPIs have a similar free spectral range, a Vernier effect is produced. The temperature and gas pressure sensitivity of the sensor reached 14.41 nm/°C and 113.82 nm/MPa, respectively, after using the sensitive material and Vernier effect double sensitization technology. In addition, a fiber Bragg grating is cascaded with the sensor, which can realize the simultaneous measurement of temperature and gas pressure and eliminate cross-sensitivity.

Enhanced detection sensitivity of Leptospira DNA using a post-deposition annealed carbon quantum dots integrated tapered optical fiber biosensor

Leptospirosis is an illness caused by a Leptospira bacterial infection, and it can be fatal if not correctly diagnosed and treated. This work explores the development of an optical biosensor that utilizes tapered optical fiber integrated with post-deposition annealed carbon quantum dots (CQDs) to improve Leptospira deoxyribonucleic acid (DNA) detection. A standard optical single-mode fiber was tapered before being deposited with CQDs. The surface properties of CQDs on the tapered optical fiber were then tuned using a simple, one-step annealing process. Leptospira probe DNA was covalently bonded to the annealed CQDs surface using several commercially available linkers. The detection was achieved through probe DNA fragments that were hybridized into different concentrations of complementary target DNA. The biosensor limit of detection remained at 1.0 fM, but a better sensitivity of 2.321 ± 0.048 nm/nM was obtained. The affinity towards Leptospira complementary DNA improved as the equilibrium dissociation constant value was lowered to 0.15 х 10−9 M compared to previous studies. In non-complementary DNA reactions, a minimal wavelength shift is detected, indicating the biosensor's high specificity, whereas studies using genomic DNAs from Leptospira and Clostridium difficile (as a control for genomic DNA) revealed similar observation. The integration of CQDs has achieved these remarkable biosensor traits, which hold great potential for developing a reliable leptospirosis diagnosis.

Distributed optical strain sensing measurements down to cryogenic temperatures.

Rayleigh backscattering (RBS)-based distributed fiber sensors technology is becoming more and more crucial in various fields such as aerospace and defense, automotive, civil, and geotechnical. This technology is measuring the naturally occurring Rayleigh backscatter level in the optical fiber core; thus, any standard single-mode telecom optical fiber can be used. The application of distributed optical fiber strain sensing in the harsh environments of the European Organization for Nuclear Research required several mechanical tests to study the accuracy of strain sensing in cryogenic conditions. This study compares the performance of a RBS-based distributed optical fiber strain sensing down to cryogenic temperatures (4.2K) with previously validated instrumentations such as electrical strain gauges and fiber Bragg grating technologies.

Laser Doppler vibrometry measurements of acoustic attenuation in optical fiber waveguides.

Fiber Bragg grating (FBG) sensors have been widely applied for structural health monitoring applications. In some applications, remote bonding of the optical fiber is applied, where ultrasonic waves are coupled from the structure to the optical fiber and propagated along the fiber to the FBG sensor. The distance that this signal can propagate along the optical fiber without decaying below a threshold value can be critical to the area of the structure that can be monitored per sensor. In this paper, we develop a method to measure the acoustic mode attenuation of fiber waveguides based on laser Doppler vibrometry (LDV) that is independent of the fiber type. In order to validate the method, we compare attenuation measurements on single-mode optical fibers using both the LDV and FBG sensor methods. Once the method is validated, experimental measurements of different coated and uncoated optical fibers are performed to quantify the role of the fiber diameter on the attenuation coefficient. As the radius of the waveguide decreases, the signal attenuation increases exponentially.

Plasmonic Biosensor on the End-Facet of a Dual-Core Single-Mode Optical Fiber.

Optical biosensors target widespread applications, such as drug discovery, medical diagnostics, food quality control, and environmental monitoring. Here, we propose a novel plasmonic biosensor on the end-facet of a dual-core single-mode optical fiber. The concept uses slanted metal gratings on each core, interconnected by a metal stripe biosensing waveguide to couple the cores via the propagation of surface plasmons along the end facet. The scheme enables operation in transmission (core-to-core), thereby eliminating the need to separate the reflected light from the incident light. Importantly, this simplifies and reduces the cost of the interrogation setup because a broadband polarization-maintaining optical fiber coupler or circulator is not required. The proposed biosensor enables remote sensing because the interrogation optoelectronics can be located remotely. In vivo biosensing and brain studies are also enabled because the end-facet can be inserted into a living body, once properly packaged. It can also be dipped into a vial, precluding the need for microfluidic channels or pumps. Bulk sensitivities of 880 nm/RIU and surface sensitivities of 1 nm/nm are predicted under spectral interrogation using cross-correlation analysis. The configuration is embodied by robust and experimentally realizable designs that can be fabricated, e.g., using metal evaporation and focused ion beam milling.

Ultra-high sensitivity optical fiber Vernier photothermal sensor based on WTe2

In this paper, a novel Vernier photo-thermal optical fiber sensor based on WTe2 is proposed. The sensor is composed of a single-sided gold-plated silicon wafer and a single-mode optical fiber, and is encapsulated with a capillary tube. The air cavity and the silicon wafer cavity are cascaded to have an optical Vernier effect, and the sensitivity can be selected by adjusting the length of the air cavity. The ultra-high sensitivity of 2.53 nm mW−1 has been obtained through experiments, which has certain potential in the fields of optical imaging, detection, and sensing.

Soliton Dynamics in a Birefringent Optical Fiber

Long-distance solitons maintain their form and speed. Single mode optical fiber exhibits birefringence as a result of its asymmetric core's effect on the refractive index. The soliton pulse is broadened and chirped as it travels through a birefringent optical fiber due to many features of the fiber. Therefore, it is necessary to strike a balance between the elements influencing the transmission to guarantee minimal data loss. This work uses OptiSysten software to strike a balance between the length, effective area, soliton period, and attenuation effects that affect the performance of the soliton while employing optical fiber as a birefringent optical fiber. Based on this research, a set of values for these parameters that minimizes widening and chirping was determined. The simulation findings are compared to the mathematical and analytical combination of soliton, which is based on the coupled non-linear Schrodinger equation. Although previous works on soliton had demonstrated the impact of GVD and SPM on the transmission, this paper aids comprehension by including additional performance-affecting characteristics.

Integration of Raspberry Pi and antennas for multiplexing digital signals over a fiber optical communication system

A Fiber Optical Communication System (FOCS) is used to experimentally demonstrate the transmission of multi-channel information of two High Definition (HD) video signals and 18 digital TV channels. These signals are supplied using commercial Raspberry Pi boards and digital TV Antennas, respectively. Both digital signals and lightwaves of a couple of Distributed Feedback (DFB) lasers with wavelengths located at 1547.5 and 1552.5 nm interact with two Mach-Zehnder Intensity Modulators (MZ-IM). The resulting modulated optical signals from each modulator are combined by using an optical coupler. The combined optical field is amplified and transmitted through 30 km of single-mode optical fiber. To demultiplex the combined optical signals, a bandpass optical filter is used, then a PIN-photodetector is connected to recover HD video signals and the 18 digital TV channels. The measured electrical spectrum of the received signals shows that the transmission is performed without interference and the multi-channel information is successfully received in an HD display. The use of wavelengths with linewidths of 10 MHz and an optical fiber with a chromatic dispersion of 17 ps/nm-km allows for a maximum bit rate of approximately 11 Gbps to be achieved numerically. This result guarantees that HD video signals can be experimentally transmitted successfully with Bit Error Rate (BER) values between 10-6 and 10-15 when the optical power of lasers is tuned between 7 and 9 dBm.

Compact Harmonic Vernier Sensor Based on an In-Fiber FPI with Three Reflector System for Simultaneous Gas Pressure and Temperature Measurement.

In this work, we proposed a sensitivity-enhanced temperature sensor, a compact harmonic Vernier sensor based on an in-fiber Fabry-Perot Interferometer (FPI), with three reflective interfaces for the measurement of gas temperature and pressure. FPI consists of air and silica cavities formulated by single-mode optical fiber (SMF) and several short hollow core fiber segments. One of the cavity lengths is deliberately made larger to excite several harmonics of the Vernier effect that have different sensitivity magnifications to the gas pressure and temperature. The spectral curve could be demodulated using a digital bandpass filter to extract the interference spectrum according to the spatial frequencies of resonance cavities. The findings indicate that the material and structural properties of the resonance cavities have an impact on the respective temperature sensitivity and pressure sensitivity. The measured pressure sensitivity and temperature sensitivity of the proposed sensor are 114 nm/MPa and 176 pm/°C, respectively. Therefore, the proposed sensor combines ease of fabrication and high sensitivity, making it great potential for practical sensing measurements.

Radiation effects on Brillouin-based Sensors: Feasibility of temperature and strain discrimination using LEAF Single-Mode optical fiber

In this paper, we investigate the accessible performances in terms of strain and temperature discrimination using Brillouin Optical Time Domain Analysis (BOTDA) combined with the LEAF fiber (from Corning) when exposed to γ-rays up to doses of 1MGy(SiO2). This optical fiber offers a multipeak Brillouin Gain Spectrum (BGS) with unique dependencies of each of its peaks over temperature and strain. The discrimination capability evolution of LEAF is investigated at high γ doses and dose rates to evaluate the radiation effects on the sensing performances. Gamma irradiation leads to modifications of the LEAF BGS signature through two main effects. First, the Radiation Induced Attenuation (RIA) of this germanosilicate optical fiber limits the BGS amplitude, sensing range and capability for discrimination over BGS amplitude. Second, radiations modify the Brillouin scattering properties by slightly changing the refractive indices and the acoustic velocities of the fiber core and cladding leading to a small change in temperature and strain dependences as well as a limited Radiation Induced Brillouin Frequency Shift (RI-BFS) causing a direct error on the measured parameters. Results exhibit an overall decrease of temperature and strain uncertainties through discrimination process after 1MGy irradiation reaching 0.9°C and 29με for 0.1 MHz frequency uncertainty.