Single-mode Optical Fiber Research Articles

Temperature Dependence of Radiation Induced Attenuation of Aluminosilicate Optical Fiber

We investigated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> the temperature influence on X-ray radiation-induced attenuation (RIA) levels and kinetics of an Al-doped single-mode optical fiber (OF) in the visible (vis) and near-infrared (NIR) spectral domains (400 nm– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu \text{m}$ </tex-math></inline-formula> , from room temperature (RT) up to 300 °C). The RIA spectra in the visible show no significant variation up to 200 °C. Above this temperature, the induced losses begin to decrease. The NIR RIA, on the other hand, appears to be more temperature-dependent, showing a monotonic decrease with increasing temperature throughout the whole investigated range. By studying the RIA growth kinetics at 1550 nm at the various temperatures, a linear dependence was found between the RIA levels and doses at which a steady state is reached, suggesting a direct generation process of the induced defects. Finally, the combination of the measurements led to the attribution of the RIA in the NIR domain to a single absorption component, whose generation process is correlated with the defects absorbing in the visible and characterized by a continuum of absorption states.

Enhancement of single-mode optical fiber quality factor-bit error rate by using uniform fiber Bragg grating

The properties of optical fibers transmission systems based on Bragg gratings and uniform fibers, which are discussed in detail in this paper. Two - fiber optic communication channels Bragg gratings are used, along with Optisystem software for simulations. It is widely used in a variety of optical communication systems, such as, dispersion compensators, band filters, amplifiers and in - fiber sensors or fiber grating lasers, because of its versatility. In this design, the distance has been changed from 10 km up to 100 km, as well as the input power from 2 dBm to 16 dBm, and the calculation of both the bit error rate (BER) and quality (Q) f actor at the receiver could be studied by modelling the model of a communication system and employing the syste m's most suited settings, such as fiber cable length (km) and input power (dBm).

INVESTIGATION OF THE TEMPERATURE DEPENDENCE OF TFBG WITH TILT ANGLES OF 20 AND 40

Due to advantages such as electromagnetic stability, durability, and high sensitivity, fiber Bragg gratings have found application as sensors of physical quantities. A special place in the line of such devices is occupied by Bragg gratings with tilted strokes (Tilted fiber Bragg grating- TFBG). At the moment, TFBGs are used to estimate the velocity of two-phase flows, to create a torsion sensor, as temperature and deformation sensors, etc. This article examines the possibility of implementing a temperature sensor based on TFBG with an angle of inclination of 2° and 4° inscribed in a single-mode optical fiber. For this purpose, experimental studies of the dependence of the wavelength of the Bragg resonance on temperature have been carried out. The grating period is 540 nm and the length is 10 mm. The temperature ranged from 30 °C to 85 °C in increments of 5 degrees. The results of the experiment are to find a linear dependence of the minimum wavelength of the Bragg resonance λB on the change in ambient temperature.

Influence of surface roughness on the sensitivity of a D-shaped optical fiber-based refractive index sensor

This paper presents the evaluation of the influence of surface roughness on the performance of a refractive index sensor based on a D-shaped optical fiber. In addition, the manufacturing process of D-shaped sections on standard silica single-mode optical fibers with different rms roughness values is described. The surface roughness morphology generated by the abrasive process is measured by processing microscopic images using the Gwyddion software. A model for the surface roughness, using the third order Weierstrass fractal function, is proposed and simulated with COMSOL Multiphysics. Experimental and simulation results are presented. The results show that the surface roughness increases the device insertion loss, as expected, but contributes positively to the sensitivity of the refractive index sensor, reaching sensitivity levels of 148.87 dB/RIU with a resolution of 10−4 RIU. The good agreement between the computational and experimental results is highlighted. Due to the good figures of merit obtained, the optical sensor has potential of application in biochemical sensing.

A cascaded FBG scheme based OQPSK/DPSK modulation for chromatic dispersion compensation

The aim of this study is to present a proposed chromatic dispersion compensation model for single mode optical fiber. The proposed model consists of 4-stages of cascaded identical linear chirped fiber Bragg grating (CFBG) in post-compensation connection scheme. It is based on differential phase shift keying modulation format. To evaluate the performance of the proposed model, a comparative study is conducted using offset quadrature phase shift keying modulation technique. This comparative study includes four cases with and without using CFBG. For system performance evaluation, a 10 Gbps wavelength division multiplexing link is simulated at a distance of 70 km under conventional operating parameters. Optisystem 7.0 has been used for simulation and evaluation process. Quality factor (Q-factor) and bit error rate (BER) are used as evaluation metrics. The proposed model shows the best performance in case of using CFBG compared to the other cases. A maximum Q-factor of 7.22, and a corresponding minimum BER of 2.59 × 10−13are obtained. The proposed system performance is enhanced by at least 53% as compared to related work.

Demonstration of Coherent Interference between Acoustic Waves Using a Fiber Ring Resonator.

Optical fibers were previously demonstrated to propagate and detect acoustic modes that were converted from Lamb waves for structural health-monitoring applications; typically, a fiber Bragg grating sensor in the optical fiber is used to detect acoustic modes. Acoustic modes can transfer from one fiber to another through a simple adhesive bond coupler, preserving the waveform of the acoustic mode. This paper experimentally investigates the coherence of acoustic waves through the adhesive coupler, using a fiber ring resonator (FRR) configuration. This configuration was chosen because the wave coupled to the second fiber interferes with the original wave after it encircles the fiber ring. We performed this experiment using different geometries of optical fibers in the ring, including a standard single-mode optical fiber, a hollow silica capillary tube, and a large-diameter multi-mode fiber. The results demonstrate that the acoustic wave, when transferring through an adhesive coupler, interferes coherently even when the main and ring fibers are of different types. Finally, we demonstrate that the FRR can be applied for sensing applications by measuring the mode attenuations in the ring due to a changing external environment (water-level sensing) and measuring the optical-path length change in the ring (temperature sensing).

Closed-loop MOEMS accelerometer.

In this paper, a closed-loop micro-opto-electro-mechanical system (MOEMS) accelerometer based on the Fabry-Pérot (FP) interferometer is presented. The FP cavity is formed between the end of a cleaved single-mode optical fiber and the cross-section of a proof mass (PM) which is suspended by four U-shaped springs. The applied acceleration tends to move the PM in the opposite direction. The arrays of fixed and movable comb fingers produce an electrostatic force which keeps the PM in its resting position. The voltage that can provide this electrostatic force is considered as the output of the sensor. Using a closed-loop detection method it is possible to increase the measurement range without losing the resolution. The proposed sensor is fabricated on a silicon-on-insulator wafer using the bulk micromachining method. The results of the sensor characterization show that the accelerometer has a linear response in the range of ±5 g. In the closed-loop mode, the sensitivity and bias instability of the sensor are 1.16 V/g and 40 µg, respectively.

Parabolic microlensed optical fiber for coupling efficiency improvement in single mode fiber

The efficiency of optical coupling between an optical fiber and other components be it a light source, a photodetector or another fiber, often depends on the performance of the focusing components. In optoelectronics, microlenses are generally incorporated at the end of optical fibers to ensure optimal coupling. These microlenses are primarily fabricated with a spherical profile easier to achieve, with a determined radius and at low production costs. However, these microlenses exhibit a relatively large waist due to intrinsic spherical aberrations making it difficult to couple light into single mode fibers. This paper presents the results of a study of a microlens having a parabolic profile that has been made of polydimethylsiloxane (PDMS) at a single mode optical fiber (SMF 9/125) end terminal. The contribution of the parabolic profile as compared to spherical shaped one is analyzed. Estimates at the wavelengths of primary importance, λ =1.310 µm and λ =1.550 µm, have shown a decrease in the spot radius diagram in the focal plane by 3, from an root mean square (RMS) value of 0.623 µm in the spherical case to less than 0.229 µm in the parabolic case. The measured optical coupling has improved to 98.5% under optimal conditions (without taking into account the bulk absorption and the effects of Fresnel reflection). For different studied microlens curvatures’ radii, the obtained waist values vary from 1.00 to 4.90 µm with working distances from 5.80 to 48.80 µm, respectively.

Digital OPLL-based distributed Brillouin sensing system in optical fibers.

A digital optical phase-locked loop (OPLL) has been implemented to develop a distributed Brillouin sensing system in optical fibers. In our experiment, two commercial semiconductor lasers are phase-locked to each other with a highly flexible offset frequency using field programmable gate array (FPGA)-based electronics. Then, the difference frequency between the two lasers is highly stabilized and scanned by a desired step frequency in the vicinity of the Brillouin frequency of standard single-mode optical fibers. Consequently, the distribution of Brillouin frequency shift over a 50 km-long sensing fiber has been successfully measured by a very simple and low-cost Brillouin optical time-domain reflectometry (BOTDR) sensing system without any penalty in the sensing performance. The measurement repeatability at 50 km position of sensing fiber with a 5 m spatial resolution was measured be 4.5 MHz under fast measurement conditions: the number of trace averaging of 2000 and the frequency scan step of 12.8 MHz, showing the figure-of-merit of 3.0.

Wavelet convolutional neural network for robust and fast temperature measurements in Brillouin optical time domain reflectometry.

In this paper, a wavelet convolutional neural network (WNN) consisting of a one-dimensional (1D) convolutional neural network and a self-adaptive wavelet neural network has been proposed and demonstrated experimentally for temperature measurement in a Brillouin optical time domain reflectometry (BOTDR) system. Based on the analysis of the system noise, it follows the Gaussian white noise distribution along the time-related sensing distance. The impact of the noise in time-domain on the measured Brillouin gain spectra (BGSs) could be neglected, so that the BGSs in the fiber can be regarded as a series of 1D input data of the proposed WNN. Different self-adaptive wavelet activation functions connected to each output of the full-connection network are adopted to realize the multi-scaled analysis and the scale translation, which can obtain more local characteristics in frequency-domain. The output extracted by the WNN is Brillouin frequency shift (BFS), which presents linearity correlation to the actual temperature. Considering the multi-parameters including different frequency ranges, signal-to-noise-ratios (SNRs), BFSs and spectral widths (SWs), a general model of the proposed WNN is trained to handle more extreme cases, in which it doesn't require retraining for different single-mode (SM) optical fibers in BOTDR sensing system. The performances of the WNN are compared with other two techniques, the Lorentzian curve fitting based on Levenberg-Marquardt (LM) algorithm and the basic neural network (NN) containing input and output layers together with two hidden layers. Both the simulated and measured results show that the WNN has better robustness and flexibility than the LM and the NN. Besides, the computational accuracy of the WNN is improved and the fluctuation of that is slighter, especially when the SNR is less than 11 dB. Moreover, the WNN takes approximately 0.54 s to measure the temperature from the 18,000 collected BGSs transmitted through the 18 km SM optical fiber. The calculating time of the WNN is greatly reduced by three orders of magnitude in comparison with that of the LM, and is comparable to that of the NN. It proves that the proposed WNN may provide a feasible or even better scheme for the robust and fast temperature measurement in BOTDR system.

Dual-Parameter Sensing With a Single Supermode Interferometer

Optical fiber interferometers have intrinsic sensitivity to temperature, thus, in sensing applications; they need a reference temperature sensor or a mechanism to control the temperature. Here, we demonstrate that a single multicore fiber interferometer can monitor two parameters simultaneously; more particularly, refractive index, and temperature. The interferometer is easy to manufacture; a short segment of an optical fiber with seven coupled cores is fusion spliced at the distal end of a conventional single mode optical fiber. In the coupled-core fiber, two supermodes beat; this makes the reflection spectrum of the device to exhibit a well-defined series of maxima and minima. The refractive index of a sample in contact with multicore fiber alters the amplitude of the interference pattern and temperature induces a shift to such a pattern. The changes of the interference pattern are easy to monitor and decode with a low-resolution spectrometer. As an application of our dual-parameter sensor, the thermo-optic coefficient of a sample was measured.

Highly Sensitive Air Pressure Sensor Based on Fabry-Perot Interference

A highly sensitive optical fiber air pressure sensor based on Fabry–Perot interferometer is proposed and demonstrated. The sensor is fabricated by flat-cut single-mode optical fiber, capillary glass tube, stainless steel sleeve, nylon substrate, and metal aluminum film. The finite element simulation was performed in two steps using the COMSOL Multiphysics software. In the first step, the structural mechanics module is used to simulate the deformation of the membrane under a fixed pressure, so as to obtain the corresponding sensor cavity lengths under different pressure. In the second step, the wave optics module is used to get the reflection spectrum of the sensor under different cavity lengths. Then the linear relationship between the reflection spectral shift of the sensor and the pressure is obtained. Thus, the average spectral sensitivity of the sensor under air pressure is −3.10335 nm/KPa. A metal-aluminum thin film F-P cavity sensor was fabricated for experimental verification. According to the experimental results, when the air pressure ranges from 0 Pa to 1000 Pa, the spectral sensitivity of the sensor is as high as −3.10 nm/KPa. This is almost consistent with the simulation result. The sensor has exhibited potential application in the fields of measurement of airway pressure and environmental monitoring.

Generation of stable temporal doublet by a single-mode silicon core optical fiber

A highly nonlinear single mode anomalous dispersion silicon-core fiber is designed and optimized at the operating wavelength of 2.2 µm for the purpose of generating stable temporal pulse doublets. To designate the output pulse pair as a perfect Gaussian doublet, two new parameters, dissimilarity factor () and co-similarity index (μ cs) are introduced. Different input pulse parameters such as power, pulse width and chirp are optimized to obtain Gaussian temporal doublets at the shortest optimum length (∼few cm) which is sufficiently smaller in comparison to silica fibers reported earlier. The output pulse pairs remain as a doublet for quite a good stability length. In view of serving practical purposes, the possibilities of fluctuations of input power and pulse width are included to investigate the changes in stability length and effective repetition rate (ERR). The change in ERR along the fiber length produces a remarkable change in free carrier concentration in core, which has also been taken into account for the first time as per our knowledge to obtain the temporal pulse doublet in the so designed Si-core fiber.

Evaluation of gamma response ability of single-mode and multi-mode optical fibers with different dopants as dosimeter sensors

Optical fiber is used as a tool for data transmission in radiation environments in many applications such as medical, plasma diagnostics, and space satellites. The optical transmission is affected by ionizing radiation, characterized by radiation-induced attenuation. This feature allows use as a dosimeter sensor. In this work, the gamma radiation responses of three types of single-mode and multi-mode fibers, with different dopants of erbium (Er), germanium (Ge), and phosphorus (P) were evaluated. Radiation-induced attenuation was measured by spectrophotometer in wavelength ranges of 400–700 nm. The Er-doped fiber had higher attenuation of 0.8 dB/m after 560 mGy total dose. There was a reasonable linear relationship between the amount of attenuation and absorbed dose in P-, Ge-, and Er-doped fibers.

Compact fiber-integrated scattering device based on mixed-phase TiO2 for speckle spectrometer.

A universal, repeatable, and controllable integration of single-mode optical fiber and mixed-phase TiO2 is used to manufacture a compact fiber-integrated scattering device. Based on the device, we achieve a high-performance and compact fiber-based speckle spectrometer, which has a resolution of 20 pm over a bandwidth of 15 nm, in the 1550 nm range. We test the capability of our proposed spectrometer to reconstruct narrow linewidth and broadband optical spectrums, and compare the performance with that of a traditional optical spectrum analyzer.

Infinity additive manufacturing of continuous microstructured fiber links for THz communications

In this work, a novel infinity 3D printing technique is explored to fabricate continuous few-meter-long low-loss near-zero dispersion suspended-core polypropylene fibers for application in terahertz (THz) communications. Particular attention is paid to process parameter optimization for 3D printing with low-loss polypropylene plastic. Three microstructured THz fibers were 3D printed using the standard and infinity 3D printers, and an in-depth theoretical and experimental comparison between the fibers was carried out. Transmission losses (by power) of 4.79 dB/m, 17.34 dB/m, and 11.13 dB/m are experimentally demonstrated for the three fibers operating at 128 GHz. Signal transmission with bit error rate (BER) far below the forward error correction limit (10–3) for the corresponding three fiber types of lengths of 2 m, 0.75 m, and 1.6 m are observed, and an error-free transmission is realized at the bit rates up to 5.2 Gbps. THz imaging of the fiber near-field is used to visualize modal distributions and study optimal fiber excitation conditions. The ability to shield the fundamental mode from the environment, mechanical robustness, and ease of handling of thus developed effectively single-mode high optical performance fibers make them excellent candidates for upcoming fiber-assisted THz communications. Additionally, novel fused deposition modeling (FDM)-based infinity printing technique allows continuous fabrication of unlimited in length fibers of complex transverse geometries using advanced thermoplastic composites, which, in our opinion, is poised to become a key fabrication technique for advanced terahertz fiber manufacturing.

Optical fiber sensor network integrating SAC-OCDMA and cladding modified optical fiber sensors coated with nanomaterial

Three modified single mode optical fiber ammonia sensors coated with nanocomposite of polyaniline/graphite nanofiber (PANI/GNF) are integrated with optical code division multiple access utilizing spectral amplitude coding (SAC-OCDMA) optical fiber sensors network. The sensors are modified using both etching and tapering processes. A thin layer of PANI/GNF is spared on the etched–tapered SMF sensors. The sensors based on the evanescent wave absorption are investigated by measuring the output optical power in the C-band wavelength range (1535–1560 nm) at room temperature. SAC-OCDMA using Khazani Syed (KS) code is deployed as it has the capability to remove multiple access interference (MAI) and it is cost effective. The performance of the developed optical fiber sensor network based on star topology is investigated remotely over 3 km using Erbium doped fiber amplifier for NH3 sensing in terms of received optical power, crosstalk, and optical signal-to-noise ratio (OSNR). OSNR is observed to vary with fiber diameter and NH3 concentration level. The smaller tapering diameter and higher NH3 concentrations generate lower OSNR at the output of the related decoder. The measured OSNR for the developed optical fiber sensor network was 22 and 18.45 dB when sensors implied in the network exposed to 0.125% and 1% NH3 concentrations, respectively.

Experimental demonstration of optical Vernier effect by cascading tapered single-mode optical fibres

An experimental demonstration of the optical Vernier effect (OVE) achieved by cascading tapered single-mode optical fibres (SMF28) is presented. The tapered optical fibres conform to a pair of Mach–Zehnder fibre interferometers (MZFIs) with slightly different free spectral ranges. Three different experiments with MZFIs in tandem were carried out to evaluate the OVE characteristics such as the magnification and free spectral range of the envelope. The displacement/curvature sensor exhibited a sensitivity of 0.069 nm/µm (∼84.2 nm/m−1) in the displacement/curvature range of 250–500 µm (∼0.12–0.24 m−1) with a magnification of 8.84. A brief comparison to other OVE-based curvature sensors is presented.

Determination of the Mandelstam – Brillouin Scatter Frequency Characteristic in Optical Fibers of Various Types

The results of researches of the Mandelstam – Brillouin scattering frequency characteristics in single-mode optical fibers of various types are presented in this paper. A technique for obtaining the spectral characteristics of Mandelstam – Brillouin scattering for predefined acoustic mode distributions in single-mode optical fibers is considered. The procedure for determining the frequency characteristics of the Mandelstam – Brillouin scattering for a given structure of the radial distribution of the optical fiber refractive index is discussed. The Mandelstam – Brillouin scattering frequency characteristics of single-mode optical fibers obtained by mathematical modeling and experimental studies are presented. A comparative analyze of obtained results is carried out.

Research of the Optical Fibers Structure Influence on the Acousto-Optic Interaction Characteristics and the Brillouin Scattering Spectrum Profile

The research results of the structure influence of single-mode optical fibers of various types on the interaction characteristics of the optic and acoustical modes of lower orders are presented in this work. A method for obtaining of optic and acoustical modes distribution in single-mode optic fibers is considered. The structures of the radial distribution of refractive index profiles for some varieties of single-mode optical fibers with dispersion shift (ITU–T recommendation G.653 and G.653) are presented. The obtained graphs for varieties of optical fibers are presented.