Fiber Distance Research Articles

Research on Noise Suppression in High-Speed Optical Communication Systems

With the rapid advancement of optical fiber communication technology, the speed and distance of information transmission have increased unprecedentedly. Multi-core fibers (MCF), which contain multiple cores, enable high-capacity and high-density information transmission. However, during signal transmission, four-wave mixing (FWM) and intercore crosstalk (ICXT) noise are generated, significantly impacting signal propagation quality. Based on the characteristics of FWM and ICXT noise, two effective noise suppression schemes are proposed. The first scheme involves reducing noise power by increasing the wavelength interval or using non-equally spaced wavelengths to mitigate phase-matching conditions. The second scheme focuses on altering the structure of the MCF; in weakly coupled MCFs, longitudinal random bending, torsion, and structural fluctuations randomly affect the power coupling coefficient. According to the noise power formula, reducing the effective fiber length, increasing the cores effective area, and using a band with a low nonlinear effect on the MCF can effectively minimize noise generation. Finally, we evaluate the proposed scheme and analyze and discuss the results.

Report on 3,143.6km Time and Frequency Transfer Fiber Link With Ps-level Stability

Abstract The letter describes the implementation of a high-precision time and frequency transmission system using a two-way and wavelength division multiplexing (WDM) scheme over 3,143.6 km of field fiber links, connecting 21 sites between Xi'an and Beijing, China. The scheme incorporates a link noise clean-up system (LNCUS), wherein the controlled very low-phase noise BVA oscillator acts as an internal frequency source at the relay site to effectively suppress the interference caused by fiber link noise. Additionally, high-stability pulse generation technology in LNCPS provides enough short-term stability to significantly improve the stability of the fiber time transfer. The results demonstrate that a time transfer stability in terms of time deviation (TDEV) of less than 2.07 ps@1s, 5.9 ps@100,000s, and the combined uncertainty of less than 49.29 ps can be obtained for the 3,143.6 km field fiber link. The obtained results represent a significant breakthrough in achieving high accuracy of time transfer and continuous operation over ultra-long span field optical fibers exceeding 3,000 km for the first time. This achievement enables the provision of time transfer and synchronization services over the longest international field optical fiber distance, thereby establishing the fundamental basis for constructing a nationwide high-precision time service through optical fiber networks.

Analysis of bit error rate and receiver sensitivity of a DC biased optical OFDM transmission link using single mode fiber with distributed Raman amplifier

Abstract In this paper, an analytical method is presented to assess the performance of bit error rate (BER) of a DC biased optical orthogonal frequency division multiplexing (DCO-OFDM) SMF transmission with distributed Raman amplifier (DRA). Formulas are developed to determine the signal-to-noise ratio (SNR) at the output of a DCO-OFDM receiver and the bit error rate (BER) for an OFDM demodulator’s output. By considering the Gaussian probability density function (pdf) for the OFDM demodulator output, the average BER is calculated numerically. The results are presented based on receiver sensitivity, bit error rate and optical SNR at a given BER of 10−9, with variations in system parameters such as input signal power, data rate, fiber distance, modulation index and OFDM sub-channel number. A comparison of BER performance indicates that DC biased optical OFDM with intensity modulation direct detection (DCO-DD-OFDM) offers better receiver sensitivity compared to optical OFDM without DC bias at a BER of 10−9. Our analytical results align with the published findings on optical OFDM.

High detail resolution cellulose structures through electroprinting

Electrospinning is a technique used to fabricate polymer fibers in micro- and nanoscales. Due to the large distance between the nozzle and collector, there is a limited positioning accuracy of electrospun fibers. To enhance the possibility of fabricating structures with micrometer placement, an electroprinting technique has been developed. By reducing the distance between the nozzle and the collector it is demonstrated that it is possible to get an improved control over fiber positioning which gives a possibility to fabricate designed 3D structures at the micron scale. In this study, cellulose acetate (CA) has been selected as a biomaterial to advance the 3D printing of membranes with possible use in separation applications. Various parameters, such as CA concentration and molecular weight, printing speed, printing pattern, applied voltage, etc. are evaluated with respect to printing control. Results indicate that by optimizing the printing parameters it is possible to print structures with inter- fiber distances down to 3 µm and fiber diameters at a sub-µm scale. This electroprinting development is promising for the fabrication of customized separation membranes. However, printing speed still remains a challenge.

Loading rate effects on multifiber pullout resistance of smooth steel fibers in ultra-high-performance concrete

This study investigated the multi-fiber pullout resistance of high-strength smooth steel fibers embedded in ultra-high-performance concrete (UHPC) at different loading rates. To discover the source of the fiber group effect on fiber pullout resistance, multi-fiber pullout tests were employed by changing the number of fibers, fiber-to-fiber distance, and difference in embedded lengths. The main source of the fiber group effect was found to be the reduced contact pressure per fiber, in the specimens containing more fibers, generated by matrix shrinkage: the fiber pullout stress at the static loading rate (0.0167 mm/s) decreased from 786.58 to 618.59 MPa (21.4 % reduction) as the number of fibers increased from 1 to 25. The equivalent bond strength of smooth steel fiber in UHPC generally increased from 4.5–5.2 to 5.9–7.1 MPa as the loading rate increased from 0.0167 to 1.67 mm/s. The favorable rate-sensitive pullout resistance of multi-fiber pullout specimens was notably affected by the number of fibers and fiber distance: the specimens containing nine fibers with a 2.7 mm fiber distance produced the highest dynamic increase factor (1.37) owing to enhanced interactions between interfacial cracks.

Multi-task metric learning for optical performance monitoring

In our experiments, applying few shot metric learning for optical performance monitoring (OPM), we set the dataset as 16-way-6-shot. Modulation format identification (MFI) was utilized as a classification task, and optical signal-to-noise ratio (OSNR) estimation was used as a regression task for joint analysis. Multi-task metric learning (MML) used the adaptive weights to balance the weights of the three metric functions, six modulation formats (QPSK, 8QAM, 16QAM, 32QAM, 64QAM, 128QAM) are classified correctly with 100 % accuracy after 200 epochs. Furthermore, the lowest mean square error (MSE) of OSNR is 0.431 dB. Then, Ablation experiments compute the corresponding similarity (SIM) for each metric function show that the MSE of MML, SIMLocal+Cosine, SIMCosine+Point, SIMLocal+Point, single-task metric learning (SML) and adaptive multi-task learning (AMTL) is 0.431 dB, 0.572 dB, 0.569 dB, 0.567 dB, 0.637 dB, 1.319 dB, respectively. The proposed model achieves the highest accuracy in MFI and the lowest MSE in OSNR estimation. Finally, when comparing the various metric functions while altering the transmission distance of the optical fiber, it was observed that MML stayed within an acceptable range between 200 km and 800 km. This shows that our algorithm requires only a small number of training samples to create a reasonably good model, offering a new approach to solving problems that arise in optical performance monitoring.

Ultrasound Shear Wave Elastography for Noninvasive Diagnosis of Acute Compartment Syndrome Using a Novel In Vivo Turkey Model.

Acute Compartment Syndrome (ACS) is a severe trauma caused by elevated intra-muscle-compartment pressure (ICP). The current standard method for diagnosis is to insert a needle into the muscle sterilely under anesthesia. However, to secure the environment is sometimes not easy and leads to delays in diagnosis. Recently, we have focused on shear wave ultrasound elastography (SWE) as an alternative, which can be done concisely in unclean environment and without anesthesia. We would like to report the usefulness of SWE for ACS diagnosis using 2-pedal walking turkey model recently developed in our lab. A total of 32 1-year-old Bourbon turkeys were used. 5% solution of chicken albumin was infused continuously into the tibialis cranialis (TC) muscle using IV pump. The ICP was increased stepwise from 0 to 50 mmHg. During the rising of ICP, the correlation between values of SWE (kPa) and ICP (mmHg) was measured. After the ICP reached 50 mmHg, half of the turkeys were maintained at this pressure for 2 hours and the rest for 6 hours. After infusion, a fasciotomy was performed on the half turkey. Half of the turkeys were euthanized after 2 weeks and the rest after 6 weeks. SWE of TC muscle and walking gait data on turkeys using a portable walkway system were measured weekly until euthanasia. At euthanasia, isometric tetanic muscle force (ITF) tests to TC muscle and histological evaluations were performed. SWE value (kPa) was highly significantly correlated to the actual ICP (mmHg) (R2 = 0.91). Stance of ACS side leg were significantly extended, and swing of the control side shortened from the second to the third week after ACS in the 6 hours infusion-no-fasciotomy group (P < 0.05*). ITF was significantly reduced mainly in the 6 hours infusion group (P < 0.05*). Histological evaluation revealed that in the 6 hours infusion and 6 weeks survival group, both the muscle fiber and intercellular distances were significantly expanded (P < 0.05). SWE seems to be a substitute measure of ICP in diagnosing ACS. With regard to our in vivo ACS model using turkey, survival at 50 mmHg ICP for 6 hours and 6 weeks post ACS would be an appropriate situation.

Double-link-failure-tolerant shared protection for fully coupled/half-split switchable point-to-multipoint coherent optical systems

Beyond 5G, the next-generation wireless communication standard requires an optical communication network with a more reliable point-to-multipoint system. A highly reliable, futuristic point-to-multipoint coherent optical system must update wavelength-division-multiplexing-based passive optical networks to a more disaster-resistant architecture that can switch between bypass and backup links. We propose, to our knowledge, a novel link-pair shared protection that can respond locally to double-link failures that result from a significant disaster. We validate the high availability of several network configurations, assuming a double-link disconnection, can be obtained irrespective of the transmission distance of the feeder fiber. We experimentally demonstrate link-pair shared protection with bidirectional wavelength pre-assignment for two of the four feeder fiber failures and validate a penalty of less than 2 dB for double-link failures. Furthermore, we prove that reconnection can be performed with a penalty of at most 2 dB in an experiment with shared protection with a single-link broadcast-and-select function that can manage partial double-link failures using a simple configuration.

Multitone Upconverted Phase-Modulated Signal RoF Link for 6G & Next-Generation Networks

The Next-Generation Networks offer a green environment giving specified data rates with ultra-low latency. Future efforts will be oriented in more degrees of freedom and system complexity by incorporating global optimization in terms of non-linearities, cost-effective, and reduced environmental impacts. The multitone upconverted radio over fibre (RoF) link with an optical modulator as phase modulator as desired alternatives with respect to optimization features and quantum photonic integration. In this paper, a framework has been developed to characterise the upconverted phase modulated signal model based on next-generation networks, in which an analytical model is investigated for single-tone upconverted, two-tone upconverted, and three-tone upconverted. Numerical simulations have been carried out to verify the novel outcomes using OptSIM software. The developed analytical models have a major contribution to the implementation of next-generation networks such as 5G, 6G, WiMAX, Quantum Communication, etc. The fundamentals of harmonics and the intermodulation product terms of third and fifth order via optical link are also evaluated for multitone Phase modulated RoF link with upconversion method. As per the finding outcomes, the proposed link is adaptable with frequency upconversion and long fibre distances.

Frequency Octupling Radio over Fiber System with Multiple Remote Antenna Units

Bidirectional radio over fiber (RoF) transmission to multiple remote antenna units (RAUs) with frequency octupling is proposed in this paper. The proposed RoF system uses a dual-port Mach-Zehnder modulator (DP-MZM) and an arrayed waveguide grating (AWG) to generate millimeter-wave (mm-wave) to four different RAUs. Bit Error Rate (BER) and received optical power are key parameters used to measure the performance of the system. From the simulation results, it is shown that the proposed system achieves an acceptable performance a fiber distance of 50 km with a BER of 10-12. Furthermore, the results indicate that the dispersion-induced power penalties for both uplink and downlink transmission of all RAUs are less than 1 dB. In summary, the proposed system simplifies the RoF system by reusing wavelengths and utilizing low RoF frequency through the frequency-octupling technique.

Detachment of particulate structures from a fiber array due to stretching and simultaneous gas flow

The main cause of high pressure drop and increased energy consumption in a filtration process is the clogging of particulate material in the upstream layers of a depth filter. To alleviate this issue, stress can be introduced into the particulate structure through stretching, which promotes rearrangement and detachment of particle structures, allowing for transfer of some of the clogged particulate material from the upstream layers to downstream void regions. This study aims to extend previous findings from experiments with single fibers to the level of an array. The goal is to analyze the introduction of a multiple stress state by performing stretching experiments with a particle-structure on a fiber array.The stretching tests investigate the influence of different process parameters such as stretching velocity and air flow velocity during stretching on the rearrangement and detachment behavior of a separated particle structures from the fiber array. Rearrangement and detachment of the particle structure are a direct consequences of the stress induced by stretching. The experiments showed a significant increase in relative free projection area of fiber interspaces (RFPI) of up to 160% and thus a large-scale removal of particle material from the fiber interspaces when the flow velocity was increased from 0.05 m/s to 0.8 m/s. Surprisingly, the radial rearrangement of the compact particle structures during stretching resulted in a clogging and blockage of the interfiber spaces (negative RFPI in the range of minimum −54% after the first stretching cycle) and not in a total release of the interfiber spaces. The size of the particle structures in the experiments decreased by about 331 μm with the number of stretching cycles, indirectly confirming the presence of residual structures. Preliminary experiments also confirmed an increased influence on the rearrangement and detachment (removed pariticulater material of about 30%) of particle structures by further increasing the fiber distance of 27 μm and thus introducing a biaxial stretching into the particle structure.

Improved evaluation model for macro-bending loss and power variation in single-mode fiber

It is challenging to calculate the macro-bending loss of optical fiber when the bending radius is reduced to sub-millimeter levels, based on Marcuse's theory and its derivative theories. Furthermore, these theories are limited in their ability to assess the distribution and changes of the optical field within the fiber, focusing solely on the analysis of loss. To overcome these limitations, we proposed an evaluation model which can simultaneously provide results for both macro-bending loss and power variation in a bent single-mode fiber. Our model achieves this by conformally transforming the fiber's refractive index profile of the axis section according to the bending radius. The ratio of output power to input power exhibits oscillation with changes in the bending radius, thereby resolving the issue of inability of Marcuse's theory to obtain an oscillation loss curve for sub-millimeter bending radii. The proposed model was validated by finite element method. We also obtained the internal power variation along the axial distance of the bent fiber through this model. This research improves the current fiber macro-bending loss evaluation model and lays a foundation for further studies on bend-insensitive fibers and the design of sub-millimeter bending sensors.

Nonbinary 2D Distribution Tool Maps Autonomic Nerve Fiber Clustering in Lumbosacral Ventral Roots of Rhesus Macaques.

Neuromodulation of the peripheral nervous system (PNS) by electrical stimulation may augment autonomic function after injury or in neurodegenerative disorders. Nerve fiber size, myelination, and distance between individual fibers and the stimulation electrode may influence response thresholds to electrical stimulation. However, information on the spatial distribution of nerve fibers within the PNS is sparse. We developed a new two-dimensional (2D) morphological mapping tool to assess spatial heterogeneity and clustering of nerve fibers. The L6-S3 ventral roots (VRs) in rhesus macaques were used as a model system to map preganglionic parasympathetic, γ-motor, and α-motor fibers. Random and ground truth distributions of nerve fiber centroids were determined for each VR by light microscopy. The proposed tool allows for nonbinary determinations of fiber heterogeneity by defining the minimum distance between nerve fibers for cluster inclusion and comparisons with random fiber distributions for each VR. There was extensive variability in the relative composition of nerve fiber types and degree of 2D fiber heterogeneity between different L6-S3 VR levels within and across different animals. There was a positive correlation between the proportion of autonomic fibers and the degree of nerve fiber clustering. Nerve fiber cluster heterogeneity between VRs may contribute to varied functional outcomes from neuromodulation.

Simplified coherent optical network units for very-high-speed passive optical networks

Future passive optical networks (PONs) for 200Gb/s/λ, and beyond, pose a significant technological challenge. The use of coherent technology in access networks provides a great solution based on concepts from mature technologies to achieve the speeds needed for very-high-speed PON (VHSP). In this paper, we provide an overview of the currently demonstrated technologies and propose a possible simplified optical network unit (ONU) for time division multiplex PON (TDM-PON). The proposed ONU uses a single polarization heterodyne receiver, using either a balanced photodiode or a single-ended one and an electro-absorption modulated laser (EML)-based transmitter. The experimental demonstration using the proposed ONU in a bidirectional, symmetrical transmission over fiber distances of 20 km and 40 km shows the viability of the technology. The downstream direction achieves a power budget of 34.3/29.3 dB for 20 km and 33.9/29 dB for 40 km, for a balanced/single-ended receiver, whereas the upstream transmission achieves 29.3 dB for both scenarios.

Physical-layer key distribution using synchronous complex dynamics of DBR semiconductor lasers

Common-signal-induced synchronization of semiconductor lasers with optical feedback inspired a promising physical-layer key distribution with information-theoretic security and potential in high rate. A significant challenge is the requirement to shorten the synchronization recovery time for increasing the key rate without sacrificing the operation parameter space for security. Here, open-loop synchronization of wavelength-tunable multi-section distributed Bragg reflector lasers is proposed as a solution for physical-layer key distribution. Experiments show that the synchronization is sensitive to two operation parameters, i.e., currents of grating section and phase section. Furthermore, fast wavelength-shift keying synchronization can be achieved by direct modulation on one of the two currents. The synchronization recovery time is shortened by one order of magnitude compared to close-loop synchronization. An experimental implementation is demonstrated with a final key rate of 5.98 Mbit/s over 160 km optical fiber distance. It is thus believed that fast-tunable multi-section semiconductor lasers open a new avenue for a high-rate physical-layer key distribution using laser synchronization.

Saturated transverse permeability of unidirectional rovings for pultrusion: The effect of microstructural evolution through compaction

AbstractThe transverse permeability of roving/tow‐based fiber reinforcement is of great importance for accurate flow modeling in the pultrusion process. This study proposes an experimental approach to characterize the roving‐based fiber beds' permeability under different compaction conditions. The experimental permeability results of thick roving‐based preforms were reported and compared with the permeability values of roving‐based preforms in the literature. A representative preform was infused under vacuum conditions. Its thickness was varied to replicate the different compaction values observed in permeability tests. Micrographs were then collected from it and analyzed to highlight the microscale transformations caused by processing/compaction on the fiber arrangement. The analysis revealed that compaction resulted in the reorganization of filaments along the direction of the applied compaction. Overall, the uniformity of the spatial filament distribution, i.e., the homogeneity within the fibrous domain, increased with increasing compaction. Furthermore, the microstructural analysis demonstrated transverse anisotropy within the tested domains, indicating that the obtained permeability results represented an upper boundary. In addition to the experimental analyses, various transverse permeability models, which were developed based on recently introduced statistical descriptors of fiber distribution, were evaluated by using the statistical descriptors extracted from the analyzed cross‐sections. Among these models, the one correlating the second neighbor fiber distance with apparent permeability exhibited good agreement with the experimental results.Highlights Transverse permeability measurement of a roving‐based reinforcement was presented. The influence of compaction on the microstructure was investigated at the filament level. Filament distribution in a pultruded profile was analyzed by using statistical descriptors. The results of the experiments and the models in the literature were compared. The correlation between microstructural features and apparent permeability was discussed.

Disaster resilience hybrid ring-mesh topology basics integrated PON/FSO system incorporating 2D-MFRS code

Abstract This work proposes a hybrid ring-mesh topology basics bidirectional 4 × 40/40 Gbps integrated passive optical network/free space optics (PON/FSO) system. The system incorporates two-dimensional modified fixed right shifting (2D-MFRS) code with enhanced disaster resilience and fault protection capability especially in remote places where the primary fibre may be destroyed. The obtained results depict that proposed system supporting 250 subscribers can provides faithful hybrid 100 km fiber and 1 km FSO transmission. Also, maximum FSO range of 21 km with fixed 50 km fiber distance can be obtained concerning weak-to-strong turbulent and rain with fog weather conditions. In addition, it also offers −39 dB m receiver sensitivity and the proposed design is superb over other work.

A 300 km fiber channel mapping using neural networks for Gb/s physical-layer key distribution.

Physical-layer secure key distribution (PLSKD) generally acquires highly correlated entropy sources via bidirectional transmission to share the channel reciprocity. For long-haul fiber links, the non-negligible backscattering noise (BSN) and the challenge of bidirectional optical amplification degrade the key generation performances. Since the channel reciprocity can be precisely mapped using neural networks (NNs), unidirectional PLSKD provides a feasible PLSKD for longer fiber links. Here, a final error-free key generation rate (KGR) in unidirectional PLSKD of 3.07 Gb/s is demonstrated over a 300 km fiber link using NNs. Moreover, the channel mapping is analyzed in terms of fiber distance, chromatic dispersion, the nonlinearity of random source, and BSN.

Ispitivanje nulte unakrsne korelacije fleksivilne promenljive težine (FVWZCC) za primenu u različitim medijima

Introduction/purpose: In this paper, we propose a novel code construction method with the zero cross-correlation property, the Flexible Variable Weight Zero Cross-Correlation (FVWZCC). This method is simple and flexible, using different code weights to support different classes of users according to their transmission distance and the quality of services they require (data, audio, and video) in OCDMA systems. The use of higher code weights enables the support of higher-priority application networks, such as long-haul reach networks. The ZCC code structure does not have overlapping of bit '1' and can efficiently eliminates the MAI interference between users and PIIN noise, thus enhancing the system overall performance. Methods: The shifting element position and the concatenation matrix process of the three basic matrices denoted as the Right vector, the basic matrix, and the Left vector were used for the construction of the proposed FVWZCC code. The mathematical analysis and simulations with Matlab and Optisystem software were used to evaluate the performance of the proposed FVWZCC method in SAC-OCDMA systems using the direct detection. Results: The results show a significant improvement in the presented code compared to other existing codes in terms of simplicity, flexibility, and cost implementation. The method uses either constant or variable weight with the Zero cross-correlation property. For a maximum acceptable BER of 10~9 , the simulation results of the SAC-OCDMA system using direct detection under OptiSystem software show better performance of the proposed code with four users of weight 6 at 10 Gb/s. Moreover, it can support up to 60 users simultaneously and reach a fibre distance of about 67 km. Consequently, the proposed FVWZCC code can be applied to support different Quality of Service (QOS) requirements with low cost and low complexity with a direct detection receiver. Conclusion: The findings of this study highlight the need for the FVWZCC code to support end-user QoS requirements. The new approach to code construction offers low-cost implementation, simplicity, and flexibility.

Visual outcome measures in pediatric myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD)

BackgroundMyelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) comprises various age-dependent clinical phenotypes and may be monophasic, multiphasic, or chronic. Optic neuritis (ON) is a common manifestation and frequently appears in combination with other MOGAD phenotypes, particularly in young children. Despite permanent structural damage to the retinal nerve fiber layer (RNFL), children often experience complete visual recovery. AimsTo analyze the progression and impact of MOGAD on the visual system of pediatric patients independently of the history of ON. MethodsThis retrospective study included children who met specific criteria: myelin oligodendrocyte glycoprotein (MOG) immunoglobulin G (IgG) seropositivity, acute presentation of MOGAD, and written general consent. Main outcome measures were global peripapillary retinal nerve fiber layer (pRNFL) thickness, and near and distance visual acuity, analyzed using descriptive statistics. ResultsWe identified 10 patients with median age of 7.7 years at first event: 7 patients manifested with acute disseminated encephalomyelitis (ADEM) (with ON 5/7, ADEM only 1/7, with transverse myelitis (TM) 1/7), 2 with isolated ON, and 1 patient with neuromyelitis optica spectrum disorder (NMOSD)-like phenotype with ON. Among ON patients, 5/8 were affected bilaterally, with 3 initially diagnosed with unilateral ON but experiencing subsequent involvement of the fellow eye. None of the patients without previous ON showed a deterioration of visual acuity and, if evaluated, a reduction of the pRNFL. ConclusionMost pediatric MOGAD-ON patients in our cohort presented with acute vison loss and optic disc edema. All patients achieved complete visual recovery, independent of number of relapses or initial visual loss. The pRNFL thickness decreased for several months and stabilized at reduced levels after 12 months in the absence of further relapses. MOGAD may not have subclinical/’silent’ effects on the visual system, as visual acuity and pRNFL were not affected in patients without ON.