This paper explores the usage of low-voltage Power-Line Communication (PLC) links for Enhanced Common Public Radio Interface (eCPRI)-based front-hauling in 5G IoT indoor mobile coverage environments, ...using a split Centralized Radio Access Network (C-RAN) architecture. This research aims to analyze how parameters such as wireless IoT device count, bandwidth, and transmission technology affect the delay performance of the proposed system. To achieve this goal, we develop detailed mathematical models that draw insights from queuing theory, stochastic geometry, and Markov models. Extensive system-level simulations verify these models' accuracy, and the analytical results cover radio and access delay performance. We validate the system's efficiency in supporting IoT indoor cellular applications and assess the feasibility of the proposed PLC-based fronthauling system, considering the strict delay requirements of the eCPRI standard.
Universal fiber is an optical fiber that supports both multimode and single-mode transmission. It is a multimode fiber with a mode field diameter of the fundamental mode roughly matching that of a ...standard single-mode fiber. In today's short-distance communications, both multimode fiber and single-mode fiber are used. Universal fiber can accommodate the needs of single-mode and multimode transmission so that end users can take advantage of the cost and performance benefits of each transmission type. In this paper, we present the design and properties of universal fiber, as well as its transmission performance for 100G systems. We also explore several application scenarios where the fiber can be utilized. In particular, we illustrate how the fiber can be used in 5G wireless fronthaul applications to meet the current needs while providing a path for future upgrades. Testing results and discussions of practical issues are also presented.
To economically manage the rapid traffic growth in data center networks, transmission technologies need to be studied for next-generation high-speed Ethernet, such as 1.6 TbE and beyond. This article ...describes a demonstration of 1.6 Tb/s (4 × 400-Gb/s/lane) O-band transmission over 10 km of installed four-core fiber. Since chromatic dispersion limits the transmission distance of the high-speed intensity-modulated direct detection (IM-DD) signals, a space division multiplexed technology using the 10-km four-core fiber is suitable to parallelly transmit 400-Gb/s/lane signals at near-zero dispersion wavelengths. A net-rate of 400 Gb/s/lane IM-DD signals with 155-GBd pulse amplitude modulation-8 (PAM-8) is generated by using an in-house broadband amplifier based on an InP double hetero-junction bipolar transistor (InP-DHBT). Our nonlinear maximum likelihood sequence estimation (NL-MLSE) enhances the performance of the 400-Gb/s/lane signals. We also introduce a technique called trellis path-limitation MLSE (TL-MLSE) for reducing computational complexity with temporarily decided results and a truncated trellis diagram. The trellis path-limitation MLSE with nonlinear calculation function (TL-NL-MLSE) achieves 1.6-Tb/s 10-km transmission in the O-band with the same performance as and lower computational complexity than the NL-MLSE.
In this work, we investigate the power-over-fiber (PoF) performance of a standard cladding single-mode 4-core fiber. Specifically, we clarify the influence of the fiber-end reflection and ...experimentally verify the applicability of our proposed approximation model. We show that PoF with a performance indicator of over 14.7 W·km can be achieved by using the standard cladding diameter 4-core fiber. The influence of the stimulated Raman scattering (SRS) spectrum on the wavelength allocation between power feeding light and signal light is also experimentally discussed.
This paper presents a linear least squares method for fiber-longitudinal power profile estimation (PPE), which estimates the optical signal power distribution throughout a fiber-optic link at a ...coherent receiver. The method finds the global optimum in the least squares estimation of the longitudinal power profiles; thus, its results closely match the true optical power profiles and locate loss anomalies in a link with high spatial resolution. Experimental results show that the method achieves accurate PPE with an RMS error of 0.18 dB from OTDR. Consequently, it successfully identifies a loss anomaly as small as 0.77 dB, demonstrating the potential of a coherent receiver in locating even splice and connector losses. The method is also evaluated under WDM conditions with optimal system fiber launch power, highlighting its feasibility for use in practical operations. Furthermore, the fundamental limit for stable estimation and the spatial resolution of least-squares-based PPE are quantitatively discussed in relation to the ill-posedness of the PPE by evaluating the condition number of the nonlinear perturbation matrix.
Current fiber-optic distributed acoustic sensor (DAS) target recognition technologies continue to prioritize updating the feature learning tools while neglecting varying contributions of information ...from different dimensions. Few works focus on designing recognition algorithms from the perspective of multi-dimensional information extraction and utilization. In this paper, we introduce an end-to-end three-dimensional attention-assisted convolutional neural network (3-D ACNN) into DAS for the first time. This novel approach allows for automatic and concurrent extracttion of three-dimensional input in time, frequency, and space, aiming to cooperatively recognize sensing targets with higher accuracy. Our new scheme also includes comparative examination of 2-D and 3-D attention mechanisms to leverage the most efficient information in various dimensions, thereby enhancing recognition accuracy while maintaining computation efficiency. Field tests demonstrate that the 3-D CNN outperforms commonly used 2-D networks with only time-frequency (T-F), time-space (T-S), or space-frequency (S-F) inputs, improving recognition accuracy from 95.47% to 98.67%. Moreover, the proposed 3-D ACNN can further improve accuracy up to 99.33%, outperforming the basic 3-D CNN. It is also found that T-F information in DAS is richer and more recognized than T-S and S-F information. The use of 3-D attention yields better results than 2-D attention. Additionally, the processing time required for each spatial sensing point is only 0.22 ms on a commercial GPU (NVIDIA GeForce (R) GTX 1080 Ti), which is approximately 1/171 of the time required for the equivalent 2-D network with the same T-F input (38.52 ms). The 3-D ACNN enabled smart fiber-optic DAS (sDAS) represents a significant breakthrough, enabling fast and accurate multi-dimensional collaborative recognition. This advancement is expected to have a substantial impact for distributed sensing applications.
Refractive-index (RI) sensing plays a pivotal role in various domains, encompassing applications like glucose sensing, biosensing, and gas detection. Despite the advantages of optical fiber sensors, ...such as their compact size, flexibility, and immunity to electromagnetic interference, they are often plagued by temperature-induced drift, which adversely impacts the accuracy of RI measurements. This study introduces an innovative approach to alleviate temperature-induced drift in RI-sensing optical frequency combs (OFCs) by employing active-dummy compensation. The central idea revolves around the utilization of a dual-comb setup, comprising an active-sensing OFC that monitors both sample RI and environmental temperature, and a dummy-sensing OFC that exclusively tracks environmental temperature. The disparity between these sensor signals, denoted as Δ f rep , effectively nullifies the effects of temperature variations, yielding a temperature-independent sensor signal for precise RI measurements. This investigation delves into the relationship between active-dummy temperature compensation and Δ f rep . It becomes evident that diminishing Δ f rep values enhance temperature compensation, thereby diminishing fluctuations in Δ f rep caused by environmental temperature shifts. This compensation technique establishes a direct link between Δ f rep and sample RI, paving the way for absolute RI measurements based on Δ f rep . The findings of this research are a valuable contribution to the advancement of accurate and temperature-compensated RI sensing methodologies using dual-comb setup. The insights gained regarding Δ f rep dependency and the strategies proposed for enhancing measurement precision and stability hold significant promise for applications in fields of product quality control and biosensing.
In this paper, a novel heterogeneous 8-core fiber, with a standard cladding diameter of 125μm, is proposed for C-band transmission. The structural parameters of 8-core fiber have been meticulously ...optimized through the utilization of an artificial intelligence-based algorithm, which resulted in a notable decrease in crosstalk and confinement loss, as the effective mode area of each core is sufficiently large to partially suppress the accumulation of nonlinear effects. The designed 8-core fiber was manufactured by traditional plasma chemical vapor deposition process. Besides, in order to implement the optical interconnection between single-mode fiber and 8-core fiber, a pair of corresponding fan-in/fan-out devices with low insertion loss have also been developed. The maximum crosstalk of designed 8-core fiber was measured to be -52.9dB/10km at 1550nm. Finally, using these fan-in/fan-out devices, we successfully demonstrated a 1.6Tbps (4x400G) self-homodyne coherent detection transmission in C-band over 10km, and the transmission characteristics were evaluated using a PDM-16QAM transceiver.
In this letter, we report for the first time the fabrication and sensor application of a helically twisted polymethylmethacrylate (PMMA) microstructured polymer optical fiber (mPOF). The fabrication ...was done by mechanically twisting the mPOF while passing it through a miniaturized Peltier element. The structure was created with a helical pitch of ∼700 μm, producing a series of spectral dips at the low loss region of PMMA, namely at the 400 to 500 nm region. The structure has been characterized to torsion showing that it can sense the twist direction with high sensitivities (48--53 nm/(rad/mm)). The strain sensor application has also been demonstrated, showing a negative sensitivity response with absolute values of 0.8--0.9 pm/μϵ. The soft and stretchable nature of mPOFs combined with helical structures will provide new opportunities for the development of highly tunable filters and innovative smart sensors.
In this paper, a frequency-scanned Φ-OTDR based on a frequency shifting loop (FSL) is proposed. The FSL is a fiber optic loop containing an acousto-optic frequency shifter (AOFS) and a fiber optic ...amplifier that converts a single-frequency pulse into a train of pulses with a fixed time and frequency spacing. By introducing bias light and precise switching control the AOFS, the FSL outputs low ASE noise pulses with a frequency spacing of 20 MHz and a scanning range of 460 MHz, which are used as the probe light for the frequency-scanned Φ-OTDR. In addition, a real-time update of the reference Rayleigh scattering pattern (RSP) is proposed to extend the strain measurement range. Experiments on a 3.96-km fiber shows that the strain ASD noise is better than 0.4 nϵ/Hz 1/2 , and approximate white noise at frequencies higher than 2 Hz with a spatial resolution better than 2.4 m. This frequency-scanned Φ-OTDR is suitable for low-frequency and quasi-static distributed strain measurements, and is expected to be applied to microseismic, teleseismic, and structural health monitoring.
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