Search

This paper proposes an efficient optical fiber communication scheme for an optical metro access network (OMAN) based on an optical multicarrier (OMC) generator. The central office (CO)'s foundation is a novel, cost‐effective OMC‐generating technique. The OMC is designed from a pulsed laser source and three cascaded electro‐optic modulators (EOMs) driven by an amplified RF source of 20 GHz signal that has generated more than 60 frequencies with excellent tone‐to‐noise ratio (TNR) ~ 40 dB and amplitude excursions from zero to 3 dB. The conventional CO is replaced with a cost‐effective OMC‐based source with an effective switching mechanism, which is necessary and equally important to be handled reliably. The downstream data of 20 Gbps per carrier is transmitted using a duo‐binary coding scheme. Six remote nodes (RNs) supported by the suggested OMC source, at each RN 10 optical network units (ONUs), can be deployed having distance laps of 5 km between the RNs, the distance between the RNs and the ONUs is kept at 2 km, the ONUs were tested w.r.t the bit error rate (BER) and the power penalties for the proposed transmissions. The BER for different fiber lengths from 5 to 25 km at various RNs and ONUs ranges were calculated and demonstrated from 1e−3 to 1e−13, showing the feasibility of the proposed OMAN. [ABSTRACT FROM AUTHOR]

This paper introduces a new bidirectional integration approach that combines fiber sensor/free space optics (FSO) communication using an intensity and wavelength division multiplexer (IWDM) techniques-based long-distance fiber Bragg grating (FBG) sensor strain-sensing system. By implementing coarse wavelength division multiplexing (CWDM), the system achieves the simultaneous transmission of optical communication and fiber optical sensor (FOS) sensing signals, resulting in a highly capable, flexible, and cost-effective solution. The proposed FSO transmission technique addresses complex fiber cable installation concerns with topographical limitations. This bidirectional structure ensures the reliability and stability of the long-distance FBG sensor system, supported by extensive research and experimentation. A hybrid stacked gated recurrent units and long short-term memory (SGRU-LSTM) model is proposed to enhance strain measurement accuracy by predicting and measuring the central wavelength of overlapped strain-sensing FBG sensor signals. The results demonstrate the superiority of the proposed model in peak wavelength detection accuracy. The primary benefit of integrating communication and sensing is the significant reduction in construction costs by eliminating the requirement for two individual fiber optic systems, as the integration allows for a single system to fulfill both functions, resulting in more efficient and cost-effective implementation. Overall, this paper contributes to advancing long-distance FBG sensor systems by integrating fiber sensor/FSO communication and deep learning techniques, improving transmission distance, multiplexing capacity, measurement accuracy, system survivability, and cost-effectiveness. [ABSTRACT FROM AUTHOR]

Fiber optic communications are inevitable to achieve higher data rates of modern telecom networks. After utilization of Wavelength division multiplexing, higher order modulations and polarization multiplexing, mode division multiplexing is a new dimension to achieve higher transmission capacity for optical fiber communication links. Different spatial distributions of optical energy along cross sectional area of optical fiber allows simultaneous transmission of data by considering each mode as an independent channel. During such simultaneous transmissions, possibility of mixing of signals amongst modes causes signal degradations and acts as limiting factor for bandwidth -- distance product of the link. This effect of mode coupling has been explored in this article by presenting its mathematical formulations. A simulation has been performed to study the impact of fiber constructional parameters on mode coupling using optical wavelengths used for telecommunication systems. The observations help to develop fiber for reduced mode coupling for particular group of modes and operating wavelengths. This article paves the way forward for study of mode coupling in micro and macro bending conditions for forthcoming research endeavours. [ABSTRACT FROM AUTHOR]

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Optical signal processing (OSP) technology is a crucial part of the optical switching node in the modern optical-fiber communication system, especially when advanced modulation formats, e.g., quadrature amplitude modulation (QAM), are applied. However, the conventional on–off keying (OOK) signal is still widely used in access or metro transmission systems, which leads to the compatibility requirement of OSP for incoherent and coherent signals. In this paper, we propose a reservoir computing (RC)-OSP scheme based on nonlinear mapping behavior through a semiconductor optical amplifier (SOA) to deal with the non-return-to-zero (NRZ) signals and the differential quadrature phase-shift keying (DQPSK) signals in the nonlinear dense wavelength-division multiplexing (DWDM) channel. We optimized the key parameters of SOA-based RC to improve compensation performance. Based on the simulation investigation, we observed a significant improvement in signal quality over 10 dB compared to the distorted signals on each DWDM channel for both the NRZ and DQPSK transmission cases. The compatible OSP achieved by the proposed SOA-based RC could be a potential application of the optical switching node in the complex optical fiber communication system, where incoherent and coherent signals meet. [ABSTRACT FROM AUTHOR]

The emergence of dynamic optical switching has opened up new perspectives for lightening the ever growing load on the electrical switches and routers, to meet the increasing demand on high-speed and flexible data processing and management in fiber-optic communications. Despite diversity schemes of optical switching in the single-mode regime, multi-mode switching of the hybrid fiber and chip system enabled by photonic integrated circuits, especially for the fiber-chip-fiber system, is still an outstanding challenge. Here, we propose and demonstrate the mode and polarization transmission and switching fiber-chip-fiber system with few-mode fibers (FMFs), including the FMF links for mode- and polarization-division multiplexing data transmission, the femtosecond (fs)-laser inscribed 3-dimensional (3D) photonic lantern silica chip for (de)multiplexing and coupling between FMFs and chip, and the topology-optimized N × N non-blocking 2-dimensional (2D) silicon switch array chip for switching and routing. Using 30-Gbaud quadrature phase-shift keying signals on wavelength-division multiplexing (WDM) channels, the WDM-compatible hybrid mode/polarization transmission, switching and routing system with FMFs, fs-laser inscribed silica (de)multiplexing chip and silicon switch array chip are demonstrated in the experiment with favorable operation performance. The demonstration may open the door for developing robust multi-dimensional optical data processing in fiber-optic communication systems with versatile fibers and chips. [ABSTRACT FROM AUTHOR]

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In optical fiber communications, data travels from the transmitter to the receiver, where it is collected and converted from optical pulses into electrical signals. The need for bandwidth has grown significantly in recent years. Dense Wavelength Division Multiplexing (DWDM), an advanced multiplexing technology that allows multiple signals to be delivered simultaneously at different wavelengths in the same channel, has been developed to meet the demand for higher capacity and faster data rates. There is a decrease in signal quality as a result of the pulse expansion caused by the scattering. During long-distance transportation, scattering should be minimized. In this research, The DWDM link model uses OptiSystem 18. The DWDM design uses 48 channels, 200 GHz channel spacing, and a bit rate of 40 Gbps for each channel The link length used is 240 and 300 km, using SMF (Single Fiber Mode) and DCF (Dispersion Compensation Amplifier). The research was performed with differences in laser power of 0, 3, and 5 dBm. From the results of the analysis carried out, changes in power changes affect the performance of the system using the MRZ (Mach Zander rate) produced by a CW-10 dB laser. The laser power values correspond to the standard Q-factor and BER (Bit Error Rate) values. The highest Qfactor is 23.266 and BER is 4.66232e-0120, while the lowest Q-factor is 14.9477 and BER is 7.89923e-051. Research has shown The more laser power is used, the better the system's performance. [ABSTRACT FROM AUTHOR]

Optical fiber communication is known as the backbone of communication today for voice, video, and data transmission. Recent advancements in optical technologies are leading us to many new forms of generation of orbital angular momentum (OAM) waves and its transmission technologies. Among them are hypergeometric waveform (HG), Bessel's waveforms, Laguerre Gaussian waveforms, and other forms of OAMs. This mode of communication is by the twisted form of electromagnetic wave which can accommodate a larger number of channels making communication simpler for wired and wireless communication. In this paper, various methods of OAM waveform generation are presented and are compared in details discussing the various needs in communication. OAM multiplexing is done by spatial division multiplexing (SDM) and wavelength division multiplexing (WDM). Methods of OAM communication, generation techniques, power analysis, and bit error analysis prove efficient transmission capability of OAM waves using low power consumption and low bit error rate in optical communication networks. OAM from fiber can be directly communicated to atmosphere which is found very useful for short distance wireless communication. Experimental validation is discussed for HG, Bessel's waveforms, and LG waveforms. Pure Optical Vertices (OV) are generated by VCSELs (vertical cavity surface emitting lasers) and transmitted by (MMF) multimode fibers. Various atmospheric effects and challenges are also elaborated in this paper. RSoft OptSim software is used for simulation. [ABSTRACT FROM AUTHOR]

In order to overcome the capacity limitations of current lightwave systems based on the single-mode optical fiber, massively parallel transmission in the spatial domain [space-division multiplexing (SDM)] supported by extended parallelism in the frequency domain (ultrawideband (UWB) systems) must be used. This article reviews key aspects of parallel transmission systems as the only significant capacity scaling option going forward and discusses the various tradeoffs on an architectural level and a hardware integration level. In doing so, this article also serves as an introduction to the more detailed accounts of fiber-optic systems and their future scaling within this Special Issue of the Proceedings of the IEEE. [ABSTRACT FROM AUTHOR]

Mode-division multiplexing (MDM) using few-mode fibers (FMFs) appears as a promising technology to increase fiber capacity by a few orders of magnitude and sustain the traffic demand for the decades to come. The potential of MDM lies in its ability to exploit multiple modes within a single optical fiber strand. Since 2011 and the first promising demonstrations, impressive progress has been made. In this article, we will show how the most recent advances in design and fabrication have improved the performance of FMFs and MDM systems, and allowed to turn research demonstrations into practical deployments. [ABSTRACT FROM AUTHOR]

Wavelength-division multiplexing (WDM) has historically enabled the increase in the capacity of optical systems by progressively populating the existing optical bandwidth of erbium-doped fiber amplifiers (EDFAs) in the $C$ -band. Nowadays, the number of channels—needed in optical systems—is approaching the maximum capacity of standard $C$ -band EDFAs. As a result, the industry worked on novel approaches, such as the use of multicore fibers, the extension of the available spectrum of the $C$ -band EDFAs, and the development of transmission systems covering $C$ - and $L$ -bands and beyond. In the context of continuous traffic growth, ultrawideband (UWB) WDM transmission systems appear as a promising technology to leverage the bandwidth of already deployed optical fiber infrastructure and sustain the traffic demand for the years to come. Since the pioneering demonstrations of UWB transmission a few years ago, long strides have been taken toward UWB technologies. In this review article, we discuss how the most recent advances in the design and fabrication of enabling devices, such as lasers, amplifiers, optical switches, and modulators, have improved the performance of UWB systems, paving the way to turn research demonstrations into future products. In addition, we also report on the advances in UWB optical fibers, such as the recently introduced nested antiresonant nodeless fibers (NANFs), whose future implementations could potentially provide up to 300-nm-wide bandwidth at less than 0.2 dB/km loss. [ABSTRACT FROM AUTHOR]

In this paper, we investigate various designs of distributed Raman amplifier (DRA) to extend amplification bandwidth in mid-link optical phase conjugation (OPC) systems and compare bands 191–197 THz and 192–198 THz giving a total bandwidth of 6 THz using a single wavelength pump. We demonstrate the use of highly reflective fiber Bragg grating (FBG) to minimize gain variation across a WDM grid by optimizing forward and backward pump powers as well as the wavelength of FBGs for original and conjugated channels. Finally, we also simulate OSNR and Kerr nonlinear reduction as a product of signals asymmetry and nonlinear phase shift (NPS) for all channels. [ABSTRACT FROM AUTHOR]

This paper deals with improving transmission properties of a DWDM system based on amplification techniques. Parameter values change due to a change in the type of optical amplifier or an adjustment of the parameters of the optical amplifiers. Optimization summarizes the knowledge of the systems and software that are used. These assumptions are verified by a set of simulations and the obtained numerical values are compared with the values given in the relevant articles. The proposed design, which uses a larger number of EDFA amplifiers over long distances, has been found to perform better than single amplifier systems. In addition, the proposed solution is better in transmission characteristics than other approaches with a similar purpose. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Orbital angular momentum (OAM) multiplexing technology is expected as one of the prospective candidates for sustaining the further increment of data-transmission capacity in the optical communication systems. Advanced multiplexing technology of combining OAM-based mode division multiplexing (MDM) in the multicore fiber (MCF) with wavelength division multiplexing (WDM) can further improve the transmission rate and spectrum efficiency in the communication systems. In this paper, a multi-ring-air-core fiber (MRACF) supporting thousands of OAM modes is designed and analyzed. The tradeoffs between ring number/density and their corresponding system performance parameters in this fiber are systematically investigated. Based on the analytical results, MRACF with 37 rings can support a record high 4440 radially fundamental OAM modes at 1550 nm, featuring <−53 dB inter-ring crosstalk and >5.67 × 10−4 intra-ring modal effective refractive index difference. Furthermore, a record-high 4144 radially fundamental OAM modes with <−40 dB inter-ring crosstalk can be supported across C and L bands from 1530 nm to 1625 nm, which is one order of magnitude larger than the number of linearly polarized (LP) modes or supermodes ever reported within one single fiber. [ABSTRACT FROM AUTHOR]

Graph HT ht (2) Graph: Figure 1: WDM-PON network architecture. Keywords: dual drive Mach-Zehnder modulator; single sideband suppressed carrier; optical network unit; optical line terminal; BER EN dual drive Mach-Zehnder modulator single sideband suppressed carrier optical network unit optical line terminal BER 353 361 9 07/05/22 20220701 NES 220701 1 Introduction A point-to-multipoint design of passive optical networks (PONs) is used to facilitate the users with broadband connectivity. Graph HT ht (10) 3.2 Simulation results The WDM -PON system model existing are demonstrated in Figures 4 and 5 respectively are analyzed in this section. [Extracted from the article]

The optical parametric amplifier (OPA) has attractive features for optical communications, such as a wideband, high gain, and fast transient response. In addition, by using idler light, which is phase-conjugated light generated in the amplification process, various kinds of optical signal processing, such as fiber-nonlinearity mitigation, wavelength conversion, and phase-sensitive amplification, can be performed. A periodically poled LiNbO3 (PPLN) waveguide is an χ(2)-based optical parametric amplification medium, and it makes both wideband and high-gain amplification possible. We developed a 4-port PPLN module that can combine signal light and pump light into a PPLN waveguide with low loss. In this paper, we overview the applications of OPA to WDM optical fiber transmission and explain the configurations of an OPA using 4-port PPLN modules. As applications of our PPLN-based OPA, we introduce the demonstration of wideband inline amplification exceeding 5 THz. Furthermore, we demonstrate inter-band wavelength conversion between C- and S-bands using PPLN waveguides developed for multi-band optical transmission applications. [ABSTRACT FROM AUTHOR]

Constellation shaping is a practical and effective technique to improve the performance and the rate adaptivity of optical communication systems. In principle, it could also be used to mitigate the impact of nonlinear effects, possibly increasing the information rate beyond the current limit dictated by fiber nonlinearity. However, this appealing idea is frustrated by the difficulty of designing an effective shaping strategy that takes into account the nonlinearity and long memory of the fiber channel, as well as the possible interplay with other nonlinearity mitigation strategies. As a result, only little progress has been made so far, while the optimal shaping distribution and the ultimate channel capacity remain unknown. In this work, we describe a novel technique to optimize the shaping distribution in a very general setting and high-dimensional space. For a simplified block-memoryless nonlinear optical channel, the capacity lower bound obtained by the proposed technique can be expressed analytically, establishing the conditions for an unbounded growth of capacity with power. In a more realistic scenario, the technique can be implemented by a rejection sampling algorithm driven by a suitable cost function, and the corresponding achievable information rate estimated numerically. The combination of the proposed technique with an improved (non-Gaussian) decoding metric yields a new capacity lower bound for the dual-polarization WDM channel. [ABSTRACT FROM AUTHOR]

We introduce the concept of the universal virtual lab, an extension to the virtual lab platform of [Golani et al. 2016], enabling a fast and accurate simulation of wideband nonlinear DWDM systems. The universal virtual lab is compliant with non-ideal transmitter and receiver architectures, distributed optical filters in the optical link, inter-channel stimulated Raman scattering, and it provides accurate performance predictions even when adaptive equalization methods are applied. In comparison with the conventional full-bandwidth split step Fourier transform method, we show with different test scenarios that the universal virtual lab provides accuracy errors below 0.1 dBQ and 0.09 bit/4D-symb in Q-factor and GMI assessments respectively, with runtime speedup factors exceeding 1000. We also report performance assessments in an ultra-wideband (11 THz) C+L system and discuss equalization gain under different compensation scenarios. The estimated speedup factor with respect to the full-bandwidth split step Fourier transform method is assessed to be greater than 35,000. [ABSTRACT FROM AUTHOR]

Over last decades, the free space optics (FSO) emerged as most prominent way of communication over radio frequency communication and microwave communication. The FSO works in the same way optical fiber cable (OFC) network works with the only difference that the optical beams were transmitted through the free space and not by using the OFC core i.e. the glass fiber. The presence of mist, fog, rain and clouds in the atmosphere directly affects the performance of FSO and the power of propagating signal is degraded significantly. Since the wavelength of propagating beam is comparable to size of fog particles, they mainly lead to atmospheric attenuation. To mitigate the impact of atmospheric attenuation on signals, the present study develops a spectrum slicing (SS)-wavelength division multiplexing (WDM) system with Pre and Post Amplification. The performance of the proposed SS-WDM-Pre and SS-WDM-Post scheme is analyzed and then compared with the traditional SS-WDM model in the Opti-system in terms of Q-factor and BER values. The analysis of the proposed and traditional scheme is done under varying attenuation and power signals during summer, winter, autumn and spring season.The comparative analysis proved that the performance of the proposed SS-WDM-Post and SS-WDM-Pre-model is more effective and efficient when compared with the traditional SS-WDM model in terms of Q-Factor and BER during all 4 seasons. [ABSTRACT FROM AUTHOR]

A method for reducing the training time of a deep learning based digital backpropagation (DL-DBP) is presented. The method is based on dividing a link into smaller sections. A smaller section is then compensated by the DL-DBP algorithm and the same trained model is then reapplied to the subsequent sections. We show in a 32 GBd 16QAM 2400 km 5-channel wavelength division multiplexing transmission link experiment that the proposed stacked DL-DBPs provides a 0.41 dB gain with respect to linear compensation scheme. This needs to be compared with a 0.56 dB gain achieved by a non-stacked DL-DBPs compensated scheme for the price of a 203% increase in total training time. Furthermore, it is shown that by only training the last section of the stacked DL-DBP, one can increase the compensation performance to 0.48 dB. [ABSTRACT FROM AUTHOR]

Multilevel power converters play an increasingly important role in energy transmission, high-power electric drives and renewable energy systems. The transmission of control signals for the semiconductor switches in power converters is critical for the operation of the system, and therefore optical communications links are employed to minimize electromagnetic interference. However, conventional parallel communication topologies have the drawback of requiring a high number of independent optical fibers and transmitter-receiver pairs as the number of transmitted signals increase, which limits the flexibility and scalability of the link. In this paper we propose the design of an optical link with wavelength division multiplexing (WDM) based on a digital micromirror device (DMD) and a linear detector array as receiver. The main advantages of the proposed system are the high flexibility and scalability of the communications link. Simulation results are obtained from a mathematical modeling of the transmitter, the link and the receiver. The communication is established by means of an asynchronous protocol in order to ensure the correct decoding of the transmitted gating signals. A feasibility analysis of the optical link is carried out in terms of the waveform quality of the multilevel inverter output voltage, measured by its total harmonic distortion (THD). The simulation results obtained in MATLAB/Simulink environment validate the methodology to enable a future implementation of the proposed optical communication link. [ABSTRACT FROM AUTHOR]

Opening new wavelength bands is the most economic step for further increasing the capacity of optical transmission links. Characteristics of different amplifier technologies for signal amplification in different wavelength bands are detailed. In particular, the suitability of these technologies for short–term and mid–term implementation is considered. An important criterion is the availability of qualified components, notably the required pump laser diodes. On this basis, solutions for the near–term and the mid–term are discussed. [ABSTRACT FROM AUTHOR]

We experimentally demonstrated a long-haul wavelength-division multiplexed (WDM) and space-division multiplexed (SDM) transmission of 32-Gbaud polarization-division multiplexed quadrature phase-shift keying signals over 52-km coupled-4-core fiber spans with amplification by coupled-4-core erbium-doped fiber amplifiers (EDFAs). Error-free performance after forward error correction was achieved up to 2700 km. From converged multi-input multi-output filter coefficients, we estimated the mode dependent loss (MDL) that occurred in this experiment. The MDL was frequency-dependent within a WDM channel and the root-mean square MDL was 1.0 dB per loop. To assess the effect of MDL on SDM transmission performance, we also estimated the outage probability through Monte-Carlo simulations with a Gaussian noise model. The estimated outage probability under MDL showed similar performance to that obtained in the transmission experiment. This suggests that the MDL of coupled-multi-core EDFAs was one of the major limiting factors of the transmission performance and that the rms MDL per span should be below 0.4 dB for further long-haul transmission distance over 6000 km. [ABSTRACT FROM AUTHOR]

We experimentally utilize a tunable, broadband pixel-array-based integrated receiver for recovering orbital-angular-momentum (OAM) multiplexed channels. The OAM receiver comprises a pixel-array-based mode converter, four phase controllers, and a pixel-array-based 4-to-3 coupler. Utilizing the mode converter, a free-space data-carrying OAM beam ($\ell \ = \ - 1$ or $\ell \ = \ + 1$) is vertically coupled into four waveguides. The resulting waveguide modes carry an OAM-order-dependent phase delay between each other. Subsequently, a 4-to-3 coupler coherently combines four waveguide inputs with the specific phase delay into a specific output port. By further tuning the relative phase delay of the waveguides using the phase controllers, the data channel carried by a specific OAM beam ($\ell \ = \ - 1$ or $\ell \ = \ + 1$)) could be routed to different ports. As there is no specific resonant wavelength, the OAM receiver could be operated with a relatively broad bandwidth. The experimental results show that: (a) the target OAM mode to be received by the OAM receiver could be tuned from ($\ell \ = \ - 1$ to $\ell \ = \ + 1$) with a <−14-dB inter-modal power coupling; (b) in a wavelength range of ∼6 nm, two OAM-carried 50-Gbaud quadrature-phase-shift-keying (QPSK) data channels ($\ell \ = \ - 1$ and $\ell \ = \ + 1$) could be recovered by the tunable OAM receiver with a bit error rate (BER) performance below the 7% forward error correction threshold; and (c) a 400-Gbit/s OAM-multiplexed and wavelength-division-multiplexed (WDM) QPSK link is demonstrated with a <2-dB optical signal-to-noise ratio (OSNR) penalty compared to that of a single-beam link. [ABSTRACT FROM AUTHOR]

In optical communications, sphere shaping is used to limit the energy of lightwaves to within a certain value over a period. This minimizes the energy required to contain information, allowing the rate of information transmission to approach the theoretical limit if the transmission medium is linear. However, when shaped lightwaves are transmitted through optical fiber, Kerr nonlinearity manifests itself as nonlinear interference in a peculiar way, potentially lowering communications capacity. In this article, we show that the impact of sphere shaping on Kerr nonlinearity varies with chromatic dispersion, shaping block length and symbol rate, and that this impact can be predicted using a novel statistical measure of light energy. As a practical consequence, by optimally controlling the parameters of sphere-shaped lightwaves, it is experimentally demonstrated that the information rate can be increased by up to 25% in low-dispersion channels on a 2824 km dispersion-managed wavelength-division multiplexed optical fiber link. The authors report nonlinear interference changes with shaping block length, modulation symbol rate, and chromatic dispersion when sphere-shaped lightwaves propagate through optical fibre, and suggest a method to predict that change. [ABSTRACT FROM AUTHOR]

The performance of moment generating function approaches, specifically Chernoff bound (CB) and modified Chernoff bound (MCB), is examined and improved in this study. We evaluates and enhances the performance of a wavelength division multiplexing (WDM) technique for free-space optical (FSO) fibre communications based on passive optical network (PON) using the M-ary digital pulse-position modulation (M-ary DPPM) schemes under amplified spontaneous emission (ASE) noise effects, interchannel crosstalk (ICC), and atmospheric turbulence (AT). We use a data rate of 2.5 Gbps for eight channels over a PON/DWDM-FSO optical fibre system in the C-band with 100 GHz channel spacing start from 1550 nm. The results achieve 20 Gbit/s transmissions (2.5 Gbps × 8 channels). This is a technology that can have extended leverage, higher data rates, power-efficient, and is considered an ideal option for the provision of bandwidth for potential access networks. When compared to the CB at a low gain (G = 8), the MCB outperforms the Gaussian approximation at high gain (G = 30). Because of its superior performance at a high gain (G = 30), the MCB offers the tightest limit on the bit error rate (BER). In comparison to an equivalent on–off keying (OOK) non-return-to-zero (NRZ), the M-ary DPPM scheme with a coding level (M) of 2 improves average power about by 2.9 dB at a data rate of 2.5 Gbps on the 1550 nm wavelength and BER of 10 - 9 . The sensitivity of the M-ary DPPM modulation scheme remains improved over OOK in the presence of ICC. The lower power penalty is predicted to be approximately 0.2–3.0 dB in the DWDM-FSO systems for low coding level M = 2. We achieve a lower power penalty at 0.2–3.0 dB for the hybrid fiber DWDM/PON-FSO optical communication system at a BER of 10 - 9 . At a target BER of 10 - 12 , the hybrid OOK-NRZ/M-ary DPPM offers about 4–8 dB of optical signal-to-noise-ratio improvements over the M-DPPM of the WDM-PON/FSO link for strong turbulence. The results demonstrated that the M-ary DPPM and the optical relaying amplification technique are powerful treatments for mitigating the impacts of ASE noise, AT, and ICC. [ABSTRACT FROM AUTHOR]

We report an industry leading optical dense wavelength division multiplexing (DWDM) field trial with line rates per channel $\ge 1.66$ Tb/s using 130 GBaud dual-polarization probabilistic constellation shaping 256-ary quadrature amplitude modulation (DP-PCS256QAM) in a high capacity data center interconnect (DCI) scenario. This research trial was performed on 96.5 km of field-deployed standard single mode G.652 fiber infrastructure of Deutsche Telekom in Germany employing Erbium-doped fiber amplifier (EDFA)-only amplification. A total of 34 channels were transmitted with 150 GHz spacing for a total fiber capacity of 56.51 Tb/s and a spectral efficiency higher than 11bit/s/Hz. In the single-channel transmission scenario 1.71 Tb/s was achieved over the same link. In addition, we successfully demonstrate record net bitrates of 1.88 Tb/s in back-to-back (B2B) using 130 GBaud DP-PCS400QAM. [ABSTRACT FROM AUTHOR]

Several modulation techniques aimed at ensuring high capacity and low latency for next generation of mobile transport networks are discussed. Centralized radio access networks are considered based on WDM transmission to ensure long distance, sufficient number of antenna sites and segregation of heterogeneous connectivity services over the same fiber infrastructure. Of all the proposed techniques, attention is paid to those allowing for low-cost transceivers. With increasing bit-rate, when considering distances in the order of 20 km, the most significant impairment is the fiber chromatic dispersion. The reasons dispersion compensating fiber modules are to be avoided in a mobile transport network are discussed and modulation formats resilient to fiber chromatic dispersion are examined to check for the highest achievable bit-rate when using direct-detection receivers. It is shown that, when using binary formats, the combined amplitude-phase shift (CAPS) codes allow to bridge a distance of 15 km or more with a significant power budget advantage over PAM-4. However, higher modulation formats such as PAM-4 allow for slower electronics speed. When halving the speed of electronics is desirable and optical amplification is employed, a bipolar PAM-4 format allows for an improved power budget. One of the results of this paper is that, without any signal processing or dispersion compensators and without exploiting polarization modulation, direct-detection formats cannot be employed to bridge distances of the order of 20 km at a bit-rate greater than about 50 Gb/s. To achieve higher rates, coherent detection is needed and we also discuss a low-cost implementation avoiding a local oscillator for detection. [ABSTRACT FROM AUTHOR]

Nonlinear interference (NLI) generated during the propagation of an optical waveform through the fiber depends on the fourth order standardized moment of the channel input distribution, also known as kurtosis. Probabilistically-shaped inputs optimized for the linear Gaussian channel have a Gaussian-like distribution with high kurtosis. For optical channels, this leads to an increase in NLI power and consequently, a decrease in effective signal-to-noise ratio (SNR). In this work, we propose kurtosis-limited enumerative sphere shaping (K-ESS) as an algorithm to generate low-kurtosis shaped inputs. Numerical simulations at a shaping blocklength of 108 amplitudes demonstrate that with K-ESS, it is possible to increase the effective SNRs by 0.4 dB in a single-span single-channel scenario at 400 Gbit/s. K-ESS offers also a twofold decrease in frame error rate with respect to Gaussian-channel-optimal sphere shaping. [ABSTRACT FROM AUTHOR]

Thulium-doped fiber amplifiers (TDFAs) can provide high power optical amplification in the wavelength range of 1,460–1,545 nm (S and near-C bands). They can be employed for dense wavelength division multiplexing (DWDM) in optical fiber communication over a broad range, unlike the Erbium-doped fiber amplifiers (EDFAs), which are active in the C-band only in the conventional "erbium window." Line service surveillance and management of digital optical information in DWDM TDFA networks can be done by low-frequency amplitude modulation (~100 kHz) of TDFA pump and communication signal, termed as overmodulation. Governing equations for overmodulation gain dynamics in TDFAs using the Bononi and Rusch (1998) model was first derived in a companion paper (2017). The research provides a methodical test bed analysis using MatLab Simulink model with a different outlook in the respective field. The transfer functions for signal-to-signal and signal-to-amplified spontaneous emission were implemented to develop a simulator. An undesirable 30 % increment in the output modulation index at 8 dBm and 1,490 nm were obtained by simulating overmodulation sensitivity at different levels of mean input signal power and signal wavelength respectively at corner frequency. The optimum operating wavelength for TDFAs obtained was 1,490 nm. [ABSTRACT FROM AUTHOR]

Higher spectral efficiency and data rate per channel are the most cost-effective approaches to meet the exponential demand of data traffic in optical fiber network communication system. In this paper, diverse modulation formats are analyzed for Dense Wavelength Division Multiplexed system at 100 Gbps * 16=1600 Gbps data rates. The performance analysis of proffered system for Non-Return to Zero, Return to Zero, Carrier- Suppressed Return to Zero and Duo binary RZ with duty cycle 0.5 to 0.7 ranges like modulation formats are considered to find optimum modulation format for a 100 Gbps bit rate per channel optical fiber transmission network system. The simulations are analyzed for different values of input power, length of fiber, nonlinear refractive index, nonlinear dispersion and nonlinear effective area for all above mentioned modulation formats with spacing 100 to 250 GHz. to evaluate the effect of modulation format Fiber Bragg Gratting, optical fiber amplifier and Dispersion Compensation Fiber dispersion compensation techniques are enacted on this proposed optical network system. [ABSTRACT FROM AUTHOR]

Single–fiber bidirectional transmission systems using the same wavelength for both directions suffer from reflection induced interference. Experimental results demonstrate the dependence of system performance and of the threshold of the forward error correction (FEC) on signal waveform variations induced by fiber effects. Larger signal distortions lead to slightly larger impact of the interference, but reduce the shift of the FEC threshold to smaller bit error ratios. [ABSTRACT FROM AUTHOR]

By means of narrow 2D-steerable infrared beams, interference-free individual wireless connections to densely-spaced devices in industry 4.0 settings can be made. Beam steering by fiber-fed passive diffractive beam steering modules and wavelength-tunable transceivers located in a separate controller location enable readily scalable connectivity to many devices and their nomadic mobility. To accommodate the dynamics in industry 4.0 settings, self-calibrating localization of the devices by means of retro-reflecting corner cube foils and beam scanning is demonstrated, and a low-complexity broadband wide field-of-view optical wireless receiver is presented, based on a matrix of photodiodes. [ABSTRACT FROM AUTHOR]

A nonlinearity-tolerant constant composition distribution matching (CCDM) scheme based on a parallel bisection architecture is proposed. Compared with CCDM based on arithmetic coding (AC), the bisection-based CCDM (BS-CCDM) can achieve the same linear performance and an improved tolerance to fiber nonlinear impairments in unrepeated fiber transmissions. The same linear performance of AC-CCDM and BS-CCDM is evaluated both in simulations and experiments with various modulation formats and shaping rates. The improved fiber nonlinear performance is demonstrated in simulations with probabilistically shaped dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) signals for unrepeated transmission over 250 km of standard single-mode fiber (SSMF). BS-CCDM provides a ∼0.22 dB gain in effective signal-to-noise ratio (SNR) on average over AC-CCDM for a variety of spectral efficiencies with a block length of 64. And a gain in achievable information rate (AIR) of ∼0.11 bits/4D-symbol is obtained correspondingly. In addition, by further optimizing the look-up tables (LUTs) in BS-CCDM, a better trade-off between the linear performance and nonlinearity tolerance is achieved. Compared with AC-CCDM, the optimized BS-CCDM provides the gain of 0.48 dB and 0.7 dB in effective SNR for the block length of 64 and 128, respectively. [ABSTRACT FROM AUTHOR]

We investigate polarization insensitive fiber optical parametric amplifiers (FOPAs) employing a balanced polarization diversity loop with at least two unidirectional gain fibers. We describe and compare three variants of looped polarization insensitive FOPAs optimized for noise figure, mitigation of nonlinear impairments and their trade-off, respectively. The test scenario consists of amplifying, by up to 14 dB, a set of 21 × 50 GHz-spaced channels including a 35 GBaud PDM-QPSK signal, and evaluating a power of nonlinear crosstalk, noise figure and amplified signal BER for each variant. For the first time we demonstrate a polarization insensitive FOPA amplifying WDM signals with a noise figure as low as 5.8 dB, and a polarization insensitive FOPA with output WDM signal power of 23 dBm. The testing results let us identify likely application scenarios for each looped FOPA variant. We justify potential implementation of polarization-insensitive FOPAs in future optical communication systems by arguing its ability to deliver low noise figure <6 dB for output signal power as high as 29 dBm and to enable polarization insensitive gain for the most prominent single-polarization FOPA achievements realizing ultrawide high gain. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel erbium–ytterbium doped fiber amplifier (EYDFA) + Raman + EYDFA hybrid optical amplifier (HOA) for a super-dense wavelength division multiplexing (SD-WDM) system application. The performance of the 100-channel system has been investigated for an overall data rate and channel spacing of 100 Gb/s and 0.4 nm, respectively, over a wavelength span of 1550–1589.9 nm. HOA has been optimized for Raman length, EYDFA lengths, pump powers and Er + concentrations to achieve high average gain and low gain variation ratio of 40.41 dB and 0.40 respectively. The optimized configuration of the proposed HOA has been compared with EYDFA + Raman and Raman + EYDFA HOA configurations. The achieved high and flat gain with an acceptable output optical signal to noise ratio (OSNR) in case of EYDFA + Raman + EYDFA HOA; makes it an optimum choice for SD-WDM systems. [ABSTRACT FROM AUTHOR]

We demonstrate experimentally a bandwidth-reconfigurable mmWave Fiber Wireless (FiWi) fronthaul bus topology for spectrally efficient and flexibly reconfigurable 5G Centralized-Radio Access Networks (C-RAN). The proposed fronthaul architecture includes four 1 Gb/s Intermediate Frequency over Fiber (IFoF) channels that can be flexibly allocated among two in-series Reconfigurable Optical Add/Drop Multiplexer (ROADM) integrated nodes, supporting in total 8 V-band 32-element Phased Array Antenna (PAA) terminals. The ROADM was fabricated as an integrated photonic device exploiting the ultra-low loss Si3N4 TriPleX waveguide integration platform and an architectural layout based on cascaded MZI interleavers. The device has flat top response of 32.5 GHz with a Free Spectral Range (FSR) of 100 GHz and fiber-to-fiber losses of 5 dB, while the V-band PAA supports analog RF beamsteering capabilities within a 90°-sector and 1m wireless distance. Each of the FiWi links carries a 250 MBd QAM16 waveform enabling a total of 1 Gb/s rate per end user beam, complying with the 5G Key Performance Indicator (KPI) user-rate requirement. Bandwidth-reconfigurability is experimentally demonstrated by selectively dropping channels either at the first or at the second ROADM node, allowing in this way the bandwidth allocation to be flexibly defined between two different network segments. Both uplink and downlink performance are experimentally validated for different ratios of bandwidth allocation among the two nodes, revealing Error Vector Magnitude (EVM) values that meet the respective 3GPP signal quality specifications. The two-stage FiWi IFoF/mmWave fronthaul bus topology, based on a miniaturized, integrated, low loss Si3N4 ROADM and supporting high-capacity wireless beamsteering capability can form a promising roadmap towards flexible and reconfigurable 5G C-RAN architectures. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for data rates by mobile users can be fulfilled by radio over fiber (RoF) combined with spectrally-efficient modulation techniques. Thus, RoF is critical to the design of the fronthaul for 5th generation (5G) mobile communication networks. We propose and experimentally demonstrate a low-cost directly modulated laser (DML)-based wavelength division multiplexing (WDM)-RoF transmission system for use in next-generation 5G networks. The proposed architecture provides flexible resource allocation as well, under low and high traffic loads at the remote radio heads (RRHs). We also present robust analytical models of the proposed DML-based WDM-RoF network with spectrally-efficient M-ary-quadrature amplitude modulation (M-QAM), beneficial for system designers. In OptiSystem software, we evaluate the error vector magnitudes (EVM) as a function of the optical link lengths, input optical power, and the received optical power with 4/16/64-QAM over the optical link. The EVMs of the link for 4/16/64-QAM are below the 3GPP standards for 5G. We find good agreement between the simulations and the analytical results. We also experimentally demonstrate a small scale model of this network with resource allocation. Such a flexible architecture is suitable for meeting the demands of femtocells in 5G fronthaul networks. [ABSTRACT FROM AUTHOR]

We review the fundamentals of the recently proposed Generalized Droop model and highlight its use in power efficiency optimization of long-haul low-SNR space-division multiplexed submarine links. [ABSTRACT FROM AUTHOR]

Wavelength division multiplexing (WDM) technique plays a vital role in optical fiber communication. In this paper, a 4 × 1 WDM system has been developed with Vertical Cavity Surface Emitting LASER as optical source for each input. The performance analysis has been carried for Non Return to Zero (NRZ), hyperbolic secant, Gaussian and impulse generators over complex WDM optical fiber up to 50 km with less attenuation of 0.2 dB/Km. The Signal to noise ratio of received signal through Avalanche Photo diode in the receiver is calculated. This work identifies the best pulse generator with reduced noise performance suitable for the proposed system. The proposed system is modeled in optisys13 and insightful discussions are provided from the simulated results. [ABSTRACT FROM AUTHOR]

In this study, an ultra-broadband orbital angular momentum (OAM) mode generator based on a phase-modulated helical long period fiber grating (HLPG) working at highradial order cladding mode is firstly proposed and numerically demonstrated. The proposed phase-only modulation method can considerably facilitate the HLPG’s fabrication by eliminating the grating’s apodization, which is extremely difficult to realize in the screw-type grating. Meanwhile, the proposed method provides more flexibilities in the design of HLPGs. As a typical example, a first-order OAM (OAM −1) mode generator with a bandwidth of ~63 nm, a conversion efficiency of ~100%, and purity of ~ 91% has been numerically demonstrated. Moreover, an OAM −1 mode generator with a bandwidth of ~469 nm, a conversion efficiency of ~100%, and purity of ~ 91% has been successfully obtained, covering all bands of fiber communication, i.e., o riginal- (O-), extended- (E-), short- (S-), conventional- (C-), long- (L-), and ultralong- (U-) wavelength bands, which, based on our knowledge, are the best results reported to date among those of the HLPG-based OAM mode generators. The proposed component may find potential applications in the OAM mode division multiplexing (MDM) system combined with the wavelength division multiplexing technique. [ABSTRACT FROM AUTHOR]

A method of engineering spectrum of mode converter based on cascaded Bragg gratings is investigated in detail. Due to the cascaded structures, the proposed mode converter owns higher design degrees of freedom comparing with mode converter based on traditional Bragg grating. Meanwhile, thanks to various light responses of gratings, conversion spectrum can be easily tailored by designing grating structures. As examples, mode converters with specific conversion spectra such as single-band pass, double-band pass, multi-band pass, narrow-band backward spectra have been designed. Besides, the same triangle-shaped band pass spectrum is obtained by two converters based on different grating structures with the aid of distribute-layer-peeling algorithm, which further shows the high design flexibility of the proposed method. We think the proposed method gives a new way for advanced mode converter with required conversion spectrum. [ABSTRACT FROM AUTHOR]

We investigate the impact of accumulated stimulated Raman scattering (SRS) on the nonlinear interference (NLI) variance due to sparse gain-tilt equalization along the optical link. We propose simple modifications to analytical models available in the literature, such as the Gaussian noise (GN) or the enhanced Gaussian noise (EGN) models, for reliable NLI estimation in the presence of accumulated SRS. We additionally generalize closed-form expressions of the NLI variance in a GN framework to the new scenario. We validate the models through split-step Fourier method simulations showing the importance of including the gain-tilt equalization period in the model to preserve the accuracy. The proposed model is then used to provide insights on the interplay between the NLI and accumulated SRS. [ABSTRACT FROM AUTHOR]

The power consumption of optical repeater subsystems in a multicore fiber (MCF) link is analyzed via the simulation of an erbium-doped fiber amplifier (EDFA) considering the power consumption of an ancillary function and an EDFA. Ancillary power consumption is attributed to nonessential functions that are required only for the subsystem to operate. In the analysis, the ancillary power consumption of optical repeater subsystems that employ multicore (MC) EDFAs is compared with subsystems that employ multiple conventional single-core (SC) EDFAs to determine whether an MC-EDFA has an advantage over the use of the number of cores ($N_c$) of SC-EDFAs in an MCF link. In a subsystem with a cladding-pumped MC-EDFA, the required sharable ancillary power consumption such that the total power consumption of the repeater subsystem with a cladding-pumped MC-EDFA is smaller than that with $N_c$ of SC-EDFAs, is several tens of watts in the C-band, whereas it is less than 10 W in the L-band. This required sharable ancillary power consumption is converted to a ratio of required sharable ancillary power consumption to ancillary power consumption of a conventional subsystem. The ratios for the C-band is 30–100 %, and most of the ratio values for the L-band are less than 40 % with minimum values of 0 %. However, the L-band cladding-pumped MC-EDFA has a 3-dB poorer noise figure compared to that for SC-EDFA, which makes the L-band cladding-pumped MC-EDFA achieve a higher output power to maintain the optical signal to noise ratio and may introduce the degradation caused by nonlinear optical effects. In contrast, the required sharable ancillary power consumption for a subsystem with a core-pumped MC-EDFA is a few watts and less than 10 W for the C- and L-bands, respectively. This implies that most of the required sharable ancillary power consumption ratio values for the C- and L-bands are less than 10 % and 40 %, respectively. In terms of power consumption, a cladding-pumped MC-EDFA has less advantage over the $N_c$ of SC-EDFAs, and a core-pumped MC-EDFA may have an advantage over the $N_c$ of SC-EDFA if the size of a core-pumped MC-EDFA is reduced to a value smaller than the $N_c$ of the SC-EDFA by integrating MCF amplifier components. [ABSTRACT FROM AUTHOR]

Spectral efficiency (SE) is one of the key metrics for optical communication networks. An important building block for its maximization are optical superchannels, channels that are composed of several subchannels with an aggregate bandwidth larger than the bandwidth of the detector electronics. Superchannels which are routed through the network as a single entity, together with flex-grid routing, allow to more efficiently utilize available bandwidth and eliminate the guard-bands between channels, thus increasing spectral efficiency. In contrast to traditional wavelength division multiplexing (WDM) channels, subchannel spacing and thus superchannel SE is governed by the linewidth and stability of the frequency spacing of the transmitter lasers. Integrated optical frequency combs, particulary the parametrically generated so-called microcombs, which provide optical lines on a fixed frequency grid are a promising solution for low power superchannel laser sources that allow to minimize the SE loss from suboptimal channel spacing. However, it is extremely challenging to realize microcombs with sufficient line power, coherence and line spacing that is compatible with electronic bandwidths. Because the line-spacing generated by most devices is above 40 GHz, demonstrations often rely on additional electro-optic frequency shifter or divider stages to avoid digital-to-analog-converter (DAC) performance degradation when operating at high symbol rates. Here we demonstrate a 52-line superchannel from a single 22 GHz line spacing soliton microcomb. We demonstrate 12 Tb/s throughput with > 10 bits/s/Hz SE efficiency after 80 km transmission and 8 Tb/s throughput (SE > 6 bits/s/Hz) after 2100 km, proving the feasibility and benefits of generating high signal quality, broadband waveforms directly from the output of a micro-scale device with a symbol rate close to the comb repetition rate. [ABSTRACT FROM AUTHOR]

We propose partial multilevel coding (MLC) for optical communications with probabilistic shaping (PS), which improves the signal-to-noise ratio performance and makes information rates more adaptable, while reducing the power consumed by forward error correction. We designed simulation models of partial-MLC and bit-interleaved coded modulation (BICM) implementing the same low-density parity-check code to have almost the same transmission performance in an additive white Gaussian noise channel. The estimated power consumption of the partial-MLC model was about 38∼39% lower than that of the BICM model. Next, we evaluated the effect of nonlinearity on fiber wavelength division multiplexing (WDM) channels in numerical simulations. The results showed that both models behaved similarly regardless of nonlinear noise, illustrating the usefulness of MLC with PS for optical transmissions on WDM channels. [ABSTRACT FROM AUTHOR]