Fiber Channel Research Articles

Seven-channel 1 Gbps TWDM coexistence architecture supporting 65 Gbps optical link for next-generation passive optical network 2–based FTTX access networks

Abstract In this paper, we have presented the design and simulation of a 7-channel next-generation passive optical network (NG-PON2) network for the deployment of Fiber-to-the-X (FTTX) access network. Coexistence architecture is proposed, designed and simulated for the implementation of NG-PON2 access network. In a coexistence architecture approach, legacy PON networks like Gigabit passive optical network (GPON) PON, 10GPON, etc. and wavelength division multiplexing (WDM)-PON supporting point-to-point connectivity are designed and simulated together. A 4 × 4 WDM-PON in which each channel carrying data at 2.5 Gbps data rate is capable of supporting a throughput channel capacity of 65.5 Gbps. NG-PON2 network is designed and simulated at 187.1, 187.2, 187.3 and 187.5 to 187.8 THz wavelengths in downstream direction for different link distances from 40 to 80 km looking into the requirement of reach of access network for future cities. The network performance parameters such as bit error rate (BER), quality factor (Q-factor), signal-to-noise ratio using the Optisystem-16 simulator at above data rates and link distances. Further, channel capacity estimation is done for single-mode fiber channel coexistence NG-PON2 configuration up to 80 km supporting BER e-13 and Q-factor 7 for WDM link and BER e-12 and Q-factor 7 for a legacy network supporting almost-1 Gbps data rate to 65 users and 100 Mbps to 512 user.

Mismatched Models to Lower Bound the Capacity of Optical Fiber Channels

A correlated phase-and-additive-noise (CPAN) mismatched model is developed for wavelength division multiplexing over optical fiber channels governed by the nonlinear Schr\"odinger equation. Both the phase and additive noise processes of the CPAN model are Gauss-Markov whereas previous work uses Wiener phase noise and white additive noise. Second order statistics are derived and lower bounds on the capacity are computed by simulations. The CPAN model characterizes nonlinearities better than existing models in the sense that it achieves better information rates. For example, the model gains 0.35 dB in power at the peak data rate when using a single carrier per wavelength. For multiple carriers per wavelength, the model combined with frequency-dependent power allocation gains 0.14 bits/s/Hz in rate and 0.8 dB in power at the peak data rate.

Securing the enterprise SAN with IBM Fibre Channel Endpoint Security

Controlling access to and privacy of data within the enterprise can prove to be a formidable task with increased complexity and management overhead encountered as the granularity of access control is increased. Fibre Channel is the premier enterprise storage transport, so an organization's most sensitive data flows over Fibre Channel links within and across datacenters. In this article, we discuss a new, easy way to deploy innovation for Fibre Channel connections that ensures data is exchanged only between trusted servers and storage controllers, while also enabling the integrity and confidentiality of the data in flight between the trusted entities. We explain how the components of IBM Fibre Channel Endpoint Security are configured to work together to provide protection from insider threats, requiring minimal steps to deploy, fully controlled via policy, and transparent to applications, middleware, and operating systems.

Real-time calibration of coherent-state receivers: Learning by trial and error

The optimal discrimination of coherent states of light with current technology is a key problem in classical and quantum communication, whose solution would enable the realization of efficient receivers for long-distance communications in free-space and optical fiber channels. In this article, we show that reinforcement learning (RL) protocols allow an agent to learn near-optimal coherent-state receivers made of passive linear optics, photodetectors and classical adaptive control. Each agent is trained and tested in real time over several runs of independent discrimination experiments and has no knowledge about the energy of the states nor the receiver setup nor the quantum-mechanical laws governing the experiments. Based exclusively on the observed photodetector outcomes, the agent adaptively chooses among a set of ~3 10^3 possible receiver setups, and obtains a reward at the end of each experiment if its guess is correct. At variance with previous applications of RL in quantum physics, the information gathered in each run is intrinsically stochastic and thus insufficient to evaluate exactly the performance of the chosen receiver. Nevertheless, we present families of agents that: (i) discover a receiver beating the best Gaussian receiver after ~3 10^2 experiments; (ii) surpass the cumulative reward of the best Gaussian receiver after ~10^3 experiments; (iii) simultaneously discover a near-optimal receiver and attain its cumulative reward after ~10^5 experiments. Our results show that RL techniques are suitable for on-line control of quantum receivers and can be employed for long-distance communications over potentially unknown channels.

Permeation behavior of low-melting-point Sn–Bi alloy in the fiber channel of pine wood

Wood and metal are the two most common materials, both with distinct advantages and disadvantages. Through the metallization process, the inherent defects of the two materials can be avoided, so that the composite material exhibits excellent structural properties and anisotropy. In this study, the pine wood was pretreated with dilute ammonia (5%), and then the low melting point Sn–Bi alloy was filled into the pine fiber without lignin at 180 °C and 3000 Pa. The density of metallic wood is about 3 times that of pine, while the impact toughness can be up to 2 times that of pine. By building the capillary buddle model, the filling mechanism of molten metal in pine wood was analyzed, and it was clear that high vacuum, high temperature, large porosity and large tracheid diameter are the conditions for rapid penetration. The conductive anisotropy was found on metalized wood, making metalized wood available in different places with requirements for electromagnetic shielding and antistatic.

Dissipative dynamics of quantum states in the fiber channel

In this paper we consider the Liouville equation that describes the quantum nonunitary dynamics of quantum states in optical fiber. We consider a particular case of thermalization aiming to applications related to various quantum information protocols; however, the model can be generalized in various ways taking into account more features (external pump, nonlinear interactions, continuous spectra, free space propagation, etc.). In order to obtain the appropriate evolution models for states in the channel we use the $\text{su}(1,1)$ algebra formalism in the Liouville representation. The developed model is applied in cases of two different initial states as an example. The first is single- and multifrequency-mode (e.g., wavelength-division-multiplexed) weak coherent states in quantum notation as a rather simple but useful example. This particular example is of interest since weak coherent states are a commonly used tool in various fields of optics, e.g., optical communication, quantum key distribution, etc. Results for coherent states are well agreed upon with classical theories; however, in order to highlight quantum features of developed theory we also consider the case of nonclassical light, in particular, Fock states. Considered implementation of the model takes into account dichroism, retardance, thermalization, dispersion, and decoherence in the polarization domain. We derive expressions of evolved states, mean photon number, and estimate the Stokes parameters as well as the degree of polarization. Considered examples explicitly demonstrate all the features and effects of the developed approach. The described approach allows one to connect the information properties of quantum channels with its physical ones. In order to illustrate this statement we consider BB84 quantum key distribution protocol and investigate the behavior of the quantum bit error rate affected by considered physical phenomena in an optical fiber.

Optimization of Probabilistic Shaping for Nonlinear Fiber Channels with Non-Gaussian Noise.

Probabilistic constellation shaping is investigated in the context of nonlinear fiber optic communication channels. Based on a general framework, different link types are considered—1. dispersion-managed channels, 2. unrepeatered transmission channels and 3. ideal distributed Raman amplified channels. These channels exhibit nonlinear effects to a degree that conventional probabilistic constellation shaping strategies for the additive white Gaussian (AWGN) noise channel are suboptimal. A channel-agnostic optimization strategy is used to optimize the constellation probability mass functions (PMFs) for the channels in use. Optimized PMFs are obtained, which balance the effects of additive amplified spontaneous emission noise and nonlinear interference. The obtained PMFs cannot be modeled by the conventional Maxwell-Boltzmann PMFs and outperform optimal choices of these in all the investigated channels. Suboptimal choices of constellation shapes are associated with increased nonlinear effects in the form of non-Gaussian noise. For dispersion-managed channels, a reach gain in 2 spans is seen and across the three channel types, gains of >0.1 bits/symbol over unshaped quadrature-amplitude modulation (QAM) are seen using channel-optimized probablistic shaping.

Analysis of Factors Affecting FWM Inter-Channel Crosstalk Based on VPI

To study the effect factors of inter-channel crosstalk caused by FWM in optical fiber communication and improve communication system performance, we build a simulation system on VPI, observe the changes of optical spectrum of the output, signal power diagrams and the eye diagrams of receiving channels, analyze the effects on FWM produced by different fiber parameters, channel spacing and optical signal power. The results show that the crosstalk between four wave mixing channels will be more serious with the increase of optical signal power, however, increasing the optical fiber’s dispersion coefficient and the effective area of the core can suppress FWM effectively, at the same time, increasing the frequency channel spacing can also reduce the FWM.

Post-Processing Protocol for Physical-Layer Key Generation and Distribution in Fiber Networks

The unique and random physical-layer properties of optical fiber channels have been exploited for a simple and cost-effective secure key generation and distribution (SKGD). However, state-of-the-art SKGD approaches focused mainly on initial key extraction, while the post-processing protocol has to be explored to guarantee error-free operation, effective key generation rate (KGR) and high key secrecy. Here we propose a full post-processing protocol for SKGD in fiber networks. A lossy quantizer is optimized to achieve the trade-off between the KGR and key disagreement rate. The distributed source coding based information reconciliation is used to remove quantization errors. The privacy amplification is applied to improve the randomness and secrecy of the generated key using hashing functions. The post-processing protocol provides a SKGD solution of error-free, high randomness and high secrecy in fiber networks.

In situ simultaneous encapsulation of defective MoS2 nanolayers and sulfur nanodots into SPAN fibers for high rate sodium-ion batteries

Molybdenum sulfide (MoS2) with layered structure has emerged as a promising anode material for sodium ion batteries (SIBs) in light of its particular surface chemistry and physical structures. However, the MoS2-based SIBs usually suffered from the weaknesses of the low rate capability and poor cycling stability induced by the sluggish kinetics of Na+ intercalation and the diffluent discharge products. Herein, the defective MoS2 nanocrystals and sulfur nanodots simultaneously embedded in sulfurized polyacrylonitrile (SPAN) fibers were fabricated via an electrospunning technology, followed by a simple annealing treatment. The unique architecture, in which MoS2 nanolayers and sulfur nanodots were mounted inside the SPAN fiber, provided multi-entry and short-range channel for sodium ion to ensure a fast kinetics. Besides, sulfur defects within MoS2 produced the strong chemical interaction for fixing soluble discharge products. As a result, the electrode performed outstanding sodium-storage performance with a superior long cycling life (8000 cycles at 5 A g−1, 15,000 cycles at 10 A g−1) and excellent rate capability (212 mAh g−1 at 25 A g−1). The full cell fabricated by using Na3V2(PO4)3 as the cathode also delivered good energy storage performance and successfully powered a group of light-emitting diode.

Design and performance analysis of a novel secure communication system based on optical code division multiple access technology

Abstract In order to enhance the physical-layer security of the communication systems in the optical fiber channel, a novel secure communication scheme based on optical code-division multiple-access (OCDMA) technology is proposed and its physical-layer security is quantitatively analyzed. Due to the small capacity of the traditional OCDMA codewords, the address code used by legitimate user is vulnerable to the brute-force searching attack. To solve this issue, a new type of 2-D wavelength-hopping/time-spreading (WH/TS) code with large capacity is constructed at first. Based on information-theoretic security, the wiretap channel model of this secure communication system is established, and the secrecy capacity is employed to evaluate the physical-layer security level. The simulation results indicate that the novel secure communication system can provide a high-speed and long-haul secure transmission and it is important to get the optimal parameter values to improve the system security.

Optical orthogonal code generation scheme and grouping of codes for optical CDMA systems

To exploit the attractive features of CDMA systems and the tremendous bandwidth provided by optical communication such as fiber, VLC, and Li-FI channel, a new system is emerging and is known as optical code division multiple access. These systems require optical orthogonal codes (OOCs). This paper presents an algorithm to design OOCs and determines the auto-correlation ( $$\lambda _a$$ ) and cross-correlation ( $$\lambda _c$$ ) constrains of codes. The grouping of these OOCs for desired $$\lambda _a$$ and $$\lambda _c$$ is done using a low complexity bipartite method. Design of codes, groups, and simulation for performance analysis in terms of multiple access interference is done using MATLAB programming. The bipartite scheme for grouping finds all possible groups and it reduced the time of computation. The memory requirement of the scheme is also reduced together with computational complexity.

Simulation studies on polarization modulated vertical cavity surface emitting laser for combined fiber and free space optical links

In this work, polarization property of Vertical Cavity Surface Emitting Laser (VCSEL) is investigated for 5 Gbps optical data transmission in a combined link comprising of Single Mode Fiber (SMF) and Free Space Optic (FSO) channel. The VCSEL considered for simulation is biased just above threshold with RZ current pulses to emit narrow polarized optical pulses. After 20 km SMF link, the received power is launched into two different paths using an optical splitter. It is received by an InGaAs PIN photodiode in one path and a coupling lens in other. A split ratio of 2%, provides the minimum power required for the SMF link to maintain a BER ≤10−12, based on the VCSEL considered in the study. The remaining 98 % of power is utilised for FSO transmission beyond the SMF link. The maximum FSO link distances under various loss combinations were found for the two polarized optical pulses, separately. For BER≤10−12, under the combined influence of all losses, an FSO link length of 130 m and 119 m, for x and y polarizations are predicted.

RZ Line Coding Scheme With Direct Laser Modulation for Upgrading Optical Transmission Systems

Abstract This study reports the efficient use of a direct laser modulated response measured with the return-to-zero coding scheme in optical transmission systems. The measured direct laser modulated response has a bit rate of 1.2 Gbps for an optical fiber cable of a transmission length of 10 km. The eye diagram analyzer is used to calculate the maximum quality factor and minimum bit error rate of the proposed model. The maximum quality factor is 531.2, and the minimum bit error rate tends to zero for the same optical fiber channel length compared with that of the previous model. The proposed model provides better results than the previous model. The figures of the proposed model are more stable than those of its previous counterpart. Bit error rate approximately tends to zero in the proposed model.

Trojan Horse Attacks, Decoy State Method, and Side Channels of Information Leakage in Quantum Cryptography

Early proofs of key secrecy in quantum cryptography systems were based on the assumption that the transmitting and receiving stations are completely isolated from the outside world—the eavesdropper. However, this condition cannot be implemented in practice since quantum cryptography systems are open systems in the sense that the eavesdropper may have indirect access, for example, through a fiber communication channel, to the critical elements of the equipment (phase modulators, intensity modulators, etc.) using active probing of the state of these elements. The state of the elements carries information about the transmitted key. In addition, the eavesdropper can use passive detection of side radiation from the receiving and transmitting equipment. Signals in side channels of information leakage may have extremely low intensity and are actually quantum signals. The eavesdropper may use the joint measurement of quantum information states in the communication channel and of states in various side channels of information leakage. The paper considers both passive attacks with measurement of side radiation and active attacks involving the probing of the states of the phase modulator and the intensity modulator, as well as backscattering radiation of single-photon avalanche detectors, which occurs during detecting information states on the receiver side. Combined attacks are also considered. The decoy state method is generalized with regard to active probing attacks, and boundaries for state parameters in side communication channels are obtained that guarantee secret key distribution for a given length of the communication channel.

Path Integral Approach to Nondispersive Optical Fiber Communication Channel.

In the present paper we summarize the methods and results of calculations for the theoretical informational quantities obtained in our works for the nondispersive optical fiber channel. We considered two models: the per-sample model and the model where the input signal depends on time. For these models we found the approach for the calculation of the mutual information exactly in the nonlinearity parameter but for the large signal-to-noise power ratio. Using this approach for the per-sample model we found the lower bound of the channel capacity in the intermediate power range.

Ultra-High Capacity FSK Transmission Using Silicon Microring Embedded Gold Grating Circuits

The Frequency Shift Keying (FSK) dual-transmission mode for short-range communication using the silicon microring resonator arrangement is proposed. FSK generated by an optical modified add-drop multiplexer embedded gold grating connected to three other microring resonators. The proposed system consists of a transmitted microring with two nano-ring phase modulators, which connected through a 10 km fiber channel to a receiver. The user end consists of three similar microring systems. A gold grating embedded on two side ring center (sensor probe) to introduce the plasmonic polariton, from which each of sensor probe identified by the Bragg wavelength. The frequency of n photonic oscillator is in the range of plasmonic frequencies, where the Whispering Gallery Mode (WGM) due to the light propagations can be obtained by controlling the used two sides smaller ring resonator in the proposed ring structures. The WGM beam can be used as another mode of transmission called light fidelity (LiFi) transmission. In manipulation, the FSK light source wavelength of 1.55 μm fed into the system. The transmission bit rates of 200 Tbits−1is achieved. The Bit Error Rate (BER) obtained at the user ends increases with increasing input power. Each sensor node identified the Bragg wavelength, while the change in Bragg wavelength on each sensor obtained and shown the linear trend, which is useful for sensing application. In applications, the proposed system is capable of dual mode of transmission either cable or wireless and in this case, the cable transmission of data using LiFi is more reliable than WiFi in terms of security, efficiency, availability, and safety.

Evaluation of a position-sensitive prototype detector unit for fast neutron imaging and spectroscopy

A novel fast neutron scatter camera with capabilities of neutron imaging and spectroscopy is under development. The detection principle is based on multiple neutron–proton (n–p) elastic scattering interactions in organic scintillator. In order to improve position measurement accuracy of recoil protons, a position-sensitive prototype detector unit has been designed and characterized experimentally. The presented detector unit consisted of a plastic scintillator sheet of 10 cm × 10 cm × 1 cm dimensions and two groups (6 × 2) of wavelength-shifting fibers with orthogonal directions embedded into grooves on two opposite scintillator surfaces. Scintillation signals were read out by silicon photomultipliers (SiPMs). A collimated Sr-90 radioactive source was utilized for system calibration and position resolution measurement. Light output of the unidimensional six fiber channels from one side of the detector unit was calibrated to be 14.45 photoelectrons per MeVee. Position resolution of the detector unit was measured to be 0.35–0.44 times fiber pitch, corresponding to 5.48 mm for proton recoil energy interval of 1.63–2.60 MeV, and 4.60 mm for proton recoil energy interval of 4.82–5.50 MeV. Energy threshold for recoil proton localization was estimated to be 1.18 MeV. The results shown satisfy basic requirements of the scatter camera, while space exists for further improvements. The positioning performance optimization consists of three aspects. The first one is to increase the fiber diameter so as to reduce signal loss. The second one is to depress dark rate of the SiPMs. The last one is to decrease the number of channels involved in position reconstruction by narrowing the scintillation signal distribution function of the detector unit.

Data-driven Optical Fiber Channel Modeling: A Deep Learning Approach

A data-driven fiber channel modeling method based on deep learning (DL) is introduced in an optical communication system. In this study, bidirectional long short-term memory (BiLSTM) is selected from a diverse range of DL algorithms to perform fiber channel modeling for on-off keying and pulse amplitude modulation 4 signals. Compared with the conventional model-driven split-step Fourier (SSF)-based method, the proposed method yields similar results based on the comprehensive comparison of multiple characteristics associated with the generated optical signals, including the optical amplitude and phase waveforms in the time domain, optical spectrum components in the frequency domain, and eye diagrams after detection in the electrical domain. Additionally, the effects of multiple factors on the modeled fiber channel have also be investigated, including fiber length, fiber nonlinearity, dispersion, data pattern, pulse shaping, and sample rate. The satisfactory fitting results and acceptable mean square errors indicate that the approximate transfer function of the fiber channel is learned by the BiLSTM. Moreover, compared with repetitive iteration SSF, the computing time is significantly reduced by the BiLSTM owing to its independence on fiber length and insensitivity to data size and launch power. Our aim is to demonstrate the BiLSTM is comparable with the conventional model-driven SSF-based method for direct-detection optical fiber system. We think the proposed method could be a supplementary technique that can be used for the existing simulation system and could also be a potential option for future simulation methods.

Nonlinear-frequency-packing nonlinear frequency division multiplexing transmission.

A nonlinear frequency division multiplexing (NFDM) transmission system, designed specifically for nonlinear fiber channel, has the potential to overcome the nonlinear Shannon capacity limit. However, the spectral efficiency (SE) of the current proven NFDM transmission systems is still lower than that of the analogous orthogonal frequency division multiplexing system. It is extremely necessary to explore effective modulation scheme for the aim of increasing the SE of NFDM system. In this study, we first propose the nonlinear-frequency-packing nonlinear frequency division multiplexing (NFP-NFDM) transmission system. In NFP-NFDM, the spacing of nonlinear subcarriers is squeezed and more nonlinear subcarriers can be packed, but the inter carrier interference (ICI) is introduced. The method of NFP in nonlinear Fourier domain is carefully designed to reduce the complexity of ICI cancellation. Through numerical simulation, we illustrate the feasibility of NFP-NFDM transmission, and higher SE in NFP-NFDM than that of NFDM system is also demonstrated. The upper bound of the normalized SE for NFP-NFDM is estimated, which is higher than that of current NFDM system. Besides, we find out that the NFP scheme may have the advantage of reducing the signal-noise interaction in fiber transmission scenario, which indicates there may be a better way to load the data into the nonlinear Fourier domain.