Optical Fiber Channel Research Articles

Geometric Constellation Shaping for Fiber-Optic Channels via End-to-End Learning

End-to-end learning has become a popular method to optimize a constellation shape of a communication system. When the channel model is differentiable, end-to-end learning can be applied with conventional backpropagation algorithm for optimization of the shape. A variety of optimization algorithms have also been developed for end-to-end learning over a non-differentiable channel model. In this paper, we compare gradient-free optimization method based on the cubature Kalman filter, model-free optimization and backpropagation for end-to-end learning on a fiber-optic channel modeled by the split-step Fourier method. The results indicate that the gradient-free optimization algorithms provide a decent replacement to backpropagation in terms of performance at the expense of computational complexity. Furthermore, the quantization problem of finite bit resolution of the digital-to-analog and analog-to-digital converters is addressed and its impact on geometrically shaped constellations is analysed. Here, the results show that when optimizing a constellation with respect to mutual information, a minimum number of quantization levels is required to achieve shaping gain. For generalized mutual information, the gain is maintained throughout all of the considered quantization levels. Also, the results implied that the autoencoder can adapt the constellation size to the given channel conditions.

Построение распределенных микропроцессорных систем управления движением поездов

High material requirements of new relay systems make it impossible to modernize devices within existing areas and require the construction of new interlocking system buildings, which significantly affects the volume of capital investments. Transitioning to microelectronic and microprocessor electronic platforms allows for the design of more compact systems with expanded functional capabilities. In global practice, there is a trend towards widespread use of microprocessor-based interlocking system. However, there is a slow pace of device updates, mainly due to the high cost of microprocessor-based interlocking system, which exceeds by several times the cost of similar relay-based interlocking system. The high performance of computing resources and fiber-optic data transmission channels allows for the design of efficient structures for microprocessor-based interlocking system. The article presents a comparative analysis of the structures of microprocessor-based interlocking system. The implemented decentralized structures solve the issues of reducing investments for the design and construction of the station’s cable network. The advantages of using these systems from the point of view of controlling the transportation process are described, conclusions are drawn on the effective use of the capabilities of modern control systems with integrated subsystems in relation to field-based train traffic control technologies.

Orthant-symmetric four-dimensional geometric shaping for fiber-optic channels via a nonlinear interference model.

Maximizing the data throughput for optical fiber communication via signal shaping has usually been regarded as challenging due to the nonlinear interference and implementation/optimization complexity. To overcome these challenges, in this paper, we propose an efficient four-dimensional (4D) geometric shaping (GS) approach to design 4D 512-ary and 1024-ary modulation formats by maximizing the generalized mutual information (GMI) using a 4D nonlinear interference (NLI) model, which makes these modulation formats more nonlinear-tolerant. In addition, we propose and evaluate a fast and low-complexity orthant-symmetry based modulation optimization algorithm via neural networks, which allows to improve the optimization speed and GMI performance for both linear and nonlinear fiber transmission systems. The optimized modulation formats with spectral efficiencies of 9 and 10 bit/4D-sym demonstrate a GMI improvement of up to 1.35 dB compared with their quadrature amplitude modulation (QAM) counterparts in additive white Gaussian noise (AWGN) channel. Numerical simulations of optical transmission over two types of fibers show that the 4D NLI model-learned modulation formats could extend the transmission reach by up to 34% and 12% with respect to the QAM formats and the AWGN-learned 4D modulation formats, respectively. Results of effective signal-to-noise ratio are also presented, which confirm that the extra gains in optical fiber channel come from the enhanced SNR by reducing the modulation-dependent NLI.

QAM Constellations With Fractional Entropy to Gain in Margin Maximization for Frequency Selective Channels

This letter proposes two approaches to increase the energy gain for the procedure of bit and power allocation in the frequency selective channels. The first one is the use of QAM constellations with optimal probabilistic shaping (PS) instead of the conventional QAM constellations. The second approach is the use of an extended set of QAM constellations with fractional entropy, which is named FQAM. These FQAM constellations are first offered in this work. As the channel examples, we used ADSL channel, fiber optic channel with Bessel filter, and the one with chromatic dispersion. It is shown that for the observed use cases the use of QAM with PS provides the energy gain in the range of 0.25–0.40 dB with respect to the conventional QAM constellations, while FQAM provides the gain in the range of 1.05–1.30 dB.

CD and PMD Effect on Cyclostationarity-Based Timing Recovery for Optical Coherent Receivers

Timing recovery is critical for synchronizing the clocks at the transmitting and receiving ends of a digital coherent communication system. The core of timing recovery is to determine reliably the current sampling error of the local digitizer so that the timing circuit may lock to a stable operation point. Conventional timing phase detectors need to adapt to the optical fiber channel so that the common effects of this channel, such as chromatic dispersion (CD) and polarization mode dispersion (PMD), on the timing phase extraction must be understood. Here we exploit the cyclostationarity of the optical signal and derive a model for studying the CD and PMD effect. We prove that the CD-adjusted cyclic correlation matrix contains full information about timing and PMD, and the determinant of the matrix is a timing phase detector immune to both CD and PMD. We also obtain other results such as a completely PMD-independent CD estimator, etc. Our analysis is supported by both simulations and experiments over a field implemented optical cable.

On off keying line coding based optical transmitter for various both optical fiber communication and OWC channels

Abstract This paper demonstrated the on off keying line based optical line transmitter for different fiber communication and wireless lighted channels. The max Q form and min BER values after PIN receiver based optical fiber base band channel, linear multi-mode fiber channel and OWC at optimum length is clarified. Lighted power variations after light fiber channel, linear multi-mode fiber channel and OWC versus spectral base band wavelength variations at optimum length is demonstrated. Lighted power form variations after lighted base band fiber channel, linear multi-mode fiber channel and OWC versus time variations at optimum length is indicated. Total lighted power after optical fiber base band channel, linear multi-mode fiber channel and OWC at optimum length is clarified. Total electrical power after PIN receiver based optical fiber channel, linear multi-mode fiber channel and OWC at optimum length.

Bipolar alternate mark inversion encoding (BAMI) scheme for performance signature of optical transceiver systems under thermal effects

Abstract This study has clarified the bipolar alternate mark inversion encoding scheme for performance signature of optical transceiver systems under thermal effects. The light power through optical fiber channel variations with spectral wavelength at various temperature variations are clarified. The total electrical power through PIN receiver at various temperature variations are demonstrated. The electrical power amplitude, max Q Factor and min BER through PIN receiver at different temperature variations are clarified in details. Electrical and optical signal per noise ratio with laser bias current at various ambient temperatures are demonstrated. The total optical/electrical power and maximum quality signal with laser bias current at various temperature variations.

Noise multiplication and bandwidth of photodetectors employed with Taylor dispersion in micro optical fiber channel system

Abstract This work has clarified the noise multiplication and bandwidth of photodetectors employed with Taylor dispersion in micro optical fiber channel system. The simulation performance evaluation of slide and squeeze film damping and fluidics mechanics. The damping ratio versus gap distance for a cantilever beam and a mass suspended from beams are determined. The damping ratio with gap size for a suspended mass with and without holes is reported. The damping ratio variations with the gap distance variations for a mass suspended from beams is clarified. The velocity field for fluid flow in a circular channel, a square channel, a rectangular channel, a parabolic channel and a triangular channel is estimated. Besides the velocity field for the fluid flow in a channel with and without slip is outlined. The spreading of a diffusion front in one dimension in a resting fluid and the dispersion coefficient in a square channel [Taylor dispersion in micro fluidic channels] are clarified. The 2D diffusion profile of a solute in a T mixer and normalized concentration versus the channel width for the solute at the outlet of H filter are determined.

INVESTIGATION OF PSK/QAM MODULATED HYBRID FIBER OPTIC AND FREE SPACE OPTIC SYSTEM UNDER VARIOUS ATMOSPHERIC LOSSES

This research aims to investigate how effectively digital modulation performs to transfer data via hybrid fiber optic and free space optic (FO-FSO) channels for last-mile communication systems. Digital modulation techniques investigated are phase-shift keying (PSK) 8-PSK, 16-PSK, quadrature amplitude modulation (QAM) 4-QAM, 16-QAM, and 64-QAM. FSO is line-of-sight technology being a solution to a last-mile communication system for the challenge of fiber optic cables installation. Combining FSO with fiber optic technology avoids bending losses and the implementation challenges of fiber optic cables in metropolitan areas and between buildings. But atmospheric challenges such as haze, fog, and rain cause signal loss while transmitting data in free space. Also, atmospheric turbulence and antenna misalignments lead to signal error. This paper proposed the models of QAM and PSK digital modulated signal transmission over FO-FSO and compared the results to better fiber optic-FSO links to achieve a last-mile communication network. This fiber optic and FSO model is analyzed for the distance up to 100 km of fiber optic channel and 0.4-1.5 km of FSO channel. Constellation diagrams and error-vector magnitude (EVM) concerning received power at the receiver are compared to analyze FSO channel capacity for various weather attenuations.

Geometrically-Shaped Multi-Dimensional Modulation Formats in Coherent Optical Transmission Systems

Shaping modulation formats in multi-dimensional (MD) space is an effective approach to harvest spectral efficiency gains in both the additive white Gaussian noise (AWGN) channel and the optical fiber channel. In the first part of this paper, existing MD geometrically-shaped modulations for fiber optical communications are reviewed. It is shown that large gains can be obtained by exploiting correlation in the dimensions or/and by increasing the cardinality of the modulation format. Practical limitations and challenges are also discussed together with efficient solutions. In the second part, we extend the recently proposed four-dimensional (4D) modulation format family based on the constraint of orthant-symmetry to high spectrum efficiencies up to 10 b/4D-sym by maximizing generalized mutual information for AWGN channel. Reach increases of up to 25% for a multi-span optical fiber transmission system are reported. Lastly, with the help of a recently introduced nonlinear interference (NLI) model, an optimization for designing nonlinear-tolerant 4D modulation formats is introduced for a single-span optical fiber system. Simulation results show that the proposed NLI model-based 4D modulation format could increase the effective SNRs by 0.25 dB with respect to the AWGN channel-optimal 4D modulation format.

Long Distance Transmission in Optical-IDMA System

In optical fiber communication system the transmission of signal through optical fiber in long distance with less repeaters can reduce the system’s cost and maintain the signal quality. For long-distance transmission Nonlinear effect and dispersion increases with distance and degrade the signal quality of the optical-interleave Division multiple Access (O-IDMA) system. To reduce Nonlinear effect and dispersion Gaussian pulse has been replaced by Solitons and evaluate the performance. MATLAB has been opted to simulate the Optical fiber channel based IDMA system. Simulation outcomes shows that Solitons may be better option in place of Gaussian pulse for long distance transmission.

Impact of the input OSNR on data-driven optical fiber channel modeling

The data-driven approach is promising for computationally efficient modeling of optical fiber channels. Here, for the first time to our knowledge, we investigate the impact of the input optical signal-to-noise ratio (OSNR) on the accuracy of data-driven modeling for optical fiber channels, based on a conditional generative adversarial network (cGAN). Initially, considering a single span of 80 km of standard single mode fiber (SSMF), we vary the launched optical power for the ease of emulating both linear and nonlinear transmission scenarios. When the input OSNR of a root raised cosine (RRC)-shaped 16 quadrature amplitude modulation signal with a roll-off factor of 0.1 varies, we identify that there occurs an OSNR threshold for accurately modeling a single span of 80 km of SSMF in order to reach the normalized mean square error of less than 0.02 in relevance to the traditional split-step Fourier method. The OSNR thresholds are 19 dB and 21 dB, respectively, under scenarios of linear and nonlinear transmissions. Moreover, we verify that the OSNR threshold of accurate modeling is insensitive to both the modulation format and the RRC shaping of the input signal. Furthermore, we find that the cascaded use of cGAN well-trained for the single SSMF span is capable of modeling the multiple-span SSMF transmission in the case that the input OSNR threshold of 22.6 dB is satisfied. We believe that the identification of the OSNR threshold for data-driven optical fiber channel modeling is useful for the accurate and efficient emulation of long-haul fiber optical transmission.

Transmitter optimization for PS-QAM signal in high spectral efficiency metro-transmission

Probabilistic constellation shaping (PCS) brings unprecedented flexibility to future optical networks. However, PCS combined with higher-order modulation formats and higher symbol rates puts more demands on the transmitter. For metro-transmission with high spectral efficiency (SE), transmitter impairments are responsible for a major portion of the system constraints. To address this issue, in this work we study the impact of transmitter impairments on probabilistically shaped quadrature amplitude modulation (PS-QAM) signals. First, we investigate the impact of transmitter impairments and radio frequency (RF) amplifier noise on the optimum shaping factor and the modulation depth within a fiber link. Then, we explore how generalized mutual information (GMI) and the shaping factor are affected by the noise from the transmitter. Next, we first jointly optimize the arcsine swing and the clipping ratio, in order to mitigate the transmitter impairments for the PS-QAM signal, when the modulation depth, the noise from the transmitter, the noise from the fiber optical channel, and the shaping factor are fixed. Then, we verify its validity for various configurations of transmission system. The optimized parameters primarily depend on the noise from the transmitter and turn out to be insensitive to the noise from the fiber optical link and the shaping factor. Finally, we experimentally verify the optimization strategy with PS-256QAM in back-to-back (B2B) transmission.

Scaling waveguide-integrated superconducting nanowire single-photon detector solutions to large numbers of independent optical channels.

Superconducting nanowire single-photon detectors are an enabling technology for modern quantum information science and are gaining attractiveness for the most demanding photon counting tasks in other fields. Embedding such detectors in photonic integrated circuits enables additional counting capabilities through nanophotonic functionalization. Here, we show how a scalable number of waveguide-integrated superconducting nanowire single-photon detectors can be interfaced with independent fiber optic channels on the same chip. Our plug-and-play detector package is hosted inside a compact and portable closed-cycle cryostat providing cryogenic signal amplification for up to 64 channels. We demonstrate state-of-the-art multi-channel photon counting performance with average system detection efficiency of (40.5 ± 9.4)% and dark count rate of (123 ± 34) Hz for 32 individually addressable detectors at minimal noise-equivalent power of (5.1 ± 1.2) · 10-18 W/Hz. Our detectors achieve timing jitter as low as 26ps, which increases to (114 ± 17) ps for high-speed multi-channel operation using dedicated time-correlated single photon counting electronics. Our multi-channel single photon receiver offers exciting measurement capabilities for future quantum communication, remote sensing, and imaging applications.

Hybrid Raman/EDFA optical fiber amplifiers configuration in amplified ultra wide band wavelength division multiplexed systems

Abstract This paper presented the hybrid Raman and erbium doped fiber amplifiers in amplified wavelength division multiplexed systems. Important role of singly and hybrid light amplifiers are clarified in the presented work. EDFA/RAMAN based average power model based Raman amplifiers are used for strength the signal power levels. CW laser with return to zero code are employed in amplified multiplexed systems. The optimum EDFA optical amplifiers length is used to strength the signal through the optical fiber channel. The max. signal quality and min. error rates are obtained with the presented model. By the assistance of multi pumped lasers for the flat gain in the hybrid EDFA/Raman light amplifiers.

Optimization of the performance parameters of the Giga passive optical networks for high transmission data rates with various modulation schemes

Abstract This article has demonstrated the performance parameters optimization of the Giga passive optical networks (PONs) can enhanced with high transmission data rates with various modulation schemes. These modulation schemes are Mach–Zehnder modulator (MZM), electroabsorption modulator (EAM), amplitude modulator (AM), dual drive MZM measured (DDMZMM), electroabsorption modulator measured (EAMM), and LiNb MZM. The network reach can be extended to 30 km with 20 Gb/s. Maxi Q and mini bit error rate can be measured at both PIN and APD receivers. The study has emphasized AM modulation scheme is the best candidate modulation scheme for upgrading the network performance efficiency. LiNb MZM is the worst modulation scheme for the estimation of PONs performance. Optical power signals after fiber optic channel based different modulation schemes are clarified. EAM modulation scheme is the best technique for upgrading optical power signal through the network reach.

Optical parametric oscillator with quantum memory for quantum repeaters

We consider preparing entangled states between single photons and quantum memory by combining two-photon source based on spontaneous parametric down-conversion and multiatomic quantum memory in a common resonator. The scheme allows one to minimize the losses while the photon to be stored is propagating from the source to the quantum memory and avoids the need to synchronize their operating wavelength. In this respect, the scheme is analogous to the cavity-enhanced embedded memory within Duan-Lukin-Cirac-Zoller approach, but it remains possible to generate a second photon at the wavelength of the fiber optic communication channel and use various multiplexing methods inherent in multiatomic quantum memory.

Принципи побудови телемедичних мереж і систем на основі волоконно-оптичних каналів зв’язку у Вінницькій області

The article draws a conclusion using the biblio-semantic approach regarding the perspective of creating optoelectronic networks for the exchange of telemedical data, formulated a range of unsolved problems and identified the main directions of their development. The development based on the model of the telemedical data transmission information channel of the fiber-optic communication channel for the exchange of telemedical information with the additional introduction to its structure of optical amplifiers with automatic gain control (AMP) and the unit of automatic control and diagnostics of the optical cable provided remote control with state determination cable fibers; automatic diagnosis of the condition of the cable with an accurate determination of the location and nature of the damage, linking of reflectors to the geographical map of the area and analysis of changes in the parameters of the VOKZ over time, which ultimately increased the reliability and improved the quality of the transmission of biomedical information. automatic . The development of a fiber-optic telemedicine network for the exchange of operational results of telemedical diagnostics and health monitoring of patients in remote areas of the Vinnytsia region through fiber-optic communication channels will in the future ensure its adaptation to the DICOM standard, information support for decision-making, and a flexible work management system network in compliance with the requirements for the protection of personal data of patients.

Волоконно-оптичні технології в інформаційних (internet, intranet тощо) та енергетичних мережах

The article draws a conclusion using the biblio-semantic approach regarding theperspective of creating optoelectronic networks for the exchange of telemedical data, formulateda range of unsolved problems and identified the main directions of their development. Thedevelopment based on the model of the telemedical data transmission information channel of thefiber-optic communication channel for the exchange of telemedical information with theadditional introduction to its structure of optical amplifiers with automatic gain control(AMP) and the unit of automatic control and diagnostics of the optical cable provided remotecontrol with state determination cable fibers; automatic diagnosis of the condition of the cablewith an accurate determination of the location and nature of the damage, linking of reflectors tothe geographical map of the area and analysis of changes in the parameters of the VOKZ overtime, which ultimately increased the reliability and improved the quality of the transmission ofbiomedical information. automatic . The development of a fiber-optic telemedicine network forthe exchange of operational results of telemedical diagnostics and health monitoring of patientsin remote areas of the Vinnytsia region through fiber-optic communication channels will in thefuture ensure its adaptation to the DICOM standard, information support for decision-making,and a flexible work management system network in compliance with the requirements for theprotection of personal data of patients.

The effects of optical fiber impairments on communication systems

In this paper, the influence of physical layer impairments on fiber optic channels was evaluated using analytical modeling, and the findings were verified through simulation results. Light propagation inside standard single mode fiber (SSMF) is affected by both linear and nonlinear effects, which must be taken into account in order to develop an appropriate fiber channel model. The use of nonlinear fiber optics in the implementation of highcapacity optical networks is crucial. The "Optisystem 17.0" software package was used to simulate the suggested systems. It can be observed that increased input power tends to increase the effect of cross-phase modulation (XPM) and four wave mixing (FWM) in the nonlinear dispersive fibers. The impact of pulse broadening due to chromatic dispersion (CD), self-phase modulation (SPM), and cross-phase modulation (XPM) was investigated using Gaussian pulses as input signals.