Optical Fiber Transmission Research Articles

Low cost O-band inter-datacenter interconnect utilizing a 4-bit resolution digital-to-analog converter for PAM-4 signal generation.

In this paper, we experimentally demonstrate the transmission of a 100 Gb/s/λ PAM-4 signal over a 40/80-km single mode fiber (SMF) in the O-band utilizing a 4-bit resolution digital-to-analog converter (DAC) for signal generation. Low resolution DACs are preferred to meet the requirement of low-cost criteria of datacenter interconnects (DCIs). However, large quantization noise introduced by low resolution DACs will deteriorate system performance significantly. Noise shaping (NS) technique is investigated to reduce the quantization noise within the PAM-4 signal band. The experimental results show that the bit error ratio (BER) performance of the signal generated by 4-bit resolution DAC and NS technique will approach that of the signal generated by the 8-bit resolution DAC in the 40/80-km optical fiber transmission system of a 50 Gbaud PAM-4 signal in the O-band, which indicates that our proposed scheme operating in the O-band with a 4-bit resolution DAC and NS technique is a promising candidate for 100 Gbit/s/λ beyond a 40-km Inter-DCI.

Rigorous FM-EDF design with an oversized two-layer erbium ion distribution for C-band DMG mitigation

We present a rigorous design of few-mode erbium doping fiber (FM-EDF) with an oversized two-layer erbium ion distribution at the central region with effective differential modal gain (DMG) mitigation over the C-band. The proposed erbium doping distribution allows for a similar overlapping integral value among the guided modes, leading to a signal gain equalization over the C-band. When the length of the proposed FM-EDF is 8 m under the cladding pumping power of 2.5 W, our calculated results reveal that four linearly polarized (LP)-modes can achieve an average gain per mode of 24.8 dB and a typical DMG of less than 0.64 dB over the C-band. Meanwhile, we carry out numerical simulations to explore the fabrication tolerance of the oversized two-layer erbium doping distribution with respect to the DMG, indicating stable DMG mitigation over the C-band. We believe that such new manipulation of erbium doping distribution is helpful for the multiple-dimensional multiplexing of fiber optical transmission.

Dispersive wave propagation of the nonlinear Sasa-Satsuma dynamical system with computational and analytical soliton solutions

The Sasa-Satsuma equation on a continuous background describes a nonlinear fiber system with higher-order effects including the third-order dispersion and Kerr dispersion. The Sasa-Satsuma equations describe the simultaneous propagation of two ultrashort pulses in the birefringent or two-mode fiber with the third-order dispersion, self-steepening, and stimulated Raman in scattering effects, and govern the propagation of ultra-fast pulses in optical fiber transmission systems. We consider the Sasa-Satsuma equation, which is one of the integrable extensions of the nonlinear Schrödinger equations. We find the functional integral and the Lagrangian of this model. We derived the computational and analytical soliton solutions of the nonlinear Sasa-Satsuma dynamical system. We discuss the stability analysis for our solutions.

Flexible and directional fibre optic ultrasound transmitters using photostable dyes.

All-optical ultrasound transducers are well-suited for use in imaging during minimally invasive surgical procedures. This requires highly miniaturised and flexible devices. Here we present optical ultrasound transmitters for imaging applications based on modified optical fibre distal tips which allow for larger transmitter element sizes, whilst maintaining small diameter proximal optical fibre. Three optical ultrasound transmitter configurations were compared; a 400 µm core optical fibre, a 200 µm core optical fibre with a 400 µm core optical fibre distal tip, and a 200 µm core optical fibre with a 400 µm core capillary distal tip. All the transmitters used a polydimethylsiloxane-dye composite material for ultrasound generation. The material comprised a photostable infra-red absorbing dye to provide optical absorption for the ultrasound transduction. The generated ultrasound beam profile for the three transmitters was compared, demonstrating similar results, with lateral beam widths <1.7 mm at a depth of 10 mm. The composite material demonstrates a promising alternative to previously reported materials, generating ultrasound pressures exceeding 2 MPa, with corresponding bandwidths ca. 30 MHz. These highly flexible ultrasound transmitters can be readily incorporated into medical devices with small lateral dimensions.

Optical modulation using digital image symbol patterns and grating light valve technology in a hybrid multiplexed superchannel

AbstractThe latest research exploits to increase optical channel bandwidth are termed polarization division multiplexing (PDM) and few mode fiber (FMF), which rely upon a complex multiplexed architecture together with customized electro‐optic modulated hardware elements, inhibited by cost implications and technical limitations thereof. The research pursued herein presents an alternate digital image pattern modulated (DIPM) approach to achieve higher bandwidth gains, spectral efficiency (SE), and transmission reach improvement. The solution focuses on reducing implementation cost with a scalable software approach and simplified conceptual hardware design using grating light valve (GLV) technology to address the drawbacks of PDM, FMF, and other conventional optical transmission technologies. Simulation test results for a DIPM‐GLV‐based fiber optic (FO) transmission system and comparisons against conventional and other novel techniques are graphically shown and interpreted, suggesting that DIPM using GLV is a viable high performance and cost efficient solution.

Two-wavelength WDM multiplexers based on combined fiber structures

One of the main directions in the development of optical communication systems is associated with the use of optical fiber (ОF) for data reception and transmission. Therefore, manufacturers began to pay special attention to the creation of new brands of OF, improving their optical and operational characteristics. This makes it possible to improve existing optical fiber components that use OF as an active medium. The most widely used are two-wavelength 1 × 2 WDM multiplexers/demultiplexers designed to separate and combine optical carriers with wavelengths of 1310 and 1550 nm, corresponding to the second and third transparency windows of quartz OF. It should be noted that multiplexers and demultiplexers are the same optical devices, which are spectrally selective splitters. Such devices are distinguished by a sufficiently high level of optical characteristics at a relatively low cost of products. However, an analysis of the multiplexers produced in recent years shows that the characteristics of these devices do not sufficiently correspond to the set of modern requirements imposed by most system developers, in particular on permissible values of external influencing factors, insertion loss and the value of optical isolation of channels. Therefore, the development and research of WDM multiplexers with improved optical characteristics is relevant. One of the possible ways of optimizing such devices using new types of OF with resistance to bending losses, of which WDM multiplexers could be made. In this paper, we consider the possibilities of realizing fused single-mode multiplexers/demultiplexers based on combined fiber structures. The technology and equipment for the manufacture of these devices are presented. The optical characteristics of experimental samples of WDM multiplexers are investigated. The results of testing for the effect of temperature are given.

Adaptive multi-layer filters incorporated with Volterra filters for impairment compensation including transmitter and receiver nonlinearity.

We propose a receiver-side signal processing to compensate for nonlinearity that occurs in transmitter (Tx) and receiver (Rx) components of coherent optical fiber transmission systems. Nonlinear effects in transmission systems are not mutually commutative with any linear effects in general. Considering the order in which all the relevant impairments occur, we adopt a multi-layer (ML) filter architecture. The ML filters consist of strictly-linear and widely-linear filter layers to compensate for relevant linear impairments that occur in a transmission system and two Volterra filter layers to compensate for Rx and Tx nonlinearity. The coefficients of the ML filters including Volterra filter layers are adaptively controlled by using a gradient calculation with back propagation, which is similar to that used in the learning of neural networks, from the last layer and stochastic gradient descent to minimize a loss function that is composed of the last layer outputs. We evaluated the compensation performance of Tx and Rx nonlinearity using the proposed adaptive ML filters including Volterra filter layers both in simulations and experiments of the transmission of a 23 Gbaud polarization-division-multiplexed 64-quadrature amplitude modulation signal over a 100-km single-mode-fiber span. The results demonstrated that the Volterra filter layers in the ML filter architecture could compensate for the nonlinearity that occurs in Tx and Rx simultaneously and effectively even when other impairments such as chromatic dispersion coexist.

Riemann\u2013Hilbert Problem Associated with the Fourth-Order Dispersive Nonlinear Schr\xf6dinger Equation in Optics and Magnetic Mechanics

In this paper, by using Fokas method, we study the initial-boundary value problems (IBVPs) of the fourth-order dispersive nonlinear Schrödinger (FODNLS) equation on the half-line, which can simulate the nonlinear transmission and interaction of ultrashort pulses in the high-speed optical fiber transmission system, and can also describe the nonlinear spin excitation phenomenon of one-dimensional Heisenberg ferromagnetic chain with eight poles and dipole interaction. By discussing the eigenfunctions of Lax pair of FODNLS equation and analyzing symmetry of the scattering matrix, we get a matrix Riemann–Hilbert (RH) problem from for the IBVPs of FODNLS equation. Moreover, we get the potential function solution u(x, t) of the FODNLS equation by solving this matrix RH problem. In addition, we also obtain that some spectral functions satisfy an important global relation.

Recent Advancement in Power-over-Fiber Technologies

Power-over-fiber is a power transmission technology using optical fibers that offers various features not available in conventional power lines, such as copper wires. The basic configuration of power-over-fiber comprises three key components: light sources, optical fibers, and photovoltaic power converters. This review article presents the features of power-over-fiber and its key components. Moreover, recent advancement in power-over-fiber technologies based on their latest results is introduced, focusing primarily on papers presented at the Optical Wireless and Fiber Transmission Conferences (OWPT) from 2019 to 2021.

Wavelength dependent transmission in W-type plastic optical fibers with graded index core distribution

This paper investigates the wavelength dependence of the equilibrium mode distribution (EMD) and steady state distribution (SSD) in W-type plastic optical fibers (POFs) with graded index (GI) core distribution for parametrically varied width of the fiber's intermediate optical layer and refractive index of the outer cladding. The numerical solution of the time-independent power flow equation is used to determine the transmission characteristics of the W-type GI POF. We demonstrated that the coupling length Lc required to achieve an EMD in W-type GI POF is shorter than the length determined experimentally for the original SC GI POF at 633 nm. We also demonstrated that as the wavelength increases, the EMD and steady-state distribution (SSD) are achieved at shorter W-type GI POF lengths. This is explained by the increase in leaky mode losses as wavelength increases. This makes it easier to tailor W-type GI POFs to a specific application at different wavelengths.

The Nonlinear Propagation and Interaction of Ultrashort Pulses in High-Speed Optical Fiber Transmission Systems in Optics

The fourth-order dispersive nonlinear Schrödinger (FODNLS) equation can simulate the nonlinear propagation and interaction of ultrashort pulses in high-speed optical fiber transmission systems in optics. In this paper, all traveling wave solutions of the envelope are obtained by means of the polynomial complete discriminant system and the elementary integral method. Under specific parameters, the propagation modes of all solutions are given. In this paper, by using the direct integration method, all traveling wave solutions of the envelope of the equation are given, including the singular rational solution, the singular periodic solution, the solitary wave solution and the double periodic solution.

Activation functions of artificial-neural-network-based nonlinear equalizers for optical nonlinearity compensation

We investigated the performance of artificial neural network (ANN)-based nonlinear equalizers for optical nonlinearity compensation by comparing activation functions, including a sigmoid function, ReLU, and Leaky ReLU. We compared the learning speeds and compensation performances by evaluating the resulting error vector magnitudes of the compensated signals. The performance was investigated using simulated 100-km optical fiber transmission of 10-GSymbol/s 16QAM signals. When the number of hidden-layer units in the ANN was small, the sigmoid function showed better performance in learning speed than ReLU and Leaky ReLU. This point is important because the number of ANN units has to be reduced in order to improve the computational complexity of the ANN-based nonlinear equalizer.

Ultra-high speed fiber-optic data transmission with a single chip source

Ultra-high speed fiber-optic data transmission with a single chip source

Design of real time system to measure the voltage signal in high voltage power supply

The output voltage signals should be measured in real-time, and it is sent to a control system for feedback control and protection in the high-voltage power supply with high-voltage, strong magnetic field, or strong power condition. In order to obtain a stable output voltage and a rapid response of the protection in the high-voltage power supply system, the measurement of the voltage signal needs to meet three requirements: response in real-time, accurate, and high isolation. Using the voltage-to-frequency (V/F) converter AD650 to transmit the analog signals as frequency form through the digital optical fiber is the best mode to measuring the signals with high precision, real-time, long-distance, and high isolation. The composition and principle of the real-time voltage measuring device are described in this paper. The design of the hardware and the parameters are analyzed and discussed in detail. The experimental results show that the circuit structure based on the AD650 chip is simple. The optical fiber transmission can achieve high isolation and high accuracy (better than 0.1%). The low response time (under 30us) can meet the requirements of the real-time voltage signal measurement system. The signal will not be affected by the high electromagnetic field in the transmission process. The measurement system has been applied in the high voltage power supply with excellent linearity and high isolation.

A high-dynamic-range digital RF-over-fiber link for MRI receive coils using delta-sigma modulation.

Coaxial cables commonly used to connect radio-frequency (RF) coil arrays with the control console of an MRI scanner are susceptible to electromagnetic coupling. As the number of RF channels increases, such coupling could result in severe heating and pose a safety concern. Non-conductive transmission solutions based on fiber-optic cables are considered to be one of the alternatives but are limited by the high dynamic range (>80 dB) of typical MRI signals. A new digital fiber-optic transmission system based on delta-sigma modulation (DSM) is developed to address this problem. A DSM-based optical link is prototyped using off-the-shelf components and bench-tested at different signal oversampling rates (OSRs). An end-to-end dynamic range (DR) of 81 dB, which is sufficient for typical MRI signals, is obtained over a bandwidth of 200 kHz, which corresponds to OSR = 50. A fully integrated custom fourth-order continuous-time DSM is designed in 180nm CMOS technology to enable transmission of full-bandwidth MRI signals (up to 1MHz) with an adequate DR. Initial electrical test results from this custom chip are also presented.

Study on Physical Effects of Optical Fiber Transmission Characteristics Under Nonlinear Optical Effects

Photonic crystal fiber has a special light guiding mechanism and structural tunability, which can produce singular dispersion characteristics and high nonlinearity, which provides new conditions for the research in the field of nonlinear fiber optics. Due to the combined action of a variety of nonlinear optical effects, photonic crystal fibres with different structural parameters and transmission characteristics can produce rich nonlinear spectra under different pump light pulse parameters. We use the photonic crystal fiber cladding section to conduct nonlinear optical experimental research, and obtain the broadband spectral output of soliton wave and dispersive wave. The theoretical analysis and experimentally measured spectra include blue-shifted dispersion waves in the visible light band near 0.5 μm, residual pump light in the 0.82 μm band, soliton waves in the 1.1 μm band, and red-shifted broadband dispersive waves near 2 μm. Corresponding to this, the formation and redshift of solitons can be clearly seen in the time domain, and there is no more oscillation secondary peak in the femtosecond transmission pulse.

The Physics Research of Optical Information Effect at Low Loss in Nonlinear Optical Fiber Transmission

Both nonlinear effects and dispersion are important factors that affect the transmission of optical pulses in optical fibres. In the anomalous dispersion region, the mutual balance of dispersion and nonlinear effects can achieve optical soliton transmission. Starting from the nonlinear Schrodinger equation of the optical pulse, under the condition of ignoring the dispersion, the nonlinear phase shift and frequency chirp of the Gaussian optical pulse under the nonlinear effect of self-phase modulation (SPM) are derived and simulated; the numerical simulation of the SPM the spectrum of Gaussian optical pulses with different maximum phase shifts without chirp and with positive chirp. The study found that the fusion loss of the fibre obtained by this algorithm is less than 0.11dB than that of the traditional single-mode fibre, and the additional bending loss caused by the wavelength range of 1460nm to 1625nm after winding 100 times on a 60mm cylinder is less than 0.02dB/km.

Performance Evaluation of Digital Back-Propagation in the Presence of Power Excursion

An accurate power map is mandatory to evaluate the performance of optical fiber transmissions in the nonlinear transmission region. In this letter, we discuss the performance variation in dispersion unmanaged fiber links due to power excursions, overarching the fiber nonlinearity that imposes a fundamental limit on the capacity of optical fiber transmissions. After using digital back-propagation (DBP) in optical fiber transmissions, the performance degradation due to power excursions shows different characteristics, depending on the location of the power excursion. Further, due to the cascading effect of the nonlinear signal-noise interaction (NSNI), the power excursion on the latter spans exerts a greater impact than that on the front spans. We implement a polarization-multiplexed 16-QAM over 12 spans of standard single-mode fiber (SSMF) experiment. The experimental results verify our theoretical analyses that the received SNRs after DBP can be sensitive to the power excursion and its location.

Nonlinearity compensation and link margin analysis of 112-Gbps circular-polarization division multiplexed fiber optic communication system using a digital coherent receiver over 800-km SSMF link

Nonlinear effects have been considered as the major limitations in coherent optical (CO) fiber transmission system. Digital signal processing (DSP)-based CO receiver with digital backpropagation (DBP) method has recently facilitated the compensation of fiber nonlinear impairments as well as compensating dispersion of optical fiber. In this paper, for the first time, a comprehensive design is presented for a newly introduced DSP-based CO receiver with the 8-quadrature amplitude modulation (8-QAM) circular-polarization division multiplexed (CPDM) fiber optic communication (FOC) system to investigate the impact of nonlinearities. We have examined the performance of nonlinearity compensating DSP-based CO receiver with DBP method and demonstrated that it can be effectively employed to mitigate the intrachannel nonlinearities in CPDM 8-QAM FOC system over 800-km SSMF link. Accordingly, by effectively compensating the fiber nonlinearities, we have analyzed the performance of bit error rate, optical signal-to-noise ratio (OSNR), optimum launch power, and investigate the link margin by evaluating OSNR margin for a specific launch power. Moreover, a CPDM technique helps as a very suitable means of maximizing the link capacity as well as enhancing the spectral efficiency of the FOC system.

Effects of the septic nonlinearity and the initial value of the radius of orbital angular momentum beams on data transmission in optical fibers using the cubic-quintic-septic complex Ginzburg-Landau equation in presence of higher-order dispersions

In a three-dimensional (3D) dissipative medium described by the higher-order (3+1)-dimensional cubic-quintic-septic complex Ginzburg-Landau [(3+1)D CQS-CGL] equation with the viscous (spectral-filtering) term, self steepening, Raman effect, dispersion terms up to six, diffraction and cubic-quintic-septic nonlinearities, we demonstrate that necklace ring beams with initial spherical shape carrying integer and even fractional angular momentum and whose intensities are azimuthally periodically modulated, can evolve into caterpillar, hexagonal, rectangular, scorpion, diamond and pillow dissipative optical bullets. The outcome of the evolution is controlled by the radius and the value of the septic nonlinearity in the initial necklace ring. We reveal numerically that spatiotemporal necklace-ring solitons carrying integer, and even fractional angular momentum can be self-trapped over a huge propagation distance even in the presence of random perturbations.