Fiber Nonlinear Effects Research Articles

Effects of fiber nonlinearity on error vector magnitude and bit error ratio for advanced modulation formats

Fiber nonlinear (NLI) noise, as well as amplified spontaneous emission (ASE) noise, degrades the performance of coherent optical fiber communications. We find that the temporal distribution of NLI noise, which is unlike that of ASE noise and depends on the waveform of signal pulse, has an impact on the estimation of error vector magnitude (EVM) and bit error ratio (BER). The influences of NLI noise, as well as ASE noise, on EVM and BER are analyzed for quadrature phase-shift keying and M-ary quadrature amplitude modulation systems. Modified theoretical formulas are proposed to estimate EVM and BER for the system under the effect of NLI noise, ASE noise, or mixing of these two noises. For system with mixing of ASE and NLI noises, according to our model, the optimal channel power for the best EVM is not corresponding to the best optical-signal-to-noise ratio. Our model is validated by numerical simulations.

THEORETICAL ANALYSIS OF SINGLE-FIBER TRANSMISSION OVER WDM-PON SYSTEMS

In this paper, a rigorous theoretical analysis on optical beat interferometric (OBI) noises caused by the Rayleigh backscattering (RB) and Fresnel reflection (FR) effects on the performance of a single-fiber single-wavelength WDM-PON (wavelength division multiplexing-passive optical network) transmission system has been presented. Two categories of PON are evaluated: a conventional and a long-reach WDM-PON system. The conventional WDM-PON took place in an access network for a typical transmission distance of 20 km without any optical amplification at the remote node (RN). In this case, the gain of the optimal reflective optical network unit (ONU) will depend on the relative RB power and also the FRs magnitudes and locations along the optical fiber channel/transmission link. However, in the cases of the long-reach WDM-PON deployed at a transmission distance of 100 km or further, the optical amplifiers are indispensable to enhance the optical power budget and to prevent the effect of fiber nonlinearities that may occur at high power injection levels. Although the presence of an optical amplifier (OA) in a long-reach WDM-PON will actually give some additional gain to the whole system, as a result it also produces the worse RB and FR effects to the system itself. A crosstalk to signal (C/S) ratio is used as a key performance indicator of whether the transmission system is in good working order or not. Therefore, this study may provide insight and relevant information in terms of transmission optimization for WDM-PON systems and developments in the future. To educate on the current technologies and developments surrounding conventional and long-reach WDM-PON, a brief overview is provided in the background part of the introduction.

Channel Capacity of Wavelength Division Multiplexing-Based Brillouin Optical Time Domain Sensors

We propose and demonstrate a novel WDM-based Brillouin optical time domain analysis (BOTDA) sensor using Brillouin loss configuration, and theoretically analyze channel capacity of WDM-based brillouin optical time domain reflectometry (BOTDR) and BOTDA sensors by considering the fiber dispersion and nonlinear effects in sensing fibers. A three-wavelength WDM-based BOTDA senor is experimentally validated in the distributed temperature measurement of a 23-km-long standard telecom fiber (SMF-28), demonstrating an electrical signal-to-noise ratio enhancement of 9.2 dB. The numerical calculation results of the channel capacity of WDM-based Brillouin optical time domain sensors show that, when compared with the conventional single-wavelength BOTDR and BOTDA sensors, 11-wavelength BOTDR and BOTDA sensor using large effective area fiber can respectively achieve 8.4 and 20.8 dB signal-noise-ratio improvement (SNRI), and 7-wavelength BOTDR and BOTDA sensor using SMF-28 can respectively achieve 7.2 B and 16.9 dB SNRI without evident spatial resolution degradation and nonlinear impairment.

Distributed Measurement of Fermi–Pasta–Ulam Recurrence in Optical Fibers

We experimentally demonstrate the distributed measurement of Fermi–Pasta–Ulam (FPU) recurrence in an optical fiber. Square-shaped pulses with weak modulation are injected into a single-mode fiber to exhibit FPU recurrence. Rayleigh backscattering signals of various sidebands are recorded to measure the power vibration along the optical fiber. The validity of the distributed method is confirmed both by the numerical simulation and the cutting-back method. Compared with the traditional cutting-back method, the distributed method has significant advantages, such as short measurement time, low cost, and good repeatability. We also believe that the distributed method has a great potential for the measurement of other nonlinear effects in optical fiber.

PENGGUNAAN NON ZERO DISPERSION SHIFTED FIBER PADA TRANSMISI KOMUNIKASI SERAT OPTIK KANAL 40 Gbit/s

Abstract Optical fiber transmission is generally used when the channel capacity (40 Gbit / s). Some of the key factors in achieving successful performance of this system include the implementation of Apol-DPSK modulation technique (Alternate Polarization Return-to-Zero Differential Phase Shift Keying), which accurately able to power up the canal, placement of optical amplifier (repeater) is recommended to increase the transmission range (the average gain for the entire wavelength range, low noise figure) and the use of optical fiber characteristics. To complement performance optical gain is selected fiber types NZDSF (Non-Zero Dispersion shifted fiber), it certainly can provide significant gains at the same time to reduce the widening pulse narrowing occurs due to chromatic dispersion and non-linear fiber effects. Keywords: Apol-RZDPSK, EDFA, RFA, DRA, NZDSF, PMD.

64-GHz millimeter-wave photonic generation with a feasible radio over fiber system

A full-duplex radio over fiber (RoF) link with the generation of a 64-GHz millimeter wave (mm-wave) is investigated. This system is proposed as a solution to cope with the demands of a multi-Gb/s data transmission in the fifth generation (5G) and beyond for small cell networks. Cost reduction and performance improvement are achieved by simplifying the mm-wave generation method with an RoF technique. High-frequency radio signals are considered challenging in the electrical generation domain; therefore, our photonic generation method is introduced and examined. RoF design is proposed for mm-wave generation using both phase modulation and the effect of stimulated Brillouin scattering in the optical fiber for the first time. RoF system with transmission rates of 5 Gb/s is successfully achieved. In our scheme, one laser source is utilized and a fiber Bragg grating is used for wavelength reuse for the uplink connection. Stable mm-wave RoF link is successfully achieved in up to a 100-km fiber link length with high quality carrier. Simulation results show a reduction in fiber nonlinearity effects and the mm-wave signal has low noise equal to −75 dBm. This study ensures a practical mm-wave RoF link, and it could be appropriate for small cell 5G networks by reducing the installation cost.

Laser linewidth and fiber nonlinearity tolerance study of C-16QAM compared to square 16QAM in coherent OFDM system

Abstract We introduced an effective modulation format circle 16 quadrature amplitude modulation (C-16QAM) to improve the laser linewidth induced phase noise and fiber nonlinear effects tolerance in coherent orthogonal frequency division multiplexing (OFDM) system without other losses compared to square 16QAM. Although C-16QAM has improved the performance of single channel system with Viterbi–Viterbi carrier phase estimation, C-16QAM using in coherent OFDM system has not been performed and such configuration of system may solve many problems in the next generation access networks. Here we numerically studied two separate manifestations of phase noise generated by laser linewidth and fiber nonlinear effects. We take these two kinds of phase noise into consideration separately by investigating the influence of laser linewidth with fixed launch power into transmission fiber and the influence of fiber nonlinear effects with fixed laser linewidth. We find that the C-16QAM improves the laser linewidth induced phase noise significantly and improves fiber nonlinear effects tolerance to a certain degree compared to square 16QAM. This coherent C-16QAM OFDM system may have great prospects for the next generation access networks for these significantly improvements.

A Survey on Fiber Nonlinearity Compensation for 400 Gb/s and Beyond Optical Communication Systems

Optical communication systems represent the backbone of modern communication networks. Since their deployment, different fiber technologies have been used to deal with optical fiber impairments such as dispersion-shifted fibers and dispersion-compensation fibers. In recent years, thanks to the introduction of coherent detection based systems, fiber impairments can be mitigated using digital signal processing (DSP) algorithms. Coherent systems are used in the current 100 Gbps wavelength-division multiplexing (WDM) standard technology. They allow the increase of spectral efficiency by using multi-level modulation formats, and are combined with DSP techniques to combat the linear fiber distortions. In addition to linear impairments, the next generation 400 Gbps/1 Tbps WDM systems are also more affected by the fiber nonlinearity due to the Kerr effect. At high input power, the fiber nonlinear effects become more important and their compensation is required to improve the transmission performance. Several approaches have been proposed to deal with the fiber nonlinearity. In this paper, after a brief description of the Kerr-induced nonlinear effects, a survey on the fiber nonlinearity compensation (NLC) techniques is provided. We focus on the well-known NLC techniques and discuss their performance, as well as their implementation and complexity. An extension of the inter-subcarrier nonlinear interference canceler approach is also proposed. A performance evaluation of the well-known NLC techniques and the proposed approach is provided in the context of Nyquist and super-Nyquist superchannel systems.

High Resolution Characterization of the Spectral Broadening Due to Fiber Nonlinearities

Balanced heterodyne detection and a gated microwave spectrum analyzer are used to precisely measure the spectral broadening due to intra-channel fiber nonlinearities. Polarization resolved spectra for a 224 Gb/s dual polarization 16-ary quadrature amplitude modulation signal are quantified in terms of the spectral edge power, which serves as a useful metric for capturing the effects of both fiber nonlinearities and amplified spontaneous emission noise. It is shown that without and with perturbation-based pre-compensation for the signal distortion due to the Kerr effect, the launch powers that minimize the bit error ratio and spectral edge power coincide.

광학적으로 제어된 섬유를 가진 비균일 불안정성의 과도 응답의 특성

In this paper we study the effect of chaos in nonuniform instability with optical fiber based IoT networks. The transient response of optically controlled fiber has also described. Nonlinear optical fiber effects especially fiber scattering in networks has emerged as the essential means active optical devices. The paradigm instability in fiber Internet serves as a test for fundamental study of chaos and its suppression and exploitation in practical application in optical communication. This paper attempts to present a survey and some of our research findings on the nature of chaotic effect on Internet based optical communication. The transient response in optical fiber has been evaluated theoretically by calculating the variation of the scattering function. The lines has used under open ended termination containing optically induced region. The scattered optical waves in a fiber used in optic communications are temporally unstable above certain threshold intensity.

Distributed Nonlinearity Compensation of Dual-Polarization Signals Using Optoelectronics

We propose an optoelectronic method for the distributed compensation of nonlinear fiber distortions affecting polarization multiplexed signals. This method involves placing devices we call total-intensity-directed phase modulators at the start of each amplified fiber span, in order to compensate the effect of fiber nonlinearity on a span-by-span basis. Numerical simulations are used to compare our proposed method with the well-known digital back propagation (DBP) algorithm for a wavelength division multiplexed system consisting of eight dual-polarization 16QAM channels operating at 28 GBd transmitted through a $15\times 100$ km dispersion unmanaged link. These simulations show that the proposed distributed nonlinearity compensation technique increases the peak signal quality, $Q$ , by 1 dB while DBP only increases peak $Q$ by 0.5 dB.

Modulation Format Identification in Coherent Receivers Using Deep Machine Learning

We propose a novel technique for modulation format identification (MFI) in digital coherent receivers by applying deep neural network (DNN) based pattern recognition on signals’ amplitude histograms obtained after constant modulus algorithm (CMA) equalization. Experimental results for three commonly-used modulation formats demonstrate MFI with an accuracy of 100% over a wide optical signal-to-noise ratio (OSNR) range. The effects of fiber nonlinearity on the performance of MFI technique are also investigated. The proposed technique is non-data-aided (NDA) and avoids any additional hardware on top of standard digital coherent receiver. Therefore, it is ideal for simple and cost-effective MFI in future heterogeneous optical networks.

Enabling the study of photons orbital angular momentum for optical communications

The internet data traffic capacity is reaching the limits imposed by optical fiber nonlinear effects, having almost exhausted the available degrees of freedom needed to orthogonally multiplex data. Therefore, new methods should be developed to avoid the capacity crunch. The orbital angular momentum (OAM) of photons may be used as an additional degree of freedom. In this article, in order to enable the study of applications of OAM for optical communications, an experimental setup for modulation and demodulation of free space OAM carrying beams was conceived based on twsited nematic spatial light modulator technology. This work assesses the viability of this technology pointing that this low cost solution can enable the application of OAM for optical communications.

Dispersion-Managed Optical Links Combined with Asymmetrical Optical Phase Conjugation for Compensating for Distorted WDM Signals

The combination of dispersion management (DM) and midway optical phase conjugation (OPC) is one of the promising techniques for compensating for optical signal distortion due to group velocity dispersion and nonlinear fiber effects. However, in this combination technique, midway OPC restricts the flexible optical link configuration. Therefore, the possibility of implementing the flexible optical link configuration with non-midway OPC applied to complete inline DM links is investigated in this study. It is confirmed that although the compensation using non-midway OPC for the distorted WDM channels is less effective than that using midway OPC, when non-midway OPC is placed at positions closer to the transmitters, the deployment of precompensation (i.e., the sequence of DCF + SMF)–OPC–postcompensation (i.e., the sequence of SMF + DCF) is more advantageous for the compensation. On the other hand, inverse deployment with respect to OPC (i.e., postcompensation–OPC–precompensation) is more advantageous when non-midway OPC is placed at positions closer to the receivers.

Comparison of the compensation effects of fiber nonlinear impairments with mid-span optical phase conjugation between PDM CO-OFDM system and PDM QPSK system**Project supported by the National Natural Science Foundation of China (Grant Nos. 61271192, 61427813, and 61331010) and the National Basic Research Program of China (Grant No. 2013AA013401).

The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing (PDM) coherent optical systems by mid-span optical phase conjugation (OPC) based on four wave mixing (FWM) effect are studied. Comparisons of the compensation results between PDM coherent optical-orthogonal frequency division multiplexing (CO-OFDM) system and the single carrier (SC) PDM quadrature phase shift keying (QPSK) system are provided as well. The results demonstrate that nonlinear compensation effect with mid-span OPC in PDM CO-OFDM system is much more obvious than that in SC PDM QPSK system.

Ultrahigh Soliton Pulse Compression Through Liquid Crystal Photonic Crystal Fiber

In this paper, one-stage nematic liquid crystal photonic crystal fiber (NLC-PCF) soliton pulse compressor is proposed and analyzed using full-vectorial finite-element method. The suggested design has high birefringence due to the infiltration of the NLC material. Therefore, it can be used as a soliton pulse compressor for the two polarized modes. The reported NLC-PCF compressor has high compression factor ( $F_{C}$ ) of 10.25 with high compression quality factor ( $Q_{C}$ ) of 0.84 at the operating wavelength of 1.55 μm for the quasi-TE mode with short device length of 76 cm. However, the $F_{C}$ and $Q_{C}$ of the quasi TM mode is equal to 10.93 and 0.66, respectively, at the same device length. The pulse compression through higher order solitons is allowed through controlling the fiber dispersion and nonlinear effects. In addition, greater compression can be achieved with large numbers of soliton order.

고출력 광섬유 레이저 기술의 현황 및 전망

Over the past two decades, fiber-based lasers have made remarkable progress, now having reached power levels exceeding kilowatts and drawing a huge amount of attention from academy and industry as a replacement technology for bulk lasers. In this paper we review the significant factors that have led to the progress of fiber lasers, such as gain-fiber regimes based on ytterbium-doped silica, optical pumping schemes through the combination of laser diodes and double-clad fiber geometries, and tandem schemes for minimizing quantum defects. Furthermore, we discuss various power-limitation issues that are expected to incur with respect to the ultimate power scaling of fiber lasers, such as efficiency degradation, thermal hazard, and system-instability growth in fiber lasers, and various relevant methods to alleviate the aforementioned issues. This discussion includes fiber nonlinear effects, fiber damage, and modal-instability issues, which become more significant as the power level is scaled up. In addition, we also review beam-combining techniques, which are currently receiving a lot of attention as an alternative solution to the power-scaling limitation of high-power fiber lasers. In particular, we focus more on the discussion of the schematics of a spectral beam-combining system and their individual requirements. Finally, we discuss prospects for the future development of fiber laser technologies, for them to leap forward from where they are now, and to continue to advance in terms of their power scalability.

Statistical Transform of Signal Field with ASE Noise through a Fiber Amplifier

While the signal field + ASE noise pass through a span of transmission fiber, a dispersion compensation grating and a fiber amplifier(with the generation of ASE noise), the nonlinear Fokker-Plank equations, describing the probability transforms of the field, are established and solved. Based on these statistical theories, the probability distributions of the signal + ASE noise field through 50km NZDSF, a dispersion compensation grating and a fiber amplifier link, are obtained. The dispersion and nonlinear effects in transmission fiber induce frequency offsets in the probability distribution of field and they cannot be dissipated by dispersion compensation. The generation of ASE noise in the amplifier will accelerate this frequency offset.

Review of Recent Progress in Digital Coherent Optical Communications

Abstracts: This paper reviews the recent progress in digital coherent optical communication technologies for core metro, and access transport network. Digital mitigations of various transmission impairment induced by Kerr -nonlinear effects in optical fibers are addressed.

Mitigation of Fiber Nonlinearity Effects in Ultra High-Dense WDM System by Using Fractional Fourier Transform for 32 Channel System

The optical signal is severely degraded when transmitted in the fiber due to both the linear and nonlinear distortions. It is well known that, the linear distortions in single mode fiber include chromatic dispersion (CD) and polarization-mode dispersion (PMD) while self-phase modulation (SPM), cross phase modulation (XPM) and four-wave mixing (FWM) are considered the most among nonlinear distortions. A method called Fractional Fourier Transform (FRFT) has been applied to mitigate fiber nonlinearity impairments. In this work, 10 Gb/s optical fiber system with five spans, each of length 60 km, for three types of modulation formats (Return-to-Zero Differential Phase Shift Keying (RZ-DPSK), Return-to-Zero Differential Quaternary Phase Shift Keying (RZ-DQPSK) and Carrier-Suppressed Return-to-Zero (CSRZ)), single and multi-channel transmission systems are designed and simulated using “OptiSystem (2011) version 10.0” software package. The BER of thirty two channel systems (channel No.16) at bit rate 10 Gb/s per channel, 300 km link length of CSRZ modulation format with channel spacing of 50 GHz at SNR 10 dB without FRFT is 10-4.6 and 10-6.4 with FRFT. The BER of thirty two channel system (channel No.16) at bit rate 10 Gb/s per channel, 300 km link length of CSRZ modulation format with channel spacing of 25 GHz at SNR 10 dB without FRFT is 10- 2.56 and 10-3.24 with FRFT.