Long-distance optical transmission: Comparison between NRZ and solitons

Nonreturn-to-zero (NRZ) and return-to-zero (RZ) signal formats are experimentally and numerically compared for single-channel long-distance transmission in an in-line amplifier system with dispersion management providing average zero dispersion and local nonzero dispersion at an interval equal to the in-line amplifier spacing. Among a 20-ps RZ signal, a 40-ps RZ signal, and an NRZ signal transmitted in 10 Gb/s straight-line experiments, the last signal achieves the longest transmission distance of 6000 km while the others are limited to 4400 km. Numerical simulations explain these results well and show that, along with linear amplified spontaneous emission (ASE) accumulation, signal waveform distortion due to the combined effect of higher order group-velocity dispersion (GVD) and self-phase modulation (SPM) dominates the performance. Nonlinear optical noise enhancement is not obvious because of the fiber dispersion arrangement. Signals with large pulse widths are less affected by the combined effect, while small-width signals yield superior initial signal-to-noise ratio (SNR) as determined by optical noise. A detailed simulation indicates that a pulse width of about 60 ps is optimum for long distance transmission under the fiber dispersion arranged in this paper.

The positioning of Erbium-Doped Fiber Amplifiers (EDFAs) plays a crucial role in optimizing the performance of Dense Wavelength Division Multiplexing (DWDM) systems, particularly in addressing signal attenuation challenges in long-distance optical transmission. This study investigates the impact of EDFA placement configurations (booster, in-line, and pre-amplifier) on signal quality using OptiSystem software simulations. The research examines systems with 4 to 16 DWDM channels, operating at 10 Gbit/s per channel with 50 GHz spacing, varying total input power between -10 dBm to 5 dBm. Results demonstrate that the booster amplifier configuration performs best, while the pre-amplifier setup exhibits more pronounced degradation. The in-line amplifier configuration shows a balanced performance, effectively restoring signal strength while requiring less pump power than the booster configuration, making it a viable option for optimizing energy efficiency in DWDM systems. A critical performance threshold was identified between 10-12 channels, where all configurations experience significant changes in error performance.

Wireless charging systems are critical for safely and efficiently recharging mobile electronic devices. Current wireless charging technologies involving inductive coupling, magnetic resonance coupling, and microwave transmission are bulky, require complicated systems, expose users to harmful radiation, and have very short energy transmission distances. Herein, we report on a long-distance optical power transmission system by optimizing the external cavity structure of semiconductor lasers for laser charging applications. An ultra-long stable oscillating laser cavity with a transmission distance of 10 m is designed. The optimal laser cavity design is determined by simulating the structural parameters for stable operation, and an improved laser cavity that produces an output of 2.589 W at a transmission distance of 150 cm is fabricated. The peak power attenuation when the transmission distance increases from 50 to 150 cm is only approximately 6.4%, which proves that this wireless power transfer scheme based on a vertical external cavity surface-emitting laser can be used to realize ultra-long-distance power transmission. The proposed wireless energy transmission scheme based on a VECSEL laser is the first of its kind to report a 1.5 m transmission distance output power that exceeds 2.5 W. Compared with other wireless energy transmission technologies, this simple, compact, and safe long-distance wireless laser energy transmission system is more suitable for indoor charging applications.

DOI: 10.1049/ic:20070242 ISBN: 978-3-8007-3042-1 Location: Berlin, Germany Conference date: 16-20 Sept. 2007 Format: PDF For the first time, we have demonstrated error-free operation of slow-light via SBS in optical fiber for 10-Gb/s NRZ and PSBT formats. The PSBT signal sensivity is 5.2 dB better than the NRZ case for a 35-ps delay. (2 pages) Inspec keywords: delays; optical modulation; stimulated Brillouin scattering; optical fibre communication Subjects: Modulation and coding methods; Stimulated Raman scattering and spectra; CARS; stimulated Brillouin and stimulated Rayleigh scattering and spectra; Optical communication; Optical communication devices, equipment and systems; Nonlinear optics and devices

One of the most important technical advances in fiber optic telecommunication systems has been the optical fiber amplifier (OFA). The use of an all-optical fiber optic amplifier instead of a semiconductor optical amplifier has many inherent advantages. For example, the most popular erbium-doped fiber amplifiers (EDFAs) have a broad range of optical amplification in the 1550-nm window; these erbiumdoped fibers are easy to incorporate directly into an all—fiber optic telecommunication system. Today the erbium-doped silica fibers are the most common rare-earth (RE)-doped fiber amplifiers, as they have high gain and low noise. EDFAs are quite versatile in that they may be used as preamplifiers, in-line and booster amplifiers, as well as sources. They can provide more than 20 dB of gain across a broad wavelength band, which enables them to be extremely useful as components in dense wavelength-division multiplexed (DWDM) systems. Additionally, they may be pumped with 800-, 980-, and 1480-nm sources and their quantum efficiency can be quite high.

The authors propose a novel technique for constructing large passive star couplers with gain using high-power erbium-doped fiber (EDF) amplifiers. In contrast to other proposed techniques where each output port of the coupler requires its own EDF amplifier, the proposed alternative requires few EDF amplifiers with sufficient output saturation power levels. When used in an FDM/WDM star network, the size of the coupler can be increased by a factor of m using m narrowband EDF amplifiers. Moreover, this alternative avoids coupling the pump-laser light through the star coupler itself, alleviating the requirement on designing large bandwidth couplers to accommodate the signal and the pump wavelengths.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Objectives: This study aims to enhance and optimize a modern communication system for high data rate transmission using Dense Wavelength Division Multiplexing (DWDM). The objectives include employing a 64-channel DWDM system, implementing different data speeds, and utilizing a dispersion compensation method. Methods: To achieve the objectives, we simulate and analyze the effects of Dispersion Compensation Fiber (DCF) in a DWDM system with 64 channels. The system employs Non-Return-to-Zero (NRZ) modulation format at varied bit rates and multiple energy levels. We propose a method for achieving data rates of 10 to 40 Gbps using NRZ modulation and Erbium-Doped Fiber Amplifier (EDFA) over a single-mode fiber transmission distance of 40 to 160 km, along with a dispersion compensation fiber of 8 to 32 km (DCF). The performance of the developed model is evaluated based on Quality Factor, Bit Error Rate (BER), Eye Height, and Threshold. These metrics are measured at two input energy levels from an optical power source, covering a communication capacity ranging from 0.625 Tbps to 2.5 Tbps. Findings: Through the simulations and analyses, we uncover the impact of dispersion and demonstrate the effectiveness of the proposed method in compensating for dispersion effects. Performance analysis of two different input transmitter power levels, -10 dBm is more efficient compared to 0 dBm input transmitter power in terms of bit error rate and quality factor. Novelty: This study presents a novel approach to improving modern communication systems by utilizing DWDM with a dispersion compensation method. The use of a 64-channel DWDM system, combined with the proposed NRZ modulation technique and dispersion compensation fiber, provides an efficient solution for achieving high data rates over long transmission distances while minimizing the effects of dispersion. The findings contribute to the advancement of communication systems for high data rate transmission. Keywords Dispersion effect, Bit Error Rate, Q-factor, Optisystem software, Erbium doped fiber amplifier

We have designed and experimentally characterized an erbium doped fiber amplifier (EDFA) which possesses a wavelength-independent gain spectrum, independent of the operating level of the gain (dynamic gain flatness), and without requiring any gain-level-dependent control of any parameters. In the wavelength range 1542-1552 nm, the gain was flat to within the experimental uncertainties of /spl plusmn/0.3 dB even as the gain level changed by 17 dB. The EDFA was based on a low-Al-content alumino-germanosilicate EDF and a Mach-Zehnder filter. We believe that this type of EDFA, which has not been demonstrated before, can significantly simplify the design of amplified wavelength-division multiplexing (WDM) transmission systems and increase the robustness of long-distance WDM transmission.

The present paper proposes the optimal transmission parameters for non-return-to-zero (NRZ), return-to-zero differential phase shift keying (RZ-DPSK), carrier-suppressed RZ-DPSK (CSRZ-DPSK) and duobinary (DB) modulation formats in 16-channel 10 Gbit/s wavelength division multiplexed passive optical network (WDM-PON) transmission system. The paper investigates influence of laser output power, length of dispersion compensating fiber (DCF) and application of erbium-doped fiber amplifiers (EDFA), as well as impact of optical components configuration on received signal quality. It compares demand of these modulation formats for amplification and dispersion compensation with the increase of transmission distance, determining the optimal conditions for achieving maximal network reach for each of them. It is shown, that DB is the most resistant to chromatic dispersion (CD) and is able to achieve the longest transmission distance (100 km) without dispersion compensation. Whereas RZ-DPSK and CSRZ-DPSK modulation formats demonstrated maximal achievable reach (180 km) using DCF and EDFA.

Erbium-doped fiber amplifiers (EDFAs) have recently been extensively studied for applications in long-distance transmission[1] [2] and subscriber loop distribution systems[3][4][5]. The noise figure of the fiber amplifier is a parameter that must be considered in these systems to optimize overall system performance. Noise figures of an EDFA pumped at 1480 nm and 980 nm were reported to be near 5 dB[6], and 3 dB[7], respectively. However, these numbers were measured when the amplifiers were operated in the linear region. An EDFA may be operated in the gain saturation region when it is used as a power amplifier in the subscriber loop[3] [5], or when it is one of the latter stages of many cascaded amplifiers in a transmission system. In the latter case, the amplifier gain saturates because of the accumulated amplified spontaneous emission (ASE) noise, which may be due to the finite passband of interstage optical filters, or because there is not enough inter-stage loss to compensate the amplifier gain. Under the above conditions, questions arise as to whether the amplifier noise figure increases while the gain is saturated, and what are the parameters that control this noise figure degradation. The subject of this paper is to examine these questions.

Erbium-doped fiber amplifier (EDFA) featuring a spectrally flattened gain is considered to be one of the most important key devices for the wavelength-division multiplexing (WDM) transmission systems. For this purpose, we have developed hybrid EDFs composed of Al doped EDF and P/Al co-doped EDF and examined their characteristics comparing with the conventional EDFs and those with passive gain equalizers. As a result, hybrid EDFs have been shown to exhibit both a flat gain and high pumping efficiency, but their noise characteristics tends to be worse than conventional EDF configurations. Thus a midway isolator should be inserted. As a result of the design optimization, three-section hybrid EDF configuration has been proposed, and three types of EDFAs have been developed employing this configuration for use as in-line amplifiers or preamplifiers. All types exhibit the passband spanning about 15nm.

Low noise double pass L-band erbium-doped fiber amplifier

Optical time domain reflectometry (OTDR) in an optical transmission line containing in-line Er-doped fiber amplifiers is investigated. The proposed Er-doped fiber amplifiers are based on optical circulators, which support both OTDR and digital signal transmission. The measurable limit of OTDR fault location in optical transmission lines containing in-line amplifiers is discussed. Fault location and 1.8-Gb/s digital signal transmission are demonstrated in a 316.9 km, optical transmission line constructed with three in-line Er-doped fiber amplifiers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical fiber communication has characteristics that really need attention. The characteristics of fiber optic transmission are very important in designing optical fiber networks, one of which is widening pulses called dispersions. Dispersion is the widening of light pulses in optical fibers which reduces data speed, signal to noise ratio and system quality. In addition to dispersion compensation, which is the most important feature needed in fiber-optic communication systems; transmission power needs to be considered to produce optimal signal output. In this paper, we will simulate the optimization effect of power and fiber dispersion compensation on Non Return to Zero (NRZ) and Return to Zero (RZ) modulation on optical transmission systems, with 5 dBm power parameters, 10 dBm 15 dBm and 0 dBm and DCF 5 km, 10 km, 15 km, 20 km and 25 km. Simulation results show that dispersion compensation is very influential on the transmission system. From these two modulations, there are differences in the results between NRZ and RZ. The results of dispersion compensation also affect the input power and DCF length.

Chromatic Dispersion Compensation (CDC) using Fiber Bragg Grating (FBG) techniques in Dense Wavelength Division Multiplexing (DWDM) system is presented in this article. Pulse broadening effects on the transmitted signal can be limited by Dispersion Compensation (DC) mechanisms. To overcome this problem and improve the system performance, a suggested system for 10 Gbps using Chirped Fiber Bragg Grating (CFBG) as a dispersion compensator, Non-Return-to-Zero (NRZ) modulation format and an Erbium Doped fiber Amplifier (EDFA) on a Single Mode Fiber (SMF) is designed. The result shows that, with using CFBG grating length of 90 mm, SMF length of 30 Km, input power of 15 dBm and attenuation coefficient 0.1 dB/Km, the Quality-Factor (QF) is 39.9373 dB. However, increasing SMF length to 100 Km, the QF is 12.173 dB. Thus, Results show that this model is more efficient in terms of QF, Bit Error Rate (BER) and eye diagrams related to other published papers which can be useful in many applications in telecommunication system like Sensor Networks, Remote Radar Networks, Tele-spectroscopic process control network, and many more networks.