All-optical wavelength converters (AOWCs) based on parametric amplification in highly nonlinear fibers are investigated and evaluated, aiming at application flex-grid optical networks. A multichannel transmission system with a multilevel modulation format at 56-Gb / s bit rate is adopted. Parameters such as symbol error rate and signal bandwidth allocation are evaluated considering the optical signal-to-noise ratio, the power reception level, the channel spacing, and the impact of several cascade conversions—series of multiple AOWCs—on the signal quality. This work was carried out with an analytical modeling and computer simulations. Results reveal consistent modeling and adequate operation of the proposed AOWCs for flex-grid wavelength-division multiplexing networks and indicate that the number of conversions is limited by the size of the converter operating band and the allowed flex-grid slot size.
Gratings in optical fibers have been increasingly used in a variety of applications such as sensors and Telecomm. Depending on perturbation separation, they are classified as: fiber Bragg gratings (FBG), and long period gratings (LPG), whose each spectral output offer advantages for certain applications. Nowadays there is a great interest in the study of arrays formed by the combination of long period gratings and Bragg gratings in cascade (CLBG), where the propagation modes of the core and the cladding propagate in the Bragg grating after they propagate in the LPG. In this work, analysis and modeling of Cascaded Long Bragg Gratings using the Transfer Matrix method was performed for the case of two gratings in series along one fiber. We analyzed the variation of the FWHM of the reflectance and transmittance spectra for different values of the difference of the refractive indexes of the core and the perturbation of the grating, using the typical core refractive index of an SMF-28 as reference value. For smaller index difference a narrow intensity peak was observed. After the number of perturbations was varied, when there is a greater number of perturbations in the grating, there is greater intensity in reflectance. However, as our results show, this dependence is not a linear function. The results were obtained under the maximum-reflectivity condition (tuned) for each single grating. The development of the mathematical model, the results of the simulation and the analysis of results are part of the development of the present work.
The present work analyzes the performance of photonic switching networks, optical packet switching (OPS) and optical burst switching (OBS), in mesh topology of different sizes and configurations. The “lossless” photonic switching node is based on a semiconductor optical amplifier, demonstrated and validated with experimental results on optical power gain, noise figure, and spectral range. The network performance was evaluated through computer simulations based on parameters such as average number of hops, optical packet loss fraction, and optical transport delay (Am). The combination of these elements leads to a consistent account of performance, in terms of network traffic and packet delivery for OPS and OBS metropolitan networks. Results show that a combination of highly connected mesh topologies having an ingress e-buffer present high efficiency and throughput, with very low packet loss and low latency, ensuring fast data delivery to the final receiver.
In this work optical networks in mesh topology with OPS/OBS photonic switching are analysed and evaluated. Analytical and computer simulation methods are utilised for evaluation of average number of hops (ANH), packet loss fraction (PLF) and transmission delay (latency). These OPS/OBS networks show that under high input traffic, networks with nodes of higher interconnection grade are more efficient than just larger networks (increased number of nodes). For both optical packest and bursts results indicate high throughput, low ANH, low latency and very low packet loss fraction at the optical layer in our networks.
In this paper, the impact of the number of channels on the performance of elastic optical networks (EONs) is examined considering a multilevel modulation format and coherent transmission. Network design parameters such as spectral bandwidth and channel symbol error rate (SER), are analysed. We simulated the transmission of quadrature phase shift-keying (QPSK) signals, modulated at 56 and 100 Gbps, to evaluate a proposed flexible spectral allocation method in order to evaluate the effect of number of channels and the required total spectral bandwidth.
We evaluate through computer simulation the performance of Photonic switching OPS/OBS networks of various sizes and configurations, based on a lossless (amplified) photonic switching node experimentally demonstrated previously. The great advantage of photonic switching is transparency to signal rate and format. Thus we propose a basic flexible network, with low-energy consumption and high-efficiency. In simulations traffic load is varied and network parameters such as, average number of hops (ANH), network latency (delay) and packet loss fraction are evaluated. Consistent results for the various configurations are presented, analyzed and discussed; and Interesting conclusions emerge.
The main proposal of this work is to show the importance of using simulation tools to project optical networks. The simulation method supports the investigation of several system and network parameters, such as bit error rate, blocking probability as well as physical layer issues, such as attenuation, dispersion, and nonlinearities, as these are all important to evaluate and validate the operability of optical networks. The work was divided into two parts: firstly, physical layer preplanning was proposed for the distribution of amplifiers and compensating for the attenuation and dispersion effects in span transmission; in this part, we also analyzed the quality of the transmitted signal. In the second part, an analysis of the transport layer was completed, proposing wavelength distribution planning, according to the total utilization of each link. The main network parameters used to evaluate the transport and physical layer design were delay (latency), blocking probability, and bit error rate (BER). This work was carried out with commercially available simulation tools.
In this paper, the effects of gridless spectrum allocation in Wavelength Division Multiplexed (WDM) optical networks are examined. The advanced modulation formats and multi-rate transmissions of the signals, which are key parameters in the optical system project, are taken into account. The consumed spectrum, as well as the impact of linear and nonlinear impairments on the signal transmission, are compared to WDM network adopting standard grid and gridless ITU. To analyze the influence of these physical effects, some key network design parameters are monitored and evaluated, such as the guard band size, the signal occupied bandwidth, the laser power and the quality of channels. The applied signal modulation formats were On/Off Keying (OOK), Quadrature Phase Shift keying (QPSK), and Dual Polarization State Phase Modulation (DP-QPSK), whereas the transmission rate per wavelength was varied from 10 Gb/s to 100Ghz. The guard band, signal band, and laser power were swept and the resulted Bit Error Rate (BER) was estimated from the eye-diagram. Analytical calculations and simulations are conducted in order to evaluate the impact of the gridless spectrum allocation on both the spectral consumption and the signal quality of transmission (QoT). Results reveal that a gridless transmission system reduces the spectral consumption while offering an acceptable QoT. This work was carried out with both analytical modeling and numerical calculation using the Optisystem as well as Matlab.
In this paper, a multiband, multi-wavelength, all-fibre source array consisting of an 810nm pump laser diode, thretwo fiber splitters and three segments of Er-, Tm- and Nd-doped fiber is proposed for PON applications. In the set-up, cascaded pairs of standard fiber gratings are used for extracting the required multiple wavelengths within their corresponding bands. A thorough design parameter description, optical array details and full simulation results, such as: full multi-wavelength spectrum, peak and average powers for each generated wavelength, linewidth at FWHM for each generated signal, and individual and overall conversion efficiency, will be included in the manuscript.
The use of rare-earth-doped fiber section working in amplified spontaneous emission regime for different emission wavelengths is analyzed theoretically. From simulation results, the design of all-fiber superluminescent sources employing different rare earths as dopants for new optical windows and different applications is proposed. Results on different pump and signal powers in forward and backward propagation direction with respect to fiber length are presented.