Optimization of free space optics parameters: An optimum solution for bad weather conditions

Free Space Optics Systems (FSO) is one of the most effective solutions, especially for atmospheric turbulence due to the weather and environment structure. Free space optics system suffers from various limitations. A well-known disadvantage of FSO is its sensitivity on local weather conditions-primarily to haze and rain, resulting in substantial loss of optical signal power over the communication path. The main objective of this article is to evaluate the quality of data transmission using Wavelength Division Multiplexing (WDM) with highlighting several factors that will affect the quality of data transmission. The results of these analyses are to develop a system of quality-free space optics for a high data rate transmission. From the result analysis, FSO wavelength with 1550 nm produces less effect in atmospheric attenuation. Short link range between the transmitter and receiver can optimize the FSO system transmission parameters or components. Based on the analysis, it is recommended to develop an FSO system of 2.5 Gbps with 1550 nm wavelength and link range up to 150 km at the clear weather condition of bit-error-rate (BER) 10⁻⁹.     

Performance improvement for N × 80-Gb/s WDM transmission link with optimized alternate polarization

In this paper, it is shown that at a high bit rate of 80-Gb/s alternate polarization of adjacent bits in a Wavelength Division Multiplexed (WDM) transmission link improves the system performance in terms of improved Q factor and minimum bit error rate (BER). Alternate Polarization Return to Zero (al-PRZ) further suppresses the non-linear effects at higher power levels of 25 dBm per channel and also improves the transmission length to 640 km for a N × 80-Gb/s WDM system and hence results in an improvement of BER to 10⁻²⁰.     

基于3×3和2×2光纤耦合器的全光纤不等带宽梳状滤波器的设计

针对基于三个2×2单模光纤耦合器的全光纤级联Mach-Zehnder干涉仪型(CMZI)不等带宽光学梳状滤波器在实际制作过程中存在的问题,提出了由一个2×2和两个3×3单模光纤耦合器级联组成的全光纤不等带宽光学梳状滤波器,并进行了详细的分析.通过对光纤耦合器分光比、干涉仪臂长差等结构参量的选择,详细分析了其传输特性,并...     

Investigations on burst length in optical burst switched networks

In this paper, we investigate the performance of optical burst switched networks for erbium-doped fiber amplifiers (EDFAs) and semiconductor optical amplifiers (SOAs). We show that EDFAs are more suitable for burst switching as compared to SOAs. We further investigate the burst length for 18, 24.6 and 55 km optical switched network. It is observed that burst length should neither be very small nor very large. If the burst length is small, throughput will be less, and if the burst length is very large, delay will be very large. This is due to higher wait times incurred when packets are formed into larger bursts causing additional overall delay. It is observed that performance decreases up to a small burst length of 1500 μs, which is the minimum burst length required for the creation of the burst. Once this burst is created, there is significant improvement in the quality factor up to 3000 μs. After this burst length, the performance again degrades. Hence the burst length can be optimized for the best quality factor in optical burst switched networks. We further show that by increasing EDFA gain, the quality deteriorates as increasing the EDFA gain results in increased levels of additive phase noise, which can further induce nonlinearities.     

Soliton pulses generation and filtering using micro-ring resonators for DWDM-based soliton communication

We propose a new optical system that can be used to form the multi-soliton pulses within the micro-ring resonators. The system consists of two micro-ring resonators and an add/drop multiplexer that can be integrated into a single system. The large bandwidth signal is generated by using a soliton pulse propagating in a Kerr-type nonlinear medium. The tuned soliton pulses in either spatial or temporal modes are obtained by using the add/drop multiplexer. Results obtained have shown that the multi-soliton pulses can be localized coherently within the micro-ring waveguide. This is shown that the generation of the multi-soliton pulses within the micro-ring resonator is achieved, which is available for long-distance communication with dense wavelength division multiplexing (DWDM). The significant increase in channel number and spacing are obtained, whereas the large free spectrum range (FSR) of 600 pm is achieved.     

Design of Two 8-Channel Optical Demultiplexers Using 2D Photonic Crystal Homogeneous Ring Resonators

ABSTRACT

Ring resonators have always been referred to as a highly flexible structure for designing optical devices. In this paper, we have designed and evaluated two 8-channel optical demultiplexers using photonic crystal ring resonators. The purpose of this study is to investigate the flexibility of this type of resonator for designing and manufacturing optical devices based on photonic crystals. To the extent that we have investigated the literature, there is no report so far on such a study. For this purpose, two structures with the same structural parameters, but only with a difference in the type of lattice constant (square or triangular) are used. Both structures have a common photonic band gap within a proper range for telecommunication applications used in wavelength-division multiplexing (WDM) systems. Both designed structures have an average crosstalk of ?26 dB. For the demultiplexer structure with a square lattice constant, the quality factor and the transmission coefficient are 3,046 and 93.7% respectively, and its channel spacing is 1.97 nm. For the structure with a triangular lattice constant, the quality factor and the transmission coefficient are 1577.7 and 94.5%, respectively and its channel spacing is equal to 4 nm. To obtain the photonic band gap of the structures, the plane wave expansion (PWE) method is used and the output spectrum of the structures is obtained using the finite-difference time-domain (FDTD) method. The good results obtained in this study is through designing and simulating optical demultiplexer structures only by creating a change in the type of lattice constant used. This undoubtedly justifies the high flexibility of ring resonators, when used in the design of optical devices, as well as their suitability for the use in WDM systems     

How the Asymmetric Nature of IP Traffic Influences the Cost of the Underlying Optical Layer

In this article the influence of the asymmetric nature of (IP) traffic on the cost of the underlying optical transport network is investigated over a time frame of six years using a realistic traffic forecast for a European fiber-optic network. The currently deployed transport networks contain bidirectional optical line systems and are thus inherently symmetric, although the traffic that has to be conveyed over those networks is asymmetric. This article shows that a cost reduction of up to 38% can be obtained if the bidirectional line systems are replaced by unidirectional ones.     

A novel method degrading the combined effect of FWM and ASE noise in WDM systems containing in-line optical amplifiers

In this paper, a novel method degrading the combined effect of four-wave mixing (FWM) and amplified spontaneous emission (ASE) noise of the amplifier on the most heavily affected channel in an equally channel spaced wavelength division multiplexing (WDM) system containing in-line optical amplifiers is proposed. FWM effect is directly related to input powers of channels. So, FWM effect can be degraded by controlling channel input powers. In the proposed method, varying the input power of each channel in an optical fiber, the output optical signal to noise ratio (OSNR) values are evaluated and input powers of all channels are optimized in order to maximize the OSNR value of the channel having the lowest OSNR. To interpret the results obtained, output OSNR values for the minimum optical input power launched to the system by each channel are also computed. Being compared to the computed results for minimum optical input powers, the lowest output OSNR value among all channels for optimized input powers shows a 5.1867 dB increase in a 5-channel system, a 3.5988 dB increase in a 9-channel system, a 3.0855 dB increase in a 15-channel system and a 1.6795 dB increase for a 21-channel system. Furthermore, output OSNR values of all channels exhibit a significant increase.     

Experimental Measurement of Fused Fiber Coupler and M-Z Interferometer Performance as WDM Devices

Abstract

An experimental study of the WDM response of fused fiber couplers and an M-Z interferometer is presented. The WDM practical implementation limits of single fused fiber couplers, along with fiber tapering measurements, were obtained. Mach-Zehnder interferometric devices based on fused fiber couplers were included in this work in order to surpass the single coupler's WDM limitations and widen the operation range of the analyzed fused fiber devices.     

New version of seven wavelengths demultiplexer based on the microcavities in a two-dimensional photonic crystal

A new two dimensional photonic crystal demultiplexer of wavelength (WDM) is designed by exploiting two Fabry–Pérot reflectors at the end of the bus waveguides. The results show that the light with different wavelengths can be successfully filtered to different ports by setting different radius of the center defect rods in the drop waveguides and high drop efficiency can be achieved by means of reflection feedbacks. The proposed filter has a cross section equal to 9.7 μm × 5.8 μm. In the designed filter, an improvement of the number of channels has been achieved. The normalized transmission spectra of this component have been studied using finite difference time domain (FDTD) method. The important parameters consider for this studies are radius of rods used in Fabry–Pérot reflectors, and radius of center defect rods in the drop waveguides. The demultiplexer we designed can easily separate the light with seven different wavelengths simultaneously. The scope of this paper lies on demultiplexer for communication systems around 1.55-μm wavelength.