Volume 37, Issue 1 -

We have studied distributed Raman amplification (DRA) and hybrid Raman amplification to apply both 10G-EPON and TWDM-PON systems. Two types of access networks, 50 km and 10 km, are assumed for case studies. Using the calculated optical received signal power Ps and optical signal noise ratio (OSNR), we consider the cases where the hybrid Raman amplification is necessary or not. In the case of coexistence of both systems, co-use of lumped Raman amplification (LRA) located at a central office (CO) may be possible. The co-use of LRA for both systems is discussed using the calculated Ps and OSNR.

Due to the benefits of Raman amplifier (RA) for long-haul Ultra Wideband (UW)-WDM optical communications systems, we are studying and investigating how to widen the bandwidth and flatten the gain of RA by testing it in a new wider range of wavelengths (1.4 μm≤ λ signal ≤1.7 μm) instead of the benchmark range (1.45 μm≤ λ signal ≤1.65 μm). Four different ranges of signal wavelengths are used in this paper with the aim of testing the performance of RA model proposed in [13–15]: 1. 1.4 μm≤ λ signal ≤1.45 μm 2. 1.45 μm≤ λ signal ≤1.65 μm 3. 1.65 μm≤ λ signal ≤1.75 μm 4. 1.43 μm≤ λ signal ≤1.7 μm Different model sizes are used and analyzed to get wider bandwidth and more flat gain.

This paper presents a nonlinear analysis of the effect of linewidth enhancement factor (LEF) on the amplification of angle-modulated optical signals in injection-locked mid-infrared (IR) quantum cascade lasers (QCLs). A higher value of LEF tends to conserve the output angle modulation index of the amplified mid-IR signal particularly in the low-modulation frequency region. Further, a higher value of signal injection ratio produces a wider bandwidth of the locked QCL amplifier. The LEF introduces asymmetry in the lockband (LB) of the injection-locked QCL and this asymmetry increases with the increase in the value of LEF. Typically ratio of calculated lower-side LB to upper-side LB for an injection power level of – 20 dB and a LEF of unity is 1.67. The electron relaxation time in the uppermost subband lasing level in a three-level system has a profound effect on the LB asymmetry in a QCL.

The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. It is quite evident that people prefer optical communication when it comes to large amount of data involving its transmission. The concept of switching in networks has matured enormously with several researches, architecture to implement and methods starting with Optical circuit switching to Optical Burst Switching. Optical burst switching is regarded as viable solution for switching bursts over networks but has several security vulnerabilities. However, this work exploited the security issues associated with Optical Burst Switching with respect to integrity of burst. This proposed Quantum Key based Secure Hash Algorithm (QKBSHA-512) with enhanced compression function design provides better avalanche effect over the conventional integrity algorithms.

With the rapid development of fiber-wireless (FiWi) access network, the protection schemes have got more and more attention due to the risk of huge data loss when failures occur. However, there are few studies on the performance evaluation of the FiWi protection schemes by the unified evaluation criterion. In this paper, quality of recovery (QoR) method was adopted to evaluate the performance of three typical protection schemes (MPMC scheme, OBOF scheme and RPMF scheme) against the segment-level failure in FiWi access network. The QoR models of the three schemes were derived in terms of availability, quality of backup path, recovery time and redundancy. To compare the performance of the three protection schemes comprehensively, five different classes of network services such as emergency service, prioritized elastic service, conversational service, etc. were utilized by means of assigning different QoR weights. Simulation results showed that, for the most service cases, RPMF scheme was proved to be the best solution to enhance the survivability when planning the FiWi access network.

In this paper, a heuristic algorithm that considers ASE (Amplified Spontaneous Emission) noise impairment is developed for demand routing in long distance optical networks. Amplifier span constraints, determined by ASE noise impairment, are presented to constrain the maximal transparent reach of a lightpath. Problem formulation and heuristic algorithms are given. Simulation demonstrates that each demand stream is guaranteed to be successfully routed, and network resources (wavelength channels and transceivers) are effectively utilized.

In this research, the performance of optical code division multiple access (OCDMA) using differential phase shift keying (DPSK) has been compared with OCDMA On-Off Keying (OOK). This comparison took place in terms of bit error rate (BER) and receiver power where two bit rates (155 Mbps and 622 Mbps) have been used for this analysis. Using of OptiSystem 7.0 simulation, comparing eye diagram and optical spectrum alongside with BER and Rx power. It is found that OCDMA-DPSK performs better in comparison to OCDMA-OOK. The performance analysis also provides parameter for designing and development of an OCDMA system for optical access network using DPSK.

The core of the global telecommunication network consists of wavelength-division multiplexed (WDM) optical transmission systems. WDM is the technology of choice as it allows for a high spectral efficiency. We propose an effective way to counter the nonlinearities like four-wave mixing and cross-phase modulation to achieve the spectral efficiency of 1 bit/s/Hz using non-return-to-zero (NRZ) modulation format. We use the concept of non-uniform channel spacing and non-uniform power assignment between adjacent channels of the WDM system. We have simulated an eight-channel WDM lightwave system with bit rates of 10 and 25 Gbit/s.

In this paper, propagation behavior of Soliton pulse in optical fiber communication is analyzed. Ultra high speed transmission of data over optical fiber is possible by choosing appropriate pulse shape. Soliton pulse transmission using different modulation formats is performed to minimize jitter. Also analysis is done to calculate optical power, electrical power and average peak electrical power at different frequencies.

This paper has represented the operating conditions for radio-over-fiber (RoF) transmission system such as Q factor, received optical power and BER at different fiber lengths. This paper also investigated optical loss, optical power spectrum and electrical power spectrum at different frequencies for different modulation formats and optical loss at different radio frequencies for varying fiber length.

This paper deals with the design of multi-tone Radio over Fiber (RoF) system, which could efficiently support increasing demand of new services and increasing user traffic. It analyzed electrical power at different frequencies, SNR at input power P in at different bit rates. It also investigated BER at input power and at increasing number of channels.

A pseudo-linear optical transmission system analytical model is built for the numerical analysis of dispersion compensation schemes. The system performance under the influence of intra-channel nonlinear effects and the initial pulse power is discussed for the data rates of 10, 40, 100 and 160 Gbit/s, respectively. We get the conclusion for the first time as we know the optimal dispersion compensation scheme for the optimal system performance is closely related to the system data rate and the proportion of the pre-dispersion compensation should be decreased while that of the post-dispersion compensation be increased with the increasing of system data rate. When the system data rate is higher than 160 Gbit/s, we can use the post-dispersion compensation scheme directly.

In this paper, we aim to theoretically analyse optical code division multiple access (OCDMA) system that based on successive interference cancellation (SIC) using pulse position modulation (PPM), considering the interference between the users, imperfection cancellation occurred during the cancellation process and receiver noises. Spectral amplitude coding (SAC) scheme is used to suppress the overlapping between the users and reduce the receiver noises effect. The theoretical analysis of the multiple access interference (MAI)-limited performance of this approach indicates the influence of the size of M -ary PPM on OCDMA system. The OCDMA system performance improves with increasing M -ary PPM. Therefore, it was found that the SIC/SAC-OCDMA system using PPM technique along with modified prime (MPR) codes used as signature sequence code offers significant improvement over the one without cancellation and it can support up to 103 users at the benchmarking value of bit error rate (BER) = 10 –9 with prime number p = 11 while the system without cancellation scheme can support only up to 52 users.

This article introduces modulation technology, coherent reception technology, the overall design and other key issues for 100 Gbit/s dual-polarization quadrature phase shift keying (DP-QPSK) modulation. Using the technologies based on digital signal processing (DSP), it realizes the long-range transmissions of 100 Gbit/s optical systems to achieve optical signal dispersion compensation, polarized solution reuse and phase estimation. The effect of this scheme is verified with OptiSystem, and the simulation results indicate, with the help of DSP module for processing of the received signal, that the last constellation is ideal and the data transmission error rate is less than 1.3 e −4 . The scheme is implemented simply and has high reliability, and it also has reference significance for the optimization of coherent optical detection hardware. As they feature in high spectrum efficiency and large dispersion and PMD tolerances, the DP-QPSK modulation can improve the line efficiency, and maximize the spectral efficiency of the dense wavelength division multiplexing systems. The quality of eye diagram is high, which is clean and has decent open degree.