Volume 36, Issue 3 -

The system performance of single channel OFDM at 10-Gbps data rate using phase modulation under the effect of Raman amplifier and varying cyclic prefix of OFDM signal is evaluated. Pump power of single pumping type co-propagating Raman amplifier is varied and the results are analyzed for different fiber length through simulation. Raman gain variation is observed with increasing Raman pump power and it shows that increasing the pump power will improve the system performance. Also it reveals the fact that with an application of Raman amplifier the transmission distance will increase. Further received electrical power is observed with variation in cyclic prefix. Electrical output power is detected in each case. Moreover optical spectrums are examined with and without amplifier.

In this paper, an all-optical switch based on photonic crystal directional coupler has been simulated and analyzed by the finite difference time domain (FDTD) method. An ultra small 3-channel wavelength division demultiplexer based on 2D photonic crystal was modified into all-optical switch suitable for integration. The output wavelengths of designed structure can be tuned for communication applications (around 1.5 µm, 1.4 µm, 1.3 µm) by locating suitable defect parameters in the corner of each resonance cavity and input waveguides. The bandwidth of each channel is about 1 nm.

We have developed a theoretical model that analytically predicts the nonlinear phase shift, which is due to Stimulated Brillouin Scattering (SBS) in two different types of optical fibers, a Standard Single-mode fiber (SMF) and a conventional Dispersion Compensating (DCF) fibre. Theoretical analysis based on the SBS effect yields a good description of the nonlinear phase shift of the output pump and Stokes wave characteristics in a strong saturation regime. A comparison of the two optical fibers is presented. With input pump power of 16 dBm, optical fiber length 11 km at the power ratio of 0.05, the predicted nonlinear phase shift of the output pump power and the Stokes power of SMF and DCF are about 79.58° and 97.92°, respectively. The nonlinear phase shift of the output pump power and of the Stokes power is higher when 11 km (6.7 km) DCF fiber length is used, as compared to the SMF of the same length. The nonlinear phase shift to the output pump power (the Stokes power) of DCF was less (more) than 8% (5%) for SMF at maximum input pump power.

The network resource utilization efficiency is limited by the rigid nature of the current wavelength-routed optical networks. The recently proposed flexible optical network can allocate the spectral resources adaptively according to the traffic demand. Meanwhile, the transmission quality has always been a main objective during the routing process in optical networks. Recently, the energy efficiency has also been a hot topic because of the energy consumption problem. In this paper, we propose a novel weighted energy efficient routing and spectrum assignment scheme based on the designed quality of transmission (QoT)-energy estimation model in which the physical impairments and energy consumption are given consideration to two or more things. The simulation results demonstrate that the proposed algorithm can make a better balance between the quality of service (QoS) and energy efficiency.

In this paper, we analyze polarization-multiplexed quadrature phase shift keying (PM-QPSK) signals using different receiver with and without differential decoding for PM-QPSK modulation and reception using training sequence-based least mean square (LMS) receiver, PM-QPSK with external local oscillator, PM-QPSK modulation and LMS dynamic receiver and compare their results for bit error rate.

We have proposed and demonstrated a full-duplex wavelength division multiplexed passive optical network (WDM-PON) configuration based on reflective semiconductor optical amplifier (RSOA). RSOA is used for reusing and remodulate the downlink signal in the uplink. We have used external modulation scheme for transmitting 20 Gbps data rates in two channels over a 40 km single mode fiber (SMF). The uplink and the downlink performances are checked by the bit error rate (BER) and the eye diagrams.

It’s known that different physical impairments can occur in coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Not only linear impairments but also nonlinear impairments can cause significant signal degradations. It is important to analyze the physical layer impairment (PLI) model which should consider these impairments. In this paper, a new PLI model is developed, where amplified spontaneous emission (ASE) categorized to linear impairments and four-wave mixing (FWM) categorized to nonlinear impairments are regarded as the main noise sources. The performance of developed PLI model in terms of Q factor versus number of subcarriers and Q factor versus fiber length are extensively simulated. Numerical results show that when the OFDM signal passes through fiber link, the noise power expansion occurs. This expansion which is related to the fiber length, number of subcarriers as well as input power, can cause higher degradation in OFDM signal. Through precise analysis, optimum parameters of the transmission system can be chosen. Simulations prove that Q factor of CO-OFDM, whose number of subcarriers is 128, fiber length is 90 km and input power is −2 dBm, is up to abound 10 dB. In addition, in order to verify the developed PLI model, comparisons of the situation with and without considering FWM effects have also been made respectively. Results show that the performance of the model conforms to the actual conditions.

In this paper, we investigate the effect of channel spacing and chromatic dispersion on four wave mixing in WDM system. Dominating effect of four wave mixing is minimizing at maximum value of dispersion and channel spacing. Power of FWM, Q-factor, bit error rate and output spectrum is used to measure the performance of system.

This paper compares the effects of amplified spontaneous emission and Q -factor for advanced modulation formats of carrier-suppressed return-to-zero (RZ), duo-binary and differential phase-shift keying (DPSK) for single and multichannel. In case of single-channel transmission, only one channel is analyzed, and for multichannel transmission, eight channels are analyzed. Main focus is to study system impairments caused due to linear and nonlinear effects. We have simulated single-channel 40 Gbit/s system and eight-channel 40 Gbit/s dense wavelength division multiplexing (DWDM) system for total five spans with each span is equal to 50 km, with a channel spacing of 100 GHz (in case of eight-channel system) for all three formats. In case of DPSK, we have considered RZ-DPSK with 33% and 66% duty cycle and comparison is made between them in terms of Q -factor. We have reported the best format for single channel as well as for multichannel among three formats and we have also listed the channels that are worst affected by nonlinearities and have least Q -factor.

In this paper, the transmission of signal with DPSK modulation with variation of duty ratio to 66% and 33% is demonstrated and performance of the system is analysed by varying the gain and noise figure value of an EDFA amplifier.

A bidirectional subcarrier multiplexing (SCM)-radio-over-fiber(RoF) network is proposed. In this paper, SCM RoFlink is analyzed with and without optical amplifier. The response of the system is studied for semiconductor optical amplifier (SOA), erbium-doped fiber amplifier (EDFA) and Raman amplifier. The results for the same are compared and then the appropriate amplifier is selected and the required gain for the optimal performance of the system is reported.

In this paper, a new generation of Network-on-chip (NoC) system with CDMA code is proposed. A Bipolar CDMA code is used to provide a good system performance and to reduce MAI. Two structures of a detector are employed, which are the PIN and the APD detectors, while putting into consideration thermal noise. On one hand, we are proving, in this work, that system performance can achieve a good BER value in optical context with an acceptable node number. On the other hand, system bandwidth can reach 16 Gbit/s with an acceptable SNR compared to wired architecture.

Advanced modulation schemes, particularly the phase-modulated signals, have already drawn huge research interests for ultra-high speed long-haul lightwave transmission systems. We have considered 40 Gbit/s optical RZ pulse propagating in a periodically dispersion managed (DM) single channel system with negative residual dispersion. We investigate the effects of negative residual dispersion on intra-channel cross-phase modulation (IXPM)-induced phase shift. Analytical estimation for phase shift has been deduced using perturbed variational formulation. We therefore explore the impact of variation of various parameters such as transmission distance, duty cycle, bit rate, etc. on phase shift. The outcome of our work is to explore the performance of the dispersion compensated system with some negative residual dispersion so that the IXPM-induced phase shift remains low in optical fiber communication.

In this paper, the decay of higher order soliton in the presence of third order dispersion, intrapulse Raman scattering and self-steepening scattering has been examined in optical fiber soliton communication. The result has been analysed in the form of graphic representation for optical time domain visualizer and optical spectrum analyzer.