Moncef B. Tayahi

System performance optimization in SCM-WDM passive optical networks in the presence of XPM and GVD

The authors investigate semi-analytically the optimized system performance limitation in an SCM-WDM passive optical network (PON) in the presence of cross phase modulation (XPM) and group velocity dispersion (GVD). A general expression for electrical average crosstalk noise power due to XPM and GVD was derived to measure the system performance for increasing number of WDM channels. Using the expression, we show that XPM and GVD causes crosstalk in the system and imposes a power penalty as the WDM channels increases for a given channel spacing and modulating frequency. These results are extended to show that the system can be optimized to achieve a minimum BER of 10-9 by controlling the channel spacing and modulating frequency as the number of WDM channels increases.

Chromatic dispersion power penalties in orthogonal subcarrier--optical tandem single sideband systems

This paper deals with power penalties in Optical Tandem Single Sideband system using orthogonal subcarriers due to chromatic dispersion. The upper and lower sideband orthogonality is affected by chromatic dispersion. This phase imbalance causes degradation of quadrature demodulation performance. The effect is demonstrated by a mathematical model and verified by simulation results.

Optical performance monitoring using a poled lithium niobate (PP-LNO3)

Optical second harmonic generation in dense wavelength division multiplexing were used to monitor the performance of each channel in all optical networks. A poled Lithium-Niobate (PP-LNO3) device is used to convert C and L- Band optical WDM channels into half wavelength channels where silicon arrayed detectors and CMOS electronics were used to perform advanced digital signal processing to predict optical channel presence, channel power, signal to noise ratio and the quality (Q) factor parameter. With further processing, the bit error rate per channel can be estimated from the Q factor. The technique is realized on a system-on-a-chip CMOS technology which can potentially improve all optical networking architectures.

The effects of drive level errors on optical SSB system performance

This paper presents a system performance analysis of an optical single sideband system (OSSB) when drive level errors occur in the modulating signal driving the dual arm Mach-Zehnder modulator (MZM). The performance is evaluated in terms of the optical sideband suppression, frequency response and power penalty measurements. Experiments are carried out and a mathematical model of the OSSB system incorporating the drive level error is developed. The theoretical and experimental results suggest that the drive level error leads to reduced system performance as a result of poor received subcarrier power. The overall frequency response of the system, which is affected by drive level errors, accumulated CD and subcarrier frequency, has a direct influence over the power penalty. However, reduction in power penalty slope is observed at peaks of the OSSB frequency response.

4-ary PAM Signaling for increasing the Capacity of Metro Light-wave Systems

We investigated both experimentally and by simulation, non-return-to-zero (NRZ) and return-to-zero (RZ) 4-ary PAM operating at 20 Gb/s. A simple scheme to realize the quadratic signal leveling by suitably driving a MZ modulator is proposed, which provides greater than 6 dB improvement in receiver sensitivity as compared to equal level spacing. We experimentally demonstrated NRZ and RZ 10 Gbaud/s 4-ARY PAM transmissions over an 80 km standard single mode fiber (SSMF) link as a proof of concept and more detailed experimental results over longer reach will follow. Numerical simulations for the 4-ary PAM performance over longer distances (>200 km) are also presented.

Chromatic dispersion penalties in orthogonal subcarrier - optical tandem sideband systems (OTSSB)

This paper deals with dispersion penalties in an optical tandem single sideband system using orthogonal subcarriers. A mathematical model demonstrates the phase imbalance of the upper and lower sideband caused by chromatic dispersion and verified by simulations. The transmission over 10 km of single mode fiber (SMF) using different subcarrier frequencies shows higher penalties for higher subcarrier frequencies.

Effect of optical beat interference on channel spacing in DWDM optical systems

The information capacity of dense wavelength division multiplexing (DWDM) optical systems is reviewed. The effect of optical beat interference of closely spaced optical carriers sets the limit on the allowed channel spacing even in the absence of nonlinear effects. Present DWDM networks operating at 10.7 Gb/s in the C and L bands region have channel spacing no less than 25 GHz. We show that this limit is a constraint and smaller spacing may not be allowed without further optical and electrical pulse shaping.

Analysis of two dimensional multistage acousto-optic cell array system based on generalized equations for different parameters

Two dimensional multistage AOCA system based on generalized equations has been analyzed. Numerical results for Bragg angle as a function of acoustic frequency, deflection angles for different wavelengths, normalized power and diffraction efficiency with and without phase shift between consecutive arrays having different channel spacing based on generalized equations have been obtained.

Analsysis of soliton interaction with local defects in fiber Bragg grating

The interaction of a fiber Bragg grating point like soliton with local defects has been thoroughly analyzed. The stability of trapped solitons has also been discussed. The main finding reveals the reversal of the sign of interaction from attraction to repulsion. It is also observed that the attraction depends on the accuracy of the numerical simulations.

Analysis of a Tunable Asymmetrical Nonlinear Directional Coupler Using Laser Beam Interaction with Semiconductor Medium

A tunable asymmetrical nonlinear directional coupler (NLDC) having interaction of a laser beam with the semiconductor medium of the coupler has been thoroughly analyzed. The analysis is based on the coupled-mode theory for coupled lines. Laser beam is used for achieving optical control over the nonlinear directional coupler. The effects of various parameters such as plasma density, waveguide width, laser beam frequency and laser spot position on the coupling of power, on an asymmetric coupler have been investigated and presented.