Hesham A. Bakarman

Security performance of spectral amplitude coding OCDMA systems

This paper presents the security performance of spectral amplitude code OCDMA systems. We examine factors affecting data security such as system capacity and its influences on the eavesdropper SNR. The eavesdropper probability of error-free code detection for Modified Double Weight (MDW) OCDMA scheme is investigated. The eavesdropper performance is based on observing the authorized transmitted signal based on classical detection theory. For probability of correct detection of 0.5, an eavesdropper receiver would need to detect SNRs of 8, 9.3 and 10 dB for MDW (9, 4), MDW (18, 6) and MDW (30, 8) respectively.

Real-time monitoring in passive optical networks using a superluminescent LED with uniform and phase-shifted fiber Bragg gratings

This paper presents a monitoring system for tree-structured passive optical access networks. The emitted light of a superluminescent LED is utilized as the monitoring source. The light signal that propagates along the fiber to the customer site is then reflected by a uniform or phase-shifted fiber Bragg grating (FBG), which is employed near the end of the customer site. The wavelength optimization concept was demonstrated, where one center wavelength or Bragg wavelength is shared by two types of monitoring FBGs. Each FBG represents the distinct location of the optical network unit (ONU)to bemonitored. This technique improves the number of monitored ONUs twofold, since a single Bragg wavelength can be utilized to monitor two independent customers. The results were analyzed using a digital signal processing board that displays the reflection spectra of the FBGs. After identifying the faulty branch, an optical time domain reflectometer can be activated for fault localization. The system is capable of monitoring up to 128 customers while maintaining the bit error rate at 10-9. This real-time, centralized monitoring system demonstrates a low-power and cost efficient monitoring system with low bandwidth requirements.

Performance of 18 channel CWDM system with inline Semiconductor Optical Amplifier

Semiconductor Optical Amplifier (SOA) is used for a 2.5Gbps Coarse Wavelength Division Multiplexing (CWDM) transmission in O to L-band (1271-1611 nm). Analysis of the proposed topology is conducted using Optisystem software. In this paper, discussions on the gain spectrum and the quality of signal of an optically amplified 18 channel system are provided. A wideband travelling wave SOA which operates as an inline amplifier resulted in wide 3 dB bandwidth of 200 nm. The overall quality of signal at the receiver is evaluated with the Q factor value. Better performance based on Q factor analysis is obtained at larger lengths of the first fiber span and a flat gain over 11 CWDM channels is obtained.

Simulation of 1.25 Gb/s downstream transmission performance of GPON-FTTx

In this paper, 1.25 Gb/s GPON downstream link is presented. All the optical distribution network (ODN) classes are implemented, using Optisystem, to investigate the transmission capability and performance of the proposed downstream physical media (PM) GPON model. Some of the design constraints involved in an optical network design such as fiber span analysis, power budget and margin calculations are taken into consideration with worst case. The quality or performance of a digital communication system is specified by its BER or Q value with respect to other parameters such as receiver sensitivity. The simulated model can support 18, 50 and 128 number of users for classes A, B, and C respectively.

Security Performance of Spectral Amplitude Code OCDMA: Spectrally Encoded Pulse Bandwidth Effects

This paper presents security performance of spectral amplitude code OCDMA based on Modified Double Weight (MDW) OCDMA scheme. The eavesdropper probability of correctly detected Spectral Encoding Chip Bandwidth (SECB) pulses in a code word is investigated. For MDW code with code length and code weight of 9 and 4 respectively, SNR of approximately 8 dB is sufficient for an eavesdropper to detect the SECB pulses with a probability of 50%. The eavesdropper performance is based on tapping and observing the encoded transmitted signal using a tuning band pass filter followed by envelope detector. The eavesdropper measures the intensity for each intercepted pulse and calculates its corresponding sig- nal to noise ratio (SNR). Spectral Encoding Chip Bandwidth effect is investigated by simulation. The possibility of eavesdropping increases with wide SECB. Our results show that using unipolar OCDMA code schemes based on MDW code system enhances the security with a low cost implementation in comparison to the bipolar ones.

Flat gain, wide bandwidth of in-line semiconductor optical amplifier in CWDM Systems

Abstract Semiconductor optical amplifier (SOA) is one of the commonly used amplifiers in optical networks. This paper reviews the SOA implementation in coarse wavelength division multiplexing (CWDM) systems, which includes the explanation of the fundamental concepts such as the configuration, principle of operation as amplifiers, and the performance in different CWDM topologies. Simulation using OptiSystem software was carried out to determine the gain saturation at high input power and longer wavelengths. It shows that SOA implementation in CWDM networks is capable of providing flat gain for 40 nm wavelength span.

Hybrid SAC/Optical CDMA-WDM overlay system for enhancing network security

An enhancement of data networks security using a hybrid WDM and SAC/Optical CDMA System is proposed. Secure transmission for dedicated users is achieved by overlaying a covert channel onto a multichannel WDM network. The covert channel is spectrally encoded using spectral amplitude coding (SAC) with unipolar Modified Double Weight (MDW) as the signature address code. OCDMA improves service availability in the presence of physical infrastructure attacks. With the use of WDM channels, the difficulty for an eavesdropper to intercept and decode the secure signal is increased. A simulation is presented as a demonstration of the concept.

Implementing EDW in Point to multipoint optical access network for FTTH applications

this paper presents the implementation of enhanced double weight optical code division multiple access codes (EDW-OCDMA) on Point-to-multipoint access network for FTTH applications, the design is based on EDW code. Simulation experiment performed to study the performance of the code, the new algorithm to generate the higher weighted EDW code enable the performance study of EDW in Point-to-multipoint for higher weights too. In this paper there is a new design to implement the code into Point-to-multipoint Access network FTTH. Multiple weighted EDW code implemented and designed to fit into FTTH application. Performance of the code on FTTH is presented through eye diagram and comparison graph from the simulation results.

Gain performance of cascaded and hybrid semiconductor optical amplifier in CWDM system

The incorporation of cascaded and hybrid-type optical amplifiers into the optical fiber link is advantageous for the purpose of achieving wide gain bandwidth of multi-wavelength coarse wavelength division multiplexing (CWDM) systems. Different amplifiers whose operating gain region differ from each other are connected in cascade, thus providing better gain performance as the overall gain is combined and flattened over a larger spectrum. In this paper, the effect of the crossover of the uniform gain of the semiconductor optical amplifier (SOA) and the nonuniform gain of erbium-doped fiber amplifier (EDFA) is analyzed using an in-line cascaded SOA-SOA and an in-line hybrid SOA-EDFA configuration in the amplification of an 8-channels CWDM system obtained from the simulation using Optisystem software. It was observed that the cascaded SOA-SOA produces higher gain of 25 dB and wider gain bandwidth of 60 nm compared to the hybrid SOA-EDFA configuration with maximum gain of only 24 dB and 40 nm bandwidth. In addition, better bit-error-rate (BER) performance which is within the typical values in optical fiber communication is also achieved from the cascaded SOA topology. Wider gain bandwidth obtained with the SOA-SOA configuration would permit the transmission of video application at 1551 nm in the proposed Ethernet CWDM system transmitted at 100 Mb/s data rates.

Implementation of optical CDMA based on passive optical networks

In this article, our aim is to investigate passive optical networking (PON) based fiber access systems. An overview of optical OCDMA and optical coding through their features such as increasing the capacity, security and improving the system performance were presented. Modified prime code, which represents a user address and signs each transmitted data bit has been chosen as a signature sequence code because of its good periodic auto/cross correlation properties. However, simulation and theoretically analysis of balanced detection scheme based on passive networking access taking into account the effects of various noises such as shot noise, phase-induced intensity noise (PIIN), thermal noises were presented as well. Results of 25 subscribers sent in C band for the upstream signal with channel spacing 25GHz show good system performance in terms of the bit error rate and suppressing the multiple access interference when variation of fiber length and data rate are applied.