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Bit error rate (BER) performance of return-to-zero and non-return-to-zero data signals optical code division multiple access (OCDMA) system based on AND detection scheme in fiber-to-the-home (FTTH) networks

Aldouri M. Y., Aljunid S. A., Ahmad R. B., Fadhil H. A.

Optica Applicata

2011

Vol. 41, nr 1

173--181

In this paper, we will focus on the modulation format used to create the optical pulses, which are return-to-zero (RZ), and non-return-to-zero (NRZ). Bit error rate (BER) performance is evaluated based on double weight (DW) code. Optical code division multiple access (OCDMA) system is considered a promising technique for fiber-to-the-home (FTTH) access networks. The performance of RZ against NRZ is compared through simulation by using the Optisystem software version 7. We used two networks designed as follows: one used a RZ pulse generator and the second used a NRZ pulse generator, and both systems were tested with and without erbium doped fiber amplifier (EDFA). It has been found that the NRZ pulse generator in this system is better than the RZ pulse generator for all simulation results. The conversion used a Mach-Zehnder interferometer (MZI) wavelength converter. Also, we are proposing a detection scheme known as the AND subtraction detection technique implemented with fiber Bragg grating (FBG) which acts as an encoder and decoder. This FBG is used to encode and decode the spectral amplitude coding DW code in the OCDMA system. The performances are characterized through BER and bit rate (BR), and also the received power at various bit rates.

Multi-rate transmissions on spectral amplitude coding optical code division multiple access system using random diagonal codes

Fadhil H. A., Aljunid S. A., Ahmad R. B.

Optica Applicata

2009

Vol. 39, nr 2

225-232

In this paper, we study the use of a new code called random diagonal (RD) code for spectral amplitude coding (SAC) optical code division multiple access (OCDMA) networks, using fiber Bragg-grating (FBG). FBG consists of a fiber segment whose index of reflection varies periodically along its length. RD code is constructed using a code level and data level, one of the important properties of this code is that the cross correlation at the data level is always zero, which means that phase intensity induced phase (PIIN) is reduced. We find the performance of the RD code to be better than those of the modified frequency hopping (MFH) and Hadamard codes. It has been observed from simulation and theoretical results that considering the bit error rate (BER), the RD code performs significantly better than other codes. The ability of RD codes to support simultaneous transmissions at different bit rates is shown through simulated results of the BER and the eye patterns. 10 Gbps and 2.5 Gbps data transmissions have been successfully demonstrated together with FBG decoding scheme for canceling the code level from SAC-signal.