Abstract
A two dimensional spectral/spatial cyclic shift (2D-CS) optical code division multiple access (OCDMA) systems is proposed for a potentially next generation passive optical network (NG-PON) implementation called (2D-CS NG-OCDMA-PON) system. The2D-CS proposed code is characterized by a high capacity and a zero cross correlation property leads to completely eliminating the multiple access interference (MAI) effect that is considered as the main OCDMA system drawback. Firstly, the 2D-CScode construction is investigated from 1D-CS code. Secondly, a system description is provided by exhibiting the transmitter and receiver architecture in the PON context. Analytical analysis reveals that our proposed 2D-CScode outperforms similar codes such as perfect difference (2D-PD) and dynamic cyclic shift (2D-DCS) codes in terms of spectral efficiency, simultaneous network subscribers and data bit rate. In addition, based on numerical analysis 2D-CS NG-OCDMA-PON system shows a good system performance by means of avery low BER and a high Q-factor values equal to $$10^{{ - 26}}$$ and 10.41 dB, respectively. Likewise, for four users and free-amplification the achievable reach ability distance of the NG-OCDMA-PON system is 63.21 km, 43.57 km and 33.2 km while Q-factor is equal to 6 dB at a bit rate of 622 Mb/s, 1 Gb/s and 1.5 Gb/s, respectively. On the other side, according to the system setup the number of single mode fiber (SMF) is reduced to the half compared to other 2D-OCDMA-PON systems based on enhanced multi diagonal (EMD) and single weight ZCC (SWZCC) codes.
Highlights
In the recent years, optical code division multiple access (OCDMA) technique has attracted much attention due to its ability to permit multiple users sharing the same bandwidth of the channel asynchronously and synchronously through providing each user its own code (Alayedi et al 2020a; Cherifi et al 2019; Alayedi et al 2019; Alayedi et al 2020b; Cherifi et al 2016; Cherifi et al 2018; Gupta and Goel 2017; Abd et al 2014; Nisar 2016)
This section discusses the system performance using two dimensional cyclic shift (2D-CS) code in two terms: bit error rate (BER)as function of number of simultaneous users, effective source power, data rate and spectral width, and signal to noise ratio (SNR) as function of number of simultaneous users. It indicates the effect of passage from one dimensional (1D) to 2D CS code and it is compared with 2D-perfect difference (2D-photo diode (PD))(Lin et al 2005)2D-multi service (2D-MS)(Najjar et al 2017), 2D-dycnamic cyclic shift (2D-DCS) (Jellali et al 2017)and 2D-zero cross correlation/multi diagonal (2D-ZCC/MD) (Matem et al 2019)codes for the same code lengths spectral and spatial: (L1 = 57) and (L2 = 3) respectively
OCDMA system based on 2D-CS code has been outperformed both 2D-PD, 2D-MS and 2D-ZCC/MD, and 2D-dynamic cyclic shift (2D-DCS) codes for the same code length about 2.31, 1.49 and 1.34 times respectively where the system capacity by using each code of them is 88, 136 and 151 users respectively so we can say that possibility meeting the needs of optical systems
Summary
Optical code division multiple access (OCDMA) technique has attracted much attention due to its ability to permit multiple users sharing the same bandwidth of the channel asynchronously and synchronously through providing each user its own code (Alayedi et al 2020a; Cherifi et al 2019; Alayedi et al 2019; Alayedi et al 2020b; Cherifi et al 2016; Cherifi et al 2018; Gupta and Goel 2017; Abd et al 2014; Nisar 2016). Incoherent systems depend on intensity modulation and direct detection (IM/DD) in encoding and decoding operations (Alayedi et al 2020a; Cherifi et al 2020; Cherifi et al 2019).Spectral amplitude coding-OCDMA (SAC-OCDMA) system suffers from multiple access interference (MAI) leading to a degradation of the system performance(Durand et al 2012; Mrabet et al 2009; Okassa M’foubat et al 2012) This issue can be eliminated if the codes will have constant in phase cross correlation value (Gupta and Goel 2017). There multiple approaches published recently for 2D-OCDMA systems use spectral and spatial as first and second encoding domain to tackle this shortcoming These codes suffer from high cross correlation (λc≥1) and autocorrelation values for instance 2D-perfect difference (PD) and 2D-dynamic cyclic shift (2D-DCS) and 2D-multi service (2D-MS) codes which are proposed by Lin et al [16], Najjar et al (Najjar et al 2017)and Jellali et al (Jellali et al 2017) respectively. A simulation setup is explained in sixth section and this paper is ended by a conclusion in the seventh section
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