## 2 Literature Review
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Codes** & \multicolumn{2}{c}{**Benefits**} & \multicolumn{2}{c}{**Drawbacks**} \\ \hline
**2D-DEU** & - & High Data Rate & - & High PINN Noise \\  & - & Short Code Length Compared To 1D & - & Presence MAI \\  & - & Short Code Length Compared To 1D & - & Two Photo-detectors at The Receiver \\ \hline
**2D-MD** & - & High Data Rate & - & Presence MAI \\  & - & Short Code Length Compared To 1D & - & Needs Narrow Filters \\  & - & Supports High Number of Users & - & \\ \hline
**2D-SWZCC** & - & High Data Rate & & \\
**2D-SWZCC** & - & Short Code Length Compared To 1D & - & Single Weight W = 1 \\  & - & Supports High Number of Users & & \\ \hline
**2D-PTZCC** & - & High Data Rate & & \\  & - & Short Code Length & - & Needs Narrow Filters \\  & - & Supports High Number of Users & & \\  & - & Low PINN Noise & & \\ \hline
**2D-HSSZCC** & - & High Data Rate & & \\
**2D-HSSZCC** & - & Low PINN Noise & - & Needs Narrow Filters \\  & - & Short Code Length Compared To 1D and 2D & - & Compatible with Even Number of Users \\  & - & Supports High Number of Users & & \\ \hline
**3D-PD** & - & High Data Rate & - & Two Photo-detectors at The Receiver \\  & - & Short Code Length Compared To 1D and 2D & - & More Complex \\ \hline
**3D-PD/MD** & - & High Data Rate & - & Two Photo-detectors at The Receiver \\  & - & Short Code Length & - & More Complex \\ \hline
**3D-MD** & - & High Data Rate & & \\  & - & Short Code Length Compared To 1D And 2D & - & Needs Narrow Filters \\  & - & Supports High Number of Users & & \\  & - & Direct Detection Technique & & \\ \hline
**3D-SWZCC** & - & High Data Rate & & \\  & - & Short Code Length Compared To 1D and 2D & & \\  & - & Supports High Number of Users & & \\  & - & Direct Detection Technique & & \\ \hline
**3D-PTZCC** & - & High Data Rate & & \\
**3D-PTZCC** & - & Short Code Length Compared To 1D and 2D & & \\  & - & Supports High Number of Users & & \\  & - & Direct Detection Technique & & \\ \hline
**3D-** & - & High Data Rate & & \\  & - & Short Code Length Compared To 1 DAnd 2D & & \\  & - & Supports High Number of Users & & \\  & - & Direct Detection Technique & & \\
**Proposed** & - & Simple Architecture & & \\
**3D-VWZCC** & - & Absence MAI & & \\  & - & Very Low PINN Noise & & \\  & - & Admits Any Number of Users and Any Code & & \\  & Weight & & \\  & - & Needs Simple Filters & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._In [19], a new design for spectral coding, called the Flexible Cross-Correlation Code (FCC), has been proposed. The suggested code has advantages such as flexible cross-correlation property for any number of users and any weight; furthermore, the proposed code provides better performance in terms of the bit error rate (BER) compared to the Modified Double Weight (MDW), dynamic cyclic shift (DCS), Modified Frequency Hopping (MFH) and Hadamard codes. Despite this, this code is characterized by PINN noise due to the intersections between the code spectral chips, which degrade the performance of the optical system. In [20], a new design coding for OCDMA systems called the Modified Double Weight (MDW) code has been developed for the non-coherent OCDMA system. Therefore, the developed code gives better performance compared to the modified frequency hopping (MFH) and Hadamard codes in terms of BER for a large number of users. However, the code is also characterized by PINN noise, which degrades the system performance as the number of users increases. In [21], a new one-dimensional spectral coding family called the Diagonal Eigenvalue Unity (DEU) code has been developed, where the proposed code is compatible with any weight; moreover, the code performance demonstrates that the DEU code gives better performance compared to random diagonal (RD), DCS, MFH, and modified quadratic congruence (MQC) codes in terms of the signal to noise ratio (SNR) and BER.