Abstract
This paper presents design and implementation of a new two-dimensional fixed right shifting (2D-FRS) code in optical code-division multiple access (OCDMA) systems. The proposed code employs spatial domain in combination with spectral encoding to elevate orthogonality between the adjacent codes. In comparison with the existing 2D coding schemes, 2D-FRS not only reserves the multiple interference-cancellation property, but also provides better performance against the effects of shot, thermal and phase-induced intensity noise. Investigation of the proposed system using numerical and simulation approach shows that larger number of simultaneous users can be supported by 2D-FRS system in comparison with existing counterparts under given bit-error-rate (BER). This paper further examines the effect of dispersion on performance of 2D-FRS based OCDMA system due to the use of numerous fiber strands between the transmitter and receiver modules for spatial encoding operation. Investigation is made in terms of data rate, fiber span and channel spacing. Analysis using a highly recognized software called OPTISYSTEM verifies that the proposed system is able to support data rates of up to 32 × 1 Gbps without employing dispersion compensation fibers (DCFs). It is also shown that application of DCF can further negate MAI and support higher transmission capacity leading to a tradeoff between the limited dispersion effects and the MAI.
If g = 0 ∩ h ≠ 0 and h = 0 ∩ g ≠ 0, hence RI(1)(g,h) and RI(2)(g,h) have nonzero value. This can be used to remove the effect caused by Ag,h with g = 0 ∩ h ≠ 0 and g ≠ 0 ∩ h from RI(0)(g,h). Deducting Eqs. (7) and (8) from Eq. (6), Eq. (9) is attained as follows