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The explosive demand of broadband services nowadays requires data communication systems to have intensive capacity which subsequently increases the need for higher data rate as well. Although implementation of multiple wavelengths channels can be used (e.g. 4 × 25.8 Gb/s for 100 Gb/s connection) for such desired system, it usually leads to cost increment issue which is caused by employment of multiple optical components. Therefore, implementation of advanced modulation format using a single wavelength channel has become a preference to increase spectral efficiency by increasing the data rate for a given transmission system bandwidth. Conventional advanced modulation format however, involves a degree of complexity and costly transmission system. Hence, carrierless amplitude phase (CAP) modulation format has emerged as a promising advanced modulation format candidate due to spectral efficiency improvement ability with reduction of optical transceiver complexity and cost. The intriguing properties of CAP modulation format are reviewed as an attractive prospect in optical transmission system applications.

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In this paper, a performance study of 8-Pulse-Position Modulation (PPM), 8-Digital Pulse Interval Modulation (DPIM), and 8-Reverse Dual Header-Pulse Interval Modulation (RDH-PIM) implementation in Verilog hardware design language is presented. The hardware design is chosen over software design since it could provide much more flexibility in term of transmission rate and reduce the workload of the processor in the complete system. Using 50 MHz clock as the reference data clock speeds, the transmission rate recorded are 11.11 Msymbol/second or 33.33 Mbps, 9.09 Msymbol/s or 27.27 Mbps, and 6.25 Msymbol/s or 18.75 Mbps for 8-RDH-PIM, 8-DPIM, and 8-PPM respectively. We conclude that 8-RDH-PIM modulator design provides better performance in term of bandwidth utilization and transmission rate as compared to 8-PPM and 8-DPIM.

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