This paper considers the Optical Frequency Division Multiplexing (OFDM) system, where optical fiber link is designed and ultra wide band Erbium Doped Fiber Amplifier (EDFA) is used as an in-line amplifier whose gain compensates the loss of the optical fiber. The optical signal is degraded by the accumulated Amplified Stimulated Emission (ASE) noise from the optical amplifier in the chain. At the photo detector, ASE noise is converted to electrical noise primarily through signal—ASE beating, which leads to Bit Error Rate (BER) flooring. Other optical parameters in system design consideration are channel power divergence and maximum channel power relative to the threshold levels of optical nonlinearities—Stimulated Raman Scattering (SRS), Stimulated Brillouin Scattering (SBS), Four-Wave Mixing (FWM), etc. The paper concludes that the product of the number of EDFAs and their gain decreases as the number of channel multiplexed increases; this depends on the data rate. The paper compares the results for 1 GB, 10 GB and 40 GB signal bit rates for the required bit error rate of 10^-9 for Amplitude-Shift Keying (ASK) and Phase-Shift Keying (PSK) modulation formats.

Geography often limits the ability to provision repeater (i.e., optical amplification) sites between two remote terminal locations. Such a phenomenon appears in a variety of applications like submarine links (island hopping and oil rigs), and links spanning large unpopulated areas (deserts, jungles, and mountain ranges). Such limitations necessitate the need for a single long fiber span. Even when repeater sites are technically feasible, a single repeater with fewer spans can reduce operational expenses and increase security.

Long, repeaterless, point-to-point links represent a fast-growing segment of the optical communications market, requiring practical and cost-effective approaches that can be rapidly and easily deployed. There are three possible methods for extending the reach of single-span links: unique modulation techniques, better Forward-Error Correction (FEC) algorithms, and the advanced optical amplification technology.

Telecommunications Journal, Optical Frequency Division Multiplexing, OFDM, Ultra wWide Band, Erbium Doped Fiber Amplifier, EDFA, Optical Nonlinearities, Modulation Techniques, Amplified Stimulated Emission, ASE, Wavelength Division Multiplexing,WSM, Optical Amplifiers, Amplitude-Shift Keying, Four-Wave Mixing, FWM .