Performance Evaluation of Optical Coded Communication Systems with Optical Amplifiers in the Presence of Noise Components Generated by Optical Devices
The individual noise components introduced from fiber optic devices, such as optical amplifiers, laser transmitters, and photo-detectors, are discussed. A performance analysis of fiber optic sub-carrier multiplexed light-wave system employing M-ary QAM with intensity modulation and direct detection scheme (M-ary QAM-SCM IM/DD) is presented. The benefits of coded system employing error control code, such as Bose, Chaudhuri, and Hocquenghem (BCH) code, in contrast with conventional Mary QAM (un-coded system) are investigated. The performance of fiber optic system with optical amplifier for both cases, coded and un-coded systems, are quantified in-terms of bit error rate (BER). The system includes laser diode as transmitting device, optical amplifier as amplifying device, fiber link as transmission medium, and photo-diode as receiving device. Each of these devices together with its own contribution of introducing a specified noise component is analyzed and compared.
The obtained results indicate that the coded system improves the BER for the same value of signal input power. However, the gain saturation of optical amplifier deteriorates the range of signal input power for efficient operation of the system. Finally, the obtained results show that performance of coded system as a function of signal input power is governed by the code rate of the used BCH code. The performance deterioration for both un-coded and coded systems is shown to be dominated by signal spontaneous emission and spontaneous-spontaneous emission noise components.
Keywords: Fiber optic link, System performance, Optical amplifier, Noise sources, Noise components, Coding, Bit error rate, Sub-carrier system, Quadrature amplitude modulation, Detection, Receiver sensitivity, Optical devices, Lasers, Photo detectors.