Various Sources of Noise in Optical Fiber Communication Systems: A Review

This paper reviews different sources of noise in optical fiber communication systems. The most important sources of noise, in such systems, are semiconductor lasers, optical amplifiers, and optical detectors.First, we review the relative intensity noise (RIN) and phase noise in semiconductor lasers. We show that, at low frequencies, RIN is negligible, and reaches its maximum at the damping frequency. RIN decreases with an increase in injection current, while it maximizes for the threshold current, at a certain frequency. The phase noise, which is related to laser line width, is constant below the damping frequency and increases to its maximum at the damping frequency. In semiconductor lasers, both RIN and phase noise decrease with an increase in the output power.Next, Amplified spontaneous emission (ASE) noise in erbium doped fiber amplifiers (EDFA) is reviewed. We show that, while ASE noise increases with an increase in the pump power, it decreases with an increase in the input signal power, for the various pump powers.Then, reviewing the formulation of noise figure (NF) in semiconductor optical amplifiers (SOA), we study the effects of cavity thickness and length on NF in both Fabry Perot (FP) and traveling wave amplifiers (TWA).Then we review sources of noise in an optical detector, and present an equivalent electric circuit model for it, including signal to noise ratio (SNR) and bit error rate (BER).Then, modal noise in a multimode optical fiber is reviewed. Finally, crosstalk as the main limiting parameter in optical multiplexer/demultiplexer units in multiwavelength systems is reviewed.