Effect of Four-Wave Mixing on Optimal Placement of Optical Amplifier in WDM Star Networks

Abstract

In this article, the effect of four-wave mixing (FWM) and amplified spontaneous emission (ASE) noise on WDM optical star networks has been investigated. Analysis for the evaluation of probability of error has been carried out (a) when only FWM is present and (b) when both FWM and ASE noise are present. Numerical results are presented in the graphical and tabular forms for the practical values of parameters.Finally, optimal location of the amplifier in the network has been identified as being before the star coupler preceding the receiver.

Theoretical investigations of the combined effect of fibre nonlinearities, amplifier and receiver noise in a DWDM transmission system

“…Considering data bits "1" and "0" being transmitted as a mark and space respectively, FWM_ASE beat noise will have two different values named as FWM_ASE(1) for data bit "1" and FWM_ASE(0) for data bit "0". Similarly, FWM_signal has further two types: FWM_signal (1) and FWM_signal (0) corresponding to transmission of data bit "1" and data bit "0" respectively [6]. Considering all these noise terms, noise variances for bits "1" and "0" are as under…”

“…where P (r) s is the power received at the receiver, R 0 is the responsivity of the photodetector and the parameter C(0) is the coefficient for bit 0 and given by [6] …”

“…The two conventional limiting factors in designing optical communication systems, namely, fiber loss and dispersion, are relatively well understood, and can be easily overcome by optical amplifiers and dispersion compensation but fiber nonlinearities have not been fully analyzed and understood despite a rich collection of literature dealing with fiber nonlinearities [2][3][4][5][6][7][8][9][10]. Therefore, it is crucial to understand fiber nonlinearities and their effects on fiber-optic communication systems.…”

“…A deeper look re- veals that the noise generated by a detector puts a real limit on the sensitivity of a receiver [11]. Along with the basic receiver noises, beat noises are also generated at the receiver [6].…”

“…Singh et al [6] made comparative study of all the configurations and concluded that placement of optical amplifier as an inline amplifier is the optimal position as it requires minimum power for given probability of error. Fellegara [7] gave a systematic approach for evaluating the optimal placement of an optical amplifier on a fibre link without considering fibre nonlinearities.…”