Laser and Optoelectronic Engineering Department, University of Technology, Baghdad, Iraq


in this paper, an analytical model is developed to estimate a
nonlinear phase noise (NPN) due to Kerr fiber nonlinearity and its interaction
with amplifier noise in mode division multiplexing (MDM) systems. Our
analysis uses generalized coupled multimode nonlinear Schrödinger equations
(MM- NLSE) that describe the propagation of the mode superimposing in the
optical fiber. The nonlinear phase noise versus channel power and transmission
distance is evaluated by implementing our analytical model for LP01, LP11a,
and LP11b spatial modes. Each mode carries a 4-QAM signal at a symbol rate
of 20 Gsymbol/s. The results reveal that LP11 mode has a lower phase noise
variance than LP01 mode over entire transmission distances. Finally, the error
vector magnitude (EVM) versus channel power is quantified using an analytical