title: Theoretical calculation on ICI reduction using digital coherent superposition of optical OFDM subcarrier pairs in the presence of laser phase noise.
abstract: Digital coherent superposition (DCS) of optical OFDM subcarrier pairs with Hermitian symmetry can reduce the inter-carrier-interference (ICI) noise resulted from phase noise. In this paper, we show two different implementations of DCS-OFDM that have the same performance in the presence of laser phase noise. We complete the theoretical calculation on ICI reduction by using the model of pure Wiener phase noise. By Taylor expansion of the ICI, we show that the ICI power is cancelled to the second order by DCS. The fourth order term is further derived out and only decided by the ratio of laser linewidth to OFDM subcarrier symbol rate, which can greatly simplify the system design. Finally, we verify our theoretical calculations in simulations and use the analytical results to predict the system performance. DCS-OFDM is expected to be beneficial to certain optical fiber transmissions.
authors.forename: Xingwen
authors.initials: X
authors.lastname: Yi
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Yun
authors.initials: Y
authors.lastname: Lin
authors.forename: Kun
authors.initials: K
authors.lastname: Qiu