Stephen G. Evangelides

Polarization multiplexing with solitons

It is shown both analytically and with numerical simulation, and confirmed experimentally in transmission over distances up to approximately 10000 km, that solitons maintain a high degree of polarization over an ultra-long distance transmission system consisting of birefringent dispersion-shifted fiber segments and erbium amplifiers. Based on that fact, the authors propose a polarization/time division multiplexing technique which should allow the single-wavelength bit-rate capacity of an ultra-long distance soliton transmission system to be doubled with little or no significant increase in bit error rate. >

The sliding-frequency guiding filter: an improved form of soliton jitter control

By gradually translating the peak frequency of guiding filters along its length, we create a fibertransmission line that is substantially opaque to noise while remaining transparent to solitons. This trick allows the use of stronger filters, and hence greater jitter reduction, without incurring the usual penalty of exponentially rising noise from the excess gain required to overcome filterloss.

Long-distance soliton propagation using lumped amplifiers and dispersion shifted fiber

It is shown both analytically and by numerical simulation, that solitons can traverse great distances through a chain of lumped amplifiers connecting dispersion shifted fiber spans. The fiber spans can also have large fractional variations in D. The resultant pulse distortions and dispersive wave radiation tend to be negligible, as long as the length scale of the variations in energy and dispersion are short relative to the soliton period. >

Hamiltonian dynamics of dispersion-managed breathers

An analytic description is presented for the pulse dynamics in a dispersion-managed communications system in which the average dispersion is in the anomalous regime. A variational formalism reduces the governing equations to a planar Hamiltonian system for which a geometrical interpretation of the pulse dynamics is given. The reduced model gives a simple method for calculating the ideal enhanced initial power for a dispersion-managed breather and further exhibits a long-time periodic behavior, which is present in the full governing equations. Extensive numerical simulations verify the range of validity of the reduced equations.

40 Gb/s WDM Transmission of Eight 5 Gb/s Data Channels Over Transoceanic Distances using the Conventional NRZ Modulation Format

The transmission of many Wavelength Division Multiplexed (WDM) channels over transoceanic distances can be limited by the nonlinear interactions between channels. In this work the nonlinear interactions were suppressed by tailoring the chromatic dispersion of the transmission fiber1 and operating the system at low channel power. These techniques made possible the transmission of eight 5 Gb/s Non-Return-to-Zero (NRZ) channels over 8000 km for a total transmission capacity of 40 Gb/s.

Energy transfers and frequency shifts from three soliton collisions in a multiplexed transmission line with periodic amplification

In this paper, we show that there can be four wave mixing between three solitons having different, but equally spaced, frequencies. While this does not happen with solitons in a uniform lossless fiber, we show that in a transmission line with loss and periodically placed amplifiers, it can happen. The spatial periodicity of the transmission line serves to phase match the four wave mixing of the three solitons. This results in permanent frequency shifts for two of the three solitons and energy exchanges between all three solitons.

Intersymbol interference induced by delay ripple in fiber Bragg gratings

We have observed the intersymbol interference (ISI) induced on a signal due to traversing a fiber Bragg grating having periodic delay ripple. A simple model of the grating transfer function agrees well with the observed ISI behavior.

Nonlinear interaction of signal and noise in 10 Gb/s long distance RZ transmission

We show that nonlinear coupling between signal and ASE noise in long-haul WDM dispersion-managed transmission is a significant impairment which limits the amount of accumulated dispersion that can be tolerated. A variety of dispersion compensation scenarios for a broad range of signal wavelengths is analyzed through computer simulations.