arXiv subjects
Publications and source records attributed to Lothar Moeller.
We report tidal-induced latency variations on a transpacific subsea cable. Week-long recordings with a precision phase meter suggest length changes in the sub-meter range caused by the Poisson effect. The described method adds to the toolbox for the new field >>optical oceanic seismology<<.
Wireless networks operating at terahertz (THz) frequencies have been proposed as a promising candidate to support the ever-increasing capacity demand, which cannot be satisfied with existing radio-frequency (RF) technology. On the other hand, it likely will serve as backbone infrastructure and could therefore be an attractive target for eavesdropping attacks. Compared with regular RF spectrum, wireless channels in the THz range could be less vulnerable to interceptions because of their high beam directionality and small signal coverage. However, a risk for eavesdropping can still exist due to the multipath effects caused by unintended scattering. In this work, an eavesdropping risk for THz channel passing atmospheric turbulences and producing compromising emissions is investigated from a physical layer perspective. A model combining signal attenuation due to turbulence, gaseous absorption and beam divergence, is developed for prediction of deterministic and probabilistic signal leakages. The secrecy capacity and outage probability of the THz channel are derived and analyzed with respect to variations of the turbulence strength and other channels characteristics. The dependence of the channel performance on the eavesdropper's position is investigated with respect to the maximum safe data transmission rate (MSR) and the signal leakage region. Design results for THz channels are provided to minimize an eavesdropping risk at physical layer.
We report the experimental observation of SOP scattering in Stokes space caused by nonlinear depolarization (NLDP) of light in fiber. In addition to our previous characterizations of NLDP by SOP speed histograms and Stokes vector spectra, we measure SOP scattering angles. For trans-Pacific propagation distances these angles range within a few degrees.
Experimental Stokes vector spectroscopy characterizes polarization state noise in nonlinear fiber transmission. Noise bandwidths of a few MHz are observed from XPM-blurred receive SOPs using a polarization scrambling interferometer. This method can detect data pattern correlations among WDM channels that contribute to performance degradations in signalling.
We report the experimental observation of a novel transmission phenomenon in optical long-haul communication systems. Un-polarized ASE depolarizes via nonlinear fiber interactions a cw laser light during their co-propagation which leads to small but measurable ultra-fast polarization state fluctuations at the fiber output. We provide a phenomenological approach and a theory that qualitatively corroborates our experimental results. One of our major findings suggests that the applicability of the often used Manakov equation needs to be scrutinized for highly accurate studies of nonlinear polarization state evolutions in noisy environments. The described phenomenon leads to a qualitatively different microscopic understanding of nonlinear light propagation in fiber and can contribute towards an explanation for todays commonly perceived gap between simulated and experimentally obtained system performance in optical data transmission.