Subspace tracking for independent phase noise source separation in frequency combs

Advanced digital signal processing techniques in combination with ultra-wideband balanced coherent detection have enabled a new generation of ultra-high speed fiber-optic communication systems, by moving most of the processing functionalities into digital domain. In this paper, we demonstrate how digital signal processing techniques, in combination with ultra-wideband balanced coherent detection can enable optical frequency comb noise characterization techniques with novel functionalities. We propose a measurement method based on subspace tracking, in combination with multi-heterodyne coherent detection, for independent phase noise sources identification, separation and measurement. Our proposed measurement technique offers several benefits. First, it enables the separation of the total phase noise associated with a particular comb-line or -lines into multiple independent phase noise terms associated with different noise sources. Second, it facilitates the determination of the scaling of each independent phase noise term with comb-line number. Our measurement technique can be used to: identify the most dominant source of phase noise; gain a better understanding of the physics behind the phase noise accumulation process; and confirm, already existing, and enable better phase noise models. In general, our measurement technique provides new insights into noise behavior of optical frequency combs

Sensitivity Study for the B+→K∗(892)+μ+μ−B^+ \rightarrow K^*(892)^+\mu^+ \mu^- Decay at the Belle II Experiment

With B meson decays it is possible to probe the Standard Model of particle physics without thenecessity to investigate high energy scales. In previous analyses, the quark transition $b \to s\ell^{+}\ell^{-}$ showed signs of New Physics in kinematic observables that deviated from the Standard Modelpredictions. Among others, the decay $B^{+} \to K^{*}(892)^{+} \mu^{+} \mu^{-}$ is particularly suited for thesearch since it is highly suppressed in the Standard Model. New Physics effects therefore couldhave similar amplitudes to Standard Model effects which makes them detectable.In this thesis the sensitivity of the Belle II experiment of this particular decay is determined.Using simulated particle decays the amount of signal and background candidates is estimatedfor data sets with various integrated luminosities which were selected to be relevant for theBelle II data taking period. A new B meson reconstruction is presented which uses the Belle IIAnalysis Framework and a boosted decision tree algorithm to classify individual events for theirlikelihood of being a signal event. This boosted decision tree is trained using 29 observableswhich are derived from the particle decay and show separation between the shapes of signal andbackground events.The presented analysis outperforms the predecessor Belle analysis as the reconstruction efficiencyis doubled and the expected amount of background is reduced by a factor of eight

Evaluating Energy Consumption of Internet Services

This paper summarizes recent reports on the internet’s energy consumption and the internet’s benefits on climate actions. It discusses energy-efficiency and the need for a common standard for evaluating the climate impact of future communication technologies and suggests a model that can be adapted to different internet applications such as streaming, online reading and downloading. The two main approaches today are based on how much data is transmitted or how much time the data is under way. The paper concludes that there is a need for a standardized method to estimate energy consumption and CO2 emission related to internet services. This standard should include a method for energy-optimizing future networks, where every Wh will be scrutinized

Subspace tracking for phase noise source separation in frequency combs

It is widely acknowledged that the phase noise of an optical frequency comb primarily stems from the common mode (carrier-envelope) and the repetition rate phase noise. However, owing to technical noise sources or other intricate intra-cavity factors, residual phase noise components, distinct from the common mode and the repetition rate phase noise, may also exist. We introduce a measurement technique that combines subspace tracking and multi-heterodyne coherent detection for the separation of different phase noise sources. This method allows us to break down the overall phase noise sources associated with a specific comb-line into distinct phase noise components associated with the common mode, the repetition rate and the residual phase noise terms. The measurement method allow us, for the first time, to identify and measure residual phase noise sources of a frequency modulated mode-locked laser.</p