Christian G. Schaeffer

Machine Learning Techniques in Optical Communication

Machine learning techniques relevant for nonlinearity mitigation, carrier recovery, and nanoscale device characterization are reviewed and employed. Markov Chain Monte Carlo in combination with Bayesian filtering is employed within the nonlinear state-space framework and demonstrated for parameter estimation. It is shown that the time-varying effects of cross-phase modulation (XPM) induced polarization scattering and phase noise can be formulated within the nonlinear state-space model (SSM). This allows for tracking and compensation of the XPM induced impairments by employing approximate stochastic filtering methods such as extended Kalman or particle filtering. The achievable gains are dependent on the autocorrelation (AC) function properties of the impairments under consideration which is strongly dependent on the transmissions scenario. The gain of the compensation method are therefore investigated by varying the parameters of the AC function describing XPM-induced polarization scattering and phase noise. It is shown that an increase in the nonlinear tolerance of more than 2 dB is achievable for 32 Gbaud QPSK and 16-quadratic-amplitude modulation (QAM). It is also reviewed how laser rate equations can be formulated within the nonlinear state-space framework which allows for tracking of nonLorentzian laser phase noise lineshapes. It is experimentally demonstrated for 28 Gbaud 16-QAM signals that if the laser phase noise shape strongly deviates from the Lorentzian, phase noise tracking algorithms employing rate equation-based SSM result in a significant performance improvement (

MultiGbit/s transmission over a fiber optic mm-wave link

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Demonstration of an efficient technique for optical generation of microwave signals based on a fiber loop mirror

8 dB) compared to traditional approaches using digital phase-locked loop. Finally, Gaussian mixture model is reviewed and employed for nonlinear phase noise compensation and characterization of nanoscale devices structure variations.

Machine learning techniques in optical communication

Advances in broadband radio-over-fiber multigbit/s transmission links are presented. An optical double sideband with suppressed carrier (DSB-SC) spectrum is used to generate a mm-wave signal of outstanding performance. One sideband is modulated with baseband data rates of up to 10 Gbps. Transmission experiments prove this modulation scheme to be dispersion tolerant and error free transmission was demonstrated after 40 km of single mode fiber for data rates up to 5 Gbps. The limits of the setup were tested with data rates of 10 Gbps.

Optical generation of microwave signals based on an unbalanced fiber loop mirror

An efficient scheme for the optical generation of a dispersion tolerant double-sideband with suppressed carrier (DSB-SC) signal is presented. A fiber loop mirror, offering an optical bandwidth of more than 130 nm is used to filter out the required sidebands.

Continuous variable quantum key distribution with a real local oscillator using simultaneous pilot signals

Machine learning techniques relevant for nonlinearity mitigation, carrier recovery, and nanoscale device characterization are reviewed and employed. Markov Chain Monte Carlo in combination with Bayesian filtering is employed within the nonlinear state-space framework and demonstrated for parameter estimation. It is shown that the time-varying effects of cross-phase modulation (XPM) induced polarization scattering and phase noise can be formulated within the nonlinear state-space model (SSM). This allows for tracking and compensation of the XPM induced impairments by employing approximate stochastic filtering methods such as extended Kalman or particle filtering. The achievable gains are dependent on the autocorrelation (AC) function properties of the impairments under consideration which is strongly dependent on the transmissions scenario. The gain of the compensation method are therefore investigated by varying the parameters of the AC function describing XPM-induced polarization scattering and phase noise. It is shown that an increase in the nonlinear tolerance of more than 2 dB is achievable for 32 Gbaud QPSK and 16-quadratic-amplitude modulation (QAM). It is also reviewed how laser rate equations can be formulated within the nonlinear state-space framework which allows for tracking of nonLorentzian laser phase noise lineshapes. It is experimentally demonstrated for 28 Gbaud 16-QAM signals that if the laser phase noise shape strongly deviates from the Lorentzian, phase noise tracking algorithms employing rate equation-based SSM result in a significant performance improvement (>8 dB) compared to traditional approaches using digital phase-locked loop. Finally, Gaussian mixture model is reviewed and employed for nonlinear phase noise compensation and characterization of nanoscale devices structure variations.

Digital coherent receiver employing photonic downconversion for phase modulated radio-over-fibre links

A scheme for the generation of a dispersion tolerant double-sideband with suppressed carrier signal is presented. An unbalanced fiber loop mirror, offering an optical bandwidth of more than 130 mm is used to select the required sidebands. Therefore it is very suited for application in radio over fiber system using WDM.

Scalable Integrated DFT Demultiplexer for Terabit Optical OFDM Transmission

In this Letter, we propose a novel implementation of continuous variable quantum key distribution that operates with a real local oscillator placed at the receiver site. In addition, pulsing of the continuous wave laser sources is not required, leading to an extraordinary practical and secure setup. It is suitable for arbitrary schemes based on modulated coherent states and heterodyne detection. The shown results include transmission experiments, as well as an excess noise analysis applying a discrete 8-state phase modulation. Achievable key rates under collective attacks are estimated. The results demonstrate the high potential of the approach to achieve high secret key rates at relatively low effort and cost.

Experimental comparison of 10 Gbit in radio over fiber systems

A digital coherent receiver employing photonic downconversion is presented and experimentally demonstrated for phase-modulated radio-over-fibre optical links. The receiver is capable of operating at frequencies exceeding the bandwidth of electrical analog-to-digital converter by using photonic downconversion to translate the high-frequency input RF signal to the operating frequency range of the analog-to-digital converter. First, using linear digital demodulation scheme we measure SFDR of the link at microwave frequency of 5 GHz. Thereafter, successful signal demodulation of 50 Mbit/s Binary Phase Shift Keying (BPSK) modulated data signal at 5 GHz RF carrier frequency is experimentally demonstrated by using an analog-to-digital converter with only 1 GHz bandwidth. We successfully demonstrate signal demodulation, using the proposed digital coherent receiver with photonic downconversion, after 40 km of transmission through standard single mode fiber.

Simulation of polarization mode dispersion compensation based on EMTY-model and nonlinear optimization

We present a scalable optical filter structure for realization of a real-time capable DFT operation. The performance of a serial-parallel filter structure for demultiplexing eight channels in an optical OFDM system is analyzed.