Abstract-Mode division multiplexing (MDM) systems using orbital angular momentum (OAM) modes can recover the data in D different modes without recourse to full (2D×2D) multiple input-multiple output (MIMO) processing. One of the biggest challenges in OAM-MDM systems is the mode instability following fiber propagation. Previously, MIMO-free OAM-MDM data transmission with two modes over 1.1 km of vortex fiber was demonstrated where optical polarization demultiplexing was employed in the setup. We demonstrate MDM data transmission using two OAM modes over 1.4 km of a specially designed ring core fiber (RCF) without using full MIMO processing or optical polarization demultiplexing. We demonstrate reception with electrical polarization demultiplexing, i.e., minimal 22 MIMO, showing the compatibility of OAM-MDM with current polarization demultiplexing receivers.
We theoretically study the performance of single sideband discrete multi-tone (SSB-DMT) in the C-band with intensity modulation and direct detection (IMDD). Our analysis allows us to quantify the impact of different noise sources such as signal-to-signal beating interference, phase-to-amplitude noise, attenuation, and receiver sensitivity on SSB-DMT. Our analytical tools also allow us to optimize the signal-to-carrier power ratio to maximize SSB-DMT throughput. We provide equations to calculate bit error rate of bit allocated SSB-DMT. Finally we examine various system parameters (laser linewidth, system bandwidth, and fiber length) to determine their impact on the performance of zero guard band SSB-DMT.
We present a comprehensive study of nonlinear distortions from an optical OFDM transmitter. Nonlinearities are introduced by the combination of effects from the digital-to-analog converter (DAC), electrical power amplifier (PA) and optical modulator in the presence of high peak-to-average power ratio (PAPR). We introduce parameters to quantify the transmitter nonlinearity. High input backoff avoids OFDM signal compression from the PA, but incurs high penalties in power efficiency. At low input backoff, common PAPR reduction techniques are not effective in suppressing the PA nonlinear distortion. A bit error distribution investigation shows a technique combining nonlinear predistortion with PAPR mitigation could achieve good power efficiency by allowing low input backoff. We use training symbols to extract the transmitter nonlinear function. We show that piecewise linear interpolation (PLI) leads to an accurate transmitter nonlinearity characterization. We derive a semi-analytical solution for bit error rate (BER) that validates the PLI approximation accurately captures transmitter nonlinearity. The inverse of the PLI estimate of the nonlinear function is used as a predistorter to suppress transmitter nonlinearity. We investigate performance of the proposed scheme by Monte Carlo simulations. Our simulations show that when DAC resolution is more than 4 bits, BER below forward error correction limit of 3.8 × 10(-3) can be achieved by using predistortion with very low input power backoff for electrical PA and optical modulator.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.