Simultaneous monitoring of the values of CD, Crosstalk and OSNR phenomena in the physical layer of the optical network using CNN

The aim of the research was to explore the possibilities of using the Asynchronous Delay Tap Sampling (ADTS) and Convolutional Neural Network (CNN) methods to monitor the simultaneously occurring phenomena in the physical layer of the optical network. The ADTS method was used to create a data sets showing the combination of Chromatic Dispersion (CD), Crosstalk and Optical to Signal Noise Ratio (OSNR) as optical disturbances in graphic form. Data were generated for 10 GB/s, Non-return-to-zero On–off keying (NRZ-OOK) and Differential Phase Shift Keying (DPSK) modulation and bit delays: 1 bit, 0.5 bit and 0.25 bit. A total of 6 data sets of 62,000 images each were obtained. The learning process was carried out for the number of epochs 50 and 1000. From the obtained learning results of the network, models with the best $$R^{2}$$ R 2 matching factor were selected. The learned models were further used to study the recognition of three phenomena simultaneously. The tests were carried out on sets of 2500 images in a combination of interference in the following ranges: 400–1600 ps/nm for CD and 10–30 dB for Crosstalk and OSNR. Very good results were obtained for recognizing simultaneously occurring phenomena using models learned up to 1000 epoch. Accuracy of over 99% was obtained for CD and Crosstalk for both modulations. In the case of the OSNR phenomenon, slightly weaker results were obtained above 96% in most cases. For models taught up to 50 epoch, very good results were obtained for the CD phenomenon (over 99%). For Crosstalk weaker results for OOK modulation were obtained. Poor results were obtained for the OSNR phenomenon, where recognition accuracy ranged from 50 to 80%, depending on the type of modulation and bit delay. Based on the conducted research, it was established that the use of ADTS and CNN methods enables monitoring of simultaneously occurring CD, Crosstalk and OSNR interference in the physical layer of the optical network, while maintaining the requirements for Optical Performance Monitoring systems. These requirements are met for network models learned up to 1000 epoch.

Intelligent Matching of the Control Voltage of Delay Line Interferometers for Differential Phase Shift Keying-Modulated Optical Signals

In optical communications, differential phase shift keying (DPSK) provides a desired modulation format that offers high tolerance to nonlinear effects in high-speed transmissions. A DPSK demodulator converts the phase-coded signal into an intensity-coded signal at receivers. One demodulation scheme is called balanced detection and is based on a tunable delay line interferometer (DLI). Demodulation performances are determined by the phase delay generated by the DLI, while the phase delay is controlled by a tunable driving voltage on the DLI device. However, a problem in the dynamic adjustment of the control voltage prevents the application of DPSK demodulators. The receivers need to scan the whole control voltage range of the DLI and find the control voltage that maximizes the demodulation performance, but the scan-based method needs to undergo a very long searching time. In our work, we found that the relation between DLI control voltages and demodulation performance can be predicted rapidly by a feedforward neural network (FNN). In this paper, we propose a new method to quickly locate the best DLI control voltage based on an FNN. We also verify the proposed method in simulations and telecommunication systems, and the results show that the proposed method can significantly improve the efficiency of resolving the best demodulation voltages.

Transmitter Aperture Diameter Effect in 40 Gb/s Inter-Satellite Optical Wireless Communication System

Optical wireless communication systems have turned into a state-of-the-art technology because of their superior performance uniqueness and innumerable characteristics, as compared to radio frequency. One optical wireless communication application is Inter-Satellite Optical Wireless Communication. Inter-Satellite Optical Wireless Communication systems can be improved by using, for example, advanced modulation formats and adjusting the aperture diameters. We demonstrate an analysis based on the aperture diameter effect in the transmission of a single channel using a 40 Gb/s Inter-Satellite Optical Wireless Communication system and three different modulation methods, specifically differential phase-shift keying with a duty ratio of 66% or 33% and duobinary. These three modulations were chosen among various modulation formats due to the advantages they provide, i.e., the differential phase-shift keying provides stronger robustness to fiber nonlinearity and duobinary provides higher chromatic dispersion tolerance to mitigate the system requirements for dispersion compensation. The results show the effect of different transmitter aperture diameters (from 2 to 20 cm) at a constant distance (200 km) in terms of the quality factor and minimum Bit Error Rate. We conclude there is a great loss in the small aperture diameter, even in the presence of the best modulation format; therefore, as the aperture diameter increases the Q-factor increases, but some of the increased rise is linear and some changes from linear to non-linear at a fixed Q-factor point equal to 5.63.