We propose two methods based on machine learning algorithms to estimate the level of spectral overlapping in a specific optical channel, without information of adjacent channels in Nyquist-wavelength division multiplexing (WDM) systems. The first method uses the fuzzy c-means (FCM) clustering algorithm to relate the membership degrees of the FCM matrix with the level of spectral overlapping in frames of 10 k symbols that relied on the k-nearest neighbors algorithm. The second method uses the density-based spatial clustering of application with noise algorithm to identify the level of spectral overlapping based on the number of symbols classified as noise (outliers) as well as the number of extra clusters found in a constellation diagram, resulting in an overlapping index. Both methods were experimentally verified in a 3 × 16 Gbaud 16-QAM Nyquist-WDM system with different channel spacing. Knowing a priori the level of OSNR, results showed accuracy percentages up to 91% and up to 100% by the first proposed method in a multiclass and a binary classification, respectively. Moreover, the second method can achieve a percentage estimation up to 100% when optical channels are overlapped more than 12.5%. Thereby, both methods could be implemented in monitoring tools for incoming gridless optical transmission systems.
The first Brazilian high speed integrated 100G-DPQPSK transmitter on a 4 × 3 mm silicon photonic chip is presented. The novel photonic component allows optical signal generation of advanced modulation formats in 25GHz bandwidth. Furthermore, in this paper we also present our vision on required integrated photonics targeting 400G optical transmission systems.
Next generation ultra-broadband elastic optical networks maximize system-bandwidth utilization based on flexible diverse traffic demands accommodation. Research on novel network architectures and system components such as datarate variable transponders and hybrid amplification schemes are needed to allow geographical context adjustability as well as capacity system upgradeability from Gbps to Tbps. In this paper we report experimental validations on deployed Brazilian optical fiber of a data-rate variable transmitter feasible for both metro and long-haul applications. The developed transmission system exhibits spectral efficiencies of 4.58, 6.25 and 3.41 b/s/Hz for 1400, 700 and 4900 km of optical transmission respectively.
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