Proof-of-Concept of the Time and Spectral Optical Aggregation Network

In this article, we present the proof of concept (PoC) of the time and spectral optical aggregation (TISA) approach that allows a better filling of the time and spectral resources of an optical transport network. Some innovative solutions have been implemented, such as a new and fast tunable laser that permits to color the bursts sent in the TISA network, as well as their transmission with both DP-QPSK and DP-16QAM coherent multi-band (MB) OFDM formats. BER versus OSNR measurements have been achieved showing less than 1-dB penalty in back-to-back or after transmission. The tolerance of bursts against frequency mismatch occurring between the transceiver and the optical filter that extracts a sub-band inside the MB-OFDM signal has also been evaluated, and ~1.5 GHz tolerance has been measured for bursts of ~6.7 GHz bandwidth. Furthermore, in order to mitigate the transients in the coherent receiver that faces alternatively the presence or absence of signal, a novel channel estimator based on a sliding window has been introduced. Its efficiency and performance has been experimentally validated, and its ability to suppress the error threshold of the BER versus OSNR curves has been demonstrated. By the experimental proof of concept delivered here, the ability of the TISA network to perform with a good level of performance the transparent routing and sub-wavelength aggregation/disaggregation in the time and spectral domains simultaneously has been established. Beyond the important and crucial aspect of the optimal filling of the optical resources, our PoC demonstrate the ability of the TISA approach to push the flexibility of an optical transport network at its limit while allowing a cost and power consumption limitation obtained by the removal of costly and power-hungry optical-electrical-optical regenerators.