High bitrate data transmission in the 8-14 µm atmospheric window using an external Stark-effect modulator with digital equalization
Hamza Dely, Mahdieh Joharifar, Xiaodan Pang, Djamal Gacemi, Toms Salgals, Richard Schatz, Yan‐Ting Sun, Thomas Bonazzi, Étienne Rodriguez, Yanko Todorov, Angela Vasanelli, Aleksejs Udaļcovs, Sandis Spolītis, Vjačeslavs Bobrovs, Oskars Ozoliņš, Sergei Popov, Carlo Sirtori
Abstract
High bitrate mid-infrared links using simple (NRZ) and multi-level (PAM-4) data coding schemes have been realized in the 8 µm to 14 µm atmospheric transparency window. The free space optics system is composed of unipolar quantum optoelectronic devices, namely a continuous wave quantum cascade laser, an external Stark-effect modulator and a quantum cascade detector, all operating at room-temperature. Pre- and post-processing are implemented to get enhanced bitrates, especially for PAM-4 where inter-symbol interference and noise are particularly detrimental to symbol demodulation. By exploiting these equalization procedures, our system, with a full frequency cutoff of 2 GHz, has reached transmission bitrates of 12 Gbit/s NRZ and 11 Gbit/s PAM-4 fulfilling the 6.25 % overhead hard-decision forward error correction threshold, limited only by the low signal-to-noise ratio of our detector.