Experimental Investigation of a Recurrent Optical Spectrum Slicing Receiver for Intensity Modulation/Direct Detection Systems Using Programmable Photonics
Kostas Sozos, Francesco Da Ros, Metodi P. Yankov, George Sarantoglou, Stavros Deligiannidis, Charis Mesaritakis, Adonis Bogris · Journal of Lightwave Technology · 2024
Photonic computing and signal processing are rapidly regaining attention, capitalizing on the saturation of digital electronics capabilities, owed to the ending of the Moore's law era. Optical communications are among the fields in which digital signal processing (DSP) struggles to offer a viable long-term solution, as its power consumption rises significantly in the latest generation optical links. For example, the traditional intensity modulation and direct detection (IM/DD) systems suffer from challenging problems such as the chromatic dispersion induced power fading effect, which necessitates the use of powerful digital equalizers in the 800G and 1.6T optical transceivers. Here, we experimentally validate our previous numerical works in recurrent optical spectrum slicing (ROSS) accelerators for dispersion compensation in IM/DD links. For this, we utilize recurrent filters implemented both through a waveshaper and by exploiting novel programmable photonic platforms. The ROSS accelerators exploit frequency processing in order to mitigate the power fading effect, which hinders the scalability of IM/DD systems. By equalizing even 80 km of 64 Gb/s PAM-4 transmission in C-band, we prove that our system can offer an appealing solution in highly dispersive channels. We employ the simplest digital equalization in the form of a feed-forward equalizer (FFE), avoiding throughput, latency, and complexity restrictions other digital equalizers impose. We achieve to reduce the bit error rate (BER) from 0.11 to less than 1 × 10−2with the use of only two filter nodes, whereas BER approaches 10-3when three nodes are incorporated. These results correspond to almost two orders of magnitude BER gain.