Real-Time 100 Gb/s PAM-4 for Access Links with up to 34 dB Power Budget

The growing demand for broadband access networks keeps motivating research for higher capacity in both wired and wireless access networks. Recently, the recommendation for 50G-PON with conventional NRZ modulation has been published. Bidirectional point-to-point access networks, also known as BiDi, used in mobile xHaul, are standardized up to 50 Gb/s with PAM-4 as modulation format. The evolution in view of a next generation 6G wireless encourages research towards higher bitrates for fronthaul systems. Hence, there is interest for having single channel BiDi links with a bitrate of at least 100 Gb/s. In this paper we experimentally evaluate four possible IMDD transceiver schemes suitable for optical access applications in the O-Band that can cover BiDi link losses up to a bitrate of 100 Gb/s using PAM-4. We employ an EML with either a 25G-based APD or an optically preamplified p-i-n photodiode (PD) with low-complexity FFE equalization and achieve a real-time power budget of 23.7 dB, just above BiDi B- loss class. By adding an optical booster, we demonstrate up to 34 dB power budget, exceeding with enough margin the highest BiDi class B loss of 25 dB.