Reclaiming Light Dropped During Optical Modulation to Bias Avalanche Photodetectors
JLT, vol. 41, no. 6, pp. 1704-1711, Mar. 2023
Bernhard Schrenk, and Margareta Vania Stephanie
The introduction of avalanche photodetectors in optical interconnects can extend the unallocated optical budget while unleashing further opportunities to migrate to novel datacenter network architectures. The required high-voltage rail that biases the photodiodes would involve a specialized electronic circuitry but will be instead harvested directly at the optical layer, taking advantage of the dropped power during optical modulation at local transmitters. Rather than dumping light resulting from extinct space bits, we will collect this contribution and convert it to a high-voltage bias by means of a photovoltaic power conversion circuit that is shared among and powered from all constituent data lanes of the optical interconnect. We will experimentally demonstrate that this energy reclamation circuit can sustain the sourced current during avalanche photodetection whilst maintaining a bias rail at ~25V with continuity, as will be proven for up to 64 data lanes. We demonstrate an optical budget of ~30 dB for 10 Gb/s/lane transmission, with a reception penalty as small as 0.2 dB with respect to an electrically biased photoreceiver. We will further elaborate on the limitations linked to the proposed concept, such as in terms of dynamic range.