An Ultra-Compact 106-Gb/s PAM4 × 8-Channel Linear-Drive VCSEL-Based Transceiver for Co-Packaged Optics

We report a design and optical link characteristics of an ultra-compact 106-Gb/s PAM4 × 8-channel linear-drive VCSEL-based transceiver for Co-Packaged Optics. This optical transceiver employs the record narrowest 0.3-mm-pitch LGA for the electrical interface. To expand the bandwidth, we use a core-less building-up multi-layer organic substrate to avoid impedance mismatch of the vias in the core layer. A 3-dB bandwidth of the differential lines is as wide as >53 GHz based on an electromagnetic simulation. When operating the optical transceiver with a bit stream of 106-Gb/s PAM4 2<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup>-1 PRBSQ in a loopback optical link without any CDR functionalities, BER measures less than the KP4-FEC threshold for both serial and 8-channel operations.