Roundhill Investments' DRAM ETF targeting the memory trade has been a breakout hit in 2026 amassing close to $25 billion since April, and it is now betting that the photonics boom due to AI data center optical networking innovation will be another investable theme. Goldman Sachs projects that the total addressable market opportunity for optical networking will grow more than nine times over through 2028, from an estimated $15 billion to an estimated $154 billion, and Nvidia has been investing billions into photonics companies.