The explosive growth of cloud computing and AI – from generative, and reasoning, to (ultimately) agentic systems – is creating unprecedented demand for bandwidth, as the amount of data that must be moved both within and between data centers continues to surge. In turn, this exposes growing limitations in the underlying interconnects that not only span the data center fabric and rack level but also extend deep inside servers – down to where they link XPUs, memory, and other system components at the package and die level. Copper-based (electrical) interconnects have long been the industry’s workhorse thanks to their low cost, simplicity, and reliability. Yet today, they are increasingly hitting fundamental limits: while highly energy-efficient electrical links can be realized, they are typically confined to very short reaches (on the order of millimeters). At longer distances and higher lane rates, power consumption rises sharply, thermal constraints intensify, and signal integrity degrades. In other words, electrical I/O is rapidly becoming a key barrier to scaling next-generation AI and machine learning systems. Optical interconnects have emerged as a critical path forward. By transmitting data using light rather than electrical signals, they are far less sensitive to distance, enabling much better energy efficiency while mitigating many of the crosstalk and thermal challenges inherent to copper links. However, even optical technologies are now being pushed to new extremes – as the need emerges for (multi) terabit-per-second interfaces, ultra-high energy efficiency, and extremely low (sub-microsecond) latency. Meeting these requirements will take more than incremental innovation. It calls for a fundamental rethinking of the optical interconnect roadmap; one that progressively brings optics closer to the silicon – from the front panel, into the package, and ultimately firmly integrated into the wafer stack. Pluggable optics (PO): The longstanding – and still very much alive – workhorse For more than two decades, pluggable optical transceivers have been the backbone of high-speed telecom and datacom networks – powering everything from enterprise workloads and video streaming to today’s hyperscale cloud infrastructure. Inserted into standardized ports on switches, routers, and servers, pluggables convert electrical signals from the host into optical signals for transmission over fiber – and back again on the receive side. They deliver: Modularity and flexibility – optics can be upgraded independently of the (electrical) host. Serviceability – pluggables are hot-swappable, meaning they can be replaced without system downtime. Multi-vendor interoperability – achieved via IEEE 802.3 standards, and through widely-adopted multi-source agreement (MSA) form factors such as QSFP, QSFP-DD, and OSFP. Thermal stability – the optical engine sits in a front-panel cage, physically separated from the power‑dense ASIC; this helps protect lasers, modulators, and photodetectors from excessive heat (improving reliability). Across successive generations, pluggable optical transceivers have scaled from 100/200G to 400G and 800G by pushing baud rates (the number of symbols transmitted per second on a single optical lane), adopting higher-order modulation (such as PAM-4), and increasing the number of parallel lanes. And despite their maturity, pluggable optics continue to evolve. First-generation 1.6T pluggable transceivers , for instance – relying on 200Gbps per-lane data rates, combined in an eight-lane parallel architecture – are approaching sampling and early deployment, targeting direct-reach (DR) intra-data center links as well as forward-reach (FR) connections over single-mode fiber. The key enabler is silicon photonics (SiPho) , which underpins this scaling through a combination of (silicon-based) optical and electronic building blocks, including Mach–Zehnder modulators that play a central role in enabling cost-effective 200Gbps per-lane operat