TL;DR: As AI networking shifts to 1.6T, transmission distance (from rack to chip) has replaced raw speed as the primary engineering bottleneck.
This post analyzes the three core architectures—MPO, NPO, and CPO—and their impact on density, power efficiency, and hardware serviceability for the next decade of AI infrastructure.
We live in an era where AI benchmarks are obsessed with numbers like 800G and 1.6T. However, speed is merely the surface result of a much deeper transformation. The real battleground for the next decade of AI infrastructure is distance.
From the rack to the silicon itself, the physical connection is being radically reinvented. In the following analysis, I break down the three fundamental routes — MPO, NPO, and CPO — exploring how each balances the critical trade-offs of density, power consumption, and serviceability.
Introduction
“Optical Interconnect” might sound like a complex buzzword, but it boils down to three fundamental questions: Where does the optical signal come from? How is it transmitted? And to whom is it delivered? MPO, NPO, and CPO represent three different answers to these questions, focusing on the connector, the distance, and the packaging, respectively. Despite their similar-sounding names, they serve entirely different functions in the modern data center.
Many observers confuse these routes because they only look at the resulting speed — 800G, 1.6T, or 3.2T. However, speed is not the cause. The real bottleneck for next-gen performance is the physical distance between the optical engine and the compute chip. Shorter distances mean faster signals, lower loss, and drastically reduced power consumption.
- MPO is a physical layer connector, solving high-density fiber interfacing.
- NPO (Near-Packaged Optics) moves the optical engine out of the pluggable module and places it next to the chip, shortening distance from centimeters to millimeters.
- CPO (Co-Packaged Optics) integrates the optical engine directly onto the same substrate as the compute chip, compressing the distance to micrometers.
I. MPO: The “Bulk Aggregator” of Fiber Density
MPO (Multi-fiber Push On) is essentially about efficiency through density — stuffing dozens of fiber cores into a single connector. While traditional connectors are “one-by-one,” MPO is “bundle-by-bundle.” In AI data centers, where fiber counts have skyrocketed from hundreds to tens of thousands of cores, MPO is the only viable solution for large-scale deployment.
The Industry Logic: The larger the AI compute cluster, the more rigid the demand for MPO. A 100,000-card cluster requires hundreds of kilometers of internal cabling. Moreover, MPO is a “consumable” product — fiber jumpers and connectors require regular replacement and cleaning, creating stable, recurring demand. MPO may not be the “sexiest” tech, but it is the most certain foundation of the physical layer.
II. NPO: The “Relocation” of the Optical Engine
NPO (Near-Packaged Optics) centers on one tactical move: taking the optical engine out of the pluggable transceiver and placing it right next to the compute chip. By reducing the transmission distance to a few millimeters, signal loss and power consumption drop significantly.
The Industry Logic: NPO is the “strategic middle ground.” It offers better performance than pluggable solutions and better serviceability than CPO. The optical engine and chip remain “neighbors” — either can be replaced or upgraded independently. As CPO technology matures and yields stabilize, NPO serves as a critical bridge for the industry to validate Silicon Photonics and optimize cooling solutions.
III. CPO: The “Unified Marriage” of Optics and Compute
CPO (Co-Packaged Optics) is the ultimate solution. By welding the optical engine and the compute chip onto the same substrate, the signal exits the chip and immediately enters the engine for conversion. Power consumption is minimized, and bandwidth density is maximized.
The Industry Logic: The trade-off is the loss of modular serviceability. If either the engine or the chip fails, the entire substrate is lost. Therefore, CPO industrialization hinges on two factors: Yield and Reliability. In 2026, we are seeing a major shift — top-tier GPU platforms have confirmed CPO as a priority, and major Cloud Service Providers (CSPs) have completed system validation for 3.2T modules. The industry is moving from R&D to mass production.
Summary: Three Routes, One Goal
- MPO solves “How to connect fibers.”
- NPO solves “Where to place the optical engine.”
- CPO solves “How to unify the engine and the chip.”
They are not mutually exclusive but rather co-evolving. MPO provides high-density connectivity at the physical layer; NPO builds the bridge for CPO; and CPO represents the final integration of electronics and photonics. The future of optical interconnect is not a solo performance by one route, but a symphony of all three. The true winners will be the companies positioned across this entire technological spectrum.
