What is Co-Packaged Optics? | Why CPO Technology is the Future of Data Center Processing | Corning

Benoit Fleury
Published: May 8, 2025

Data center processing and networking capacities continue to be pushed to their limit with copper interconnections becoming increasingly less viable due to the rapid growth of artificial intelligence capabilities and networking models.

To meet the exponentially growing needs of data center networks while reducing power consumption created by increased processing speeds, bandwidths, and densities, optical connections must now make their way much closer to networking and processing integrated chips (ICs) to reduce the length of copper traces to these ICs. Co-Packaged Optics (CPO) achieves this by packaging the optical transceivers (often referred to as photonic chiplets) with the ICs on the same silicon substrate; this significantly reduces the length of the electrical path between optics and the electrical ICs, which in turn reduces power consumption while unlocking unprecedented levels of bandwidth concentration.

Fiber Beats Copper—and Here’s Why

The power needed to transmit electrical signals along a copper path starts to become prohibitive at data rates of 200 Gb/s, which is expected to reach the tipping point for when CPO starts to become a much better solution. The optical-to-electrical conversion that is performed by the optical transceiver is still needed in a CPO system, but it moves from a pluggable module located at the faceplate of the switching equipment to a small chip (or chiplet) that is co-packaged very closely to the target ICs inside the box. Data center chipset heavyweights Broadcom and Nvidia have both announced CPO-based data center networking products operating at 51.2 and 102.4 Tb/s.

Connecting the Dots

Connecting fibers to these transceiver chiplets, or photonic ICs (PICs), in a precisely aligned and reliable manner is a critical enabler for CPO systems. Currently, this is achieved by coupling an array of single-mode fibers to the edge or surface of the PIC. Each method has its pros and cons, and both are currently being developed by different chipset companies. The same types of fibers are used in either scenario, for which Corning is actively developing best-in-class fiber-to-chip connectivity solutions.

Early generation CPO systems, such as those announced by Broadcom and Nvidia for Ethernet switching, make use of high channel count Fiber Array Units (FAUs) that are designed to precisely align the fiber cores to their corresponding waveguides inside the PICs. These FAUs are challenging to make as they require high fiber counts, mixed single-mode (SM) and polarization maintaining (PM) fibers, integration of micro-optic components depending on the fiber-to-chip coupling mechanism, highly precise tolerance alignments, CPO-optimized fibers and multiple connector assemblies. Corning is well equipped to provide these complex inside-the-box harnesses and is ramping up operations to meet the needs of the industry as CPO technology adoption broadens.

As part of our 2025 OFC showcase, Corning launched the CPO FlexConnect™ fiber under our GlassWorks AI™ solutions —Corning’s one-stop shop for AI network needs both inside and outside the data center. The CPO FlexConnect fiber is a single-mode, bend-resilient fiber that is specifically optimized for short-length configurations, making it ideal for inside-the-box CPO fiber deployments.

The figure below illustrates an FAU assembly, with the FAU at the PIC end on the right, a SM/PM fiber harness and several optical connectors on the left that mate at the inside of the system’s faceplate.

At OFC 2025, Corning also showcased two examples of inside-the-box CPO fiber infrastructures. One of these was a single rack-unit mockup emanating a 102.4 Tb/s Ethernet switching system with 64 MMC faceplate connectors and a total of up to 1,024 signal fibers neatly organized to and from the 16 PICs that are co-located with the switching IC in the middle of the assembly. In addition, 16 pluggable laser source modules at the faceplate are interconnected to the same PICs by means of specialized fibers known as polarization-maintaining (PM) fibers.

The other CPO fiber infrastructure example that was showcased was a GPU-based interconnect system from Mixx Technologies, which also included MMC connectors and pluggable laser sources at the system’s faceplate, a mix of densely packed single mode and polarization maintaining fibers, and fiber management trays to ensure that the fibers are organized in a way that is easily serviceable. Having deployed a high number of densely packed fiber infrastructures in data center and telecom environments, Corning has the experience and know-how to ensure that these systems can be deployed both robustly and at scale.

Additionally, at OFC 2025, Corning previewed a proof of concept towards a more advanced method of connecting fibers to chips by means of a glass substrate with integrated optical waveguides. In addition to scale and cost benefits, extreme densities can be achieved at the edge of the PIC by bringing the waveguides very close together, down to about 30µm, which is far more than what can be achieved with even the thinnest fibers. Next generation fiber-to-chip coupling will enable GPU optics—which will require unprecedented levels of density and scale. Because Corning has the combination of glass, connector, and fiber expertise, we are uniquely positioned to integrate all these critical elements into the most advanced fiber-to-chip connector in the industry which will enable later generation CPO designs by our data center OEM customers.

What once appeared to be a far-reaching and futuristic technology, CPO has become a reality driven by phenomenal AI growth and the need to enable it with increased speeds and density while significantly reducing power consumptions. Corning has all the elements to address this need with innovative fiber and connectivity solutions and is excited to help move CPO forward now and in the years to come.