What Is CPO? A Complete Guide to Co-Packaged Optics for AI Data Centers｜Technology Year：2026

As AI servers, GPU clusters, and large-scale AI data centers continue to expand, the challenge of high-speed interconnects is no longer simply about achieving more bandwidth.

The real engineering question is becoming:

How can higher bandwidth be achieved while controlling electrical transmission distance, power consumption, signal integrity, bandwidth density, and thermal conditions?

CPO, or Co-Packaged Optics, has gained significant attention because it directly addresses these challenges.

Its core concept is straightforward:

Move the optical engine closer to the switch ASIC, shorten the distance traveled by extremely high-speed electrical signals, and convert electrical signals into optical signals earlier.

CPO is increasingly being integrated into next-generation AI networking platforms, showing that the technology is moving from research and validation toward practical high-bandwidth network systems.

What Is CPO?

CPO stands for:

Co-Packaged Optics

It is a high-speed optical interconnect architecture.

CPO is not a type of optical fiber, a specific connector, or one fixed optical transceiver form factor.

The main idea is to place:

Switch ASIC

and:

Optical Engine

much closer together, potentially within a shared or closely integrated packaging architecture.

This reduces the physical distance between high-speed electronic switching silicon and the optical conversion system.

How Does Traditional Optical Networking Work?

Traditional data center switches widely use pluggable optical transceivers.

A simplified high-speed signal path looks like:

Switch ASIC
↓
High-Speed PCB Electrical Channel
↓
Front-Panel Connector / Cage
↓
Optical Transceiver
↓
Optical Fiber

The switch ASIC generates high-speed electrical signals, which travel through PCB traces toward the front panel.

Only after reaching the optical transceiver does the system perform:

Electrical → Optical

conversion.

This architecture provides strong advantages in modularity, maintenance, and ecosystem maturity.

However, as SerDes rates and network speeds increase, the high-speed electrical channel between the ASIC and front-panel optics becomes increasingly difficult to design.

What Does CPO Change?

CPO moves the optical engine much closer to the switch ASIC.

A simplified data path becomes:

Switch ASIC
↓
Short High-Speed Electrical Channel
↓
Co-Packaged Optical Engine
↓
Optical Fiber

The key change is:

The electrical signal no longer needs to travel across a relatively long PCB path before reaching the optical engine.

Electrical-to-optical conversion happens earlier, after which the signal primarily travels through fiber.

CPO therefore changes:

Where optical conversion takes place.

It does not fundamentally change optical fiber itself.

Why Do AI Data Centers Need CPO?

One of the major differences between AI data centers and traditional enterprise data centers is the massive amount of East-West traffic generated within AI clusters.

GPUs continuously exchange:

• Tensor data
• Model parameters
• Gradients
• Collective communication traffic
• Distributed training data
• Inference traffic

As GPU clusters scale from dozens of accelerators to hundreds or thousands, switching bandwidth and port density must increase at the same time.

AI networking is therefore moving toward:

• 800G
• 1.6T
• Higher-speed Ethernet
• 200G-per-lane signaling
• Higher-radix switches
• Greater optical bandwidth density

This creates a critical engineering question:

Switch ASICs can continue getting faster, but can the electrical channel between the ASIC and optical module keep up?

This is where CPO begins to provide system-level value.

Challenge 1: High-Speed Electrical Channel Loss

High-speed electrical signals passing through PCBs, connectors, and other channel components can experience:

• Insertion loss
• Return loss
• Crosstalk
• Jitter
• Impedance discontinuities

As data rates increase, these issues generally become more difficult to control.

Longer ASIC-to-front-panel electrical paths may require more demanding:

• PCB materials
• Routing
• Connector design
• Equalization
• Signal conditioning
• FEC
• Channel budgeting

The basic CPO strategy is:

If extremely high-speed electrical signals are difficult to transmit over longer distances, reduce the distance they need to travel.

This is one of the fundamental reasons for moving the optical engine closer to the ASIC.

Challenge 2: Power per Bit

High-speed data centers increasingly care not only about:

Total power consumption

but also:

How much power is required to transmit each bit of data?

An AI data center may contain large numbers of 400G, 800G, and 1.6T ports.

If every high-speed electrical and optical interconnect consumes substantial power, the impact extends to:

• Power delivery
• Cooling
• Rack density
• Operating cost

By shortening the high-speed electrical path, CPO can potentially reduce part of the power required for electrical signal conditioning and transmission.

However, CPO power-efficiency claims should always be evaluated at the system level and within the context of the specific platform.

Challenge 3: Bandwidth Density

Another major AI networking challenge is:

How much bandwidth can one switch deliver within a limited physical space?

As port speeds increase from:

400G → 800G → 1.6T

switch front panels, connectors, PCB routing, and thermal design all face greater pressure.

CPO can help increase bandwidth density by reducing some of the limitations associated with long high-speed electrical routing and front-panel architecture.

The value of CPO is therefore not only:

A faster individual port

but also:

More total network bandwidth within a limited switch and rack footprint.

Why Is 200G per Lane Important for CPO?

High-speed Ethernet is progressing toward:

200G per lane

and eventually even higher signaling rates.

Conceptually:

4 × 200G = 800G

8 × 200G = 1.6T

As lane rates increase, electrical channel design becomes more difficult.

The higher the SerDes rate, the greater the value of minimizing electrical reach between the switch ASIC and the optical engine.

This is why 200G-per-lane technology is closely associated with next-generation CPO systems.

What Components Are Used in a CPO System?

CPO is not simply an ASIC connected directly to fiber.

A practical system may involve:

Component	Main Function
Switch ASIC	High-speed packet switching
SerDes	High-speed electrical I/O
Optical Engine	Electrical-to-optical and optical-to-electrical conversion
Silicon Photonics	Implements high-density optical functions
Laser Source	Provides optical light
Fiber Interface	Couples optical signals into fiber
Electrical Interface	Connects ASIC and optical engine
Thermal Solution	Manages heat from ASIC and optical components

Different vendors may use different architectures.

Therefore:

CPO is an architectural category, not one fixed product shape.

Are Silicon Photonics and CPO the Same Thing?

No.

Silicon Photonics is a technology platform that uses silicon-based processes to implement optical functions.

CPO is a packaging and system architecture that places optical engines close to high-speed ASICs.

They often appear together because silicon photonics is well suited for building compact, high-density optical engines.

A simple way to understand the distinction is:

Silicon Photonics = Optical Technology Platform

CPO = Optical-Electrical Integration Architecture

CPO can use silicon photonics, but the two terms are not interchangeable.

Does CPO Still Need Optical Fiber?

Yes.

This is one of the most common misunderstandings.

CPO does not replace fiber.

It changes:

Where the electrical signal becomes an optical signal.

After electrical-to-optical conversion, data still needs to travel over optical fiber toward:

• Other switches
• Other racks
• GPU clusters
• Data halls
• Other network equipment

Therefore:

CPO + Optical Fiber

is a very natural architecture.

Where Is the Laser Located in CPO?

There is no single fixed answer.

Some CPO architectures use an:

External Laser Source, or ELS

where the laser is placed outside the main CPO package and delivers light to the optical engine.

Potential advantages include:

• Independent laser maintenance
• Keeping the laser away from the hottest ASIC area
• Better serviceability in some designs
• Greater flexibility for laser redundancy

External laser architectures can therefore help address certain reliability and thermal challenges.

However, they also introduce additional optical coupling and system-design considerations.

Why Is Thermal Design Important for CPO?

CPO places:

High-Power Switch ASICs

and:

Optical Engines

much closer together.

This shortens the electrical path, but also places temperature-sensitive optical components near high-power silicon.

Thermal design must therefore consider:

• ASIC temperature
• Optical engine temperature
• Laser temperature
• Cooling architecture
• Thermal coupling
• Long-term reliability

As AI networking switches continue increasing in bandwidth, CPO thermal management becomes an increasingly important system-level challenge.

What Are the Main Engineering Challenges of CPO?

CPO offers important advantages, but it also introduces new challenges.

1. Serviceability

Traditional optical modules can be removed and replaced independently.

CPO requires a different approach to handling failures in optical engines, lasers, and fiber connections.

2. Manufacturing Yield

ASICs, optical engines, packaging, and fiber integration all affect final production yield.

3. Thermal Management

High-power ASICs and temperature-sensitive optical components are placed closer together.

4. Fiber Management

Large numbers of optical lanes require efficient fiber routing from the package toward the front panel or other equipment.

5. Testing

CPO requires more than electrical testing.

Verification may involve:

• Optical testing
• Thermal testing
• Packaging validation
• Reliability testing
• System-level testing

6. Supply Chain Integration

A CPO system may involve:

• ASIC suppliers
• Silicon photonics vendors
• Laser suppliers
• Fiber manufacturers
• Connector suppliers
• Packaging companies
• Cooling-system suppliers

CPO therefore turns high-speed interconnect design into a broader system-integration challenge.

Will CPO Replace Pluggable Optical Transceivers?

It should not currently be viewed that way.

CPO offers advantages in:

• Short electrical reach
• High bandwidth density
• Potentially lower power per bit
• High-speed ASIC-to-optics integration

Pluggable optics offer advantages in:

• Modularity
• Serviceability
• Flexible transmission reach
• Mature ecosystem
• Multi-vendor deployment

Future AI data centers are more likely to use a combination of:

**Pluggable Optics

• LPO
• NPO
• CPO**

depending on the system requirements.

The key question is:

Has bandwidth density and power consumption become severe enough to justify changing the traditional optical architecture?

Which AI Data Center Applications Should Pay Attention to CPO?

CPO is particularly relevant for:

• AI factories
• Hyperscale data centers
• Large GPU clusters
• 800G / 1.6T networks
• Ultra-high-bandwidth switches
• High-radix networking
• High port density
• Scale-out fabrics
• Power-constrained networking

Not every data center requires CPO.

If the network operates at lower speeds or places very high value on field serviceability and modular upgrades, pluggable optics may remain the more appropriate architecture.

CPO primarily targets:

Next-generation AI networks with extremely high bandwidth and bandwidth density.

How Does CPO Affect Cables, Connectors, and Fiber?

Moving optics closer to the ASIC does not eliminate cables and connectors.

Instead, their roles change.

Electrical Interconnects

The ASIC and optical engine still require very high-speed electrical interfaces.

Optical Fiber

Once electrical-to-optical conversion occurs, fiber becomes the primary medium for longer-distance transmission.

Fiber Connectors

High optical-lane counts require:

• High-density fiber connections
• Low insertion loss
• Reliable mechanical alignment
• Maintainable fiber management

Cable Management

As switch bandwidth density increases, large numbers of fibers create new routing and maintenance challenges.

CPO therefore does not mean:

“Connectors and cables will disappear.”

Instead:

High-speed interconnect systems will increasingly shift from longer electrical channels toward higher-density optical interconnects.

Where Is CPO Technology Heading?

Several important development directions can already be identified.

Higher Lane Rates

100G/Lane → 200G/Lane → Higher Rates

Higher Switch Bandwidth

51.2T → 102.4T → Higher Capacity

Lower Power per Bit

Reducing high-speed electrical transmission and signal-processing power.

Greater Silicon Photonics Integration

Increasing optical engine density and functionality.

External Laser Architectures

Improving selected thermal and serviceability characteristics.

Higher-Density Fiber I/O

Supporting larger numbers of optical lanes.

More Complete Industry Standards

Developing common electrical, optical, laser, management, and mechanical interfaces.

CPO is therefore becoming one of the key technology paths for next-generation AI networking.

Why Do AI Data Centers Need CPO? The Core Answer

The entire article can be summarized in one sentence:

AI data center bandwidth is growing so quickly that the traditional high-speed electrical channel between the switch ASIC and front-panel optics is facing increasing loss, power, and bandwidth-density pressure. CPO addresses this by moving optics closer to the ASIC.

CPO is therefore not mainly solving:

“Optical fiber is not fast enough.”

It is solving:

“The electrical signal is becoming increasingly difficult to carry before it reaches the optical fiber.”

That is the most important concept for understanding CPO.

As networking continues from:

800G
→ 1.6T
→ Higher-Speed Ethernet

switch ASICs, SerDes, optical engines, silicon photonics, fiber, connectors, thermal systems, and packaging will become more tightly integrated into one system-level design challenge.

CPO is one of the most important architectures emerging from this transition.

Frequently Asked Questions

What Is CPO?

CPO stands for Co-Packaged Optics. It places optical engines much closer to switch ASICs to shorten the high-speed electrical channel and convert electrical signals into optical signals earlier.

Why Is CPO Suitable for AI Data Centers?

Large AI clusters require extremely high network bandwidth and port density. As 800G, 1.6T, and 200G-per-lane technologies develop, longer electrical channels face increasing loss, power, and thermal challenges, making CPO more valuable.

Is CPO the Same as Silicon Photonics?

No. Silicon photonics is an optical technology platform, while CPO is a system architecture that places optical engines near ASICs. Silicon photonics is often used to build CPO optical engines.

Does CPO Still Require Fiber?

Yes. CPO changes the location of electrical-to-optical conversion. After conversion, optical fiber is still required to transmit data.

Will CPO Completely Replace Optical Modules?

That is unlikely to be the most accurate expectation. CPO is suited for very high bandwidth density and power-sensitive AI networking, while pluggable optics continue to provide advantages in modularity, serviceability, and ecosystem maturity. Multiple optical architectures are likely to coexist.

SyncTronics Solutions

As AI data centers move from 400G and 800G toward 1.6T and higher bandwidths, high-speed interconnect design is expanding beyond simple cable and connector selection to include electrical channels, optical fiber, signal integrity, thermal conditions, and high-density interconnect architectures. SyncTronics can support the evaluation of high-speed electronic interconnect and customized cable assembly solutions based on equipment interfaces, data rates, cable lengths, connectors, cable or fiber architecture, and actual application requirements.

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We welcome you to visit our Contact Us page and share your project requirements and contact information. Our team is committed to responding quickly and professionally, evaluating the most suitable products and electronic interconnect solutions based on your product specifications, application requirements, and project objectives. We also provide technical recommendations and customized engineering support to help shorten product selection and development time, reduce project risks, and accelerate your path to mass production. We look forward to the opportunity to work with you and provide reliable technical support and practical solutions for every stage of your project.

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