Are all optical modules packaged in the same way

Not all optical modules are packaged the same way; they range from traditional pluggable modules to co-packaged and in-package optical designs, each optimized for different applications and integration levels.

Traditional Pluggable Modules

Traditional optical modules, such as SFP, SFP+, QSFP, QSFP28, XFP, and CFP, are designed as hot-swappable pluggable units that connect to network equipment via standardized interfaces like LC or SC connectors. These modules are physically separate from the switching ASIC and communicate through SerDes channels. They are widely used in data centers, enterprise networks, and telecom systems for applications ranging from 1G to 400G Ethernet and SONET/SDH networks. The form factor and pin count vary depending on speed and generation, e.g., SFP is smaller than GBIC, while QSFP28 supports higher data rates with multiple fiber channels .

Co-Packaged Optics (CPO)

CPO modules integrate the optical engine directly with the switching or routing ASIC on the same substrate or interposer. Unlike pluggable modules, CPO is not hot-swappable and is tightly integrated, reducing the length of high-speed electrical traces from centimeters to millimeters. This integration lowers power consumption, reduces latency, and allows higher bandwidth density, making it ideal for hyperscale data centers and AI infrastructure. CPO modules rely on silicon photonics, 2.5D/3D integration, and high-density substrates to achieve co-location of photonic and electronic components .

In-Package Optical I/O

In-package optical I/O takes integration further by embedding optical interconnects (chiplets) within the same package as compute chips such as CPUs, GPUs, or FPGAs. This approach enables chip-to-chip optical communication across boards, racks, or compute rows, offering extremely low latency and high bandwidth. It is particularly suited for emerging distributed compute fabrics, memory-semantic fabrics, and machine learning scale-out systems, representing a more revolutionary step compared to traditional pluggable modules .

Summary

Optical modules are not uniform in packaging. The main categories include:

• Pluggable modules: Standardized, hot-swappable, separate from ASICs, widely used in networking.
• Co-packaged optics (CPO): Integrated with ASICs, non-pluggable, optimized for power, latency, and density.
• In-package optical I/O: Embedded within compute chip packages, enabling direct chip-to-chip optical communication. Each packaging type is designed to meet specific performance, density, and integration requirements, reflecting the evolution of optical technology from traditional networking to advanced data center and compute applications.