The co-packaged optics (CPO) market is experiencing rapid growth, driven by the increasing demand for high-speed data transmission and the exponential expansion of data centers and cloud services.
NVIDIA's latest product roadmap highlights plans to launch a CPO version of the Quantum 3400 X800 InfiniBand switch in Q3 2025, followed by the Spectrum4 Ultra X800 Ethernet switch in 2026. The InfiniBand switch will feature 144 MPO optical interfaces, supporting 36 3.2T CPO modules, with four 28.8T switching chips inside, providing a total switching capacity of 115.2T.
The architecture of these switches leverages a multi-plane design, enabling efficient distribution of optical signals. After entering through MPO optical ports, fibers are split by a shuffle box into four separate paths, each connecting to a different switch chip. This approach effectively segments the signal source into smaller units, which are then aggregated at the CX8 network card. The multi-plane setup allows independent planes to operate concurrently, optimizing throughput and reducing signal congestion. The shuffle box plays a pivotal role in this architecture, performing critical signal routing and processing functions.
On-Board Connection, between front panel and Optical Engines (OE)
High-speed CPO switches are projected to require thousands of internal fiber connections. Managing the routing of these fibers within the switch’s compact structure poses multiple challenges, including maintaining uniform fiber lengths despite varying distances between optical engines and the front panel, as well as preventing excessive bending that could lead to signal degradation. To overcome these obstacles, advanced solutions such as flexible optical shuffle technology are employed. When paired with high-density connectors and adapters, this approach effectively minimizes length variations and ensures robust, high-performance signal transmission.
Fiber flexible circuit products enable higher-density optical routing solutions. Conventional 1U optical patch panels typically support up to 24 fiber connections for splicing and distribution. In a 40U cabinet (with a height of 2 meters), this results in a total fiber capacity of just 960 fibers. By integrating optical fiber flex circuits with high-density MT connectors, a 1U optical panel can accommodate up to 600 fibers (12*50). When scaled to a 40U cabinet, the total fiber capacity increases dramatically to 24,000 fibers—representing a 20-fold increase in density compared to conventional solutions. This significant improvement in density is a key advantage for high-speed, high-capacity data centers and networking systems.
Front Panel Connectors/Adapters
The shuffle box utilizes high-density connectors, such as MPO and MMC connectors, to enable high-speed, high-density signal connections and transmissions, meeting the demands for network performance and equipment integration in data center applications. CPO switches require extensive fiber deployment internally, and using high-fiber-count MPO connectors can significantly reduce the number of ports needed on the front panel. For example, a 51.2T CPO switch may require 1,152 optical fibers, including 1,024 standard single-mode fibers and 128 polarization-maintaining fibers. By utilizing 16-fiber MPO connectors, 64 MPO adapters and connectors are needed, streamlining deployment and improving integration efficiency.
PM Fiber Assemblies Between External Laser Source(ELS) and OE
Due to its ease of maintenance and broad accessibility, the External Laser Source (ELS) is currently one of the most widely adopted solutions for CPO light sources. The performance of CPO optical engines is highly sensitive to the polarization state of the incident light from the ELS, requiring the laser polarization state to remain stable during signal transmission. To achieve this, Polarization Maintaining Fiber (PMF) is employed to connect the light source to the switching chip. PMF ensures that light propagates along a single polarization direction within the fiber, ensuring signal stability and transmission reliability.
Photonics Integrated Circuit (PIC) Connections
Optical interconnection between silicon-based optoelectronic chips and external optical fibers is a critical packaging technology that requires low-loss signal transmission and high-precision alignment at the micrometer scale. Due to the high refractive index of silicon-based materials, the waveguide mode field diameter is typically much smaller than that of single-mode optical fibers, leading to high insertion losses during mode conversion.3D optical waveguides overcome the limitations of traditional planar waveguide technologies by enabling flexible light guidance and coupling in three-dimensional space, meeting the demands of more complex packaging configurations. Fabricated using advanced techniques such as photolithography and laser direct writing, 3D optical waveguides offer precise geometric control and superior optical performance, providing a reliable solution for the efficient interconnection of next-generation silicon-based optoelectronic chips.
