Selection of Red Light Sources for Data Center Interconnection

For data center interconnection, red light sources around 1310 nm are typically used, with the choice between external or integrated sources depending on link distance, power budget, and scalability requirements.Wavelength ConsiderationsFor DCI links, the O-band (around 1310 nm) is commonly used to minimize chromatic dispersion over short to medium distances, which is critical for high-speed intra-data center links. Red light sources in this band are suitable for both single-mode fiber (SMF) and multi-mode fiber (MMF) deployments, with SMF preferred for longer distances and higher bandwidths .External vs Integrated Light SourcesExternal Light Sources: These are separate from the transceiver or switch ASIC and can provide higher optical power, which is beneficial for longer links or when multiple fibers are aggregated. They are more flexible for wavelength-division multiplexing (WDM) and can scale to high switch bandwidths (up to 102.4 Tb/s) with link budgets exceeding 4 dB .Integrated Light Sources: Co-packaged with the switch or transceiver, these reduce electrical interconnect losses and power consumption but may be more sensitive to temperature and thermal management. Integrated sources can improve link budgets by 2–4 dB for 51.2 Tb/s switching and reduce the number of required fiber attachments .Single- vs Multi-Wavelength SourcesSingle-Wavelength Sources: Simpler and cost-effective for short-reach links, typically used in direct detection architectures.Multi-Wavelength Sources (DWDM/CWDM): Enable higher aggregate bandwidth over the same fiber infrastructure. Colored optics over passive DWDM allow flexible scaling, while colorless (gray) optics over active DWDM provide similar advantages with simplified inventory management .Modulation and DetectionDirect Detection: Suitable for short-reach intra-data center links, simpler and lower cost, but link budgets are typically lower (less than 5 dB for 102.4 Tb/s switching).Coherent Detection: Supports higher link budgets (over 13 dB) and longer distances, enabling 102.4 Tb/s switching with improved signal integrity .Practical Selection GuidelinesDistance and Fiber Type: Use SMF with LR4 or ER4 optics for longer DCI links; MMF with SR4 or DR4 optics for short-reach connections.Power Budget: External sources are preferred when higher optical power is needed; integrated sources are advantageous for power efficiency and reduced footprint.Scalability: Multi-wavelength sources are recommended for future-proofing high-capacity switches.Thermal Management: Ensure adequate cooling for integrated sources to maintain reliability and performance.Compatibility: Verify that pluggable optics are compatible with existing switch and DCI equipment . By carefully evaluating these factors, data center operators can optimize red light source selection for reliable, high-bandwidth interconnection while minimizing power consumption and maximizing scalability.