Power Grid Class Co-packaged Photonics NRZ Selection Guide

NRZ-based co-packaged photonics modules are selected based on electrical interface bandwidth, optical modulation type, power efficiency, and integration with ASICs or switch fabrics.Key Selection Criteria1. Electrical Interface and Bandwidth NRZ (Non-Return-to-Zero) signaling is typically used for 25–28 Gb/s per lane in 100G PSM4 modules, with a single wavelength centered at 1310 nm for all lanes . When selecting NRZ CPO modules, ensure the electrical interface supports the required baud rate and has low insertion loss. For example, VCSEL-based transceivers with 0.3-mm pitch LGA can achieve 28-Gbaud operation with a 3-dB bandwidth of 14 GHz . 2. Optical Modulation Type NRZ is simpler than PAM4 and is preferred for lower power consumption and reduced signal processing complexity. NRZ modules are compatible with both VCSEL-based and silicon photonics (SiP) transceivers, but SiP may offer higher-order modulation options if future upgrades are needed . 3. Integration and Co-Packaging Modules should be co-packaged close to the ASIC to minimize electrical transmission loss and improve energy efficiency. VCSEL-based transceivers are attractive for low-power, high-density integration, while SiP-based modules allow higher electro-optical bandwidth density and support sub-pJ/b transmission efficiency . 4. External Light Source (ELS) Considerations Some CPO designs use an external light source to supply continuous-wave light via polarization-maintaining fibers. ELS classifications range from standard to Very High Power (VHP) classes, which may influence module selection depending on required optical output and link budget . 5. Modulator and Optical Performance When selecting NRZ CPO modules, consider optical modulation amplitude (OMA), extinction ratio (ER), and signal-to-noise ratio (SNR). Micro-ring modulators (MRMs) offer compact footprints and high electro-optical bandwidth but require larger voltage swings, whereas VCSELs provide low drive current and power-efficient operation . 6. Standards and Implementation Agreements Refer to OIF Implementation Agreements for 3.2 Tb/s CPO modules and 100G PSM4 specifications to ensure compliance with mechanical, electrical, and optical requirements . These documents provide guidance on cable attach formats, optical lane configurations, and co-packaging constraints.Practical RecommendationsFor 100G NRZ links, choose modules with 4x25 Gb/s lanes and 1310 nm wavelength.For high-density ASIC integration, consider VCSEL-based CPO for low power or SiP-based CPO for higher bandwidth and future scalability.Evaluate electro-optical performance metrics (OMA, ER, SNR) to meet link budget requirements.Ensure mechanical compatibility with LGA or other pluggable interfaces for dense packaging.Check ELS class if using external light sources to match optical power requirements. By considering these factors, engineers can select NRZ-based co-packaged photonics modules optimized for power grid, data center, or high-speed switch applications while balancing bandwidth, power efficiency, and integration constraints.