100G optical modules are high-speed transceivers used in modern data centers and networks, with QSFP28 as the primary form factor and multiple standards and modulation techniques to meet diverse transmission needs.

Overview and Standards

100G optical modules are essential for high-bandwidth applications such as AI, big data, and cloud computing, forming the backbone of 25G/100G network architectures in data centers . The standards for these modules are defined by IEEE 802.3 and MSA (Multi-Source Agreement) organizations. IEEE provides official specifications for Ethernet speeds, while MSA defines multi-vendor packaging, electrical, and optical interfaces to ensure interoperability and standardization across manufacturers .

Form Factors and Types

The QSFP28 module is the most widely used 100G form factor, offering low power consumption, high port density, and compact size . Key QSFP28 module types include:

• 100GBASE-SR4: Parallel transmission using four 25Gbps channels over multimode fiber, suitable for short distances.
• 100GBASE-PSM4: Parallel single-mode fiber module with four 25Gbps channels, optimized for data center interconnects.
• 100GBASE-CWDM4: Uses Coarse Wavelength Division Multiplexing (CWDM) to transmit four wavelengths over single-mode fiber, cost-effective for medium distances.
• 100GBASE-LR4: Long-distance module (up to 10 km) using WDM to multiplex four optical signals into a single channel, featuring cooled DFB lasers and industrial-grade packaging .

Modulation Techniques

100G modules employ advanced modulation formats to increase data rates efficiently:

• NRZ (Non-Return-to-Zero): Traditional binary signaling.
• PAM4 (Pulse Amplitude Modulation 4-level): Doubles data rate per channel by encoding two bits per symbol.
• Coherent modulation: Used for long-haul and high-capacity links, combining amplitude and phase modulation for improved spectral efficiency .

Single-Lambda 100G Optics

Modern single-lambda 100G optics simplify module design by using one wavelength per channel, reducing complexity and cost while enabling gradual upgrades to 400G networks . This approach allows network operators to future-proof investments and scale infrastructure incrementally.

Design Considerations

When selecting 100G optical modules, consider:

• Transmission distance and fiber type (multimode vs single-mode).
• Power consumption and thermal management, as high-speed modules generate heat .
• Compatibility with existing switches and routers, especially for future 400G upgrades .
• Cost efficiency, balancing performance with deployment budget .

Applications

100G QSFP28 modules are widely used in:

• Data center core and aggregation layers
• Enterprise networks
• Service provider networks
• High-performance computing clusters These modules provide reliable, high-speed connectivity while supporting scalable network growth and advanced data center architectures. In summary, 100G optical modules like QSFP28 combine standardized form factors, advanced modulation, and flexible deployment options to meet the growing demands of modern high-speed networks, offering both performance and future scalability .