As the core hub of optical communication systems, the rate iteration of optical modules determines the data transmission efficiency and upper limit, supporting the upgrading of industries such as digital economy, AI computing power, and 5G communication. From 1.25G to 800G, the iteration of optical modules is accompanied by innovations in architecture, principles, and performance. This article will focus on three major sections: architecture principles, performance parameters, and selection pitfalls, to provide practitioners with selection references and help with scientific deployment.

Ⅰ.Core Technology Differences: Architectural Design and Core Principle Analysis

The technological differences between 1.25G and 800G optical modules stem primarily from iterative architectural design and breakthroughs in core principles. Modules at different rate levels exhibit distinct differences in channel architecture, modulation principles, and packaging design, directly determining their bandwidth limits and application boundaries. The following section analyzes the architectural design and core principles of each rate module in turn, categorized by rate gradient, to clarify the root causes of these technological differences.

(1)Ultra-high speed band (800G): Silicon photonics integrated architecture, front-end modulation optimization

The ultra-high-speed band (800G) adopts a silicon photonics integrated architecture to improve integration. The mainstream packages are QSFP-DD and OSFP (OSFP supports liquid cooling). Some use 3D packaging and support evolution to 1.6T. The core is based on PAM4 modulation optimization, uses 8×100G parallel channels, and has a bit error rate pre -FEC≤2.4E-4. It is equipped with LPO/CPO technology to reduce power consumption and is suitable for extreme bandwidth scenarios such as AI training and supercomputing.

(2)High-speed band (200G, 400G): Highly integrated multi-channel, optimized modulation principle

High-speed bands (200G, 400G) adopt a high-density multi-channel parallel architecture. 200G uses 4×50G ( QSFP56 package), while the mainstream 400G uses 8×50G (QSFP-DD and OSFP packages). Some 400G uses LPO architecture to reduce power consumption. Both use PAM4 modulation. 400G adds wavelength division multiplexing technology, and LPO is suitable for short-distance high-speed scenarios.

(3)Medium speed range (25G, 40G, 100G): Multi-channel parallel operation, transition of modulation principle

Mid-speed bands (25G, 40G, 100G) are gradually shifting to multi-channel parallel architecture and improved integration. 25G uses SFP28 package for single-channel operation, 40G uses QSFP+ package for 4×10G parallel operation, and 100G uses QSFP28 package for 4×25G parallel operation. In principle, the transition is from NRZ to PAM4. 25G supports dual modulation, 40G continues to use NRZ, and 100G uses NRZ combined with CWDM wavelength division multiplexing to improve fiber utilization when converting from 4x25G to 4x25G. The conversion from 4x25G to 1x100G uses electrical signal NRZ and optical signal PAM4 .

(4)Low-speed band (1.25G, 10G): Single-channel architecture, basic modulation principle

The low-speed band (1.25G, 10G) adopts a single-channel transmission architecture, which is simple in structure, low in integration, and does not require complex heat dissipation. The mainstream package for 1.25G is SFP , and for 10G it is SFP+ . The two packages are similar and partially compatible. The core of both adopts the NRZ modulation principle, which is simple in technology, low in power consumption, and strong in stability, but has a low bandwidth limit. The 10G module adds BIDI single-fiber bidirectional technology to save fiber resources.

Ⅱ.Comprehensive Performance Analysis: Key Parameters and Scenarios Adaptability Comparison

Key Considerations for Selection and Avoiding Common Pitfalls:

① Points for Speed Adaptation: Combine bandwidth requirements, match the architecture with the speed gradient, select the appropriate model as needed, and avoid blindly pursuing high speed and wasting resources.

② Points for Parameter Selection: Pay attention to key parameters such as packaging, transmission distance, and power consumption, and select the appropriate parameter based on the scenario, taking into account both practicality and stability.

③ Points for Risk Mitigation: Avoid blindly pursuing high speeds and fiber optic mismatches. Make precise selections based on the fiber optic network, data center, and equipment conditions to prevent potential risks in advance.

④ Points for Cost Planning: balance cost and performance, select modules according to scenarios, and reserve room for upgrades.