Despite the rapid development of 100G and 400G technologies, 40G QSFP+ optical modules are still the mainstream choice for small and medium-sized data center upgrades due to their high cost-effectiveness and mature ecosystem. Faced with the two major technical routes of QSFP-40G-SR-BD (short-distance bidirectional) and QSFP-40G-LR4-S ( medium- distance single-mode), how to accurately match the needs? This article will deeply analyze these two optical modules to help you choose the most suitable data center upgrade solution.

一、Basic information about the two optical modules

1. QSFP-40G-SR-BD

The transmission wavelength of QSFP-40G-SR-BD optical module is 850nm and 900nm, with two 20Gbps optical signal transceiver channels. Each signal channel can transmit and receive different transmission wavelengths simultaneously through a multimode optical fiber. It can be stably transmitted in a multimode optical fiber system. The transmission distance using OM3 fiber patch cord is 100m, and the transmission distance using OM4 fiber patch cord is 150m. This optical module can make full use of the duplex LC patch cord in the existing 10G wiring system to quickly build a 40G network without adding a fiber distribution box.

2. QSFP-40G-LR4-S

The QSFP-40G-LR4-S optical module adopts CWDM coarse wavelength division multiplexing technology with four wavelengths of 1271nm, 1291nm, 1311nm, and 1331nm. It is generally used with single-mode fiber jumpers and uses a duplex LC connector. It is suitable for medium and long distance transmission, with a maximum transmission distance of 10km.

二、 Key Parameter Comparison Table

三、Selection Decision Guide

1. Power consumption and heat dissipation design

SR-BD VCSEL laser power consumption is only 43% of LR4-S, making it suitable for high-density switch deployments (such as the NVIDIA Quantum-2 platform).

LR4-S requires additional consideration of laser heat dissipation and optimized airflow design in high temperature environments.

2. Cost and upgrade path

Short- term costs: The price of SR-BD modules is 30% lower, but if new multimode fiber is required, the total cost may exceed that of LR4-S.

Long-term investment: The CWDM wavelength of LR4-S can be directly multiplexed to 100G, which is suitable for planning in the next 3-5 years.

四、ETU-Link 40G QSFP+ S R-BD and LR4-S optical module product information

The QSFP-40G-SR-BD optical module is favored for its short-distance transmission capability and compatibility with existing multimode fiber infrastructure, and is particularly suitable for high-speed connections within data centers. In contrast, the QSFP-40G-LR4-S optical module provides a longer transmission distance and is suitable for scenarios that need to span larger geographical distances, such as interconnection between data centers.

When choosing an optical module, it is recommended that you communicate with a professional supplier to obtain more detailed product information and technical support to ensure the smooth implementation of the upgrade plan. ETU-Link Technology Co., Ltd. is a professional module manufacturer. Here are several of ETU-Link 40G QSFP+ S R-BD and LR4-S optical modules:

Through this, I believe everyone has a clearer understanding of the different characteristics of QSFP-40G-SR-BD and QSFP-40G-LR4-S and their applicable scenarios. If you have any questions about the selection of optical modules or need further technical discussions, please contact us. Let us explore the infinite possibilities of data center technology together!

About ETU-Link

ETU-Link Technology Co., Ltd. was founded in 2014. It is a high-tech enterprise focusing on the research and development, production and sales of optical communication devices. With high-speed optical modules as its core products, the company professionally serves the optical fiber communication markets such as telecommunications, data communications, and storage.