40G QSFP BIDI vs 40G QSFP SR4 vs 40G QSFP UNIV: What Is the Difference?

Posted on Oct 20, 2023 by

40G optical modules provide reliable and efficient solutions for modern high-performance networks, offering advantages such as high data rates, high density, flexible transmission distances, and compatibility. In the context of 40G short-distance transmission, three commonly used modules are 40GBASE-SR4, 40GBASE-BiDi, and 40GBASE-UNIV. So, what are their differences, and how should you choose? This article will provide answers to these questions.

What Is 40G QSFP BIDI SR Optical Transceiver Module

The 40GBASE-BiDi SR (Bidirectional Short Reach) module is a type of 40G optical transceiver that utilizes a single pair of multimode fibers for bidirectional transmission. The 40G QSFP BIDI SR optical module uses two 20G channels to achieve 40G transmission. With the use of WDM (Wavelength Division Multiplexing) technology, each channel of the transceiver can simultaneously send and receive light signals of different wavelengths (typically 850nm and 900nm) over multimode fibers. The QSFP-40G-SR-BD optical module, used for short-distance data transmission, can achieve a transmission distance of up to 100 meters when paired with OM3 fiber patch cords and up to 150 meters when paired with OM4 fiber patch cords.

The 40G QSFP BIDI SR optical module maximizes the utilization of existing duplex LC patch cords in the 10G cabling system, enabling a quick deployment of a 40G network. Compared to other traditional solutions, upgrading to a 40G network using the QSFP-40G-SR-BD optical module is more convenient and efficient.

40G QSFP BIDI vs 40G QSFP SR4 vs 40G QSFP UNIV: What Is the Difference

What Is 40G QSFP SR4 Optical Transceiver Module

The 40GBASE-SR4 module is specifically designed for short-range data center applications. It utilizes four parallel optical channels to achieve a data rate of 40Gbps. Each channel operates at 10Gbps, resulting in a combined data rate of 40Gbps. The 40GBASE-SR4 module supports a transmission distance of up to 100 meters using OM3 fibers and up to 150 meters using OM4 fibers.

The module is typically equipped with an MTP/MPO connector, allowing for easy and efficient connectivity with high-density cabling systems. The MTP/MPO connector consolidates multiple fibers into a single connector, simplifying cable management. With its high-bandwidth connectivity, the module enables faster data transfers and enhances performance in data-intensive applications.

40G QSFP BIDI vs 40G QSFP SR4 vs 40G QSFP UNIV, How to Choose

What Is 40G QSFP UNIV Optical Transceiver Module

The 40GBASE-UNIV module is an optical module designed for 40G networks, offering versatility and flexibility. It operates at four different wavelengths: 1270nm, 1290nm, 1310nm, and 1330nm. It features four transmit and receive channels, with a transmission rate of 10Gbps per channel. During operation, the 40G UNIV module combines the four transmitted optical signals through an internal multiplexer to form a single 40Gbps optical signal, which is then transmitted over duplex LC fiber patch cords.

Unlike the 40G QSFP SR4 and 40G QSFP BIDI SR modules, the 40G QSFP UNIV module can be used with both single-mode and multimode fibers. This eliminates the need to replace network equipment when transitioning between single-mode and multimode fibers. The transmission distance for OM3 multimode fibers is up to 150 meters. For single-mode fibers, the transmission distance ranges from 500 meters to 2 kilometers.

40G QSFP BIDI vs 40G QSFP SR4 vs 40G QSFP UNIV: What Is the Difference

Difference between 40G BIDI, 40G SR4, and 40G UNIV

40G BiDi SR, 40G SR4, and 40G UNIV modules are all 40G optical transceiver modules, but they have some key differences in terms of their compatibility, transmission modes, and fiber types:

Transceiver Module
40G SR4
Whether 4 x 10G links are supported
Duplex LC
Duplex LC
Cable Type
1270nm,1290nm, 1310nm,1330nm
Transmission Distance

10G Upgrade to 40G: How to Choose

When upgrading the 10G cabling structure to 40G, you can choose the appropriate 40G module based on the following factors:

  • Transmission distance requirements: First, consider the transmission distance that needs to be covered. If your requirement is data transmission over short distances, typically within 100 meters, then 40G SR4 modules may be a suitable choice. It is suitable for multimode fiber and can be used with existing OM3 or OM4 multimode fiber.

  • Single-mode fiber compatibility: If your upgrade plans include using single-mode fiber, the 40G BiDi SR module may be an option. It can be used with single-mode fiber and provides two-way communication. This module uses duplex LC jumpers for connections.

  • Versatility and flexibility: If you want more flexibility during the upgrade process to adapt to different transmission modes and distance needs, then 40G UNIV modules may be a good choice. It has multiple operating wavelengths and channels and can adapt to different fiber types and transmission requirements.


40G QSFP BIDI SR and 40G QSFP UNIV optical modules can be upgraded from 10G to 40G without changing the existing 10G cabling infrastructure, with a high degree of flexibility and simplicity. 40G QSFP SR4 optical modules are widely used in 40G to 10G network transmission of 8-core MTP-LC optical fiber jumpers. FS.COM provides a large number of 40G optical modules to meet your needs.

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