40G/100G Optical Transceivers
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QSFP to SFP Adapter
Introduction and Applications of QSFP28 Optical Modules
Time: 2020-02-23
• Overview
With the advancement of technology, requirements for the transmission rate of optical fiber communications have been rising steadily. Currently, 100G optical modules are being deployed across a variety of scenarios. 100G optical modules come in multiple form factors, including CFP, CFP2, CFP4, CXP and QSFP28. Among these different form factors, QSFP28 optical modules have emerged as the mainstream form factor for 100G optical modules, thanks to their advantages of compact size, high port density and cost-effectiveness. They are widely favored by enterprises, carriers and data centers.
• Classification and Applications of QSFP28 Optical Modules
1. QSFP28 SR4 Optical Module
The QSFP28 SR4 optical module complies with the IEEE 802.3bm standard for 100G Ethernet. It features 4 independent transmit and receive channels, with each channel supporting a data rate of 25G, delivering an aggregate bandwidth of 100G. Operating at a central wavelength of 850nm and adopting an MPO interface, it can transmit data up to 70m over OM3 multimode fiber and 100m over OM4 multimode fiber, making it ideal for short-reach transmission scenarios. Due to these characteristics, QSFP28 SR4 optical modules are predominantly used in data centers for switch-to-switch cabling within a 100m distance over multimode fibers.
2. QSFP28 LR4 Optical Module
The QSFP28 LR4 optical module is compliant with the IEEE 802.3ba standard for 100G Ethernet. Unlike the QSFP28 SR4, it adopts Wavelength Division Multiplexing (WDM) technology, which multiplexes optical signals of different wavelengths from 4 channels onto a single fiber for transmission. The central wavelengths of the 4 LAN WDM channels are 1295.56nm, 1300.05nm, 1304.58nm and 1309.14nm respectively. Equipped with dual LC interfaces, this module supports a transmission distance of up to 10km over single-mode fiber. Suited for medium-to-long reach transmission applications, it is widely deployed in large-scale data centers and enterprise campuses.
Figure 1: Moduletek’s QSFP28-SR4 and QSFP28-LR4 Optical Modules
3. QSFP28 PSM4 Optical Module
Similar to the QSFP28 SR4, the QSFP28 PSM4 optical module provides 4 independent transmit and receive channels and utilizes an MPO interface. However, it operates at a central wavelength of 1310nm and is designed for use with single-mode fiber, supporting a maximum transmission distance of 2km. It should be noted that to minimize reflections caused by MPO connections, Moduletek’s QSFP28 PSM4 optical module employs MPO receptacles with 8-degree angled endfaces. This product must be used with female MPO connectors featuring 8-degree angled endfaces.
4. QSFP28 CWDM4 Optical Module
The QSFP28 CWDM4 optical module is similar to the QSFP28 LR4 in that it uses WDM technology to convert 4 electrical data input channels of 25Gb/s into 4 CWDM optical signals, which are then multiplexed into a single channel to achieve 100Gb/s optical transmission. Similarly, at the receiving end, the module demultiplexes the incoming 100Gb/s optical signal into 4 CWDM channel signals and converts them back into 4-channel electrical output signals. The central wavelengths of the 4 channels are 1271nm, 1291nm, 1311nm and 1331nm respectively. With an LC interface, it can transmit data up to 2km over single-mode fiber.
5. QSFP28 ER4 Lite Optical Module
The QSFP28 ER4 Lite optical module complies with the IEEE 802.3bm standard for 100G Ethernet. It works on a similar principle to the QSFP28 LR4 optical module, converting 4 electrical signals of 25Gb/s into 4 optical signals with LAN-WDM wavelengths, which are then coupled into a single fiber via an internal multiplexer (MUX) to realize 100Gb/s optical signal transmission. The key difference is that the QSFP28 ER4 Lite optical module uses an APD (Avalanche Photodiode) receiver, making it suitable for long-reach transmission applications. If the host device supports FEC (Forward Error Correction) functionality, the QSFP28 ER4 Lite can achieve a maximum transmission distance of 40km over single-mode fiber; if the host device does not support FEC, the maximum transmission distance is 30km.
Moduletek offers all the QSFP28 optical modules covered in this application guide. Welcome to contact us for inquiries and purchases.
If you have any questions about the above content, please contact us via email: sales@moduletek.com
