How to Choose QSFP28 Optical Transceiver For 100G Network?

On the migration road of data center from 10G-40G-100G, it’s known that cost-effective 100G optics are in great demand, especially QSFP28 optical transceivers with low cost optical design package tech, widely applied in data center, LAN, WAN, Ethernet switches. However, among these optic fibre modules, which one is the most suitable for our 100G Network? Well, this article will introduce how to choose it.

To some degree, the selection of 100G QSFP28 products depends on transmission distance. Therefore, it would be better to choose it from this perspective. While for different applications, there are different requirements for transmission distance. The below is about its specific conditions and feasible measures:

1. When transmission distance is 100m or under 100m, QSFP28 SR4 is highly recommended. The QSFP28 SR4 supports links of 70 m (OM3) and 100m (OM4) over multimode fiber with MPO connectors. It offers 4 independent transmitting and receiving channels, and each is with 25Gbps able to be aggregated into 100Gbps. Meanwhile, the QSFP28 SR4 optic module is also ideal for the connections from rack to rack in the data center.

2. When transmission distance is over 100m but under 10 km, QSFP28 LR4 is preferred. The QSFP28 LR4 is a fully integrated 4 × 25Gbit/s optical transceiver module, supporting distance up to 10 km. So for long span 100G deployment, such as cabling between two buildings, QSFP28 LR4 with duplex LC and single-mode fiber cable is the perfect option.

3. When transmission distance exceeds 10 km, QSFP28 ER4 is ideal for very long transmission distance. It provides superior performance for 100G Ethernet applications up to 30 km links and converts 4 input channels of 25Gb/s electrical data to 4 channels of LAN WDM optical signals and then multiplexes them into a single channel for 100Gb/s optical transmission.

Of course, the above solutions are just for the different transmission distance. While for the  same transmission distance, how to choose it? Maybe we can get the answer from the example of QSFP28 CWDM4 and QSFP28 PSM4.

QSFP28 CWDM4

QSFP28 PSM4

The CWDM4 provides a 100G Ethernet high-speed link with a maximum transmission distance of 2 km, which interfaces with LC duplex connectors, and uses Mux/Demux technologies with 4 lanes of 25Gbps optically multiplexed into and demultiplexed from duplex single-mode fiber. While PSM4 does not need a MUX/DEMUX for each laser but it does need either a directly modulated DFB laser (DML) or an external modulator for each fiber. Besides, with an MTP interface, PSM4 modules can transmit data at 100Gb/s from point to point over 2 km or can be divided into dual 50Gb/s or quad 25Gb/s links for linking to servers, storage and other subsystems.

It’s seen from that both of QSFP28 CWDM4 and QSFP28 PSM4 are designed to meet the requirement for intermediate or mid-reaches for datacenter applications (500 m to 2 km). And they both use WDM and parallel single mode fiber technologies and support transmission distance up to 2 km.

When faced with such a situation, maybe we can make a decision from the two aspects. For one thing, from the aspect of an inner transceiver module structure, by comparison , PSM4 can be more cost-effective due to its lower component costs. For another thing, from the infrastructure viewpoint, PSM4 would be more expensive when the link distance is long, because PSM4 uses 8 optical single-mode fibers while CWDM uses only 2 optical single-mode fibers.

Above all is about the solutions on choosing a appropriate optical transceiver for 100G network. Believing it will benefit us a lot. If you have other questions or want to know more information about this aspect, welcome to consult us any time, we must provide the most professional information for you in first time.

About us: We are a sub-brand of Gigalight, we focus on high-end optical network devices, mainly supplying industrial-grade optical transceivers and professional optical interconnection components for data centers. With more than 10 years' experience in optics industry, we now have professional R&D team(more than 100 engineers) and stable supply ability.