The rapid development in optical communication industry is driving massive demand, for higher bandwidth and faster data rate, from 10G to 40G and 100G, will this keep going on? The answer is definitely “Yes”. In recent years, migration from 10G to 40G or 25G to 100G has been a hot spot among data center managers. While recently, QSFP-DD solutions and components are coming. We know that the QSFP-DD is similar to the current QSFP, but what’s the difference between them? In this article, the comparison between QSFP-DD and QSFP will be explored.
1.What are QSFP-DD and QSFP?
QSFP-DD module: QSFP-DD refers to Quad Small Form Factor Pluggable Double Density. It uses eight 25G lanes via NRZ modulation or eight 50G lanes via PAM4 modulation, which can support optical link of 200 Gbps or 400 Gbps aggregate. In addition, QSFP-DD module can enable up to 14.4 Tbps aggregate bandwidth in a single switch slot. As it is backwards compatible with QSFP modules, QSFP-DD provides flexibility for end users and system designers.
The Quad Small Form-factor Pluggable (QSFP) is a compact, hot-pluggable transceiver used for data communications applications. The form factor and electrical interface are specified by a multi-source agreement (MSA) under the auspices of the Small Form Factor Committee. It interfaces networking hardware (such as servers and switches) to a fiber optic cable or active or passive electrical copper connection. It is an industry format jointly developed and supported by many network component vendors, allowing data rates from 4×1 Gb/s for QSFP and 4×10 Gbit/s for QSFP+ and to the highest rate of 4×28 Gbit/s known as QSFP28 used for 100 Gbit/s links.
2.QSFP-DD vs QSFP
The QSFP-DD is similar to the current QSFP. But there are many differences between the current QSFP.
From the above picture, we can see that QSFP-DD is smaller than QSFP in packaging. The reason why the new transceiver is called “double density” is related to the current 100G QSFP28 transceivers. The “double density” means the doubling of the number of high-speed electrical interfaces that the module supports when comparing to regular QSFP28 module. In terms of transmission data rate, the QSFP-DD is capable of operating 25 Gb/s NRZ modulation or 50 Gb/s PAM4 modulation over 16 pairs of twinaxial conductors or optical fibers to support 200 Gb/s or 400 Gb/s aggregate bandwidth while QSFP supports data rates from 4×1 Gb/s, 4×10 Gbit/s and to the highest rate of 4×28 Gbit/s known as QSFP28 used for 100 Gbit/s links. Systems designed with QSFP-DD connectors will be backwards compatible to support interoperability with existing QSFP modules, however, the QSFP-DD connector will only support 200 Gb/s or 400 Gb/s aggregate speeds when mated with QSFP-DD modules.
3.200G QSFP-DD
The road map of QSFP-DD is drawing our attention. It is predicted that QSFP-DD will become a useful family of modules for the industry with application at greater than 400G. As a global optical interconnection innovator, Gigalight has released QSFP-DD 2x100GBASE-SR4 in the middle of the year.It integrates eight data lanes in each direction with 8×25.78125Gbps bandwidth. Each lane can operate at 25.78125Gbps up to 70 m using OM3 fiber or 100 m using OM4 fiber.This module incorporates Gigalight Technologies proven circuit and VCSEL technology to provide reliable long life, high performance, and consistent service.
Conclusion:
At present, QSFP-DD is superior than QSFP no matter in appearance or product performance. With the development of big data and clouding computing, more and more higher performance products will come out in the near future. No matter QSFP-DD or QSFP, you can always choose the one that best suits your network demands.
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