What are the SFP-DD form factors?

The SFP-DD (“DoubIe-Density SFP”) are two approaches to achieving the same objective: A compact, SFP-Iike form factor with 2x 50Gb/s PAM-4 eIectricaI Ianes in each direction to enabIe a totaI bandwidth of 100G / port. The basic concept is shown beIow:

The SFP-DD form-factor is defined by the SFP-DD MSA. The SFP-DD adds a second row of contacts to the SFP eIectricaI connector to enabIe a 2x 10G/25G/50G eIectricaI interface. The figure beIow summarizes the approach of the SFP-DD to achieve a duaI-Iane interface.

What is the speed and modulation format of the electrical interface of a 100G SFP-DD module?

SFP-DD modules utilize 2x electrical lanes in each direction (2 transmit lanes and 2 receive lanes), operating at a maximum data rate of 50Gb/s PAM-4, enabling an aggregate bandwidth of 100Gb/s. All SFP-DD copper cables can also be configured at lower speeds, enabling 2x 25G & 2x 10G operation.

Can 10G, 25G and 50G SFPs be used in SFP-DD ports?

Yes. The SFP-DD and DSFP ports can be considered “quad-rate” ports, and support 10G, 25G and 50G SFP optics and cables, as well as 100G SFP-DD / DSFP copper cables. This allows a single platform to support 4 generations of speeds – a unique feature of SFP-DD and DSFP systems.

Can SFP-DDs be used in 10G, 25G or 50G SFP ports?

No. SFP-DDs should only be inserted into SFP-DD ports, and DSFPs should only be inserted into DSFP ports.

What are the benefits of using 100G SFP-DD systems?

100G/port SFP-DD systems are quad-rate systems, enabIing the use of 10G, 25G and 50G SFP optics and cabIes, as weII as 100G SFP-DD cabIes 一 enabIing one system to support 4 generations of speeds and transceivers. Key benefits & appIications incIude:

• Future-proof Top of Rack (TOR) switch to Network Interface Card (NIC) connectivity: 100G SFP-DD
  switch ports can be depIoyed using mature 10G/25G SFP technoIogy today, whiIe being future proof to support 50G SFP and 100G SFP-DD/DSFP moduIes and cabIes.

• Easy connectivity 100G-2 QSFP56 based NICs, or breakout to NICs that use 2x 10G/25G/50G SFP ports

• Increase in bandwidth density by a factor of 4 when compared to 25G/port SFP systems.

What do the terms 100G-2 and 50G-2 mean?

These terms describe the bandwidth of an ethernet link, and the number of lanes used to achieve this bandwidth. Every front panel port of an ethernet switch consists of one or more electrical lanes that transmit and receive ethernet data. For 10G SFP, 25G SFP or 50G SFP ports, a single electrical lane is used (in each direction) and modulated at 10G, 25G or 50G. For SFP-DD and DSFP ports, 2 electrical lanes are used (in each direction) and can be operated at a rate of up to 50Gbs per lane (for a total of 100Gb/s per SFP-DD / DSFP port).

The table below summarizes the terminology used to describe common ethernet speeds used by SFP and SFP- DD/DSFP ports, the number of lanes required to achieve this bandwidth, and some common applications of these interface types:

What are the complete set of ethernet speeds that each SFP-DD / DSFP cable supports?

Each SFP-DD port has a 2-lane electrical interface, which can support a maximum data rate of 50Gb/s per lane, enabling a total bandwidth of 100Gbs per SFP-DD port. Each lane can be operated at lower speed data rates, and since the SFP-DD DACs are passive copper cables, the cable does not impose restrictions on lane speed configuration (except that each lane must be operated at 50Gb/s or lower data rate).

The most common port configurations and applications for each SFP-DD copper cable are summarized below. The column labels “Lane 1” & Lane “2” represent the 2-lane electrical interface of the SFP-DD port. The values in the “Lane” columns refer to the speed configuration of the SFP-DD switch port.

The table below shows GIGALIGHT’s 100G SFP-DD series products.