What is the speed of QSFP56 DD？

The speed of QSFP56 DD (Quad Small Form-factor Pluggable Double Density) is 400 Gigabits per second (Gbps).

Walsun's 400G QSFP56-DD transceivers are addressing the technical challenges of achieving high speed 400G interconnections. The transceivers have four optical lanes that operate at 100Gbps PAM4 modulation, providing solutions up to 400 Gbps. The transceivers have on the electrical side 8 lanes of 53.125Gbps PAM4. They are compliant with the QSFP-DD MSA (DD = Double Density). Digital diagnostics functions are available via the I2C interface, as specified by CMIS (Common Management Interface Specification).

QSFP-DD 400G Walsun’s EOLD-134HG-5H-M QSFP-DD DR4, 4x100G Optical transceiver module are designed for use in 400 Gigabit links over 500m singlemode fiber. They are operating on 1310nm wavelength, and are compliant with the QSFP-DD MSA. Digital diagnostics functions are available via the I2C interface, as specified by the QSFP-DD MSA.

QSFP-DD 400G Walsun’s EOLD-164HG-02 QSFP-DD FR4, 4x100G Optical transceiver module are designed for use in 400 Gigabit links over 2km singlemode fiber. They are operating on CWDM4 wavelength, and are compliant with the QSFP-DD MSA. Digital diagnostics functions are available via the I2C interface, as specified by the QSFP-DD MSA.

QSFP-DD 400G Walsun’s EOLD-164HG-10 QSFP-DD LR4, 4x100G Optical transceiver module are designed for use in 400 Gigabit links over 10km singlemode fiber. They are operating on CWDM4 wavelength, and are compliant with the QSFP-DD MSA. Digital diagnostics functions are available via the I2C interface, as specified by the QSFP-DD MSA.

QSFP-DD 400G Walsun’s EOLD-854HG-E-02-MO QSFP-DD SR8, 8x50G Optical transceiver module are designed for use in 400 Gigabit links over 100m multimode fiber. They are compliant with the QSFP-DD MSA. Digital diagnostics functions are available via the I2C interface, as specified by the QSFP-DD MSA.

QSFP-DD 400G Walsun’s EOLD-BI854HG-E-02-MXX QSFP-DD 400G SR4.2, 8x50G Optical transceiver module are designed for use in 400 Gigabit links over 150m multimode fiber using 850/910nm wavelength. They are compliant with the QSFP-DD MSA. Digital diagnostics functions are available via the I2C interface, as specified by the QSFP-DD MSA.

QSFP56 vs QSFP28 vs QSFP+

Seen from their industry names, QSFP56, QSFP28 and QSFP+ are very similar in that they share the same QSFP form factor as their postfix shows, and they have the same size as each other. However, their data center and connectivity capabilities are different. Below is a table listing the basic parameters of QSFP56, QSFP28, and QSFP+.

Industry name	Year	original meaning	Number of Electric Lanes	Number of Optical Lanes	Bit Rate/Lane	Modulation	Line Rates
QSFP+	2013	Quad Small Form-factor Pluggable Plus	4	4	10Gbps	NRZ	40G
QSFP28	2016	Quad Small Form-factor Pluggable 28	4	4	25Gbps	NRZ	100G
QSFP56	2017	Quad 50 Gigabits Small Form-factor Pluggable	4	4	50Gbps	PAM4	200G

From the comparison chart, it can be distinctly seen that compared with QSFP+ and QSFP28, the QSFP56 form factor performs a higher network speed as 200G QSFP supporting 4×50G channels. While QSFP+ is an evolution of QSFP to support 4×10G channels carrying 10G Ethernet, 10G fiber channel or QDR InfiniBand. It introduced the concept of multiplexing four lanes to increase the bandwidth, capable of handling 40Gbps line rates at 10GBaud NRZ per lane. QSFP28 supports 4×25G channels and contains 4-lane optical transmitter and 4-lane optical receiver as QSFP+ does.

The most significant change from QSFP+ and QSFP28 to QSFP56 is that QSFP56 made the change from NRZ encoding to PAM4 encoding. Though QSFP56 still uses 4 lanes as QSFP28, the modulation is doubled to 50G per channel, which enables more data on existing fiber, accordingly, more suitable for hyper-scale data center networks.