GIGATECH PRODUCTS GUIDE TO QSFP-DD INTEROPERABILITY

As traffic demands continue to push networks to their limits, 400G capable solutions are ideal for high volume hyperscale and enterprise networks, telco providers, and large data centers.  400G technology holds the potential to deliver the power, efficiency, and density essential for supporting 5G networks, emerging applications like augmented and virtual reality, Artificial Intelligence, as well as 4k video streaming. 400G QSFP-DD transceivers provide the optimal combination of size, speed, and flexibility for growing and expanding networks.

Features & Benefits

  • Next-Gen Bandwidth

    QSFP-DD extends the use and usability of the QSFP family of modules to support higher speeds of 200G, 400G, and 800G .

  • Breakout Capability

    Certain QSFP-DD modules possess the ability to connect with multiple 100G modules in breakout mode, increasing port density for 100G interfaces and facilitating the migration to 400G platforms.

  • Backward compatibility

    QSFP-DD port is backward compatible with QSFP+, QSFP28 and QSFP56 modules

QSFP-DD stands for Quad Small Form Factor Double Density. QSFP-DD is a high-speed, high-density, hot-pluggable optical transceiver module used in data communication applications. QSFP-DD is an evolution of the QSFP (Quad Small Form Factor Pluggable) standard, designed to support higher data rates of 200G, 400G, 800G, and even 1.6TB. Double Density signifies that a QSFP-DD module supports twice the number of high-speed electrical connections compared to the older QSFP28 generation while maintaining the same physical size and form factor. In order to achieve higher bandwidth over 100G, a newer form of channel modulation called PAM4 was incorporated to replace the existing NRZ method used up to QSFP28.

Compliance
QSFP-DD MSA
IEEE 802.3
OIF 56G PAM4
100G Lambda MSA

400G QSFP-DD Models

400GBase-SR8

The QSFP-DD SR8 is a short-range transceiver for use over parallel multimode fiber.  Utilizing 8 optical pairs of 850nm, each optical pair operates at 50Gb/s PAM4, resulting in a total of 16 fibers (8x Tx and 8x Rx).  This transceiver can be used to connect to single 400G, 2x 200G, 4x 100G, or 8x 50G applications.

Data Rate Wavelength Max Distance Connector Modulation
400Gbps
850nm
100m
MTP/MPO-16 MMF APC
8x 50G PAM4

Select Breakout Options Below

QSFP-DD SR8

MTP/MPO-16 400G Link

QSFP-DD SR8

Direct Connection between QSFP-DD SR8 Transceivers for 400G Connectivity

QSFP-DD SR8

MTP/MPO-16 400G to 2x 200G MTP-12 Breakout

QSFP56 SR4

The QSFP-DD SR8 Transceiver Supports 2x 200G-SR4 Breakout Capability

QSFP-DD SR8

MTP/MPO-16 200G to 2x 100G MTP-12 Breakout

QSFP28 SR4

The QSFP-DD SR8 Transceiver Supports 2x 100G-SR4 Breakout Capability

QSFP-DD SR8

MTP/MPO-16 400G to 8x 50G LC Duplex Breakout

50G SFP56

The QSFP-DD SR8 Transceiver Supports up to 8x 50G-SR Breakout Capability

QSFP-DD SR8

MTP/MPO-16 200G to 8x 25G LC Duplex Breakout

25G SFP28

The QSFP-DD SR8 Transceiver Supports up to 8x 25G-SR Breakout Capability

400GBase-SR4.2

The QSFP-DD SR4.2 is a short-range transceiver for use over parallel multimode fiber.  Utilizing 4 optical pairs of 855nm/908nm, each optical channel operates at 50Gb/s PAM4, resulting in a total of 8 fiber (4x Tx and 4x Rx).  This transceiver can be used to connect to single 400G or 4x 100G 1.2 applications.

Data Rate Wavelength Max Distance Connector Modulation
400Gbps
855/908nm
150m
MTP/MPO-12 MMF UPC
8x 50G PAM4

Select Breakout Options Below

400G SR BD

MTP/MPO 400G Link

400G SR BD

The GigaTech Products QSFP-DD SR BD transceiver will operate with a QSFP-DD SR BD for 400G connectivity.

400G SR BD

MPO to LC Breakout 4x 100G Link

100G SR BD

The GigaTech Products QSFP-DD SR BD transceiver will operate with 4x QSFP28 SR BD in a 4x 100G breakout mode.

400GBase-DR4

The QSFP-DD DR4 transceiver is used for transmission up to 500m over parallel singlemode fiber.  Utilizing 4 optical pairs of 1310nm, each optical channel operates at 50Gb/s PAM4, resulting in a total of 8 fiber (4x Tx and 4x Rx).  This transceiver can be used to connect to single 400G or 4x 100G applications.

Data Rate Wavelength Max Distance Connector Modulation
400Gbps
1310nm
500m
MTP/MPO-12 SMF APC
8x 50G PAM4

Select Breakout Options Below

QSFP-DD DR4

MTP/MPO-12 APC 400G Link

QSFP-DD DR4

Direct Connection between QSFP-DD DR4 Transceivers for 400G Connectivity

QSFP-DD DR4

MTP/MPO-12 400G to 4x 100G LC Duplex Breakout

100G QSFP28

The QSFP-DD DR4 can breakout to 4x 100GBASE-DR, 100G-FR, & 100G-LR QSFP28 up to 500m

4x 100GBase-FR (XDR4)

The QSFP-DD FR transceiver is used for transmission up to 2km over parallel singlemode fiber.  Utilizing 4 optical pairs of 1310nm, each optical channel operates at 50Gb/s PAM4, resulting in a total of 8 fiber (4x Tx and 4x Rx).  This transceiver can be used to connect to single 400G or 4x 100G applications.

Data Rate Wavelength Max Distance Connector Modulation
400Gbps
1310nm
2km
MTP/MPO-12 SMF APC
8x 50G PAM4

Select Breakout Options Below

QSFP-DD FR

MTP/MPO-12 SMF APC 400G Link

QSFP-DD FR

Direct Connection between QSFP-DD FR Transceivers for 400G Connectivity

QSFP-DD FR

MTP/MPO-12 SMF APC 400G to 4x 100G LC Duplex Breakout

100G QSFP28

The QSFP-DD FR can breakout to 4x 100GBASE-FR (up to 2KM), 100G-DR (up to 500M), & 100G-LR (up to 2KM) QSFP28 

4x 100GBase-LR (PLR4)

The QSFP-DD LR transceiver is used for transmission up to 10km over parallel singlemode fiber.  Utilizing 4 optical pairs of 1310nm, each optical channel operates at 50Gb/s PAM4, resulting in a total of 8 fiber (4x Tx and 4x Rx).  This transceiver can be used to connect to single 400G or 4x 100G applications.

Data Rate Wavelength Max Distance Connector Modulation
400Gbps
1310nm
10km
MTP/MPO-12 SMF APC
8x 50G PAM4

Select Breakout Options Below

QSFP-DD LR

MTP/MPO-12 SMF APC 400G Link

QSFP-DD LR

Direct Connection between QSFP-DD LR Transceivers for 400G Connectivity

QSFP-DD LR

MTP/MPO-12 SMF APC 400G to 4x 100G LC Duplex Breakout

100G QSFP28

The QSFP-DD LR can breakout to 4x 100G-LR (up to 10KM), 100G-DR (up to 500M), & 100G-FR (up to 2KM) QSFP28

400GBase-FR4

The QSFP-DD FR4 transceiver is used for transmission up to 2km over duplex singlemode fiber.  Utilizing 4 CWDM pairs, each optical channel operates at 50Gb/s PAM4, resulting in a total of 2 fiber (1x Tx and 1x Rx).  This transceiver can only be used to connect to a single 400G application.

Data Rate Wavelength Max Distance Connector Modulation
400Gbps
1271 / 1291 / 1311 / 1311nm
2km
LC Duplex
8x 50G PAM4

QSFP-DD FR4

LC Duplex 400G Link

QSFP-DD FR4

Direct Connection between QSFP-DD FR4 Transceivers for 400G Connectivity

400GBase-LR4

The QSFP-DD LR4 transceiver is used for transmission up to 10km over duplex singlemode fiber.  Utilizing 4 CWDM pairs, each optical channel operates at 50Gb/s PAM4, resulting in a total of 2 fiber (1x Tx and 1x Rx).  This transceiver can only be used to connect to a single 400G application.

Data Rate Wavelength Max Distance Connector Modulation
400Gbps
1271 / 1291 / 1311 / 1311nm
10km
LC Duplex
8x 50G PAM4

QSFP-DD LR4

LC Duplex 400G Link

QSFP-DD LR4

Direct Connection between QSFP-DD LR4 Transceivers for 400G Connectivity

200G QSFP-DD Models

200GBase-2SR4

The QSFP-DD 2SR4 is a short-range transceiver for use over parallel multimode fiber.  Utilizing 8 optical pairs of 850nm, each optical pair operates at 25Gb/s NRZ, resulting in a total of 16 fibers (8x Tx and 8x Rx) used with an MPO-24 connector.  This transceiver can be used to connect to single 200G, or 2x 100G applications.

Data Rate Wavelength Max Distance Connector Modulation
200Gbps
850nm
100m
MTP/MPO-24 MMF APC
8x 25G NRZ

Select Breakout Options Below

QSFP-DD 2SR4

MTP/MPO-24 MMF UPC 200G Link

QSFP-DD 2SR4

Direct Connection between QSFP-DD 2SR4 Transceivers for 200G Connectivity

QSFP-DD 2SR4

MTP/MPO-24 MMF UPC 200G to 2x 100G MTP-12 Breakout

QSFP28 SR4

The QSFP-DD 2SR4 Transceiver Supports 2x 100G-SR4 Breakout Capability

200GBase-2CWD4

The QSFP-DD 2CWD4 transceiver is used for transmission up to 2km over dual duplex singlemode fiber.  Utilizing dual 4 CWDM pairs, each optical channel operates at 25Gb/s NRZ, resulting in a total of 2 fiber (1x Tx and 1x Rx) per CS duplex connector.  This transceiver can be used to connect to a single 200G, or 2x 100G applications.

Data Rate Wavelength Max Distance Connector Modulation
200Gbps
1271nm, 1291nm, 1311nm, 1311nm
2KM
Dual Duplex CS SMF PC/UPC
8x 25G NRZ

Select Breakout Options Below

QSFP-DD 2CWD4

Dual Duplex CS SMF PC/UPC 200G Link

QSFP-DD 2CWD4

Direct Connection between QSFP-DD 2CWD4 Transceivers for 200G Connectivity

QSFP-DD 2CWD4

Dual Duplex CS SMF PC/UPC to 2x LC SM Duplex

QSFP28 CWDM4

The QSFP-DD 2CWD4 Transceiver Supports 2x 100G-CWDM4 Breakout Capability

200GBase-2LR4

The QSFP-DD 2LR4 transceiver is used for transmission up to 10km over dual duplex singlemode fiber.  Utilizing dual 4 LWDM pairs, each optical channel operates at 25Gb/s NRZ, resulting in a total of 2 fiber (1x Tx and 1x Rx) per CS duplex connector.  This transceiver can be used to connect to a single 200G, or 2x 100G applications.

Data Rate Wavelength Max Distance Connector Modulation
200Gbps
1295.56nm, 1300.05nm, 1304.58nm, 1309.14nm
10KM
Dual Duplex CS SMF PC/UPC
8x 25G NRZ

Select Breakout Options Below

QSFP-DD 2LR4

Dual Duplex CS SMF PC/UPC 200G Link

QSFP-DD 2LR4

Direct Connection between QSFP-DD 2LR4 Transceivers for 200G Connectivity

QSFP-DD 2LR4

Dual Duplex CS SMF PC/UPC to 2x LC SM Duplex

QSFP28 LR4

The QSFP-DD 2LR4 Transceiver Supports 2x 100G-LR4 Breakout Capability

Optical Channel Modulation

Initial optical transceivers utilized NRZ (Non-Return-To-Zero) modulation for transmitting electrical signals.  NRZ is highly stable and was used to create the QSFP+ 40G and QSFP28 100G optical transceivers.  These speeds were achieved by using four parallel electrical lanes, each lane running at 10Gbps (QSFP+ 40G) to 25Gbps (QSFP28 100G) with NRZ encoding. As requirements for increased bandwidth grew, there was a need for a new type of modulation.  PAM4 (Pulse Amplitude Modulation 4 Levels) was introduced with the new QSFP56 and QSFP-DD form factors to handle increased speeds of 200G, 400G, and 800G transceivers.  PAM4 is a significant breakthrough in technology, utilizing more channels at higher rates, with 1600G in development as the next QSFP-DD evolution.

NRZ Modulation

NRZ (Non-Return to Zero) is a digital line coding scheme used in telecommunications.  In NRZ, binary data values are directly represented by distinct signal levels:

Binary 1: Represented by a specific signal level (often a positive voltage).

Binary 0: Represented by a different signal level (often a negative voltage).

The key point is that the signal level does not return to zero between transmitting consecutive bits of the same value.

Imagine a classic light switch, on or off. That’s essentially NRZ, using two voltage levels to represent data: high for 1 and low for 0. Simple, reliable, and widely used for lower data rates under 100G.

NRZ incorporated 1G, 10G, and up to 25G per lane speeds, but was not suited for higher levels of data due to the simplicity of design.

Eye Diagram for NRZ data

PAM-4 Modulation

PAM4 (Pulse Amplitude Modulation, 4 Levels) is a multi-level signaling technique used in high-speed data communication.

Instead of representing bits with just two distinct levels (high and low) like in NRZ, PAM4 uses four distinct voltage levels allowing it to transmit two bits of information per symbol.

00: Lowest voltage level

01: Second lowest voltage level

10: Second highest voltage level

11: Highest voltage level

Think of this as a dimmer switch with multiple levels vs NRZ method of “on & off”. This doubles the bandwidth compared to NRZ, perfect for transmitting more data at the same speed of modulation.

PAM4 in QSFP-DD utilizes up to 8 electrical lanes over the 4 optical channels.  Broken down in speeds of 50Gb/s, 100Gb/s, and soon 200Gb/s to achieve speeds of 400G, 800G, and soon to be 1.6TB collectively.

Eye Diagram for PAM4 data

QSFP-DD Frequently Asked Questions

Are QSFP-DD Ports Backwards Compatible?

Yes, QSFP-DD Ports are backwards compatible, accepting QSFP112, QSFP56, QSFP28, & QSFP+ transceivers. Each are the same form factor size. Please note that this does not work the opposite direction however, a QSFP-DD will not work in a lower speed port such as QSFP28.

Why is it called Double Density when it is capable of much larger speed than QSFP28?

Double Density refers to the doubling of the number of high-speed electrical interfaces that the module supports compared to QSFP28.  The connector specification supports PAM4 electrical modulation format up to 8 electrical lanes, allowing speeds of 400G and greater.

Are QSFP-DD able to connect with other form factors?

Yes.  QSFP-DD can be paired with equivalent media type of OSFP (Octal Small Form Factor Pluggable) directly.  It is also possible for QSFP-DD to link to lower speeds such as QSFP28, and even SFP types via breakout cable.

Can you plug an OSFP module into a QSFP-DD port, or a QSFP-DD module into an OSFP port?

No. The OSFP and the QSFP-DD are two physically distinct form factors. If you have an OSFP system, then OSFP optics and cables must be used. If you have a QSFP-DD system, then QSFP-DD optics and cables must be used.