分类目录归档:Optical Transceiver Solution

400ZR: Enable 400G for Next-Generation DCI

To cope with large-scale cloud services and other growing data center storage and processing needs, the data center systems have become increasingly decentralized and difficult to manage. And applications like artificial intelligence (AI) urgently need low-latency, high-bandwidth network architectures to support the large number of machine-to-machine input/output (I/O) generated between servers. To ensure the basic performance of these applications, the maximum fiber propagation between these distributed data centers must be limited to about 100 km. Therefore, these data centers must be connected in distributed clusters. In order to ensure high-bandwidth and high-density data center interconnection at the same time, 400G ZR came into being. In this post, we will reveal what 400ZR is, how it works and the influences it brings about.

What Is 400ZR?

400ZR, or 400G ZR, is a standard that will enable the transmission of multiple 400GE payloads over Data Center Interconnect (DCI) links up to 80 km using dense wavelength division multiplexing (DWDM) and higher-order modulation. It aims to ensure an affordable and long-term implementation based on single-carrier 400G using dual-polarization 16 QAM (16-state quadrature amplitude modulation) at approximately 60 gigabaud (Gbaud). Developed by Optical Interconnect Forum (OIF), the 400ZR project is essential to facilitate the reduction of the cost and complexity of high-bandwidth data center interconnects and to promote interoperability among optical module manufacturers.

400G ZR

Figure 1: 400G ZR Transceiver in DCI Switch or Router

How Does 400ZR Work?

400G ZR proposes a technology-driven solution for high-capacity data transmission, which could be matched with the 400GE switch port. It uses a unique design of advanced coherent optical technology for small, pluggable form factor modules. Although the product form factor is not specified in the IA (implementation agreement), the companies or groups contributing to the 400ZR have defined this specification to fit the solution. These form factors defined separately by Multi-Source Agreement (MSA) bodies specify compact mechanical transceivers like QSFP-DD and OSFP, which are connectorized and pluggable into a compatible socket in a system platform. That is to say, the compatible 400ZR solutions that come to market will also be interoperable since the OIF and form factor MSAs are industry-wide organizations. And the interoperability of the 400ZR solutions offers the dual benefit of simplified supply chain management and deployment.

400ZR+ for Longer-reach Optical Transmission

Like other 400G transceivers, the pluggable coherent 400ZR solution can support 400G Ethernet interconnection and multi-vendor interoperability. However, it is not suitable for next-generation metro-regional networks that need transmission over 80 km with a line capacity of 400 Gb/s. Under such circumstances, 400ZR+, or 400G ZR+ is proposed. The 400ZR+ is expected to further enhance modularity by supporting multiple different channel capacities based on coverage requirements and compatibility with installed metro optical infrastructure. With 400ZR+, both the transmission distance and line capacity could be assured.

What Influences Will 400ZR Bring About?

Although 400ZR technology is still in its infancy, once it is rolled out, it will have a significant impact on many industries as the following three: hyper-scale data centers, distributed campuses & metropolitan areas and telecommunications providers.

400ZR Helps Cloud and Hyperscale Data Centers Adapt to the Growing Demand for Higher Bandwidth

The development of DCI and 400ZR could help cloud and hyper-scale data centers adapt to the growing demand for higher bandwidth on the network. They could deal with the exponential growth of applications such as cloud services, IoT devices, and streaming video. As time goes by, 400G ZR will contribute more to the ever-growing applications and users for the whole networking.

400ZR Will Support Interconnects in Distributed Data Centers

As is mentioned above, 400ZR technology will support the necessary high-bandwidth interconnects to connect distributed data centers. With this connection, distributed data centers can communicate with each other, share data, balance workloads, provide backup, and expand data center capacity when needed.

400ZR Allows Telecommunications Companies to Backhaul Residential Traffic

400G ZR standard will allow telecommunications companies to backhaul residential traffic. When running at 200 Gb/s using 64 Gbaud signalings and QPSK modulation, 400ZR can increase the range of high loss spans. For 5G networks, 400G ZR provides mobile backhaul by aggregating multiple 25 Gb/s streams. 400ZR helps promote emerging 5G applications and markets.

400ZR+/400ZR- Will Provide Greater Convenience Based on 400ZR

In addition to the interoperable 400G mode, the 400ZR transceiver is also expected to support other modes to increase the range of addressable applications. These modes are called 400ZR + and 400ZR-. “+” indicates that the power consumption of the module exceeds the 15W required by IA and some pluggable devices, enabling the module to use more powerful signal processing technology to transmit over distances of hundreds of kilometers. “-” indicates that the module supports low-speed modes, such as 300G, 200G, and 100G, which provide network operators with more flexibility.

Will 400ZR Stay Popular In the Next Few Years?

According to the data source below from LightCounting, 400ZR will lead the growth of optical module sales in 2021-2024. The figure below shows the shipment data of high-speed (100G and above) and low-speed (10G and below) DWDM modules sold on the market. It is clear that modules used in Cloud or DCI have an increasing tendency in 2021-2024. That means 400ZR will lead annual growth from 2021.

Source

In addition, with the first 100Gbps SerDes implementation in switching chips expected in 2021, the necessary data rate will move to 800 Gbps within the next 1-2 years for the optics interface. Since the OSFP form factor has been defined to allow an 8x 100GE interface without changing the definition of the transceiver. Similarly, in parallel, the coherent optics on the line side will transition to support 128GBaud 16QAM within a similar time frame, making it easy to migrate from the current 400ZR to the next-generation 800ZR. Therefore, 400ZR is crucial no matter in the current or the future network development.

Article Source

https://community.fs.com/blog/400zr-enable-400g-for-next-generation-dci.html

Related Articles

https://community.fs.com/blog/400g-qsfp-dd-transceiver-types-overview.html

https://community.fs.com/blog/400g-osfp-transceiver-types-overview.html

400G QSFP Transceiver Types and Fiber Connections

400G QSFP has become one of the most popular form factors in the next-generation network. And different types of modules have appeared in the 400G optical transceiver market. What are 400G QSFP-DD transceiver types? What fiber cables could be used with these 400G optical modules? What about the answers to frequently asked questions about 400G QSFP? This post will illustrate them thoroughly.

400G QSFP Transceiver Types

400G QSFP transceivers are introduced respectively in the following table according to the two transmission types (over multimode fiber and single-mode fiber) they support.

Transmission TypeQSFP-DD Product DescriptionReachOptical ConnectorWavelengthOptical ModulationProtocol
Multimode fiber400G QSFP-DD SR8up to 100m over OM4 or OM5
up to 70m over OM3
MTP-16/MPO-16850nm50G PAM4IEEE P802.3cIEEE 802.3cd
Single-mode fiber400G QSFP-DD DR4up to 500m over parallel SMFMTP-12/MPO-121310nm100G PAM4IEEE 802.3bs
400G QSFP-DD XDR4/DR4+up to 2km over parallel SMFMTP-12/MPO-121310nm100G PAM4/
400G QSFP-DD FR4up to 2km over duplex SMFLCCWDM4 wavelength100G PAM4100Glambda MSA
400G QSFP-DD 2FR4up to 2km over duplex SMFCSCWDM4 wavelength50G PAM4IEEE 802.3bs
400G QSFP-DD LR4up to 10km over duplex SMFLCCWDM4 wavelength100G PAM4100Glambda MSA
400G QSFP-DD LR8up to 10km over duplex SMFLCCWDM4 wavelength50G PAM4IEEE 802.3bs
400G QSFP-DD ER8up to 40km over duplex SMFLC1310nm50G PAM4IEEE 802.3cn

Fiber Connections for 400G QSFP Transceivers

QSFP 400G SR8

  • A QSFP-DD SR8 can interop with another QSFP-DD SR8 over an MTP-16/MPO-16 cable. This is the most popular connection using an MTP-16/MPO-16 cable to connect two QSFP-DD SR8 transceivers directly.
  • 400G QSFP-DD SR8 breaks out to 2× 200G SR4.
  • QSFP-DD SR8 interops with 8× 50G SR over MPO-16 to 8× LC duplex fiber cables.

QSFP 400G DR4

  • QSFP-DD DR4 interops with QSFP-DD DR4 over an MPO-12 trunk cable.
    • 400G QSFP-DD DR4 interops with 4× 100G DR over MPO-12 to 4× LC duplex breakout cable.
    QSFP-DD DR4 to 4x 100G Breakout Connection

    QSFP 400G XDR4/DR4+

    • QSFP-DD XDR4/DR4+ interops with QSFP-DD XDR4/DR4+ over an MPO-12 trunk cable.
      • 400G QSFP-DD XDR4 interops with 4× 100G FR modules over an MPO-12 to 4× Duplex LC cable.

      QSFP 400G FR4

      QSFP-DD FR4 interops with QSFP-DD FR4 over a duplex LC cable.

      QSFP-DD FR4 Connection

      QSFP 400G 2FR4

      QSFP-DD 2FR4 interops with 2× 200G FR4 over 2× CS to 2× LC duplex cable.

      QSFP-DD 2FR4 Connection

      QSFP 400G LR4

      QSFP-DD LR4 interops with QSFP-DD LR4 over an LC duplex cable.

      QSFP-DD LR4 Connection

      QSFP 400G LR8

      QSFP-DD LR8 interops with QSFP-DD LR8 over an LC duplex cable.

      QSFP-DD LR8 Connection

      QSFP 400G ER8

      QSFP-DD ER8 interops with QSFP-DD ER8 over an LC duplex cable.

      QSFP-DD ER8 Connection

      400G QSFP Transceivers: Q&A

      Q: What does “SR8”, “DR4”, “XDR4”, “FR4”, “LR4”, and “LR8” mean in QSFP 400G modules?

      A: “SR” refers to short-range, and “8” implies there are 8 optical channels. “DR” refers to 500m reach using single-mode fiber, and “4” implies there are 4 optical channels. “XDR4” is short for “eXtended reach DR4”. And “LR” refers to 10km reach using single-mode fiber.

      Q: Can I plug a QSFP-DD transceiver module into an OSFP port?

      A: No. QSFP-DD and OSFP are totally different form factors. For more information about OSFP transceivers, you can refer to the 400G OSFP Transceiver Types Overview. You can use only one kind of form factor in the corresponding system. Eg, if you have a QSFP 400G system, QSFP-DD transceivers and cables must be used.

      Q: Can I plug a 100G QSFP28 module into a 400G QSFP port?

      A: Yes. A QSFP28 module can be inserted into a QSFP-DD port (without a mechanical adapter). When using a QSFP28 module in a QSFP-DD port, the QSFP-DD port must be configured for a data rate of 100G instead of 400G.

      Q: What other breakout options are possible apart from using the 400G QSFP-DD modules mentioned above?

      A: 400G QSFP-DD DACs & AOCs are possible for breakout 400G connections. See 400G Direct Attach Cables (DAC & AOC) Overview for more information about 400G DACs & AOCs.

      Article Source:

      https://community.fs.com/blog/400g-qsfp-dd-transceiver-types-overview.html

      Related Articles:

      https://community.fs.com/blog/optical-transceiver-market-200g-400g.html

      https://community.fs.com/news/400g-qsfp-dd-solution-for-400g-data-center-interconnect.html

      How Much Do You Know About QSFP56?

      Over the past years, there have emerged various optical module form factor types with the growth of new technology and high-speed interconnects, among which QSFP56, as a member of the QSFP family, is a solution for 200G applications. What‘s the difference between QSFP56 with other QSFP family form factors? Is QSFP56 the same as QSFP56-DD? If you are wondering about these questions, this article is for you.

      Figure 1: Transceiver form factor

      QSFP56—Form Factor of 200G Transceivers

      To make clear what QSFP56 is, let’s take a look at the QSFP form factor first. Quad Small Form-Factor Pluggable (QSFP) was developed after SFP, which was originally designed to replace the single-channel SFPs with high-density optical modules. Due to the fact that it denotes four lanes for up to 4 wavelengths, it provides higher bandwidth capacity compared with the SFP modules.

      Developed on the basis of QSFP, 40G QSFP+ arose and then 100G QSFP28 came into use for high-density applications. With the rising of data traffic in data centers and advanced network applications, the market is urgent to achieve higher-speed general availability. There is more addition to QSFP family form factors, such as 200G QSFP56 and 400G QSFP56-DD.

      Figure 2:Types of QSFP form factor

      As an evolution of the previous 40G QSFP+ and 100G QSFP28, Quad 50 Gigabits Small Form-factor Pluggable (QSFP56) is the one designed for 200G Ethernet. QSFP56 denotes 4 x 50 to 56Gb/s in a QSFP form factor. Sometimes it can also be referred to as 200G QSFP for sake of simplicity. QSFP56 optical modules are similar to QSFP ones in terms of size and form factor. Classified by distance, QSFP56 modules can be divided into QSFP56 CR, SR, DR, FR, LR, which enables different transmission distances over a single mode fiber (SMF) or multimode fiber (MMF).

      Generally, two QSFP56 modules can be used with an SMF or MMF to realize a 200G link. QSFP56 AOC/DAC is also a way to realize a 200G link by connecting QSFP56 ports on two devices in a simplified linking process. For bridging 200G QSFP56 ports with other speeds, there are 200G QSFP56 to 2x100G QSFP28 breakout cables and 200G QSFP56 to 4x50G SFP56 breakout cables to achieve 2x100G or 4x50G connections.

      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 nameYearoriginal meaningNumber of Electric LanesNumber of Optical LanesBit Rate/LaneModulationLine Rates
      QSFP+2013Quad Small Form-factor Pluggable Plus4410GbpsNRZ40G
      QSFP282016Quad Small Form-factor Pluggable 284425GbpsNRZ100G
      QSFP562017Quad 50 Gigabits Small Form-factor Pluggable4450GbpsPAM4200G

      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.

      Shift from QSFP56 to QSFP56-DD (400G QSFP-DD)

      With data centers undergoing rapid growth, the rising demand for data volume is pushing network components to support higher bandwidth and higher density. The latest iteration of optical module form factor is from QSFP56 to QSFP56-DD, which is also called 400G QSFP-DD. DD here refers to double density, representing reaching 400G (with 50G PAM4) by doubling data lanes of QSFP56, from 4 lanes to 8 lanes.

      Though QSFP56-DD has the double density, its size is similar to QSFP56. 400G QSFP56-DD port is backward compatible with the QSFP transceiver which means as long as the switch supports, QSFP56 can work on the QSFP56-DD port. When using a QSFP56 module in an QSFP56-DD port, this port will be configured for a data rate of 200G, instead of 400G.

      The QSFP56-DD form factor is now recognized by the 400G market as the 400G form factor that gets the most concern. Despite that nowadays 400G Ethernet is seen as a futureproofing solution for the next-generation data center, there is still a need for 200G QSFP56 for some organizations deploying 200G Ethernet.

      Article Source

      https://community.fs.com/blog/introduction-to-qsfp56-form-factor.html

      Related Articles

      https://community.fs.com/blog/differences-between-qsfp-dd-and-qsfp-qsfp28-qsfp56-osfp-cfp8-cobo.html

      https://community.fs.com/blog/400g-qsfp-dd-transceiver-types-overview.html

      400G Transceiver Test – How Does It Ensure the Quality of Optical Modules?

      400G

      Higher bandwidth requirements are enhancing the need for 400G optical modules in the large data center interconnections. And a series of tests is significant to ensure the high quality of the 400G transceivers. This article will introduce the 400G transceiver test from three aspects: challenges, key items, and opportunities.

      Challenges of 400G Transceiver Test

      The electrical interfaces of 400G transceivers use either 16× 28Gb/s with NRZ (non-return to zero) modulation or the newer 4 or 8× 56Gb/s with PAM4 (4-level pulse amplitude) modulation. Higher speeds and the utilization of PAM4 do bring great improvements but also result in high complexity at the physical layer, causing signal transmission errors easily and bringing challenges for optical module vendors.

      High Complexity at the Physical Layer

      On the physical appearance layer, the high-speed interfaces of 400G optical modules include more electrical input/output interfaces, optical input/output interfaces, and other power and low-speed management interfaces. And all the performance of these interfaces should be made to a complaint of 400G standards. As the size of 400G transceivers is similar to the existing 100G transceivers, the integration of those interfaces needs more sophisticated manufacturing technology.

      Signal Transmission Errors

      The higher lane speed in 400G electrical interfaces means more noise (also called signal-to-noise ratio) in signal transmission, causing an increased bit error rate (BER), which in turn affects the signal quality. Therefore, corresponding performance tests should be taken to ensure the quality of 400G modules.

      Development & Manufacturing Test Costs

      The complex 400G transceiver test also brings new challenges for the optical module vendors. To ensure the transceiver quality for users, vendors have to attach great importance to the transceiver test equipment and R&D technical. They should ensure that the new products can support 400G upgrade while dampening associated development and manufacturing test costs that may hamper competitive pricing models.

      Key Items in 400G Transceiver Test

      For transceiver vendors, product quality testing is fundamental to building reliable connections with customers. Let’s have a look at the key items in the 400G transceiver test. For more detailed information, please visit the 400G QSFP-DD Transceivers Test Program.

      ER Performance and Optical Power Level Tests

      ER (extinction ratio), the optical power logarithms ratio when the laser outputs the high level and low level after electric signals are modulated to optical signals, is an important and the most difficult indicator to measure the performance of 400G optical transceivers. The ER test can show whether a laser works at the best bias point and within the optimal modulation efficiency range. OMA (outer optical modulation amplitude) can measure the power differences when the transceiver laser turns on and off, testing 400G transceivers’ performance in another aspect. Both the ER and the average power can be measured by mainstream optical oscilloscopes.

      Optical Spectrum Test

      The optical spectrum test is mainly divided into three parts: center wavelength, side mode suppression ratio (SMSR), and spectrum width of the 400G transceivers. All of these three parameters are essential for keeping a high-quality transmission and performance of the modules. The larger the value of the side mode suppression ratio, the better the performance of the laser of the module. Watch the following video to see how FS tests the optical spectrum for 400G QSFP-DD transceivers.https://www.youtube.com/embed/xMwbi85Hlig?rel=0&showinfo=0&enablejsapi=1&origin=https%3A%2F%2Fcommunity.fs.com

      Forwarding Performance Tests

      400G transceiver has a more complicated integration compared with the existing QSFP28 and QSFP+ modules, which puts higher requirements for the test of its forwarding performance. RFC 2544 defines the following baseline performance test indicator for networks and devices: throughput, delay, and packet loss rate. In this test procedure, the electrical and optical interfaces will be tested and make sure the signal quality they transmitted and received will not get distortion.

      Eye Diagram Test

      Different from the single eye diagram of NRZ modulation in 100G optical transceivers, the PAM4 eye diagram has three eyes. And PAM4 doubles the bit bearing efficiency compared with NRZ, but it still has noise, linearity, and sensitivity problems. IEEE proposes using PRBS13Q to test the PAM4 optical eye diagram. The main test indicators are eye height and width. By checking the eye height and width in the test result, users can tell if the signal linearity quality of the 400G transceiver is good or not.

      Comparison of waveforms and eye diagrams between NRZ and PAM4 signals.png

      The following video shows how FS tests 400G QSFP-DD-SR8 transceivers’ eye pattern with Anritsu MP2110A All-in-One BERT and Sampling Oscilloscope to ensure the QSFP-DD transceivers’ signal quality.https://www.youtube.com/embed/DlfMLDy6VmY?rel=0&showinfo=0&enablejsapi=1&origin=https%3A%2F%2Fcommunity.fs.com

      Jitter Test

      The jitter test is mainly designed for the output jitter of transmitters and jitter tolerance of receivers. The jitter includes random jitter and deterministic jitter. Because deterministic jitter is predictable when compared to random jitter, you can design your transmitter and receiver to eliminate it. In a real test environment, the jitter test is operated together with the eye diagram test to check the 400G transmitter and receiver performance.

      Bit Error Rate Test in Real Working Condition

      In this testing procedure, 400G optical transceivers will be plugged into the 400G switches to test their working performance, BER, and error tolerance ability in a real environment. As mentioned above, the higher BER in 400G optical transceiver lanes leads to transmission problems in most 400G links. Therefore, FEC (forward error correction) technology is applied to improve signal transmission quality. FEC provides a way to send and receive data in extremely noisy signaling environments, making error-free data transmissions in 400G link as possible. How FS tests the BER of 400G QSFP-DD modules is displayed in the following video to ensure the stability and reliability of the transmission.https://www.youtube.com/embed/KJ7eWECtZ54?rel=0&showinfo=0&enablejsapi=1&origin=https%3A%2F%2Fcommunity.fs.com

      Temperature Test

      Each 400G transceiver module comes with a vendor-defined operating temperature range. If the temperature exceeds or beyond the normal temperature range, then the modules will fail to perform well or even won’t operate normally, and even lead to delays or network breakdowns. So the temperature test is also essential for the transmission performance of transceivers. This is to guarantee the reliability of these high-speed 400G transceivers used within the high-speed communication network and data centers. The video below shows how FS tests its 400G QSFP-DD modules at different temperatures.https://www.youtube.com/embed/CgwfapEcU2o?rel=0&showinfo=0&enablejsapi=1&origin=https%3A%2F%2Fcommunity.fs.com

      Opportunities in 400G Transceiver Test

      Driven by 5G, artificial intelligence (AI), virtual reality (VR), Internet of Things (IoT), and autonomous vehicles, though multiple technical transceiver test issues are needed to be resolved, the booming trend of the 400G Ethernet market cannot stop. Lots of manufacturers and test solution providers have promoted their own 400G product solutions to the market. Under this situation, for some smaller optical module vendors, the 400G transceiver test is one of the key points they should consider, because how to improve the quality of the 400G products and supply speed will determine how much profit they get from the 400G market. Know more about What’s the Current and Future Trend of 400G Ethernet? to prepare for the coming fast-speed era.

      Original Source: 400G Transceiver Test – How Does It Ensure the Quality of Optical Modules?

      Differences Between QSFP-DD and QSFP+ / QSFP28 / QSFP56 / OSFP / CFP8 / COBO

      QSFP-DD, as the smallest form factor for 400G transceivers, offers industry’s highest bandwidth density while leveraging the backward compatibility to lower-speed QSFP pluggable modules and cables, making it popular among the fiber optic manufacturers. As the newest hot type of optical transceivers in 400G high-speed applications, QSFP-DD is often compared with other modules such as QSFP56, OSFP, CFP8, and COBO. So what are the differences among these optical modules? This post will illustrate them thoroughly.

      QSFP-DD Wiki

      QSFP-DD (also called QSFP56-DD) stands for Quad Small Form Factor Pluggable Double Density, which is fully compliant with IEEE802.3bs and QSFP-DD MSA standards. The “double density” means the doubling of the number of high-speed electrical interfaces that the module supports compared with a standard QSFP28 module. The data rate of each channel can reach 25Gb/s through NRZ modulation technology, realizing 200G network transmission. Also, the data rate of each channel can reach 50Gb/s by the PAM4 modulation technology, achieving 400G network transmission, which is suitable for high-performance computing data center and cloud network. For more information about PAM4 modulation technology, please visit: PAM4: Learn 400G Ethernet From Here.

      The advantages of QSFP-DD form factor are as follows:

      • Backward compatibility: allowing the QSFP-DD to support existing QSFP modules (such as QSFP+, QSFP28, QSFP56, etc.) and provide flexibility for end-users and system designers.
      • Adopting the 2×1 stacked integrated cage/connector to support the one-high cage connector and two-high stack cage connector system.
      • SMT connector and 1xN cage design: this kind of design can enable thermal support of at least 12W per module. The higher thermal reduces the requirement for heat dissipation capabilities of transceivers, thus reducing some unnecessary costs.
      • ASIC design: supporting multiple interface rates and fully backward compatible with QSFP+ and QSFP28 modules, thus reducing port and equipment deployment costs.

      QSFP-DD vs QSFP+/QSFP28/QSFP56

      QSFP-DD, QSFP+, QSFP28 and QSFP56 belong to the QSFP form factor, but what are the differences among them? The differences are explained in the following descriptions.

      Structure

      In terms of the appearance, the width, length and thickness of the QSFP-DD are the same as QSFP+, QSFP28 and QSFP56. But the QSFP-DD module is equipped with an 8-lane electrical interface rather than a 4-lane like other QSFP modules and the ASIC ports of QSFP-DD are doubled to support existing interfaces such as CAUI-4. Therefore, the mechanical interface of QSFP-DD on the host board is slightly deeper than that of the other QSFP system transceivers to accommodate the extra row of contacts.

      Bandwidth & Application

      The QSFP-DD modules can support 400Gbps while QSFP+/QSFP28/QSFP56 can only reach 40Gbps/100Gbps/200Gbps respectively. Therefore, QSFP-DD connectors are used in 400G optical modules, DACs and AOCs, and applied for the 400G data center interconnections. And QSFP+/QSFP28/QSFP56 modules and DAC/AOC are used for 40G/100G/200G networks. interconnection.

      Backward Compatibility

      As mentioned above, the QSFP-DD can be backward compatible with the previous QSFP system transceiver modules. In other words, based on the previous form factor, the QSFP-DD has been technically upgraded to support increased bandwidth. And its backward compatibility can avoid existing equipment replacement on the scale and effectively reduce the network upgrade cost.

      Form FactorQSFP-DDQSFP56QSFP28QSFP+
      Released Year2016201820162010
      Number of Electrical Interface Lanes8444
      Single Channel Rate25Gbps/50Gbps50Gbps25Gbps10Gbps
      Modulation TechnologyNRZ/PAM4PAM4NRZNRZ
      Backward CompatibilityQSFP+/QSFP28/QSFP56QSFP+/QSFP28QSFP+/

      QSFP-DD vs OSFP/CFP8/COBO

      QSFP-DD (QSFP56-DD) and OSFP/CFP8/COBO are the form factors of 400G optics on the market, the differences of them are listed below:

      QSFP-DD vs OSFP

      OSFP is a new pluggable form factor with eight high speed electrical lanes that will initially support 400Gb/s (8x50G) or reach up to 800Gb/s. The width, length and thickness of QSFP-DD are 18.35mm, 89.4mm and 8.5mm, while those of OSFP are 22.58mm, 107.8mm and 13.0mm. It is obvious that the OSFP form factor is slightly wider and deeper than the QSFP-DD, but it still supports 36 OSFP ports per 1U front panel, enabling 14.4Tb/s per 1U.

      Generally, the power consumption of QSFP-DD is 7-12W, while the OSFP can reach 12-15W. The lower the power consumption, the better the performance of the transceiver. Unlike the QSFP-DD, OSFP can’t be backward compatible with QSFP+/QSFP28 since it has a larger size than that of QSFP+/QSFP28.

      QSFP-DD vs CFP8

      Featuring a 41.5mm*107.5mm*9.5mm form factor, the CFP8 module delivers four times more bandwidth than existing 100G solutions. Its electrical interface has been generally specified to allow for 16×25 Gb/s and 8×50 Gb/s mode. Since the size of CFP8 is almost three times larger than that of QSFP-DD, the power consumption of CFP8 is much higher than QSFP-DD. Meanwhile, the CFP8 can’t be used on QSFP+/QSFP28 ports. The maximum bandwidth of CFP8 and QSFP-DD is 400Gb/s, but CFP8 only supports in the form of 16x25G or 8x50G while QSFP-DD also supports both 200Gb/s (8x25G).

      QSFP-DD vs COBO

      COBO stands for Consortium for On-Board Optics, it can be installed internally to the line-card equipment in a controlled environment, which lacks flexibility. And it doesn’t support hot-pluggable, so it is more difficult for COBO modules to maintain than QSFP-DD. Additionally, the COBO form factor has two electrical interfaces——one eight lane and the other sixteen lane to meet both 1x400G and 2x400G transmission requirements.

      The following chart shows the market maturity of the QSFP-DD, OSFP, CFP8 and COBO form factors. The larger the numbers, the higher the market maturity of these form factors.

      PerformanceCFP8OSFPQSFP-DDCOBO
      Volume1234
      Power Consumption3214
      Cost1342
      Maturity4321
      Compatibility3241
      Difficulty for Operation & Maintenance2341
      Overall Ratings14151813

      We can see from the table that the overall rating of QSFP-DD and OSFP form factors are higher than other form factors. So the QSFP-DD and OSFP are more popular with fiber optic manufacturers. While the former is suitable for data center applications and the latter often applied for telecommunications applications. For more types of 400G transceivers, please refer to How Many 400G Transceiver Types Are in the Market? for more detailed information.

      Will QSFP-DD Be Popular in 800G Ethernet?

      The QSFP-DD (QSFP56-DD) is more suitable for data center applications than OSFP. With the concentration of east-west traffic in the data center and the increasing pressure on the internal bandwidth of the data center, the time gap between the application of high-speed optical modules in the telecom market and the data center market is gradually shortening. The 400G optics will be applied widely. That is, QSFP-DD will benefit from the 400G Ethernet and ushered in a good development prospect.

      As 400G becomes commercially available on a large scale, single-wave 100G technology is set to mature, laying the groundwork for the arrival of 800G. Recently, the QSFP-DD800 Multi-Source Agreement (MSA) organization released the first version of the QSFP-DD800 transceiver hardware specification, which is dedicated to the continuation of the current QSFP-DD form factor to support a single channel rate of 100Gbps 8-channel new generation QSFP-DD800. This also means that 800G might still adopt the QSFP-DD form factor to bring greater advantages and values for Internet service providers.

      Article Source:

      https://community.fs.com/blog/differences-between-qsfp-dd-and-qsfp-qsfp28-qsfp56-osfp-cfp8-cobo.html

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      https://community.fs.com/blog/400g-ethernet-400g-transceiver.html

      https://community.fs.com/blog/400g-qsfp-dd-transceiver-types-overview.html