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?

      FAQs on 400G Transceivers and Cables

      400G transceivers and cables play a vital role in the process of constructing a 400G network system. Then, what is a 400G transceiver? What are the applications of QSFP-DD cables? Find answers here.

      FAQs on 400G Transceivers and Cables Definition and Types

      Q1: What is a 400G transceiver?

      A1: 400G transceivers are optical modules that are mainly used for photoelectric conversion with a transmission rate of 400Gbps. 400G transceivers can be classified into two categories according to the applications: client-side transceivers for interconnections between the metro networks and the optical backbone, and line-side transceivers for transmission distances of 80km or even longer.

      Q2: What are QSFP-DD cables?

      A2: QSFP-DD cables contain two forms: one is a form of high-speed cable with QSFP-DD connectors on either end, transmitting and receiving 400Gbps data over a thin twinax cable or a fiber optic cable, and the other is a form of breakout cable that can split one 400G signal into 2x 200G, 4x 100G, or 8x 50G, enabling interconnection within a rack or between adjacent racks.

      Q3: What are the 400G transceivers packaging forms?

      A3: There are mainly the following six packaging forms of 400G optical modules:

      • QSFP-DD: 400G QSFP-DD (Quad Small Form Factor Pluggable-Double Density) is an expansion of QSFP, adding one row to the original 4-channel interface to 8 channels, running at 50Gb/s each, for a total bandwidth of 400Gb/s.
      • OSFP: OSFP (Octal Small Formfactor Pluggable, Octal means 8) is a new interface standard and is not compatible with the existing photoelectric interface. The size of 400G OSFP modules is slightly larger than that of 400G QSFP-DD.
      • CFP8: CFP8 is an expansion of CFP4, with 8 channels and a correspondingly larger size.
      • COBO: COBO (Consortium for On-Board Optics) means that all optical components are placed on the PCB. COBO is with good heat-dissipation and small-size. However, since it is not hot-swappable, once a module fails, it will be troublesome to repair.
      • CWDM8: CWDM 8 is an extension of CWDM4 with four new center wavelengths (1351/1371/1391/1411 nm). The wavelength range becomes wider and the number of lasers is doubled.
      • CDFP: CDFP was born earlier, and there are three editions of the specification. CD stands for 400 (Roman numerals). With 16 channels, the size of CDFP is relatively large.

      Q4: What 400G transceivers and QSFP-DD cables are available on the market?

      A4: The two tables below show the main types of 400G transceivers and cables on the market:

      400G TransceiversStandardsMax Cable DistanceConnectorMediaTemperature Range
      400G QSFP-DD SR8QSFP-DD MSA Compliant70m OM3/100m OM4MTP/MPO-16MMF0 to 70°C
      400G QSFP-DD DR4QSFP-DD MSA, IEEE 802.3bs500mMTP/MPO-12SMF0 to 70°C
      400G QSFP-DD XDR4/DR4+QSFP-DD MSA2kmMTP/MPO-12SMF0 to 70°C
      400G QSFP-DD FR4QSFP-DD MSA2kmLC DuplexSMF0 to 70°C
      400G QSFP-DD 2FR4QSFP-DD MSA, IEEE 802.3bs2kmCSSMF0 to 70°C
      400G QSFP-DD LR4QSFP-DD MSA Compliant10kmLC DuplexSMF0 to 70°C
      400G QSFP-DD LR8QSFP-DD MSA Compliant10kmLC DuplexSMF0 to 70°C
      400G QSFP-DD ER8QSFP-DD MSA Compliant40kmLC DuplexSMF0 to 70°C
      400G OSFP SR8IEEE P802.3cm; IEEE 802.3cd100mMTP/MPO-16MMF0 to 70°C
      400G OSFP DR4IEEE 802.3bs500mMTP/MPO-12SMF0 to 70°C
      4000G OSFP XDR4/DR4+/2kmMTP/MPO-12SMF0 to 70°C
      400G OSFP FR4100G lambda MSA2kmLC DuplexSMF0 to 70°C
      400G OSFP 2FR4IEEE 802.3bs2kmCSSMF0 to 70°C
      400G OSFP LR4100G lambda MSA10kmLC DuplexSMF0 to 70°C

      

      QSFP-DD CablesCatagoryProduct DescriptionReachTemperature RangePower Consumption
      400G QSFP-DD DACQSFP-DD to QSFP-DD DACwith each 400G QSFP-DD using 8x 50G PAM4 electrical lanesno more than 3m0 to 70°C<1.5W
      400G QSFP-DD Breakout DACQSFP-DD to 2x 200G QSFP56 DACwith each 200G QSFP56 using 4x 50G PAM4 electrical lanesno more than 3m0 to 70°C<0.1W
      QSFP-DD to 4x 100G QSFPs DACwith each 100G QSFPs using 2x 50G PAM4 electrical lanesno more than 3m0 to 70°C<0.1W
      QSFP-DD to 8x 50G SFP56 DACwith each 50G SFP56 using 1x 50G PAM4 electrical laneno more than 3m0 to 80°C<0.1W
      400G QSFP-DD AOCQSFP-DD to QSFP-DD AOCwith each 400G QSFP-DD using 8x 50G PAM4 electrical lanes70m (OM3) or 100m (OM4)0 to 70°C<10W
      400G QSFP-DD Breakout AOCQSFP-DD to 2x 200G QSFP56 AOCwith each 200G QSFP56 using 4X 50G PAM4 electrical lane70m (OM3) or 100m (OM4)0 to 70°C/
      QSFP-DD to 8x 50G SFP56 AOCwith each 50G SFP56 using 1x 50G PAM4 electrical lane70m (OM3) or 100m (OM4)0 to 70°C/
      400G OSFP DACOSFP to OSFP DACwith each 400G OSFP using 8x 50G PAM4 electrical lanesno more than 3m0 to 70°C<0.5W
      400G OSFP Breakout DACOSFP to 2x 200G QSFP56 DACwith each 200G QSFP56 using 4x 50G PAM4 electrical lanesno more than 3m0 to 70°C/
      OSFP to 4x100G QSFPs DACwith each 100G QSFPs using 2x 50G PAM4 electrical lanesno more than 3m0 to 70°C/
      OSFP to 8x 50G SFP56 DACwith each 50G SFP56 using 1x 50G PAM4 electrical laneno more than 3m//
      400G OSFP AOCOSFP to OSFP AOCwith each 400G OSFP using 8x 50G PAM4 electrical lanes70m (OM3) or 100m (OM4)0 to 70°C<9.5W

      

      Q5: What do the suffixes “SR8, DR4 / XDR4, FR4 / LR4 and 2FR4” mean in 400G transceivers?

      A5: The letters refer to reach, and the number refers to the number of optical channels:

      • SR8: SR refers to 100m over MMF. Each of the 8 optical channels from an SR8 module is carried on separate fibers, resulting in a total of 16 fibers (8 Tx and 8 Rx).
      • DR4 / XDR4: DR / XDR refer to 500m / 2km over SMF. Each of the 4 optical channels is carried on separate fibers, resulting in a total of 4 pairs of fibers.
      • FR4 / LR4: FR4 / LR4 refer to 2km / 10km over SMF. All 4 optical channels from an FR4 / LR4 are multiplexed onto one fiber pair, resulting in a total of 2 fibers (1 Tx and 1 Rx).
      • 2FR4: 2FR4 refers to 2 x 200G-FR4 links with 2km over SMF. Each of the 200G FR4 links has 4 optical channels, multiplexed onto one fiber pair (1 Tx and 1 Rx per 200G link). A 2FR4 has 2 of these links, resulting in a total of 4 fibers, and a total of 8 optical channels.

      FAQs on 400G Transceivers and Cables Applications

      Q1: What are the benefits of moving to 400G technology?

      A1: 400G technology can increase the throughput of data and maximize the bandwidth and port density of the data centers. With only 1/4 the number of optical fiber links, connectors, and patch panels when using 100G platforms for the same aggregate bandwidth, 400G optics can also reduce operating expenses. With these benefits, 400G transceivers and QSFP-DD cables can provide ideal solutions for data centers and high-performance computing environments.

      Q2: What are the applications of QSFP-DD cables?

      A2: QSFP-DD cables are mainly used for short-distance 400G Ethernet connectivity in the data centers, and 400G to 2x 200G / 4x 100G / 8x 50G Ethernet applications.

      Q3: 400G QSFP-DD vs 400G OSFP/CFP8: What are the differences?

      A3: The table below includes detailed comparisons for the three main form factors of 400G transceivers.

      400G Transceiver400G QSFP-DD400G OSFPCFP8
      Application ScenarioData centerData center & telecomTelecom
      Size18.35mm× 89.4mm× 8.5mm22.58mm× 107.8mm× 13mm40mm× 102mm× 9.5mm
      Max Power Consumption12W15W24W
      Backward Compatibility with QSFP28YesThrough adapterNo
      Electrical signaling (Gbps)8× 50G
      Switch Port Density (1RU)363616
      Media TypeMMF & SMF
      Hot PluggableYes
      Thermal ManagementIndirectDirectIndirect
      Support 800GNoYesNo

      

      For more details about the differences, please refer to the blog: Differences Between QSFP-DD and QSFP+/QSFP28/QSFP56/OSFP/CFP8/COBO

      Q4: What does it mean when an electrical or optical channel is PAM4 or NRZ in 400G transceivers?

      A4: NRZ is a modulation technique that has two voltage levels to represent logic 0 and logic 1. PAM4 uses four voltage levels to represent four combinations of two bits logic-11, 10, 01, and 00. PAM4 signal can transmit twice faster than the traditional NRZ signal.

      When a signal is referred to as “25G NRZ”, it means the signal is carrying data at 25 Gbps with NRZ modulation. When a signal is referred to as “50G PAM4”, or “100G PAM4”, it means the signal is carrying data at 50 Gbps, or 100 Gbps, respectively, using PAM4 modulation. The electrical connector interface of 400G transceivers is always 8x 50Gb/s PAM4 (for a total of 400Gb/s).

      FAQs on Using 400G Transceivers and Cables in Data Centers

      Q1: Can I plug an OSFP module into a 400G QSFP-DD port, or a QSFP-DD module into an OSFP port?

      A1: No. OSFP and QSFP-DD are two physically distinct form factors. If you have an OSFP system, then 400G OSFP optics must be used. If you have a QSFP-DD system, then 400G QSFP-DD optics must be used.

      Q2: Can a QSFP module be plugged into a 400G QSFP-DD port?

      A2: Yes. A QSFP (40G or 100G) module can be inserted into a QSFP-DD port as QSFP-DD is backward compatible with QSFP modules. When using a QSFP module in a 400G QSFP-DD port, the QSFP-DD port must be configured for a data rate of 100G (or 40G).

      Q3: Is it possible with a 400G OSFP on one end of a 400G link, and a 400G QSFP-DD on the other end?

      A3: Yes. OSFP and QSFP-DD describe the physical form factors of the modules. As long as the Ethernet media types are the same (i.e. both ends of the link are 400G-DR4, or 400G-FR4 etc.), 400G OSFP and 400G QSFP-DD modules will interoperate with each other.

      Q4: How can I break out a 400G port and connect to 100G QSFP ports on existing platforms?

      A4: There are several ways to break out a 400G port to 100G QSFP ports:

      • QSFP-DD-DR4 to 4x 100G-QSFP-DR over 500m SMF
      400G to 4x 100G
      • QSFP-DD-XDR4 to 4x 100G-QSFP-FR over 2km SMF
      400G to 4x 100G
      • QSFP-DD-LR4 to 4x 100G-QSFP-LR over 10km SMF
      400G to 4x 100G
      • OSFP-400G-2FR4 to 2x QSFP-100G-CWDM4 over 2km SMF
      400G to 4x 100G

      Apart from the 400G transceivers mentioned above, 400G to 4x 100G breakout cables can also be used.

      Article Source: FAQs on 400G Transceivers and Cables

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      400G Transceiver, DAC, or AOC: How to Choose?

      400G OSFP Transceiver Types Overview

      Infographic – Types of 400G Transceivers

      With the tremendous requirement for high bandwidth in 5G, loT and cloud data center, the focus on 400G Ethernet has been lasting for several years. As the key hardware devices for optical network interconnection, 400G transceivers have also become the mainstream of the industry. The following is a brief introduction to the types of 400G transceivers.

      Infographic Source

      https://community.fs.com/blog/infographic-types-of-400g-transceivers.html

      Related Articles:

      https://community.fs.com/blog/400g-transceiver-dac-or-aoc-how-to-choose.html
      https://community.fs.com/blog/faqs-on-400g-transceivers-and-cables.html