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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?

400G ZR & ZR+ – New Generation of Solutions for Longer-reach Optical Communications

400G

400G ZR and ZR+ coherent pluggable optics have become new solutions for high-density networks with data rates from 100G to 400G featuring low power and small space. Let’s see how the latest generation of 400G ZR and 400G ZR+ optics extends the economic benefits to meet the requirements of network operators, maximizes fiber utilization, and reduces the cost of data transport.

400G ZR & ZR+: Definitions

What Is 400G ZR?

400G ZR coherent optical modules are compliant with the OIF-400ZR standard, ensuring industry-wide interoperability. They provide 400Gbps of optical bandwidth over a single optical wavelength using DWDM (dense wavelength division multiplexing) and higher-order modulation such as 16 QAM. Implemented predominantly in the QSFP-DD form factor, 400G ZR will serve the specific requirement for massively parallel data center interconnect of 400GbE with distances of 80-120km. To learn more about 400G transceivers: How Many 400G Transceiver Types Are in the Market?

Overview of 400G ZR+

ZR+ is a range of coherent pluggable solutions with line capacities up to 400Gbps and reaches well beyond 80km supporting various application requirements. The specific operational and performance requirements of different applications will determine what types of 400G ZR+ coherent plugs will be used in networks. Some applications will take advantage of interoperable, multi-vendor ecosystems defined by standards body or MSA specifications and others will rely on the maximum performance achievable in the constraints of a pluggable module package. Four categories of 400G ZR+ applications will be explained in the following part.

400G ZR & ZR+: Applications

400G ZR – Application Scenario

The arrival of 400G ZR modules has ushered in a new era of DWDM technology marked by open, standards based, and pluggable DWDM optics, enabling true IP-over-DWDM. 400G ZR is often applied for point-to-point DCI (up to 80km), making the task of interconnecting data centers as simple as connecting switches inside a data center (as shown below).

Figure 1: 400G ZR Applied in Single-span DCI

Four Primary Deployment Applications for 400G ZR+

Extended-reach P2P Packet

One definition of ZR+ is a straightforward extension of 400G ZR transcoded mappings of Ethernet with a higher performance FEC to support longer reaches. In this case, 400G ZR+ modules are narrowly defined as supporting a single-carrier 400Gbps optical line rate and transporting 400GbE, 2x 200GbE or 4x 100GbE client signals for point-to-point reaches (up to around 500km). This solution is specifically dedicated to packet transport applications and destined for router platforms.

Multi-span Metro OTN

Another definition of ZR+ is the inclusion of support for OTN, such as client mapping and multiplexing into FlexO interfaces. This coherent pluggable solution is intended to support the additional requirements of OTN networks, carry both Ethernet and OTN clients, and address transport in multi-span ROADM networks. This category of 400G ZR+ is required where demarcation is important to operators, and is destined primarily for multi-span metro ROADM networks.

Figure 2: 400G ZR+ Applied in Multi-span Metro OTN

Multi-span Metro Packet

The third definition of ZR+ is support for extended reach Ethernet or packet transcoded solution that is further optimized for critical performance such as latency. This 400G ZR+ coherent pluggable with high performance FEC and sophisticated coding algorithms supports the longest reach over 1000km multi-span metro packet transport.

Figure 3: 400G ZR+ Applied in Multi-span Metro Packet

Multi-span Metro Regional OTN

The fourth definition of ZR+ supports both Ethernet and OTN clients. This coherent pluggable also leverages high performance FEC and PCS, along with tunable optical filters and amplifiers for maximum reach. It supports a rich feature set of OTN network functions for deployment over both fixed and flex-grid line systems. This category of 400G ZR+ provides solutions with higher performance to address a much wider range of metro/regional packet networking requirements.

400G ZR & ZR+: What Makes Them Suitable for Longer-reach Transmission in Data Center?

Coherent Technology Adopted by 400G ZR & ZR+

Coherent technology uses the three degrees of freedom (amplitude, phase and polarization of light) to focus more data on the wave that is being transmitted. In this way, coherent optics can transport more data over a single fiber for greater distances using higher order modulation techniques, which results in better spectral efficiency. 400G ZR and ZR+ is a leap forward in the application of coherent technology. With higher-order modulation and DWDM unlocking high bandwidth, 400G ZR and ZR+ modules can reduce cost and complexity for high-level data center interconnects.

Importance of 400G ZR & ZR+

400G ZR and 400G ZR+ coherent pluggable optics take implementation challenges to the next level by adding some of the elements for high-performance solutions while pushing component design for low-power, pluggability, and modularity.

Conclusion

Although there are still many challenges to making 400G ZR and 400G ZR+ transceiver modules that fit into the small size and power budget of OSFP or QSFP-DD packages and also achieving interoperation as well the costs and volume targets. With 400Gbps high optical bandwidth and low power consumption, 400G ZR & ZR+ may very well be the new generation in longer-reach optical communications.

Original Source: 400G ZR & ZR+ – New Generation of Solutions for Longer-reach Optical Communications

400G OSFP Transceiver Types Overview

400G

OSFP stands for Octal Small Form-factor Pluggable, which consists of 8 electrical lanes, running at 50Gb/s each, for a total of the bandwidth of 400Gb/s. This post will give an introduction of 400G OSFP transceiver types, the fiber connections, and some QAs about OSFP.

400G OSFP Transceiver Types

Below lists some current main 400G OSFP transceiver types: OSFP SR8, OSFP DR4, OSFP DR4+, OSFP FR4, OSFP 2*FR4, and OSFP LR4, which summarize OSFP transceiver according to the two transmission types (over multimode fiber and single-mode fiber) they support.

Fibers Connections for 400G OSFP Transceivers

400G OSFP SR8

Figure 1 OSFP SR8 to OSFP SR8.jpg
  • 400G OSFP SR8 to 2× 200G SR4 over MTP-16 to 2× MPO-8 breakout cable.
Figure 2 OSFP SR8 to 2 200G SR4.jpg
  • 400G OSFP SR8 to 8× 50G SFP via MTP-16 to 8× LC duplex breakout cable with up to 100m.
Figure 3 OSFP SR8 to 8 50G SFP.jpg

400G OSFP DR4

  • 400G OSFP DR4 to 400G OSFP DR4 over an MTP-12/MPO-12 cable.Figure 1 OSFP SR8 to OSFP SR8.jpg
  • 400G OSFP DR4 to 4× 100G DR4 over MTP-12/MPO-12 to 4× LC duplex breakout cable.
Figure 4 OSFP DR4 to 4 100G DR.jpg

400G OSFP XDR4/DR4+

  • 400G OSFP DR4+ to 400G OSFP DR4+ over an MTP-12/MPO-12 cable.
  • 400G OSFP DR4+ to 4× 100G DR over MTP-12/MPO-12 to 4× LC duplex breakout cable.
Figure 5 OSFP DR4+ to 4 100G DR.jpg

400G OSFP FR4

400G OSFP FR4 to 400G OSFP FR4 over duplex LC cable.

Figure 6 OSFP FR4 to OSFP FR4.jpg

400G OSFP 2FR4

OSFP 2FR4 can break out to 2× 200G and interop with 2× 200G-FR4 QSFP transceivers via 2× CS to 2× LC duplex cable.

400G OSFP Transceivers: Q&A

Q: What does “SR8”, “DR4”, “XDR4”, “FR4”, and “LR4” mean?

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 an OSFP transceiver module into a QSFP-DD port?

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

Q: Can I plug a 100G QSFP28 module into an OSFP port?

A: Yes. A QSFP28 module can be inserted into an OSFP port but with an adapter. When using a QSFP28 module in an OSFP port, the OSFP port must be configured for a data rate of 100G instead of 400G.

Q: What other breakout options are possible apart from using OSFP modules mentioned above?

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

Original Source: 400G OSFP Transceiver Types Overview

What Cable Should I Use for 10G Transceiver Module?

To deploy the optical network, the transceiver module and patch cable are the two basic components. According to the feedbacks of customers from FS.COM, one of the common problems faced by them is what cables they should use for their transceiver modules. To solve this problem, we make this post of patch cable selection guidance. Since the order for 10G transceivers ranks top, we are going to take 10G modules as a reference.

An Overview of 10G Transceiver Module

Transceiver module, also called fiber optic transceiver, is a hot-pluggable device that can both transmit and receive data. By combining a transmitter and receiver into a single module, the device converts electrical signals into optical signals to allow these signals to be efficiently transferred on fiber optic cables. As for the 10G transceiver, it refers to the optical modules with 10G data rate. In FS.COM, there are mainly four types of 10G transceivers: XENPAK, X2, XFP, and SFP+. Even though these optical transceivers are all accessible to the 10G networks, they have different matching patch cables and applications.

10G Transceiver Module

Figure 1: 10G Transceiver Modules

Patch Cable Basics

Apart from optical module, the patch cable is the other vital role in networking. Patch cable, also called patch cord, refers to the copper or optical cable. It’s designed to connect one electronic or optical device to another for signal routing. Conventionally, the patch cable will be terminated with connectors at both ends. For example, the LC fiber cable refers to the optical cable fixed with LC connector. Typically, there are LC, SC, ST, FC and MTP/MPO fiber patch cables. According to different features, we can get various classifications of patch cables, such as fiber types, polishing types, etc.

Patch Cables

Figure 2: Patch Cables

Factors to Consider When Choosing Patch Cable for 10G Transceiver Module

Recently, most of the 10G transceiver modules are compatible with different brands and support higher data rates. It will be much easier to choose optical modules for your networking than selecting mating patch cables. Based on most applications, there are three major factors that can be taken into consideration: transmission media, transmission distance, and transceiver module interface.

Transmission Media

Classified by transmission media, two types of patch cables can be found in the market: optic fiber cable and copper cable. Correspondingly, there are two kinds of optical transceivers available: copper-based transceivers and fiber optic based transceivers. Copper transceiver modules like 10GBASE-T SFP+, they have an RJ45 interface, connecting with copper cables. Typically, Ethernet cables that support 10G copper-based transceivers are Cat7 and Cat6a cables.

As for the 10G optical modules, they can support higher data rates over optic fiber cables. It will be more complicated to choose fiber cables. Generally, there are multimode fibers and single mode fibers. Based on the specified needs for transmission distance, the answer will be varied.

Transmission Distance

To select cables, the transmission distance is also an important factor that you need to take care. In the following table, we list the basic information of common 10G transceivers, including their supporting fiber cable types and transmitting distance.

Transceiver Type
Wavelength
Cable Type
Transmission Distance
SR
850 nm
MMF
300 m
LR
1310 nm
SMF
10 km
ER
1550 nm
SMF
40 km
ZR
1550 nm
SMF
80 km

As for fiber cables, single mode fiber is used for long-distance transmission and multimode fiber is for short distance. In a 10G network, the transmission distance of single mode fiber (OS2) can reach from 2 km to 100 km. When it comes to multimode fibers, the transmission distances for OM1, OM2, OM3 are 36 m, 86 m and 300 m. OM4 and OM5 can reach up to 550 m.

Transceiver Module Interface

Another factor you need to consider is the transceiver interface. Usually, transceivers use one port for transmitting and the other port for receiving. They tend to employ duplex SC or LC interface. However, for 10G BiDi transceivers, it only has one port for both transmitting and receiving. Simplex patch cord is applied to connect the 10G BiDi transceiver.

Summary

For your 10G network cabling, transceiver module and patch cable are necessary components. With a wide range of patch cables, selecting the right patch cables will be more complex than 10G transceivers. Generally, three major factors can be considered: transmission media, transmission distance, and transceiver module interface. To apply what you have learned in this post in cabling, you can visit FS.COM for all the transceivers and patch cables at one shop.