Counting East and West, Creating Possibilities Together | VIAVI Test Solutions Build a Solid Foundation for Optical Networks

In May 2021, the National Development and Reform Commission issued the “National Integrated Big Data Center Collaborative Innovation System Computing Power Hub Implementation Plan”, proposing to build a new computing power network system integrating data centers, cloud computing, and big data, and laying out the construction of a national integrated computing power hub. The national hub node of the power network, and accelerate the “East Count West Count” project.

On February 17, 2022, the National Development and Reform Commission, the Central Cyberspace Administration of China, the Ministry of Industry and Information Technology, and the National Energy Administration jointly issued a document agreeing to develop new projects in the Beijing-Tianjin-Hebei region, the Yangtze River Delta, the Guangdong-Hong Kong-Macao Greater Bay Area, Chengdu-Chongqing, Inner Mongolia, Guizhou, Gansu, Ningxia and other 8 places have launched the construction of national computing power hub nodes, and plan 10 national data center clusters. So far, the overall layout design of the national integrated big data center system has been completed, and the “Digital from East to Computation from West” project has officially started.

The national plan of “East Counting and West Computing” clarifies the positioning and target scale of hubs in the east and west. The 10 major cluster nodes plan a total of 6 million+ racks, and the number of cluster racks in the west reaches more than 2 million racks. It is estimated that the backbone network bandwidth in the east and west will reach More than 2000T. This will also lead to ultra-high data transmission requirements at multiple levels: data center interconnection (DCN) < 10km, urban data center interconnection (DCI) < 80km, cross-regional data center interconnection 500-1000km or more, and ultra-large Bandwidth, ultra-low latency, and flexible scheduling will also become new challenges for data transmission.

Experts believe that it is expected that the “Digital from the East and Calculate from the West” project will bring a market value of over 100 billion to the data and communication industry chain. For this reason, VIAVI combines its leading advantages in the field of optical communication testing, focusing on two typical application scenarios of DCN (intra-park) and DCI (inter-park), from product design and development to network construction and opening The three stages of operation, maintenance, and troubleshooting provide the industry with real and complete application and testing solutions, and promote the high-quality development of “counting from east to west”.

Product development and design stage:

Client-side high-speed optical module and physical link test solution (DCN): The main function of the multi-channel client-side optical module is photoelectric/electrical-optical conversion, which is an important part of optical communication engineering. With the increasing complexity of software and hardware inside the data center and the sharp increase in the demand for optical modules, the industry’s demand for specialized testing solutions is more urgent. Based on this, VIAVI has launched a client-side optical module one-stop test solution system, which can perform photoelectric simulation and simulation on client-side optical modules (100G, 200G, 400G, 800G) in accordance with the indicators and methods formulated by various standard protocol specifications , verification and test analysis can simulate the application environment of optical modules in the actual transmission system in the laboratory, which is convenient for R&D and verification of various parameters and performance, and helps the production of optical modules in the production line to improve efficiency and productivity.

Figure 1: VIAVI customer-side optical module test solution

Test items of the high-speed optical module on the client side:

In the application environment of Ethernet, the VIAVI test solution uses switches to forward data at network nodes, and verifies the interconnection between optical modules and switches to check whether the full link capability meets the requirements.

Figure 2. Bidirectional test between VIAVI ONT and switch

Both ends of DAC and AOC are fixedly connected, which solves the problem of optical port leakage, and is a cost-effective solution for interconnection within a rack or between adjacent racks. The VIAVI test solution implements two test modes: direct connection and Breakout. It supports two methods at the same time, which is very convenient for customers.

Figure 3. VIAVI ONT test 400GE breakout 2*200GE

◆200G QSFP56(PAM4 50Gb*4) AOC breakout 2*100G QSFP56(50Gb*2) AOC

◆200G QSFP56(PAM4 50Gb*4) AOC to 200G QSFP56(PAM4 50Gb*4) AOC

◆400G QSFP56DD(PAM4 50Gb*8) AOC breakout 2*200G QSFP56(50Gb*4) AOC

◆400G QSFP56DD(PAM4 50Gb*8)) AOC to 400G QSFP56DD(PAM4 50Gb*8) AOC

Selection of jumpers in the computer room: Fiber jumpers are an important link for the interconnection of network devices. The performance of the connectors at both ends of the jumpers directly affects the quality of optical transmission. Therefore, the management of fiber jumpers is becoming more and more important. In the test and verification of high-speed optical modules, VIAVI MAP series platforms, PCT (IL/RL test) modules can be configured according to the parameters of the R&D, production or acceptance test environment, from single-mode to OM1/2/3/4/5 Testing of all major fiber types. At the same time, VIAVI MAP series platforms can be combined with optical switching modules to support IL/RL testing of the rapidly growing MPO multi-fiber connectors, and support connectivity and polarity verification of large multi-fiber devices such as optical backplanes. In addition, they can also measure line RL of the card and optical transceiver module.

Coherent optical module and physical link test solution (DCI): Coherent optical transmission is changing the design and construction of optical networks, from the design of high-performance line cards to the evolution of an open interoperable ecosystem, and the best point of this ecology appears In 400GE, DCI and DWDM are applied and served in two different scenarios, but current suppliers mostly produce 100G and 200G pluggable modules. In 2016, OIF and related MSA organizations successively released a series of industry standards, including ZR400, OpenZR+, OpenROADM, etc. From this, coherent optical transmission is expected to enter the next wave of growth. The expected goal is to achieve interoperability, long distance and high performance. These segments will be the commanding heights that mainstream optical module manufacturers will seize.

Figure 4. VIAVI coherent 400ZR optical module test solution

Coherent 400ZR module test items:

Coherent DCO optical module (DCI box-type equipment): WDM system changes with the development of technology. For example, the emergence of coherent CFP2 DCO has greatly promoted the research and development of WDM box-type wavelength division equipment for metropolitan area networks. Currently, mainstream manufacturers are in Development and testing of such devices is carried out. It is reported that these devices and systems work on C wave (191.35~196.1THz). The line side of the device needs to support 400G with 16 QAM modulation format and 200G CFP2 DCO with QPSK modulation format, and the client side needs to support 100G 100GE, OTU4, 100GE FLEXE and other business applications. The system involves many types of services and includes various types of overhead, alarm and optical characteristics. For the above characteristics, VIAVI defines and describes the relevant test items.

5. VIAVI DCI equipment test plan

VIAVI DCI equipment test items:

Long-distance optical cable selection: In addition to considering the fiber core type (such as G.654E), manufacturers also need to verify the tensile and torsional performance of the optical cable in the field environment. Chapter IEC60794-1-21 stipulates the stress of optical cables in different scenarios. International and domestic mainstream optical cable manufacturers have also conducted relevant research. The stress change of optical cables should not exceed 0.2%, in order to ensure the health and safety of optical cables.

VIAVI’s DTSS (Distributed Temperature and Stress System) has an international patent. It is a type of instrument that can decouple temperature and stress. It is more in line with the complexity requirements in practical applications and ensures the accuracy and effectiveness of test data.

Network construction and opening stage:

Construction and commissioning of ZR equipment on the live network: In the deployment and commissioning phase, the ONA1000 portable instrument can be used for QSFPDD ZR verification test:

    ▷Insert ONA1000 into QSFPDD ZR, and access to WDM system through optical fiber.

▷Switch the wavelength of QSFPDD ZR to the specified wavelength (such as 191.3THz) through ONA1000, wait for the module to enter the Ready state, and at the same time switch the wavelength of the QSFPDD ZR module of the opposite channel to the same wavelength and perform loopback settings on the opposite router so that the signal Return from the same channel.

    ▷Check on the ONA1000 instrument to see if there is an alarm. If the result is normal, you can switch to the next wavelength and repeat the above steps to complete all channel tests.

      ▷ If all channels are normal, the verification is complete.

Service test and activation: VIAVI Metro series provides full-rate (10M to 400GE), efficient Ethernet automated test templates, embedded with a unique fast convergence algorithm, which can save 20%-50% of tests compared with other commonly used test templates time, greatly improving the service provisioning efficiency. At the same time, VIAVI launched the industry’s first OTN Check function that supports the standardized test process for OTN service provisioning to ensure the standardization and high efficiency of OTN service provisioning.

High-precision one-way delay test: The “East Count West” project not only requires a large amount of transmitted data and high reliability, but also hopes to reduce the transmission delay as much as possible to meet the needs of more low-latency applications, such as billing , games, etc. According to the current design requirements of the transmission network, the one-way delay of the optical transmission network between cities is not greater than 10ms, and the one-way delay between hubs is not greater than 20ms. Driven by industry demand, the VIAVI transmission data tester has a built-in high-precision rubidium atomic clock function, which realizes high-precision one-way delay testing at the ns level, and ensures high-precision one-way delay testing even when there is no satellite signal inside or outside the computer room. To the delay test.

Active cable and fan-out cable verification: One-click automatic test and performance verification of active cable AOC/DAC/fan-out cable through ONA1000/800, MTS5800, etc., to ensure that the cable indicators meet the network design requirements.

OSNR signal-to-noise ratio test (on-line test of coherent signals): OSNR (signal-to-noise ratio) in super 100G OTN networks has always troubled network construction and maintenance personnel. This is due to the existence of multiple polarization states, the traditional online OSNR monitoring relying on polarization separation technology can no longer be realized, coupled with the use of ROADM/OXC, the filtered channel signal no longer has the conditions to compare with the original waveform, the traditional relying on The way the mathematical model calculates OSNR is no longer feasible.

To this end, VIAVI launched the first instrument Pol-Mux OSCA-710 that uses inter-spectral correlation technology (SCorM, VIAVI patent), which realizes the coherent transmission of 100 Gb/s, 200 Gb/s and 400 Gb/s signals (polarized Multiplexing) system in-band OSNR accurate test, and the test of chromatic dispersion (CD) per channel, and there is no need to shut down the network or related channels during the test.

Figure: OSCA710 polarization multiplexing network online OSNR test

Integrated cabling Tier1/Tier2 test certification: VIAVI OLTS and MPOLx optical loss test suites provide the necessary tests for Tier 1 based fiber length certification, optical loss and correct polarity (especially important for MPO), enabling single-mode and multi-mode Fast and accurate testing of mode fibers while generating certification reports. At the same time, the VIAVI high-precision OTDR provides a full-featured layer 2 fiber solution that can troubleshoot network problems by pinpointing the exact location of any event that causes excessive loss. For copper testing, the Certifier10G/40G can quickly and accurately test copper or fiber optic cables.

Optical cable line performance test G.654E complete solution

VIAVI not only supports the performance test of traditional G.652D and G.655 fiber, but also matches the new test scheme for the new G.654E fiber. G.654E has a lower attenuation coefficient and a larger effective area, which can significantly reduce the nonlinear effect of optical fiber and improve the OSNR of the system, thereby increasing the transmission distance of the system without electrical relay, reducing the number of relay stations, and reducing network delay. However, its special performance also puts forward higher requirements for the test content:

Test wavelength: The cut-off wavelength of G.654E fiber is different, and a new OTDR test wavelength of 1550, 1625 or 1650nm is required;

Bi-directional test: Built-in intelligent interactive system, one-button bi-directional test, solves the problem of inaccurate OTDR test events and complex & polarity error-prone problems of bi-directional test; supports bi-directional test function of single-core and multi-core optical cables (MPO 12/24).

Figure: Multi-core (MPO 12/24) one-button bidirectional test

In addition, VIAVI also provides a dispersion solution based on G.654E fiber, which is an integrated design for CD/PMD/AP.

Operation maintenance and troubleshooting phase:

The testing of transmission equipment and services has been introduced in the construction and commissioning stage of the previous part. The test plan is also applicable to the operation and maintenance troubleshooting stage, such as service commissioning test, optical module performance test, AOC/DAC cable test, optical cable test, etc. .

Wisdom optical network management system:

On the basis of realizing the original optical cable attenuation, length, interruption judgment and other functions, VIAVI enhanced intelligent optical network management system adds extreme speed and extreme sensitivity mode:

▷It can capture instantaneous faults, and the fault duration is less than 1s

▷Quick recording and storage of instantaneous fault curves

▷ Combined with the analysis system to give the latitude and longitude of the fault

▷ Send detailed alarm information by direct mail and SMS

▷Analyze the reasons according to the model, and give treatment suggestions

Figure: Extreme mode test results

Security anti-eavesdropping function:

▷Enhance network security management

▷Security-sensitive networks, government, banking, securities, military, scientific research, public security and other private networks

▷Pre-alarm to prevent information theft

Optical cable dumb dimension resource management:

VIAVI enhanced intelligent optical network management system integrates DTSS (distributed optical fiber sensing system) to realize dumb-dimensional resource management and optical cable health analysis. Typical indicators include:

▽Verification of the overhead section of the optical cable;

▽ Optical cable model judgment and optical cable hybrid check;

Figure: Brillouin Spectrum Characteristics of Optical Cables and Cable Types

▽Verification of excess cable length resources;

▽Analysis of optical cable health: no loss abnormal optical cable, there may be stress exceeding the standard point, and it is in a sub-healthy state;

Optical cable and route verification:

In summary, focusing on the three stages of product development and design, network construction and opening, operation and maintenance, and troubleshooting, VIAVI escorts the entire life cycle of optical communication products, providing the industry with real and complete testing from the laboratory to the field The solution has built a solid and reliable optical network base for the rapid and stable development of the “East Counting West Counting” industry chain.