Outdated optical fiber technology is not required in modern data centers

Do you remember the previous topic about "Optical Fiber for the future? Regardless of the answer, we need to pay close attention to the development of optical fiber technology and the capabilities of suppliers. At the same time, combined with application guarantees, we can ensure the maximum return on investment from the most critical fiber network in the modern data center. Industry standards also need to be constantly revised to meet the requirements of high-performance Optical Fiber systems. As work continues, ISO/EIA organizations will eventually develop well-developed international standards, but you also need to understand these trends as customers.

Centralized Network Architecture CNA) or "fiber-to-desktop" is a typical case of future-oriented optical fiber design, but these networks are indeed outdated. In the network backbone network and data center fields, most network managers will encounter similar situations. When the bandwidth demand increases, the early multi-mode optical fiber will decrease the available distance over time. Many customers begin to replace the OS2 optical fiber because the "future" of this optical fiber is very limited.

Many optical connectors we use in the data center network, such as Biconic, ST, MTRJ, and even SC connectors, are outdated or about to expire. At the same time, the international standards of optical network technology are far behind the current demand and reality of data center networks. Market demand drives the development of optical fiber and copper Technology in the direction of higher bandwidth and higher density. In the past, customers thought they invested in CNA optical fiber networks and purchased final products in the future. In fact, today's application requirements are not exactly consistent with industry standards and actual operations. Therefore, understanding this gap helps avoid investment in outdated optical fiber technology!

Optical fiber, like other technologies in the data center, must keep pace with the increasing bandwidth demand. Multimode Optical Fiber, once considered as "high" bandwidth, has reached its limit. With the continuous development of multi-mode optical fiber technology, bandwidth capacity can also be continuously improved. Interestingly, this development path clearly reflects the limitations of multimode optical fiber. A series of minor changes and adjustments of optical devices can achieve higher bandwidth capabilities. However, for modern data centers, it is necessary to reconsider the design and installation specifications of optical fiber networks.

 

Figure 1: optical fiber transmission distance and speed

Multimode Optical Fiber standard OM3 or OM4) is the transmission medium currently selected for most data center applications. The bandwidth provided by OM3/OM4 Optical Fiber greatly increases, and supports 40g and G speeds to meet the bandwidth requirements of next-generation network solutions, this does not mean that a single-core optical fiber can support long-distance transmission of 40g or G. Instead, the standard already allows multi-core optical fiber to work in parallel and provides a total bandwidth of n x 10g, where N is the number of optical fiber used. In this way, the 8-core optical fiber can work together to provide 40 Gb bidirectional bandwidth. Similarly, the 20-core optical fiber can provide GB connection.

Although the use of optical fiber parallel transmission can solve high bandwidth needs, there are still some problems in the actual operation process. We usually think of each fiber link as two connectors-transmitter and receiver. So how can we use these 8-or 20-Core Optical Fibers in parallel? Fortunately, NTT has developed a multi-core optical fiber Parallel Processing Method many years ago. Multi-core fiber connectors such as MPO can organize multi-core fiber cables to achieve logical and mechanical performance.

Figure 2 MPO connector, offering different specifications from 12-core to 72-core

The design of the data center needs to be carefully planned and organized to ensure reliability and scalability. Sometimes it is difficult for us to understand that a specific wiring method will eventually lead to disasters. For example, TIA942 data center standards describe the best implementation scheme for planning a data center and Create structured concepts and rules for data center Cabling Design. These concepts define the wiring areas for allocating resources within the data center. Therefore, a practical optical fiber solution must support multiple connection points to support the Structured Cabling Design for data centers to allocate resources.

The data center must be highly scalable and can be implemented using many potential applications, topologies, and architectures. Data center operators are looking for modes that can save money and optimize operating costs. This requires designers to design modular systems that are small-scale and can be quickly expanded. These changeable, deployable, and reusable solutions provide building modules. Is an example of a highly scalable design solution.

Figure 3: An example of a highly scalable design solution

In addition to flexible wiring and multi-channel optical fiber, the Supported Distance of optical fiber can greatly improve the scalability and utility of the system. Taking a large data center as an example, a large data center must support multiple connection points and cover a large area. The maximum distance supported by the optical fiber cabling system is a major consideration.

Therefore, it is necessary to develop cabling application specifications that support applications of 40 GB and GB. We know that point-to-point connections of OM3 optical fiber can support 40g and 100g applications within a m transmission distance. OM4 Optical Fiber supports a transmission distance of 150 meters. It is important to understand how to apply it to the real-world data center design, including the use of Point-to-Point configuration for multi-link and interconnect wiring of regional cabling and layered architecture ). The loss of each connector in the connection wiring loss link leads to a reduction in the total supported transmission distance. However, the loss of transmission distance caused by the connection wiring loss is not constant. Multi-link and wiring must be included in the system design. The customer must understand and consider the impact of these factors on reliability.

For example, an 8g Fiber Channel application must be deployed according to its unique rules. For optical fiber channels and Ethernet, the rule to be followed is that high-performance Optical Fiber and connectors must be used for structural cabling of data centers. Just as low-bandwidth optical fibers are outdated, the current ISO and TIA Optical Fiber Connection standards are no longer keeping up with the times. Currently, industry standards stipulate that the loss of each connector is 0.75db. Only two "standard" connectors can meet the maximum allowable connection loss standards in modern high-speed applications. The good news is that today's technology can easily go beyond the "standard" of connector loss ". The bad news is that when we design an actual data center, we cannot continue to refer to these standard values. We need a new way to define the performance of the optical fiber system.

Figure 4: end-to-end link loss is the total loss of all components. The loss value is specified by the manufacturer. The maximum loss value must be within the application range.

The purpose of setting industry standards is to clearly define a risk-free design. In the past, end users did not need to design their own solutions because industry standards could provide design guidelines and general application support. Imagine what users will face if there is no practical industry standard? A typical design example: a 160-meter long fiber link with three jumpers is required. How long does this link support 8g fiber channels? What should I do if I need more jumpers or longer transmission distances? Who will verify the new wiring configuration? Can it meet actual application requirements and support products of all source equipment vendors? What is our "New Standard?

This "New Standard" can be defined from the perspective of components. For example, the accepted connector loss "standard" value is 0.75db. However, we may actually expect a loss value of 0.2db or even smaller. Set a maximum system loss value in actual application, which may be lower than 1.5db. Therefore, subtract the loss of the optical fiber used from the allowable total loss and divide it by the number of connectors used to obtain the performance of the required connector. Finally, we can compare the loss value with the product statement claimed by the wiring manufacturer. Please note that to ensure design consistency, the supplier must ensure the maximum loss value, rather than using data that produces optimistic illusion like "average" or "typical value.

In this method, the end user designs the system and verifies the application support. Suppliers are generally not responsible for designing the entire system, but need to provide a large amount of data required for design decisions. Some end users think there should be a better way to solve this problem. Some vendors can provide the application guide for guarantee. The following table is used as an example. Generally, basic design elements of the data center topology are used to describe the overall application support.

For more information about how to design new applications, see the following 4g Fiber Channel table. After evaluating the data center design requirements, you can determine the distance supported by the optical fiber, the number of connectors, and the transmission speed. Design solutions for data centers that comply with the following table, so that customers can simply verify and ensure that they can support the required applications.

The design, application, and capacity of the data center change frequently. A typical example: to expand from a 4G Fiber Channel to an 8G Fiber Channel, you need to increase the bandwidth of the storage application. The new technology can provide higher throughput. Generally, the port density of the new generation devices also increases. Two considerations should be taken into account when evaluating new devices to be used. Does the current infrastructure support Speed upgrade? Is there enough space to add the number of ports on the new switch? Similarly, we can use the Application Guide provided by the vendor to answer these questions.

The following table specifies the impact of the new application. When the speed increases, the maximum transmission distance is reduced. Take the OM4 optical fiber as an example. The following table lists the maximum distances supported by the optical fiber cables, for example, using 6 LC and 6 MPO coupler). The 8G Optical Fiber Channel supports 150 meters, the 4G Fiber Channel supports 340 meters. Although the number of connectors is large, it reflects the actual needs of some applications.

Network planners and data center designers can use these tables to check whether network upgrades are feasible. If planning requires higher development speed, you can select the area size and wiring topology in advance to ensure future applications. Future plans may include 16g fiber channels. The coverage area of the 16g Fiber Channel Guide may be smaller than that of the 8g Fiber Channel. Similarly, the 16g Optical Fiber Channel application support form can be used as a basis for determining the longest distance and wiring combination that the 16G switch can provide. In the initial stage of data center design, we can ensure that the 16 GB technology will be used in the future. This method also applies to the planning of 40g and G Ethernet. The application guide table provides guidelines for design and implementation.

All in all, the design of data center optical fiber systems requires a new approach that must include optical system specifications that are directly related to the support of modern high-speed applications. When the vendor provides end users with an application design guide, the customer can clearly understand the design options. Provides appropriate methods for system designers and operators based on the specification defined by topology and transmission distance. Vendors provide secured support for these application standards to ensure that system integrators share the responsibility for design and support in an appropriate manner.