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Cabling Data Center Process: Planning & Implementing its Infrastructure

Today’s data centers are the home to diverse bandwidth-demanding devices, like servers, storage systems, and backup devices which are interconnected by networking equipment. All these devices drive the need for reliable and manageable cabling infrastructure with higher performance and more flexibility for today and future growth. While managing the cabling in data centers, two main processes are included: planning the cabling infrastructure and implementing the cables.
Planning the Cabling Infrastructure
As networking equipment becomes denser, and port counts in data centers increase to several hundred ports, managing cables connected to these devices becomes a difficult challenge. Thus, during planning the cabling infrastructure, it’s wise to do the following:
Choosing Fiber Cable Assembly
This assembly has a single connector at one end of the cable and multiple duplex breakout cables at the other end, an alternative to avoid cable management. The LC (Lucent Connector) –MPO (Multifiber Push-On) breakout cable assemblies are designed to do just that. The idea is to pre-connect the high-density, high- port-count LC equipment with LC-MPO breakout cable to dedicated MPO modules within a dedicated patch panel, reducing equipment cabling clutter and improving cable management. This image below show the LC-MPO breakout cable assembly that consolidates six duplex LC ports into one MPO connection.
Nowadays, this breakout technology is widely used in 40 Gigabit Ethernet (GbE) applications. Like QSFP-4X10G-AOC10M, this product is the QSFP to four SFP+ active optical breakout cable assembly with the 10m short reach.
Using Color to Identify Cables
Color coding simplifies management and can save you hours when you need to trace cables. Cables are available in many colors (table shown below). For instance, multi-mode fiber (MMF) looks in orange (OM1, OM2) and in aqua (OM3), while yellow is usually the color of single-mode fiber (SMF) which is taken as the transmission media when the required distance is as long as 2km, or 10km . Take WSP-Q40GLR4L for example, this 40GBASE-LR4L QSFP+ transceiver works through SMF for 2km link length.
Implementing the Cabling Infrastructure
While implementing the cables, the following tasks should be obeyed by.
Testing the Links
Testing cables throughout the installation stage is imperative. Any cables that are relocated or terminated after testing should be retested. Although testing is usually carried out by an authorized cabling implementer, you should obtain a test report for each cable installed as part of the implementation task.
Building a Common Framework for the Racks
this step is to stage a layout that can be mirrored across all racks in data centers for consistency, management, and convenience. Starting with an empty 4-post rack or two, build out and establish an internal standard for placing patch panels, horizontal cable managers, vertical cable managers, and any other devices that are planned for placement into racks or a group of racks. The INTENTION is to fully cable up the common components while monitoring the cooling, power, equipment access, and growth for the main components in the racks.
A good layout discourages cabling in between racks due to lack of available data ports or power supply ports, allowing more power outlets and network ports than you need. This will save you money in the long run as rack density increases, calling for more power and network connectivity. Using correct length cables, route patch cables up or down through horizontal patch panels alleviates overlapping other ports. Some cable slack may be needed to enable easy removal of racked equipment.
Documentation
Typically, the most critical task in cable management is to document the complete infrastructure: including diagrams, cable types, patching information, and cable counts. It’s advised update the documentation and keep it accessible to data center staff on a share drive or intranet Web site.
Stocking Spare Cables
It’s sestible to maintain an approximately the same amount on the installed cabling and ports in use, so as to face the environment variation or emergency.

Two Main Questions About Direct Attach Cables

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The increasing bandwidth demands in data centers call for new cost-effective network solutions that are able to provide great bandwidth and improved power efficiency. As such, direct attach cables (DACs) are designed to replace expensive fiber optic cables in some Ethernet applications, like choosing SFP+ DACs and QSFP+ DACs accordingly as 10 Gigabit Ethernet (GbE) and 40GbE cabling solutions to achieve high performance. How much do you know about this kind of cable? Do you know its such basic information as classifications? If not, then you can follow this article to understand DAC in depth based on the two main questions.
Question 1: What Is DAC?
DAC, a kind of optical transceiver assembly, is a form of high speed cable with “transceivers” on either end used to connect switches to routers or servers. Often referred to as twin-ax, this direct attach twin-axial cable is very similar to coaxial cable, except for one additional copper conductor core. DACs are much cheaper than the regular optics, since the “transceivers” on both ends of DACs are not real optics and their components are without optical lasers. In some 10GbE and 40GbE infrastructures, DACs have been selected to replace fiber optic patch cord when the required link length is relatively short. And in storage area network, data center, and high-performance computing connectivity, DACs are preferable choice because of their low cost, low power consumption and high performances.
Question 2: How DAC Is Classified?
When it comes to DAC’s classifications, there exist two primary standards: Ethernet transmission rate, material of cables.
Based on Ethernet transmission rate and construction standard, 10G SFP+ DACs, 40G QSFP+ DACs, and 120G CXP+ DACs are all available, meaning that DAC can be used as transmission medium for 10GbE, 40GbE, and 120GbE applications when combined as transceivers. Typical DAC assemblies have one connector on each end of the cable. Take SFP-10G-AOC1M for example, this Cisco compatible SFP+ to SFP+ Direct-Attach Active Optical Cable assembly has one SFP+ connector on each end of the cable, designed for relatively short reach that is 1m.
According to material of cables used, DACs are available in direct attach copper cables and active optical cables (AOCs).
Direct Attach Copper Cable
Direct attach copper cables are designed in either active or passive versions, providing flexibility with a choice of 1-, 3-, 5-, 7-, and 10-meter lengths. The former provides signal processing electronics to avoid signal issue, thus to improve signal quality. What’s more, the former can transmit data over a longer distance than the latter which offers a direct electrical connection between corresponding cable ends. Both direct attach passive copper cables and direct attach active copper cables have gained popularity in data centers. For instance, EX-QSFP-40GE-DAC-50CM, the Juniper 40G cabling product, hot-removable and hot-insertable, is the QSFP+ to QSFP+ direct attach passive copper cable assembly, really suitable for short distances of up to 0.5m(1.6ft), appropriate for highly cost-effective networking connectivity within a rack and between adjacent racks.Active Optical Cable
AOC is also one form of DAC. It uses electrical-to-optical conversion on the cable ends to improve speed and distance performance of the cable while mating with electrical interface standard. Compared with direct attach copper cable, its smaller size, electromagnetic interference immunity, lower interconnection loss and longer transmission distance make it popular among consumers.
DACs offer great flexibility in cabling length choices, simplify server connectivity in top-of-rack deployments, and reduce the power needed to transmit data. More importantly, DACs ensure high system reliability after going through rigorous qualification and certification testing, helping network designers to achieve new levels of infrastructure consolidation while expanding application and service capabilities.

Considerations About Fiber Optic Transceiver Designing

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The rapid expansion of fiber optic networks, including data services measured by data volume or bandwidth, shows that fiber optic transmission technology is and will continue to be a significant part of future networking systems. Network designers are becoming increasingly comfortable with fiber solutions, since the use of which allows for more flexible network architecture and other advantages, such as EMI (Electromagnetic Interference) resilience and data security. Fiber optic transceivers play an really important role in these fiber connections. And while designing fiber optic transceivers, three aspects need to be considered: environmental situation, electrical condition and optical performance.
What Is a Fiber Optic Transceiver?
The fiber optic transceiver is a self-contained component that transmits and receives signals. Usually, it is inserted in devices such as routers or network interface cards which provide one or more transceiver module slot. The transmitter takes an electrical input and converts it to an optical output from a laser diode or LED. The light from the transmitter is coupled into the fiber with a connector and is transmitted through the fiber optic cable plant. Then the light from the end of the fiber is coupled to a receiver where a detector converts the light into an electrical signal which is then conditioned properly for use by the receiving equipment. There are a full range of optical transceivers available in telecommunication market, like SFP transceiver, SFP+ transceiver (eg. SFP-10G-SR shown below), 40G QSFP+, 100G CFP, etc.
Designing Considerations
It’s true that fiber links can handle higher data rates over longer distances than copper solutions, which drive the even wider use of fiber optic transceivers. While designing fiber optic transceivers, the following aspects should be taken into consideration.
Environmental Situation
One challenge comes to the outside weather—especially severe weather at elevated or exposed heights. The components must operate over extreme environmental conditions, over a wider temperature range. The second environmental issue related to the fiber optic transceiver design is the host board environment which contains the system power dissipation and thermal dissipation characteristics.
A major advantage of the fiber optic transceiver is the relatively low electrical power requirements. However, this low power does not exactly mean that the thermal design can be ignored when assembling a host configuration. Sufficient ventilation or airflow should be included to help dissipate thermal energy that is drawn off the module. Part of this requirement is addressed by the standardized SFP cage which is mounted on the host board and also serves as a conduit for thermal energy. Case temperature reported by the Digital Monitor Interface (DMI), when the host operates at its maximum design temperature, is the ultimate test of the effectiveness of the overall system thermal design.
Electrical Condition
Essentially, the fiber transceiver is an electrical device. In order to maintain error free performance for the data passing through the module, the power supply to the module must be stable and noise-free. What’s more, the power supply driving the transceiver must be appropriately filtered. The typical filters have been specified in the Multisource Agreements (MSAs) which have guided the original designs for these transceivers. One such design in the SFF-8431 specification is shown below.
Optical Performance
Optical performance is measured as Bit Error Rate, or BER. The problem facing designing optical transceiver lie in the case that the optical parameters for the transmitter and receiver have to be controlled, so that any possible degradation of the optical signal while traveling along the fibers will not cause poor BER performance. The primary parameter of relevance is the BER of the complete link. That is, the start of the link is the source of the electrical signals which drive the transmitter, and at the end, the electrical signal is received and interpreted by the circuitry in the host by the receiver. For those communication links which use optical transceivers, the primary goal is to guarantee BER performance at different link distances, and to ensure broad interoperability with third party transceivers from different vendors.

Transceiver Selection Guide for Your Networking Use

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Thanks to the advances made in fiber optical technologies, fiber solutions have been deployed in ever-increasing applications where high-speed and high-performance data transmission is needed. They outweigh the copper solutions in such aspects as higher bandwidth, longer distances and Electromagnetic interference (EMI) immunity. Transceivers, one of the key components required in such fiber connections for high networking performance, have experienced the never-ceasing industrial designs, from lower port density to higher, from the standard modules to the final hot-plable ones, to meet the ever more flexible networking infrastructure.
There is a broad selection of hot-plable transceiver modules available for fiber networking use, and you may feel a little confused about how to select the correct transceivers for your networking transmission. In this article, I will illustrate different aspects of transceivers that need to be known before choosing a transceiver.
Transceiver Basics
Before giving guidance to transceiver selection, it’s necessary to know the basics of transceiver. Transceiver is a combination of a transmitter and a receiver in a single package, while they function independently for bidirectional communication. Typically, a fiber optic transceiver converts the incoming optical signal to electrical and the outgoing electrical signal to optical. More specifically, the transmitter takes an electrical input and converts it to an optical output from a laser diode or LED. The light from the transmitter is coupled into the fiber with a connector and is transmitted through the fiber optic cable plant. The light from the end of the fiber is coupled to a receiver where a detector converts the light into an electrical signal which is then conditioned properly for use by the receiving equipment.
Here go the several aspects of transceivers that are helpful in your purchasing.
Form-factor
Multi-source agreements (MSAs) between different equipment vendors specify guidelines for electrical and optical interfaces, mechanical dimensions and electro-magnetic specification of a transceiver. The equipment vendors follow these MSA defined values for designing their systems to ensure interoperability between interface modules. The form-factor or the MSA-type is needed so that the transceiver can mechanically and electrically fit into a given switch, router, etc. Transceiver MSAs define mechanical form factors including electric interface as well as power consumption and cable connector types. There are various MSA types: SFP (eg. MGBSX1), SFP+, XFP, CFP, CFP2, CFP4, QSFP and so on.
Transmission Media
Transceivers can work over single-mode fiber (SMF), multi-mode fiber (MMF), and copper. In different Ethernet applications, media can achieve different link lengths when combined with transceivers. Take Gigabit Ethernet (GbE) applications for example, single-mode transceivers can have a transmission distance of 5km to 120km, while multi-mode transceivers are defined to have the maximum reach of 55om, with copper solution establishing even fewer link length at 25m. Take MGBLX1 for example, this Cisco compatible 1000BASE-LX SFP works through SMF for 10km reach.
Power Budget
The transceiver power budget is the difference between transmitter launch power and receiver sensitivity and has to be 2-3dB larger (Margin) than the measured link loss. If the link loss cannot be measured, it has to be calculated. Therefore transmission distance [km], the number of ODFs, patches and passive optical components (Muxes) have to be known. Common values for power budget are <10, 14, 20, 24, 28, >30dB.
If you’re seeking high-speed data carrier, transceivers can help accomplish goals. By transmitting data at 10Gbit/s, 40Gbit/s, 100Gbit/s or 12940Gbit/s, they can ensure that data arrives quickly. Transceiver modules that are capable of handling fast speeds can help with downloads and high and low bandwidth video transmission.

1000BASE-X SFP Modules Overview

A continuous stream of manufacturing process improvements and product innovations has given fiber optical system several advantages, like longer distance reach, larger data-carrying capacity, greater bandwidth and lower power consumption. Among these fiber optical product innovations, hot-plable transceiver modules should come to the central point with their unique designs. They have been constantly designed, and finally been reinvented as hot-plable modules along with the optical technological advances. These small, hot-plable serve as the key components in accommodating the demands of higher port density and more networking flexibility.
Transceiver modules come into various types: SFP (small form-factor plable), SFP+ (small form-factor plable plus), QSFP+ (quad small form-factor plable plus), etc. This article mainly introduces SFP transceiver modules which are widely applied in Gigabit Ethernet (GbE) applications, with the focus on several 1000BASE-X interface types, including 1000BASE-SX, 1000BASE-LX, 1000BASE-EX, and 1000BASE-BX10-D/U.
Features and Benefits
1000BASE-X SFP modules provide a wide range of form factor options for enterprise and service provider needs. They are designed with the following features and benefits:
Hot swappable to maximize uptime and simplify serviceability;
Flexibility of media and interface choice on a port-by-port basis, so you can “pay as you populate”;
Sophisticated design for enhanced reliability;
Supports digital optical monitoring (DOM) function;
1000BASE-X SFP Interface Types
1000BASE-SX SFP
1000BASE-SX SFP, compatible with the IEEE 802.3z 1000BASE-SX standard, operates on legacy 50Ľm multi-mode fiber (MMF) links up to 550m and on 62.5Ľm Fiber Distributed Data Interface (FDDI)-grade MMFs up to 220m. Take DEM-311GT for example, Fiberstore compatible D-Link 1000BASE-SX SFP is able to realize 550m link length through OM2 MMF with duplex LC.
1000BASE-LX SFP
1000BASE-LX SFP, compatible with the IEEE 802.3z 1000BASE-LX standard, is specified to support link length of up to 10km on standard single-mode fiber (SMF), to 550m on MMFs. When used over legacy MMF, the transmitter should be coupled through a mode conditioning patch cable. The laser is launched at a precise offset from the center of the fiber which causes it to spread across the diameter of the fiber core, reducing the effect known as differential mode delay which occurs when the laser couples onto only a small number of available modes in MMF.
1000BASE-EX SFP
1000BASE-EX, sometimes referred to as LH, is a non-standard but industry accepted standard which works on standard SMF with fiber link spans up to 40km in length. For back-to-back connectivity, a 5-dB inline optical attenuator should be inserted between the fiber optic cable and the receiving port on the SFP at each end of the link. 1000BASE-EX SFPs (eg. GLC-EX-SMD) run on 1310nm wavelength lasers, and achieves 40km link length.
1000BASE-BX10-D/U SFP
The 1000BASE-BX-D and 1000BASE-BX-U SFPs, compatible with the IEEE 802.3ah 1000BASE-BX10-D and 1000BASE-BX10-U standards, operate on a single strand of standard SMF (figure shown below). A 1000BASE-BX10-D device is always connected to a 1000BASE-BX10-U device by a single strand of standard SMF with an operating transmission distance up to 10km.
The communication over a single strand of fiber is accomplished by separating the transmission wavelength of the two devices (figure shown above): 1000BASE-BX10-D transmits a 1490nm channel and receives a 1310nm signal, whereas 1000BASE-BX10-U transmits at a 1310-nm wavelength and receives a 1490-nm signal. In this figure, the wavelength-division multiplexing (WDM) splitter is integrated into the SFP to split the 1310nm and 1490nm light paths.

10GbE Interconnect Solutions Overview

New sophisticated networking services, coupled with the increase of Internet users push the Internet traffic to an even higher point, driving the need for increased bandwidth consequently. One Ethernet technology—10 Gigabit Ethernet (GbE) is adequate for such bandwidth demand, and has become widely available due to the competitive price and performance, as well as its simplified cabling structure.
Several cable and interconnect solutions are available for 10GbE, the choice of which depends on the maximum interconnect distance, power budget and heat consumption, signal latency, network reliability, component adaptability to future requirements, cost. Here cost includes more than what we call the equipment interface and cable cost, but more often the labor cost. Thus, choosing a 10GbE interconnect solution requires careful evaluation of each option against the specific applications. This text aims to introduce two main 10GbE interconnect solutions: fiber optics and copper.
Fiber Optics Solution
Fiber optic cables include single-mode fiber (SMF) and multi-mode fiber (MMF). MMF is larger in diameter than that of single-mode, thus portions of the light beam follow different paths as they bounce back and forth between the walls of the fiber, leading to the possible distorted signal when reach the other end of the cable. The amount of distortion increases with the length of the cable. The light beam follows a single path through thinner single-mode cable, so the amount of distortion is much lower.
The typical 10GBASE port type that uses MMF is 10GBASE-SR which uses 850nm lasers. When used with OM3 MMF, 10GBASE-SR can support 300m-connection distances, and when with OM4 MMF, 400m link length is possible through 10GBASE-SR SFP+ transceiver.
10GBASE-LR (eg. E10GSFPLR), 10GBASE-ER and 10GBASE-ZR are all specified to work via SMF. SMF can carry signals up to 80km, so it is more often used in wide-area networks. But since SMF requires a more expensive laser light source than MMF does, SMF is replaced by MMF when the required connection distance is not so long.
Copper Solution
10GBASE-CX4, SFP+ Direct Attach (DAC) and 10GBASE-T are all specified to operate through copper medium.
10GBASE-CX4
Being the first 10GbE copper solution standardized by the IEEE as 802.3ak in 2002, 10GBase-CX4 uses four cables, each carrying 2.5gigabits of data. It is specified to work up to a distance of 15m. Although 10GBase-CX4 provides an extremely cost-effective method to connect equipment within that 15m-distance, its bulky weight and big size of the CX4 connector prohibited higher switch densities required for large scale deployment. Besides, large diameter cables are purchased in fixed lengths, causing problems in managing cable slack. What’s more, the space isn’t sufficient enough to handle these large cables.
SFP+ DAC
SFP+ Direct Attach Cable (DAC), or called 10GSFP+Cu, is a copper 10GBASE twin-axial cable, connected directly into an SFP+ housing. It comes in either an active or passive twin-axial cable assembly. This solution provides a low-cost and low energy-consuming interconnect with a flexible cabling length, typically 1 to 7m (passive versions) or up to 15m (active versions) in length. Below is the SFP+ to SFP+ passive copper cable assembly with 1m length, 487655-B21, a HP compatible 10GbE cabling product.
10GBASE-T
10GBASE-T, known as IEEE 802.3an-2006, utilizes twisted pair cables and RJ-45 connectors over distances up to 100m. Cat 6 and Cat 6a are recommended, with the former reaching the full length at 100m, and the latter at 55m. In a word, 10GBASE-T permits operations over 4-connector structured 4-pair twisted-pair copper cabling for all supported distances within 100m. Besides, 10GBASE-T cabling solution is backward-compatible with 1000BASE-T switch infrastructures, keeping costs down while offering an easy migration path from 1GbE to 10GbE.