Månadsvis arkiv: October 2016
With the top trend for data center and enterprises to move to higher data rate like 40G, relevant products and technologies are developed to back this new speed (e.g. the 40G optical transceivers and cables). However, there are so many options out there on the market. Network users usually don’t know how to make a choice. Take the 40G cables as an example, the most commonly used 40G cables are the 40G direct attached cable (DAC) and active optical cable (AOC). Each has its unique specification and usage. Which would be the most suitable one for connecting signals across the rack in data center? This article will provide you an ideal answer from the aspect of cabling performance, transmission distance and cost.
Brief Overview of DAC and AOC Cables
QSFP DAC cable is a form of high-speed cable with “transceivers” on either end used to connect 40Gbqs switches to routers or servers. QSFP+ DAC cable usually comes in either active or passive versions. They are widely available for short-reach 40G interconnect (within 7 meter). 40G DAC cables transmit 40GbE over short distances of parallel coaxial copper cabling. It uses a special cabling assembly with four lanes of coaxial cabling. Each transmit 10 Gbps for a total data rate of 40 Gbps. QSFP to QSFP and QSFP to SFP+ cable are the two common types of 40G DAC cables. The picture below shows a QSFP to SFP+ DAC breakout cable connected in a switch.
AOC cable 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 DAC cables, its smaller size, longer transmission distance, lower insertion loss and electromagnetic interference immunity make it popular among subscribers. 40G AOC cables (see in the image below) can support longer distance than QSFP+ DAC cables (within 15m).
Comparison Between DAC and AOC Cables
After the brief introduction to the DAC and AOC cables, what to be considered next is the detailed comparison from the expects of cost, distance and cabling performance. The following chart shows a vivid comparison between them.
Cost is typically the No.1 factor affecting your selection. When it comes to 40G DAC cables, it is the same, although it’s quite clear that copper is much cheaper than optical cable. AOC, with connectors embedded with electronics and/or optics is the most expensive one. But it supports the highest transmission distance, many data centers won’t choose it because of the high cost.
While passive copper cable is much cheaper than AOC. However, the truth is that it cannot support 40G transmission in most cases in data center. Active copper cable is less expensive than AOC and can support longer transmission than passive copper cable seems to be a good choice. In this battle over cost, passive copper cable wins. But it is not suggested for 40G transmission in most cases.
The main reason why DAC active copper cable and AOC can support longer transmission distance than passive cooper cable is that they are supported with active electronics. Passive copper cable requires no power. For 40G transmission, the power required for active copper cable is about 440mW, which is much less than that of AOC—2W. Thus, passive copper cable wins for its low power consumption.
Cooling is always crucial for data center, as it is closely related to the data center reliability and life of use. During DAC cable selection, two main factors can affect the cooling of data center. One is cable size. the other is the power consumption of direct attached cable. For the former factor, the thinner the cable is, the better dispersion devices in data center would have. AOC cable is the thinner than DAC cables. And DAC active copper cable is also thinner than passive cooper cable. The relation between power consumption and data center cooling is easy to understand. Higher power consumption can generate more heat in data center, which will load more burden on the data center cooling system. As mentioned before. AOC cable needs the highest power and DAC passive copper cable needs the lowest.
In the past, when the data rate required is less than 5 Gbps, the passive copper cables are used for interconnection. This type of DAC connects two SFP connectors by a copper cable, providing direct connection between cable ends via copper wire. Thus they are not expensive and robust with reliability. As it is passive, they need no power generally. However, when it comes to 40Gbps, they cannot satisfy such data rate in most cases. The passive copper cable with QSFP connectors attached on both ends can only support transmission 40 Gbps over very short distance. Thus passive copper cable is not suggested for regular 40G interconnection, unless 40G transmission is in very short distance.
Then AOC cable is introduced to overcome this challenge. Optical cables are thinner, flexible and can reach much longer distance up to 100 meters or more, which is much longer than that of the passive copper cable. However, AOCs are usually very expensive with the connectors attached on the active optical cable are embedded with optics and/or electronics. The connectors of the DAC active copper cable are embedded with electronics. Although they cannot support transmission distance as long as AOC, active copper cable can support longer transmission distance than that of the passive copper cable via copper wire. 40G transmission distance of active copper cable is about 15 meters.
To sum up, if you have a special requirement of the transmission distance. Then active optical cable wins with a transmission distance up to 100 meters. The active copper cable got the second place. And passive copper cable is at the last place. It is only suggested for 40G transmission over really short distance.
After comparing the performance of the DAC and AOC cables, we understand that the DAC passive copper cable is only suitable for really short-reach applications. While AOC cable possesses the best transmission performance but with higher cost in both material and daily use, and it needs more power as well. As for the DAC active copper cable, it can can support 40G transmission up to 15 meters with low power consumption, and satisfy the regular interconnection requirement for distance and cooling in most data center. What’s more, it is less expensive. FS.COM offers a full range of 40G QSFP cables including 40G DAC cable and AOC cables. Besides, the QSFP transceivers are also provided.
Fiber optic cable is considered as one of the most effective transmission medium today for safe, and long-reach communications, and it also offers a number of advantages over copper. In general, fiber optic cable consists of a core, cladding, coating, strengthening fibers, and a cable jacket, which has been clearly introduced in the previous article. Today’s article will focus on the several materials in fiber optic cable construction, as well as their features and applications.
PVC (Polyvinyl Chloride)
Polyvinyl Chloride (PVC) is one of the most commonly used thermoplastic polymers in the world. The PVC cable is typically used for patch connections in the data center, wiring closet, and at the desktop. PVC is produced in two general forms, first as a rigid or unplasticized polymer (RPVC or uPVC). The following image shows a ST single-mode pre-Terminated cable (0.9mm PVC Jacket).
- Good resistance to environmental effects. Some formulations are rated for -55 to +55.
- Good flame retardant properties. Can be used for both outdoor and indoor fiber optic cables.
- PVC is less flexible than PE (Polyethylene).
Polyethylene is a kind of polymer that commonly categorized into one of several major compounds of which the most common include LDPE, LLDPE, HDPE, and Ultrahigh Molecular Weight Polypropylene. Polyethylene fiber has a round cross section and has a smooth surface. Fibers made from low molecular weight polyethylene have a grease like handle.
- Popular cable jacket material for outdoor fiber cables
- Very good moisture and weather resistance properties
- Very good insulator
- Can be very stiff in colder temperatures
- If treated with proper chemicals, PE can be flame retardant.
Kevlar (Aramid Yarn)
The word Aramid is a generic term for a manufactured fiber in which the fiber forming substance is a long chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to the two aromatic rings as defined by the U.S. federal trade commission. Kevlar fiber is based on poly (P-phenylene terephthalamide). Aramid yarn is the yellow fiber type material found inside cable jacket surrounding the fibers. It can also be used as central strength members.
- Aramid yarn is very strong and is used in bundle to protect the fibers.
- Kevlar is a brand of aramid yarn. Kevlar is often used as the central strength member on fiber cables which must withstand high pulling tension during installation.
- When Kevlar is placed surrounding the entire cable interior, it provides additional protection for the fibers from the environment.
The steel armored fiber cable, using light-steel tube, can provide maximum bend radius, strong protection and flexible cabling. Steel armor jacket is often used on direct burial outdoor cables and it provides excellent crush resistance and is truly rodent-proof. Since steel is a conductor, steel armored cables have to be properly grounded and loss fiber optic cable’s dielectric advantage. Armored fiber optic cable are often used in the outdoor direct burial cables and for the industrial environment where cables are installed without conduits or cable tray protection. The following image shows a single-mode armored fiber optic cable.
Various types of these light-steel armored fiber cables are in stock in FS.COM, including pre-terminated armored fiber patch cables, armored fiber trunk cables and field-terminated armored fiber cables for both indoor and outdoor applications.
- Provides excellent crush resistance for outdoor direct burial cables
- Protects cables from rodent biting
- Decreases water ingress into the fiber which prolongs the fiber cable’s life expectancy
Central Strength Member
Strength member is used to increase the tensile force that will be applied on the cable during installation. Strength member will take the pulling force and will keep the fibers safe during installation. For large fiber count cables, a central strength member is often used.
The central strength member provides strength and support to the cable. During fiber optic cable installation, pulling eyes should always be attached to the central strength member and never to the fibers. On fiber splice enclosure and patch panel installations, the cable central strength member should be attached to the strength member anchor on the enclosure or patch panel.
When you choose to use which type of the fiber optic cables, the fiber optic cable construction, along with the mechanical and environment requirements should all be taken into account. All the above materials in the fiber optic cable construction are specifically required to meet the network infrastructure. FS.COM fiber optic cables come in various types with detailed specifications displayed for your convenient. These quality cables are designed with best-in-class performance. For more information about fiber optic cables or patch cords, you can visit fs.com.
With the emerging high-speed network standards and rapidly advancing technology, fiber optic network is driven to meet the growing demand for faster access to larger volumes of data. Although 10G/40G Ethernet becomes the mainstream of telecommunication market nowadays, organizations of all sizes still need to be prepared to integrate speeds of 100G and beyond. For data center networking, users can choose different solutions based on the different transmission distance need. In general, there are two kinds of 100G fiber optic solutions: direct cabling and breakout cabling. It is essential for users to understand the detailed information of each type of solution in order to select the one that meets their current and future connectivity needs.
How 100G Optics Develop
After the IEEE completing the certification of the first 100G standard for Ethernet networks, the transceiver industry launched a new type of form factors for 100G connectivity—CFP (“C” for 100, and FP for Form factor Pluggable). Compared to the most popular 40G QSFP, the size of CFP transceiver is huge. And most CFP implementations doubled the power consumption per bit. Furthermore, the price per bit increased by a factor of ten. These disadvantages becomes the main obstacles of the popularity of 100G CFP transceivers.
The next version of 100G form factors is the CFP2, CFP4, and the CPAK that are improved upon the CFP. But when compared to the popular 10G SFP+ and 40G QSFP+, none of these new members of the CFP family improved density, power consumption, or cost. Fugure 1 shows the size comparison between CFP2, CFP4 and QSFP28 modules.
Then here came the 100G QSFP28. The QSFP28 is the exact same footprint as the 40G QSFP+. The 100G QSFP28 is implemented with four 25-Gbps lanes, Just as the 40G QSFP+ is implemented using four 10-Gbps lanes. In all QSFP versions, both the electrical lanes and the optical lanes operate at the same speed, eliminating the costly gearbox found in CFP, CFP2, and the CPAK. The 100G QSFP28 makes it as easy to deploy 100G networks as 10G networks. When compared to any of the other alternatives, 100G QSFP28 increases density and decreases power and price per bit. That’s why it is fast becoming the universal data center form factor. The following part will move on to talk about the 100G optic cabling solutions.
100G Direct Cabling Solutions
QSFP28 transceiver utilizes either fiber or copper media to achieve 100GbE communication in each direction. This transceiver has 4 individual 25GbE lanes which can be used together to achieve 100GbE throughput or separately as 4 individual 25GbE connections (using 4 SFP28 modules).
For 100G short-reach direct cabling within 100m, 100GBASE-SR4 QSFP28 optical module and 100G QSFP28 cable are good choice. Just from the table list of FS.COM 100G optical modules and cables, we know that 100GBASE-SR4 QSFP28 modules can support up to 100 m on OM4 12 fiber multimode MTP cable. And 100G QSFP28 to QSFP28 direct attach copper cable can support up to 5m and 100G QSFP28 to QSFP28 active optical cable can support up to 10m. Figure 2 describes a 100G direct cabling with the use of QSFP28 to QSFP28 DAC and AOC cables.
For 100G long-haul direct cabling, like 10km, both 100GBASE-LR4 QSFP28 optical module and 100GBASE-LR4 CFP4 transceiver can support up to 10km on single-mode LC patch cables. For longer 100G direct cabling above 10km, the 100GBASE-ER4 CFP is the ideal choice as their transmission distances support up to 40 km.
100G Breakout Cabling Solutions
A breakout cable is a multi-strand cable, typically custom-made, which is divided into multiple duplex cables. For instance, a 40G breakout cable has four individual 10G duplex cables totaling eight strands, while a 100G breakout cable has 10 duplex cables and 20 strands. Figure 3 displays a simple 100G connectivity with 100GBASE-SR4 QSFP28 and QSFP28 to 4SFP28 breakout cables.
Between the 100G optical module and 25G optical modules, there always uses the breakout cables connected the two kinds of optical modules, and the common cable solutions are 100G QSFP28 to 4SFP28 Breakout AOC cables or 100G QSFP28 to 4x 25G SFP28 Breakout Direct Attach Passive Copper Cables.
The commonly used 100G breakout cabling solutions is 100G QSFP28 to 4SFP28 DAC. It’s easy to understand how this type of cable function. Just as the QSFP+ breakout cable, the 40GBASE-SR4 QSFP+ optical module at the one end can be connected to 4x10GBASE-SR SFP+ optical modules at the other end.
As IT infrastructures are planning to migrate to 100G data rate, network designers must carefully weigh alternative implementations of such links. With a variety of fibers already deployed, it is important to understand the interoperability of new optics with existing fibers. And for 100G deployment, you are supposed to understand the benefits and challenges of each type of the fiber optic solutions before taking an action. FS.COM’s 100G FHD series covers a full range of 100G optical transceivers and cables, like CFP, CFP2, CFP4, QSFP28, as well as 100G QSFP28 to QSFP28 DAC, 100G QSFP28 to 4SFP28 DAC. Besides the above products, 100G FHD Fiber Enclosures, 100G FHD MTP Modular Cassettes, 100G 160 Fiber 2U Panels and 100G CFP SR10 Cables are also provided. If you want to know more about our products, please contact us directly.
Without denying that the market for 100G data center optics is accelerating, and more and more telecommunication vendors are aiming to seize this opportunity to launch cost-effective 100G solutions. FS.COM also offers a series of 100G optical modules and cabling solutions that are compliant to the IEEE standards. Our 100G optical modules support different transmission distance from 100m, 10km and more reach options in CFP and QSFP28 form factors. Before introducing the FS.COM 100G optical modules, let’s firstly talk about the 100 Gigabit Ethernet standard.
IEEE 100GbE Standard Introduction
Defined by the IEEE 802.3ba-2010 standard, 100 Gigabit Ethernet (100GbE) technology was given birth to transmit Ethernet frames at the rates of 100 gigabits per second. The 100G optical modules are not standardized by any official standards body but are in multi-source agreements (MSAs). The major 100Gigabit Ethernet 100GBASE-R optical module standards are briefly listed in the below table.
According to the above table, the 100GBASE-CR4 and 100GBASE-CR10 standards were met by twinax copper cable with a link length of 7m. The 802.3bm standard was approved in 2015, which specifies a lower-cost optical 100GBASE-SR4 PHY for multimode fibers (MMF). The 100GBASE-SR4 standard can operate over OM3 MMF for a link length of 70m, and transmit over OM4 for a link length of 100m. QSFP28-100G-SR4 is one of the common types of the 100G modules, which can be used in 100 Gigabit Ethernet links on up to 100m of OM4 multimode fiber.
For those infrastructure who require a link length longer than 2 km, 100GBASE-LR4 and 100GBASE-ER4 standards were introduced. These two standards are specially designed for use in long haul applications. For example, QSFP28 100GBASE-LR4 optics can support a distance of 10km, and the CFP 100GBASE-ER4 operate over single-mode fiber for a distance of 40km.
As for the 100GBASE-SR10 or 100GBASE-CR10, the 10×10 MSA was intended as a lower cost alternative to 100GBASE-SR4 for applications, which defines an optical Physical Medium Dependent (PMD) sublayer and establish compatible sources of low-cost, low-power, pluggable optical transceivers based on 10 optical lanes at 10 Gbit/s each.
FS.COM 100G Optical Modules
FS.COM provides 100G QSFP28 optical modules, including 100G QSFP28 SR4, 100G QSFP28 LR4 as well as 100G CFP LR4 optical module. All these 100G transceivers are good choice for today’s high-density data center 100G interconnection and networking.
- QSFP28 100GBASE-SR4
The QSFP28 100GBASE-SR4 transceiver, based on the QSFP28 from factors, is a parallel 100G optical module designed with optical/electrical connection and digital diagnostic interface. It offers 4 independent transmit and receive channels, each capable of 25Gbps operation for an aggregated data rate of 100Gbps for 100 m on 12-fiber MPO/MTP OM4 multimode fiber.
The QSFP28 SR4 module is a vertically integrated solution that meets IEEE 802.3 standards and MSA requirements with power dissipation well under 3.5W. It supports both 100GBASE-SR4 as well as 4x25G breakout applications, 100G QSFP28 to QSFP28 DAC and 100G QSFP28 SR4 to 4x25G SFP28 break-out cables, meeting the harshest external operating conditions including temperature, humidity and EMI interference.
- QSFP28 100GBASE-LR4
The 100GBASE-LR4 QSFP28 transceiver, compliant to 100GBASE-LR4 of the IEEE P802.3ba standard, is also a 100Gbps transceiver module designed for long-reach communication applications. This module converts 4 input channels of 25Gbps electrical data to 4 channels of LAN WDM optical signals and then multiplexes them into a single channel for 100Gbps optical transmission. The high performance cooled LAN WDM EA-DFB transmitters and high sensitivity PIN receivers provide superior performance for 100GbE applications up to 10km links over single-mode fibers.
FS.COM 100G Optical Modules
According to the market researchers, the 100G optical transceivers market will be booming in the near future. So what are you waiting for? It is the ideal time for data center designers to prepare for the data center networking and architecture beforehand with 100G transceivers and cables. Contact us for the available 100G optical modules: 100G QSFP28 SR4, 100G QSFP28 LR4, 100G CFP, CFP2 and 100G CFP4 optics. Besides 100G optical modules, FS.COM also provides 100G cable solutions like 100G active optical cable (AOC) and 100G direct attach cable (DAC). You can have what you need here.