Månadsvis arkiv: September 2016
There is no doubt that fiber optic cables play an integral role in telecommunication industry. Applications like data centers, local area networks, telecommunication networks, industrial Ethernet, and wireless network are all needing fiber optics to ensure smooth connectivity. Each application requires a specific cable design based on performance requirements, environmental conditions, and installation type. The common fiber optic cables like LC to LC patch cord cannot adapt to the harsh environment (e.g. moisture environment or underground deployment), thus water-resistant fiber optic cables are highly demanded on the market due to their water proof nature. Here is what you should know about the water-resistant fiber optic cable.
Overview of Water-resistant Fiber Optic Cables
Water-resistant fiber optic cable refers to the special type of fiber optic cable that are designed and specified for installations where the cable will come in contact with water or moisture, such as aerial, direct buried, or in conduit. The cables in these applications are exposed to or can be temporarily submerged in water, so they contain either a water-resistant gel-filled or gel-free (dry gel) polymer.
Generally, fiber optic cables can be divided into three types—outside plant cable (OSP), indoor/outdoor, and indoor, which are specified based on the environment and location where they are installed. With the exception of indoor cables, all cables contain water-resistant gel-filled or gel-free material to protect them from water and moisture. Before the use of gel-filled and gel-free materials, flooded core was another water-blocking method that is rarely used today (it has been replaced with gel-filled). The following image shows the gel-filled cables.
The gel is a gooey substance that must be removed when accessing and installing the cable. Gel-free cables, which are now more widely used, contain a super-absorbent polymer powder that is activated when it comes in contact with water or moisture. This blocks the water from penetrating the cable and allows for some expansion and contraction with temperature changes. Indoor cables do not contain water-resistant material since they are not typically exposed to water. Indoor (and indoor/outdoor) cables must meet additional flammability requirements dictated by local codes, such as the National Electrical Code.
Tight-Buffered & Loose Tube Cable Construction Provides Excellent Moisture Resistance
Water-resistant materials and cables are included in many industry specifications and standards. Generally, there are two basic water-resistant cable designs: Tight-buffer cables (primarily used inside buildings), Loose tube cables (used for OSP and indoor/outdoor).
It is known to all that most tight-buffered cable designs (seen in image below) are specified for indoor use, but some of them are designed with water-resistant powder and yarn, making them suitable for some indoor/outdoor applications. This tight-buffered cable utilizes an different design approach to deal with the moisture issue. Buffer materials are low-porosity plastics with excellent moisture resistance. This construction very effectively minimises the water molecule and OH-ion concentration level at the glass surface and virtually eliminates the stress corrosion phenomenon.
In loose tube cables (seen in image below), in order to prevent the water from reaching the 250μm coated fibers, the tubes surrounding the fibers must be filled with water-absorbent powder or gel that withstands high-moisture conditions, making them excellent for outside plant applications. This approach is especially made to waterproof the cable by filling the empty spaces in the cable with gel. The gel-filled tubes can also expand and contract with temperature changes, which makes loose-tube cable great for harsh, high-humidity environments where water or condensation can be a problem. However, gels can move, flow, and settle, leaves an uncertainty of the filled level of any particular point of a loose-tube gel-filled cable. Because loose-tube cable is typically 250 microns, you’ll need a fan-out kit to build up the individual fiber strands to 900 microns when making the transition at the entrance point from outdoor loose-tube to indoor to tight-buffered cable.
The same level of protection remains in place all along the fiber, regardless of installation conditions, environment, or time. The balance of the tight-buffered, tight bound cable designs is such that it minimizes the open spaces available in the cable structure in which water can reside. Even if an outer cable jacket is cut, or water otherwise enters the cable structure, only a very small percentage of the cross-sectional area is open to water.
When selecting the suitable fiber optic cables, one must consider the application, the installation location, and the appropriate cable design and type according to specifications and standards. The water-resistant optic cable is specially made for moisture environment to insure the smooth connectivity. However, whether to have the loose tube fiber optic cable or tight buffered cable, it depends on the installation location. FS.COM offers a full range of fiber optic cables at very economical rates. These cables are widely used and are highly demanded on the market due to their water proof nature. In addition to this, we offer these cables in various fiber optic cable specifications, such as duplex/simplex fiber cable, single-mode/multimode fiber optic cable, LC/FC/SC/ST fiber optic cable and so on. LC to FC patch cord is absolutely high quality and low price, just as the other fiber optic cables. If you want to know more about our products, please contact us directly.
Data center nowadays are migrating to high-bandwidth, high-density network infrastructure. This increased network speeds have tighter link budget requirements that can be challenging to achieve with field terminations. Pre-terminated cabling includes a variety of trunk cables, array cables, and plug and play cassettes that gives data center managers options that suit specific needs. Besides this, there are several reasons to consider pre-terminated optical fiber in data center solution. The following image shows the pre-terminated UTP cassettes.
No Need to Test the Network Performance
With pre-terminated cable assemblies, transmission testing of assemblies is performed by the manufacturer before shipment, and test reports are included with the assemblies. This leaves only continuity testing for copper and 10% insertion loss and continuity testing for fiber, which reduces the time spent testing on-site.
With pre-terminated solutions, data center managers can make changes quickly based on network growth, business decisions, or shifting requirements. In disaster recovery situations that call for fast, temporary data communications set-up, pre-terminated cabling can minimize business downtime and establish communications quickly. It can also be disassembled quickly when the situation is resolved. The components are reusable for more efficient moves, adds, and changes (MACs).
Fast and Simple Deployment
Field termination is the most time-consuming, labor-intensive part of the cable installation process. Once pre-terminated cabling is delivered, it can be unpacked, readied for deployment, and connected quickly. In many cases pre-terminated cabling can cut installation time by up to 80% over field terminations.
Additionally, precision factory-termination processes take place in a clean, well-lit environment, unlike termination in uncontrolled field conditions. This increases the likelihood of clean and uncontaminated optical fiber ports, enables lower loss budgets, and provides overall better electrical transmission. Factory terminations are also guaranteed under warranty, which offer data center managers peace of mind.
Pre-terminated solutions allow for quick clean-up due to minimal leftover materials and scrap. Also, because there is less waste and material to clean up, pre-terminated solutions also help meet green design, waste reduction, and material reuse goals. Additionally, pre-terminated solutions provide an easy way for network managers to proceed a routine check.
If you are making up your mind to deploy a pre-terminated system, one thing you shouldn’t miss is that the planning process typically requires more time upfront and more detailed analysis to determine specific cabling and termination routes along the cable trays and within the cabinets. Once the detailed plan is formulated and approved, the system’s cabling and connectivity components are manufactured and tested at the factory to ensure they meet all applicable industry standards prior to delivery. The next part will go on to talk about the how to select the suitable pre-terminated solution.
How to Choose the Pre-terminated Cable
Pre-terminated cabling solutions are ideally suited for data center environments where the cable routes are well defined and where the time for deployment, ease of installation, network reliability and manageability are paramount. When selecting pre-terminated cable assemblies, be sure to use a reliable provider that can offer services such as guaranteed cabling performance, design assistance, certified contractor training, and the ability to support large quantities of assemblies in the required delivery window. Make sure the pre-terminated copper or optical fiber purchased through a manufacturer uses components that have been tested and verified by a third party to exceed TIA and IEEE standards. The manufacturer should also provide 100% testing in a quality-controlled environment before the cabling is shipped out to the worksite.
Pre-terminated cables are the plug-and-play solution for links between switches, servers, and patch panels in the data center. As the computing environments and business needs of organizations differ widely, not every enterprise will find the benefits of pre-terminated systems outweigh the investment. Field-terminated copper and fiber cabling and connectivity systems are generally less costly to purchase in terms of the various components. Just to find a suitable solution system for your own network. Providing reliable quality, advanced testing system and favorable price, progress of FS.COM has never stopped. We offer a variety of pre-terminated optics including the breakout patch cable, pre-terminated trunk cable and adapter panels. Fiber optic cables like SC fiber patch cable and LC to LC patch cord are also needed. If you have any requirement of our products, please send your request to us.
Alien crosstalk refers to the noise that may occur in a cable that runs alongside one or more other signal-carrying cables. It is the combination of alien near-end crosstalk (NEXT) and alien far-end crosstalk (FEXT). The alien acrosstalk between fiber jumper cables reduces the operational bandwidth of a cabling solution due to an increased level of crosstalk noise decreasing the overall signal-to-noise ratio (SNR). This additional reduction in operational bandwidth are posing threat for the performance of network infrastructure, especially for the higher-bandwidth applications. Therefore the ANSI/TIA/EIA standard committees are proposing that new NEXT and attenuation limits be considered. This pose briefly introduce some things about alien crosstalk (AXT), and the way to measure it.
Alien crosstalk is the coupling of noise from one cable link to another. This happens if one cable is surrounded by many other cables in a bundle. Alien crosstalk can be particularly troublesome because, unlike the simple crosstalk caused by a single interfering signal, it cannot be eliminated by phase cancellation. As noted before, alien crosstalk in high-speed application is far more severer than in lower-bandwidth infrastructure. The following image shows the Alien crosstalk coupling between pairs of wires of the same color in a UTP (unshielded twisted pair) cable.
Gigabit Ethernet (GbE) technology uses an encoding method of transmitting data on all four cable pairs simultaneously and in both directions. This method is demanding on the cabling infrastructure, which might be resulted in alien crosstalk being generating within adjacent, parallel, unshielded twisted-pair (UTP) cables. People usually have the misconception that if they use shielded cables, then alien crosstalk would not be a problem. However, if the shield is not terminated correctly even a shielded system can fall foul of alien crosstalk.
How Do We Measure AXT?
Since the alien crosstalk had really bad influence in network performance, attempting to control alien crosstalk through cable design and cable installation would be a great changer to guarantee the installed network performance. In all, there are three methods that can help to control the alien crosstalk:
- Through cable design by decreasing the combined sources of noise (NEXT, FEXT, and return loss) within the system, effectively increasing the overall SNR.
- Through installation control by ensuring cables are not installed in such a way as to exacerbate the problem. This approach would preclude the use of bundled UTP cables, overfilling of conduits and trunking, or close-proximity parallel cable runs.
- Through the use of screened, balanced, twisted-pair cables.
Thanks to the above methods, we might have a chance to minimize the alien crosstalk. But we still have the need to know how to test alien crosstalk. Typically we test alien crosstalk between each pair of each disturber to each pair of the disturbed in a cable bundle. Two solutions in use today are based on test devices connecting the victim and disturber cables under test, respectively a communication channel between the devices. The following example uses the Fluke DSX-5000 testers to measure the alien crosstalk.
For near-end alien crosstalk testing, the main unit is connected to the victim channel, and the remote unit is connected to a disturber channel. we identify the potential Disturbed cable that is surrounded by Disturbers, not including cables’ connectors that are adjacent to gaps. For Disturbers, we pick cables in the same bundle that surround the Disturbed cable. These are the cables where the connectors are likely to cause the majority of the ANEXT. The connector shown in green identifies a potential good disturbed cable connector.
We make an ANEXT measurement with the Master unit of the DSX-5000 connected to the Disturbed (victim) at the near-end with a terminator at the far. The DSX-5000 remote unit is connected to the near-end of the Disturber with a terminator attached at the far end. The Master unit and remote are then connected together via the RJ45 communication ports to enable them to synchronise the tests being made. The measurements are then made on the Disturbed (Victim) as above for each Disturber.
Alien Crosstalk also requires a measurement to be made from the far-end. This is the PS AACR-F (Power Sum Alien Attenuation Crosstalk Ratio Far End) measurement. This is performed in the same way as PS ANEXT but the setup is different. The Main unit is connected to the Disturbed cable connector as before. However, the remote unit is connected at the far end and the terminator at the near end as in the diagram below. In addition, the communication cable between the master and remote unit is connected through one of the horizontal RJ45 links.
During the whole testing no matter the ANEXT or the far-end AXT measurement, the Main unit of the DSX-5000 tester remains connected to the Disturbed (Victim) cable. Each time a measurement of Disturbed (Victim) is completed for one Disturber, the remote unit and the terminator are moved to the next Disturber to make the next test, this is continued until all the Disturbers in the bundle have been measured for that Disturbed cable.
Alien crosstalk measurement setup is more complex than that of general crosstalk testing. Because the alien crosstalk should be executed for a bundle of cables (at least six cables). Furthermore, more test instruments are needed for alien crosstalk, except for the Fluke DSX-5000 tester. Therefore, whether to go for a PSANEXT or ANEXT measurements, this might be a time-consuming and troublesome process. FS.COM is a professional telecom manufacturer. We not only supply plenty of optical products, such as fiber patch cables (ST-LC patch cord), transceiver modules, or DAC/AOC cables, etc, but the best services to all of our customers. If you have any doubt about today’s topic, you are always welcomed to contact us.
The rapid development in data center throughput has led to the increasing usage and demand for higher-performance servers, storage and interconnects. And the old 1G Ethernet cannot handle the heavy-loaded solutions in data center any more. As a result, datacenter designers are looking to the expansion of higher speed Ethernet solutions, specifically 10 G and 40G Ethernet. As for 10GbE, there are two broad categories—SFP+ optical options and 10GBASE-T available on the market, which pose difficulty in selecting the appropriate 10-gigabit physical media. This article will make a brief introduction to these two 10G solutions to help you choose the suitable one.
What Is 10G SFP+?
10G Small-form-factor pluggable plus (SFP+) is the industry standard for data rates up to 10 Gbps, which is also MSA compliant. SFP+ module is especially standardized for 10 Gbps application, and is identical in dimensions to the SFP. To achieve the SFP+ form factor reduction, only the optical-to-electrical and electrical-to-optical conversion functionalities occur inside the optical module. The key advantage of SFP+ over the existing 10 G optical interconnects is the higher port densities enabled by its dimensions, and lower power consumption. Figure 1 shows a SFP+ modules connected with a LC to LC patch cord.
SFP+ transceivers are available in different 10G Ethernet standards—10GBASE-SR, 10GBASE-LR, 10GBASE-LRM, 10GBASE-ER, 10GBASE-ZR, 10GBASE-LX4 and 10GBASE-PR. Each standard has a unique specification that can be suitable for different applications. SFP+ optics are selected more often when designers need faster and more reliable solutions to handle 10 Gigabit Ethernet optical lines. With lower power usage and low latency, SFP+ ports are most commonly used for enterprise switches and also for plug-in cards for servers.
How Does 10G Copper Solutions Compare?
10G Ethernet can also run over twin-axial cabling, twisted pair cabling, and backplanes. SFP+ direct attach cable, 10GbASE-CX4 and 10GBASE-T are the common copper solutions for 10G short-reach interconnect. 10GBase-CX4 achieves the aggregate rate of 10 Gbps by transmitting over four independent cables at 3.125 Gbps. The disadvantage of this solution is the bulkiness of the cables that have eight twin-ax cables within them for a duplex link. And the bulkiness of the cables makes cable management more difficult. This becomes a significant limitation as the port densities and inter-port connection densities increase. Additionally, the number of conductors make these cables expensive compared to SFP+ cables.
10GBase-T enables 10 Gbps transmissions over Cat 6 and higher quality cables using complex signal processing and channel coding. The potential advantage of this technology is its extended reach. The extended reach and ability to enable structured cabling are not required for the short reach interconnects between servers and switches collocated in a rack. The disadvantages are its high power consumption and latency. The high latency in particular is a key limitation in latency sensitive data center and storage applications.
SFP+ Direct Attach DAC is another lower cost alternative to fiber with a limited link length of 7 meters. Additionally, it has significant power, cost, and performance advantages over the above media as explained below.
Why Use 10G DAC Cables in Data Center?
As 10 Gbps interconnects become ubiquitous in servers, providers are looking for a low cost, low power, and space efficient interconnect solution for the short reach (5-7m) links that dominate the data center environment. A length of seven meters covers all connections between server cards and switches, typically mounted on a single data center rack, and a vast majority of inter-rack connections. The SFP+ Direct Attach Copper is the 10G interconnect technology that matches these requirements, playing a vital role in enabling the next generation power and cost efficient data centers.
SFP+ Direct Attach Copper Solution
To further reduce cost and power in interconnect distances of 7 meters, which is sufficient to link server cards and switches, the SFP+ Direct Attach Copper replaces the optical modules and fiber with a passive copper cable with connectors identical to an SFP+ optical module. Figure 2 shows a SFP-H10GB-CU3M plugging in a Cisco switch. The reduction in cost and power are significant since the price of two optical modules required to support a full duplex link is approximately 10 times the cost of a fully connectorized SFP+ Direct Attach cable. In addition, the optical SFP+ modules consume around 1W each, adding 2W per port to the overall system power budget and cooling requirements.
Data is transmitted as 10 G serial NRZ (Non Return to Zero) symbols with transmit pre-emphasis and receive equalization compensating for Inter Symbol Interference caused by the board trace and the copper cable. This choice of serial NRZ transmission over a passive medium makes SFP+ copper both a low power and low latency solution compared to its alternatives.
As more emphasis is placed on energy efficient data centers and higher bandwidth applications, the need for a small form factor, low power, low latency and low cost interconnect makes SFP+ Direct Attach the optimal solution for short-reach 10G interconnects. While SFP+ fiber options provides a great path for higher performance long haul applications. FS.COM is a top manufacturer for DAC Twinax cables (SFP+ Cables, XFP Cables, CX4 Cables, Infiniband Cables, etc) and best suppliers for QSFP+ products including 10G & 40G QSFP+ copper and AOC cables. Optics transceivers like QSFP+, SFP, SFP+, XFP, X2, XENPAK, SDH, Bidi are also offered. If you have any interest in our products, you can contact us directly.