Guide to Bend-insensitive Multimode Fiber

četvrtak , 07.07.2016.

A common problem facing cabling installers during installation or other fiber handling is the light losses or weaker optical signal, which is cause by the fact that when a fiber bend radius exceeds the specified figure, the angle at which the light hits the cladding changes and some light will escape and result in power loss. It’s known that light losses is the commonplace found in fibers, like LC-SC multimode fiber patch cord. In 2009, bend-insensitive multi-mode fiber (BIMMF) has been introduced, which can withstand tight bends, or even kinks, or other withstand tough treatment without suffering significant light losses in many cases. It seems to be an ideal product. How much do you know about it? Have some ideas about its working principle, its compatibility, its testing issues? Follow this article and find answers.

BIMMF Working Principle
An introduction to the working principle helps you to understand how BIMMF reduces signal losses with its bend-insensitivity and becomes the preferred choice in data center applications.

BIMMF technology prevents light from escaping. BIMMF has an innovative core design that incorporates a graded-index core profile combined with a specially engineered optical trench. A specially engineered optical trench (image below) is used to trap the light in the many modes which propagate within the fiber core. The trench, or also called moat, with low refractive index, surrounds the core in BIMMF to reflect lost light back into the core. It acts like a barrier for propagating light. Keeping the light in the core, even in the most challenging bending scenarios, significantly reduces the bend-induced. The trench is just an annular ring of lower index glass surrounding the core with very carefully designed geometry to maximize the effect.

BIMMF Compatibility Issues
One question with BIMMF is whether it’s compatible with conventional fibers. Can they be spliced or connected to other conventional (non-BI) fibers without problems? How does the inclusion of higher order modes affect bandwidth?

Measurement of core size, NA, differential mode delay (DMD) and bandwidth were developed prior to the introduction of BI MMF designs. These measurements are in the process of being evaluated and updated, so measurement results may depend on the manufacturer of the BIMMF. For the most part, it appears that BIMMF can be made to be compatible to other non-BI fibers by modifying the core design slightly or careful engineering of the trench surrounding the core, but at this point it is left to the manufacturers to show their product will perform equivalently to the installed base of fiber.

When short lengths of BIMMFs are measured, they may have a larger effective NA and core size than conventional MMFs since they propagate "leaky modes" that are attenuated in conventional fiber designs. This may affect splice or connector loss when mating BIMMF with conventional MMF but usually only in one direction, from BIMMF to conventional MMF, in a manner similar to the losses from mismatched fibers.

BIMMF Testing
Testing BIMMFs or using them for reference cables for testing is another matter. For testing, link set ups included both all BIMMF channels and mixed links using a combination of BIMMF assemblies and standard nonBIMMF assemblies. 10G and 40G testing used full duplex traffic with two transceivers (e.g. E10GSFPLR or QFX-QSFP-40G-SR4), and this approach is necessary, since the trunk cables contain only 12 fibers and per the standard, and full duplex traffic at 100G requires 20 fibers. The channel configurations for the various active tests are shown below.


BIMMF Advantages & Design Challenges
This kind of cable has obvious advantages. In patch panels, it should not suffer from bending losses where the cables are tightly bent around the racks. In buildings, it allows fiber to be run inside molding around the ceiling or floor and around doors or windows without inducing high losses. It's also insurance against problems caused by careless installation.

However, BIMMF profiles pose a complex design challenge. Profile parameters must be carefully selected to ensure all key attributes satisfy all relevant industry standards. Bandwidth is a key parameter for MMFs and the graded-index profile remains a key driver to achieve high bandwidth. Any deviation from the optimum profile results in reduction of bandwidth of the MMFs. Inappropriate trench location can result in delay errors of the higher-order modes, and this can significantly impair bandwidth performance. Locating the trench too far from the fiber core can result in failure to comply with fundamental industry standards. The fiber's trench location must be carefully engineered to ensure superior bandwidth and macrobend response while maintaining industry standard requirements for core diameter, numerical aperture and chromatic dispersion.

Conclusion
BIMMF is fully compliant with the OM3 and OM4 standards for laser-optimized fibers, and is also backward compatible with the installed base of 50-Ľm MMFs. With its improved bend -sensitivity, BIMMF allows for less light losses in the stressed section of the fiber, reducing the challenges encountered in installations in local area network (LAN) data centers.

Oznake: MMFs, BIMMF, LC-SC multimode fiber patch cord, BIMMF testing, transceivers, E10GSFPLR

Fiber Optics: Do You Know Its History & Advantages?

srijeda , 22.06.2016.

As we all know that the medium is considered as the simplest form of fiber optics, which is used to carry information from one point to another in the form of light. It's comprised of a transmitter used to generate the light signal, a fiber optic cable that functions as a conduit for pulses of light to travel over distances,, and a receiver to accept the light signal transmitted. In practical use, fiber systems are often deployed as the alternative solutions to traditional copper-based communications systems, since fiber optic cables outperform copper cables in less signal loss and immunity to electromagnetic interference (EMI). Of course, the advantages of fiber optics are denifinely not confined to these two points. Read this article and the following detail the several strong points of fiber optics used in communication systems, as well as its history.

Fiber Optics: History
In 1880, the photophone was invented, a great inventory used to speak into a microphone which would then cause a mirror to vibrate. The sun's light would strike the mirror, and the vibration of the mirror would transmit light across an open distance of about 656ft (200m). The receiver's mirror would receive the light and cause a selenium crystal to vibrate, causing the noise to come out on the other end. Although the photophone was successful in allowing conversation over an open space, it had a few drawbacks: it did not work at night, in the rain or if someone walked between the signal and receiver. Then this idea was given up.

In 1950s, the laser was invented. This device was a finely controlled beam of light that could transmit information over long distances. Unfortunately, the same drawbacks also plagued the laser. Although it could be used at night, it did not work during rain, fog or at any time when a building was erected between the sender and the receiver.

Scientists at Corning developed the first practical fiber optic cables in the 1970s, based on the idea of "total internal reflection". This is the principle that fiber cables are built upon, and it basically means that an optical fiber consists of a core of transparent glass, surrounded by outer layer, (called "cladding") of slightly less transparent glass which reflects the light back into the core.

What Makes Fiber Optics Special?
What is special about fiber optics? As mentioned above, fiber optic cables are made out of glass, and carry pulses of light energy. The idea of a flexible piece of glass sounds a bit counter-intuitive, but in some ways, fiber optic cables are stronger and more durable than copper cables.

Nowadays, fiber optic cables are used for many different telecommunication applications, like data centers, data warehouses, server farms, SANs, and LANs. But actually, in their practical use, there exists a common question. One may find himself faced single-mode fibers (SMFs) and multi-mode fibers (MMFs) which are terminated with different connectors, such as LC (LC fiber cable), SC (LC to SC cable), MTP/MPO (MTP cable). When such things occur, it’s important to keep in mind that SMFs and MMFs are not compatible with each other, and can't mix them together between two end points.


Fiber Optics: Advantages
Why is fiber optics used in telecommunications? There are several reasons that make fiber systems more popular than copper ones.

Large Bandwidth & Long Distance
Bandwidth refers to the amount of data that can be passed along a cable in a given time period. If we think of cables as pipes, then bandwidth is the amount of water that can flow through the pipe in a second. The bigger the pipe, the more water can flow. Consider a normal communication cable that may be used to carry a single phone call. It is built out of copper, and may have the bandwidth of a normal drinking straw. By comparison, a fiber cable of the same physical size would provide more bandwidth.

Since fiber optic signal is made of light, very little signal loss occurs during transmission, and data can move at higher speeds and greater distances. In most cases, copper cables are limited to a range of 100meters or less. In contrast, the relatively small diameter and light weight of fiber optic cables can allow a wide range of distance reaches from 550meters to dozens of kilometers, which makes fiber ideal for applications where signals have to travel over long distances.

Immunity & Reliability
Fiber optics provides extremely reliable data transmission. It’s completely immune to many environmental factors that affect copper cable. The core is made of glass, which is an insulator, so no electric current can flow through. It’s immune to electrometric interference and radio-frequency interference (EMI/RFI), crosstalk, impedance problems, and more. You can run fiber optic cable next to industrial equipment without worry. Fiber is also less susceptible to temperature fluctuations than copper and can be submerged in water.

Security
The data is safe with fiber cable which doesn’t radiate signals, letting information difficult to be tapped. More specifically, the dielectric nature of fiber optic cable makes it impossible to remotely detect the signal being transmitted within the cable. If the cable is tapped, it’s very easy to monitor because the cable leaks light, causing the entire system to fail. If an attempt is made to break the physical security of your fiber system, you’ll know it. Fiber networks also enable you to put all your electronics and hardware in one central location, instead of having wiring closets with equipment throughout the building. They are very attractive for use in governmental institutions, finance/banking and other environments with major security concerns.

Summary
It's obvious that fiber optics has a growing usage in both private and public networks. It's able to transmit signals over significantly distance at high speed and large amount, extremely suitable for voice and data links. As an outstanding fiber patch cord manufacturer, Fiberstore provides various kinds of fiber optic cables terminated with the same or hybrid connectors on the ends to cover countless applications, including the above mentioend LC fiber cable, LC to SC cable, MTP cables, and so on. They are all supplied at cost-effective prices. Really worth your try.

Oznake: fiber optic cables, LC to SC cable, LC fiber cable, SMFs, MMFs, fiber patch cord manufacturer

Three Factors That May Destroy Fiber Optic Cables

srijeda , 06.04.2016.

Fiber optic cable, which has become the essential component of nearly all modern computer and communications systems nowadays, has been deployed all over the world. Where there is a city, there are thousands of fiber optic cables connecting people to the networking systems. Without them, it’s hard get the information in real time. But there is a problem that once the fiber optic cable is damaged or cut, it may cause a big loss because of the network disruption. And we know that fiber optic cable is made up of pure glass, in some cases, it may be very fragile. This article gives you three factors that may destroy the cables.

Environment
The environment is the first thing you should take into consideration. Because in the extreme weather conditions, such as hurricanes, mud slides, flood and ice storms, ect., fiber optic cable would suffer great damage. If water enters, a splice enclosure can freeze, then this will crush the fiber strands and leave you with a costly network outage. Additionally, lightning is also a factor to destroy fiber cables. When lightning strikes the ground, it will search for the best conductor available, even if it’s underground. If that happens to be the armor or trace-wire of your fiber cable, then damage to the cable sheath and even the fiber itself is very likely.

Human’s Destruction
Here human refers to the people who steal the fiber. They cut the fiber thinking it has value and can be sold in pieces. The most classical event is that a 75 year-old woman in Georgia (country in Asia) was digging with her spade, looking for copper, which she wanted to sell for scrap, when she accidentally cut the fiber optic cable that provided internet to 90% of Armenia. It is ridiculous. It is fiber but not copper! In addition, people vandalize the fiber cable in other ways, e.g. for gun practice. This especially happens in the rough parts of town which makes the cable repair work become dangerous. Furthermore, land disputes which cause artificial malicious damage of fiber are also a fiber damage reason.

Animals Chew & Bite
We can try to reason with humans and publicize our buried fiber cable, but there is nothing we can do about the cable damage causing by animals. Squirrel, a furry little nut eater, seems to be deeply fond of fiber cable sheathing besides nuts. We even doubt that the cable manufacturers of using peanut oil in the sheathing. Since they have a life-long drive to gnaw, squirrel is often responsible for extensive damage to fiber optic cable. Even metal armored cable can get cut in two by this furry critter. In addition, undersea cables aren’t exempt from cuts. Because there is another kind of animal under ocean that is likely to bite cables. It is shark. Why shark would like to eat fiber cables? Effect by magnetic fields is one of the explanation at present. We have no idea how we can combat these wayward rodents. Now, only thing we can do is always looking for ways to improve.


Notes on the Use of Fiber Optic Cables
After mentioning three common factors that may do harm to fiber cables, there goes the basic information about the use of fiber cables and their related fiber optic transceivers.


Fiber cables are used as the transmission medium of fiber optic transceivers for high data-rate transmission in gigabit applications, with distance reaching from only several hundred meters on multi-mode fibers (MMFs) to 10km, 20km, 40km, 80km on single-mode fibers (SMFs). Take Gigabit Ethernet (GbE) applications for example, when 1000BASE-LX SFPs (eg. MGBLX1) work through SMFs, 10km link length is made possible; and 1000BASE-SX SFPs (eg. MA-SFP-1GB-SX) operates via OM2 (MMF), the possible distance reach is 550m. So when you choose fiber optic cables for fiber systems, it’s necessary to figure out what the distance reach is required first, and then you can deploy the right fiber cable type for different applications.

Conclusion
So after you obtain a good understanding of the three factors that may destroy the fiber optic cables, you must master how to protect the cables. Now, waterproof fiber cables, armored fiber cables and the other outdoor cables which are designed to protect fibers in a harsh application environment are widely used in this field. You can buy these fiber optic cable as well as the related fiber optic transceivers (MGBLX1, MA-SFP-1GB-SX, etc.) in Fiberstore which are really reliable. Any questions, please let me know.

Oznake: fiber optic cable, SMFs, MGBLX1, MMFs, MA-SFP-1GB-SX