Several years ago, OS1 fiber optic cable was the only one standard for single-mode fiber with the maximum link length for campus cabling around 10km, but 10km can no longer satisfy people’s increasing needs nowadays. Therefore, OS2 fiber that can support much longer distance than 10km has been widely utilized in telecommunication industry. But there has been some debate and confusion as to the differences between OS1 and OS2 fiber types and what the terminology actually means. Thus, the following article is provided to assist the users in understanding the differences between OS1 and OS2 fiber types. The following image shows the LC to LC fiber patch cable single mode plugging in a switch.
OS1 and OS2 Single-mode Fibers
Firstly, OS in the term OS1 and OS2 specifications refers to the Optical Single-mode fiber. Single-mode OS1 is indoor tight buffered fiber. An OS1 cable could be a micro-core LSZH indoor cable that consists of 250 micron fibers, with the fibers being tightly enclosed in a cable with aramid strengthening yarn and a LSZH jacket. The attenuation of a OS1 fiber is higher than an OS2 fiber. From the above table, the maximum attenuation allowed per km of installed cable is 1.0 dB for OS1 for 1310nm and 1550nm, while the maximum attenuation allowed per km of installed cable is 0.4 dB for OS2 for 1310nm and 1550nm.
Single-mode OS2 is an outdoor loose tube optical fiber cable, which is suitable for outdoor applications where the cabling process applies no stress to the optical fibers. For instance, a 250 micron coated multi-fiber, which is loose inside an enclosure or tube and/or is free to move, is classified as OS2.
OS1 or OS2 performance cables are constructed from B1.3 optical fibers (or ITU specification G.652D). Furthermore, OS1 and OS2 cable types can also include cables manufactured from B6_A fiber, which is commonly known as bend insensitive single-mode optical fiber, or ITU specification G657A2 (compatible with B1.3 optical fiber). OS1 or OS2 single mode fiber performance, does not relate to ITU specification G.655 (Non-dispersion shifted single mode optical fibers.
Why Should We Use OS2 Over OS1 Fiber?
Single-mode fiber was mainly used for long-hual applications but not marked as a cost-effective investment for future application in building. One reason is that the single-mode related products like cables and optical transceivers are offered with high price. The other is that with the price decrease of the VCSEL or laser power source, the performance gap (namely link length) between multimode or single-mode fiber is smaller everyday.
Considering this, why not use the best single-mode fiber (OS2) to create better performance and ready for high speed data networks? Besides the difference in link distance, OS1 and OS2 fibers have different attenuation—OS2 has two times less losses than OS1 fibers. And in CWDM or DWDM network, OS1 has poor result in the wavelength range called E-band or water peak band, which makes it not suitable for the WDM-based network.
Figure 3: CWDM wavelength allocation and fiber loss. The solid line represents OS2 fibers. The dotted line represents the water peak.
Another good news is that if you use OS2 fiber, it will be more suitable for you to support the IEEE 802.3 multiplexed series (40G BASE-LR4 and 100G BASE-ER4). You even don’t need to change your existing OS1 fibers, as the OS2 can be mixed with OS1 in the same link. What’s more, active or passive component for OS1 like connectors, adapters also works with OS2.
To sum up, OS1 optical fiber is appropriate for indoor and universal tight buffered cable constructions, which are mainly deployed in internal building/campus networks, as well as internal cabling within telecommunication exchanges and data centers. While OS2 optical fiber is appropriate for outdoor and universal loose tube solutions, which would include external plant and most back-haul networks. Therefore, when deciding which single-mode optical fiber type to specify, consider the application as well as how and where the cable will be installed. For further information on optical fiber products, please contact FS.COM. Our fiber optic cable price is the cheapest with great feedback.
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.
It’s true that fiber optic cable, based on optical technology to carry information between two points, have become increasingly important in fiber optic systems. This cable is often attached with the same or different connectors on the ends to connect devices, for example, LC LC multimode patch cord (LCs on both ends). When used in premises, fiber optic cables can be used as backbone cabling in a standard structured cabling network, connecting network hardware in the computer room. And when applied in optimized fiber optic networks, they go directly to the work area with only passive connections in the links. They can be installed indoors or outdoors using several different installation processes. One of my recent blogs has talked about safety issues about fiber optic cable installation. Today, this article still focuses on its installation, but from other aspects, including the general guidelines, its pulling tension, bend radius, and so on.
When deployed outside, fiber optic cables may be direct buried, pulled or blown into conduit or innerduct, or installed aerially between poles. When used outside, they can be e installed in raceways, cable trays, placed in hangers, pulled into conduit or innerduct or blown though special ducts with compressed gas. The installation process depends on the nature of the installation and the type of cables being used.
First point to mention is that fiber optic cable is often custom-designed for the installation and the manufacturer may have specific instructions on its installation. So, it’s highly recommended to follow the cable manufacturer’s suggestions. Often, it’s necessary to check the cable length to make sure the cable being pulled is long enough for the run, so as to prevent having to splice fiber and provide special protection for the splices. Of course, it’s better to try to complete the installation in one pull. Prior to any installation, one should assess the route carefully to determine the methods of installation and obstacles that are likely to be encountered.
- Pulling Tension
Fiber optic cable is designed to be pulled with much greater force than copper wire if pulled correctly, but excess stress may harm the fibers, potentially causing eventual failure. Cable manufacturers install special strength members, usually aramid yarn, for pulling. Fiber optic cable should only be pulled by these strength members. Any other method may put stress on the fibers and harm them. During installation, swivel pulling eyes should be used to attach the pulling rope or tape to the cable to prevent cable twisting during the pull.
Besides, cables should not be pulled by the jacket unless it is specifically approved by the cable manufacturers and an approved cable grip is used. Tight buffer cable can be pulled by the jacket in premises applications if a large (~40 cm, 8 in.) spool is used as a pulling mandrel. It’s right to wrap the cable around the spool 5 times and hold gently when pulling.
It’s ill-advised to exceed the maximum pulling tension rating. It’s suggested to consult the cable manufacturer and suppliers of conduit, innerduct, and cable lubricants for guidelines on tension ratings and lubricant use.
On long runs (up to approximately 3 miles or 5 kilometers), one should use proper lubricants and make sure they are compatible with the cable jacket. If possible, an automated puller can be used with tension control and/or a breakaway pulling eye. On very long runs (farther than approximately 2.5 miles or 4 kilometers), one should pull from the middle out to both ends or use an automated fiber puller at intermediate point(s) for a continuous pull.
- Bend Radius
When there are no specific recommendations from the cable manufacturer, the cable should not be pulled over a bend radius smaller than twenty (20) times the cable diameter. And after completion of the pull, the cable should not have any bend radius smaller than ten times the cable diameter.
- Twisting cable
It’s known that twisting the cable can stress the fibers, thus in no case should one twist the cable. (Tension on the cable and pulling ropes can cause twisting.)
Use a swivel pulling eye to connect the pull rope to the cable to prevent pulling tension causing twisting forces on the cable.
Roll the cable off the spool instead of spinning it off the spool end to prevent putting a twist in the cable for every turn on the spool.
When laying cable out for a long pull, use a “figure 8” on the ground to prevent twisting. The figure 8 puts a half twist in on one side of the 8 and takes it out on the other, preventing twists.
Fiber optic cables have been widely deployed for computer net- works (LANs), closed circuit TV (video), voice links (telephone, intercom, audio), building management, security or fire alarm systems, or any other communications link. With its installation in large scale, it’s of great importance to know some basic points on cable installation discussed in this text. As for the fiber optic cables chosen for project, you can try Fiberstore, whose cables are available in many types, like SC fiber optic cable, LC SC cable, MTP cable. All are test- and quality-assured, suitable for both indoor and outdoor installation.
It’s known that fiber optic termination methods vary based on the types of fiber optic cable being terminated, the style of connectors or splices used and the termination process appropriate for that connector. Generally speaking, fiber optic cable can be terminated in two ways—connectors that mate two fibers to create a temporary joint and/or connect the fiber to network equipment, and splices which create a permanent joint between the two fibers. Each termination method must have two primary characteristics: good optical performance (low loss and minimal reflectance) and high mechanical strength. As such, the terminations can be made in the right style, installed in a manner that provides low light loss and back reflection and protected against the expected environment, dirt or damage while in use. This passage mainly talks about the first method: connector.
Most fiber optic connectors are plugs or so-called male connectors with a protruding ferrule that holds the fibers and aligns two fibers for mating. Choosing a connector type for any installation should consider if the connector is compatible with the systems planned to utilize the fiber optic cable plant, if the termination process is familiar to the installer and if the connector is acceptable to the customer. If the systems are not yet specified, patch cords with different connectors on each end (e.g. LC ST patch cable) may be necessary.
Fiber optic connectors are manufactured in different styles (say, ST, SC, LC, MT-RJ) that attach to the fibers in a fiber optic cable (LC to LC fiber cable single mode) by a number of methods, such as epoxy polish, prepolished/splice, etc.. ST is one of the most popular connectors for multimode networks, like most buildings and campuses. SC is a snap-in connector that is widely used in singlemode systems for it’s excellent performance and multimode systems because it was the first connector chosen as the standard connector for TIA-568. LC uses a 1.25 mm ferrule, half the size of the ST. Otherwise, it’s a standard ceramic ferrule connector, easily terminated with any adhesive. MT-RJ is a duplex connector with both fibers in a single polymer ferrule. It uses pins for alignment and has male and female versions, basically obsolete nowadays.
Several termination methods are available for fiber optic cables, and the following passages list three terminations: adhesive termination, crimp/polish termination and prepolished termination.
- Adhesive Termination
Epoxy Polish: The fiber is glued into the connector with two-part epoxy and the end polished with special polishing film. This method provides the most reliable connection and lowest losses. The epoxy can be allowed to set overnight or cured in a special oven. A “heat gun” should not be used to cure the epoxy as the uneven heat may not cure all the epoxy or may overheat it which will prevent curing.
Hot Melt: This connector is similar to the epoxy/polish connector but already has the adhesive (a heat set glue) inside the connector. The adhesive is liquefied in an oven before the fiber can be inserted. The fiber is secured when the adhesive cools.
Anaerobic Adhesives: These connectors use a quick-setting adhesive instead of the epoxy. They may use a single part adhesive or an adhesive and set- ting agent. Some adhesives do not have the wide temperature range of epoxies, so they should only be used indoors unless otherwise specified.
- Crimp/Polish Termination
These connectors use a crimp on the fiber to hold it in the connector ferrule. The fiber can be polished like an adhesive connector or cleaved with a special tool. Insure the crimp is made properly to prevent fiber pistoning (pulling back or pushing forward in the connector ferrule.)
- Prepolished Termination
These connectors have a short stub of fiber already epoxied into the ferrule and polished. Termination requires cleaving a fiber, inserting it into the back of the connector like a splice and crimping. The loss of these connectors will generally be higher than adhesive connectors, since they include the connector loss plus a splice loss in every connector.
To ensure low loss, the fiber must be cleaved properly, which requires a good cleaver and good technique. Insure the crimp is made properly to prevent fiber pistoning. The termination process can be monitored with a visual fault locator.
Connectors can be installed directly on most cable types, including jacketed tight buffer types like simplex, zipcord and breakout cables, where the where the aramid fiber strength members in the cable are crimped or glued to the connector body to create a strong connector. Connectors can be attached to the 900 micron buffered fibers in distribution cables, but the termination is not as rugged as those made to jacketed cables, so they should be placed in patch panels or boxes for protection. The 250 micron buffered fibers in loose tube cables cannot be easily terminated unless they have a reinforcement called a breakout kit or furcation kit installed, where each fiber is covered by a larger plastic tube. Generally loose tube and ribbon cables are terminated by splicing on a terminated pigtail.
Cables can be pulled with connectors already on them if, and a big if, you can deal with two issues: First, the length must be precise. Too short and you have to pull another longer one (it’s not cost effective to splice), too long and you waste money and have to store the extra cable length. Secondly, the connectors must be protected. Some cable and connector manufacturers offer protective sleeves to cover the connectors, but you must still be much more careful in pulling cables. You might consider terminating one end and pulling the unterminated end to not risk the connectors.
When special tools are required, use them in the appropriate manner. And once installation is completed, connectors should be covered with an appropriate dust cap and stored in a safe location awaiting testing or connection to net- work equipment.
Fiber terminations must also be of the right style to be compatible to the equipment involved and be protected against the environment in which they are installed. When several connector types are all acceptable, or only one connector type is available but not ideal for the installation, the installer should discuss the merits of other types before committing to the project.
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.
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.
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.
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 non‐BIMMF 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.
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.
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-μm 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.