What are Bend Insensitive Cables and Why Use Them?

Bend-insensitive fiber is a vital part of most FTTH and now FTTx networks.

Fiber Attenuation – How are YOU managing it?

The main limit to performance in optical fiber is attenuation.  Optical fiber attenuation, commonly known as loss, refers to the weakening or degradation of the optical signal as it passes through the glass fiber over the total distance of the fiber.  Insertion loss and back reflection (return loss) are two tests that will enable a technician to correct attenuation problems on a fiber span.

Testing the fiber will show you where the weakened signals are located.  Physical characteristics of the fiber, increased signal levels, amplification nonlinearity, inconsistent or ‘dirty’ connector end-faces as well as components on the fiber such as splices and connector terminations can all be a factor that cause increased attenuation.  Attenuation (loss and back reflection) can be measured by using an Optical Power Meter and an Optical Light Source , or an Integrated Power Meter / Light Source for bidirectional testing (pair needed), or an Optical Time Domain Reflectometer (OTDR) and a Handheld Power Meter.  (It is recommended to utilize a fiber reference jumper for all scenarios).  When testing large fiber counts, data storage and the ability to download the information to a computer, is essential.

Using any of the above mentioned test scenarios; the light source will send a continuous wave signal, which simulates the operating wavelength of the emitter on the transmission equipment, down the fiber in question.  At the far end of this fiber the power meter will be connected.  The result of this test will be the loss of dB which is a relative reading and is equal to the transmitted power minus the received power.  This test gives a numerical value for the power received.  To obtain accurate loss measurements, a reference setting function must be available on the power meter.  The setting of a reference requires a test jumper be connected to power meter, and also the light source and connected by a coupler. A reference reading is than taken, and than the power meter/light source are attached to the different ends of the cable under test. The resultant reading will be the loss or attenuation of the fiber under test only.  Attenuation will differ depending on the direction in the fiber itself.  Different results can be obtained when measuring from A to B and from B to A.

Back reflection (return loss) is the ratio of the light backscattered or reflected in the reverse direction of the forward direction of travel.  Back reflection limits and/or degrades system performance.  Unlike attenuation, which can be reduced by cleaning the connector interfaces etc., the effects of back reflection can only be resolved by re-polishing connector faces, or even changing the type of connector interfaces such as UPC or APC connector polishes.

While every effort should be made to keep attenuation to a minimum such as effective fusion splicing techniques, proper bend radius consideration, proper fiber end face maintenance techniques, etc., sometimes attenuation must be added to a circuit because the receiver on the network element can not accept the signal level. An attenuator is a passive device used to reduce the amplitude of a light signal without significantly changing the waveform itself.  Primarily there are five different configurations of attenuators and each configuration has its own strength.

Hybrid Attenuator (Plug) (Male to Female) or (The Opposing Ends are a Different Connector Type)  The hybrid style is ideal for reducing the intensity of a signal just prior to going into a receiver.  This type of attenuator is typically available with similar connector ends with male/female configurations. They can also be available with different connector types on each end as well.  The high performance characteristics of this type of attenuator make it the perfect choice for DWDM systems, CATV, EDFA, with Instrumentation and other highly amplified systems, LAN and Telecommunication Networks and high-speed data-com.

Patch Cord Attenuator (In Line) (Attenuator is within a cable assembly) the attenuating fiber patch cord is ideal for high power applications and can be easily installed into fiber splice enclosures.  The Patch Cord style offers simplified system set-up and reduced installation costs by combining the functions of patch cords and fixed attenuators in one convenient package.

Bulkhead Attenuator (Female to Female) The bulkhead style is ideal when two male connectors need to be mated with a fixed attenuator.  Many times you will find this type at the patch panel.  This type of attenuator is ideal for applications where return loss is not as critical and price is a consideration.

Loopback Attenuator The loopback style is ideal for simulating losses associated with outside plant cable runs allowing BER testing on engineering and production test standards

Variable Optical Attenuated Jumper (VOA) The variable style is ‘in-line’ (patch cord) and allows the user to change the attenuation of the signal in the fiber as it is transmitted through the device, using a screw on the side of the housing.  The maximum specified attenuation is achieved within 10 turns of the adjustment screw.  VOAs are often used to balance the signal strengths in fiber circuits and for precisely attenuating an optical signal in order to evaluate the dynamic range of transmission equipment.

3 Step Attenuator This attenuator is a completely passive device using bend radius of a 3mm jacketed cable as a means of attenuation without introducing back-reflection.  It is designed to fit onto your existing cable assembly and it leaves no lasting effects on cable jacketing.

Preparing Fiber Optic Cable for Splicing or Termination

I recently watched my coworker disassembling a computer using only one tool.  Was it the right tool for the job?  Yes and no.  It was the tool he had… it worked, however, there is definitely more than one tool out there that would have made the task easier!  This situation is definitely one that many fiber optic installers know all too well.  As a gentle reminder, how many of you have used your Splicer’s Tool Kit (cable knife/scissors) to remove jacketing or even slit a buffer tube and then use the scissors to hack away at the Kevlar?  Did you nick the glass?  Did you accidentally cut through the glass and have to start over?

Correctly splicing and terminating fiber optic cable requires special tools and techniques.  Training is important and there are many excellent sources of training available.  Do not mix your electrical tools with your fiber tools.  Use the right tool for the job!  Being proficient in fiber work will become increasingly necessary as the importance of data transmission speeds, fiber to the home and fiber to the premise deployments continue to increase.

Many factors set fiber installations apart from traditional electrical projects.  Fiber optic glass is very fragile; it’s nominal outside diameter is 125um. The slightest scratch, mark or even speck of dirt will affect the transmission of light, degrading the signal.  Safety is important because you are working with glass that can sliver into your skin without being seen by the human eye.  Transmission grade lasers are very dangerous, and require that protective eyewear is a must.  This industry has primarily been dealing with voice and data grade circuits that could tolerate some interruption or slow down of signal.  The person speaking would repeat themselves, or the data would retransmit.  Today we are dealing with IPTV signals and customers who will not tolerate pixelization, or momentary locking of the picture.   All of the situations mentioned are cause for the customer to look for another carrier.  Each situation could have been avoided if proper attention was given to the techniques used when preparing, installing, and maintaining fiber optic cables.

With that being said, why don’t we review basic fiber preparation?  Jacket Strippers are used to remove the 1.6 – 3.0mm PVC outer jacket on simplex and duplex fiber cables.  Serrated Kevlar Cutters will cut and trim the kevlar strength member directly beneath the jacket and Buffer Strippers will remove the acrylate (buffer) coating from the bare glass.  A protective plastic coating is applied to the bare fiber after the drawing process, but prior to spooling. The most common coating is a UV-cured acrylate, which is applied in two layers, resulting in a nominal outside diameter of 250um for the coated fiber.  The coating is highly engineered, providing protection against physical damage caused by environmental elements, such as temperature and humidity extremes, exposure to chemicals, point of stress… etc. while also minimizing optical loss.  Without it, the manufacturer would not  be able to spool the fiber without breaking it. The 250um-coated fiber is the building block for many common fiber optic cable constructions.  It is often used as is, especially when additional mechanical or environmental protection is not required, such as inside of optical devices or splice closures.  For additional physical protection and ease of handling, a secondary coating of polyvinyl chloride (PVC) or Hytrel (a thermoplastic elastomer that has desirable characteristics for use as a secondary buffer) is extruded over the 250um-coated fiber, increasing the outside diameter up to 900um.  This type of construction is referred to as ‘tight buffered fiber’. Tight Buffered may be single or multi fiber and are seen in Premise Networks and indoor applications.  Multi-fiber, tight-buffered cables often are used for intra-building, risers, general building and plenum applications.

‘Loose tube fiber’ usually consists of a bundle of fibers enclosed in a thermoplastic tube known as a buffer tube, which has an inner diameter that is slightly larger than the diameter of the fiber.  Loose tube fiber has a space for the fibers to expand.  In certain weather conditions, a fiber may expand and then shrink over and over again or it may be exposed to water.  Fiber Cables will sometimes have ‘gel’ in this cavity (or space) and others that are labeled ‘dry block’.  You will find many loose tube fibers in Outside Plant Environments.  The modular design of loose-tube cables typically holds up to 12 fibers per buffer tube with a maximum per cable fiber count of more than 200 fibers.  Loose-tube cables can be all-dielectric or optionally armored. The armoring is used to protect the cable from rodents such as squirrels or beavers, or from protruding rocks in a buried environment.  The modular buffer-tube design also permits easy drop-off of groups of fibers at intermediate points, without interfering with other protected buffer tubes being routed to other locations. The loose-tube design also helps in the identification and administration of fibers in the system. When protective gel is present, a gel-cleaner such as D-Gel will be needed.  Each fiber will be cleaned with the gel cleaner and 99% alcohol. Clean room wipers (Kim Wipes) are a good choice to use with the cleaning agent.  The fibers within a loose tube gel filled cable usually have a 250um coating so they are more fragile than a tight-buffered fiber.  Standard industry color-coding is also used to identify the buffers as well as the fibers in the buffers.

A ‘Rotary Tool’ or ‘Cable Slitter’ can be used to slit a ring around and thru the outer jacketing of ’loose tube fiber’.  Once you expose the durable inner buffer tube, you can use a ‘Universal Fiber Access Tool’ which is made for single central buffer tube entry. Used on the same principle as the Mid Span Access Tool, (which allows access to the multicolored buffer coated tight buffered fibers) dual blades will slit the tube lengthwise, exposing the buffer coated fibers. Fiber handling tools such as a spatula or a pick will help the installer to access the fiber in need of testing or repair.  Once the damaged fiber is exposed a hand- stripping tool will be used to remove the 250um coating in order to work with the bare fiber.  The next step will be cleaning the fiber end and preparing it to be cleaved.  A good cleave is one of the most important factors of producing a low loss on a splice or a termination.  A Fiber Optic Cleaver is a multipurpose tool that measures distance from the end of the buffer coating to the point where it will be joined and it precisely cuts the glass.  Always remember to use a fiber trash-can for the scraps of glass cleaved off of the fiber cable.

When performing fusion splicing you will need a Fusion Splicer, fusion splice protection sleeves, and isopropyl alcohol and stripping tools.  If you are using a mechanical splice, you will need stripping tools, mechanical splices, isopropyl alcohol and a mechanical splice assembly tool.  When hand terminating a fiber you will need 99% isopropyl alcohol, epoxy/adhesive, a syringe and needle, polishing (lapping) film, a polishing pad, a polishing puck, a crimp tool, stripping tools, fiber optic connectors ( or splice on connectors)  and  piano wire.

When a termination is complete you must inspect the end face of the connector with a Fiber Optic Inspection Microscope.  Making sure that light is getting through either the splice or the connection, a Visual Fault Locator can be used.  This piece of equipment will shoot a visible laser down the fiber cable so you can tell that there are no breaks or faulty splices.  If the laser light stops down the fiber somewhere, there is most likely a break in the glass at that point.  When there is more than a dull light showing at the connector point, the termination was not successful.  The light should also pass through the fusion splice, if it does not, stop and re- splice or re-terminate.

We will provide additional informational guides for other segments of the fiber optic industry in upcoming blogs.

Author: Fabian Newman of Fiber Solutions Inc.

Different ways to terminate fiber optic cable

Have you ever wondered what all the differences were when terminating fiber? There are so many options and not many people know why. I will try and outline the five things that you need to know to terminate your fiber correctly.

There are five basic classifications of fiber termination:  no-epoxy/no-polish, epoxy/polish, pigtail/splice on connector splicing.

NO-EPOXY/ EPOXY CONNECTORS

No-epoxy/no-polish connectors offer the easiest and quickest termination technology.   Installers only need to strip, cleave, and crimp the fiber into the connector body.  The connector contains a short pre-polished fiber stub in the ferrule.  In effect this connector has a built-in mechanical splice and a high quality, factory-controlled end face that provide excellent return-loss performance for a field terminated connector.   They are an excellent choice for locations where there is a low fiber count.  Reasons why this type of termination would be used are:  short length of slack fiber, quick installation and fast training for inexperienced technicians.

Items needed for this type of termination:

Connectors, Buffer Stripper, Kevlar Shear, Crimp Tool, Jacket Stripper, Cleaver, Cletop Connector Cleaner, Isopropyl Alcohol, Piano Wire, Safety Goggles

EPOXY/ POLISH CONNECTORS

There are two options for this technology: heat cured and quick cure.  Both methods are suitable for terminating high fiber count cables in a single location.  The process takes some experience to get proficient but can yield some of the lowest loss terminations.  This is an excellent option for installers with low labor costs and a stable, trained work force.  Fast curing adhesives reduce oven curing or air curing times considerably.  FSI feels that achieving anything above a PC (Physical Contact) polish on a fiber optic connector is unlikely, if not using a polishing machine. Training DVDs/Videos are great sources for training.

Items needed for this type of termination:

Connectors, Buffer Stripper, Kevlar Shear, Crimp Tool, Jacket Stripper, Cleaver, Cletop Connector Cleaner, Isopropyl Alcohol, Piano Wire, Safety Goggles, Curing Oven, Curing Stand, Lapping Film, Epoxy

PIGTAIL FUSION SPLICING

Rather than terminate fiber in the field, you can fusion splice a pigtail to the installed fibers.  Worrying about epoxy, hand tools or curing times are eliminated; however it does require the use of a fusion splicer.   This type of termination makes the most sense for installers that have already invested in a fusion splicer.  The compact fusion splicers available today, such as the Fitel S-122, are smaller and less expensive.  Installation can proceed quickly and the results can be as good as the epoxy polished connectors.  The cost is slightly higher however, it eliminates the need for assembly and termination labor costs and this will make a significant difference in overall costs in a short amount of time.  There will be an additional cost regarding the need for splicing hardware to house the splices.  This technology works best for installers working with a large number of fibers, or on high performance singlemode networks.

Items needed for this type of termination:

Jacket Stripper, Buffer Stripper, Cleaver, Isopropyl Alcohol, Alcohol, Kim Wipes, Fusion Splicer, Fusion Splice Protector Sleeves, Safety Goggles, Fiber Trash Can

SPLICE ON CONNECTORS

The splice-on connector eliminates the need for field polishing and significantly improves the quality of the termination and installation time required. FITEL manufactures factory polished ferrules with pre-cleaved fiber stubs that can be spliced onto the field fiber utilizing their proprietary ferrule holder and fusion splicer. Once spliced, the SC/APC, FC/APC or SC/UPC, FC/UPC connectors are easily assembled by using a process that requires minimal skill or training. A video of this product is viewable on the Fiber Solutions Online Website.

Items needed for this type of termination:

Splice On Connector Kit ( FC/APC, FC/UPC, SC/APC, SC/UPC), Fusion Splicer Kit (Fitel), Buffer Stripper, Jacket Stripper, Fusion Splice Protection Sleeves, Connector Assembly Tool, Isopropyl Alcohol, Kim Wipes, Fiber Trash Can, Safety Goggles, Fusion Splice Protection Sleeves

Are you using Flat Drop fiber optic cable?

Often times flat drop fiber optic cable which is typically used in FTTH applications to make the transition from the telecom pedestal to the NID/ONT/Customer premise, can really be difficult to penetrate. This is especially true when this transition needs to be made in a mid-span environment.

Fiber Solutions, Inc. has found several tools available from our suppliers that make this difficult and delicate task much easier.

 

1)    One way to easily penetrate flat drop fiber optic cable, is by the use of a Ripley 46270 FDS (Fiber Drop Stripper). This tool uses a One-Step stripping action for removing the jacket both top and bottom and exposing the dielectric strength members, and fibers, making them available for further termination.

 

The tool is available in two different configurations depending upon the cable being stripped. This is due to the variations in flat fiber optic drop cable specifications between manufacturers.

 

Additional information is contained on the attached datasheet.

 

2)    Another alternative for this difficult task is the use of the NEW Jonard FOD-2000. This tool puts a slit on each side of the cable, making it extremely easy to cut away the excess jacket and dielectric materials making the fibers available for termination.

 

The Jonard FOD-2000 can accommodate both end and mid-sheath stripping applications as outlined on this datasheet.

 

Details of this process are clearly demonstrated on this video.

 

Both of these tools and other varieties are available for this difficult and delicate task.

 

If you need additional information please call us at 800-743-4237 or e-mail info@fibersolutionsinc.com.

 

New OTDR from OFS/Fitel Released

Fiber Solutions, Inc: We are proud to announce the recent release of the OFS LBT-101 Short Range OTDR. This amazing tool has recently been introduced by OFS/Fitel/Furukawa America and is directed toward the telecommunications, and in particular the FTTx (Fiber to the Home/Premise) marketplace.

 

The main differentiator of this OTDR compared to other FTTx OTDR’s is the use of 1610nm, and filtered receiver. This allows the OTDR to be used from the NID/ONT/Customer Premise and shooting back into traffic toward the splitter. The 1610nm wavelength will not interfere with the oncoming traffic, both toward the individual customer premise, nor on the other side of the splitter. Conventional OTDR’s that utilize 1310/1490/1550nm wavelengths can interfere with the oncoming traffic, and possibly disrupt the triple play services including Voice, Data, and Video.

 

Many other features of this amazing new PON OTDR are outlined in this datasheet.

How to properly clean fiber optic connections?

Studies have shown and our sales back that up, that an overwhelming majority of people use “dry cleaning methods” such as cletop cleaners, reel cleaners, sticks/swabs, etc., or they may introduce IPA (Isopropyl Alcohol) to aid in the cleaning process.

 

Is “dry cleaning” an effective method for cleaning fiber optic connectors?

Often times “dry cleaning” or the introduction of IPA can have some adverse effects. For instance:

1)   IPA does not dry immediately. Left to dry on its own IPA

Can take minutes to dry, and than it leaves a residue. That residue can leave the connection susceptible to dust and debris gathering on the fiber end face, and causing degradation in signal transmission.

 

2) Cletop cleaners, reel cleaners, and sticks/swabs, are considered “dry cleaning tools” these can be very effective if you have the connector available to you, such as a jumper connection, or the fiber is not very dirty. However if there are abrasive contaminants on the end face, such as metal filings from the adapter housing, etc. this can lead to scratches on the fiber face. In addition in many “computer type” humidity controlled environments the dry cleaning methods can lead to static charges on the connector end-face which may lead to the introduction or adherence of other contaminants over time. This process can contribute to signal degradation.

 

 

The Advantages of using a Tri-hole Stripper

www.FiberOpticTool.com Blog

“Dedicated to answering your questions relating to fiber optic and telecom tools & testing”

1) What is the advantage of using a Tri-hole stripper such as Jonard’s JIC-375 (TO-S-JIC-375-J) instead of  a standard Miller Stripper (FO-103-S)?

In time past, it used to be that a majority of the stripping of fiber optic cable in the field was done in preparation for either mechanical or fusion splicing. That meant that you only needed to typically strip the buffer coating of 250um. That made the use of a Miller stripper, or a single-hole stripper ideal. However as time progressed other cables were introduced that included the use of 900um buffers as well. However, those buffers were typically stripped farther back on the cable, and the actual area where the splice occurred was still typically 250um. Again that made the use of separate tools for 900um and 250um an acceptable practice.

However now as we are moving toward FTTx, it is not uncommon to have to strip 3mm jacket, 900um buffer, and 250um on the same cable end, as you prepare to connectorize a cable for insertion into an Optical node, or Optical Network Terminal (ONT) on the side of a home for example. Another driving force behind this type of tool in the FTTx application is the use of Splice-On-Connectors (SOC). Again this technology replaces many of the cumbersome steps previously associated with cable preparation; termination and polishing of fiber optic end faces, and replaces that with an easy assembly process of splicing on a factory terminated connector. This provides significant benefits in terms of optical performance, and greatly reduces the amount of time needed for a technician to install a fiber optic connector in the field.

So the need for a Tri-Hole stripper can easily been seen in the time savings it provides. This is further demonstrated in this video. Click Here