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Have a technical question for Fiber Optic Center?

Please email your question to AskFOC@focenter.com and we will respond ASAP. 

In addition to replying, we will post your question and our answer here on the AskFOC page.  Everyone remains anonymous when we post so feel comfortable asking your questions.  You can also search to see if your question has already been answered in the FAQs section below.





AskFOC Questions (open for Answers)

I am having issues on MT polishing. I am getting “Y” radius less than 100. Can you advise which step should I reduce time or pressure?

This customer had a need to increase y-axis radius on MT’s (making the surface “flatter”), was having difficulty.  After trying the most common recommendations (reducing pressure, trying non-PSA films instead of PSA films) with no improvement, FOC technical team discussed as a group, and one recommendation to come from the meeting was to ensure proper torque was applied when fixing the ferrules to the fixture. 

After providing this information to the customer, he used a new, calibrated torque wrench to fix the ferrules, and results were significantly improved—-customer yields are now at acceptable levels, he is happy.

Answered by AskFOC Technical Team June 9, 2017ask_FOC_trans

I need information on cleaning and repairing TOSA/ROSA devices. Is this something you can help them with?

We have done design work on the TE transceivers in the past.  Depending on the internals you are able to clean (more or less). There are in fact two types, ferrule based or molded based.

The ferrule based internal parts you can clean with the standard swabs/sticks you use when cleaning adapters in panels etc.

The molded parts are more difficult to clean. Due to the z-direction alignment in the adapter there is a stop where the ferrule need to reference to. That makes the cleaning even harder because the diameter is smaller than the ferrule diameter. In this area is often the collimating lens to concentrate the in- or out coming light into or out of the fiber. There are special swabs which are able to clean the ‘sleeve’ alignment part of the transceiver but also have a center piece (tip) that is able to touch the collimating lens and clean the lens surface without leaving any residue or scratch the lens surface. Do not use IPA at this surface, only ferrule cleaning fluid that evaporate quickly and leaves nothing!

Most suppliers of the molded optical housings for the transceivers have special cleaning instructions, and specify the ‘profile’ of the cleaning tip, the method and fluid to use.  We suggest you look for the cleaning instructions based on your molded optic supplier.  If you can find and share the specified cleaning tip, FOC can supply them.

Answered by AskFOC Technical Team May 30, 2017ask_FOC_trans

Does FOC have any experience or recommendations in using microwaves to cure fiber optic epoxies?

FOC does not have any experience using microwaves to cure epoxies.  Certain microwave machines, much more sophisticated than the familiar domestic models, are now being used to cure some adhesives.  These machines make use of variable frequency microwaves (VFM) to sweep through a range frequencies, providing much more uniform heating throughout the oven, and can accomplish adhesive cures in significantly less time than conventional heat ovens. 

One place this technology is used in the semiconductor and electronic packaging industry, to rapidly and uniformly cure chip underfills; where miniaturization and mismatched CTEs of the substrates involved cause tensile/compressive stresses that damage the parts.   

To date FOC has not seen anyone in the fiber industry using microwaves to cure epoxies.  For more information about microwave curing, here is a link to Lambda Technologies:   http://www.microcure.com/.

Answered by AskFOC Technical Team May 11, 2017ask_FOC_trans

What are the probable causes of light leakage from ferrule barrel? Is it while insertion of fiber into ferrule or while stripping fiber with Fujikura stripper?

We will contact you to discuss further but here are a few different possible issues:

  • Insufficient epoxy at rear of ferrule, leading to fiber break.  This can be determined fairly easily by cross-section of failed parts.
  • Fiber damage (nicking) during stripping, leading to fiber break.    Stripper causing fiber damage can often be identified by performing a fiber “bend test” immediately after stripping—–bend fiber 45-degrees in 4 directions (north, south, east, and west).   Nicked fiber should break if scored during stripping.    He should do this for 100% of production for a period of time, as it may not be evident all the time.  If he sees fiber breakage in more than, say, 1-2% of bend-tests, then likely he’s in need of replacing blades / further investigation of the strippers.
  • Fiber damage during termination—rotating ferrule around to “spread the epoxy”, when fiber is fully inserted. Depends on ferrule manufacturer, but this can be an excellent way to score the fiber and severely weaken it.   He should check lines, see if operators are rotating ferrules—-sometimes it’s necessary if tight fit, but shouldn’t need to be done as a matter of course.   To see if his ferrules have such sharp edges inside, he can strip a 900um fiber, do a bend test to make sure fiber integrity is ok, then insert it into a ferrule (no epoxy) all the way, gently rotate the ferrule 360-degrees (no need to apply downward pressure, just rotate the ferrule), then remove and re-do the bend test.  If fiber breaks, this is an area of significant concern, especially if operators are rotating connectors during term.


Answered by AskFOC Technical Team May 4, 2017ask_FOC_trans

Is there a solution for getting LC/PC for return loss more than 60 dB? If it depends on final polishing film, is Ultimas final polishing film suitable? What kind of films will work? Is there a special polishing method?

Unfortunately, there isn’t a special final film that produces 60 dB on UPC connectors. Our film is the most likely to get you there, but many other factors need to be considered including test leads on the RL meter.  However, I dare say getting 60 dB with a decent yield, may not be doable without considerable scrap.  Also, ultra-low return loss degrades with multiple mates, so you need to get it under the first test.  Consider that you may test -60.5 dB on the first test with ‘fresh’ test leads, but if the customer tests the next time with the best test leads, it may be -59 dB, then -57 dB, then finally settle somewhere below that. 

Here are a few additional comments:

  • In terms of polishing process, there’s not much more that can be done with current state of lapping films.
  • To tweak out the last few dB’s, you need to focus on core alignment (highest concentricity ferrules and fibers, and most precise adapter split-sleeves) that can be found.
  • RL values are not a characteristic of the connector itself, but of the mated pair.   A RL limit of 60 dB in production will mean you’ll need to constantly replacing test leads. The end user will likely not be able to correlate results.
  • If end user truly needs 60’s, APC’s are the way to go.


Answered by AskFOC Technical Team April 24, 2017ask_FOC_trans

In looking up the IL effect of Return Loss, I found definitions in your FOC Glossary (https://focenter.com/foc-glossary/) for IL, IL/RL, RL. In addition to these definitions, can you provide any info on the IL effect of Return Loss?

Yes, the definitions in the FOC Glossary (https://focenter.com/foc-glossary/) are:

  • Insertion Loss: The ratio between the power received at a specified load before and after the insertion of a filter at a given frequency. It is an indication of the attenuation provided by a filter.
  • Return Loss: The Channel Return Loss (RL) is a measure of the consistency of the impedance down the length of not just the cable, but also the connections and the patch cables.

Regarding the IL effect of Return Loss, Return Loss in an connection is that part of the optical power reflected back to the source, usually expressed as how many dB less that the forward power. It is usually regarded as a bad thing, you want as much of the light to as possible to get to the receiver and reflections, if you are very unlucky can cause instability. 

Reflectance or optical return loss (which has also been called “back reflection”) of a connection is the amount of light that is reflected back up the fiber toward the source by light reflections off the interface of the polished end surface of the mated connectors and air.

Based upon that definition a PC connector should not have any back reflection since PC stands for physical contact. But in reality the surfaces have some non-planarity and therefore the glass air glass interface follows the Fresnel equations.

A detailed description of the process and how it affects system loss is on the FOA website: https://www.thefoa.org/tech/ref/testing/test/reflectance.html

Answered by AskFOC Technical Team April 14, 2017ask_FOC_trans

We are looking for a replacement of isopropyl alcohol as a fiber optic cleaning fluid (specifically the isopropyl alcohol that is used to clean the stripped fiber before gluing the connector). Our goal is to get rid of any alcohol used in the connector assembly process. Can you tell us a little more about Microcare Sticklers MCC-POC03M and MCL Eco-Clean cleaning fluids on your website or alternative fluids? Also, we are using Schleuniger equipment for fiber stripping. The fiber is very clean. Can we proceed directly to connector assembly without cleaning fluid? Is static charge a problem?

Short Answer:  

If optimum health / safety is the target, the Stickler fluid will be an improvement over IPA, and should also clean fibers well. I have not used the MCL fluid in production, but the published marketing advantages seem to be similar to Stickers, so I’m assuming they have similar performance.  I’d recommend always cleaning after stripping.

Very Long Answer:

Cleaning fluids:

Sticklers fluid:  I’ve only used 99%+ IPA for this cleaning in manufacturing environment.  I’ve used Stickler fluid for low-volume cleaning (doing demo’s of equipment, where I need to clean a few connectors here and there—-the little bottle is very easy for carrying for field use.).   It’s always worked well, though I have never done any real experiment specifically to quantify / compare the cleaning effectiveness.   I think the Stickler fluid is certainly a good option, performance-wise.   And it’s non-flammable, “non-hazardous”, etc.  Certainly smells like IPA, but doesn’t support a flame for more than a second or two.   

MCL Fluid:   I’ve zero experience with it, can’t really comment.  I would have to guess the chemical makeup would be similar enough to Stickler fluid—–the marketing bullet-points seem similar.

Cleaning process:

There are a few risks associated with not cleaning after stripping:

  1. Oils or other film / residue on the fiber prevents good bonding of the epoxy to the fiber.   This can / will result in reduction in long-term performance / reliability.   On a “PFMEA” analysis, this would be a high “Severity”  of 7, 8 or 9.   But what’s worse is that the effects of this are nearly impossible to detect in the short-term, so , again in a PFMEA analysis, the “Detection” rating would be huge—-9 or 10.      
  2. Gross contamination may clog the ferrule hole, making insertion of fiber difficult (leading to increased mfg costs, including likely increased scrap).  This is less of a worry about customer satisfaction, and more a question of keeping your manufacturing costs / throughput on-target.
  3. Cleaning with a moistened cleaning tissue usually provides an additional service:  By “squeaky cleaning” (cleaning with moist tissue until you hear the fiber “squeaking”), the “squeak” comes from the fiber vibrating very quickly.   This vibration serves as one test of fiber integrity——if there are nicks, scratches, or other defects in the stripped fiber, the hope is that this vibration may cause the defect to propogate due to the vibration, and fail now (rather than after the customer receives the product).   I’ve been trained that this is true, and it seems sensible, but have never objectively measured if this is a real benefit or not.

Thus:   after stripping, I’d highly recommend additional cleaning of the fibers regardless, UNLESS the following conditions are met:

  • You can determine that
    • the fiber is indeed perfectly clean after stripping—-cleaner than you can get with using IPA or some other fluid / cleaning method,
    • and there is very low risk of the stripping process resulting in unclean fibers.
  • The fiber is immediately inserted into a connector, without ever putting the stripped fiber down or transporting it in the production line to next step, where there is some risk of fibers contacting a contaminated surface.
  • ALL fiber types / manufacturers in your production line strip with the same cleanliness.   (I’d not like to have a variety of strip / clean procedures and have to depend on the production line controls to ensure proper stripping / cleaning procedures are used, based on the fiber manufacturer or type of buffer material, etc).

Static Charge:  

              I do believe static charge can certainly create several issues, mostly in terms of attracting loose dust particles from the room air—a relatively minor problem (easy to re-clean—it’s not attracting residue or oils, etc).    Efforts to reduce static charge should be implemented if cost-effective to do so.   I’m not well-versed in where the static charges are usually created and best way to avoid, but I *think* the stripper process itself can generate static.   Cleaning with lab-wipe and IPQ certainly can / does create static charge.    

If the Stickler or MCL fluid does indeed reduce static charge (as claimed), I’d say this is a “moderate” advantage in connectorization.   I have seen situations where engineers introduced an ionized air “wash” at the stripping  / cleaning stations to remove static charge on the fibers during cleaning (an ionized air line at the bench—I don’t know any other details on the ionizing of the air), seemed cheap and effective solution—–but again, if you achieve the same with a special cleaning fluid instead of IPA, then even better.

Answered by AskFOC Technical Team March 16, 2017ask_FOC_trans

What is the most effective way for cleaning the entire surface of an MT ferrule?

Ultrasonic cleaning of ferrules after polish, and guide-pin hole brushing during / after polish.

Contamination on the surface of the ferrule is a major (if not THE major) contributing factor to poor testing performance (assuming, of course, that the connector was built properly and meets geometry specs).   The best way to clean entire ferrule surface, in my opinion, is to clean all ferrule in an ultrasonic bath (using filtered / DI water).  This removes all contamination from guide pins / holes and surface of the ferrule.

Care should (and must) be taken through the entire assembly process after polishing, to minimize contamination of ferrule surface, guide pins, etc.

Also:  guide pin holes should be scrubbed with brush during polishing to make sure loose particles of abrasive or removed ferrule material don’t stay in the holes and prevent future issues when mating/un-mating.

Answered by AskFOC Technical Team February 24, 2017ask_FOC_trans

I need a really strong bond. What is the absolute strongest adhesive you have?

Modern adhesives are pretty amazing, and people do seem to want to rely on them more and more.  But it is important to know that epoxies are NOT primary fasteners.  Primary fasteners are hardware devices that mechanically join two substrates together – like a bolt, clamp, clip, any threaded fastener like a screw, threaded insert, etc.  They are immune to temperature swings and moisture – the ban of much chemistry, and the Achilles heel of epoxy.  If you are relying on a critical joint not to fail, epoxy is probably not the way to go. 

Also, it is a misconception to think that strong joints require ‘strong’ adhesives. Good adhesion is all about the surfaces involved.  Adhesive failures usually happen at one of the surfaces – not within the adhesive itself.  This is where cleanliness of the surfaces prior to bonding is critical.  Also, the amount of surface area devoted to the bond, a decreasing piece of real-estate in ever-more miniaturized packages  – needs to be adequate.  The best adhesive and cleaning won’t work if the bond area is too small. 

We are always available by phone and email if you would like to discuss in more detail or if any clarification is needed at sales@focenter.com or 508-992-6464.

Answered by AskFOC Technical Team February 22, 2017ask_FOC_trans

I have some pre-angled 24-fiber single mode mpo connectors that are producing good geometry. However, with my current process I am using a “Multimode” non-angled fixture to effectively remove the epoxy in the 1st step. Then, I am removing the ferrules and re-inserting them in an angled fixture to complete the rest of the remaining steps in the process. Is this a necessary procedure with this type of connector?

The short answer:

  • Using the PC fixture, as you describe, is a common method, many do the same.  Though not very efficient, it is a “tried and true” method.      
  • You CAN eliminate the PC fixture, but need to make sure epoxy bead is fully removed (so that none remain on the final product, which should have angle cut across about 90% of the ferrule surface, not all the way) and scribing processes are solid.
  • Best option, if available,  would be to use Pre-Angled ferrules
    • Quicker polishing times—–MUCH quicker than using PC fixture to remove epoxy
    • Less material needs to be removed from the ferrule—-thus preserving original end-face hole dimensions and locations (and preserving optimum optical performance).

The long answer:

Using a PC plate to first remove epoxy, and then changing to APC plate to complete the angle-generation and polishing, is a common way to polish these ferrule.

The risk with this (besides being labor-intensive) is removing too much material from the ferrule during the epoxy removal step—-you have to take care to not remove too much material, as the more you polish down, the less fiber holes will meet intended dimensions:   The holes molded into the ferrules may very well not be consistent throughout the length of the ferrule.   If you can visualize a hole that is not perfectly perpendicular to the ferrule end-face, you can see that the more material you remove, the result will be a fiber center moving more and more away from intended location.

This is one reason it is preferred to use pre-angled MT ferrules for APC application, if possible.  Less ferrule material needs to be cut away.   Not only do you save production time of loading into two fixtures, but you very likely improve performance (as there’s less chance for the holes at the ferrule end-face surface will deviate from their original, molded positions).

But—you don’t have pre-angled MT ferrules.   So, yes—–using the PC plate first is reasonable.   Is it “necessary”?  Well, the goal of using the PC plate is to remove all the epoxy.   If you can reduce the “footprint” of the epoxy bead so that you can remove it on the APC fixture while you generate the angle—–then you wouldn’t need to use the PC plate.    (so the angle generation will also remove the epoxy).   However, reducing the epoxy bead footprint likely also means reducing epoxy bead support of the fibers——-so you’d increase risk of fracturing fibers, since they’re less protected by epoxy bead.  So you’d need to be careful with this option—-keep track of fiber crack / fracture failures, make sure there’s no significant increase.

Some people only use the APC fixture, and just apply very small amount of epoxy on the end-face.    The thinking is that while this would increase chance of end-face cracks, the fact that we’re then going to cut an angle across the fiber section (removing quite a bit of ferrule material) is insurance that cracks won’t be a problem——it’s unlikely the cracks would propagate down the fibers so far.

We are always available by phone and email if you would like to discuss in more detail or if any clarification is needed at sales@focenter.com or 508-992-6464.

Answered by AskFOC Technical Team January 24, 2017ask_FOC_trans

Does Phenix Fibersect MT cleaver saw have warranty and replacements?

The Phenix Fibersect MT cleaver saw is warranted for 100,000 cuts or 1 year, whichever occurs first.  Phenix inspected several saws with about 40,000 cuts and our 100,000 projection is based on observed wear.

The saw can be easily replaced. This is done by replacing the saw assembly which includes the saw, motor and motor bracket. The motor is replaced as part of the saw assembly.  Instructions would be furnished with the purchased assembly. An electronic technician can easily do this in 15 minutes or less.

Thank you for visiting the product page.  Let us know if we can answer any other more specific questions at sales@focenter.com or 508-992-6464.

Answered by AskFOC Technical Team January 18, 2017ask_FOC_trans

Looking for tips on epoxy work surfaces. Do you have any information on that?

When working with epoxy, neatness really counts.  Since the pot life on epoxy starts the moment the two parts are mixed, plan your work so that you have everything you need when you start – like:

  • really clean mixing equipment and any secondary mixing containers (stainless steel spatulas, polyethelyene (PE) and polypropylene (PP) mix containers that have been final rinsed with electronic grade isopropyl alcohol (IPA, <0.5% water))
  • timers
  • helpful fixturing – i.e. a test tube-like rack for holding syringes upright
  • any dispensing equipment reservoirs, positioned to be filled directly  

Something that can also be helpful is a polyethylene work surface.  PE is white in color, chemically resistant and available in 1/8” or ¼” sheets, like plywood.  It can be cut (using wood working tools) and laid down in any dedicated space to make a clean, and easily cleaned, work surface.  Any uncured epoxy that lands on a PE surface can easily be wiped off (acetone and a Kim-Wipe make this very easy), and cured epoxy can be removed even more easily by gentle scraping – the cured epoxy will pop off of the PE surface. 

Since PE is white, the gleaming surface may by its very nature discourage other activities that clutter and intrude on this area where neatness really counts.   Any extra pieces of PE can also be used to create fixtures that helps make the mixing/filling job go more smoothly. 

Answered by AskFOC Technical Team January 12, 2017ask_FOC_trans

What’s the easiest way to load a syringe with a 2.5g pack of epoxy?

We think the best way to load a syringe with a mixed pack of epoxy is to have BOTH HANDS available to do the job.  This means you want the clean syringes ready to go and POSITIONED for loading directly.  Anything like a test tube rack, that holds the syringes vertical, works – 

  • You can improvise a syringe rack by taping the syringe(s) to the side of a table or desk.
  • You can fashion a simple fixture that is a block (wood is ok, but something like Delrin would be better) that has a hole slightly larger than the size of the syringe barrel drilled vertically to hold the syringe upright (drill the hole all the way through the block so any spillage or overflow doesn’t collect in the bottom of a blind hole).  A larger block is more stable and makes a better base, and allows multiple holes to be drilled. 

Answered by AskFOC Technical Team January 10, 2017ask_FOC_trans

We recently had a customer ask that we put mating sleeves on the cable connectors before we ship to him. I think that he may end up with a dirty end face even though the dust cap will be on the other end of the mating sleeve. The cable assembly will be sealed in a plastic bag. What is your opinion?

Shipping mating sleeves on the connector ferrules instead of dust caps is very rarely done, and a traditional ferrule cap provides the best protection in most cases.  Using a brand new, clean and capped “mating sleeve” (adapter) should not cause any issues.

Answered by AskFOC Technical Team December 12, 2016ask_FOC_trans 

Is there an industry standard for rotational tolerance of an angled ferrule (APC) face with respect to a key on the ferrule carrier or connector body. Or do manufacturers just strive for a minimum. What are typical figures?

With APC ferrules, the Apex Offset value is actually the resultant of two vectors—–the “horizontal” axis offset (the offset due to actual end-face angle error) and the “vertical” axis offset (the offset due to rotational error of the ferrule relative to the key—-“key error”). That is, if the actual Angle of the APC ferrule is exactly 8.000 degrees, then any Apex Offset value is 100% due to Key Error. Conversely, if the actual Key Error of an APC connector is exactly zero, then any Apex Offset value is 100% due to angle being greater than or less than 8.000 degrees.

So, some manufacturers simply use Apex Offset as the only pass / fail specification when measuring angles, and ignore the Key Error value.  It’s really up to the manufacturer.   I understand this from a production point of view—–after all, Apex Offset DOES have industry-accepted specifications, so if my product fails for Apex Offset, what difference does it make if it’s because of Angle error or Key error or both?

My answer to that question is:   if you want to improve your APC Apex Offset values, it’s critical to understand which aspect——Angle Error or Key Error—is creating the majority of the Apex Offset.   The causes of Key Error are completely different from the causes of Angle Error.  Often, the Key Error is simply due to the ferrule not sitting properly within the connector body, and has nothing to do with the polishing process—-simply springing the ferrule up and down a few times will “seat” it properly within the connector, and re-measured Key Error values fall to near zero.   This is in contrast to Angle Error values, which are almost always the direct result of the polishing process itself and requires re-polishing to fix.

So, while “Industry Spec” for Key Error may not exist, monitoring Key Error is very important when troubleshooting / improving Apex Offset results.

You should always strive for a minimum of key error, but you don’t want to handcuff yourself and rework product that meets Apex Offset specifications.   If your customer is requiring a specification on Key Error, a common spec value is +/- 0.5 degrees—-because at this point, even with a zero Angle Error, the Apex value will almost certainly also fail Apex Offset specifications.   But if it is not required, I would recommend to not use Key Error as a pass / fail spec in production, and rely only on the Apex Offset specification.  However, I would certainly monitor and analyze all the geometry data—including Key Error—as part of my standard process control, striving to keep Key Error to a minimum and investigating causes if values rise.

Quick Links to APC Blogs include:

Answered by AskFOC Technical Team November 17, 2016ask_FOC_trans 

I have a question about the AB9112 Epoxy, what is the proper storage method? In the datasheet, under section 7:Handling and Storage, it doesn’t really specify the proper storage of the epoxy. We had a couple epoxy packs that went grainy before it’s due date, are these still usable? Would storing them in a fridge prevent this?

Thank you for reaching out to us.  The AB9112 should be stored according to the Storage recommendations on the attached data sheet.  In regards to a couple packs appearing grainy, this may be crystallization.  Here is blog on the subject of crystallization and how to heat treat to remove it and use the epoxy, but I have also pasted the treatment method below – https://focenter.com/crystallization-in-epoxies-steps-for-you-to-spot-it-and-fix-it/

  • Crystals can be eliminated by increasing the temperature of the liquid resin to about 50°C (about 122°F) until all signs of the crystals are gone. We suggest checking the material at 10 minutes, at 20 minutes, at 30 minutes, and at 1 hour. Typically, it takes only 20-40 minutes to eliminate crystals and fully return the epoxy to a clear liquid, but it could take several hours. (Note that this low-temperature heat treatment does not damage the epoxy or impact its material properties. Also, the epoxy won’t cure, because you have not yet mixed the material.)
  • Allow the resin to cool to room temperature, then proceed to use normally. It can be stored in its original packaging for later use.

Here is also a link to a white paper if you wanted to look into this topic further. https://focenter.com/crystallization-in-epoxies/ 

crystallization-in-epoxiesCrystallization in epoxies is a common occurrence –and easy to remedy:  If your production facility discovers a container of epoxy that appears cloudy or is nearly solid, there’s no need for concern.  In fact, in this technical paper, we hope to dispel the perception that crystallized epoxy is not usable or that its material properties are compromised.  Crystallization indicates purity of product.

Please let me know if you can do the treatment and if you have any questions.  If you find that this is something else, please let me know and we can look into it further.

Answered by AskFOC Technical Team November 8, 2016ask_FOC_trans 

We are seeing some failures on the total co-planarity and fiber line on some of our MT interometric test. Some in the industry have commented these items are not included in the standard and they even don´t know what do they mean. Could you please provide your comments on this?

There are two types of IEC standards for MT/MPO measurements using interferometry.  The first is the “Measurement Standard” and its primary purpose is to try and ensure that different instruments yield the same measurement results.   The second is “Performance or Interface Standards” which relate to specific connector styles or groups. 

My blog, Navigating IEC standards for MT/MPO measurements using interferometry, covers this topic with more details and can be found at bit.ly/1U2l9Y1.

Answered by AskFOC Technical Team March 8, 2016ask_FOC_trans 

We are getting epoxy 353nd from you in a package of 2gr. Is it the minimum package? We are concerned about wasting material because we are using 353nd only for MTP assembly. Do you have any suggestions to reduce waste?

It is not possible to make a smaller package of 353ND.  353ND has a mix ratio of 10:1.  For a 2 gram package the 1 part of hardener has to be measured to +/- 0.01 grams, to maintain this mix ratio.  To do better than this is not practical in the repackaging business.

I can suggest to mix the 2 gram packet, use what you need immediately, then as quickly as possible put the rest of the mixed 353 into a syringe that can be used for dispensing later.  Freeze the syringe in at least a -20°C freezer (-40°C is preferred, if you have one).  Depending on how cold you are able to store the syringe, you will be able to prolong the pot life of the 353 by days, weeks, or months (in the case of -40°C).  When you need a little more 353, remove the syringe from the freezer, let warm up briefly, and hopefully dispense another small quantity.  You can refreeze and keep using, as long as the 353 doesn’t cure in the syringe.

Answered by AskFOC Technical Team January 11, 2016ask_FOC_trans 

Is Domaille APM-HDC-5300 the only polisher for MTP/MPO? I know normal polishing machines for patch cords and Domaille is one of the more expensive when we compare to others. I understood that Domaille's technology is very good but I just wondered if we can use another brand or not.

Your question is understandable as there is a significant price difference. There are options, assuming you do not need the top computerized model. The APM-HDC-4000 would give you the same performance for less with almost the same process controls.  The initial purchase will still be more expensive than other polishing machines, but with the 4000 you will benefit from the lowest production cost by spending less money on inspection and rework. Rework is very expensive on MTP assemblies and, according to our customers, other machines are over 30% more expensive on reworks.   Also, work-flow and process times are optimized with the Domaille platform, further decreasing your continual manufacturing costs.

Please note my Blog, Polishers: Discussion on Expense and Top Technology (https://focenter.com/polishers-discussion-on-expense-and-top-technology/)

Answered by AskFOC Technical Team December 6, 2015ask_FOC_trans 

Do you have a lapping film that can remove a larger than normal epoxy bead more effectively than 15um Silicon Carbide? We have a unusual connector that does not have a crimp to secure it to the cable and relies on the epoxy for this. Therefore, we use more epoxy for the termination and excess flowing out to the tip during curing. Using a harder pad is one of the solutions we tried but the connector radius becomes lager and we require a 100% geometry pass. Any suggestion will help.

Correct using a harder rubber pad (or changing the pressure) will change the ROC.  We recommend a more aggressive lapping film, more polishing time or likely a combination of both.  A 30 um Silicon Carbide lapping film will likely do the trick.

Answered by AskFOC Technical Team October 12, 2015ask_FOC_trans 

I am noticing a large epoxy ring with visual inspection. Can you help me understand what I am looking at?

Occasionally we receive visual inspection pictures from multimode connectors that shows an evident rough epoxy ring around the fiber.  To get a bit more in depth with the answer, I have five bullets of tips and info plus a photo in my blog post to help with this: https://focenter.com/noticing-a-large-epoxy-ring-with-visual-inspection/  Another influence, outside of the details in my blog, might be that the ferrules are insufficient filled with epoxy into the ferrule might relate to air bubbles as well. Please see another FOC blog that describes more details about this: https://focenter.com/assuring-the-correct-amount-of-epoxy-is-in-the-connector/

Answered by AskFOC Technical Team September 3, 2015ask_FOC_trans 

I am interested in efficiently coupling a 125 or 200um core-diameter fiber onto an LED die. My understanding is that the coupling efficiency is limited by the NA and core diameter of the fiber in most circumstances. Is it possible to use a tapered fiber, e.g. starting at 1000um core and moving to 125 or 200 um core to increase the irradiance at the small diameter fiber side?

Transmission light from the LED die into any fiber is controlled by both the core and NA as well as the NA of the light coming out of the source.  Obviously, the larger the fiber NA and core the better the coupling efficiency.   We’ve done a lot of work using LED dies in conjunction with 1000um POF fiber which is a perfect match.  Due to most application requirements, we’ve been forced to develop methods of coupling to 200um fibers with a .37NA and .48NAs.  Inexpensive tapers did not work unless they were very long which are very expensive. Also, tapers had to be manufactured with a gl/gl fiber of .22NA which defeat the purpose of the design criteria.  The shorter the taper, the more severe the internal angle thus the coupling efficiency is very poor.  This can be easily modeled by performing a ray trace on zemax.    Here is what we’d recommend, assuming the power is fairly low, a plastic lens would be the most cost effective as well as having the best coupling efficiency.   There will be other issues that will have to be dealt with here related to the output pattern of the LED die. 

  1. Oval or rectangular shape.
  2. Hot spots
  3. Cladding modes of the fiber.
  4. Fiber output, if the length is short will be very strange as well.

In short, there are quite a few issues to consider and we are more than happy to put you in contact with someone to discuss further.     

Answered by AskFOC Technical Team July 24, 2015ask_FOC_trans 

How can I tell I have over-polished a connector?

Primarily, the indicator of over polished connectors is poor repeat ability in measurements of the return loss and insertion loss. For the majority of “spring loaded ferrule connectors” e.g.; LC, SC, MU, FC. Determining over polishing of the connector is difficult to gauge.    Read Mario Goduco’s full blog to answer this question here: https://focenter.com/how-can-i-tell-i-have-over-polished-a-connector-asked-more-often-than-you-might-think/

Answered by AskFOC Technical Team July 21, 2015ask_FOC_trans 

My epoxy is ‘behaving irregularly’, curing differently, has a different color, etc. Can you help?

It is possible for a batch of epoxy to be faulty, but it is very rare.  Most likely you are experiencing some variation in the epoxy that is allowed by the epoxy’s specification.  Epoxies are manufactured in batches, with specified manufacturing windows for viscosity, work time, and every other parameter.  This means the final product can and probably will show some variation.  If your manufacturing process has been very specifically tailored for a given batch of epoxy, and a new batch of epoxy has slightly different properties, you may find yourself in a borderline situation with the new batch of epoxy.   No doubt this kind of variation in results is very unwelcome to an up and running process.  However, minor changes to the process frequently solve the issue at hand, and make for a more robust process overall.  One approach is to take the epoxy and cure it all by itself (not in your application) and ensure it meets its own spec.  This simple experiment may also offer clues to help you to determine what might be needed to tweak your process – i.e. if the epoxy takes a little longer to cure, dwell a little longer in the oven, or raise the temperature a little, to ensure complete cure.  Unfortunately color can’t be used to indicate much.  Again, epoxies are made in batches, and the materials used by the manufacturers to synthesize the epoxy are subject to small variations as well.  Small changes in the manufacturer’s raw materials and process are frequently what is responsible for variations in color. 

Answered by AskFOC Technical Team July 15, 2015ask_FOC_trans 

Is AL-6261 the same as OKP4?

Yes.  We re-label the OKP materials under the AngstromLink (AL) label, where the last two digits of the product name indicate the refractive index: askfocchartokp If you get a 25kg bag of any OKP product it will arrive in the original Osaka Gas packaging and you will see the original Japanese labeling on the bag.  If you purchase a 5kg bag it will arrive in a sealed metalized bag (which I repackage myself for quality control purposes) and you will have to trust us.  In this case we are happy to provide the original Osaka Gas lot number on the COC.   

Answered by AskFOC Technical Team July 13, 2015ask_FOC_trans 

We have an 8º MT polishing fixture and are getting polished angled less than 7.9º. Is there a problem with the polishing plate?

Assuming you are using high quality polishing equipment, it is most likely NOT an issue with the fixture.  The angle of the MT chip can be greatly affected by the Silicon Carbide grinding steps, and even more so when polishing a non-pre-angled ferrule.  If, as in this case, the angles are too low, we’d recommend decreasing the polishing time during these early grinding steps.  If the angled is too great, the time should be decreased.  As long as the standard deviation for the angle is reasonable, you can move that average one way or the other by adjusting the process.  If your standard deviation is large, meaning the results aren’t consistent, you likely have other issues. 


Answered by AskFOC Technical Team June 30, 2015

We are polishing some 12 fiber MT ferrules and found that the edge fibers (1, 2, 11 and 12) are on the lower end. Is this normal?

While an infinite or perfectly flat radius across all fibers is the goal, it’s next to impossible to achieve this.  Even though we are polishing on a glass plate the flock material has some softness.  Like when you polish a ceramic connector on a rubber pad, you generate a radius.  Hence, the shorter heights on fiber 1,2, 11 and 12.  There are some PROCESS things they can do to minimize this, like decreasing the pressure a bit, but it will never completely go away. 


Answered by AskFOC Technical Team June 29, 2015

Why does my epoxy have crystals in it?

Crystallization of liquid epoxy is a known phenomenon that frequently surprises users who are not very familiar with epoxies.  Crystallization may look like crystals, snowflakes, cloudiness, fog, turbidity, and even a solid, or a solid sediment, in the epoxy resin.  The reason some epoxy resins crystallize has to do with their ‘super-cooled’ nature – they are supposed to be solids at room temperature, but have remained liquid below their solidification (freezing) point.  Therefor super-cooled liquids have a natural tendency to crystallize.  The timing of crystallization is highly variable and unpredictable.  Factors effecting crystallization include resin purity, viscosity, additives, moisture content, the presence of ‘seed’ crystals, and environmental variables such as storage temperature and even a sudden cold shock.    Crystals can be easily eliminated by increasing the temperature of the liquid resin to about 50°C (about 122°F) for a period of hours or until all signs of the crystals are gone.  Allow the resin to cool back to room temperature, and proceed to use normally.  There is nothing about crystallization that is damaging to the epoxy.  It is the same as water freezing, and melting ice: the water is exactly the same before and after crystallization.


Answered by AskFOC Technical Team June 21, 2015

How long should it take to polish a plate of 48 LC start to finish?

The short answer is around 15-20 minutes including loading and unloading.  The actual polish time usually doesn’t change as the quantity of connectors being polished increases.  The only thing that increases is the load time.  However, you should think about the types of cables you are polishing before moving to a large capacity plate.  For example, if your cable a bulky drop cables with short breakouts, feeding all the legs to the plate can be difficult and thus add more time to the entire process over plates with smaller qualities.


Answered by AskFOC Technical Team June 19, 2015

My epoxy is past expiration. Can I use it?

Once the epoxy is past expiration, FOC does not recommend using it without testing the material. You can cure it and if it sets as expected, it can be used.  However, the hard part will be determining if it cured/set properly.  When in doubt, throw it out.


Answered by AskFOC Technical Team

What info is needed to determine the correct epoxy for an application?

Here is a list of question we will need answered:

  • ‘Can you tell me something about your application?’
  • What substrates are to be bonded?
  • What is the main purpose of the adhesive – alignment, in the optical path, index matching
  • UV or heat cure?
  • What is the maximum acceptable temperature for cure?
  • Strength of bond?
  • Harness of material?
  • What viscosity?


Answered by AskFOC Technical Team

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Frequently Asked Questions

Here at Fiber Optic Center, we are asked questions and provide technical help to our customers every day.  We are providing the top ten FOC FAQs here and hope this is helpful. Although there are other questions we are constantly asked like ‘How quickly can Mario get to my location to help us?’ and ‘What can I do to request Dan help me today?’, we did not think that those would be most helpful here. If you do not see your answer here, please follow the instructions above by emailing your question to AskFOC@focenter.com.  We will have one of our technical experts answer quickly.

FAQ: How do you connect with your Fiber Optic Center Customer Service manager?
FAQ: How do you connect with your Fiber Optic Center Inside Sales manager?
FAQ: Are samples and/or demos available?

Samples and Demos are available for most of our products.

FAQ: Can you ship today?

If we have the product in stock and the order is placed by 4:00PM (ET) it will ship.

FAQ: How quickly can someone from FOC come to my location and fix my problem?

When a customer requests a site visit, we aim to get someone there ASAP. Depending on the nature and urgency of the call, this usually ranges between 1 to 3 weeks.

FAQ: Can you provide equipment to me at the same price as the manufacturer?

Yes with all our manufacturing partners we offer the same list price as they do. Our philosophy is doing business with Fiber Optic Center should NOT cost you more money.  On the contrary, our aim is to save you money with our technical recommendations and our superior customer service.

FAQ: When can I expect to receive a pricing quote?

Pricing quotes for standard items should be available within a couple hours from submitting the request (within the working day). Of course, complex quotes for a complete manufacturing line or custom products will take longer, but should be received within one business day.  There may be exceptions for new products.

FAQ: Why can’t I see pricing online?

At this time you cannot get pricing online. We are working on a system where some simple items will have pricing and be available to purchase online.  We prefer to fully engage with the customer to find a total solution.

 Cleaning Questions

Fiber Optic Center, with the Sticklers MicroCare Corporation Team, have answered some frequently asked cleaning questions below:

Why is it a bad idea to dip the cleaning tip of a mechanical click cleaner directly into the cleaning fluid when doing a wet to dry cleaning process?

All of the mechanical click cleaners currently on the market use a synthetic woven fabric cleaning strand or cleaning ribbon. The cleaning strands or cleaning ribbons will flow across a tip on in a single direction. This motion effectively wipes away the contamination from the ferrule end face.

The synthetic woven micro strand has excellent absorbency for wiping away common residue based contaminates like skin oil, humidity, or alcohol residue. If an operator inserts the cleaner’s cleaning trip directly into the cleaning fluid, he will have a problem. The cleaning fluid will absorbed up onto both sides of the cleaning strand. You will not be able to control how much cleaning fluid is being wicked up onto the strand. The cleaning strand will become over-saturated with the cleaning fluid on both sides. When this happens, the operator is going to have to engage the cleaner multiple times to get to a dry section of the cleaning strand. 

If you have put the cleaning tip directly into the cleaning fluid, your best option is to stop using the cleaner for a few minutes and let the cleaning fluid evaporate off. You can tell when the fluid is gone by touching the tip periodically until it feels dry. You don’t need to worry about cross contamination touching the cleaning strand to see if I feels dry. When you engage the cleaner, the part of the strand that has your skin oil be move away in the engagement process.  The next step is to engage the cleaner five or six times in a row to make sure all of the over-saturated section of the cleaning strand has passed.

Answered by AskFOC Technical Team WITH the Sticklers MicroCare Corporation Team June 4, 2017

For the response including images, visit: https://focenter.com/fiber-optic-center-askfoc-dipping-the-cleaning-tip-of-a-mechanical-click-cleaner-directly-into-the-cleaning-fluid-when-doing-a-wet-to-dry-cleaning-process/

What is the best way for doing a wet to dry cleaning process using a mechanical click cleaner and cleaning fluid? We purchased Stickler MicroCare from you.

The best way to do a wet to dry cleaning is to use a minimal amount of the cleaning fluid. A small amount of cleaning fluid is all you need to effectively breakup and loosen any end face contamination from the ferrule end face. That same small amount of cleaning fluid is also all you need to increase the local humidity levels for totally eliminating an electrostatic charge.

You will want to start by applying a small amount of the cleaning fluid to an optical grade clean wipe. Be careful not to over-saturate the wipe.  The next step is to take the tip of the mechanical click cleaner and touch it to the wet part of the wipe. You want to apply a small amount of the cleaning fluid onto the cleaning strand. The wet the section of the cleaning strand is what will make the initial contact with the ferrule end face. The final step is to insert the cleaner into the adapter if you are cleaning an in bulkheads connector.

After you clean the in bulkhead connector, you need to inspect and clean the connector on the cable assembly to prevent cross contamination. You will want to repeat the step of touching the cleaner’s tip into the wet part of the wipe. This will reapply a small amount of cleaning fluid to next section of the cleaning strand. The final step is to attach the end cap onto the barrel of the cleaner, insert the connector into the end cap, and engage the cleaner.


Answered by AskFOC Technical Team WITH the Sticklers MicroCare Corporation Team May 4, 2017

For the response including images, visit: https://focenter.com/fiber-optic-center-askfoc-wet-to-dry-cleaning-process-using-a-mechanical-click-cleaner-and-cleaning-fluid/

How does dust contamination negatively impact a mated connector pair and where does it come from?

Dust is the most common contaminate that negatively impacts optical connectors.  The dust particulates that are in the contact of a mated connector pair interferes with the signal path. Smaller particles in contact will obstruct signal path which creates a loss. Larger particles of dust may interfere with the mating process. 

Answered by AskFOC Technical Team WITH the Sticklers MicroCare Corporation Team April 12, 2017

For the response including images, visit: https://focenter.com/fiber-optic-center-askfoc-how-does-dust-contamination-negatively-impact-a-mated-connector-pair-and-where-does-it-come-from/

When should I use stick cleaner and what are some limitations to using these types of cleaners?

Mechanical click cleaners are good for cleaning light to medium levels of end face contamination when you have many connector pairs that need to be cleaned. The basic mechanical action of the click cleaners is to have the cleaning tip rotate 180° which the cleaning strand flows across the tip. The effect is a sweep and lifting motion for wiping away contamination off the ferrule end face. Most mechanical cleaners have a spring loaded cleaning tip for controlling the contact force. If the ferrule end face has lot of residues or has a high to severe level of contamination, the mechanical click cleaners may not be able to wipe away enough of the contamination from the ferrule end face. Higher levels of end face contamination are usually encountered in outside plant networks and legacy networks that have not been properly maintained over many years.

Most mechanical click cleaners have barrels and end caps that are designed to ensure the cleaner’s cleaning tip is wiping away end face contamination from the contact zone on the ferrule. The self-alignment feature eliminates the need for the good technique by the operator which means consistency with the mechanical click cleaner’s cleaning performance. Mechanical click cleaners usually offer a lower cost per clean when compared to other cleaning options like cassette based cleaners and stick cleaners.  The way to determine cost per clean is to take the price of the cleaner and divide it by the number of uses.

There are some limitation with mechanical click cleaners. The cleaning region of mechanical click cleaners will never be able to completely clean a ferrule end face. The cleaning tip has to be able to fit inside and rotate unobstructed through the adapter sleeve.  If your application is experiencing issues with particle migration, the better option may be to use a stick cleaner.   The mechanical click cleaners will not be able to remove any dust contamination on the adapter sleeve.

Answered by AskFOC Technical Team WITH the Sticklers MicroCare Corporation Team March 28, 2017

For the response including images, visit: https://focenter.com/fiber-optic-center-askfoc-when-should-i-use-stick-cleaner-and-what-are-some-limitations-to-using-these-types-of-cleaners/ 

Follow the Fiber Optic Center Experts:

Fiber Optic Center ‎@FiberOpticCntr

Ben Waite ‎@BenWaite_FOC

Mario Goduco @PolishExprtFOC

Dan Rocheleau @TermExpert_FOC

Kelly Barker @EpoxyExprtsFOC

Chris Rollinson @TestExpert_FOC

Wayne Kachmar @TechHorsepower