How to polish fiber connectors – Fiber connector polishing Tips and Practices

How to make your fiber optic polishing work to be correct and how to revise your fiber connector polishing

When you polishing a fiber connector or several connectors in polishing holder, by fiber polishing machine or fiber polisher, there are procedures and setting parameters designed to leverage the machines best practices as well as previous developments and experience.

Additionally, there are tips to consider applying during daily production to improve first pass yield, efficiency and results to avoid scrapping costs.

The standard polishing process includes three steps:

Epoxy Removal

Geometry checking

Final Step: finishing the fiber connector end-face, check optical surface

Below we share tips for each step of the fiber polishing process:

Epoxy removal

Pre- Polish

When connectors are loaded on the polishing fixture or fiber polishing holder jig after cleaving, there are large, sharp edge fibers and inconsistent fiber protrusion due to different fiber cleaves.  This can result in fiber breaks if polishing, by machine, is started immediately.

Tip: start polishing the connectors loaded on the jig with SC Film mounted on the rubber pad and then by hand/air delicately, with little hand pressure making few rotations (around 10).  Next the fiber protrusion has more consistent length distribution over all ferrules resulting in less fiber breakage (fiber into ferrule bore hole).  After this initial operation, one can start polishing with the machine using the same film used for air polishing.

LC Conical

The available surface of the 1.25 mm connector is small and sometimes due to this limited surface, epoxy is also going to the base of the chamfer area that you cannot remove using the polisher.

Tip: After the epoxy removal step on the polisher, if some epoxy is still present on the chamfer area, use a little scalpel to remove residues. This will allow to move to the next step (Geometry) avoiding any contamination on D films.

For other types of ferrule (2.0 or 2.5 mm) it is a good practice to check, after epoxy removal, if all the epoxy has been polished away (checking the front face of the ferrules).

Fiber Polishing Jig Holder Locking Mechanism with Individual Ferrule

A fiber polishing fixture or holder jig where the ferrules are independently moving from the each other is called Individual Pressure Control (IPC) fixture and is recognized by the use of spring loaded adapters to lock and to keep the ferrule in place.

Tip: after checking if there are not any epoxy residues left, it is a good practice to verify if all the connectors are well positioned (same height) and if the spring of each adapter is working properly with the ferrule moving freely – not stuck due to polishing residue. This guarantees each ferrule will be under the defined fiber polisher pressure in the polishing steps offering more consistent geometry results.

Geometry Checking

Air Bubble Under Fiber Polishing Film

A common occurrence after positioning on the rubber pad is air bubbles under the fiber polishing lapping film.

When this occurs, it must be removed because during the geometry polishing process as the air cushion can modify the ferrule geometry (radius and/or apex).

Tip: to avoid this effect, use a roller to press down the lapping film on the rubber pad. It is important to have a different roller for each type of film to avoid contamination especially from D film to final film.  If one uses the same roller, it is essential to clean it before moving to the smaller film grid.

Tip: when using just one roller, to avoid contamination, take two films one on top of the other (one on top upside down) and then use roller. The lapping film that will used for polishing connector will not be effected by any cross-contamination.

Fiber Polishing Film Longer Life

Diamond fiber lapping film is the most expensive film we use on the polishing process and one consideration when selecting a supplier is the number of times you can use it.   There are fiber polishing films used for 10, 15, 25 times, or even longer depending on the process and specific customer specifications.

Tip: after a certain number of usage, typically 10 times, if you clean the surface with alcohol you are able to extend the life of this film (using alcohol removes debris from previous polishing).

VIEW: Diamond Films Product Matrix

Fiber Polishing Rubber Pad

In a polishing process, we use rubber pads typically 60 to 80/85 durometer.  Keeping consistent geometry can be a challenge.

In principle, a rubber pad that is too soft can help to reduce radius but effect negatively the apex.

Using a harder pad with higher pressure should be better to get positive radius and apex results.

Tip: always try to develop a process using pads with same durometer throughout the entire process. Changing the hardness of the fiber polishing pad will effect radius and/or apex and can make it difficult to bring both parameters within the specification.  Usually adjusting pressure and timing, using the same pad, can achieve desired results.  If you do need to change to a softer pad, decrease the durometer maximum by approximately 10 durometer.

Choice of APC connector holder/Jig According to Connector Style

In the market there are two different types of ferrules: Stepped and Conical.

As soon as you select the connector style, you need to consider the related fiber polishing fixture holder jig.


Stepped Ferrule – require a jig with an APC angle of 8°

Conical Ferrule – require a jig with an APC angle of 8.3°



Scratches are a fiber optic assembler’s nightmare because if it occurs, they jeopardize all of the previous activities and are costly due to the waste of time and additional material.

Tip: each step requires good cleanliness to avoid contamination especially when you move from D film to Final polishing film.   Quite often this activity is underestimated but if you make this a priority, you can avoid costly issues.

Tip: use spray water to remove all the debris on the ferrule and mainly at the jig’s bottom surface.   Follow this by wiping the operation using Cleaning Wipes or similar paper moving from the center of the jig to the outside.

Final Fiber polishing Film Choice

In addition to the nice smooth surface, final film is extremely important to define the right fiber protrusion.  Based on the requested specification, you can choose different types of film that provide various results.

Tip: important to know the different specifications and what your requirement is: Fiber protrusion, Undercut, Flatness with respect to the Ferrule. Basically, fibers can protrude or stay below the ferrule surface according to the described parameter to guarantee the best fiber physical contact terminated in a connector.

Tip: if you don’t have access to different final lapping films, adjusting time and pressure, can also achieve specified results with some limitations.


Fiber optics requires physical contact between the two mating parts because if you have an air gap between, it will cause high back reflection.  The physical contact will happen when you have fiber protrusion but considering the compression force made by the connectors, you could have some physical deformation of the fiber and ferrule.  When that happens, there is physical contact with flat and undercut if the related values are according to the specified parameters.

One might ask, why not only use protruding fiber and the answer is that concern is about fiber breaks when the two fibers are pushed against the others?   They specify undercut or flat fiber vs. end face the ferrule to better protect the fiber but still having physical contact.  It is clear the parameters have to be according to the specifications (as seen on the graphic) otherwise you will experience air gap.



Hundreds of fiber optic patch cable assembly facilities around the world use Fibermart’s Fiber polishing films, including multiple Fortune 500 companies. Fibermart has polishing process technical experts on staff as well as lapping film experts.

Please note a few of our resources whether you are implementing a new polishing process, fine-tuning your process to ensure it produces repeatable results, or looking for help to resolve a polishing issue by writing to us: or

Proper Care of Polishing Fixtures for Optical Fiber Polishing Machines

In fiber optic cable assembly, the polishing process is perhaps the most critical step to assure high-quality assemblies that meet specifications. That’s why it’s important to select the right optical fiber polishing machine – and polishing fixtures – that meet your needs. Depending on your cable assembly house product offerings, it’s likely that you have several polishing fixtures to produce different connector styles.

The quality of the polishing fixtures (also called polishing plates or jigs) is extremely important to your company. Considering the high cost of production equipment and components, your company will want to maintain these tools to produce a high volume of products with minimal quality issues over the long run.

Proper maintenance of polishing fixtures is absolutely essential

Polishing fixtures for optical fiber polishing machines are built with high-precision machining equipment. Fixtures made of steel and aluminum can flex and warp over time, which will negatively impact your polishing process and product quality. On the other hand, polishing fixtures made of hardened stainless steel avoid this wear effect. However, hardened stainless steel contains more iron in the alloy, so this does increase the risk of rusting. This is a key reason why proper maintenance is so critical.

In addition, the most common fiber optic connectors (SC, LC, and E2000) are locked onto the polishing fixture with a plastic latch or clamp, which can wear over time if not properly cleaned. Poor cleaning techniques can also prevent proper locking. This can significantly impact the polishing machine’s functionality and, therefore, product quality.

Polishing fixtures are expensive – this is a bottom-line reason why proper maintenance is so important. With daily maintenance, you can use your polishing fixtures for a long time with no variation in the quality level of your fiber optic cable assemblies.

Follow these 8 steps to clean and maintain your polishing fixtures

Whether your company is just starting to manufacture fiber optic cable assemblies – or you have years of experience – we recommend you rigorously follow these guidelines to properly clean and maintain your polishing fixtures.

It’s better to clean every day for 5 minutes rather than clean once a week for 30 minutes. In fact, we recommend you integrate a cleaning procedure throughout the daily polishing process. Cleaning the fixtures should be a regular task – and a priority – in your polishing process.

Use distilled water, because it doesn’t contain abrasive minerals. Do not use tap water – regular drinking water is different all over the world. Your company’s tap water may contain iron minerals that tend to adhere to the polishing fixture. Also, do not use alcohol. At Fiber Optic Center, we recommend the Air Cleanse Cleaning Wand. This hand-held cleaning wand has an integrated pressurized fluid and filter system for a debris-free cleaning operation. You can use the wand to clean any brand of polishing machine and fixture. Click to read the datasheet for the Air Cleanse Cleaning Wand from Domaille Engineering.

The ferrule holes (and for MT style fixtures the ferrule slots, surrounding surfaces, and top clamps) can be cleaned using dental brushes and particle‐free, distilled or deionized water. Again, do not use alcohol. We recommend using a 1.25mm nylon brush (purple-handled brush) for fixtures with 1.25mm diameter ferrule holes. Use a 2.5mm nylon brush (blue-handled brush) for fixtures with 2.5mm diameter ferrule holes. Either one will work fine for MT style fixtures.

Clean the fixture while it’s still wet from the polishing process. This makes it easy to remove the polishing debris.

To clean areas where a brush can’t reach, use an ultrasonic bath. When using an ultrasonic bath, you must change the deionized water every day. Otherwise, debris could contaminate the polishing fixture. (Again, here is the link for the Air Cleanse Cleaning Wand datasheet.)

If you have a fixture with a cam-lock interface, pay special attention to the spring slits. These are very narrow and debris can easily build up, causing the metal to flex less and interfere with the spring functionality.

After cleaning the polishing fixture, it’s important to dry it thoroughly to avoid rusting. This is especially true for polishing fixtures made of hardened stainless steel.

Over time, your polishing results may change, and the reason could be directly related to natural wear of key interfaces of the polishing machine and fixture. The EZ-Check Precision Wear Gage Kit provides precise measurements for the polishing machine mandrel, fixture mounting hole, and ferrule holes. We recommend incorporating this wear gage kit into your process control system. Call Fiber Optic Center to determine whether this tool works with your polishing machine and fixture.

Fiber Optic PC Connectors: Single-channel vs. Multi-channel

Over the past 30 years, fiber optic technology has spanned its commitment constantly with, even more, endeavors nowadays to meet the ever-increasing networking bandwidth for high-quality Internet applications. In these applications, fiber optic connectors, serving as mousetraps, are used to couple the source, receiver and other components to the fiber optic cable. Fiber optic connectors generally use either physical contact (PC) or expanded beam technology. This article mainly discusses PC connectors from single-channel and multi-channel aspects.

It’s necessary to figure out what PC connections are first.

What Are PC Connection?

A PC connection is accomplished by terminating the optical fiber into a precise ceramic ferrule. The tip of the ceramic ferrule is polished in a precise manner to ensure that light enters and exits at a known trajectory with little scattering or optical loss. In achieving PC connection, there are two requirements for a cleaved fiber end face for PC connection. One is that the fiber end face inclination is less than 0.6°, and the other is that there is no mist on the end face.

PC Connector Types

There are countless single-channel and multi-channel fiber optic PC connector types available for telecommunication and data communication industries.

Single-channel Connectors

PC connectors are characteristic of directly mating and polishing fibers by utilizing tight tolerance ferrules and alignment sleeves and/or mating pins. This ceramic-ferruled technology permits reliable optical performance, with several designs becoming widely used as industry standards. Typically, these connectors are single fiber solutions with plastic shells. FC and ST connectors are becoming less popular but are still used in instrumentation. LC and SC connectors are commonly used in the telecommunication industry.

As a push-pull connector, LC connector, licensed by Lucent Technologies, provides a pull-proof design and small size perfect for high-density applications. It’s available in simplex or duplex versions, widely used in 10Gigabit, 40Gigabit, and 100Gigabit applications. Like Cisco QSFP-40GE-LR4 transceiver, QSFP-40GE-LR4 listed on establishes 40Gigabit Ethernet (GbE) links with this duplex LC connector for 10km maximum link length over single-mode fiber (SMF).

SC connector, developed by Nippon Telegraph and Telephone (NTT), is recommended in the TIA/EIA-568-A Standard for structured cabling. It’s also available in simplex or duplex versions, typically used in Analog CATV (Cable Television) and other telecoms applications including point to point and passive optical networking.

Multi-channel Connectors

Multi-channel connectors house multiple fiber optic termini in a precision insertion. The termini can be configured as a pin/socket combination or genderless. MTP/MPO connectors belong to PC multi-channel connector.

The US CONEC MTP is an MPO compatible connector that exhibits quick and reliable connections for up to 12 fibers in a very small form factor. Just like LC connector, 40G links are likely to deploy this kind of MPO-12 connector for high performance. Take Cisco QSFP-40G-CSR4 for example, this QSFP-40G-CSR4 transceiver sets up 40G links in 850nm multi-mode fiber (MMF), with MPO-12 as its connector.

Optical Performance

Both single-channel and multi-channel PC connectors have optical performance characterized by return loss. The return loss of the connector is a measurement of how much light is reflected back at the connector interface. It’s affected by alignment, contamination, and polishing. For example, if the mating faces of the two fibers are not parallel, some energy reflects back to the source. Additionally, contamination at the mating interface causes reflection and scattering of light. What’s more, a poor polish may create an end-gap separation or an end angle.

Featuring by the tightest tolerance ceramic ferrules and alignment sleeves, coupled with the highest quality termination and polishing procedures, PC connections are able to deliver unrivaled optical performance.


Fiber optic connectors make quick fiber connection and efficient light transmission possible, gaining more and more popularity among their users. offers hundreds of fiber optic connectors, such as FC, D4, DIN, MU, the MTP/MPO ST, SC and LC, as well as their related optic modules (eg. QSFP-40GE-LR4 and QSFP-40G-CSR4 mentioned above). You can visit for more information about fiber optic connectors.

What fiber Patch Cables should we use in a harsh environment?

With the rapid development of optical communication, more and more fiber optic cables are increasingly used in different environments. Under harsh conditions, the ruggedness and durability of common fiber optic cables cannot meet operators’ requirements, especially for exceptional demanding applications. This post mainly introduces IP67 waterproof fiber optic cable & armored Fiber Patch Cablesuitable in harsh environment. All the types of waterproof fiber optic cables are available in Fiber-Mart.

The two fiber patch cables are armored fiber patch cable and IP67 fiber patch cable. As most fiber cable failures are usually caused by fiber breaks and contaminants, the fiber cable and the termination points of the fiber links should all be well protected. And the two types of fiber cable can perfectly meet most requirements of harsh cabling environment.

IP67 Fiber Patch Cable

IP67 waterproof fiber optic patch cable can be used in harsh environment, providing more convenience and extra protection for network systems. Even if there are various patch cables available on the market, which can be used in different applications, in most cases, they can only be installed in relatively protected environment where stay away from liquid, chemicals and animal biting. What if I want to use it in military network or extremely harsh environment? The following text will introduce a saviour in hostile surroundings—IP67 waterproof fiber optic patch cable.

Overview of IP67 Waterproof Fiber Optic Patch Cable

Waterproof fiber optic patch cable is mainly used in outdoor connection. It is designed with a stainless steel strengthened waterproof unit and armored outdoor PU jacketed cables. It can resist high temperature, and is suitable for use in harsh environments. Similar to standard fiber optic patch cables, waterproof fiber cables also have various types, including simplex, duplex, 12 fibers, 24 fibers, and various kinds of connect interfaces are optional, such as LC, SC, FC, ST, MPO, etc.

IP67 waterproof fiber cable meets ODVA (Open DeviceNet Vendors Association) standards and the IP66/67 environmental sealing ratings. IP67 waterproof fiber jumper connectors are designed according to the IEC60603-7 interface standard, which allows mating to other similar mechanical locking systems. In all, IP67 waterproof fiber optic patch cable is a low-cost and ideal alternative for industry, FTTA, or other harsh environmental conditions.

Why & Where to Use IP67 Waterproof Fiber Optic Patch Cable?

Compared to common fiber optic cables, IP67 waterproof fiber cables are endowed with the following features:

Corrosion-resistant, waterproof, dust-proof

High temperature stability, low insertion loss

Easy operation, reliable and cost-effective installation

Thread locking mechanism to ensure long-term reliable connection

Long-lasting and durable

Rugged design for extreme environments

High sealing performances for vacuum & under water applications

All of the above features make waterproof fiber cables suitable for outdoor application, such as:

Emergency repair quick connection system

Radio and television industry

Military exercise communication devices

Power industry emergency communication system

Oilfield, mining communication connection

Remote wireless base station

Railway signal control application

Intelligent substation communication

Video monitoring system

2.Armored Fiber Patch Cable

Unlike traditional fiber patch cables which are fragile and usually need careful operation, armored fiber patch cables are usually much more durable and flexible. Armored fiber patch cable usually has two jackets, one inner jacket and one outer jacket, between which there is a build-in steel tube. Some vendors also provide armored fiber cables with aluminum tube. This robust metal tube can provide optical fibers inside armored fiber cable from the impact and bite from animals. The most commonly used designs of armor used in armored fiber cables are interlock and corrugated. For most outside plant applications, the corrugated armored fiber cables are suggested. Now a lot of armored fiber patch cable uses interlock armor. During operation in data center, armored fiber patch cable can provide a more flexible cabling environment, because it has bend restrictor which can provide optical fibers from over bending. The following picture shows the structure of an armored fiber patch cable.

With its durability and flexibility, armored fiber patch cables and armored fiber cable are widely deployed in today’s network. For data center applications, there is a wide selection of armored fiber patch cables, which are available from different connector type, fiber type, jacket type, fiber count, etc.


It is usually inevitable to deploy fiber cables in harsh environments for both indoor and outdoor applications. Rodents, like squirrels in outdoor and rats in data centers, are cable destroyers which like to bite or chew fiber optic cables. Except that, there are also many other challenges which can harm fiber optic cables and cause fiber failures, like dusts, water or other liquid, accidental impact, etc. Thus, enough protection should be provided for fiber optic network. Two types of fiber patch cables, which are specially designed for harsh cabling environments, can easily find in Fiber-Mart. Welcome to contact with us:

Parameter setting of OTDR optical fiber test method

OTDR is the main instrument in the field of optical fiber testing technology. It is widely used in the maintenance and construction of optical cable lines. It can measure optical fiber length, optical fiber transmission attenuation, joint attenuation, and fault location. OTDR has the advantages of short test time, fast test speed, and high test accuracy.

Optical Time Domain Reflectometer (OTDR), using the method of optical time domain measurement, emits a certain pulse width of light into the tested fiber, and detects the Rayleigh scattering (Rayleigh scattering) and Fresnel reflection (Fresnel reflection) optical signal power along the time Axis distribution, draw OTDR curve, to measure various optical cable and joint parameters to locate optical fiber fault points, and understand the distribution of optical cable loss. The following takes OTDR tester as an example to analyze and explain.

1. Test wavelength selection

Since OTDR is for optical fiber communication, select the test wavelength before performing fiber test. Only 1310 nm or 1550 nm is selected for single-mode fiber. Since the 1550nm wavelength has a much more sensitive influence on the bending loss of the fiber than the 1310nm wavelength, it does not matter. Whether it is fiber optic cable line construction or fiber optic cable line maintenance or experimentation and teaching, use OTDR to test the entire fiber backscatter signal curve of a certain optical cable or a certain optical fiber transmission link. Generally, the wavelength of 1 550 nm is used.

The shape of the test curves at 1310nm and 1550nm wavelengths is the same, and the measured optical fiber connector loss values ​​are basically the same. If no problems are found in the 1550 nm wavelength test, then the 1310 nm wavelength test must be no problem.

Choosing the 1550 nm wavelength test, you can easily find whether there is excessive bending of the fiber throughout the entire process. If a large loss step is found somewhere on the curve, repeat the measurement with a wavelength of 1310 nm. If the loss step disappears at a wavelength of 1310 nm, it means that there is indeed an excessive bending situation, which needs to be further searched and eliminated. If the loss step is the same at the 1310 nm wavelength, there may be other problems in the fiber, which need to be found and eliminated. In the single-mode optical fiber line test, the 1550 nm wavelength should be selected as much as possible, so that the test effect will be better.

2. Test range selection

The range of the OTDR refers to the maximum distance that the abscissa of the OTDR can reach. The measurement range should be selected according to the length of the optical fiber under test. It is better for the measurement range to be 1.5 times the length of the optical fiber under test. When the range is selected too small, the display of the optical time domain reflectometer is not comprehensive; when the range is selected too large, the abscissa on the display of the optical time domain reflectometer is compressed and can not be seen clearly.

According to the actual experience of engineers and technicians, when the test range is selected so that the backscatter curve accounts for about 70% of the OTDR display screen, both the length test and the loss test can get a better direct-view effect and accurate test results.

In the optical fiber communication system test, the link length is several hundred to several thousand kilometers, the relay section length is 40-60 km, and the single-reel optical cable length is 2 to 4 km. A reasonable selection of the OTDR range can get good test results.

3. Test pulse width selection

Setting the light pulse width too large will produce strong Fresnel reflection, which will increase the blind area. Although the narrow test light pulse has a small blind area, the light power of the test light pulse is too narrow, and the corresponding backscatter signal is also weak. The backscatter signal curve will be undulating and the test error is large. The set optical pulse width must not only ensure that there is no excessive blind zone effect, but also ensure that the backscattered signal curve has sufficient resolution and can see every point along the optical fiber.

Generally, according to the length of the fiber under test, an appropriate test pulse width is selected first, and an optimal value is determined from the pre-test once or twice. When the distance of the tested fiber is short (less than 5 000 m), the blind area can be less than 10 m; when the distance of the tested fiber is longer (less than 50,000 m), the blind area can be less than 200 m; the distance of the tested fiber is very long (Less than 2 500 000 m), the blind area can be as high as more than 2 000 m.

In single-disk testing, proper selection of the optical pulse width (50 nm) can make the blind zone less than 10 m. By taking the average of two-way test or multiple tests, the impact of the blind zone will be smaller.

Generally speaking, the longer the averaging time, the higher the test accuracy. In order to increase the test speed and shorten the overall test time, the test time can be selected within 0.5 to 3 min.

In the optical fiber communication connection test, a satisfactory result can be obtained by choosing 1.5 min (90 s).

If Fiber-mart OTDR is used for testing, the recommended duration is 1min (60s).

Only by accurately setting the basic parameters of the test can conditions be created for accurate testing.

Safety instructions before fiber optic testing

Hello everyone, today we will discuss with you the safety instructions before fiber optic testing. Some people may not understand why the safety instructions of the optical fiber should be emphasized. This is because once the operation is improper, it will not only cause irreversible damage to the naked eye, but also affect the service life of the optical fiber inspection equipment, or even directly damage the equipment.

01.How to avoid damage to the eyes

• Under no circumstances should you look directly at the optical fiber.

• The wavelength used is invisible to the naked eye (the light that actually transmits data is invisible to the naked eye).

• If the power of the energized optical fiber is large enough, the light emitted by it will cause permanent damage to eyesight.

• If the equipment currently in use is occasionally exposed to its radiation, it will not cause damage to eyesight.

• If you are told that the optical fiber is not energized, please treat it as if it is energized.

• Never stand in front of an optical fiber patch panel unless all optical fiber connectors are equipped with protective caps.

• Comply with the safety requirements set by your organization.


On the device level of fiber inspection

• The equipment test recommendations are all passive tests, that is, there should be no light in the optical fiber.

• Light on the optical fiber will cause inaccurate testing.

• If there is too much light, it will damage the optical power interface of the test instrument.


Choose the most suitable test instrument

Why is it strictly forbidden for us to directly observe whether the light source has output during the test? Because the wavelengths used in optical communications are all invisible wavelengths, the wavelengths of multimode fiber transmission are 850nm and 1300nm, and the wavelengths of single-mode fiber transmission data are 1310nm and 1550nm, so even if we observe with the naked eye, there is no light output. , But in fact, this kind of light may cause permanent damage to human eyes, so be careful.

Of course, as long as we pay attention to the above two safety issues, it is still very safe to use the fiber tester itself. Of course, in the process of use, even if there is a strong light device at the opposite end, the power meter of Fluke Networks still has a large range. It will be easily damaged. At the same time, the OTDR type instrument will automatically give an alarm, prompting that the opposite end is detected and the test cannot be performed, which has a good protective effect, so there is no need to worry about the instrument being damaged.