Difference in Fiber Optic Adaptors

Adaptor Differences
Fiber optic adaptors (Also known as a fiber optic coupler or mating sleeve) are designed to connect two fiber optic cables together. Fiber optic adaptors are designed for multimode or single mode cables and have various features that help distinguish them from one another. When looking at adaptors there are several options and styles that can help determine which one will be appropriate. There are material differences. Different colors help to distinguish between fiber cable types, connector types and hybrid adaptors. Adaptors come in various versions to connect single fibers together (simplex), two fibers together (duplex), or sometimes four fibers together (quad). All adaptors play a vital role in fiber optics, which helps to carry optical signals all over the world.
Alignment Sleeve Material
One main difference between single mode and multimode adaptors is the material used for the sleeve that mates two male connectors together. Single mode typically uses a zirconia sleeve and multimode uses a phosphorus bronze inner sleeve. More recently, zirconia is even being used for multimode applications as well. This is important, as tolerances play a vital role when mating a fiber connector, especially those with a small core size. Since single mode connectors have a smaller core size, usually 9um, the tolerance for the two cores to be lined up has to be very tight. This is achieved by using the zirconia sleeves which have very tight tolerances. With multimode connectors having a bigger core size, they are usually 50um or 62.5um; the tolerance level can have more play than in single mode applications. Another difference that explains this is the type of light source being used on the network. Single mode fiber uses a laser light source and traditional multimode optic cable uses LED light to pass the signal. To go even further, OM3 and OM4 are laser optimized fibers, and they use VCSELs (Vertical Cavity Surface Emitting Laser) which are also a laser source.
Color Identification
Color is helpful in determining what type of fiber cabling you have, but it also can help when looking at adaptors. Not only does the color helps you identify if it is single mode or multimode, it also helps you distinguish the type of polish on the connector or coupler endface. Mainly, this applies to single mode connectors.
Multimode fiber has several different size cores and it also has different bandwidth capacities for the 50um core fibers. For 62.5um fiber the color associated with this is beige, therefore beige adaptors are typically used for 62.5. Dealing with 50um fiber is when you have to pay attention to all details.
There are four different types of 50um fiber OM2, OM3, OM4 and OM5. Let’s start with OM2 as this one can be difficult to comprehend since it has the same orange color jacket as 62.5 fibers. The color that is typically used for OM2 is black for adaptors but beige is also used as well. That’s why it is safest to always look at the printed markings on the fiber optic cable jacket to know which fiber optic cabling you have. OM3 and OM4 can also get confusing as they both use aqua and so you will have to read the jacket as well to be sure. OM4 however does have another color that is being used – magenta. Magenta is not the industry standard color, but it can help you distinguish which type of fiber optic cable is in place.
For single mode it is a little easier as there are only two color adaptors that are typically used. There is blue which lets you know you have a single mode connector but it also lets you know that it is a UPC (Ultra Physical Contact) polished connector or slightly rounded on the edges. There are also the color green adaptors, which indicate it is an APC (Angled Physical Contact) polished connector. On the APC polish, this connector has an 8 degree angle that helps lower the amount of back reflection the connector has. Applications such as FTTx use these optical fiber connectors that require very low back reflection to achieve signals over long distances.
Fiber Connector Styles
Just like optical connectors have different styles, adaptors have several different style types as well. Such as the number of connectors the adaptor can accommodate. Starting with simplex adaptors; which means that it will mate one fiber to another fiber. There are duplex adaptors; which allows you to mate a pair of fibers to another pair. This is vital as many systems use one fiber for transmitting and one fiber for receiving signals. Also with smaller connectors such as the LC fiber connector, there are also quad adaptors which help save space, so more connectors fit into a smaller space. These are also known as high density applications – where the object is to try to pack as many connectors as possible into the smallest area.
There are flanged adaptors. This means that they have little tabs on each side that allow you to screw the adaptor down so it doesn’t move. On the other side there are adaptors that are called no flange. They really do have a flange, but it is smaller than a regular flanged adaptor and does not allow you to put any screws in.
Another style of adaptor is shutter adaptors. Shutter adaptors help to prevent dust from getting in and causing havoc on your optical connectors. There are adaptors that have external shutters and there are some out there that have internal shutters.
Another solution that can be used rather than shutters are dust caps. These caps cover unused ports, and they also play a couple vital roles for your fibers. Not only are they helping to prevent material and other objects that could damage your fiber connector endface from getting inside the mating sleeve, but they also help provide safety for the technicians. When working with single mode fiber you are using light sources that are lasers, these lasers are powerful and if you look directly into them, they can cause damage to your eyes. Moral of story is – Better to be Safe than Sorry.
Hybrid Adaptors
Along with the traditional adaptors that mate two of the same style connectors together, there are also hybrid adaptors. These can be a couple different varieties that can include female to female and male to female. Typically hybrid adaptors help to mate two different style connectors together. For example, you have a piece of equipment that has a patch cord with a male SC connector on it. The switch that you need to plug into has a female LC port. In this instance, you would get a SC female to a LC male adaptor so you can connect the patch cord with the switch port.

What is the Best Way to Clean Fiber Optic Connectors?

Sometimes it is the simplest of things that cause the biggest problems.
Car won’t start? Check to see if you have gas in the tank. Is your fiber optic network having issues? Do you have performance problems with your fiber optical cable? Check your fiber optic connectors. It can be as simple as dirty connectors. A simple fiber optic connector cleaning can remedy the problem. And no, you do not clean them on your shirt. That doesn’t work. Do they look clean? How can you tell if there is contamination when the fiber optic cable is smaller than a human hair? You can’t.
What are the Differences between a Hand Held Microscope and a Video Microscope?
A digital microscope is just a regular hand held microscope with a camera added to it. Usual magnification ranges from 100x to 800x, a popular magnification is 400x, although 200x can usually do the job. Sometimes a 200x may be a better choice as you can see more of the area that is being inspected. These microscopes can capture images and have documentation software. They provide a report on the inspection. A tech can look at the connector on a computer screen. Some digital microscopes may have a focus, some models have auto focus. All you need do to use this microscope is attach the connector to be inspected and view the results on a computer screen or tablet. This image can also be captured and sent remotely to another location for inspection. A hand held microscope provides basically the same function as the digital microscope but is limited to just the inspection. It cannot be viewed on a computer or tablet screen nor can it transmit the image for remote viewing. However, it will give you the basic information you need on whether or not the connector is dirty.
How Do I Clean a Connector?
Step #1
It is always best to turn off the laser. Never under any circumstances should you look into the end of any optical fiber while it is energized. Looking directly at the fiber can cause irrevocable eye damage.
Step # 2
Remove the protective cap and store it in a clean container. Make sure the container has a cover. This will protect the dust caps from dust or dirt.
Step # 3
The connector now needs a visual inspection with a microscope. Typical dust and debris cannot be seen with the naked eye. A hand held microscope or a video microscope will aid you in seeing the condition of the connector. Take the connector and attach it to either the video microscope or the hand held microscope of your choice. Take a look to see the condition. If you see debris or contamination you need to do some cleaning.
Step # 4
You need to be careful when cleaning or you may introduce more contamination. There are several ways to clean a connector. Wet Cleaning, Wet to Dry Cleaning, and Dry Connector Cleaners.
• Wet Cleaning
• Dry Connector Cleaners
• Wet to Dry Cleaning
Wet Cleaning
You must use reagent-grade 99% isopropyl alcohol and lint free cleaning wipes. The reagent grade alcohol can be purchased in bulk however, it is suggested that you use pre-moistened Isopropyl alcohol wipes as bulk isopropyl alcohol can become contaminated after time and will absorb water from the air. The individually packed wipes will avoid that problem. Dry Connector Cleaners – Also known as click type cleaner or a cassette cleaner are generally used for light contamination. They contain a lint free type of tape designed to clean. It is more difficult to eliminate contaminants using the dry method. Connectors can become electrically charged during this method and may even attract additional contaminants. Use the correct materials to avoid this. Wet to Dry Cleaning – In this process you need to use a small amount of reagent grade alcohol to remove debris and dust particles. Apply a small amount to a lint free fiber optic cleaning cloth. Wipe the connector from the wet area on the cleaning cloth, towards the dry section of the cloth. Do this using a straight across forward motion right across the connector. Never use a figure 8 motion when using this method. This method of moving straight across the lint free surface will remove debris and particles. It is important to note more is not better when using this method. Using too much cleaner could contaminate the surface to be cleaned. Remember, moderate wetness, wipe only straight across from wet to dry.
Always Avoid
• A cleaning process that will leave a residue on the connector or end-face.
• Twisting or pulling on the fiber cable forcefully.
• Looking directly at lasers.
• Touching the area that was cleaned
• Reusing cleaning wipes
• Touching cleaning materials
Conclusion
You always need to inspect your connectors for contamination. Never assume a connector is clean. Connectors in many cases are the source of degradation. Contamination is your systems enemy. Use a microscope to do your inspection. Use a proven procedure and products to clean your connectors. Never trust the quality of your optical signal to guesswork. The only way that you can guarantee that your connectors are doing their job correctly is to; Inspect, clean, inspect.

Fiber Optic Microscope versus Fiber Optic Video Inspection Probe

Microscopes
If you are new to fiber optics, when you hear the word microscope, you most likely think of the one that was used in science class to look at cells of animals. Well in the fiber optic world, microscopes are a vital tool that should be in all technicians’ tool bags.
An optical microscope is a hand held tool used to look at the end face of a fiber optic connector. What do you look at the end of a connector for you ask? Looking at the end of a connector is vital to making sure that there is nothing wrong with the connector. By looking at the end of a connector you can see if there is any contamination such as dirt or oils, a scratch or even a broken (shattered) ferrule on the connector. Although you look at the whole end face, the primary spot that is looked at is the core of the fiber. The core of the fiber is the vital part, because this is where the light, or your data, will travel. When you are trouble shooting a fiber, visual inspection of the end face of the connector(s) is one of the first steps that should be done – before you pull out your test equipment to shoot with a power meter and light source, or even an optical time domain reflectometer (OTDR).
The very first microscopes that came out were pretty much glorified magnifying glasses. These were the 100X magnification microscopes. They were primarily helpful with multimode fiber connectors due to the core size of multimode fiber being much larger than single mode fiber. The next one to come out was the 200X microscope. These higher powered scopes were needed to better look at the end face and also to view the core of single mode connectors because the size of the core is only 9 microns. They were also used to look at the ends of the multimode connectors more in depth. There are scopes that only use coaxial illumination and ones that illuminate two ways, these being oblique or coaxial illumination. What came out next was the 400x power scope. The 400x scope is the single mode version of what the 200x scope was for multimode. The higher power scope allows you to view the end of a single mode connector in a higher detailed view, which allows you to more closely look at the vital central core of the fiber.
Video Scopes
After microscopes came video scopes. These come in the form of either a hand held probe or bench top scope, and they transfer the image onto some type of monitor. Bench top scopes are typically used in factory (cable assembly houses) or lab (research and development) type settings. A bench top inspection scope is a microscope that is positioned at a work area and that connects to a monitor. It will look at the connector and the image is transported over a connecting wire on to a bigger screen so it is easier to view. There will be better resolution and this makes it easier to focus and see the ferrule end face. These are not easily carried into the field, allowing for a different product known as video inspection probes. These are hand held devices that follow the same concept as the bench top scope, but they are smaller and portable, making them perfect for field use. The video inspection probes can work with several different monitors which makes them flexible for a variety of applications. Some probes come with a small hand held monitor that connects to the probe and allows you to see the end faces. Probes can also be hooked up to different OTDR’s, so while testing your fiber you can also look at the end face of connectors.
Analysis Software
One thing that has always been a problem with microscopes and even video inspection probes when they were first introduced is the fact that you have multiple view points on what is passing and what is failing. This would leave a lot up to human judgment and we all know that one person’s idea of passing may be completely different from another’s. Introduce analysis software that is programmed with industry accepted standards and rules that can look at the end face of the connector and tell you whether or not a connector is passing, or good. Then there is failing which means that the connector may still work but based on the standards it will not be allowed to be used in its current state. This software has a whole system of algorithms built in to it to allow the end face of the connector to be compared to the industry standard or expected parameters in order for a connector to be considered good or bad.
We had a customer that we would make patch cords for and we would test them and send them out to them with everything passing to the standards of testing that are accepted by the industry. The customer would get them in and perform incoming checks on all the patch cords to make sure they were up to their standard. Well after they checked them all, they called us and said that they had rejected 60% of the shipment and needed to send them back. This was a very high amount and we took action and scheduled a visit with the customer. Come to find out, the customer was not using any analysis software so their decision to reject the patch cables was all based on human judgment. We informed them that we use the software that takes the human judgment out of it and instead uses the complex algorithms in the software to help with the decision to pass or fail a connector. Once they learned this, the customer invested in the software and after that we had a zero rejection rate from that customer. By visiting with the customer to evaluate their process and get on the same page for testing purposes, it made it so that the standards being used were the same.
This software has gotten even better throughout the cycle to improve the process of scoping. Scopes now have features that make it easy for a tech to auto focus and auto center the fiber on the monitor or viewing screen. This improves the process of scoping because instead of having to spend time trying to focus and get the end face lined up in the middle of the screen so you can have the software do the pass fail analysis, it now will do this for you and you will know if your connector will pass or fail in a matter of seconds.
Another improvement that has been made takes advantage of the ability of Wi-Fi. There is now a wireless probe that communicates without a cord to get in the way. So now, as long as you are in a location that has a strong Wi-Fi signal, you can use the wireless probe and it will sync to either a tablet or your cell phone or even your OTDR so you can view your connector end faces.

What Are Some of the Different Fiber Optic Cable Jacket Ratings

There are several parts that make up a fiber optic cable; starting with the core, to the cladding, followed by the coating, the strength member and lastly the outer jacket. The outer jacket is the cover that gives protection and shielding, especially to the optical fibers. Whether it is meant to be indoor/outdoor, UV rated or armored, the jacket is what keeps the fiber protected and useful. Above all of these, the outer jacket is the first layer of protection to the fiber so it can withstand different conditions such as fire, moisture, chemicals, and stress during installations and maneuvering.

The National Electrical Code (NEC) has a classification system for optical fiber cables. The system specifies the requirements regarding how the fiber cables will endure under fire conditions. These requirements concentrate on how these cables can add a dangerous amount of fuel and smoke and transmit fire from one place to another.

Plenum

OFNP – Optical Fiber Non-conductive Plenum – refers to the specific fire code rating of cable that is flame resistant and emits the least toxic fumes or smoke when burned. Plenum rated cables have a higher fire rating and are for both commercial and residential use. They are considered the safest rated cable among jacket types. These cables are primarily used in ducts or pathways for heated and cooled return airflows. These spaces are usually above a ceiling or below a floor that serves as heated or cooled inhabited areas.

Plenum cables are purposely built with a jacket that gives off low amounts of smoke and that is flame retardant. Being able to deter the spread of flames and toxic fumes are the main uses for this jacket rating. The word plenum refers to the space in which air is circulated by a HVAC system. Drop ceilings and raised floors are perfect for the application. Plenum cables still use PVC (Polyvinyl Chloride) in the construction of the plenum jacket but special additives are put into the jacket material in order to make it more flame retardant. The NEC defines plenum cables by the airspace they are put into. Plenum rated cables are often used in building construction, typically they are used as communication cables for the building’s computer and telephone networks. Use of plenum areas for cable does pose some hazard in the event of a fire. This is because there are fewer barriers to contain smoke and flames.

Riser

OFNR – Optical Fiber Non-conductive Riser – is constructed of PVC and will emit toxic fumes when burned. Riser cables are to be run only in non-plenum areas. Plenum can usually replace riser but riser cannot replace plenum. Riser rated cables are typically used in the riser areas of buildings and in vertical telecommunications infrastructures. They connect from one floor to another and are used within shafts in accordance with section 800.53(B) of the NEC (National Electrical Code). They typically have load bearing strength members since they need to be upright without placing added stress on the fiber.

OFNR cable is resistant to oxidation and degradation but still gives off heavy black smoke and toxic gases when it is burned. Yet it is perfectly fine to use as a patch cord or for single in-wall runs. If you want to use it in a building, the building must feature a contained ventilation system and have good fire exits. Location is extremely important for these types of cables.

LSZH – Low Smoke Zero Halogen

These types of cables are made with halogen free materials and although they still emit smoke it is a much safer alternative. This type of cable jacket has superior safety characteristics. This rating offers low smoke, low toxicity and low corrosion standards. Tunnels, enclosed rooms, aircraft, and other minimum-ventilation areas are prime spots for the use of LSZH cables because areas like these are more difficult to escape from quickly. There are many different types of LSZH jacketed fiber optic cables provided for many different uses. The primary use for these types of cables is to satisfy the need for safety and environmental protection. Hospitals, schools and airports are good examples of where these cables should be installed. Due to the amount of people and the serious need for the protection of those people and equipment from toxic matter and gases should a fire ever occur. These cables are especially popular outside the United States, specifically for plenum spaces. Although it may seem as if you can replace plenum with LSZH cables, that’s not really the case. The difference is that while there is a lower smoke rating for LSZH, plenum cables have higher fire spread rating.

Cable tray rated

Tray cables are designed for just that, installation in cable trays. Primarily they are used in industrial control systems, factories, wind turbines and other severe environments. They can be rated for use indoors, outdoors, and in corrosive areas, for hazardous locations or high electrical noise areas. This cable was first introduced in order to combat failures in power and communication applications. There are several different kinds of cables to choose from, these include: Tray Cable (TC), Power Limited Tray Cable (PLTC), Instrumentation Tray Cable (ITC), Exposed Run (ER), and Wind Turbine Tray Cable (WTTC). Effective in direct sunlight as well as underground, these types of cables are extremely versatile in their application. Although cable in tray is viewed as being exposed to a greater risk of mechanical damage and it can be a potential ignition source or fuel load in a fire scenario. Due to this the NEC has a specific requirement in order to ensure the safety and quality of these fiber runs.

When choosing a jacket rating it is important to understand the placement and application where the cables will be run. It is pivotal that the cables meet local code requirements for the installations as well. These ratings are designed to prevent hazards and reduce risks to human and environmental health. We put on a jacket to prevent uncertainties from happening to our body, such as a cold or the flu. Fiber optic cable jacketing is very similar in the sense that we apply a certain compound to prevent a dangerous mishap, or if it does happen in the environment of the application.

Winter is coming… be sure to put on the appropriate jacket! .

Why should I calibrate fiber optic test and splicing equipment?

Would you drive a car with a speedometer that gives you faulty readings? How can you tell how fast you were driving? Optical testing equipment that is out of calibration will also cause faulty test readings. A fusion splicer that is out of calibration will produce inferior splices. False readings from an OTDR and a poor connector splice joining cable will cost you time and money. Not to mention customers and network owners who would question your fiber optic installation work. How do you expect to evaluate your installation or repair with equipment that has not been calibrated?

As demand keeps growing, more and more of today’s fiber optic network owners are demanding that their networks handle the increased speed needed to keep up with those demands. This means that your splice equipment and cleaver need to be up to the job. With this increased need for speed, today’s loss budgets are lower than ever. These budgets need to be met. Test equipment must be more accurate than ever.

Items that need to be calibrated

You need to remember your OTDR is an important piece of diagnostic equipment. It must be calibrated at specific intervals to ensure correct diagnostics. A power meter & light source is another important piece of testing equipment in your arsenal. This tool consists of transmitter and receiver. It measures the power of an optical signal that is passed through the fiber cable. When two ends of optical fiber are permanently welded together by an electrical arc, this is known as a fusion splice. Arc calibration is a must for the proper splice to take place. Do not forget the optical fiber cleaver. Cleaving is the process of breaking or cutting of the fiber. A fusion splice requires the use of a highly accurate cleaver. As you can see the each piece of equipment mentioned has a specific job. Not calibrating a cleaver or a fusion splicer can mean a poor splice. Without calibration, optic test equipment such as the OTDR and power meter & light source are somewhat useless in determining things like the quality of connectors and splices.

What is a loss budget?

This calculation is the total optical power loss that the system is allowed to have. This amount is determined by the power losses resulting from the total amount of equipment that the system has. A loss budget for fiber optic networks is derived from installation of items such as patch cords; couplers, adaptors, splices, cable and any additional optical components installed in the system. This is determined when the network is designed. After it is installed this loss must be tested to see if the budget has been met. Is the splice that has been made to extend the cable acceptable? How about a connector? Was it installed properly? Another equally important reason for OTDR testing, is once the system is active, later on if a problem presents itself, you can go back to the original test. You could then compare the new test to the original test and determine the problem quickly and easily. This is why accurate OTDR testing equipment must be maintained. In order for that piece of equipment to be accurate it must be calibrated on a regular basis.

Calibration is not an option. It is a must.

Put calibration off and it could cost you more than the cost of the calibration itself. Incorrect readings could have technicians thinking the installation is better than it really is or just the opposite. Your company name depends on quality and accuracy. It is not worth saving a few bucks on calibration. During the year your equipment such as splicing equipment is subjected to all sorts of events that can cause it to go out of calibration. If you are in the south heat can be your enemy. Up north freezing temperatures are not your friend. Have you left your equipment in your truck only to be bounced around? All those bumps, drops and bangs add up to inaccurate readings. Dirty conditions are no help either. In many instances in order to get paid you need up to date certified testing equipment. If you are certified for ISO 9001 you need your equipment calibrated. ISO clause 7/6 reads in part as; Control of monitoring and measuring equipment. The organization shall determine the monitoring and measurement to be undertaken and the monitoring and measuring equipment needed to provide evidence of conformity of product to determined requirements. The organization shall establish processes to ensure that monitoring and measurement can be carried out and are carried out in a manner that is consistent with the monitoring and measurement requirements. Remember, calibration is always a must when the measurements from your equipment are critical – It’s that simple.

What exactly is calibration?

When you calibrate any piece of equipment the unit to be calibrated is compared to a unit of a known value. This known value comes from another similar device of known accuracy and precision. Equipment that has a laser which is being calibrated means that laser must fall within a specific acceptable range. Should the equipment being tested be found to be “out of calibration” and produces faulty readings, the equipment must be repaired or adjusted so it falls within the acceptable specified range of measurement.

What is NIST Calibration?

NIST stands for National Institute of Standards and Technology. They provide services to make sure the equipment being calibrated is measured up to a particular piece of equipment similar to that of the equipment being calibrated. NIST certifies that that the lab testing to equipment uses a method that meets the standards of the NIST and must match the NIST measurement standard for a particular piece of equipment. For fiber optic purposes, that would be equipment such as an OTDR, a fusion splicer, cleavers, power meters and lights sources.

In simple terms when using the NIST method you need an unbroken chain of documents; your piece of equipment and components are compared to our piece of equipment which in turn was compared to a piece of equipment from the NIST which is within a stated tolerance. NIST sets the tolerance and it is correct. Our equipment was compared to the NIST equipment so we know ours is correct. Finally yours is compared to ours and found to be correct. That is an unbroken chain. This unbroken chain which is traced back to NIST standards for accurate measurement is how uniformity is maintained. Once your equipment has been tested and meets NIST standards you will receive a calibration certificate paper work stating the results and the date. This means your equipment has met the highest test standards. A big plus would be getting that certification from an ISO compliant calibration company.

What is ISO?

The International Organization for Standardization (ISO) is the world’s largest non-governmental organization developer of standards. ISO 9001 is the most sought-after and internationally acclaimed management system standard. They have created over 22,808 International standards and goals. Their standards are voluntary. Companies who seek out this standard are ensuring that their customer requirements are met accurately and consistently. When it comes to calibration a company is working to meet a set of regulatory requirements which in turn will improve company performance, which will improve product and service quality. This method in the end will benefit the customer by assuring them that the ISO certified company has met the exacting ISO standards to bring them a better product.

Conclusion

Over time even a well cared for piece of test equipment can lose its’ accuracy. You must have your equipment calibrated as suggested by the manufacturer. However, in many instances you may need to get it done sooner, as many conditions that the equipment is subjected to may alter or falsify your test results. As networks need to increase their efficiencies loss budgets are becoming smaller and smaller. Only calibrated equipment can assure you are correctly within that budget. Calibration is not really an option. It is a must. Always use a lab that will test to NIST standards and if possible use an ISO certified test lab. Accurate results will always save you time, money and your company reputation.

Types of Fiber Optic Attenuators

Fiber Optic Attenuators

When looking at fiber optic attenuators, people always have several questions as to why would you purposely put attenuation on a fiber optic network. When testing fiber, attenuation is one of the key points that you are looking for. You want your attenuation to be as low as possible, so that you can fit the link budget that you are trying to meet or beat. For those that don’t know, attenuation is the amount of light or signal lost over a span or link. When building a network, customers are always looking to cover distances as far as possible and sometimes they add a fiber amplifier to boost signals to make sure that they reach to the end of where they are running fiber so that a signal will reach every customer or place that it needs to. Sometimes adding in an amplifier causes a higher power laser to be used, which in turn, if the signal is only going a short distance to your first location, can cause the light signal to be too strong when it hits the optical receiver. It can either distort the signal or it can burn up the optical receiver. This is where an attenuator that purposely adds in loss is useful and necessary. Attenuators come in several different types, and have many different levels of attenuation to assist in creating the perfect balance for a network. Let’s dig into the different types of fiber optic attenuators to give you a better idea of the different ways you can help to create loss and potentially save you money in equipment costs.

Male to Female Optical Attenuator

The common optical attenuator that I usually sell the most of is the male to female style attenuators. These attenuators are used at the end of a patch cord and typically get plugged in at the receiving side of your transmission. Some refer to these as in-line attenuators, because they are put directly into a switch and a patch cable is plugged in. These come in 1 db increments and go from 1dB to 25dB in attenuation levels. They come in the four most common fiber connector types in both UPC and APC polishes. Often the level of attenuation that is perfect for the application is unknown. Most customers will buy a hand full of each dB level from 1 to 10. When on a job the amount of attenuation needed varies so they have a variety and it becomes a “try it till it works” process. Meaning, if they start with 5dB and it is too much and shuts the signal off, you would know that you need less attenuation and your next level to try would be 4dB. Repeat the process until the desired attenuation is achieved.

Female to Female Optical Attenuator

There are attenuators that allow you to plug two male connectors to each other. These are the bulkhead style female to female attenuators. They tend to be wavelength specific. This means for the desired attenuation it is only guaranteed at the specified wavelengths – 1310nm or 1550nm. This style uses a wavelength sensitive neutral density filter that assists with achieving the proper level of attenuation. When using this type, they only come in four different dB levels. In increments of 5 – so 5, 10, 15 or 20dB is what you can get these in. Use this style when you know exactly the dB level of attenuation needed and what wavelength you need the attenuation to be on.

Variable Optical Attenuator

Rather than getting several different dB levels of attenuators, there are some other types of attenuators that allow you to change the amount of loss. One of these styles is called a variable optical attenuator. It uses a device in the middle of a patch cord that allows you to turn a screw to change the amount of attenuation. It ranges from the 1dB to 20 dB and works on both 1310nm and 1550nm wavelengths. This one will have a specific connector on each end. By turning a nut on the device it helps separate the connectors or helps to pull them back together. This will change the amount of loss in a system because connectors are meant to have the end faces touching to eliminate that loss.

Another type that we have is an air gap attenuator. These are only available for the ST and FC style connectors. This one uses its name and puts different levels of space (air) between a mated pair of fiber optic connectors. Air attenuators involve the use of “washers” to cause attenuation by creating distance between the end faces. The washers have different thicknesses to help change the amount of loss. This kind of washer style attenuator does not have specific dB levels as there are other factors that can affect the amount of loss at that point. They do however have different colors to help you to know which one you have tried through your test process. Unlike the male to female attenuators, the washers are placed at the light source or transmitter and not the receiving side.

Passive Optical Attenuators

Another form of attenuator is known as passive style attenuators. This is where you use a device to help attenuate a patch cord that is already in place. We have two different options that we would consider this type. One is a Clip On attenuator that can be used on a 3 millimeter jacketed fiber and has the ability to go from zero dB to 47dB for the wavelength of 1550nm. For a wavelength of 1310nm the levels will be zero to 21 dB. When the Clip On attenuator is put on a fiber, the way it works is by bending the fiber to cause the desired loss that is required. This device can be reused and does not affect the performance of the fiber once removed. The other one that would fall in this category would be the 3 step attenuator. This one only works on wavelength of 1310nm. There are three different ranges, 2-7dB, 5-15dB and 5-20dB. This device works by exceeding the recommended bend radius of the fiber without introducing any back reflection.

As you can see, attenuators can have a very important role in certain networks. They may sound counterproductive in the sense that when running fiber you are looking for the smallest amount of loss. Attenuators not only create loss but can assist in a network that has too much light going through which can affect the signal and cause data loss on a link. It is funny to think that a part that costs around 12 dollars can have a big impact on a network that cost a lot more to put together.