Category: Fiber Transceivers

Optical transceivers, Active Optic Cables, data center switches, and cable management in data centers.

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.

Different Types of Cable Jacketing

In the fiber industry, we have all probably seen the words plenum or riser in our day, as these are two of the most common jacket types in the United States. In Europe we are seeing more Low Smoke Zero Halogen cables being utilized. But there are other options out there in the fiber optic world that are lesser known and talked about, they are the likes of Low Smoke Zero Halogen (LSZH), and Polyethylene (PE).
When looking at the construction of any fiber optic cable, you will notice that the jacket is the first line of defense against physical damage from chemicals, water, burning and other potentially damaging effects that would compromise the viability of the cable. Cable jackets come in multiple colors, but there are industry standard color codes such as aqua for OM3 or yellow for single mode, but in some cases there are custom colored jackets. You will also see foot markers on the outer jacket, showing you length of the cable, and even a print string showing the type of fiber, brand of cable, and type of cable construction. The print string will also contain information as to whether or not the cable is UL listed, and if it is, it will contain the UL number. Most cable jacket material is made from PVC or Polyvinyl Chloride, and there are additives that determine its jacket rating.
Plenum and riser ratings are defined by the National Electrical Code (NEC). They are also responsible for the standards that these cables must abide by in order to be classified as plenum or riser cabling. This standard basically states that if a fire were to start within a structure, how much would these compounds contribute to the fire, and create a “fuel” source – transporting the fire from place to place along the cable.
Most fiber optic cables that adhere to these fire standards are Underwriter Laboratories (UL) tested, meaning that they bear the UL marker on the cable jacket and have been certified to meet the NEC Standard for the cable jacket type. These UL Listings are independently tested, and qualified to ensure that the safety measures are upheld. They (UL) have no monetary stake in the items that they test, and consumers can be assured that this UL listing means that the safety standards are upheld. These listings are given and can be taken away at any point if the quality of the product does not continue to meet that UL standard.
The real question that most technicians ask in the field is where to use what type of jacket. Below we will go into a breakdown of the cable jacket types and where they can be utilized within a building or structure.
Plenum Cable
Plenum has the highest fire rating, meaning that it can be installed in all of the plenum spaces within a building such as the air ducts and ventilation systems – any part of the building that has to do with heating or cooling. Plenum can sometimes be utilized in any space within a building as an alternative to other jacket types. Plenum cables are less hazardous and create less smoke and toxic fumes in the case of fire. If a job requires plenum cable then plenum cable must be installed, there are no alternatives for this type of cable install. Plenum cables for the above reasons are usually slightly more expensive than the other cable jackets.
Riser Cable
Riser cabling is only to be used within riser spaces in a building – such as between building shafts, for vertical runs. It is meant to be a backbone cable, the fire ratings that fit a riser rating are not as strict as plenum. You can utilize a plenum cable within a riser space, but you cannot utilize a riser cable in a plenum space. Such as in the case of a ventilation shaft – you could not install a riser cable because this is a plenum air space, but you can install riser say in an elevator shaft between the floors of a building. Typically, riser cables are less expensive than plenum because the standards are less stringent.
Low Smoke Zero Halogen (LSZH) Cable
Low Smoke Zero Halogen cable jacketing or LSZH is a separate classification from riser or plenum cables because it does not contain the same compounds or thermoplastics that produce smoke and other hazardous chemicals that could be harmful to humans and animals that may be in the vicinity of the cable, if it ever should burn. To be considered low smoke zero halogen cable, it must be made of flame retardant materials that do not excrete halogens, and produces little to no smoke when it burns. LSZH is not the same as a plenum cable – they are two different fire ratings. While it may seem beneficial to use LSZH within every space in a building, this type of cable does not fit the bill for every single application. Since this product is far more expensive than other compounds, it does not make sense to install this in areas that do not require a less hazardous, or low smoke material. LSZH is highly recommended for areas that have poor ventilation, where people tend to congregate or in a confined space. LSZH is primarily utilized in Europe currently but, this type of cable is gaining traction within the US markets. .
PE Cable
PE (polyethylene) rated cable is primarily used for outdoor cables only; this is not a cable that can be installed more than fifty feet inside of a building. PE cable jacket’s superior weather, temperature and water or moisture resistance makes this a great pick for harsh weather conditions and installations, but its rigid characteristics make it difficult to utilize in environments that require flexibility or movement of the cable. It also boasts superior UV protection because its black color absorbs the sunlight, which is a typical characteristic for outdoor rated cabling.
While there are more cable ratings and classifications than these shown above, these are the most common types that your average technician will run into on the job more. Familiarity with the cable jacket types is never a bad thing to have in a technician’s pocket. Knowing and being able to define what makes a plenum cable plenum or riser cable riser is superior knowledge that will benefit the technician on future jobs. .

How Do I Choose the Right Fiber Interconnect Box?

Decisions, Decisions
When talking about interconnect boxes (also known as enclosures), there are a variety of options that can be used. Often, a common question asked by customers is which box would be best for their application. This is a loaded question that requires some questions and answers to see what will work best for the situation that they have in front of them. There are a number of factors that will have to be addressed to come to a point where we can help to make a recommendation. Where is the interconnect going to be located, along with how many fibers are you going to be putting in the enclosure and if it will need to house fusion splices. Is there a 2 post rack existing or will you have to put that in as well?  Does your job have a spec that you need to follow? Specs are written by engineers and sometimes they call out specific manufacturers that can be used for a job. Other specs are open to different manufacturers as long as it covers what is needed for the job or project.
Wall vs. Rack Mount
When talking about interconnects we will discuss the two types that are primarily used in building your network. Not to say there are not other options, we will just be talking about the most common two used. The first one we will discuss is rack mount enclosures. These come is several different sizes and configurations. You can have anywhere from a 1RU (Rack Unit) all the way an 8RU. This is the amount of space that the rack mount will take up in your 2 post rack. So if you have 72 fibers to install and you are using SC 6 pack adapter plates then you would need a 4RU rack that accepts 12 plates. If you were to use duplex SC adapter plates you could use a 2RU rack with 6 adapter plates. Again, this will also depend on what you are looking to do along with if you are splicing in the back. If splicing you want to make sure you have enough room for your fiber management along with splice trays.
Now with wall mounts you have the same idea as rack mounts except now you will need to know how much room you have where it is being installed. So dimensions of the wall mount are important along with how many adapter plates it holds. You will still need to know if you are splicing in it. Fiber count is important, as well as what style connectors you will be using to determine how many adapter plates you will need. Some installers look at cosmetics for both the wall and rack mounts. Interconnects are offered in black and off white and they will be off the shelf items. We do also have the capability of customizing these to different colors as well. When you are customizing there are quantity requirements that need to be met. This not only applies to the enclosures but adapter plates as well. If you have a good size project and would like to customize it all to match it can be done.
Fiber Count
When talking enclosures one of the first questions that is asked has to do with how many fibers will you, the customer, be putting into these enclosures. This is a vital part of figuring out what you will need. When designing a system you will typically have a central point that will hold all fibers in one location. This has to have a little bigger rack or wall mount due to having a larger number of fibers. Then what happens is there are several runs of fiber that go out to several different locations that need to be connected. At these locations there is a smaller box that will hold the number of fibers needed for that location. For example, at your central location you have a total of twelve different runs that go to twelve different locations. So at your central point you will need to have an enclosure that will hold a minimum of 144 fibers (12 fibers per run x12 different locations). So for each of your runs of fiber you will need a rack or wall mount enclosure, at the end of the run, that will hold 12 fibers.
Splice Trays
When picking out the correct enclosures, a big part of the decision is whether or not splicing will occur in the back of the wall or rack mount. If you are splicing, then this section will apply to your decision. If not, you can skim over this part like most of us do with nutritional facts on the back of food products. Splice trays, like the rack and wall mounts, have several different options that you can choose from. There is the number of splices to consider, which is typically 12 or 24 per tray. There are dimension differences as well that will play in to the decision of which one to choose. Splice trays are one of the last things to consider because you will need the dimensions of the enclosure to choose the correct size splice tray. If you are trying to splice a higher fiber count you will want to try to use the splice tray that can accept more splices per tray. This will help keep the number of splice trays needed down and to make the fiber management look as professional as a man dressed in a tuxedo ready for his wedding.
LGX Style vs. Proprietary
In all interconnect boxes you need adapter plates loaded with mating sleeves that allow you to connect your fibers together. Along with knowing which connector style you are connecting, you will also need to know what style box you are using, especially if you are connecting in a panel that already is in place. There are plates that are “universal” that will fit in multiple manufacturers’ enclosures. One style is known as LGX adapter plates. There are several manufacturers that use this concept allowing for multiple manufacturers’ adapter plates to be interchanged and used with several different manufacturers interconnect boxes. There are other manufacturers that have proprietary adapter plates, meaning you can only use that manufacturers adapter plates with their rack and wall mount enclosures.

Fiber Optic Patch Cable – (color coding)

Fiber optic patch cable, is also known as fiber optic jumper or fiber optic patch cord which is composed of a fiber optic cable terminated with different connectors on the ends.
Fiber optic patch cable is used to cross-connect installed cables and connect communications equipment to the cable plant.It is a very important component of the network.
In general, fiber optic patch cables are classified by fiber cable mode or cable structure, by connector construction and by construction of the connector’s inserted core cover.
Fiber Cable Mode & Structure
According to the fiber cable mode, fiber optic patch cables are divided into two common types – Singlemode fiber patch cable and Multimode fiber patch cable. Singlemode fiber patch cables use 9/125 micron bulk single mode fiber cable and single mode fiber optic connectors at both ends. Singlemode fiber patch cable is generally yellow with a blue connector and a longer transmission distance. Multimode fiber patch cables use 62.5/125 micron or 50/125 micron bulk multimode fiber cable and terminated with multimode fiber optic connectors at both ends. It is usually orange or grey, with a cream or black connector, and a shorter transmission distance. According to the fiber optic cable structure, fiber optic patch cables include simplex fiber optic patch cable and duplex fiber optic patch cable. The former has one fiber and one connector on each end while the latter has two fibers and two connectors on each end. Each fiber is marked “A” or “B” or different colored connector boots are used to mark polarity.
Connector Construction
Connector design standards include FC, SC, ST, LC, MTRJ, MPO, MU, SMA, FDDI, E2000, DIN4, and D4. Fiber optic patch cables are classified by the connectors on either end of themselves. Some of the most common patch cable configurations include FC-FC, FC-SC, FC-LC, FC-ST, ST-LC, SC-SC, and SC-ST.
Construction of the Connector’s Inserted Core Cover
Fiber optic connectors are designed and polished to different shapes to minimize back reflection. This is particularly important in single mode applications. Typical back reflection grades are -30dB, -40dB, -50dB and -60dB. The connector’s inserted core cover conforms to APC (Typical back reflection <-60dB), UPC (Typical back reflection <-50dB), or PC (Typical back reflection <-40dB) configuration.
The buffer or jacket on patchcords is often color-coded to indicate the type of fiber used. In addition, color-coding of connectors for different fiber standards make it easy to avoid confusion.
Fiber Color Codes
Similar to the color coding designations of copper cabling, optical fiber has a color code designation for strands of fiber within the larger cable, as well as the cable’s jacket. These color codes are set by the EIA/TIA-598 standards guide identification for fiber and fiber related units that determines which color codes are used in which applications. The colors don’t only apply for the application though, they also are meant to be of use in determining a cables properties. The differences in colors are based upon different levels of OM and OS fiber (Optical Multimode & Optical Singlemode).
Optical fiber cable is separated into strands, which are the individual fibers within the larger piece of cabling. Up to 24 individual strands can be manufactured loosely, and after that point they are usually sectioned into tubes containing 12 each. Each tube containing 12 strands is then given a color.
Connector Color Codes
Since the earliest days of fiber optics, orange, black or gray was multimode and yellow singlemode. However, the advent of metallic connectors like the FC and ST made connector color coding difficult, so colored strain relief boots were often used.

Deploying Tunable Transceivers: Advantages, Challenges and Solutions

Tunable transceivers represent a cutting-edge technology that allows on-site wavelength adjustment, transcending the fixed-wavelength limitation of traditional static transceivers. The need for tunable devices has become increasingly important as networking technology continues to develop. Dense wavelength division multiplexing (DWDM), which is expected to serve as the central technology in the future of optical networking, allows data of different wavelengths originating from different sources to share a single optical fiber.
One drawback of static transceivers is that multiple backups are needed to minimize network downtime in a DWDM environment, given the range of wavelengths present. This can greatly increase operating cost. While it’s true that individual tunable transceivers tend to cost between two to four times more than their static counterparts, they can both minimize cost and maximize flexibility when considered in the context of the system overall.
The flexibility afforded by tunable transceivers is also key to adapting to the needs of a growing network. This aspect will only become more important as transmission rates increase and flexible channel spacing becomes crucial to networking success.
That said, tunable transceiver technology can lead to challenges for operators attempting to interface with legacy equipment. One of the most significant challenges is an inability to tune over the command line interface (CLI); it’s a problem that presents itself for some switches and routers interfacing with tunable XFP transceivers, and is even more common among devices interfacing with tunable SFP+ transceivers.
Fortunately there is a solution: a transceiver management module, also known as a tuning box, which features ports designed for hosting tunable transceivers and that works in conjunction with tuning software.
Precision Optical Transceivers offers two major transceiver management modules – the TN100-XS and TN100-S-BT.
Precision’s TN100-XS tuning module is a USB-powered device capable of hosting both SFP+ and XFP devices. It allows for tuning to any of the standard ITU C-Band 50GHz or 100GHz spaced channels.
The TN100-S-BT is a Bluetooth® powered compact device capable of hosting SFP+ devices, allowing for on-the-go tuning through a proprietary mobile tuning application. The device also allows for tuning to any of the standard ITU C-Band 50GHz or 100GHz spaced channels.
Tuning software is included with both devices and offers the advantage of being web-driven, meaning that the device will stay up-to-date without the need for manual installations of new firmware, or the inherent security compromises that accompany manual network interaction.

Why Use Tunable DWDM SFP+ Transceivers?

The tunable DWDM SFP+ is one kind of DWDM SFP+ transceivers. They both can be used in the DWDM system. In the market, tunable DWDM SFP+ transceivers are often between two and four times more expensive than DWDM SFP+ transceivers. Thus, many may think DWDM SFP+ transceivers are enough in the DWDM system and wonder why tunable DWDM SFP+ transceivers are also needed. This post will introduce what is tunable DWDM SFP+ transceiver and explain why they need to be used in DWDM systems in details.
What’s Tunable DWDM SFP+ Transceiver?
DWDM SFP+ Transceiver
Tunable SFP+ transceivers are a new technology that is in development for a few more years due to the limiting power specifications of the SFP+. They are only available in DWDM form because the CWDM grid is too wide. So a tunable SFP+ transceiver is also called tunable DWDM SFP+ transceiver.
The tunable DWDM SFP+ transceiver is equipped with an integrated full C-Band 50GHz tunable transmitter and a high performance PIN receiver to meet the ITU-T (50GHz DWDM ITU-T Full C-band) requirements. It shares the same hot–pluggable SFP+ footprint as DWDM SFP+ transceiver. The major difference between them is that DWDM SFP+ has a fixed wavelength or lambda while the tunable DWDM SFP+ can adjust its wavelength on site to the required lambda. Tunable DWDM SFP+ transceivers enable us to change wavelengths unlimited within the C-band DWDM ITU Grid and can be applied in various types of equipment such as switches, routers and servers.
Why Tunable DWDM SFP+ Transceivers Are Used in DWDM Systems?
In traditional DWDM systems, fixed-wavelength DWDM SFP+ transceivers are commonly used as light sources in optical communication field. However, as the continuous development, application and promotion of optical communication systems, the disadvantages of DWDM SFP+ transceivers have been gradually revealed. The followings are why tunable DWDM SFP+ transceivers are also needed in DWDM systems:
On the one hand, it is essential to prepare backup DWDM SFP+ transceivers for each DWDM wavelength to avoid unnecessary breakdown. In traditional DWDM systems, a small number of extra DWDM SFP+ transceivers are enough. However, with the development of technology, the number of wavelengths in DWDM 50GHz now has reached the hundreds. This means people have to provide up to hundreds of backup DWDM SFP+ transceivers, which will greatly increase the operating cost. Tunable DWDM SFP+ transceivers provide equipment manufacturers and operators with great flexibility, achieving the optimization for the overall network performance and greatly reduce the demand of existing operators for DWDM SFP+ transceiver inventory.
10GBASE 1350nm~1610nm CWDM SFP+ 10km Transceiver
On the other hand, in DWDM systems, it may be required to use a large number of DWDM SFP+ transceivers with different wavelengths to support the dynamic wavelength assignment in optical network and improve network flexibility. But the usage rate of each transceiver is very low, resulting in a waste of resources. The arrival of tunable DWDM SFP+ transceivers has effectively solved this problem. With tunable DWDM SFP+ transceivers, different DWDM wavelengths can be configured and output in the same light source, and these wavelength values and intervals all meet the requirements of ITU-T (50GHz DWDM ITU-T Full C-Band).
Conclusion
Featuring for flexibly selecting working wavelength, tunable DWDM SFP+ transceivers have very large practical value in optical fiber communication wave division multiplexing system, optical add-drop multiplexer and optical cross-connection, optical switching equipment, light source parts and other applications.