How to choose your fiber optic Cable?
Introduction - What is an optical fiber ?
In this article, we will try to guide you on how to choose your fiber optic cables properly. However, we first need to understand what exactly is a fiber optic cable.
Definition
An optical fiber is a flexible, transparent fiber made by extruding glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer. [1]
Fiber Optic Cable Composition
- Core
Depending on the fiber, the core can be equal to 9µm (Single mode), 50µm (Multimode OM2/OM3/OM4/...) or 62.5µm (Multimode OM1).
- Cladding
Providing a lower refractive index at the core interface in order to cause reflection within the core so that light waves are transmitted through the fiber. The cladding usually has a diameter of 125µm
- Buffer
Offering the first layer of protection of the fiber (against bending and shock).
- Jacket
Offering the second layer of protection and allowing, based on its colors to specify which type of fiber it is (OMx, OSx).
Single Mode or Multimode?
Many decisions come into play when installing fiber optic cabling. By far, one of the most important questions is whether to install single mode or multimode. This decision has huge implications for your network’s distance, bandwidth, and budget, so it’s vital to understand the differences between these two types of fiber optic glass.
For many of you, new to fiber, multimode fiber may seem appealing because the name implies that more can be sent over the cable. However, “multimode” refers to multiple rays of light simultaneously taking different tracks down the core of the fiber. This characteristic, enabled by multimode’s larger core, actually creates some limitations. [2]
Indeed, in multimode fiber, light travels down the core, bouncing off the cladding as it goes. As each beam of light has an individual path, each will reach the end of the optical fiber at different times. This spread is called modal dispersion, and it creates limits on data as well as distance. As a matter of fact, the narrower the core, the bigger the bandwidth. This is because you will have less reflection,dispersion... and so received a narrowed impulse which will allow a higher bandwidth.
If you also want to improve your knowledge about the sources of attenuation in fiber optics, check out our guide dedicated to Fiber Transmission Loss.
For each mode, there are multiple types of fiber, which imply different characteristics. Below you will find a table that provides you with a resume of performance and how to distinguish the different constructions.
| Name | Diameter | Jacket Colors | Connector Colors | Optical Source | Bandwidth | Common speed used | Distance (for given speed) |
|---|---|---|---|---|---|---|---|
| OM1 | 62.5/125 | Orange | Beige | LED | 200MHz/km | 100 Megabit | 2km |
| OM2 | 50/125 | Orange | Black | LED | 500MHz/km | 1 Gigabit | 550m |
| OM3 | 50/125 | Aqua | Aqua | VCSEL | 2000MHz/km | 10 Gigabit | 300m |
| OM4 | 50/125 | Aqua or Violet | Aqua or Lime | VCSEL | 3500MHz/km | 40 Gigabit | 150m |
| OS1 | 9/125 | Yellow | Blue or Green | Laser | > 10GHz/km | 100 Gigabit | 40km |
Why Use Multimode?
Why bother with multimode if it provides less bandwidth for a shorter distance? The answer is simply related to the cost of single mode.
Today, the total cost of a single mode installation ranges between 1,5 to 5 times the cost of a multimode installation.
This might be a bit surprising as multimode fiber is a tinny bit more expensive.
Indeed, the main source of expense for single mode installation are the transceivers. For single mode you must use an expensive powerful laser. This laser must send a concentrated beam into the 9um core, with enough power to travel long distance and must be able to follow the targeted bandwidth.
Plus, Multimode transceivers consume less power, which can be significant when you have a huge data center, for which you must take into account the cost of power consume by the equipment as well as the cost to cool down your data center.
To sum up:
- SingleMode:
- Is a fiber composed by a 9µm core.
- Using 2 main wave lengths for communication: 1310nm and 1550nm.
- Is for longer distances.
- Allows for a higher bandwidth (almost unlimited).
- More expensive (due to the singlemode transceivers).
- More sensitive to contamination (due to the smaller core).
space
- Multimode:
- Is a fiber composed by a 50µm core
- Using 2 main wave lengths for communication: 850nm and 1300nm.
- Is for shorter distances.
- Has a smaller bandwith, related to the type of fiber (OMx).
- Is cost effective.
- More tolerant to dust.
space
- Multimode and Single Mode are not interchangeable!
Which Connection Type?
Physical Contact vs. Lens coupling
In fiber optic communication, you have 2 types of connectors: Physical Contact and Lens coupling.
Those 2 technologies offer pros and cons that must be weighed and chosen based on your needs.
Physical Contact
With physical contact, the connector's 2 ferrules are placed against each other, aligning the cores, enabling the wavelength to pass through both connectors.
There are multiple types of PC connectors: Flat, PC, UPC, APC.
- Where the FLAT connector are simply flat/perfectly vertical, leaving a small air gap between the 2 ferrules.
- Where the PC connector is similar to the Flat Fiber connector, but is polished with a slight spherical (cone) design to reduce the overall size of the end-face. Decreasing the air gap, resulting in lower Optical Return Loss (ORL).
- Where the UPC connector (Ultra PC) is a PC connector with an extended polishing method that creates an even finer fiber surface finish, decreasing again the ORL.
- Where the APC connector (Angle PC) is a PC connector with a small 8° angle, allowing an even tighter connections.
| Flat | -20 dB/1% |
| PC | -40 dB/0.01% |
| UPC | -50 dB/0.0001% |
| APC | -60 dB/0.0001% |
Pros & Cons:
Cheap
Low coupling loss (0.3-08 dB)
Works with all frequencies
Allows multiplexing
Easier for field repair
Dust sensitive
Needs to be cleaned after a few mating cycles
Protected Physical Contact
In order to find the best solution for its customers, Neutrik developed the OPTICALCON, a rugged physical contact fiber solution for outdoor events. Keeping the best of both worlds!
Lens Coupling
The lens technology magnifies the size of the core, allowing a much bigger transfer zone for the light. Therefor, making it much more resistant to dust and other contaminations.
Pros & Cons:
Outdoor used (way less sensitive to dust compare to PC)
High mating cycles
High coupling loss (1.5 dB)
More sensitive to back reflection
Limited to one precise band per connector (these lenses are tuned to a particular wavelength only)
Limited to multiplexing as 1 connector is made for 1 precise wavelength
Advanced Lens Technology
To remain state of the art, Neutrik works in collaboration with the latest technology. Allowing them to develop brand new cables with lens technology that tend to reach the physical contact performance but with the lens robustness.
Check out the XB2 technology developed in the DRAGONFLY, a camera dedicated cable.
Check out the HybridMed cable, a Hybrid + 16 fiber fiber cable especially made for the medical environment!
Fiber Design - Loose Tube or Tight Buffer?
The cable jacket includes the strengthening fibers which includes the coating which includes the cladding which include the core.
There is 2 types of fiber design:
- Loose Tube (better for harsh environment, long distance and for long pulls through conduits), tube's inner diameter bigger than cladding, can be filled with gel.
Isolates from mechanical forces (strength member) and continuous mechanical stresses
More stable against temperature and humidity changes
Lowest cable attenuation, more stable transmission characteristics
Delicate and expensive to terminate, needs splicing break out kits
Less flexible
- Tight Buffer (better for indoor environment, short distance), an extra layer of kevlar instead of gel is added in the fiber cable.
Don’t require a break-out kit for splicing or termination, connectors can be directly crimped to each fiber
Small and lightweight design, flexible cable
Easier to install (increased size for handling, no messy gel to clean up,...)
More expensive than loose tube
Lower stress isolation (temperature, mechanical stress)
Sharp bends or twists equals microbending loss
Slightly more attenuation than loose tube
Nevertheless, if you want to make sure that you can ben fiber as much as you want, making sure it can resist through everything, check out our Cleerline SSF fiber, the fiber of the future!
Belram's Solutions
Belram offers a large range of solution regarding fiber optics equipments. Feel free to check our website or contact us for further informations.
Fiber Patch Cords
Fiber Cleaning
Hybrid Lense Technology
Outdoor Rugged PC Fiber
Unbreakable Fiber
Fiber Accessories
Glossary
µm - micrometer
The µm is a unit that represent a length, equalling to 1×10−6 meter, so one millionth of a meter or 0.001 mm
Laser
A Laser is a perfect, powerful with a narrow emission pattern but expensive optical source.
LED
A LED optical source has a large emmision pattern with a weak signal but extremly cheap component.
Multiplexing
Multiplexing allows you to send multiple signals simultaneously on the same fiber at the same time. There are 2 types of multiplexing: Coarse Wave Division Multiplexing (CWDM) which combines up to 16 wavelengths onto a single fiber and Dense Wave Division Multiplexing (DWDM) which combines up to 64 wavelengths onto a single fiber.
Optical Return Loss
The ORL represents the total accumulated light reflected back to the source along the link due to: connectors back reflection, diffusion, Rayleigh back scattering,...
The ORL = 10Log(Pt/Pr) where Pt = Transmitted Power at the fiber origin and Pr = Received Power.
So the bigger is the value, the better!
Receiver
A receiver is an optical-to-electrical converter. It includes a detector and signal processing electronics.
Transceiver
A transceiver is a device that performs within one chassis, both telecommunication transmitting and receiving functions.
Transmitter
A transmitter is an electrical-to-optical converter. It includes a source and driving electronics.
VCSEL
A VCSEL is a perfect compromise between a LED and a LASER (point of view price and emission pattern).
