Fiber optic cable offers a range of benefits for corporate data networking and telecommunications, such as thinner, lighter cables and longer signal range. This comprehensive buying guide will discuss:
- What fiber optic cable is
- Key features
- What you should look for when choosing fiber optic cable
- How to find the right kind of fiber optic cable for your network
- The different kinds of optical fiber cable available
What Is Fiber Optic Cable?
It is also known as “optical fiber cable,” fiber optic cable relays data in pulses of light through optically pure, flexible glass or plastic fibers. Thanks to its rapid data transmission speeds over extended distances, fiber optic cable have become a frontrunner for Ethernet networking and telecommunications applications.
How Does It Work?
Light pulses reflect off the sides of the fiber optic cable, moving down the core. No power is necessary to transmit a signal, except for the light source. Light pulses can travel for many miles before weakening and needing a boost.
When determining how far a signal will travel, core size is key. A good rule of thumb is that the smaller the core, the farther the light will go before it needs to be regenerated. Single-Mode Fiber (SMF) features a petite core, keeping the path of light narrow and allowing it to travel up to 100 km. Multimode Fiber (MMF) has a larger core that carries more data but is susceptible to signal quality issues over longer distances, making it better suited to short-haul networks and premises cabling.
Fiber Optic Signal Distance
How far a fiber optic cable can carry a signal depends on the wavelength, the type of cable, and the network. For 10 Gbps multimode cable, ranges average about 984 ft, and single mode cable can reach up to 25 miles. Optical repeaters or amplifiers are employed to regenerate and error correct the optical signal if a longer span is needed.
Fiber Optic Vs. Copper Cable
- Data Transmission: The speed of light is a hundred times faster than electrical conduction. Copper maxes out at 40 Gbps, while OM5 fiber reaches speeds of 100 Gbps.
- Electromagnetic Interference (EMI): Fiber optic cables use light, not electricity, and EMI does not affect them. Copper wires generate an electromagnetic field, which can cause other cables to malfunction.
- Distance: Both copper and fiber cables experience signal loss over long distances, but copper suffers much greater attenuation. Fiber only loses an estimated 3% of its signal strength over 100 meters, while copper loses 94%.
- Cable Weight: Fiber cables are a tenth the weight and a quarter the copper cables’ diameter, making them much easier to install and optimizing airflow in rack enclosures.
- Electrical Isolation: Since fiber optic cables don’t carry electricity, you don’t need to ground the receiver and transmitter, and there isn’t any danger of arcing, electrical shock, heat, or fire.
Fiber Optic Vs. Ethernet Cable
Ethernet cable is often used interchangeably with copper category cable, but Ethernet is the networking protocol devices use to communicate over copper or fiber cable. Network designers may employ either fiber or copper cable, depending on requirements, and may utilize both kinds of cable for different network components. Typically, fiber is used to connect two high-speed devices (like switch to switch) in campus networks and data centers where distance and bandwidth are essential. Sometimes, a network designer can save money utilizing copper cable with similar performance rather than fiber optic cable.
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Choosing The Right Fiber Optic Cable
There is a wide range of cable types with different performance characteristics and specific installation requirements. When choosing fiber optic cable for your network, you should begin by listing requirements for:
- Network Speed
- Cable Jacket
After you’ve narrowed it down, make sure to account for cost and future-proofing. Our experts at C&C Technology Group can help you determine requirements or choose pre-terminated or custom fiber cable.
Network Speed & Distance
Multimode fiber (MMF) used to be the standard for corporate networks and data centers because it was cheaper than single-mode fiber (SMF). Thanks to technological advancements, the cost difference is much more negligible. Rather than comparing single-mode and multimode, consider the distance of the connection and the network speed the overall network design requires. To move a large amount of data over a short distance (i.e, under 300 meters), OM3 MMF may be your best option. Consider SMF if data transmission distance or speed is critical. The cable’s OM rating dictates the MMF range.
Local fire codes must be obeyed when installing indoor fiber cabling. Article 77 of the National Electric Code defines fire rating and jacket identification in the U.S. If your cable needs to run through plenum spaces or risers, account for that in the cable jacket rating. Flexibility and strength under tensile load are other cable jacket properties to consider.
The ports on your network equipment typically dictate fiber optic cable terminations. If your 10G Ethernet switch features multi-fiber MTP ports, for example, then you need a certain amount of fibers in the cable.
Types Of Fiber Optic Cable
Single Mode Vs. Multimode
Fiber optic cable comes in two “modes”: multimode and single-mode. Mode refers to whether it’s single or multiple pulses of light.
Multimode Fiber (MMF)
MMF comes in two core sizes: 50µm and 62.5µm. The relatively wide core can simultaneously carry multiple streams of data at 850 nm or 1300 nm. Multimode fiber employs a Vertical Cavity Surface Emitting Laser (VCSEL) or a light-emitting diode (LED) as its source of light. It is generally used to carry a high volume of data over shorter distances due to high attenuation and dispersion rates. Multimode fiber optic cable is designated as 50/125 or 62.5/125, which refers to the core and cladding diameter.
Single-Mode Fiber (SMF): The core size is much smaller for SMF, comprising 8.3µm or 9µm and a single light path that can travel further. SMF utilizes a laser diode that operates in the 1310 and 1550m range. Single-mode is usually employed in longer spans, like cable TV transmission, campus data networks, and telecommunications networks.
Simplex Vs. Duplex
A Simplex cable employs a single strand of fiber with a transmitter (TX) on one end and a receiver (RX) on the other. The cable isn’t reversible and only transmits one way. Simplex cable is commonly used in monitoring applications, where a sensor transmits time-sensitive data back to the central system.
Full-duplex cable has two fibers that transmit and receive data simultaneously and are essentially two simplex cables working in conjunction to handle bidirectional data transfer. The twin connectors on both ends can transmit and receive at the same time. Half-duplex cables can produce two-way communication, but not simultaneously. Duplex cables are commonly used to link network devices in a high-speed network, like storage systems, servers, and switches.
Duplex Zipcord Fiber
Zipcord is a kind of electrical cable with two or more connectors you can pull apart to separate. Duplex zipcord fiber comprises two fibers wrapped by strength members and an outer jacket.
Mode Conditioning Cables
A Mode Conditioning patch cord (MCP) refers to a duplex cable featuring a single-mode to multimode on the transmit (Tx) side and multimode to multimode on the receive (Rx) side. Remember that you cannot mix single-mode and multimode fiber and equipment on the same network. Single-mode fiber (SMF) and multimode fiber (MMF) have different core sizes, so differential mode delay (DMD) occurs when cable types are mixed, causing receiver errors. DMD can be avoided using Mode Conditioning patch cables, which launch the single-mode signal at an offset to the MMF ore center. The “mode conditioning” generates a signal similar to a normal multimode launch.
Active Optical Cables (AOCs)
Active Optical Cables (AOCs) refer to fiber optic cables that have transceivers bonded permanently to either end, removing the need for connectors. AOCs are commonly found in top-of-rack applications for short link distances. The thin cables maintain airflow with high port density.
Multi-Strand Fiber Cables
Like duplex fiber, multi-strand fiber features multiple strands of fiber relaying data in one direction and an equivalent number of strands transferring data in the other direction. Multi-strand fiber is engineered to support data rates above 25G and utilizes an MPO/MTP connector. Multi-strand fiber cables generally combine 12 or 24 fiber strands (known as12F or 24F) in a single jacket. Multi-strand fiber can also be used as a breakout cable with multiple duplex LC connectors on one end and an MPO/MTP connector on the other end.
For testing signal transmission and diagnosing problems, engineers use a loopback cable called a loopback adapter or loopback tester. Loopback cables plug into a serial or Ethernet port and relay the transmit line to the receiving line to redirect any outgoing signals back into the testing source.
What You Should Know About Fiber Optic Cable Performance
Optical Return Loss
When a pulse of light hits the fiber core’s end, a certain portion of light reflects toward the source, known as the Optical Return Loss (ORL). ORL is expressed in decibels (dB), only impacts fiber with a laser light source, and can lower data transmission speeds. ORL can affect single-mode fiber and multimode fiber if they have a VCSEL light source. ORL doesn’t impact older multimode fiber with an LED light source.
ORL Vs. Back Reflection
The terms ORL and Back Reflection are used interchangeably but are distinct concepts. ORL refers to all of the power lost from the entire system, including the fiber. Reflected power is only one aspect of ORL. Engineers can minimize ORL by making sure connectors are properly mated, and ferrules are clean. Choosing fiber optic cable with end-faces designed to optimize physical interface can also reduce ORL.
Original fiber connectors used ferrules with a basic flat face with a relatively large area that is easily damaged through repeated mating. Physical Contact (PC) connectors are polished to a slightly rounded surface to cut down on the end face size. Ultra Physical Contact (UPC) connectors have end faces with an even larger radius where the fibers connect at the apex of the curve near the fiber core.
Angled Physical Contact (APC) connector ferrules are cleaved at an angle between 15 and 5 degrees, directing the reflected light out of the core for a smaller ORL value.
The total light lost between two fixed points in the fibers known as Insertion Loss and is measured in decibels (dB). Fiber spliced or terminated with a connector can cause Insertion Loss due to dirty ferrules, fiber core misalignment, or poor quality connectors. The total insertion loss of the entire system needs to comply with the installer’s agreed-upon link-loss budget.
Fiber Cable Installation Basics
Minimum Bend Radius
The minimum radius shouldn’t be smaller than 10 times the cable diameter for cables that are not under pulling tension. A multimode cable with an outside diameter of 3.0 mm, for example, should have a minimum bend radius of 30 mm. If the cable is under tensile load, the bend radius may be higher. For further details, look at the cable’s spec sheet.
Maximum Tensile Rating (Pulling Force)
A fiber optic cable may be stressed during installation as it is pulled around bends and through ductwork. Damage can even be caused by pulling a cable from the payoff reel. Cables may also undergo continuous pulling forces after they are installed. A fiber optic cable’s maximum tensile rating is the highest pulling force the cable can stand before damaging its optical properties of fibers. The cable manufacturer generally lists the maximum tensile rating during installation and the maximum tensile rating while in operation.
Consult With C&C Technology Group For Your Fiber Optic Needs
C&C Technology Group is a top infrastructure and advisory firm dedicated to optimizing your business. Work with C&C Technology Group for your fiber optic cabling solutions today!
Looking for the latest fiber optic solutions? Work with C&C Technology Group to optimize your network today!