Fiber Optic Definitions

To navigate the complex world of fiber optics effectively, it's essential to understand the terminology associated with this technology. 

In this comprehensive glossary, we'll break down the key terms into specific categories for a better understanding.

Fiber Optic Performance and Measurements

Fiber optics, as a universal technology, relies on the metric system for measurement standards.  Fiber transports a ton of data in seconds which requires precision, therefore knowing which measurement to use is paramount.

What is used to measure light in fiber optics? 

Fiber optic power meters are used to measure microwatts (mW), Decibels (dB), and decibel milliwatts (dBm, which are some of the most common measurements of light in fiber optics.  

• Watt: A unit of power (one joule per second) in an electric circuit 

• Decibels (dB): A unit of measurement of optical power which indicates relative power. A -10 dB means a reduction in power by 10 times, -20 dB means another 10 times or 10 times overall, -30 means another 10 times or 1000 times overall and so on.

• Optical Power: is measured in "dBm", or decibels referenced to one miliwatt of power. While loss is a relative reading, optical power is an absolute measurement, referenced to standards. You measure absolute power to test transmitters or receivers and relative power to test loss.

• Meter: Equivalent to 3.28 feet (or more precisely, 3.28084 feet).

• Kilometer: Corresponds to 1000 meters, 3,281 feet, or 0.62 miles.

• Micron: Represents 1/1,000,000th of a meter. In the fiber optics industry, it is a common unit of measurement for fibers.

• Nanometer: One billionth of a meter, typically used in the fiber optics industry to express the wavelength or frequency of transmitted light.

• dB: Optical power referenced an arbitrary zero level

• dBm: Optical power referenced to 1 milliwatt

• Wavelength: A term for the color of light, usually expressed in nanometers (nm) or microns (m). Fiber is mostly used in the infrared region where the light is invisible to the human eye.

• Index of Refraction (IOR): A measurement of the speed of light in a particular medium.

• Mode Field Diameter: A measure of the size of the guided lightwave in the core of the fiber.

• Numerical Aperture (NA): A measurement of the range of angles over which the fiber can accept or emit light.

• Refractive Index: A measure of how much a ray of light is bent when it enters a material.

• Velocity of Light: The speed of light in a vacuum, approximately 3 x 10^8 meters per second.

• Chromatic Dispersion: The temporal spreading of a pulse in an optical waveguide caused by the wavelength dependence of the velocities of light.

• Cutoff Wavelength: The wavelength beyond which singlemode fiber only supports one mode of propagation.

• Dispersion: The temporal spreading of a pulse in an optical waveguide, which may be caused by modal or chromatic effects.

What is fiber optic attenuation?

How is fiber optic cable tested?

Optical Time-Domain Reflectometers and Optical Power Meters such as our ZOOM 2 is ideal for both singlemode and multimode fiber testing.

 

• Optical Time Domain Reflectometer (OTDR): A test instrument used to characterize an optical fiber.

• Back Reflection, Optical Return Loss: Light reflected from the cleaved or polished end of a fiber caused by the difference in refractive indices of air and glass. Typically, it accounts for about 4% of the incident light, expressed in dB relative to incident power.

• Backscattering: The scattering of light in a fiber back toward the source, used to make OTDR measurements.

• Scattering: The change of direction of light after striking small particles that causes loss in optical fibers and is used to make measurements by an OTDR

• Edge-Emitting Diode (E-LED): A LED that emits from the edge of the semiconductor chip, producing higher power and narrower spectral width.

• Helium-Neon Laser: A type of gas laser that emits a red light beam.

• Laser: Light Amplification by Stimulated Emission of Radiation.

• Light Emitting Diode (LED): A semiconductor that emits light when current flows through it.

• Light Source: The device that provides the light for a fiber optic system.

• S/N Ratio: Signal-to-Noise ratio.

• Signal: Information-carrying electromagnetic or optical wave.

• Faraday Rotation: The rotation of the plane of polarized light in a magnetic field.

• Polarization: The orientation of electromagnetic wave vibrations.

What causes signal loss in fiber optic cables?

• Bending Loss, Microbending Loss: Loss in fiber caused by stress on the fiber bent around a restrictive radius.  This can occur when bend radius is exceeded on a fiber cable

• Excess Loss: The amount of light lost in a coupler, beyond that inherent in the splitting ratio, caused by reflections and absorption.

• Fusion Splice Loss: The loss of a fusion splice in a fiber optic cable.

• Insertion Loss: The loss of power resulting from the insertion of a device in a transmission line.

• Splice Loss: The loss of power resulting from the fusion of two fibers.

• Optical Loss: The amount of optical power lost as light is transmitted through fiber, splices, couplers, etc, expressed in dB.

 

Fiber Optic Overview

Before diving into any hands on terminology, it's crucial to understand the fundamental components of fiber optics.  If you're interested in continued learning, here are some great fiber optic courses you can take for advanced training.

What are the different parts of a fiber optic cable?

Fiber optic patch cables are made up of a core (singlemode or multimode), cladding, coating, strengthening fibers, and a cable jacket.’

We will dive into each definition further below:

• Core: The central part of the fiber where light transmission occurs.

• Cladding: The outer optical layer that traps and guides light within the core, even through curves.

• Buffer Coating or Primary Coating: A protective hard plastic layer on the outer surface of the fiber, guarding against moisture and physical damage.

• Optical Fiber: Thin strands of highly transparent glass or plastic designed to guide light.

• Jacket: The durable outer covering of the cable, which must meet fire codes for indoor installations.  Check out this guide on how to choose which jacket type for a fiber installation.

What is the difference between the fiber cable types single-mode and multimode?

In general, singlemode cable types support high-speed networks up to 50 times faster than multimode fiber optic cables.  This is not always true and many installers prefer singlemode where multimode might be the best practice by the book. Check out this guide on the optimal speeds by fiber type.

 

Below are a few related terms you should know.

• Mode: A single electromagnetic field pattern (akin to a ray of light) that travels within the fiber.

• Multimode Fiber: Featuring a larger core (62.5 or 50 microns) and employed with LED sources for short-distance, lower-speed networks, such as LANs.

• Singlemode Fiber: With a much smaller core, about 9 microns, networks, telephony, and CATV with laser sources for long-distance, high-speed applications.

• Graded-Index Fiber: A multimode fiber with a core that has a lower refractive index in the center than at the edges.

• Step index multimode: the first fiber design but is too slow for most uses, due to the dispersion caused by the different path lengths of the various modes.

• Plastic Optical Fiber (POF): A multimode fiber with a large core (about 1mm) utilized in short, low-speed networks. POF has gained popularity in consumer HiFi and car communication systems.

• Mode conditioning cables: These are designed to help connect singlemode signals to multimode.  The launch of the light coming out of the equipment begins on a Singlemode fiber, then light is launched on to the multimode fiber at a precise angle, giving the cable its mode conditioning properties.

What are the advantages and disadvantages of fiber optic cable compared to copper cable?

Whether to use copper or fiber depends upon how future proof you need your installation to be.

 

Copper cables are supremely reliable and are perfect for indoor implementations involving equipment that must remain active at all times.

 

Fiber boasts overwhelming speed, capacity and adaptability

Access Points and Network Types

What are the types of access points?

• WAP (Wireless Access Point): A wireless access point (WAP) is a device that allows wireless devices to connect to a wired network. WAPs are commonly used in Wi-Fi networks to provide wireless connectivity within a specific area, typically less than 300 feet away.

• PON (Passive Optical Network): A Passive Optical Network (PON) is a type of telecommunications network that uses fiber-optic cables to distribute signals. Unlike active optical networks, PONs do not require powered equipment for signal transmission, making them more cost-effective and efficient.

• GPON (Gigabit Passive Optical Network): GPON (Gigabit Passive Optical Network) is an advanced version of PON that provides high-speed internet access, voice, and video services over a single fiber-optic connection. It offers faster data transmission and is widely used in modern broadband networks.

• OLT (Optical Line Terminal): The Optical Line Terminal (OLT) is a key component in a PON network. It connects the optical fiber network to the broader internet or service provider network and manages the data traffic between the service provider and the customer's premises.

• ONT (Optical Network Terminal): An Optical Network Terminal (ONT) is the customer-side equipment in a PON network. It is responsible for converting optical signals into electrical signals that can be used by customer devices such as routers and computers.

• ONU (Optical Network Unit): An Optical Network Unit (ONU) is essentially the same as an ONT and is used interchangeably in many cases. It serves as the endpoint device at the customer's location, connecting to the OLT through the PON infrastructure to access internet and other services.

What are the characteristics of a fiber optic cable?

Fiber optic cables can have various strengths such as armored, loose tube, direct burial and more.  These characteristics are important because every installation has different environmental and physical factors.

• Cable: Fiber requires protection when installed, and cables serve this purpose. They can contain anywhere from one to hundreds of fibers.

• Strength Members: Aramid fibers (such as Kevlar) used to help protect and can be used to pull the cable, or fiberglass rods to prevent kinking.

• Armor: Typically of metallic nature located underneath the cable jacket designed to deter rodents from chewing through the cable and to provide crush resistance.

Fiber Optics Components:

What is a fiber optic connector and what are the different types?

 

A connector is located at each end of the fiber patch cable to provide a cabling attachment to the transmit and the receiving device.  The common types of fiber optic connectors are LC, SC, ST, and FC.

 

In addition, there are various polishing types to minimize back reflection.

 

• LC (Lucent Connectors): LC uniboot connectors integrate two fibers into a single cable. This design reduces the number of cables in a high-density cabling installation by reducing cable count by half and eases cable management. 

• SC (Subscriber Connectors): uses a push pull design with a locking tab instead of a latch that LCs have.

• ST (Straight Tip): Similar to FC but utilizes threads.

• FC (Ferule Connector): Used mostly for singlemode connections,  these have a threaded screw-on design.

• Connector: A device that provides for a demountable connection between two fibers or a fiber and an active device and provides protection for the fiber.

• Coupler: An optical device that splits or combines light from more than one fiber.

• Jumper: A short length of fiber connecting two devices.

• End Finish: The quality of the end surface of a fiber prepared for splicing or terminated in a connector.

• Ferrule: A precision tube used to align two fibers for connection.

• Fiber Optic Panel (FOP): A panel for managing and interconnecting fiber optic systems.

• Fiber Pigtail: A short optical fiber permanently attached to a light source or detector.

What are the three types of fiber polishes?

• PC (physical contact): Has a cylindrical cone head with a return loss of about - 40dB. OM1 and OM2 multimode fiber use the PC polish type.

• UPC (ultra physical contact): has a similar, slightly more conical head shape and undergoes extended polishing. As a result, the surface and performance improve return loss to -50dB or higher. However, the head degrades over time with repeated connections and disconnections due to the precision contact surface.

• APC (angled physical contact): Has a slightly angled tip with an end face radius at an 8° angle. This design minimized the back reflection too -60dB.

Fiber Optic Applications

Termination overview

Termination is a critical aspect of fiber optics. It involves preparing the end of a fiber for connection. Explore the following terms:

• Connector: A non-permanent device for connecting two fibers or fibers to equipment. It offers protection and is suitable for occasional disconnection, testing, or rerouting.

• Splice: A permanent connection between two fibers.

• Mechanical Splice: A splice created through mechanical alignment.

• Fusion Splice: Achieved by welding or fusing two fibers.

• Fusion Splicer: An instrument for splicing fibers via electrical arc.

• Hardware: Terminations and splices require additional hardware for protection and management, such as patch panels and splice closures.

Termination Tools

• Jacket Slitter or Stripper:A cutter for removing the heavy outside jacket of cables

• Fiber Stripper: A precise stripper used to remove the buffer coating of the fiber itself for termination. There are three types in common use, called by their trade names: "Miller Stripper", "No-Nik" and "Micro Strip."

• Cleaver: A tool that precisely "breaks/cuts" the fiber to produce a flat end for polishing or splicing.

• Scribe: A hard, sharp tool that scratches the fiber to allow cleaving.

• Polishing Puck: for connectors that require polishing, the puck holds the connector in proper alignment to the polishing film.

• Polishing Film: Fine grit film used to polish the end of the connector ferrule.

• Crimper: A tool that crimps the connector to the aramid fibers in the cable to add mechanical strength.

What is the difference between a coupler and a splitter in fiber optics?

While both devices divide, route, or combine optical signals, a splitter sends data in multiple points while a coupler joins fiber cables that may have different shapes and cores.

What tool is used to cut fiber optic cable? 

A high precision fiber optic cleaver should be used to provide a clean and precise cleave of fiber optic glass.

Measurement and Testing:

• Cutback Method: A technique for measuring the loss of bare fiber by measuring the optical power transmitted through a long length, then cutting back to the source and measuring the initial coupled power.

• Optical Loss Test Set (OLTS): A test set used to measure the total optical power transmitted through a fiber optic cable.

• Optical Power Meter: A test instrument used to measure optical power.

• Optical Spectrum: A range of optical wavelengths.

• Spectrum Analyzer: An instrument that displays the signal levels of a fiber.

Testing Equipment

• Optical Power Meter: An instrument that measures optical power from the end of a fiber

• Test Source: an instrument that uses a laser or LED to send an optical signal into fiber for testing loss of the fiber

• Optical Loss Test Set (OLTS): A measurement instrument for optical loss that includes both a meter and source

• Reference Test Cables: short, single fiber cables with connectors on both ends, used to test unknown cables.

• Mating Adapter: also called splice bushing or couplers, allow two cables with connectors to mate.

• Fiber Tracer: An instrument that allows visual checking of continuity and tracing for correct connections

• Visual Fault Locator: A device that allows visual tracing and testing of continuity by illuminating a particular strand of fiber with a laser.

• Microscope: used to inspect the endface or surface of a connector for flaws or dirt.

• Contamination: In terms of Fiber, contamination can be liquid, dust, or any other microscopic material that can lead to attenuation.  This is why it's important to keep your fiber connectors clean.

 

Data Transmission and Communication:

• Bit-Error Rate (BER): The fraction of data bits transmitted that are received in error.

• Bit: An electrical or optical pulse that carries information.

• Digital: Signals encoded into discrete bits.

• Modulation: The encoding of digital information onto a carrier wave.

• Transceiver: A transmitter/receiver.

• Transmitter: The part of a fiber optic link that converts electrical signals into optical signals.

• LAN (Local Area Network): A Local Area Network (LAN) is a network that covers a relatively small geographic area, such as a single building or a campus. LANs are used for connecting computers, devices, and resources within the same physical location, enabling them to communicate and share information.

• WAN (Wide Area Network): A Wide Area Network (WAN) is a network that spans a larger geographic area, often connecting multiple LANs or individual devices over long distances. WANs facilitate data transmission between different locations and can use various technologies, including public and private networks.

• POE (Power over Ethernet): Power over Ethernet (PoE) is a technology that allows electrical power and data to be transmitted over an Ethernet network cable simultaneously. PoE is often used to power devices like IP cameras, phones, and wireless access points (WAPs) via the network cable.

Networks and Connectivity:

• Backbone cabling: The portion of your network cabling that connects various rooms and communication panels.

• CATV: An abbreviation for Community Antenna Television or cable TV.

• ESCON: IBM standard for connecting peripherals to a computer over fiber optics. Acronym for Enterprise System Connection.

• Fiber Optic Backlight: A light source used for displays, consisting of a flat slab of glass or plastic.

• Fiber-to-the-Home (FTTH): The installation and use of optical fiber from a central point directly to individual buildings, such as residences and businesses.

• Fiber-to-the-X (FTTX):  encompasses a range of broadband optical fiber distribution configurations categorized according to the point at which the fiber optic line terminates and the transition to metallic network lines occurs.

• Fiber-to-the-Antena (FTTA) utilized when fiber network lines extend to radio antennas equipped with optical transceivers and transmitters for the conversion of optical signals into radio waves. FTTA networks form the fundamental infrastructure for 3G, 4G, and 5G mobile networks. 

• Fibre Channel: A set of American National Standards Institute (ANSI) standards for data transmission.

• Fibre Channel Protocol (FCP): A protocol for accessing and managing data on a Fibre Channel network.

• Link Loss Budget: The total allowable loss for a fiber optic link, considering all components.

• Router: A device that forwards data packets between computer networks.

• Time Division Multiplexing (TDM): A method for putting multiple signals on a single transmission line.

Codes

• TIA Codes: A set of standards and guidelines established by the Telecommunications Industry Association (TIA) that govern various aspects of the telecommunications industry, including cabling standards, infrastructure design, and performance specifications.

• 606: TIA-606 is a specific standard within the TIA codes that provides guidelines for the administration and labeling of telecommunications cabling and infrastructure within a facility. It helps ensure that cabling systems are organized and well-documented.

• 568: TIA-568 is another standard within the TIA codes that specifies the design and performance requirements for structured cabling systems, particularly those used in Ethernet networks. It covers aspects like cable categories, connectors, and wiring schemes.

• EIA 569: EIA-569, now part of the TIA standards, provides guidelines for designing and constructing telecommunications pathways and spaces, including telecom rooms and pathways between them. It focuses on ensuring efficient cable management, organization, and physical infrastructure for telecommunications systems.

• PON (Passive Optical Network): A Passive Optical Network (PON) is a fiber-optic telecommunications network architecture that uses point-to-multipoint topology to provide broadband access. PONs are typically used for delivering services like internet, voice, and video to subscribers. They are characterized by passive components and optical splitters that enable shared fiber connections.

Types of Installation

Premises Cable Installations

Premises cabling includes cabling installed in a building or campus.  Most cables are short lengths, rarely longer than a few hundred feet, with 2 to 48 fibers per cable typically. The fiber is mostly multimode, except for the enlightened user who installs hybrid cable with both multimode and singlemode fibers.

Indoor installations include running cables through floors, ceilings and walls.  Often, these cables must be plenum rated so they can withstand, or not cause, and fire damage. 

• Plenum: When constructing a building, there is a separate space provided for air circuluation such as heating, ventilation, and air-conditioning.  It is commonly located in ceilings, drop ceilings, or under a raised floor.
• Plenum rated cables: These are cables that are able to be installed in plenum areas of indoor installations that limit the amount of smoke that is released and they have low flame characteristics.  If a plenum cable catches fire, it won't release toxic fumes the way a non-plenum rated cable would.  Since this is in the plenum space of a building, those fumes would get circulated and be very harmful to anyone in the building.

Outside Plant (OSP) Installations

There are four main types of OSP installation including underground, direct burial, aerial, and underwater.

• Underground OSP Projects: these projects involve the installation of fiber optic cables below the ground's surface in conduit. This method is often used in urban areas where aesthetics and protection are paramount.
• Direct Burial (Sewers) OSP Projects: these projects involve laying fiber optic cables directly into the ground without the use of conduit or ducts. This method is cost-effective and often used in rural areas.
• Outdoor Aerial OSP Projects: these projects involve the installation of fiber optic cables on overhead support structures, such as utility poles. This method is suitable for rural and suburban areas.
• Underwater OSP Projects: these projects involve laying fiber optic cables on the seabed, often for submarine communications or marine research.
• Conduit: Useful to help protect cables from moisture, tearing, small rodents, temperatures, and flooding in OSP installations.  When designing a conduit run, you'll need to consider the cable size.  This means you can't just choose any size and you must choose the right conduit for your fiber installation.
• Designing Cable Networks: In order to lay fiber, you need to plan where everything should go.  This involves visiting the worksite, identify where servers or patch panels will be placed, and more.
• Project Estimates and Bidding: Estimating involves quoting out the equipment and labor costs involved in an installation job and is necessary to figure out what the job will cost you.

With this organized glossary, you can delve into the world of fiber optics with a clear understanding of its terminology and how it fits into various categories. Whether you're new to fiber optics or a seasoned professional, this glossary provides a valuable resource for effective communication and troubleshooting in the field.