In physics, attenuation is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates.
An optical attenuator, or fiber optic attenuator, is a device used to reduce the power level of an optical signal, either in free space or in an optical fiber. The basic types of optical attenuators are fixed, step-wise variable, and continuously variable.
An optical time-domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber. It is the optical equivalent of an electronic time domain reflectometer which measures the impedance of the cable or transmission line under test. An OTDR injects a series of optical pulses into the fiber under test and extracts, from the same end of the fiber, light that is scattered or reflected back from points along the fiber. The scattered or reflected light that is gathered back is used to characterize the optical fiber. The strength of the return pulses is measured and integrated as a function of time, and plotted as a function of length of the fiber.
In fiber-optic communication, a single-mode optical fiber (SMF), also known as fundamental- or mono-mode, is an optical fiber designed to carry only a single mode of light - the transverse mode. Modes are the possible solutions of the Helmholtz equation for waves, which is obtained by combining Maxwell's equations and the boundary conditions. These modes define the way the wave travels through space, i.e. how the wave is distributed in space. Waves can have the same mode but have different frequencies. This is the case in single-mode fibers, where we can have waves with different frequencies, but of the same mode, which means that they are distributed in space in the same way, and that gives us a single ray of light. Although the ray travels parallel to the length of the fiber, it is often called transverse mode since its electromagnetic oscillations occur perpendicular (transverse) to the length of the fiber. The 2009 Nobel Prize in Physics was awarded to Charles K. Kao for his theoretical work on the single-mode optical fiber. The standards G.652 and G.657 define the most widely used forms of single-mode optical fiber.
A transmission medium is a system or substance that can mediate the propagation of signals for the purposes of telecommunication. Signals are typically imposed on a wave of some kind suitable for the chosen medium. For example, data can modulate sound, and a transmission medium for sounds may be air, but solids and liquids may also act as the transmission medium. Vacuum or air constitutes a good transmission medium for electromagnetic waves such as light and radio waves. While a material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance, by absorption or reflection or refraction at the interfaces between media. Technical devices can therefore be employed to transmit or guide waves. Thus, an optical fiber or a copper cable is used as transmission media.
In computer networking, Gigabit Ethernet is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use in 1999, and has replaced Fast Ethernet in wired local networks due to its considerable speed improvement over Fast Ethernet, as well as its use of cables and equipment that are widely available, economical, and similar to previous standards. The first standard for faster 10 Gigabit Ethernet was approved in 2002.
Small Form-factor Pluggable (SFP) is a compact, hot-pluggable network interface module format used for both telecommunication and data communications applications. An SFP interface on networking hardware is a modular slot for a media-specific transceiver, such as for a fiber-optic cable or a copper cable. The advantage of using SFPs compared to fixed interfaces is that individual ports can be equipped with different types of transceivers as required, with the majority including optical line terminals, network cards, switches and routers.
A passive optical network (PON) is a fiber-optic telecommunications network that uses only unpowered devices to carry signals, as opposed to electronic equipment. In practice, PONs are typically used for the last mile between Internet service providers (ISP) and their customers. In this use, a PON has a point-to-multipoint topology in which an ISP uses a single device to serve many end-user sites using a system such as 10G-PON or GPON. In this one-to-many topology, a single fiber serving many sites branches into multiple fibers through a passive splitter, and those fibers can each serve multiple sites through further splitters. The light from the ISP is divided through the splitters to reach all the customer sites, and light from the customer sites is combined into the single fiber. Many fiber ISPs prefer this system.
A link budget is an accounting of all of the power gains and losses that a communication signal experiences in a telecommunication system; from a transmitter, through a communication medium such as radio waves, cable, waveguide, or optical fiber, to the receiver. It is an equation giving the received power from the transmitter power, after the attenuation of the transmitted signal due to propagation, as well as the antenna gains and feedline and other losses, and amplification of the signal in the receiver or any repeaters it passes through. A link budget is a design aid, calculated during the design of a communication system to determine the received power, to ensure that the information is received intelligibly with an adequate signal-to-noise ratio. Randomly varying channel gains such as fading are taken into account by adding some margin depending on the anticipated severity of its effects. The amount of margin required can be reduced by the use of mitigating techniques such as antenna diversity or multiple-input and multiple-output (MIMO).
An optical fiber connector is a device used to link optical fibers, facilitating the efficient transmission of light signals. An optical fiber connector enables quicker connection and disconnection than splicing.
An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss and are immune to electromagnetic interference. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, such as fiber optic sensors and fiber lasers.
Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared or visible light through an optical fiber. The light is a form of carrier wave that is modulated to carry information. Fiber is preferred over electrical cabling when high bandwidth, long distance, or immunity to electromagnetic interference is required. This type of communication can transmit voice, video, and telemetry through local area networks or across long distances.
Telecommunications engineering is a subfield of electronics engineering which seeks to design and devise systems of communication at a distance. The work ranges from basic circuit design to strategic mass developments. A telecommunication engineer is responsible for designing and overseeing the installation of telecommunications equipment and facilities, such as complex electronic switching system, and other plain old telephone service facilities, optical fiber cabling, IP networks, and microwave transmission systems. Telecommunications engineering also overlaps with broadcast engineering.
Gap loss is a type of signal strength loss that occurs in fiber optic transmission when the signal is transferred from one section of fiber or cable to another.
A fiber-optic cable, also known as an optical-fiber cable, is an assembly similar to an electrical cable but containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable is used. Different types of cable are used for fiber-optic communication in different applications, for example long-distance telecommunication or providing a high-speed data connection between different parts of a building.
An optical power meter (OPM) is a device used to measure the power in an optical signal. The term usually refers to a device for testing average power in fiber optic systems. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power meters, light meters or lux meters.
Electrical or fiber-optic connectors used by U.S. Department of Defense were originally developed in the 1930s for severe aeronautical and tactical service applications, and the Type "AN" (Army-Navy) series set the standard for modern military circular connectors. These connectors, and their evolutionary derivatives, are often called Military Standard, "MIL-STD", or (informally) "MIL-SPEC" or sometimes "MS" connectors. They are now used in aerospace, industrial, marine, and even automotive commercial applications.
Radio over fiber (RoF) or RF over fiber (RFoF) refers to a technology whereby light is modulated by a radio frequency signal and transmitted over an optical fiber link. Main technical advantages of using fiber optical links are lower transmission losses and reduced sensitivity to noise and electromagnetic interference compared to all-electrical signal transmission.
TOSLINK is a standardized optical fiber connector system. Generically known as optical audio, the most common use of the TOSLINK optical fiber connector is in consumer audio equipment in which the digital optical socket carries (transmits) a stream of digital audio signals from audio equipment to an AV receiver that can decode two channels of uncompressed, pulse-code modulated (PCM) audio; or decode compressed 5.1/7.1 surround sound audio signals, such as Dolby Digital and DTS. Unlike an HDMI connector cable, a TOSLINK optical fiber connector does not possess the bandwidth capacity to carry the uncompressed audio signals of Dolby TrueHD and of DTS-HD Master Audio; nor carry more than two channels of PCM audio.
STANAG 3910High Speed Data Transmission Under STANAG 3838 or Fibre Optic Equivalent Control is a protocol defined in a NATO Standardization Agreement for the transfer of data, principally intended for use in avionic systems. STANAG 3910 allows a 1 Mb/s STANAG 3838 / MIL-STD-1553B / MoD Def Stan 00-18 Pt 2 (3838/1553B) data bus to be augmented with a 20 Mb/s high-speed (HS) bus, which is referred to in the standard as the HS channel: the 3838/1553B bus in an implementation of STANAG 3910 is then referred to as the low-speed (LS) channel. Either or both channels may be multiply redundant, and may use either electrical or optical media. Where the channels use redundant media, these are individually referred to as buses by the standard.
