Optical fibers are now commonly used to transmit light signals from one place to another for a variety of applications. Optical communication technologies are employed in a wide variety of communication environments which include, for example, telecommunications, networking, data communications, industrial communication links, medical communications links, etc. Optical fiber is useful in communication networks to transmit digital and analog information via modulated optical signals. Fiber optics is of increasing importance in both medical imaging and treatment. Optical fibers are used in the medical field to transport laser energy through flexible catheters for pin-point microsurgery. For example, in the area of photodynamic therapy, where a patient is injected with a photodynamic therapeutic agent followed by irradiation, fiber optics have become a radiation delivery method of choice. Optical fibers are finding use in a number of specialized applications such as long distance, secure, data links for military communications, data buses for satellite and space vehicle systems and real time imaging systems. Such imaging systems includes optical fiber systems for monitoring environmental and experimental conditions around nuclear reactor facilities, and optical fiber data links for plasma fusion reactors where extremely high electromagnetic fields can degrade electrical transmission systems. Fiber optic probes have long been used to measure the properties of solutions. Such probes use optical fibers to send out light to interact with the solution. Over the past decade, fiber optic sensors have received attention in the application of magnetic field sensing and current sensing. Fiber optic circuitry is increasingly being used in electronics systems where circuit density is ever-increasing and is difficult to provide with known electrically wired circuitry. Fiber optic illumination systems are widely used for landscape lighting and holiday decorations.

Transmission of data by optical fiber waveguides, also called fiber optics or optical fibers, has become ubiquitous in the telecommunications and computer industries. The telecommunications industry has long recognized the many advantages fiber optic cabling and transmission devices hold over traditional copper wire and transmission systems. Fiber optic communication has a number of advantages over traditional transmission means such as hard-wired coaxial and twisted pair cable and lower frequency electromagnetic broadcasting such as radio and microwave. Optical fibers are very small diameter glass strands which are capable of transmitting an optical signal over great distances, at high speeds, and with extremely low signal loss as compared to standard wire or cable networks. Fiber optic systems provide significantly higher bandwidth and greater performance and reliability than standard copper wire systems. Optical fibers also require fewer repeaters over a given distance to keep a signal from deteriorating. Fiber optic connections are far less vulnerable to electromagnetic disruptions and nuclear radiation, whether of natural origin or the result of the use of certain military weapons. Optical fibers are immune to electromagnetic interference and to crosstalk from adjoining wires. Additionally, cables o f optical fibers can be made smaller and lighter than conventional copper wire or coaxial tube cables. Optical fibers can carry much more information, making them useful for transmitting large amounts of data between computers and for carrying bandwidth-intensive television pictures or many simultaneous telephone conversations.

An optical communication system includes optical transmission cables for transmitting optical signals. Fiber optic cables have gained increased use in a number of applications, as in computer interconnection, process controls, industrial automation, data transmission links and communications in general. A fiber optic cable typically comprises an optical fiber concentrically surrounded by a series of protective layers. Optical fibers intended for manufacture of telecommunications cables are typically coated with one or more polymer layers. The polymers provide mechanical protection of the fiber surface, and are colored for identification purposes. The coated optical fibers, singly or in groups, are typically covered with one or more of a number of jackets that provide structural support and environmental protections. The aggregate of the optical fiber, jackets, and additional integrated mechanical supports, is typically referred to as an fiber optic cable. Fiber optic cables using optical fiber ribbons can result in a relatively high optical fiber-density. Fiber optic ribbons include optical waveguides such as optical fibers that transmit optical signals, for example, voice, video, and/or data information. Fiber optic ribbon configurations can be generally classified into two general categories. Namely, fiber optic ribbons with subunits and those without. A fiber optic ribbon with a subunit configuration includes at least one optical fiber surrounded by a primary matrix forming a first subunit, and a second subunit having a similar construction, which are contacted and/or encapsulated by a secondary matrix. Fiber optic ribbons without subunits generally have a plurality of optical fibers surrounded by a single layer of matrix material. Fiber optic cables include a plurality of optical fibers housed within one or more protective layers. The number of fibers included in the cable, and the materials and thicknesses thereof used to form the protective layers, are selected based on the type of application or installation of the cable.

A optical communications system comprises a transmitter of optical signals, a length of transmission optical fiber coupled to the source, and a receiver coupled to the fiber for receiving the signals. Filters and attenuators are required in these systems to change the power levels of various signals. Optical fiber communication systems typically comprise a modulated laser source, a length of optical transmission fiber and a receiver. Light from the laser is typically modulated into signal pulses at a high bit and launched into the transmission fiber. The transmission fiber carries the signal pulses to the receiver where the signal is demodulated. Intermediate between the transmitter and the receiver, the transmission path may include optical fiber amplifiers to compensate amplitude loss, add/drop modes to permit the addition or dropping of signal channels at intermediate points, and chromatic dispersion compensators to compensate the tendency of different wavelength components of pulses to travel through the fiber at slightly different speeds. An advanced commercial optical communication system utilizes numerous signal channels over a wide bandwidth in each optical fiber in a wavelength division multiplexed (WDM) transmission cable system to achieve high speed and high capacity optical signal transmission. Within optical fiber communication systems, fiber distribution frames or lightguide cross-connect frames are used to optically couple various optical fiber networks. A fiber distribution frame typically includes one or more bays, with each bay including a plurality of fiber distribution shelves. The distribution frame includes one or more covers for protecting the fiber distribution shelves. Generally, optical signals delivered from optical fibers must be optically coupled to many types of optical components, such as filters, interferometers, beam splitters, etc. The transmitters and receivers are often integrated into a single component called a transceiver. Transmitters are light sources, such as lasers or light-emitting diodes. Receivers usually include a photo detector.

In fiber optic networks, light signals are transmitted along optical fibers to transfer information from one location to another. Optical switches are used to selectively couple light from an input fiber to an output fiber. Optical fibers typically have very small cross-sections and narrow acceptance angles within which light entering the fiber must fall to promote efficient propagation of the light along the fiber. Optical switches transfer light with precise alignment. These fibre optic switches allow switching of electrical loads from locations where traditional electrical switches can create the risk of sparks and electrical shorts. Optical fiber gratings are important elements for controlling light within fibers. A fiber grating typically comprises a length of fiber including a plurality of substantially equally spaced optical grating elements such as index perturbations, slits or grooves. Fiber optic connectors of a wide variety of designs have been employed to terminate optical fiber cables and to facilitate connection of the cables to other cables or other optical fiber transmission devices. Fiber optic coupling devices are used in a wide variety of applications to couple an optical signal from one optical fiber, or optical fiber bundle, to another optical fiber or optical fiber bundle. Fiber coupled optical polarization beam splitters and combiners are used in fiber-based communication systems to perform various functions, for example to combine two laser beams having orthogonal polarizations to produce a single beam having a higher total output power as well as low polarization dependence. The fiber optic amplifiers are optical devices to which a silica-based amplification optical fiber with a core region, an equivalent of an optical waveguide region, doped with a rare earth element is applied as an optical amplifying medium and in which the amplification optical fiber amplifies signals under supply of pumping light. Fiber optic attenuators are optical components that induce a calibrated loss between two connectors to dampen an optical signal. Attenuation is desirable if the optical signal has a power level that exceeds the operating range of the equipment to which the signal is being transferred.

Fiber optic sensors become attractive innovation with applications in many areas of industry and engineering. Fiber optic sensors offer a series of advantages over conventional electronic sensors used to measure temperature, strain, ultrasonic pressure, and other properties. These advantages include small size, high sensitivity, immunity to electromagnetic interference, high temperature capability, multiplexing potential, and low cost. The small size makes fiber optic sensors good candidates for embedding within structures. Embedded sensors measure parameters at locations not accessible to ordinary sensors, and allow for real-time measurements during fabrication and use of structures. They can also be used for non-contact measurements because they do not require wiring between the sensor and detector. Optical fiber, due to its properties, can play roles of both sensitive element and signal delivery channel. Distributed fiber optics sensors are suitable for monitoring of large pieces of equipment such as planes, ships, factory equipment, pipelines, and construction structures like buildings, bridges, etc. Fiber optic current sensors are particularly advantageous over iron-core current transformers, since fiber optic sensors are non-conductive and light weight. Fiber optic sensors also do not exhibit hysteresis and provide a much larger dynamic range and frequency response. Fiber optic interferometric sensors offer a number of advantages over electrical sensors such as inherent immunity to electromagnetic interference, capability of operating in harsh environments and at longer distances, miniature sizes, etc. A fiber optic sensing coil is commonly used in fiber optic rotation sensing devices, such as an interferrometric fiber optic gyroscope. The fiber optic sensing coil is a continuous optical fiber wound in a circular or looped shape that acts as a sensing device to detect a Sagnac phase difference for two counter-propagating beams in presence of rotation.

There are a variety of fiber optic sensors, such as Bragg grating sensors, fiber laser sensors, and interferometric sensors. Many fiber optic sensing systems are developed using in-fiber Bragg gratings. Bragg gratings have narrow reflection spectral bands whose position within the optical spectrum depends on certain conditions, like temperature and axial strain. Arrays of fiber optic interferometric sensors show promise in applications where size, electrical interference, and electromagnetic detection make electronic sensors impractical. Such interferometric sensors are capable of measuring a parameter with a very high dynamic range. Fiber optic interferometers are implemented in sensors and sensor arrays to measure physical properties such as acoustic level, pressure, acceleration, temperature, electric and magnetic fields. An interferometric fiber optic sensor operates by splitting light from a light source into two different paths and subsequently recombining the two components to produce an interference fringe whose properties are related to the quantity being measured by the sensor. Position sensors are used in a wide variety of automated manufacturing applications. A fiber optic position sensor uses an adjacent pair of fiber optic lines, one to carry light from a remote source to an object or target whose position or motion is to be sensed, and the other to receive the light reflected from the object and carry it back to a remote photo sensitive detector. Fiber optic vibration sensors have been used in a wide variety of applications, from monitoring machinery conditions to detecting motion for alarm systems. Optical fiber pressure sensors are needed for measurement of pressure in extreme high temperature, high pressure and corrosive environments such as oil well downholes, jet engines, or power generation equipment. Optical couplers are commonly used to couple optical signals from a distribution bus to the sensors, and from the sensors to a return bus.

Illuminating apparatuses such as fiber optic lighting systems are used in a variety of applications to provide a cool, flexible, safe source of light. Fiber optic cable transmit light in a longitudinal mode, such cable can also transmit light laterally. Lateral emissions from fiber optic cable are useful for area lighting and spotlighting, such as around swimming pools, walkways, signs, and for other safety and decorative accent lighting applications. Fiber optic illumination systems are designed to meet specific requirements that a standard illumination system cannot meet. Pool lighting systems must be designed to provide a significant amount of light, and yet be safe from contamination and/or damage from the effects of exposure to water. Fiber optic light systems allow a light source to be located away from a pool's body of water, and thus provide for a safe distance between electrical components and the water. Fiber optic cables are also used for decorating Christmas trees to create colorful lighting effects which are unable to be achieved with traditional lighting sources. When displayed at festivals and holiday celebrations, the fiber-optic Christmas tree can bring much fun and better atmosphere. Fiber optic illumination systems generally consist of a light source, a light guide device for transmitting the light from the light source, and an optical coupling of the light source to the light guide.