OPTICAL FIBRE

Read the following text with gaps and match the headings to its parts (A, B, C, D, E):

Types Usage Joining together Description History

Now read the text again a part by part and fill in the gaps with the words from the boxes in each part:

signal system communications carries light message

Nowadays, optical fiber is the most common type of channel for optical (1) __________ . Optical communication is any form of telecommunication that uses (2) __________ as the transmission medium. An optical communication (3) __________ consists of a transmitter, which encodes a message into an optical (4)__________ , a channel, which (5) __________ the signal to its destination, and a receiver, which reproduces the (6) __________ from the received optical signal.

A ____________________________

cable light transparent protective ducts distance glass made plastic diameter

An optical fiber cable is a cable containing one or more optical fibers. An optical fiber (or fiber) is a (7) __________ or plastic fiber that carries (8) __________ along its length. The optical fiber elements are typically individually coated with (9)__________ casing and are contained in a (10) __________ tube suitable for the environment where the cable will be deployed.

Fibers can be made out of (11) __________ (or clear) plastic, glass, or a combination of the two. The fibers used in long- (12) __________ telecommunications are always (13) __________ of glass.

Fiber (14) __________ can be very flexible, but traditional fiber's loss increases greatly if the fiber is bent with a (15) __________ smaller than around 60 mm. Usually optical fibre cables are put into the underground cabling (16) __________ .

B ____________________________

used diameter short single metres

Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those which can only support a (17) __________ mode are called single-mode fibers (SMF). Multi-mode fibers generally have a larger core (18) __________ , and are used for (19) __________-distance communication links and for applications where high power must be transmitted. Single-mode fibers are (20) __________ for most communication links longer than 550 (21) __________ (1,800 ft).

C ____________________________

property optical modern century Paris physicist technology 1870 demonstrated experiments

Fiber optics, though used extensively in the (22) __________ world, is a fairly simple and old (23) __________ . Guiding of light by refraction, the principle that makes fiber optics possible, was first (24) __________ by Daniel Colladon and Jacques Babinet in (25) __________ in the early 1840s.

John Tyndall included a demonstration of it in his public lectures in London a dozen years later. Tyndall also wrote about the (26) __________ of total internal reflection in an introductory book about the nature of light in (27) __________ : "When the light passes from air into water, the refracted ray is bent towards the perpendicular... When the ray passes from water to air it is bent from the perpendicular...”

Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth (28) __________ . Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for internal medical examinations by Heinrich Lamm in the following decade. In 1952, (29)__________ Narinder Singh Kapany conducted (30) __________ that led to the invention of optical fiber. Modern (31) __________ fibers, where the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade.

D ____________________________

harmed metal bandwidths ignite electricity communications equipment carry space repeaters

Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher (32) __________ (data rates) than other forms of communications. Fibers are used instead of (33) __________ wires because signals travel along them with less loss.

Over short distances, such as networking within a building, fiber saves (34) __________ in cable ducts because a single fiber can (35) __________ much more data than a single electrical cable. Fibres are also not (36) __________ by electromagnetic interference; there is no cross-talk between signals in different cables and no pickup of environmental noise. Non-armored fiber cables do not conduct (37) __________ , which makes fiber a good solution for protecting communications (38) __________ that is located in high voltage environments such as power generation facilities, or metal communication structures prone to lightning strikes. They can also be used in environments where explosive fumes are present, as they don’t (39) __________ and there is no danger of ignition.

Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance (40)__________ , because light propagates through the fiber with little attenuation compared to electrical cables. This allows long distances to be spanned with few (41) __________ .

large equipment building Industrial analyse environment illumination objects used level designed

Fibers are also widely used for (42) __________ . Optical fiber illumination is also used for decorative applications, including signs, art, and artificial Christmas trees. Swarovski boutiques use optical fibers to illuminate their crystal showcases from many different angles while only employing one light source.

In some buildings, optical fibers are used to route sunlight from the roof to other parts of the (43) __________ . Specially (44) __________ fibers are used for a variety of other applications, including sensors and fiber lasers.

They are used as light guides in medical and other applications where bright light needs to be shone on a target without a clear line-of-sight path.

Optical fiber is also used in imaging optics. A coherent bundle of fibers is used, sometimes along with lenses, for a long, thin imaging device called an endoscope, which is used to view (45) __________ through a small hole. Medical endoscopes are used for minimally invasive exploratory or surgical procedures (endoscopy). (46) __________ endoscopes are used for inspecting anything hard to reach, such as jet engine interiors.

In spectroscopy, optical fiber bundles are (47) __________ to transmit light from a spectrometer to a substance which cannot be placed inside the spectrometer itself, in order to (48) __________ its composition. A spectrometer analyses substances by bouncing light off of and through them. By using fibers, a spectrometer can be used to study objects that are too (49) __________ to fit inside, or gasses, or reactions which occur in pressure vessels.

Optical fiber can be used to supply a low (50) __________ of power (around one watt) to electronics situated in a difficult electrical (51) __________ . Examples of this are electronics in high-powered antenna elements and measurement devices used in high voltage transmission (52)__________ .

E ____________________________

used screen copper special process together temperature instrument controlled

Fiber splicing is much more difficult than splicing (53) __________ wire.
Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with an electric arc. Special connectors are used to make removable connections.

As it has already been mentioned, optical fibers may be connected to each other by connectors or by splicing, that is, joining two fibers (54) __________ to form a continuous optical waveguide. The generally accepted splicing method is arc fusion splicing, which melts the fiber ends together with an electric arc. For quicker fastening jobs, a "mechanical splice" is (55) __________ .
Fusion splicing is done with a specialized (56) __________ that typically operates as follows: The two cable ends are fastened inside a splice enclosure that will protect the splices, and the fiber ends are stripped of their protective polymer coating. The ends are cleaved (or cut) with a precision cleaver to make them perpendicular, and are placed into (57) __________ holders in the splicer. The splice is usually inspected via a magnified viewing (58) _________ to check the cleaves before and after the splice. The splicer uses small motors to align the end faces together, and emits a small spark between electrodes at the gap to burn off dust and moisture. Then the splicer generates a larger spark that raises the (59) _________ above the melting point of the glass, fusing the ends together permanently. The location and energy of the spark is carefully (60) __________ so that the molten core and cladding don't mix, and this minimizes optical loss. A splice loss estimate is measured by the splicer, by directing light through the cladding on one side and measuring the light leaking from the cladding on the other side. A splice loss under 0.1 dB is typical. The complexity of this (61) __________ is rather obvious.

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