Fiber optic transmission systems and their components

Objectives: In this chapter, you will learn:

How fiber optic data links and transmission systems work.

What components are used in transceivers?

What types of sources and detectors are used in transceivers?

The performance parameters of fiber optic transmission systems.

Fiber optic data links

Fiber optic transmission systems use data links that work similarly to the one illustrated in the diagram above. Each fiber link consists of a transmitter at one end of the fiber and a receiver at the other. Most systems operate by transmitting in one direction through one fiber and in the opposite direction through another fiber in order to have a two-way transmission. It is possible to transmit in both directions through a single fiber but couplers are needed to do so, and the fiber is less expensive than them.

Most systems use a " transceiver " that includes both a transmitter and a receiver in a single module. The transmitter takes an electrical pulse and converts it into an optical output from a laser diode or LED. The light from the transmitter is coupled to the fiber with a connector and transmitted through the network of fiber optic cables. The fiber end light is coupled to the receiver, where a detector converts the light into an electrical signal that is then conditioned so that it can be used in the receiving equipment.

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Analog or digital

The analog signals are continuously variable and the information contained in them is in the amplitude of the signal with respect to time. The digital signals are sampled at regular time intervals and the amplitude is converted to digital bytes, therefore the information is a digital number. Analog signals are the most common form of data transmission, but suffer degradation by the noise present in the transmission system. Because the analog signal is attenuated in a cable, the signal-to-noise ratio worsens and consequently, the signal quality degrades.

Variable delay device for optical signals.

Variable delay device for optical signals.

A variable delay device for optical signals is proposed. In order to reduce the switching time, this device comprises a connector and a multiplexer containing n inputs tuned to n different wavelengths, respectively. The inputs of this multiplexer are connected to the outputs of the connector through various wavelength conversion devices and various LZs. Each conversion device issues respectively. multiplexer input wave, the length of which corresponds to this input. The invention also relates to a device for synchronizing the channels of a multiplexer along a wavelength using said variable delay device.
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A needle for separating and pulling communication cables.

A needle is proposed for separating and pulling communication cables in which m. optical fibers were also used. This needle is hollow. Liquid grease may circulate inside the needle. The back end of the needle m. B. connected to the lubricant reservoir, and the front one is equipped with either a closed removable tip during separation operations, when this needle is translationally moving in the cable channel, or lubricating - during the cable pulling operation. This needle is a tube of composite material enclosed in an outer sheath and containing an inner tube of a sealing coating. This design is realized by extruding and stretching a composite material based on fiberglass in an epoxy matrix on a tube of thermoplastic material, which in this case becomes a tube of the inner coating for sealing. The system obtained in this way is coated externally with a small coefficient. friction. The hollow needle functions as a nozzle and lubrication tip and provides for the dispersion of lubricant immediately before the drawn end of the cable

From topological charge information to a set of solitons

From topological charge information to a set of solitons in a quadratic nonlinear medium.

The principle of operation of a new class of optical devices operating in a quadratic nonlinear medium is described.

Types of solitons and soliton waves.

Trends in the development of communications networks on optical fibers in the United States.

An extremely rapid growth in the market for fiber-optic communication networks in the USA is noted. The pace of development of new technologies is such that industry lags significantly behind. A similar trend persists both in the field of creating long-distance communication systems and in the field of local communication networks. Among the long-distance communication systems, the creation of a fiber-optic communication network for the states of the Midwest with the length of long-distance communication paths> 20 thousand km, communication paths within cities> 8 thousand km is noted.
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Firm Lucent's Technologies'produces new types of optical fibers with high throughput for local fiber-optic communication networks. It is noted that many fiber-optic communication networks in the present. time reached 85% of throughput and expand on average by 20% per year. A characteristic trend is the emergence of a large number of small and medium-sized firms, which often merge.

Multifunctional fiber optic microwave lines .

The results of the experiment are presented. studies of the multifunctionality of microwave FOCLs based on remote heterodyne detection of signals from a two-frequency laser transmitter. Using heterodyne detection instead of direct detection can significantly improve line performance, such as modulation, frequency conversion, signal recovery, and transmission. Various detection methods and a FOCL scheme with remote heterodyne detection are considered.

Completion of the Japanese Information Highway

The completion of the Japanese Information Highway is reported, which is a system of optical cables laid along the bottom of the sea connecting 17 ground-based communication centers, each of which is also connected to optical cables laid on the islands of the Japanese archipelago (Hokkaido, Honshu, Kyushu, Shikoku.) The Japanese information highway operates in the mode of wavelength division multiplexing, each channel has 14 channels. The information transfer rate per channel is 2.5 Gbytes / s. The description of the backup system. The construction was carried out by the information highway HDD, which completed the development of a prototype of a new generation of fiber-optic communication systems using solitons (information transfer speed at a distance of 10,000 km 40 Gbit / s).

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Mode coupling in single-mode spiral fibers in the presence of perturbations.

Experimental results are given. investigation of the coupling of modes in spiral optical single-mode fibers with a circular cross-section in the presence of perturbations. Equations of coupled modes for these fibers are derived and compared with similar equations for std. fibers. The transmission characteristics for spiral fibers with a round core are obtained. The results of the numerical analysis show that the ellipticity of modes and birefringence increases with an increase in the ellipticity of the fiber core.

integro-differential equations for the description of modes in channel waveguides with uniaxial anisotropy

The system of integrodifferential is formulated. equations for 2 transverse components of magn. and longitudinal components el. fields, which allows us to describe both guided and leaky modes of inhomogeneous channel waveguides characterized by a diagonal complex tensor. permeability.


Dispersion properties of the modes of chiral planar optical waveguides

An analytical study of the dispersion properties of the modes of chiral planar optical waveguides: symmetric and asymmetric. It is shown that all modes have circular polarization, while they are divided into 2 classes: with right and left polarizations; modes of one class, depending on the sign of the chiral parameter of the medium of the waveguide layer, can exist only in a limited frequency range, i.e. have critical frequencies in both the lower and upper parts of the frequency range. Graphs of the dispersion characteristics of the modes are presented, illustrating these new results.

Laying fiber optic cables directly into the ground

Using specialized mechanisms, a micro trench is made in the roadbed with a width of up to 15 mm and a depth of 40 to 100 mm, into which a specialized fiber-optic cable is laid. The laid cable is covered with a porous rubber tow, the diameter of the tow is selected so that it fits snugly into the trench and serves as a spacer. After this, the trench is poured with bitumen.

The cable designed for this installation method is a monotube design and consists of one metal module made of a copper alloy, inside of which optical fibers are contained. The interior of the fiber module is filled with a hydrophobic compound. The external diameter of the module is 5 mm. The module contains bundles of optical fibers. For identification, the optical fibers in one bundle have a different color, and each bundle has a winding of colored synthetic filaments. The number of optical fibers in the beam is up to 12 pieces. A cable can contain up to 5 bundles of optical fibers. Thus, the number of optical fibers in the cable can reach sixty. Outside the cable is covered with a protective polyethylene sheath. The outer diameter of the cable is 7 mm, weight - about 110 kg/km.

Fiber optic cable for micro trench installation

This design of the fiber optic cable provides high resistance to temperature fluctuations and mechanical stress. Permissible tensile strength is 1 kN. The permissible bending radius when laying is 70 mm. Operating temperature range - from -40 to + 70 ° С.

It should be noted that, as in the case with other fiber-optic cables, installation work should be carried out at an ambient temperature of at least -5 ° C.

To join the building lengths of the fiber-optic cable, special couplings have been developed, designed to be installed on the soil surface so that the coupling hatch is flush with the road surface. These are couplings of the type through the passage. The round case is made of stainless steel and is designed for splicing up to two cable construction lengths, that is, it has 4 cable entries. There are modifications of couplings for splicing fiber optic cables of various capacities. The clutch case has a round shape, the diameter is calculated in such a way as to enable the calculation of the technological stock of optical fibers inside the clutch case.

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FOCL: types of optical fibers

The optical fibers used to construct the fiber optic link differ in the material of manufacture and in the mode structure of light. As for the material, there are distinguished all-glass fibers (with a glass core and a glass optical sheath), all-plastic fibers (with a plastic core and a sheath) and combined models (with a glass core and a plastic sheath). Glass fibers provide the best throughput; a cheaper plastic option is used if the requirements for attenuation and throughput are not critical.

By the type of paths that light travels in the fiber core, single and multimode fibers are distinguished (in the first case, one beam of light propagates, in the second - several: tens, hundreds and even thousands).

• Single-mode fibers (SM) are characterized by a small core diameter through which only one beam of light can pass.
• Multimode fibers (MM) are distinguished by a large core diameter and can be with a stepped or gradient profile. In the first case, the light beams (modes) diverge along different paths and therefore come to the end of the fiber at different times. With a gradient profile, the time delays of various rays almost completely disappear, and the modes go smoothly due to a change in the speed of light propagation along wave-like spirals.

All modern works (both single and multi-mode), with which data lines are created, have the same outer diameter - 125 microns. The thickness of the primary protective buffer coating is 250 μm. The thickness of the secondary buffer coating is 900 microns (used to protect connecting cords and internal cables). The sheath of multi-fiber cables is painted in various colors (for each fiber) for convenience.

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FOA International Certifications - ETA

FOA International Certifications - ETA
The importance of our International Certification courses lies fundamentally in that they are elaborated to world standards, without brand sponsorship, being able to achieve accreditation and validity thus allowing employability anywhere in the world.

FOA - The Fiber Optic Association, USA
It is a nonprofit professional organization oriented to the fiber optic technology industry. Its main function is the development of educational programs, pass training courses and certification of Optical Fiber, participate in the processes of elaboration of standards together with the main organizations of industry standards and the general promotion of Fiber Optic technology. The FOA has developed guidelines for the approval of Certified Schools that meet FOA standards.

A School certified by FOA and offering certifications in CFOT® Fiber Optics, CPCS and CFOS, complies with FOA training standards and is authorized to offer certifications. METACOM® Technology Training Center has been approved as a Fiber Optic School that meets FOA standards to offer Fiber Optic Certifications and has a staff of Engineers who have been certified as CFOS / I, accrediting them as Fiber Optic Instructors.

ETA International ® - Electronic Technician Association, USA
Professional association founded in 1978 in the United States, representative of the electronics industry, including its professionals, educators, and corporate institutions. Its main function is the development of educational, neutral training and certification programs accredited by ICAC - International Certification Accreditation Council, forming more than 150,000 certified professionals in more than 80 programs in a variety of fields technology. Professionals certified by ETA International today work for companies such as Google, ESPN, Motorola, and the United States Armed Forces.
CET METACOM® has been approved as an ETA International® School that meets its standards to offer certifications in various technologies, and has a staff of Engineers who have been certified as Instructors by the Association.