Approach of an era of optical processing techniques

Evgenie Rudometov

Optical cables are characterised by very high metrics of information capacity, reserve and the noninterference, unavailable to radio channels and traditional wire lines. Implementation of the specified advantages specialised hardware-software resources, for example, provide products Cisco

In the course of the evolution computers have rather fast transited path from the big computing monsters to compact personal desktop arrangements. Thanks to perfection of processing techniques and architectures their computing power promptly increased, often overtaking forecasts of the known empirical law of Moore. Also functionality of personal computers (PC) that has provided the extension of consumer properties and implementation of many before unavailable possibilities in a parallel way grew.

However, despite all it, there were the tasks which are not subject to single PCs. It has demanded multiplexing of computers in a network of different level of complexity. Appearance of networks has provided not only the extension of a spectrum of solved tasks, but also more optimal maintenance of the equipment at the expense of municipal usage of accessible hardware-software resources.

There are the different patterns of networks differing both topology, and technical parametres. However all solutions are banked by that for informational interconnection of computers communication circuits use. They provide high-speed transmission of figures between arrangements. Thus the information can be handled or wireless way, or by means of cables.

Despite perspectivity and convenience of a wireless information transfer, the majority of networks now is under construction by means of wire communication circuits. It concerns also local area networks with rather small number of computers – units, tens or hundreds arrangements, and global where the quantity of computers, is quite often calculated already by millions. And it is finite, for high-speed transmission of the big streams of the information appropriate transmission lines of data are required also.

Before recent time computers were jointed in a network exclusively by means of the cables created on the basis of metal explorers: coaxial and-or twisted pairs. At all advantages of these variants it is necessary to mark, that they already far not always correspond to fast increasing requirements. First of all, it concerns the pass-bands which necessity of increase is dictated by prompt growth of productivity of computers.

Alas, for traditional metal explorers possibility of increase in a pass-band is limited by physical laws. Really, with attempts to increase the given parametre the problems linked to influence of capacity and inductive properties of lines which distort the form of handled digital signals increase. Besides, it is impossible to dump about scores and inevitable losses in lines. The part from them is linked to an active component, and a part - with emanation. In addition to all problems also the prices for nonferrous metals used in cables permanently grow.

Of the specified lacks the fiber-optical lines representing, as a matter of fact, dielectric wave guides, created on the basis of thin threads of quartz glass — amorphous modification of oxide of silicon are deprived many . In them the information transfer is carried out by means of light signals of a microwave wave band: the infra-red band with length of waves from 0,8 to 1,6 microns usually uses.

The fiber optics has received today wide development and is applied in various areas of a science and engineering. Optical fiber production is estimated already in millions kilometres. Rates of growth of fiber optics and optoelectronics in the world market anticipate many other things branches of engineering and reach 40 % a year.

Optical cables form on the basis of the quartz glass alloyed by special additives in which quality rare-earth units and their interconnections usually are applied. Such cables possess many advantages. Major of them concern: broadbandness that means possibility of transmission of the big streams of the information; small losses and, accordingly, the big lengths of sites without usage of additional amplifiers; small values of diameter of cables and their weight (1 km svetovolokna without the protective shell has weight 40); security from external actions and a crosstalk; high reserve of an information transfer; a galvanic isolation of units of a network; absence of an arc drawing and short circuit in cables.

The enumerated advantages became a consequence of changeover of a current flow in the metal wires used for an information transfer, on light in special cables. It is necessary to add, current technologies provide reception of photofiber of very high transparency: in a loss working range can be less than 0,1 db on km.

To estimate revolutionism of the given transition, it is enough to recollect, that light represents electromagnetic oscillations of very high frequency, by the way, much bolshej, than in case of habitual radio. This circumstance provides very high information capacity of optical channels unavailable to other resources, including radio-waves and even traditional wire lines. And it is real, metrics of capacity of optical channels already today on usages above, than for the informational lines constructed on the basis of copper cables.

And still the optical fiber is unreceptive to electromagnetic fields that removes some typical problems of copper communication systems. Here and the reserve following from practical impossibility of interception in optical channels of the transferred information, and their noninterference eliminating deformation of handled signals.

Today optical networks are capable to handle a signal to the big distances with the extremely insignificant losses, by the way, much smaller, than in case of traditional wire solutions.

However, in spite of the fact that this processing technique remains while rather not cheap, the prices for optical components fast decrease, while possibilities of copper lines come nearer to the limiting values and demand the increasing expenses for further development of this direction. With the registration of pass-bands optical cables already are quite competitive today, though demand certain modification of a network infrastructure.

In optical systems of transmission the same methods of derivation of multi-channel link, as in usual systems of transmission on an electrical cable are applied. The fulfilled methods of frequency and time sharing of channels treat them kindly. In all cases of an optical information transfer modulation of the optical carrying is provided. And already in the promodulated sort the light signal is handled on the optical channel, providing transmission of huge streams of the information.

Understanding perspectivity of the optical processing techniques, many companies carry on the intensive researches linked to their development. Implementation of the received results become appropriate production.

As an example it is possible to result optical transmission media of data of company Cisco which are the recognised world leader in the field of network processing techniques. Recently this company has presented the next products concerning construction of DWDM-networks on the market. Here it is necessary to remind, that DWDM means Dense Wavelength Division Multiplexing — spectral channelizing. The processing technique is grounded on usage of light waves of various length. It provides multiplexing and data transfer on the optical channel of several signals from different sources. Thus each signal is handled on the wavelength therefore on one optical fiber it can be handled more than 1000 trunks. It is necessary to add, that in cables than ten standard veins of an optical fiber can use more.

Multiservice transport platform Cisco ONS is put in a basis of new solutions of DWDM-networks 15454 MSTP. This platform uses the newest optical amplifiers, multiplexers and recustomized transponders (transponder from transmitter-responder — the transmitter-respondent).

Among shared units it is necessary to mark the 40-channel customised optical mesh-multiplexer of input/output (ROADM — Reconfigurable Optical Add-Drop Multiplexer), supporting from 2 to 8 directions in DWDM-system, maps Ethernet Xponder and system of multiservice aggregation SONET/SDH on the basis of map MSPP-on-a-Blade. Cisco Mesh ROADM provides transition from linear and ring networks DWDM to more effective polnosvjaznym (Mesh) to optical networks DWDM at simultaneous simplification of handle, activation of services and diagnostics. Cisco Ethernet Xponder allows to aggregate streams Ethernet with speeds from 1 Mbit/with to 1 Gbit/with in optical channels 10Gbit/with. Thus, according to experts Cisco, the company has the resources providing transmission on each fiber optic pair to 32 channels on 10 Gbit/with, that much more traditional 1 Gbit on a twisted pair.

Certainly, the enumerated products make only small part of optical products of company Cisco offering to customers completed network solutions. Some of the most interesting hardware-software resources will be described in following articles.