Telecommunications applications

The bulk of plastics materials are required to operate within the range of -30 to + 100°C. There has, however, been a steadily increasing demand for materials to operate outside of these ranges, particularly in certain aerospace, military and telecommunications applications. A considerable amount of research work has been carried out in response to this demand and many thousands of polymers, both organic and inorganic, have been prepared. Many of those which have achieved commercial use have been considered in earlier chapters but in the final part of this chapter it is intended to review the overall situation. 

Silicon photodiodes exhibit maximum sensitivity at about 800 nm and they can be used in the whole visible range however their sensitivity drops by several times at the blue region. Special structures can be made with enhanced blue sensitivity (so-called blue or UV diodes). Germanium photodiodes are capable to detect radiation from 600 nm up to 1700 nm. In telecommunication applications InGaAs elements are widely used. 

The NFPA Research Foundation, in a collaborative project with the DOE and the telecommunications industry, completed a draft report on diffusion of hydrogen leaks from cabinet-enclosed hydrogen storage tanks. The purpose of this research is to establish a better scientific foundation for setback requirements for hydrogen fuel cell systems used in telecommunication applications. 

The laboratory-to-laboratory reproducibility of the isothermal oxidative stability procedure for measuring the oxidative stability of polyolefin insulation used in telecommunications applications has been improved from approximately 45% to approximately 85%. The improved protocol is described in some detail. 12 refs. 

The actual power loss in a dielectric in an AC field is proportional to the loss factor, i.e. the product of permittivity and power factor, so that to achieve the minimum loss both of these parameters must be small. Power loss is also proportional to frequency so that at high frequencies, for example in telecommunications applications, it may be especially necessary to use low permittivity and low loss materials. For making capacitors, a high permittivity is desirable because then the physical size of the component for a given capacitance can be as small as possible. A high loss is not normally wanted in a capacitor so that the ideal dielectric would have a high permittivity and a low power factor. A high loss factor may be desirable... 

Telecommunication stations based in non-interconnected to the grid areas are a promising market segment for autonomous hydrogen power systems. The power demand of such stations ranges from some Watts in the case of minimal stations to 10 kW for mobile-phone relay stations. In telecommunication applications only DC loads are usually served by the installed power system. 

Also, the organic compounds show, in the semiconducting and insulator phases, very interesting properties, especially optical ones, which are fully analysed and exploited for themselves, for instance in the telecommunication applications of active fiber optics. 

In some applications, where it is necessary to protect the batteries from heat via solar radiation (e.g., PV systems), passive-cooling systems can be used (Fig. 8.29). An example of a passive-cooling system in telecommunications applications is described in Ref. [36]. This design reduces the elfects of heating by direct solar radiation and by heat generated inside the housing. Additionally, the batteries are protected against other effects of the environment. 

Lead-acid batteries were first used in stationary, stand-by applications more than 130 years ago [1]. For a long period of time, only flooded lead-acid batteries were used. Nowadays, UPS and telecommunications applications use valve-regulated batteries. Large, utility-scale applications such as load levelling continue to use flooded batteries, but it seems that, increasingly, valve-regulated batteries are chosen even for these applications. 

Sonnenschein was the first company to introduce gel battery technology to the market successfully. They started in 1958 with rather small batteries for flashlights. Since that time, this technology has steadily replaced the conventional, flooded lead-acid battery in various applications [38,71,72]. Phosphoric acid addition for cycling was first introduced in 1965. Larger gel batteries with tubular positive plates were developed for stationary applications in 1978. More recently, gel batteries have been produced for starter and traction applications, and thick, flat positive plates were added for telecommunications applications. 

Since the electrolyte is immobilised as a gel, the cells can also be placed in the horizontal position without any risk of add leakage. A 48-V, 1000-Ah, lead-acid battery with gel cells, positioned horizontally for a telecommunications application, is shown in Fig. 13.8. 

Fig. 13.8. Stationary, 48-V, 1000-Ah battery with OPzV, A600-type gel cells for telecommunications application in a horizontal position.

Gel batteries are also produced in 6-V and 12-V monoblocs with capacities between 5 and 180 Ah. These are also mainly used for telecommunications applications. They have flat positive plates, and provide a service-life of more than 12 years. The results of an accelerated life test of 12-V, 16-Ah batteries at 40°C and a float voltage of 2.22-V per cell are shown in Fig. 13.9. It can be seen that the capacity decreased below the 80% level after about 35 months and reached 50% after about 40 months. This equates to an expected life of more than 12 years at 20°C. The influence of discharge rate and temperature on the available capacity is shown in Fig. 13.10. Most of the applications of this battery-type require discharge currents between 1 and 4 times the 10-h discharge rate. Therefore, this battery-type has been optimized to a high energy density for discharge times between 10 and 2h. 

Fig. 13.14. 12-V, 100-Ah AGM battery (Marathon-type) with front terminals for telecommunications applications.

In summary, it seems that there is a rapidly increasing market for large batteries in a variety of utility applications. So far, this has mainly been a market for flooded batteries, but it is likely that the valve-regulated battery can replace the flooded battery in utility applications in the same way that it has replaced them in UPS and telecommunications applications. 

Because of basic optical principles, the light injected into the fiber must belong to a geometrical acceptance cone in order to be guided within the core. This condition is given by the numerical aperture, defined as NA = sint ni = ( i — with 0, the maximum angle of the cone, and n and 2 the refractive indices of the core and cladding, respectively. Numerical apertures are usually between 0.1 and 0.3 for telecommunication applications, with the refractive index of pure silica equal to 1.4586 at sodium D-line. 

The Telecommunication Development Sector (ITU-D), a UN body advising nations on telecommunication development, has been researching technological developments that have the potential to support telecommunication applications that are commercially viable or sustainable through other transparent financing mechanisms in rural and remote areas of developing countries that exhibit the following[2] ... 

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