ATIS 0600331-2015 Description of Above-Baseline Physical Threats to Telecommunications Links.pdf

1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0600331.2015 Description of Above-Baseline Physical Threats to Telecommunications Links As a leading technology and solutions development organization, the Alliance for Telecommunications Industry Solutions (ATIS) brings together the top global

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11、ve current information on all standards by calling or writing the American National Standards Institute. Notice of Disclaimer AM broadcast, television, FM broadcast, and radar. The effects of EMI range from audible noise on the link (e.g., audio rectification in an operated surge protector) to shutt

12、ing down high-capacity service (e.g., many bit errors in an optical repeater). Another EMI threat to telecommunications links is caused by broadband electromagnetic sources. Examples of broadband sources are electric motors, combustion engines, and electrostatic discharges. These sources generate br

13、oadband emissions because of the impulsive nature of the signals. 6.2.1 Narrowband Electric Fields Narrowband electric field sources are those with radiating frequencies between 10 kHz and 10 GHz. These fields include a mixture of emissions from licensed transmitters (e.g., AM and FM broadcast, tele

14、vision, amateur radio, and police/emergency communications). Field strengths of 15.3 V/m may be present at some locations, for example, 140 meters from a 50 kW nondirectional AM broadcast transmitter antenna or 94 meters in front of an 8 dB gain amateur antenna fed with 1.5 kW peak envelope power. T

15、he above-baseline threat level from narrowband electric fields is greater than 15.3 V/m in the range of 10 kHz to 10 GHz. The maximum permissible transmission power for new AM broadcast stations is 50 kW; for FM broadcast stations, 100 kW; and for TV broadcast stations and commercial radar, 5 MW. Th

16、e maximum permissible transmission power for amateur radio stations is 1.50 kW. It should be noted that these values are the input power to the antenna and not the Effective Radiated Power (ERP) in the main beam of the antenna. The ERP can be larger because it includes the antenna gain. See Annex E

17、for added information. ATIS-0600331.2015 5 The increased usage of portable transmitters (e.g., cellular telephone, VHF business band, and Personal Communication Services PCS) is also a threat to the telecommunication links. Although these are low-power transmitters, the electromagnetic fields close

18、to one of these transmitters are considerable, since field magnitude is inversely proportional to the square of the distance. Collocated ancillary electronic equipment may be a source of EMI to electronic telecommunications link equipment. This ancillary equipment may be located within one meter in

19、front or back of the telecommunications link, or worse, adjacent. The increased density of electronic equipment (nonintentional radiators) near telecommunications links and intentional radiators (e.g., broadcast radio stations) in the vicinity of telecommunications links augment the electromagnetic

20、field strength incident on telecommunications links. The electromagnetic waves generated by the above-mentioned sources can cause EMI to electronic telecommunication link equipment (e.g., digital/optical repeaters, optical network units, multiplexers/demultiplexers). The interference may range from

21、audible noise (broadcast demodulation) on voiceband leads to the shutting down of repeaters. Audio demodulation may occur at operated carbon block protectors in the telecommunication links. A T1 repeater may be completely incapacitated by EMI that causes it to receive, or perceive to receive, excess

22、ive bit errors in a short period of time. 6.2.2 Broadband Fields Examples of sources of broadband interference include combustion engines, electric motors, faulty power line insulators, and electrostatic discharges. Electrostatic Discharges (ESD) are considered broadband events with energy distribut

23、ed in the frequency range 10 MHz to 10 GHz. Broadband interference, generated by sparking, typically has most of its emissions centered between 400 MHz and 500 MHz. Telecommunications links equipment designs tested to ESD limits of 8 kV for contact discharges and 15 kV for air discharges rarely expe

24、rience ESD interference. Therefore, the above-baseline threat level from ESD shall be 8 kV for a contact discharge and 15 kV for an air discharge. Interference to telecommunications links equipment can be difficult to predict because of unrestricted use and location of broadband interference sources

25、. Repeaters for digital carrier systems commonly are located at the base of a wooden pole, in a pedestal, or in a busy commercial or residential area, where they may be exposed to broadband interference from nearby power tools, gasoline engines, or electrostatic discharges. Such broadband interferen

26、ce can have a large effect on digital equipment, since a spark (a broadband signal source) can be interpreted by the digital equipment as the leading edge of a bit. ATIS-0600331.2015 6 Annex A List of Acronyms (informative) ANSI American National Standards Institute ASCE American Society of Civil En

27、gineers EIA Electronic Industries Alliance EMI Electromagnetic Interference ERP Effective Radiated Power ESD Electrostatic Discharge HEMP High-Altitude Electromagnetic Pulse PCS Personal Communications Services ATIS-0600331.2015 7 Annex B Typical Telecommunications Links (informative) Typical teleco

28、mmunications links are depicted in the diagram below. This figure is reproduced from ATIS-0600328. Please see the latest revision of that document. ATIS-0600331.2015 8 Annex C Additional Above-baseline Threats (informative) The additional threats discussed here are considered to be above-baseline th

29、reats, but do not have identified levels that are at the upper limit of reasonable probability. When these upper limits are quantified, these threats may be included in subsequent revisions of this standard. C.1 Liquid Penetration in Cables C.1.1 Optical Fiber Cables C.1.1.1 Water It has been well d

30、ocumented that the concentration (or more precisely the thermodynamic activity) of liquid water or water vapor on the surface of silica (light guide) fibers is the critical agent controlling their mechanical degradation with or without stress. Studies of such degradation over normal ranges of temper

31、ature (25C to 100C) and concentration (liquid water to water vapor at 1 atmosphere of pressure) have shown that at a given water concentration, the temperature dependence is well-behaved and is controlled by the energy necessary for the water to break the silicon-oxygen bond (80 kJ/m). Thus, the beh

32、avior in this temperature and pressure range is predictable. An above-baseline threat shall be water on the surface of light guide fibers outside the normal ranges of temperature and pressure given above. C.1.1.2 Aqueous Solutions Very little detailed work has been done on other aqueous liquids whic

33、h are expected to be more aggressive than water, e.g., ammonia (NH4OH) or other household cleaners (chlorine bleach), as well as petroleum products (gasoline, kerosene, etc.). In some cases extreme optical or mechanical degradation can occur, especially with ammonia. However, upon drying with time,

34、the ammonia is desorbed from the glass surface and some amount of the strength is regained. C.1.2 Copper-Conductor Cables There is no above-baseline threat defined for liquid penetration in copper-conductor cables. C.2 Temperature, Temperature Cycling, Humidity C.2.1 Exposure to High Temperatures An

35、 above-baseline high-temperature exposure threat to lightguide fibers shall be temperatures above 100C. The mechanical degradation behavior of lightguide fibers in the presence of water can be predicted at temperatures below 100C. It is assumed that the relations applied below this temperature will

36、continue to be valid above 100C and thus the prediction is that the water will continue to become more aggressive (exponentially) with increase in temperature at a constant water activity. The critical issue then becomes one of the stability of the polymer coating. Most commonly used coatings will s

37、often and/or degrade rapidly above 100C, thus leaving the fiber unprotected. In cases where such temperatures are possible, alternate coatings should be employed. C.3 Exposure to fire The above-baseline threat from fire external to the links structure is fires from both man-made and natural sources

38、with heat release rates above 10 MW. The basic assumption is that the link elements under threat are not at the source of these fires. Examples of such fires are: Forest fires. Flammable liquid fires from fuel spills, vehicular crashes, etc. ATIS-0600331.2015 9 Flammable gas fires from pipeline brea

39、ks, trucks, railroad tanker cars, etc. Adjacent building fires. The above-baseline threat from fires internal to the links structure is fires with a heat release rate of approximately 50 kW to 100 kW in the area of origin. An example of this threat is a self-sustaining fire in the cables in a cable

40、entrance facility. C.4 Wind in addition to the southern and eastern portions of Virginia; the areas of Michigan and southeastern Wisconsin south of 43 30 north latitude; the coastal strip of Maine; the areas of New Hampshire and Vermont south of 45 north latitude; and the areas of western New York s

41、outh of 43 30 north latitude and eastern New York south of 45 north latitude. In addition, Zone I-A (FM only) consists of all of California south of 40 north latitude, Puerto Rico and the U.S. Virgin Islands. (If the dividing line between Zones I and II runs through a city, that city is considered t

42、o be in Zone I.) Zones I and I-A have the most “grandfathered“ overpowered stations, which are allowed the same extended coverage areas that they had before the zones were established. One of the most powerful of these stations is WBCT in Grand Rapids, Michigan, which operates at 320,000 watts and 2

43、38 meters (781 ft) HAAT. Zone III (the zone with the flattest terrain) consists of all of Florida and the areas of Alabama, Georgia, Louisiana, Mississippi, and Texas within approximately 241.4 kilometers (150 miles) of the Gulf of Mexico. Zone II is all the rest of the Continental United States, Alaska and Hawaii.