【正文】 Equaliser CPLR CPLR High Pass Low Pass Signal Director BASIC TWO WAY AMPLIFIER with BRIDGER 18 Cisco Systems Confidential Up Converter / Optical Node Frequency Synthesizer ATT IF RF Upconverter Optical Node Optical Electrical Diplexer 19 Cisco Systems Confidential COAXIAL CABLE TRANSMISSION SYSTEMS COMMON EQUIPMENT AND APPLICATIONS AMPLIFIER (FORWARD) AMPLIFIER ( TWO WAY) INPUT + 12 dBmV INPUT + 12dBmV OUTPUT + 34 dBmV OUTPUT + 34 dBmV CABLE LOSS 22dB GAIN + 22 dB GAIN + 22 dB CABLE LOSS 22dB DOWN STREAM DOWN STREAM UP STREAM ONE WAY TRANSMISSION TWO WAY TRANSMISSION 20 Cisco Systems Confidential COAXIAL CABLE TRANSMISSION SYSTEMS AFFECTS OF TEMPERATURE and COUNTERMEASURE LOSS (dB) TEMPERATURE (deg F) relative to reference frequency AGC (Autmatic Gain Control ) is the countermeasure Output signal is sampled, and fed back to the input of the amplifier to pensate for temperature, and to maintain a constant output. AGC functionality is distributed when needed to achieve stability at minimal cost. DISTRIBUTION OF AGC FUNCTION AMP 1 (AGC) AMP 2 (MAN) AMP 3 (MAN) AMP 4 (AGC) TEMP OUT CABLE IN OUT CABLE IN OUT CABLE IN OUT deg F PUT LOSS PUT PUT LOSS PUT PUT LOSS PUT PUT +90 +40 + + + + + +40 +68 +40 + + + +40..0 + +40 +0 +40 + + + + 29. + +40 21 Cisco Systems Confidential COAXIAL CABLE TRANSMISSION SYSTEMS ESTABLISHING SIGNAL LEVELS +18 +40 100 Ft TAP 600Ft TAP 500 Ft TAP dBmV dBmV 1 dB (2/29) 6 dB (2/20) 5 dB (2/17) DROP LEVEL +10 dBmV + dBmV +10 dBmV DROP LOSS 100 Ft 1 dB 100 Ft 1 dB 100 Ft 1 dB DEVICE / CABLE INSERT LOSS/GAIN OUTPUT LEVEL DROP LEVEL AMPLIFIER + 40 dBmV 100 Ft .500 CABLE 1 dB + 39 dBmV 2 / 29 TAP .4 dB + dBmV +10 dBmV 600 Ft .500 Cable 6 dB + dBmV 2 / 20 TAP .6 dB +32 dBmV + dBmV 500 Ft .500 CABLE 5 dB +27 dBmV 2 / 17 TAP .7 dB + dBmV +10 dBmV (+9 dBmV) (+ dBmV) (+9 dBmV) 22 Cisco Systems Confidential HFC (Hybrid Fiber Coaxial) Technology Coaxial Cable Network 2022 HOMES COAX Headend Coaxial Cable ? Bypass and eliminate coaxial cable and amplifiers from a portion of the downstream path and replace the link with fiber ? Make ready for two way operation! 23 Cisco Systems Confidential NODE N Cable Serving Area Typically Fewer than Five Amplifiers in Cascade HFC Cable Network ? The video signal is transmitted over fiber to the node, where it is converted to an electrical signal and forwarded to the subscriber over existing coaxial cable ? Provision is made to support return traffic for future services 2022 HOMES Headend COAX Fiber HFC (Hybrid Fiber Coaxial) Technology 24 Cisco Systems Confidential CABLE SYSTEM TOPOLOGY (optical node) TO / FROM HEAD END TYPICALLY FEWER THAN FIVE AMPLIFIERS IN CASCADE TYPICALLY 125 TO 2022 HOMES SUPPORTED BY ONE NODE 25 Cisco Systems Confidential 80 Channels CNN HBO ESPN ? Smaller, robust serving areas: HFC to the node Alternate feed to the node Target nodes of 500 homes Fewer amplifiers Cable Network COAX Drop Settop TV Alternate Feed Reliability, Increased Access Bandwidth Hub HFC (Hybrid Fiber Coaxial) Technology 26 Presentation_ID 169。 1999, Cisco Systems, Inc. Module 2 CATV and RF Technology Overview 6 Cisco Systems Confidential Terms ? CATV Community Antenna TV ? NTSC National Television Systems Committee: . TV technical standard, named after the anization that created it in 1941. Uses a 6 MHz wide modulated signal ? PAL Phase Alternating Line. The TV system used in most of Europe and many other places, in which the color carrier phase definition changes in alternate scan lines. Utilizes an 8 MHz wide modulated signal ? SECAM TV system used in France and some former Soviet bloc countries. Utilizes an 8 MHz wide modulated Signal. ? Spectrum Reuse CATV’s most fundamental concept is spectrum reuse. Historically, the overtheair spectrum has been assigned to many other purposes. Much of it is therefore not available for the carriage of TV. The result is an inadequate supply of spectrum to serve viewers needs. Cable can reuse spectrum that is sealed in its aluminum tubes. ? Coaxial Cable The principal physical media over which CATV systems are built. The main drawback of Coax Cable is it’s relatively high loss. Coax sign