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1、 Hybrid Fiber Coax HFC and Dense Wavelength Division Multiplexing DWDM Networks Definition The latest generation of optoelectronics products provides a major increase in the capacity of hybrid fiber coax HFC networks allowing the delivery of new interactive video data and voice services This tutoria
2、l summarizes the capabilities of these products and discusses methods of successful implementation Overview As cable and telecommunications operators strive to introduce new services they must find new ways to increase their network capacities at a reasonable cost An excellent solution to this dilem
3、ma is the implementation of optoelectronics in HFC systems Optoelectronics is having a tremendous impact on the evolution of the HFC networks required for high volume interactive multimedia traffic The introduction of this technology enables networks originally designed for video services to provide
4、 reliable bandwidth for all types of interactive video data and voice services Optoelectronic technology allows operators to drive fiber deep into the network more effectively make better use of existing bandwidth economically increase bandwidth and target programming to specific areas Most importan
5、t optoelectronics enable the efficient delivery of many revenue generating interactive services which can make operators more profitable and competitive In addition the larger telecom industry can cost effectively overlay video on fiber in the loop FITL architectures efficiently carry analog video o
6、n synchronous optical network SONET backbones and solve the power challenge the dense wave division multiplexing DWDM deployments impose on optical amplifiers in the long haul network Both the computer and telecommunications industries have shown a great deal of recent interest in HFC networks as th
7、e pending AT it cannot monitor the video performance Consequently many broadband operators install two networks a SONET system for voice and data and an analog or proprietary digital system for video From both an architectural and operational perspective this is not an optimal solution To address th
8、is essential transport issue a video optimized OC 48 SONET multiplexer has been developed see Figure 11 Video optimized input output I O devices take analog video channels in various formats and map them directly in STS 3 slots in the SONET payload This lets the operator carry analog video in an unc
9、ompressed high performance manner while maintaining all the benefits of SONET for duplex services such as voice and data To encode the video the operator can use 10 bit samples and map both baseband and IF video signals scrambled or clear channel This technology allows building a true Web ProForum T
10、utorials http www iec org Copyright The International Engineering Consortium 13 21 multimedia backbone in which a single pair of fibers carries a full range of video voice and data services Eliminating service specific architectures creates the flexibility needed to cope with the uncertainty inheren
11、t in new service rollouts Figure 11 A Video Optimized OC 48 SONET Multiplexer One drawback of carrying uncompressed analog video signals digitally is the large amount of bandwidth needed 16 analog channels occupy an entire OC 48 To address this DWDM is used to combine up to eight systems on a single
12、 fiber This combination enables the transport of 80 analog video channels and several hundred digital video streams while maintaining 5 gigabits for voice and data services 9 Using the Analog Network for Interactive Traffic The existing analog transport network can also play a role in carrying inter
13、active traffic For video on demand for example a typical hub may need to receive several hundred digital streams to meet the traffic requirements for 20 percent or 30 percent penetration To deliver this amount of bandwidth up to eight 1550 transmitters each carrying 200 MHz of QAM loading can be mul
14、tiplexed onto a single fiber and combined at the hub with the broadcast signal see Figure 12 Depending on architectures chosen either externally modulated or directly modulated transmitters may be Web ProForum Tutorials http www iec org Copyright The International Engineering Consortium 14 21 used T
15、his technology is also being used in the upstream direction to carry reverse path signals from hubs to head ends Figure 12 Using the Analog Network for Interactive Traffic In the longer term systems will need to carry over the same fiber not only multiple wavelengths of baseband digital but also mul
16、tiple QAM channels and an analog tier as well In this way backbone metropolitan area networks MANs can be constructed to meet the transport goal of efficient connectivity of multimedia services in multiple formats avoiding unnecessary conversion and processing costs whenever possible 10 Conclusion Optical technology enables providers to achieve the goal of building powerful multimedia networks capable of handling high volume interactive services cost effectively High power 1550 technology video
