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发表于 2008-1-25 20:09:35
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FIBER TO THE HOME Paul E. Green John Wiley & Sons Foreword The promise of fiber communications has not been realized either in the long-haul backbone network or in the last mile access network. Considerable discussion has taken place regarding the failure of the former, the most compelling explanation being the bursting of the dot.com bubble which drastically reduced the growth of traffic in the backbone and produced a devastating effect on the telecomm industry. Capital for broadband in the backbone dried up rapidly at the turn of this century. More complex reasons exist that fiber to the home (FTTH) has not taken off in the past. In this book, Paul Green examines this issue and provides an in depth treatment of the drivers that are now emerging which will likely spur dramatic increases in FTTH deployment (already the early signs are there) as a strong alternative to the existing broadband access technologies of copper (DSL) and coax (cable modems). He makes the effective, and common, argument that today’s move toward multimedia streams into the home (in addition to voice and data, the three together forming the holy grail of the “triple play”) is driving the demand for broadband access to homes (as well as other end–user premises). Green minimizes the value of copper and coax as a sustainable solution while at the same time arguing that fiber is future proof, and hence the correct solution. The influence of the common carriers, especially in the United States, on the continued push for DSL and of the cable operators on the continued push for cable modems is an important part of the discussion in which Green engages us. Paul Green takes us on a journey through all aspects of the FTTH landscape. He has crafted an exceptional book that explains why Fiber to the Home is finally coming to your neighbourhood. After arguing, most effectively, that the access network represents an enormous bandwidth gap between the backbone network and the end user computational platforms, he then takes us through the many layers of design and device issues related to fiber. First we are exposed to the different architectural choices for passive optical networks (PONs) leading finally to a very nice summary table that compares the ATM-based and Ethernet-based PONs; he then offers his opinion that “. . .the most striking difference, in this modern world of IP packets, the Web and ubiquitous small, cheap laptops and desktops, is the complexity of the (ATM-based) APONs compared to the (Ethernet-based) EPONs. . . much is due to the tyranny of the 125-microsecond framing” that comes from the telco world. He further offers “It is this author’s prediction that EPONs and their descendants are likely to become the norm everywhere” and he further slams the ATM-based technologies with “. . .the heritage of ATM cells and 125-microsecond framing are increasingly likely to be seen as an expensive luxury from the past, eventually achieving only a lingering archeological significance”. Next, we are presented with the base technologies underlying FTTH and Green quickly observes that “. . .the principle technology challenge of FTTH has been to cost-reduce the appropriate subset of historically available solutions, rather than to invent new ones”. He lays down the physics underpinnings of the various elements that make up the FTTH system in a straightforward fashion that is eminently understandable. In so doing, he lifts the veil of mystery about how fiber optics works. We then return to the more practical issues of deploying FTTH systems, after which I felt the urge to purchase a hardhat and begin installing fiber in my neighborhood. The state of current deployments worldwide is a most interesting chapter as well, where we are treated to a comparison of the many different drivers and levels of penetration across the world. Sadly, it is the case that the United States is sixteenth in terms of broadband penetration on a percentage basis, with many of the Asian countries way ahead of the United States. In summary, fiber is finally making its move into the edge of the network. The technology is sound, the demand is here, and the cost structure is compelling. Paul Green has been working in fiber optics for decades and has been a champion of the tremendous bandwidth and low attenuation offered by something so thin and so small. His deep expertise in fiber optics specifically, and digital communications in general comes through in this excellent book. If you want to know all things about FTTH, you have picked the right book. LEONARD KLEINROCK Professor of Computer Science UCLA |
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发表于 2008-1-23 13:36:23
