pvf@att.att.com (10/13/89)
In Volume 9 Issue 441 of TELECOM Digest, Larry Lippmann offers a thorough review of coaxial cable and microwave radio technologies and points out that these system require more bandwidth to carry digital signals compared to analog signals. Then, he goes on to say that because of the large embedded base of analog technology in the AT&T network, it will be a long time before AT&T's network is 100% digital. I pulled out my copy of the 1988 AT&T Annual Report, published in February 1989, to see if it had anything to say on this subject. Here's what I found on page 4: "By mid-1989, 95 percent of our domestic switched traffic will be carried digitally, increasing to 100 percent by the end of 1990. By the end of 1992, all private-line facilities will be digital as well. With our new digital lightwave systems, we quadrupled our domestic fiber-optic capacity and, by laying the first trans-Atlantic fiber-optic cable, doubled circuit capacity between the United States and Europe. We plan to install more fiber-optic cable in the Pacific, Caribbean and the Atlantic." Obviously, Larry's discussion left out all the fiber we have in our network. We have been deploying fiber-optic cable for several years. In fact, we have more route miles of fiber than any other carrier. Keep in mind, too, that the capacity of a fiber cable is quite high. The 1.7 gigabit/sec systems that we have been installing for the past year or two have a capacity of 36 DS3s, or 24,192 voice-grade circuits. And that is for one pair of fibers. A typical cable has many pairs of fiber, many of them still sitting unlit. We also have a significant amount of digital coax and radio already out there. So, it won't take as long as Larry fears for AT&T's network to become predominantly digital. It has already happened. I'm not even sure that the targets I quoted above for becoming 100% digital are still valid. Given the number of times AT&T has decided to accelerate its digitization plans, those public statements from February could be out of date already. Paul Flynn pvf@houdi.att.com AT&T Bell Laboratories, Holmdel, NJ