Fiber Optics Glossary And Facts

Bandwidth: The range between the lowest and highest frequencies in a communication channel. Measured in Hertz (Hz). The greater the bandwidth, the greater the information-carrying capability.

Bell Operating Companies (BOCs): Formerly the local telephone arm of AT&T, now administered by regional holding companies. Providers of about 80 percent of local telephone service.

Bypass: Circumvention of the central office of local telephone company by the use of alternate distribution devices, such as short-haul microwave or satellite-to-private receiver, or establishment of a direct line between two or more users locations. Reduces user's telephone costs, but decreases local telephone company's billings.

Central office: The facility where all customers' lines terminate and are switched to make or receive outgoing calls. Location of the interface of local and long distance traffic, unless bypassed.

Common carrier: A provider of telecommunications services to the public, whose operations are regulated by state and federal authorities.

Fiber optics (or optical fibers): Hair-thin strands of glass or plastic that use coded light signals, generated by lasers or light-emitting diodes, to transmit voice, video, or data signals. Offers wideband digital transmission. Integrated Services Digital Network (ISDN): The capability of providing an end-to-end digital network that would carry high speed data, voice, and video.

Other Common Carriers (OCCs): Common carriers other than the Bell Operating Companies.

Point of presence: The facility established by an OCC in order to reach customers, to which the BOCs provide local telephone access.

Wideband (or Broadband): A communication channel capable of highspeed data and video transmissions, over 3,300 Hz.

"A single fiber with a transmission capacity of 560 Mbs (millions of bits per second) could carry into the home at one time the following services:

• 4 network-switchable channels with capability of delivering current analog-type video service or future high-definition television (greater than 100 Mbs per channel);

• 30 high-fidelity audio channels (8 Kilobytes (Kbs) per channel);

• 4 narrowband ISDN channels which would include traditional voice service (144 Kbs per channel); and

• 12 telemetry channels (low bit rate channels). The capacity of 560 Mbs is not a limitation of the fiber, but rather ... of the associated electronics." (Harrold, D. J. and Strock, R. D. "The Broadband Universal Telecommunications Network," IEEE Communications Magazine, v.25, n.l, pp. 71.) •

July 1987 / Illinois Municipal Review / Page 21