Development and testing of a fire-resistant optical cable

A new type of fire-resistant optical cable has been developed. It is based on the loose tube concept employing special mica and glass tape wrappings together with a new type of buffer jacket material to provide the desired properties. With this design, ordinary acrylate-coated fibers are used. The cable has the unique property that during fire it converts from a cable, which mostly consists of organic materials, to a ceramic loose-tube structure that gives the fiber sufficient protection to prevent damage during fire. The cable has been tested according to IEC 331 which specifies a 750°C flame exposure for 3 h, and passed that test with negligible loss increase even at temperatures up to 900°C.     

A New Digital Echo Canceler for Two-Wire Subscriber Lines

A new type of digital echo canceler for two-wire digital transmission is presented. The new principle involves very simple signal processing and is thus an interesting alternative for digital transmission on subscriber lines. The principle is compared with other echo cancellation techniques, and it is shown how choice of line code, equalization, and carrier recovery are affected by the new echo canceler. A theoretical analysis of the principle is given, taking into account finite accuracy, jitter, noise, and correlated data streams. The echo canceler can be used for line attenuation up to 40 dB. At 80 kbits/s this corresponds to at least 7 km 0.6 mm cable and is sufficient to cover more than 99 percent of the existing Norwegian subscriber lines.     

New line code for digital subscriber loop

A new line code is presented which may find applications in the future digital subscriber loop. The line code is well balanced and has a narrow frequency spectrum.