Other

American Telephone & Telegraph Co., At&t Bell Laboratories

At&t Information Systems Inc.

Tyco Telecommunications (US) Inc.

Tyco Submarine Systems Ltd.

Richard L Maybach

S Devendra Verma

Neal S Bergano

Cleo D Anderson

Robert L Lynch

William W Patterson

Bhaskar N Sanakkayala

Mohammad A Arbabzadah

The position and amount of localized polarization dependent anomalies such as polarization mode dispersion and/or polarization dependent loss may be measured by applying a polarization modulated probe signal to an optical transmission line. The polarization modulated probe signal is returned via optical feedback paths positioned along the line, and is detected by a probe signal receiver to identify the position and strength of the anomaly.

Method and apparatus for detecting localized polarization dependent anomalies on optical transmission lines

An OTDR provides both in-service and out-of-service measurement information for an optical transmission system with multiple repeaters. The repeaters include an optical high-loss loop back (HLLB) path and an OTDR path. The OTDR is coupled to the input lines of the optical transmission system via an optical coupler so that both traffic signals and test signals from the OTDR can be transmitted simultaneously. When the OTDR is providing in-service measurement information, test signals in the form of side-tone pulses are transmitted on the transmission system. The wavelengths of the test signals are sufficiently offset from the wavelength of the traffic signal so there is minimal interference between them. The level of the test signals is low relative to the traffic signal to also minimize interference. The OTDR filters out the traffic signal from the returned signal. The HLLB path through the amplifier pairs of each repeater is distinguishable in the filtered returned signal. When the OTDR is providing out-of-service measurement information, the level of the side-tone pulses is increased because interference with traffic signal is no longer a concern. Both the HLLB path and the OTDR path are distinguishable in the filtered returned signal when the higher level out-of-service test pulses are transmitted.

Side-tone OTDR for in-service optical cable monitoring

Control equipment employed in a customer-owned public telephone station prevents a user from making unauthorized telephone calls in a telephone system. Operating under the control of a computer in the station, the control equipment employs a call screening process which restricts the telephone numbers a user can dial to those numbers preselected by a station owner. The telephone numbers are categorized in multiple but distinct groups, each of which represents a specific class of telephone call. The control equipment is responsive to momentary loop breaks occurring on tip and ring lines connecting the station to a central office, and to a loop break provided by the central office which reflects that the far end party has disconnected. The control equipment is also responsive to scheduled as well as unscheduled receipt of dial tone. The combination of the call screening process along with the ongoing loop break and dial tone detection and analysis conveniently provides the desired protection so that the user will be properly charged for telephone calls made from the station. The restrictions incorporated in the station for obtaining this protection are applied with minimal inconvenience for the legitimate user.

Call screening in a public telephone station

Control equipment employed in a customer-owned public telephone station prevents a user from making unauthorized telephone calls in the telephone system. Operating under the control of a computer in the station, the control equipment is responsive to momentary loop breaks occurring on tip and ring lines connecting the station to a central office, and to a loop break provided by the central office which reflects that the far end party has disconnected. The control equipment is also responsive to scheduled as well as as unscheduled receipt of dial tone. The combination of ongoing loop break and dial tone detection and analysis conveniently provides the desired protection for reliable operation of the customer-owned public telephone station in the telephone system. Restrictions incorporated in the station for obtaining the desired protection are applied with minimal inconvenience for the legitimate user.

Fraud prevention in a public telephone station

Growing community of inventors

Holmdel, NJ, United States of America

Richard L Maybach