Francesco F Ledda

US Patent:

6816680, Nov 9, 2004

Filed:

Dec 12, 2000

Appl. No.:

09/735034

Inventors:

Christopher M Purse - Chelmsford, GB
Francesco Ledda - Plano TX

Assignee:

Nortel Networks Limited - St. Laurent

International Classification:

H04J 1402

US Classification:

398 5, 398 1

Abstract:

An optical network has a main fiber ( ) and a protection fiber ( ) between a source node ( ) and a destination node ( ). The source node ( ) is provided with a plurality of transponders ( ) and a splitter ( ) for providing source node data onto the main and protection paths, with the transponders ( ) being positioned on the node side of the splitter ( ). The destination node ( ) is provided with a plurality of transponders ( ) and a switch ( ) for selecting which of the main and protection paths to route to a receiver ( ) of the node, the transponders ( ) being positioned on the node side of the switch ( ). This arrangement reduces the number of transponders required, as they are provided before the splitter at the transmitting node, and after the switch at the receiving node. The destination node ( ) preferably further comprises a monitoring arrangement for monitoring the signal from the protection path ( ).

US Patent:

56129807, Mar 18, 1997

Filed:

Mar 22, 1995

Appl. No.:

8/408313

Inventors:

Francesco Ledda - Plano TX
Jeffrey W. Tsao - Plano TX

Assignee:

Alcatel Network Systems, Inc. - Richardson TX

International Classification:

H03D 324

US Classification:

375375

Abstract:

A system and method for fast frequency locking are provided in which the phase difference between first and second synchronization signals is measured (22). The frequency difference between the two signals is then determined (24). The frequency of the second synchronization signal is then set to that of the first synchronization signal (26). Thereafter, the feedback loop of a phase-locked loop circuit is closed, with an error signal representative of the phase difference between the first and second synchronization signals being offset by an amount equal to an error signal generated when the frequency of the second synchronization signal is set to that of the first synchronization signal.

US Patent:

55966144, Jan 21, 1997

Filed:

Sep 13, 1995

Appl. No.:

8/528424

Inventors:

Francesco Ledda - Plano TX

Assignee:

Alcatel Network Systems, Inc. - Richardson TX

International Classification:

H03D 324

US Classification:

375376

Abstract:

A method and circuitry are provided for detecting and measuring a phase difference between the output signals from a primary stratum clock and a standby stratum clock in a telecommunications system, computing a period of time needed for a numerically-controlled oscillator to shift the frequency of the standby clock enough to cancel the phase difference, transforming the required period of time into a signal representing a corresponding number of frequency shift steps, and controlling the numerically-controlled oscillator with the step signal to shift the frequency of the standby clock accordingly and thereby cancel the phase difference. Both the frequency and phase alignments of the two clocks are thus maintained. Therefore, when either the system or user switches operations from the primary stratum clock module to the standby stratum clock module, phase-related transients are not generated, which results in a significant increase in the overall performance and reliability of the system.