Flexible bit rate clock recovery unit

Details Flexible bit rate clock recovery unit Flexible bit rate clock recovery unit

1999-11-17

2001-10-16

Pham, Chi (Department: 2631)

Pulse or digital communications

Synchronizers

C375S371000

Reexamination Certificate

active

06304622

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a regenerator device in an optical network, and particularly to a flexible bit rate clock recovery unit for use in the regenerator device.
2. Technical Background
Regenerators are used in optical communication systems to prevent the accumulation of signal distortion. A regenerator typically performs re-amplification, re-shaping and re-timing functions on an incoming data signal. In order to perform the re-timing function, it is necessary to extract the clock signal associated with the incoming data signal.
Conventional clock recovery units have only limited tuning range (e.g., typically less than 1% of the clock rate). This type of clock recovery unit does not pose a problem for optical communication systems which operate at a single bit rate. However, today's optical communication system must support input data signals transmissible at a variety of different bit rates.
Therefore, it is desirable to provide a clock recovery unit for recovering clock signals from input data signals transmissible at a variety of different bit rates. The clock recovery unit should identify the bit rate of the incoming data signal and extract the clock signal from it so that the incoming data signal can be correctly re-timed for retransmission.
SUMMARY OF THE INVENTION
One aspect of the present invention is a flexible bit rate clock recovery unit for recovering a clock signal from an input data signal, where the input data signal is transmissible at different bit rates. The flexible bit rate clock recovery unit includes a plurality of fixed rate clock recovery units, where each fixed rate clock recovery units is operative at a different bit rate to extract an intermediary clock signal from the input data signal; a comparator for generating an encoded data signal based on an amplitude characteristic of each of the intermediary clock signals, where the encoded data signal is indicative of the clock signal associated with the input data signal; and a selector for selecting one of the intermediary clock signals based on the encoded data signal, thereby recovering the clock signal from the input data signal.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described in the detailed description which follows, the claims as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.


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Ushirozawa, M.; Asahi, K; Noda, A.; Fujita S. “Bit-rate-Independent SDH/SONET Regenerator for Optical Network” from the 11thAnnual International Conference on Integrated Optics and Optical Fibre Communications 23rdEuropean Conference on Optical Communications IOOC-ECOC 97, Edinburgh, UK; Sep. 22-25, 1997 (Conf. Publ. No. 448) p. 5 vol. (xiii+202+xvi+296+xviii+370+viii+120+vii+92), 25-8 vol. 4.

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