Pulse or digital communications – Synchronizers – Phase displacement – slip or jitter correction
Reexamination Certificate
1998-10-07
2001-10-23
Pham, Chi (Department: 2631)
Pulse or digital communications
Synchronizers
Phase displacement, slip or jitter correction
C375S375000
Reexamination Certificate
active
06307906
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to fiber optic communication, and more particularly, to a multiple-channel clock and data recovery scheme for re-timing fiber optic data input streams into a synchronous state.
2. Description of Related Art
With the advent of parallel ribbon fiber cable and optical component array integration, high-speed optical data communication links are becoming increasingly practical and desirable. It is a challenge in achieving low-cost parallel modules for formatting fiber optic data, however, to incorporate a data receiver that performs clock and data recovery on multiple data input channels simultaneously. A typical data communications receiver for a single-channel input system requires a clock recovery circuit to extract timing information from an incoming data bit stream.
The recovery clock provides synchronous sampling off of the input data bits.
Carrying this approach to a multi-channel input system, however, induces error into the system. The application of the typical single-channel approach to a multi-channel input system typically requires integrating multiple clocks, e.g. one clock per channel. However, integrating one clock per channel results in multiple clocks that are competing on a single integrated circuit. The multiple clocks each tend to accumulate jitter due to the cross-coupling of the associated relatively high-power signals.
A need exists, therefore, for a multiple-channel clock and data recovery scheme that is capable of outputting a single clock signal to re-time all of the multiple channel data and that is thereby able to reduce the jitter and channel crosstalk that can occur with multiple clocks.
SUMMARY OF THE INVENTION
The problems outlined above are in large measure solved by a multiple-channel clock and data recovery scheme according to the present invention. The multiple-channel clock and data recovery scheme is a data synchronization system for a fiber optics data communication receiver. The fiber optics data communication receiver has a plurality of fiber optic data inputs. Each data input is received by a data sampler. The data sampler samples the input data according to a transition in a clocking signal received from a single clock. Each data sampler produces a data output for each fiber optic data input sampled. A phase detector is provided for each data input channel and compares this data output with the single clock signal. The phase detector determines a phase difference between the data output and the clock signal for each data input channel. The single clock averages the phase differences for all of the data input channels and determines an average data center for all of the data input channels. The single clock then produces the clocking signal, which is directed to the data sampler and phase detector, such that the data sampler samples the input data at the average data center.
REFERENCES:
patent: 5537448 (1996-07-01), Schwarz et al.
patent: 6009134 (1999-12-01), Yoon
patent: 6041090 (2000-03-01), Chen
patent: 6211739 (2001-04-01), Synder et al.
Tanji Todd M.
Welch James R.
Applied Micro Circuits Corporation
Gary Care Ware Freidenrich
Nguyen Dung X.
Pham Chi
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