Clock extraction circuit for fiber optic receivers

Details Clock extraction circuit for fiber optic receivers Clock extraction circuit for fiber optic receivers

1993-12-08

1995-07-11

Chin, Stephen

Pulse or digital communications

Repeaters

Testing

331 2, 375359, H03D 324, H04L 702, H03L 700

Patent

active

054328276

ABSTRACT:
A circuit for regenerating a clock signal from an NRZ encoded signal. The NRZ signal is filtered, differentiated, and applied to a nested phase-locked loop. The main loop of the phase-locked loop includes a voltage controlled crystal oscillator. The inner loop of the nested phase-locked loop includes a voltage controlled oscillator which multiplies the frequency of the signal provided by the crystal oscillator to obtain the regenerated clock signal. Tunable low pass filters are used in the differentiating circuit as delay elements. The voltage controlled oscillator includes a tunable low pass filter and an integrator. The control voltage for the inner loop voltage controlled oscillator is used to control the low pass filters of the differentiating circuit in a frequency locked loop.

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D. J. Millicker et al, Bell Communications Research Inc., "Delay-and-multiply timing recovery circuit for lightwave transmission systems using NRZ format", OFC 1985 chapter TUG3.

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