Phase and frequency detectors for clock synchronization in high-speed optical transmission systems

This paper presents several phase and frequency detectors (PFD's) for clock recovery in high-speed optical transmission systems. Their performance is evaluated by means of computer simulations and laboratory experiments using a 140 Mbit/s system prototype. The results demonstrate that the proposed detectors substantially increase the loop acquisition range with respect to conventional phase detectors without degrading its steady-state jitter performance. The improvement of the acquisition performance is obtained at the expense of a very small increase of the loop hardware complexity. The presented detectors turn out to be very attractive for high-speed optical systems, because with such a detector in the timing recovery loop, it is possible to use low-precision oscillators and still meet stringent requirements on acquisition speed and steady-state phase jitter.