Pull-in analysis of dither optical phase-lock loop

The pull-in behavior of dither optical phase-lock loop (OPLL) is analyzed, neglecting the shot noise and phase noise of the loop. Expressions are derived analytically for computing the pull-in voltage, pull-in limit and acquisition time for a second-order type-II dither OPLL that employs an active low pass loop filter. The influence of dither signal on the acquisition of the dither OPLL is studied in detail. It is found that dither signal allows pull-in from much larger frequency offset, decreases the acquisition time of the loop and also improves the acquisition characteristics of the OPLL in terms of the pull-in voltage. This paper also analyzes the effect of loop-delay on the pull-in behavior of the dither OPLL. The performance of the dither OPLL regarding the phase-error variance and noise bandwidth is investigated considering laser phase noise, photo-detector shot noise and dither noise. Analytical results are supported by simulations.