DECISION-DIRECTED PLL FOR COHERENT OPTICAL PULSE CDMA SYSTEMS IN THE PRESENCE OF MULTIUSER INTERFERENCE, LASER PHASE NOISE, AND SHOT-NOISE

Citation
W. Huang et al., DECISION-DIRECTED PLL FOR COHERENT OPTICAL PULSE CDMA SYSTEMS IN THE PRESENCE OF MULTIUSER INTERFERENCE, LASER PHASE NOISE, AND SHOT-NOISE, Journal of lightwave technology, 16(10), 1998, pp. 1786-1794
Citations number
24
Categorie Soggetti
Optics
ISSN journal
07338724
Volume
16
Issue
10
Year of publication
1998
Pages
1786 - 1794
Database
ISI
SICI code
0733-8724(1998)16:10<1786:DPFCOP>2.0.ZU;2-A
Abstract
A digital decision-directed phase-locked loop (PLL) for use in optical pulse code-division multiple-access (CDMA) systems based on coherent correlation demodulation is proposed. PLL performance is affected by m ultiuser interference, laser phase noise and optical shot noise. The e ffect of these sources of interference and noise on PLL performance is evaluated based on a nonlinear model (the Fokker-Planck method) since a linear analysis yields large deviations between the analytical resu lts and actual performance at low signal-to-noise ratios (SNR's), Afte r describing the implementation of the PLL, the steady-state probabili ty density function (pdf) of the phase estimator is derived, Numerical evaluation of the variance of the phase estimator is given for Gold c odes. The linewidth requirements of the laser for an acceptable phase estimator variance and the value of the optimal loop bandwidth minimiz ing the impact of the interference and noise on the PLL are discussed.