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 multiuser interference, laser phase noise and optical shot noise. The effect 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 results and actual performance at low signal-to-noise ratios (SNR's). After describing the implementation of the PLL, the steady-state probability density function (pdf) of the phase estimator is derived. Numerical evaluation of the variance of the phase estimator is given for Gold codes. The linewidth requirements of the laser for an acceptable phase estimator variance and the value of the optimal loop bandwidth minimizing the impact of the interference and noise on the PLL are discussed.

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  1. N. A. Olsson, "Lightwave systems with optical amplifers," J. Lightwave Technol., vol. 7, pp. 1071-1082, July 1989.
  2. M. J. O'Mahony, "Semiconductor laser optical amplifers for use in future fiber systems," J. Lightwave Technol., vol. 6, pp. 531-544, Apr. 1988.
  3. P. Prucnal, M. Santoro, and T. Fan, "Spread spectrum fiber optical local area network using optical processign," J. Lightwave Technol., vol. 4, pp. 307-314, May 1986.
  4. L. G. Kazovsky, "Decision-driven phase-locked loop for optical homodyne receivers: Performance analysis and laser linewidth requirements," J. Lightwave Technol., vol. 3, pp. 1238-1247, Dec. 1985.
  5. --, "Balanced phase-locked loops for optical homodyne receivers: Performance analysis, design considerations, and laser linewidth requirements," J. Lightwave Technol., vol. 4, pp. 182-195, Feb. 1986.
  6. --, "Performance analysis and laser linewidth requirements for optical PSK heterodyne communications systems," J. Lightwave Technol., vol. 4, pp. 415-425, Apr. 1986.
  7. S. Huang and L. Wang, "Exact evaluation of laser linewidth requirements for optical PSK homodyne communication systems with balanced PLL receivers," J. Lightwave Technol., vol. 14, pp. 661-664, May 1996.
  8. D. Zaccarin, D. Angers, and T. H. Huynh, "Performance analysis of optical heterodyne PSK receivers in the presence of phase noise and adjacent channel interference," J. Lightwave Technol., vol. 8, pp. 353-366, Mar. 1990.

J. Lightwave Technol. (8)

N. A. Olsson, "Lightwave systems with optical amplifers," J. Lightwave Technol., vol. 7, pp. 1071-1082, July 1989.

M. J. O'Mahony, "Semiconductor laser optical amplifers for use in future fiber systems," J. Lightwave Technol., vol. 6, pp. 531-544, Apr. 1988.

P. Prucnal, M. Santoro, and T. Fan, "Spread spectrum fiber optical local area network using optical processign," J. Lightwave Technol., vol. 4, pp. 307-314, May 1986.

L. G. Kazovsky, "Decision-driven phase-locked loop for optical homodyne receivers: Performance analysis and laser linewidth requirements," J. Lightwave Technol., vol. 3, pp. 1238-1247, Dec. 1985.

--, "Balanced phase-locked loops for optical homodyne receivers: Performance analysis, design considerations, and laser linewidth requirements," J. Lightwave Technol., vol. 4, pp. 182-195, Feb. 1986.

--, "Performance analysis and laser linewidth requirements for optical PSK heterodyne communications systems," J. Lightwave Technol., vol. 4, pp. 415-425, Apr. 1986.

S. Huang and L. Wang, "Exact evaluation of laser linewidth requirements for optical PSK homodyne communication systems with balanced PLL receivers," J. Lightwave Technol., vol. 14, pp. 661-664, May 1996.

D. Zaccarin, D. Angers, and T. H. Huynh, "Performance analysis of optical heterodyne PSK receivers in the presence of phase noise and adjacent channel interference," J. Lightwave Technol., vol. 8, pp. 353-366, Mar. 1990.

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