Limitations on peak pulse power, pulse width, and coding mask misalignment in a fiber-optic code-division multiple-access system

The authors analyze the effects of fiber dispersion and optical nonlinearity on a code-division multiple-access (CDMA) communications system. They assume that each transmitter has a unique phase-encoding mask to scramble the pulses, and that the intended receiver has the complementary phase-decoding mask to unscramble the pulses. The necessary nonlinear pulse propagation equation is derived using a new and systematic approach. The authors then determine the minimum allowable pulse width and the maximum pulse width for the system. They next calculate the maximum optical power, which is limited by the fiber´s self-phase modulation. This power is significantly larger than the minimum detectable optical power determined by the noise in the electrical receiver, so that in practice any distortion caused by the fiber´s optical nonlinearity can be avoided. From their calculations estimates for all important optical parameters are provided. The deleterious effect of a slight relative misalignment between the encoding and decoding masks is also investigated