THEORY OF POLARIZATION SPREADING TECHNIQUES .1.

This paper, together with a companion one [1], constitute a thorough p resentation and analysis of a series of techniques grouped under the d enomination ''Polarization Spreading,'' the intent of which is that of making the performance of a coherent optical receiver insensitive to the polarization transformations occurring along the optical fiber, wi thout resorting to polarization compensation or control. The principle on which Polarization Spreading operates is that of spreading the sig nal power over different states of polarization, so that heterodyning of at least half of the optical incident bit energy is always ensured. The main obtained results concern a condition that guarantees the max imum heterodyned signal energy, some classes of spreading waveforms sa tisfying the above condition, the derivation of the structure and perf ormance of optimum receivers in Gaussian noise; and, presented in [1], the analysis of a suboptimum but easily implementable receiver and a detailed spectral and performance analysis of all the known spreading waveforms. The results encompass most of the binary optical coherent m odulation schemes proposed and experimented, such as ASK, FSK and DPSK .