I/Q coding method for SDM communication system over optical fibre

SDM transmission method over optical fiber with polarization duality, intended to transmit, during one channel use, 2N symbols belonging to a modulation constellation in the complex plane, N>1 being the number of spatial elementary channels used for transmission, characterized in that:

• said symbols undergo a separation into real part and imaginary part (220-520) to provide a first vector consisting of the real parts of these symbols and a second vector consisting of the imaginary parts of these same symbols;
• a first orthogonal linear transformation (230-1, . . . , 430-1) is applied to the first vector to provide a first transformed vector;
• a second orthogonal linear transformation (230-2, . . . , 530-2), distinct from the first, is applied to the second vector to provide a second transformed vector;
• a complex scalar, solution of an irreducible polynome from [X] in is multiplied to the first or to the second transformed vector, before the two transformed vectors are summed to provide a vector consisting of 2N complex emission symbols, each complex transmission symbol modulating a first state and a second polarization state of a spatial elementary channel.