Fig. 2
Realisation of Alamouti coding. a The analogy between wireless (two transmit antennae) and optical fibre communication (dual-polarisation transmitter), corresponding to a multiple-input-single-output system. b Alamouti polarisation-time block coding (PTBC) scheme and the illustration of polarisation rotation. E X and E Y correspond to the optical fields carrying the information and coded symbols (\(\left[ {{X_1}\quad {X_2}} \right]\) and \(\left[ { - X_2^*\quad X_1^*} \right]\)) in X- and Y-polarisation modes, generated using transmitter 1 and 2 (TX 1,2). Subsequently, the transmitted signal beats with the local oscillator E LO in the receiver (RX 1). I in-phase, Q quadrature
