Optical E-field modulation using a directly driven laser

A method of synthesizing an optical signal using a directly driven laser for transmission through a link of an communications network, the method comprising steps of:

• calculating respective in-phase and quadrature sample values I(n) and Q(n) of a target optical E-field envelope;
• processing the in-phase and quadrature sample values I(n) and Q(n) to calculate corresponding amplitude and phase values S(n) and P(n) respectively representative of target amplitude and phase S(t) and P(t) of the target optical E-field envelope;
• scaling the amplitude and phase values S(n) and P(n) to obtain corresponding scaled amplitude and phase values;
• generating a phase drive signal VP(t) based on the scaled phase values and a phase transfer function Tp of the laser, the phase transfer function TP being defined such that applying the phase drive signal VP(t) to the laser will yield an optical signal having an output phase φ(t) corresponding to the target phase P(t);
• and
• driving the laser using the phase drive signal to generate the optical signal;
• wherein scaling the phase values P(n) limits the output phase φ(t) of the optical signal to a predetermined range of angles.