In this survey of methods of producing modulated light emphasis is placed upon recent developments. Techniques are available for producing pulses of high intensity lasting for less than 5 × 10^-9 sec, whilst continuous modulation at 10¹⁰ c/s appears feasible. For use in laser communication links the main interest is in obtaining bandwidths of order 1 Gc/s: the rapid progress now being made in this and other fields is briefly outlined.