Apparatus for modulating the output signal of a converter

An arrangement for modulating the output signal of an electro-optical converter that converts an electric analog input signal into an optical output signal comprising:

• a subtraction device having a first input which receives an analog input signal, means coupling an output of said subtraction device to an input of a limiter which produces a binary output signal the value of which depends on the polarity of the input signal with respect to a discrimination level, an adjustable current source controlled by the limiter output signal and connected to said converter, a photo-detector for detecting a portion of an optical output signal of said converter, means for supplying said portion of the optical output signal to a second input of said subtraction device so that the signals present at said inputs are subtracted from one another, said subtraction device, limiter, converter and photo-detector being coupled together to form a feedback loop having a bandwidth and a gain such that said loop will be self-oscillating at a frequency outside the frequency band of the analog input signal.

Apparatus for modulating the output signal of an electro-optical converter comprising:

• an analog electric signal input terminal, a signal combining device having first and second inputs and an output, means coupling a first input of the combining device to said signal input terminal, a signal limiter having an input coupled to the output of the combining device and an output at which appears a binary output signal for controlling said converter, an integrator device coupled between an output of the converter and the second input of the combining device, and means coupling the combining device, the limiter, the converter and the integrator in a wideband high gain negative feedback loop in which a self-excited oscillation is produced and wherein said analog signal modulates the pulse width and/or the pulse density of the limiter output signal.