Abstract: A method of measuring the error rate of an optical transmission system transmitting a signal by detecting the signal, and asynchronously sampling the signal at a frequency independent of the bit rate of the signal to obtain K samples of the signal at respective times t1 to tK, where K is an integer greater than or equal to 2. The eye diagram of the signal, the error rate of the signal and the bit time of the signal are then computed.

Abstract: The present invention relates to a method of measuring the error rate of an optical transmission system transmitting a signal, said method comprising the following operations:

Abstract: A coding process for the adaptive prediction differential PCM type. An error signal e.sub.t is formed between a sample of signal y.sub.t to be coded and a prediction signal p.sub.t of said signal. The prediction signal p.sub.t is formed from restored signals y.sub.t and e.sub.t by two linear filtering operations, the first relating to N successive samples of y.sub.t and using coefficients A1.sub.t, A2.sub.t, . . . , AN.sub.t and the second relating to P successive samples of e.sub.t and using coefficients B1.sub.t, B2.sub.t, . . . , BP.sub.t, the coefficients A1.sub.t, A2.sub.t, . . . , AN.sub.t and B1.sub.t, B2.sub.t, . . . , BP.sub.t being sequentially adjusted at each time t so that the mean power of error signal e.sub.t is minimal. Instead of carrying out the prediction on the basis of signals y.sub.t and e.sub.t only according to the invention, use is also made of the real signal y.sub.t and the real error e.sub.t. A linear filtering of y.sub.t using the coefficients A1.sub.t, A2.sub.t, . . . , AN.sub.

Abstract: A device for following and recursively estimating the local state of pict contours defined by lines of N points distributed in accordance with an orthogonal sampling structure, said points being defined by successive numerical samples.The invention also relates to a differential coded pulse modulation coder and a differential coded pulse modulation decoder.