Abstract: The present invention concerns a method of protecting the transmission of cells in a telecommunication system, the method consisting, on the transmitter side, of simultaneously transmitting two identical flows of cells on two distinct physical links and, on the receiver side, of receiving each of the two flows of cells respectively transmitted on the said two links and selecting one of them. The method further consists, on the transmitter side, of inserting, regularly in each of the flows, cells serving as markers and thus delimiting blocks of cells or sets of blocks of cells, and, on the receiver side, of selecting, block after block or group of blocks after group of blocks, the block or group of blocks from the flow of cells which has the fewer transmission errors compared with the block or group of blocks of the same order number in the other flow.

Abstract: A device for the control of the output power of laser diodes designed to be coupled to an optical fiber for the tranmission of data comprises a photodiode that can be used to acquire a characteristic signal of the power emitted by the laser diode; digital means to drive the laser diode comprising a central processing unit associated with servo-control computation program memorizing means to keep a constant output power whatever may be the drift and change of slope of the characteristic of the laser diode in response to ageing phenomena or to a change in temperature or to a loss of power due to the coupling of this diode with an optical fiber or to variations in the response of the photodiode as a function of the temperature. Application to digital transmission by optical fiber.