1. Field of the Invention
The field of the invention is that of electronic devices for generating synchronization signals. More specifically, the technical field is that of very high resolution synchronization signals, the temporal accuracy of the signals being less than a nanosecond. These devices are in particular used in the laser subsystems that deliver high-energy, ultra-brief laser pulse trains, the duration of the pulses being of the order of a few hundreds of femtoseconds and their energy being of the order of a terawatt.
2. Description of the Invention
These subsystems more often than not comprise a large number of optoelectronic elements needed for generating, amplifying and formatting the laser pulses and elements for controlling, monitoring and measuring these pulses. Now, the pulses emitted are of very brief duration, so it is vitally important to synchronize the various elements of the subsystem with a high temporal accuracy so as to ensure both optimal operation of the subsystem and the best possible reproducibility of the emitted pulses.
The current synchronization devices present a certain number of drawbacks. On the one hand, the internal clock of these various devices is not necessarily perfectly synchronized with an external signal taken from an element of the system to be synchronized. On the other hand, when the system comprises a large number of elements to be synchronized it becomes impossible to synchronize them all with a single synchronization device. In this case, several synchronization devices are used, these devices being synchronized between themselves by trigger devices. These triggers are produced from clock signals internal to the synchronization devices. These clock signals are periodic. It can be demonstrated that the triggering accuracy is equal to a period of the clock signal. For example, for a clock signal emitted at a frequency of 100 megahertz, the synchronization accuracy is then equal to one period, or 10 nanoseconds. This accuracy is not sufficient, for certain applications, to permit a perfect synchronization of the various elements of the system.
To overcome these drawbacks, the device can operate no longer with an internal clock but with an external clock taken from the device to be synchronized. Thus, any temporal drift and any triggering inaccuracy of the synchronization signals is avoided. However, this solution presents the drawback that, if the external signal disappears, the entire synchronization devices can no longer function. The disappearance of the synchronization signals can then have serious consequences. In practice, the breakdown of the external clock signal is the manifestation of a malfunction of the system to be synchronized. For some applications, in particular in pulsed laser subsystems, it is important to take measures to protect the elements of the subsystem that can be damaged by this malfunction. Such is the case in particular with power amplifiers which must operate only in the presence of the laser beam to be amplified.
The device according to the invention comprises a security device for compensating for the malfunctions of the external clock by the provision of an internal clock which takes over from the external clock in the event of a malfunction. The device also comprises electronic management means for continuing to manage the system to be synchronized and so prevent elements from being damaged.