1. Field of the Invention
The present invention relates to an optical device for generating, from an input optical impulse, a first and a second output optical impulse, each having a preselected temporal phase shift with respect to the input optical impulse and a preselected duration.
2. Technical Background
At the present time, in telecommunications networks, optical technology is predominantly used for the transmission of optical signals, in which use is made of the known wideband properties of optical fibres, while the operations of processing the optical signals, such as multiplexing and switching, are carried out by means of opto-electronic devices.
However, opto-electronic devices have the known disadvantages of electronic circuits which are becoming bottlenecks in optical communications systems and in optical networks. This is because electronic devices have a narrow bandwidth compared with the optical band available in optical communications systems, and are generally based on a relatively slow serial processing of the signals.
Research is therefore being increasingly directed towards the possibility of using optics not only for the transmission of signals but also for their processing. This is due to the fact that, potentially, wholly optical devices have a wide bandwidth and are transparent to the bit rate, the format and the code of the transmission.
The inventors of the present invention have noted the necessity of an optical device which, on receiving an optical impulse at its input, is capable of supplying two optical impulses at the output, for example two optical control impulses, each having a preselected temporal phase shift with respect to the input optical impulse and also having a preselected duration.
A first aspect of the present invention is therefore an optical device comprising:
an input for an input optical impulse;
an optical beam splitting element for supplying, from the said input optical impulse, a first pair of optical impulses and a second pair of optical impulses;
at least a first optical delay element to delay, by a predetermined time, at least one of the said optical impulses of the said first pair;
at least a second optical delay element to delay, by a predetermined time, at least one of the said optical impulses of the said second pair;
a first optical processing element capable of supplying a first output optical signal when commanded by the said first pair of optical impulses;
a second optical processing element capable of supplying a second output optical signal when commanded by the said second pair of optical impulses;
a first output connected to the said first optical processing element for the said first output optical signal;
a second output connected to the said second optical processing element for the said second output optical signal.
Typically, the said first output optical signal has a duration which is modified with respect to at least one of the said optical impulses.
Generally, the said second output optical signal has a duration which is modified with respect to at least one of the said optical impulses.
Preferably, the said optical beam-splitting element comprises a first optical beam splitter, to form a first and a second optical impulse from the said input optical impulse, and a second and a third optical beam splitter to form the said first pair of optical impulses and the said second pair of optical impulses from the said first optical impulse and from the said second optical impulse, respectively.
More preferably, the said optical device also comprises at least a third optical delay element to delay, by a predetermined time, at least one of the said first and second optical impulses.
Typically, the said first optical processing element consists of an optical flip-flop. Preferably, the said second optical processing element also consists of an optical flip-flop.
A second aspect of the present invention is therefore a method for supplying, from an input optical impulse, a first and a second output optical impulse, each having a preselected time delay with respect to the input optical impulse, and also having a preselected duration, the said method comprising the steps of
a) supplying the said input optical impulse;
b) supplying a first pair of optical impulses and a second pair of optical impulses from the said input optical impulse;
c) imparting a predetermined delay to at least one of the said optical impulses of the said first pair;
d) imparting a predetermined delay to at least one of the said optical impulses of the said second pair;
e) supplying the said first output optical impulse as a function of the said optical impulses of the said first pair;
f) supplying the said second output optical impulse as a function of the said optical impulses of the said second pair.
Preferably, one of the said optical impulses of the said first pair is delayed by a predetermined time with respect to the other.
Advantageously, one of the said optical impulses of the said second pair is delayed by a predetermined time with respect to the other.
According to one embodiment, step e) consists in supplying an output optical signal at the command of one of the two optical impulses of the said first pair and interrupting the transmission of the said output optical signal at the command of the other of the two optical impulses of the said first pair, in such a way as to supply the said first output optical impulse.
According to another embodiment, step f) consists in supplying an output optical signal at the command of one of the two optical impulses of the said second pair and interrupting the transmission of the said output optical signal at the command of the other of the two optical impulses of the said second pair, in such a way as to supply the said second output optical impulse.
Preferably, the said first output optical impulse has a duration which is modified with respect to the said input optical impulse.
Even more preferably, the said first output optical impulse is time-delayed with respect to the said input optical impulse.
Preferably, the said second output optical impulse has a duration which is modified with respect to the said input optical impulse..
Even more preferably, the said second output optical impulse is time-delayed with respect to the said input optical impulse.