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Demodulation process of optical fibre intensity sensors and the respective device

Request number
Publication date 29-04-2009
Patent number 103.868
Grant date
Inventors Júlio Montalvo García, OrlandoFrazão,
Luís Alberto Ferreira, Francisco Araújo,
José Luís Santos, Carmen Vázquez García,
José Manuel Baptista

The present invention consists of a demodulation process of optical fibre intensity sensors using a low-cost finite impulse response electronic filter.  This filter will replace the fixed optical delay lines that are normally used in intensity optical fibres referencing. This will make it possible to implement more compact fibre sensor heads and it allows more flexibility when choosing the electrical parameters that will be employed.

When using a finite impulse response electronic filter, it is not necessary to insert a length of optical fibre delay of hundreds of meters when constructing the sensor head. Therefore, it is possible to reduce the modulation frequency from 100 kHz to 2 kHz without compromising the sensitivity. These frequency values refer to the demonstrated application. Other values may be used without restrictions in other applications.

Furthermore, if reconfiguration is required, the electrical parameters involved have to be altered only in the interrogation unit as opposed to having to replace or adjust the temperature control of the optical delay line of the sensor head which is normally located in a remote place.

The process that has been described can also be configured to demodulate optical fibre intensity sensor networks with spatial separation using wavelength multiplexing. It is also possible to remotely reconfigure one or more sensors in the network.









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