Optical components supplier, Southampton Photonics, Inc (SPI) UK has been awarded a contract by QinetiQ to design, develop and manufacture distributed feedback fibre lasers (DFBs). It is planned that the lasers are to be used in an application for sensing acoustic signals.
According to a statement, DFB fibre lasers are finding important applications in a wide range of functions such as hydrophony, seismology, ocean bed surveying, multiphase flow measurements and sub-sea oil and gas pipeline monitoring. Furthermore, when DFBs are packaged as sources, their narrow line width makes them suitable for sensing applications such as LiDAR and LiDAR arrays.
The secret of the laser, which is built into the optical fibre itself, lies in the associated Fibre Bragg Grating (FBG), which determines the lasing wavelength.
When suitably packaged for sensing, the lasing wavelength of a DFB is very responsive to the pressure changes in its environment. Pressure fluctuations caused by acoustic signals produce changes in the length of the Bragg grating. These give rise to infinitesimal shifts in the lasing wavelength that can be detected and processed to recover the acoustic signal.
DFB acoustic sensing technology is said to have many advantages over existing solutions, in terms of size, weight, reliability and cost. In addition, the ability to use the devices in multi-channel arrays is of particular interest to QinetiQ. Using the DFBs in such an array enables a precise range and bearing of an acoustic source to be determined.