Filter for an optical fibre temperature sensor

A filter for an optical fibre (13) temperature sensor comprising at least one first (14,30) and one second optical filter for filtering an optical pulse reflected by said optical fibre (13), wherein said optical pulse lying within the range from 1570 nm and 1580 nm;

• said at least one first filter (14,30) and one second filter filtering two adjacent spectral windows (21,22) of the Raman anti-Stokes optical signals or Raman Stokes optical signals;
• said two adjacent spectral windows (21,22) of the Raman anti-Stokes optical signals or Raman Stokes optical signals are converted into a first electrical signal and a second electrical signal;
• said first filter (14,30) is a stopband filter centered on the Rayleigh optical signal;
• said second filter comprises a third and a fourth filter (31), said third filter being a passband filter centered on a first spectral window (21) of the Raman anti-Stokes signals, said fourth filter being a stopband filter for blocking said first spectral window (21) of the Raman anti-Stokes optical signals;
• said second filter comprises a fifth filter (32), coupled to said fourth filter, said fifth filter (32) being a passband filter which supplies a second spectral window (22), adjacent to said first spectral window (21), of the optical Raman anti-Stokes signals;
• said two adjacent optical spectral windows (21,22) lie within the range respectively of about 1450-1510 nm and about 1525-1565 nm.