Colour simplex coding for brillouin distributed sensors

The possibility to customize Simplex coding for long range Brillouin Optical Time Domain Analysis is demonstrated by “colouring” the sequences in the frequency domain. The coding gain is identical to the traditional intensity-modulated Simplex code, though with much simplified series of sequences. The frequency-hopping pulses in return-to-zero intensity-modulated format are generated with a Direct-Digital Synthesizer. The proof-of-concept is experimentally demonstrated with measurements over a 50 km range (100 km fibre-loop) and a 2 meter spatial resolution.