Optical waveguide grating interrogation system and sensor system

An optical waveguide grating interrogation system 10 comprises bi-directional optical amplifying and gating means, in the form of a semiconductor optical amplifier (SOA) 14 and an optical pulse source 12, 14. Drive means 22 (an electrical pulse generator triggered by a variable frequency oscillator) are provided to generate electrical drive pulses (see inset (a)) which are applied to the SOA 14, to cause the SOA 14 to switch on and off. The optical pulse source comprises a super-luminescent diode (SLD) 12, the CW output from which is gated into optical pulses by the SOA 14. The SOA 14 is optically coupled to the waveguide 16 containing an array of gratings G to be interrogated. The interrogation system further comprises wavelength evaluation apparatus 18, optically coupled to the SOA 14, operable to evaluate the wavelength of a returned optical pulse transmitted by the SOA 14.