Design of a Photonic Integrated Circuit (PIC) for a BOTDR read-out unit. R.F. Klein Breteler, M. Felicetti, J.J.G.M. van der Tol, G.D.J. Sasbrink, M.K. Smit / Department of electrical engineering – opto electronic devices Introduction In the expanding field of fibre sensors Brillouin scattering is a powerful effect for determining strain and temperature distributions along fibres. Circuit design Brillouin scattering COBRA COBRA COBRA COBRA Chip layout Acknowledgements This work is done within the European Europic project, and has been supported by the Dutch Ministry of Economic Affairs through the “Kenniswerkers” program BSGOC. 1550 nm 1550 nm + 11GHz MMI DET DET Delay MMI MMI φ MMI DET DET <----------------switch1-------------- > MMI MMI φ MMI MMI Coherent receiver -φ -φ fiber <----------------switch2-------------- > BOTDR Strain and temperature affects the speed of sound and thus the Brillouin spectrum. Frequency tuning A switcheable digital delay line circuit is implemented into the frequency locking circuit. This allows to tune the frequency spacing between the two lasers and enables homodyne detection of the full Brillouin spectrum. ∆f=1MHz/20με ∆f=1MHz/°C -Size: 6x3 mm -Cost: €1000,- (existing instruments: >€50.000,-) -Spatial resolution: 2m -Strain resolution: 0.004%, temperature resolution: 2°C -Sensor length: 50 km We have designed a foudry-based Brillouin Optical Time Domain Reflection (BOTDR) read-out unit with low-cost potential. Structures that can be monitored with fibre sensors. Brillouin scattering is the reflection of light from a moving grating, formed by acoustical phonons. Spectrum of backscattered light from a fibre. Backscattering in time provides spatial information. - Dual laser circuit, allows homodyne detection - Switch 1: laser selector - Switch 2: injects pulse and enables coherent detection - Laser locking circuit: stabilizes frequency spacing Five elements of the digital delay line.