Photonic integrated Brillouin optical time domain reflection readout unit

Brillouin scattering can be used for determining strain distributions along fibers. This is a convenient way to monitor the structural integrity of large constructions. However, the high cost of the optical circuitry has prevented wide use of this technique. We report on a design study on an integrated optical circuit for a Brillouin optical time domain reflection readout unit with low-cost potential. The circuit contains narrow linewidth tuneable distributed Bragg reflector (DBR) lasers, photodiodes with an optical mixer for coherent detection, a 10-bit digitally switched delay line for frequency tuning, and a switching fabric that allows three modes of operation. Such a circuit can be realized through one of the upcoming foundries in the field of photonic integration. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3574377]