Timing calibration of the optical sensors for undersea neutrino telescopes

This paper describes the timing calibration system for the NEMO underwater neutrino telescope. The NEMO Project aims at the construction of a km3 detector, equipped with a large number of photomultipliers, in the Mediterranean Sea. We foresee a redundant system to perform the time calibration of our apparatus. Such a system can be extended to work for a very large apparatus, even for complex arrangements of widely spaced sensors. The NEMO prototyping activities ongoing at a test site off the coast of Sicily will allow the system described in this work to be operated and tested in situ next year.