A new kind of correlated photon-pair source based on a waveguide integrated on a periodically poled lithium niobate substrate is reported. Using a pump laser of a few μW at 657 nm, photon-pairs are generated/degenerated at 1314 nm. Detecting ~1500 coincidences per second, a conversion rate of 10-6 pairs per pump photon can be inferred, which is four orders of magnitude higher than that obtained with previous bulk sources. These results are very promising for the realisation of sources for quantum communication and quantum metrology experiments requiring a high signal-to-noise ratio or working with more than one photon-pair at a time