For the first time to our knowledge, continuous nonsegmented channel waveguides in periodically poled $\mathrm{K}\mathrm{Ti}\mathrm{O}\mathrm{P}{\mathrm{O}}_4$ with guided orthogonal polarizations are used to demonstrate type II background-free second harmonic generation in the telecom band with $1.6\%∕\left(\mathrm{W}{\mathrm{cm}}^2\right)$ normalized conversion efficiency. This constitutes a 90-fold improvement in aggregate conversion efficiency over its free space counterpart. Simulations show that the guided wave device should enable the measurement of timing fluctuations of optical pulse trains at the attosecond level in an optical cross correlation scheme.