S-shaped bend waveguide is indispensable to realize the lateral displacement and connections in the integrated optical devices, such as the optical switch matrix, star coupler and arrayed waveguide grating (AWG). Even when various optical devices are integrated onto one chip, S-bend also plays important roles. Its size and optical loss directly influences the integration dense and loss of whole device. The insertion loss (except the dispersion loss produced by the configuration defection) of S-bend includes two parts