Methods of measurement of passive integrated optical waveguides

The author examines popular method of evaluating losses of integrated optical waveguides. The aim in measuring these waveguides is usually to establish the propagation loss to the optical mode, and consequently evaluating the insertion loss of a device is not sufficient. This is because the propagation loss is closely related to the properties of the material in which the waveguide is fabricated and therefore, for a given waveguide geometry, can be reduced very little without improving the quality of the materials involved or their interfaces. In evaluating the propagation loss it is sometimes difficult to distinguish between genuine propagation loss and effects related to insertion loss such as Fresnel reflection, and input coupling efficiency. For this reason these issues are also addressed briefly, by means of consideration of some example results. The parameters that affect the accuracy and convenience of each of the measurement techniques are considered. >