Planar waveguide optical delay line has the advantage of small size and easy integration. Not only the length of the waveguide can be precisely designed to control the delay time, but also super long waveguide line is able to be easily produced. Planar waveguide optical delay line has important applications in optical communication.

Figure 1.  Light path diagram of planar waveguide

A planar optical waveguide integrated on a quartz substrate is shown in Figure 1. It is connected to OCI1500 for measuring with the spatial resolution of 10 μm.

(a)

(b)
Figure2. Measurement results

The lengths of two waveguides which are shown above are 2.30199m and 3.09831m. Rayleigh backscatter produced in the delay line forms a slope and presents regular semicircle. The descending amplitude of the slope represents the insertion loss resulting from the entire waveguide and the value is about 3.3dB/m in figure (b. The semicircle is caused by the screw-type path and the emergence of sudden loss points is caused by a large bend in the center of the path.