Measurement of excess loss in planar silica X junctions

Abstract
Planar silica provides a compact and stable medium for the fabrication of optical delay lines for signal processing applications. One particularly compact design involves the use of 90% crossovers (X junctions) to allow coiling of buried channel waveguides to form the delay line without the discontinuity loss associated with loopback structures. The Letter presents measurements of the excess loss due to these and compares the results with theoretical treatment.