Abstract

Linear DFB lasers are important elements in analog applications. In fiber-optical cable TV systems the linearity specifications are stringent: composite second-order (CSO) distortions for 80 channels must not exceed -60 dBc. The dominant intermodulation distortion (IMD) is commonly attributed to the nonlinearity of L-I characteristics arising from a spatially inhomogeneous distribution of the optical field. Other sources of nonlinearity are considered relatively small,¹ We note, however, that inhomogeneous field distribution is not fundamentally inherent to CATV lasers. Thus, lasers with a practically homogeneous field distribution have been obtained² by introducing two X/8 phase shifts in the DFB grating.

© 1994 Optical Society of America