Lasing wavelength shifting by using grating reflectors has been regarded as a most fundamental method to make frequency tunable light sources, which are attractive and indispensable devices in optical coherent transmission systems, especially FDM systems. A degree of frequency shift and adjusting capability greatly increases in a local oscillator light source and in a transmitter light source. The important characteristics of these devices are frequency tunabillty and spectral linewidth when system applications are considered. Recent advances are reported by classifying these devices into hybrid tunable DBR LDs1,2 and monolithic tunable DBR3,4/DFB LDs,5 as shown In Table 1.
© 1988 Optical Society of AmericaPDF Article