Title :
Spectral shift and broadening of DFB lasers under direct modulation
Author :
Zadok, Avi ; Shalom, Hamutal ; Tur, Moshe ; Cornwell, W.D. ; Andonovic, Ivan
Author_Institution :
Fac. of Eng., Tel Aviv Univ., Israel
Abstract :
The spectrum of DFB lasers, directly modulated at 144 and 622 Mb/s, is found to be considerably wider than the modulating random sequence rate. The broadening, which may be as high as ten times the data bandwidth, is accounted for by frequency changes (chirp) along each bit, incorporating a recently observed short time constant on the order of 10-20 ns. These changes will also introduce a few gigahertz spectral shifts as a function of the bit rate.
Keywords :
chirp modulation; distributed feedback lasers; optical transmitters; semiconductor lasers; spectral line broadening; spectral line shift; 10 to 20 ns; 144 Mbit/s; 622 Mbit/s; DFB lasers; bit rate; broadening; chirp; data bandwidth; direct modulation; frequency changes; modulating random sequence rate; short time constant; spectral shift; Bandwidth; Bit rate; Chirp modulation; Fiber lasers; Frequency; Optical interferometry; Optical modulation; Optical refraction; Optical variables control; Refractive index;
Journal_Title :
Photonics Technology Letters, IEEE
