Title :
Electroabsorption modulated laser for long transmission spans
Author :
Salvatore, Randal A. ; Sahara, Richard T. ; Bock, Michael A. ; Libenzon, Ilya
Author_Institution :
Corning Lasertron, Bedford, MA, USA
fDate :
5/1/2002 12:00:00 AM
Abstract :
Strain-compensated AlGaInAs quantum-well electroabsorption modulated lasers (EMLs) transmit at 10 Gbits/s on uncompensated transmission spans of >75 km of standard fiber and >225 km of MetroCor fiber. Details of the design, fabrication, and testing are presented. A complex-coupled distributed feedback (DFB) grating is used to enable high output power. The epitaxy and chip structure are described. The paper studies what is needed to accomplish long-span transmission in terms of minimum physical requirements for laser mode control, facet reflection, index grating strength, laser-modulator matching, laser-modulator electrical isolation, modulator extinction ratio, modulator capacitance, linewidth enhancement factor, etc. The interaction of the modulator with the laser is analyzed and a requirement for this structure is computed for the electrical isolation resistance between modulator and laser contacts. Stability of the laser source is discussed and a method is derived for determining the grating´s gain-coupling coefficient at operating power. Chirp due to the modulator is analyzed. Nonzero chirp of the modulator is shown to have beneficial impact on the quality of the signal after transmission. The effect of a bias-dependent alpha parameter is analyzed. Because bit-error rate is a strong function of mean alpha parameter and not a strong function of the range of alpha during nonreturn-to-zero modulation, we determine that tuning the chirp of the EML modulator to suit different fiber types (MetroCor, SMF-28, etc.) is practical. Specific tradeoffs are also required. Experimental results verify the analysis
Keywords :
III-V semiconductors; aluminium compounds; chirp modulation; distributed feedback lasers; electro-optical modulation; electroabsorption; gallium arsenide; indium compounds; integrated optoelectronics; laser stability; optical communication equipment; quantum well lasers; 10 Gbit/s; 225 km; 75 km; AlGaInAs; DFB grating; MetroCor fiber; bias-dependent alpha parameter; bit-error rate; chip structure; complex-coupled distributed feedback grating; design; electrical isolation resistance; electroabsorption modulated laser; epitaxy; fabrication; facet reflection; gain-coupling coefficient; high output power; index grating strength; laser contacts; laser mode control; laser-modulator electrical isolation; laser-modulator matching; linewidth enhancement factor; long transmission span; long-span transmission; mean alpha parameter; modulator capacitance; modulator extinction ratio; nonreturn-to-zero modulation; operating power; standard fiber; strain-compensated AlGaInAs quantum-well electroabsorption modulated lasers; testing; uncompensated transmission spans; Chirp modulation; Distributed feedback devices; Fiber lasers; Gratings; Laser feedback; Laser modes; Laser stability; Laser theory; Optical fiber testing; Quantum well lasers;
Journal_Title :
Quantum Electronics, IEEE Journal of