MITSUBISHI

MITSUBISHI LASER DIODESML8XX1 SERIESFOR OPTICAL COMMUNICATIONII Far-field patternThe ML8XX1 laser diodes lase in fundamentaltransverse (TEoo) mode and the mode does notchange with the current.They have a typicalemitting area (size of near-field pattern) of 1.0 x1.25 f.J. mo. Fig.7 and 8 show the typical far- fieldpatterns. The full angles at half maximum points(FAHM) are typically 25deg. and 30deg., respectively.00.."~S0.E~.~.!i~Fig. 7 Far- field patternsin plane parallel to hetero junctions (J /I1. or---r-'"T""...,...~--'---"'--r-'"T"""""'''''0.5~50 +50Off-axis angle (deg.)Fig. 8 Far- field patternsin plane perpendicular to heterojunctions (J 1.1.0r-~-r~~~.-~...,...~--~0':sc.S0~"" g.,j0.5OIf- axis angie (deg.)I Pulse responseIn digital optical transmission systems, the responsewaveform and speed of the light output againstthe input pulse current waveform is a mainconcern. In order to shorten the oscillation delaytime, the laser diode is usually biased close to thethreshold current. Fig.9 shows a typical responsewaveform when a rectangular pulse current (rise/fall time is shorter than 0.2ns) is applied.Rise/fall time is typically 0.3ns at Ib = Ith and Po=5mW.s~o "Fig. 9 Pulse response waveformiIb=lth100r--t---:;;;+;;;;7't-"""~~v--r--Po=5mW90 --- -p'":':- ---110 ~ -- ------ --- -----\;ti'­O%~'r-+--+-i--i~~~~~--~~500ps/div2-158