External modulation technology laser working with direct current, has no laser chirp. It has advantage of no chromatic dispersion distortion, large extinction ratio, high speed and disanvantage of high cost, high difficulty in producing.
Direct modulation will lead to high laser chirp (laser's bias current will be modulated by signal, opercal spectrum will shift and shake),Laser chip will interact with dispersion effect caused by standard single mode fiber (SMF-28); it generates serious distortion. laser chip effect will occur high distortion in 1550nm. This kind of distortion will become more serious companied with the increase of transmission distance, bandwidth and channel number.
At present, internationally, high featured 1550nm direct modulation has no obvious feature inferior, when transmitting a analog and digital multiplex full channel signal, transmission distance≤15Km or digital load with transmission distance≤40Km.
Starshine SE1500A is a kind of 1550nm direct modulation optical transmitter, standard and AGC function. It adopts high linearity, low chirp DFB laser, bulid-in pre-distortion compensation and closed loop AGC, APC, ATC control, obviously improve the system index. It can be used in second service area (sub-headend) FTTx (≤10Km), also can be used in WDM narrow band multiplex as well as IP/QAM.
SE1500AC: CATV wavelength
SE1500AU: ITU standard wavelength
※ Main application
Second service area (sub-headend) provide IPTV, VOD value-added service.
Analog digital mixed transmit <15Km.
Pure digital load <40Km.
WDM narrow band multiplex >70Km.