External modulation technology, with the laser working in direct current, has the advantage of no laser chirp, low dispersion distortion, large extinction ratio, and high speed. It also has the disadvantage of high cost and high difficulty in manufacturing.

Direct modulation will lead to high laser chirp (Laser's bias current is modulated by signal and the optical spectrum shifts and shakes). Laser chip will interact with dispersion effect caused by standard single mode fiber (SMF-28), which will generate serious distortion in the place of 1550nm. This kind of distortion will become more serious with the increase of transmission distance, bandwidth and channel number.

At present, international high performance 1550nm direct modulation has no obvious performance inferior while transmitting an analog and digital multiplexing full channel signal with transmission distance ≤ 15Km or transmitting digital load with transmission distance ≤ 40Km.

Huatai HT1500E is a kind of 1550nm direct modulation optical transmitter built-in EDFA. It adopts high linearity, low chirp DFB laser, built-in pre-distortion compensation and APC, ATC closed loop control. A built-in low noise EDFA can supply 1~8 way, 13~17dBm output power. It can be used in FTTx ( ≤ 10Km) of second-grade service area (Sub-HE), also can be used in WDM narrow band multiplex and IP/QAM.

HT1500EC: CATV wavelength.

HT1500EU: ITU standard wavelength.

 Low chirp, high linearity DFB laser, chirp compensation.

 Dual module RF driver , high efficient laser pre-distortion adjustment.

 Perfect APC, ATC closed loop control

 Intuitionist modulation status display.

 Built-in dual power supply back-up, switch automatically.

 Casing temperature auto-control, ensure the long life of the laser.

 Provide IPTV, VOD value-added service in second-grade service area (Sub-HE).
         Analog digital mixed transmit <15Km. (common distance ≤ 10km). 
        Pure digital load <40Km.

 WDM narrow band multiplex >70Km.