FP laser
FP (Fabry Perot) laser is a kind of semiconductor light-emitting device which uses FP cavity as resonator to emit multi longitudinal mode coherent light. FP laser is mainly used for low speed and short distance transmission. For example, the transmission distance is generally within 20 km, and the speed is generally within 1.25g. FP laser has two wavelengths, 1310nm / 1550nm.
The performance parameters of FP laser are as follows
1) Working wavelength: the central wavelength of laser spectrum.
2) Spectral width: root mean square spectral width of multi longitudinal mode laser.
3) Threshold current: when the working current of the device exceeds the threshold current, the laser emits a coherent laser.
4) Output optical power: the optical power from the laser output port.
DFB Laser
DFB laser is based on FP laser and uses grating optical filter to make the device have only one longitudinal mode output. DFB (distributed feedback laser) generally uses two kinds of wavelengths, 1310nm and 1550nm, which are divided into refrigeration and uncooled. It is mainly used for high-speed, medium and long-distance transmission, and the transmission distance is generally more than 40km.
The performance parameters of DFB laser are as follows：
Working wavelength, side mode suppression ratio (power ratio of main mode to maximum side mode of laser), and
-20dB spectral width (the spectral width is reduced by 20dB from the highest point of laser output spectrum), threshold current and output optical power.
