We all know that optical modules have many types of lasers. FP and DFB lasers are common types of lasers. What is the difference between them?
FP laser
The FP (Fabry-Perot) laser is a semiconductor light-emitting device with the FP cavity as the resonator and emitting 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 rate is generally within 1.25G. FP laser has two wavelengths, 1310nm/1550nm.
There are also some manufacturers in the market to reduce the cost of FP devices to produce gigabit 40km module, in order to achieve the corresponding transmission distance, must increase the emission optical power, long time work ahead of the aging of the product devices, shorten the service life. According to the engineer's suggestion, the dual fiber module of 1.25G and 40km is safer to use DFB devices!
Performance parameters of FP laser:
1) Working wavelength: the central wavelength of the spectrum emitted by the laser.
2) Spectral width: root mean square spectral width of multi-longitudinal mode laser.
3) Threshold current: When the operating current of the device exceeds the threshold current, the laser emits a laser with good coherence.
4) Output optical power: the optical power emitted by the laser output port.
DFB laser
Based on THE FP laser, the DFB laser adopts the grating filter to make the device have only one longitudinal mode output. DFB (Distributed Feedback Laser) generally also USES two wavelengths, 1310nm and 1550nm, which can be divided into refrigeration and non-refrigeration. DFB (Distributed Feedback Laser) is mainly used for high-speed medium and long distance transmission, with the transmission distance generally above 40km.
Performance parameters of DFB laser:
1) Working wavelength: the central wavelength of the spectrum emitted by the laser.
2) Side mode rejection ratio: the power ratio between the laser working main mode and the maximum side mode.
3) -20dB spectral width: the spectral width is reduced by 20dB from the highest point of the laser output spectrum.
4) Threshold current: When the operating current of the device exceeds the threshold current, the laser emits a laser with good coherence.
5) Output optical power: the optical power emitted by the laser output port.
The main difference between FP and DFB laser is that the spectrum width is different. The spectrum width of DFB laser is generally narrow, and it is a single longitudinal mode with distributed negative feedback. The FP laser has a relatively wide spectrum and is a multi-longitudinal mode laser. They also differ in wavelength, threshold current and forward voltage.
I believe you already know something about FP and DFB lasers. As a professional manufacturer of optical modules, HTF hopes that you will not be afraid to put forward your valuable opinions and Suggestions, and hope to make progress together with you. If you need fiber modules, please visit the official website: www.htfwdm.com of HTF or contact the sales: sales2@htfuture.com for consultation!
