‘Laser’ evolved from the abbreviation of LASER (Light Amplification by Stimulated Emission of Radiation). Laser is a kind of coherent light, with the characteristics of the same frequency, the same vibration direction and the same phase (or the phase difference remains constant). Optical communication system, to a large extent, depends on high quality laser light source.
Laser is the heart of an optical module, and its cost accounts for about 50% of the total cost of an optical module. This article mainly introduces the laser in an optical module. What are the types of lasers in optical modules? VCSEL, FP and DFB are all independent devices. If you want to transmit the light signal, it is driven with or without electric current, which is called Direct Modulated Laser (DML). EML is an integrated device. There are two modules on a chip, one is a laser (L), and the other is an EAM modulator, and these two formed together is called EML.
DFB
DFB (Distributed Feedback Laser) is based on the FP Laser, the Bragg grating is integrated into the active layer inside the Laser (that is, in the gain medium), and the mode selection structure is formed in the resonant cavity to achieve single-mode work. It belongs to the edge emission type and uses the horizontal cavity structure.
DFB generally uses two wavelengths of 1310nm and 1550nm, which can be divided into cooled and uncooled, and is mainly used for medium and long-range transmission. Read more on Types of Lasers for Optical Modules.
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