Lasers are the core devices of optical transceivers, which injecting current into semiconductor materials and injecting laser light through the photon oscillations and gains in the resonator. At present, the most commonly used lasers are VCSEL, FP, and DFB laser. The difference between them is that semiconductor materials and resonator structures. DFB lasers are more expensive than FP lasers. The optical modules of transmission distance within 40km generally use VCSEL, FP lasers; transmission distance ≥ 40km generally use DFB lasers. Do you know all the transceiver laser types? Let us learn this knowledge.
LED Laser
Light-emitting diode referred to as LED. Made of a compound containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N). Visible light is emitted when electrons recombine with holes and thus can be used to make light emitting diodes. In the circuit and equipment as a light, or composed of text or digital display. Gallium arsenide diode red, gallium phosphide diode green, silicon carbide diode yellow, gallium nitride diode blue. Due to the chemical nature of organic light-emitting diode OLED and inorganic light-emitting diode LED.
For optical fiber communication systems, LEDs are the best light source of choice if the multimode fiber is used and the bit rate is under 100-200Mb/s while only requiring input optical power of tens of microwatts. Compared with the semiconductor laser, because the LED does not need thermal stability and light stabilization circuit, so the LED drive circuit is relatively simple, its production cost is low, high yield LED emission spectrum line light, poor directivity, its own response speed Slow, so only for the lower speed communication system. The LED laser commonly used in 155M 1×9 multimode transceivers.
VCSEL Laser
Vertical-Cavity Surface-Emitting Laser (VCSEL) is a type of semiconductor laser whose laser is perpendicular to the top surface It is made of a separate chip that is generally cut with a slit, and the edge-emitting laser is different from the edge-emitting laser. VCSELs typically use 850nm wavelengths for short-range transmission of Gigabit Ethernet to 10GbE SR multimode fiber.
VCSEL laser has many advantages over edge-beam lasers in the production process. Edge-beam lasers cannot be tested after production. If an edge-emitting laser does not work, it is a waste of processing time and material processing time, either because of poor contact or poor material growth. However, VCSEL can be tested its quality and troubleshoot any manufacturing process. For example, if the paths between the dielectrics are not completely and cleanly connected, the top metal layer is not in contact with the test metal layer during the pre-packaged test and the test result is incorrect. Further, since the laser light emitted from the VCSEL is perpendicular to the reaction zone, and edge emitting laser light emitted in parallel to the reaction zone contrary, there can be tens of thousands of VCSEL to be processed on a three-inch large gallium arsenide chip simultaneously. In addition, even though VCSELs require more labor and finer material in the manufacturing process, more predictable production results can be controlled.
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