Fiber Optics Explained Light Sources

Light Sources

    Let’s take some time to discuss the devices that put the “optic” in fiber optic technology- the light sources, or, as they are sometimes referred to, the optic transmitters. Currently, commercially available fiber optic technologies may utilize one of three types of light source- laser, LED, or VCSEL. Below you will find brief explanation of each light source and its given practicalities in fiber optics. 

    Laser (Light Amplification by Stimulated Emission of Radiation)- Didn’t know that was acronym? Well it is, and beyond just being fun to play with, lasers play a crucial role in many fiber systems. In the most basic of terms, lasers work by creating a focused source of one frequency (or color) of light that moves in only one direction. Lasers in fiber optics are valued for their long life spans, high modulation speed (the turning on and off of light), and high-bandwidth capabilities. Lasers do however come at a higher cost and are more difficult to calibrate then other light sources.  

    LED (Light Emitting Diode)- LEDs are small scale, often less than 1mm squared, complex semiconductors. They create light via electron recombination, a process in which electrons recombine with electron holes within the device, releasing light energy. In fiber optics LEDs are utilized for their convenient size, affordable price range, and high luminescence. LEDs are not capable of super high modulation speeds and reach mid-range bandwidths, making them appropriate for multi-mode fiber and relatively shorter cable runs. 

    VCSEL (Vertical Cavity Surface Emitting Laser)- VCSELs (pronounced ‘vixel’) emerged in the 80’s as a new kind of semi-conductor laser and were soon recognized for their potential in fiber optics. When Gigabit Ethernet products were developed LEDs could not modulate (turn on and off) at required speeds and standard lasers proved too expensive- enter VCSEL, which modulates at high speeds at cheaper costs. In turn, multimode fibers that could transmit laser had to be developed, these laser-optimized fibers are the OM3 and OM4 cables that we know and use today. 


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