Semiconductor Optical Amplifier (SOA) With the growing popularity and usage of optical technology in the field of telecommunication, there is a critical need for more reliable signal transmission optical channels. As telecommunication aims to shorten distances, long distance transmission is greatly susceptible to attenuation losses. In order to cater to this, the conventional method relied on converting the optical signals to electrical ones and vice versa. The advent of optical amplifiers however was able to remedy this problem. Today, our technology and its operations are primarily dependent on three main types of optical amplifiers.
Erbium Doped Fiber Amplifier (EDFA) Semiconductor Optical Amplifier (SOA) Linear Optical Amplifier (LOA)
While the initial success of EDFA was far greater than that of SOA’s, the revolution of SOAs has brought forth a new window of successful technological innovation. Currently, the most vastly used amplifiers are the SOAs which function as an LOA. This innovative technology has been able to resolve a multitude of issues associated with SOAs including cross talk and high SNR (Signal to Noise Ratio). Structure of SOA The SOA has a basic laser diode structure to enable amplification of optical signals which are passed through the structure’s optical region. Stimulated emission in the active region accounts for amplification. The same is shown below:
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Amplification in SOA As visible from the structure shown above, carriers are injected into the active region of an SOA via an external current source. This results in holes in the valence band (VB). In other words, the injection current is able to create a carrier density in the conduction band which is then responsible for optical transition from the conduction to the valence band. If the density of the carriers exceeds that of the transparency carrier density then an optical gain is said to have occurred. In this case, the device can be used to amplify signal through stimulated emission. SOAs find massive application in telecom systems, especially in fiber pig-tailed components. An SOA is considered as the preferred choice for industrial usage because it makes use of direct electrical drive current which in actual is a more robust structure as compared to lasers. In addition, the SOA can operate on a switching speed ranging from 0.5 to 5 GHz. This indicates that the switching characteristics and tolerance of SOAs are far better than other types of amplifiers. What’s more is that an SOA will be able to operate at a Bi-error rate of 10-15 which is the lowest rate. As compared to other amplifier types, SOAs offer better bit error rate properties. For instance, an EDFA is continuously subject to worsening BER from one channel to another. This is not the case with SOAs. Reference http://www.researchomatic.com/Semiconductor-Optical-Amplifiers-141486.html
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