Nonlinear distortion reduction techniques in transistor lasers for analog fiber optic communication applications

Abstract

Now a days, in order to improve the today s communication technology with large bandwidth, better reliability and long distance, the coaxial cables are replaced by optical fiber. Generally, the optical source used in the optical transmitter is laser diode. Due to fast recombination lifetime and increase in modulation bandwidth, the laser diode can be replaced by Transistor Laser (TL). TL is a three terminal device and it performs the operation of both laser diode as well as transistor. Light emission is achieved in the TL due to the insertion of quantum well (QW) in the base region. For a single electrical input, optical and electrical outputs are obtained at the base and collector of TL respectively. TL can be used in various applications such as signal mixing, frequency multiplication, optoelectronic logic gates and Radio over Fiber (RoF). The main advantage of TL over laser diode is it can operate both in current and voltage modulation. Further, the performance of TL is improved based on introducing a tunnel injection in TL. In this scheme, the carriers are directly injected to the QW which leads to increase the electron hole pair recombination with fast recombination lifetime. newlineRF signal is modulated and transmitted over the optical fiber in ROF technology. TL has a great impact to use as an optical source in RoF system. The overall performance of the system depends on the RF-to-RF link efficiency. However, nonlinearity of optical source and detectors is one of the major concerns to consider the performance of the system. The nonlinear distortion components such as harmonic and intermodulation distortion will fall on the main signal band and affect the overall performance. Therefore, it is very important to suppress these distortion components using various distortion reduction techniques. newline