Laser nonlinearity reduction model using taylor series expansion for free space optical communication system

Abstract

One primary limitation on the performance of the optical transceiver is the nonlinearity of the laser transmitter, which produces intermodulation distortions and necessitates various compromises between modulation depth, channel spacing and types of modulation scheme, leading to degraded bandwidth efficiency. Nonlinearity of a directly modulated laser diode imposes limitations in the performance of the optical communication systems. Many laser linearization techniques involve the use of duplicate lasers or optical modulators, and those, which attempt to create physical structures within the optical modulators, and lasers can obviously increase the cost relative to ordinary optical transmitters. Fundamentally, linearization techniques can be divided into one of the following categories: feedforward, feedback, precorrective distortion. In this chapter a new free space optical link non-linearity correction system has been introduced employing the Feedforward Linearization technique, so called Optical Free Space Feedforward Linearization System (OFFLS). The system was modeled by Taylor series and the results of the simulations have shown a significant reduction in the 3 th and 5 th order intermodulation distortion products (IMD) by 30 dB over 2GHz bandwidth.