Advancements in the telecommunication industry have reformed people's lifestyle in the past few decades. Anyone connected to Internet can acquire or disseminate data with a click of a button. The massive volume of data is transferred almost exclusively through optical fibers, which connect continents, countries, and cities together. Optical fibers are also used in datacenters to transfer information bits in short distances with high speeds.
With the phenomenal growth of Internet and the advent of social media, Internet-of-things, and high-resolution movie streaming, the request for data transmission is rapidly increasing. It is predicted that the demand surpasses the limits of current optical systems in the near future. Therefore, it is essential to reconsider the design of conventional optical transmitters and receivers to maximize the performance of fiber-optic systems.
The core of optical fiber is a cylindrically-shaped medium slightly thicker than a human hair made from extremely transparent glass. The light is generated at the source via a laser, traverses the fiber, and is received at its destination. The information is coded into the intensity and/or the phase of the light at the transmitter and is decoded at the receiver. This process of data transmission is not perfect since the light's phase and intensity is disturbed through propagation via noise and interference. These impairments of optical systems limit the rate of data transmission through the fiber.
In this thesis, we study the capacity of fiber-optic channels, i.e., the maximum rate at which information can be transferred reliably through fiber-optic systems. First, an introduction is given to the physics, properties, and impairments of the optical fiber. Then, we compare multiple available models of fiber-optic channel and assess their accuracy. Next, we propose a method to mitigate the effects of nonlinear interference caused by a copropagating optical signal. In the next step, we compare the performance of three different multi-channel optical systems. Finally, we study the capacity of short-haul fiber-optic channels.