Optical communication in space faces significant challenges due to atmospheric effects such as absorption, scattering, and turbulence, which degrade signal quality and link reliability. This paper provides a comprehensive survey of these challenges and mitigation techniques for ground-to-satellite, satellite-to-ground, and inter-satellite optical communication links. It discusses various impairments affecting performance, including atmospheric turbulence, which can severely impact bit error rate (BER) and link feasibility. The paper also reviews techniques at physical, link, network, and transport layers to combat these effects, with a unique focus on orbital angular momentum (OAM) for enhancing capacity in space-based optical links. It highlights the use of FSO for high-capacity backhaul solutions and discusses the advantages of FSO over RF communication, such as high bandwidth, lower power and mass requirements, and unlicensed spectrum usage. The paper also addresses the choice of wavelength in FSO communication, emphasizing the trade-off between receiver sensitivity and pointing bias. It covers various factors affecting FSO performance, including fog, rain, snow, and atmospheric turbulence, and presents empirical models for turbulence profiles. The paper concludes with an overview of future research directions and the importance of adaptive techniques for reliable space-based optical communication.Optical communication in space faces significant challenges due to atmospheric effects such as absorption, scattering, and turbulence, which degrade signal quality and link reliability. This paper provides a comprehensive survey of these challenges and mitigation techniques for ground-to-satellite, satellite-to-ground, and inter-satellite optical communication links. It discusses various impairments affecting performance, including atmospheric turbulence, which can severely impact bit error rate (BER) and link feasibility. The paper also reviews techniques at physical, link, network, and transport layers to combat these effects, with a unique focus on orbital angular momentum (OAM) for enhancing capacity in space-based optical links. It highlights the use of FSO for high-capacity backhaul solutions and discusses the advantages of FSO over RF communication, such as high bandwidth, lower power and mass requirements, and unlicensed spectrum usage. The paper also addresses the choice of wavelength in FSO communication, emphasizing the trade-off between receiver sensitivity and pointing bias. It covers various factors affecting FSO performance, including fog, rain, snow, and atmospheric turbulence, and presents empirical models for turbulence profiles. The paper concludes with an overview of future research directions and the importance of adaptive techniques for reliable space-based optical communication.