With the increasingly widespread application of optical communication technology in modern social production and life, the application scenarios of optical communication technology are becoming increasingly diverse and challenging. In energy sensitive scenarios such as data centers and aerospace, traditional digital coherent optical communication reception methods are difficult to reduce complexity and power consumption, and have obvious limitations. Analog coherent technology is a simplified coherent technology that utilizes analog devices to achieve part or all of the functions of the traditional digital coherent optical communication receiver, in order to simplify the receiver structure and reduce power consumption. Compared to traditional digital coherent optical communication receiving technology, analog coherent technology has obvious advantages in power consumption, complexity, and cost. This paper first introduces the typical architecture of analog coherent technology and demonstrates its main components. Then, the principles, specific structures, and implementation methods of each part are specifically introduced, including clock and carrier recovery, optical domain polarization demultiplexing (polarization rotation compensation), and analog adaptive equalization. Finally, other simplified coherent technology similar to analog coherent technology are introduced, including quasi coherent reception technology, Kramers-Kronig (KK) reception technology, and differential reception technology. Through the analysis of the principles and current research status of analog coherent and other simplified coherent techniques, this paper compares the advantages and disadvantages of various simplified coherent methods, elucidates the future development directions of simplified coherent technology, and provides a reference for future research on simplified coherent technology.