An optical telecommunication system with automatic channel switching is disclosed. The system is provided with two symmetrical fiber channels and two subsystems. Each subsystem is formed by two 2.times.2 optical switches that are connected to each end of the primary and secondary channels, including an input light source, an optical receiver, multiple fiber optic power meters, and a control circuit. Data signals are normally sent over the primary channel, while test signals are passed through the secondary channel. The fiber optic power meters are connected to the receiving ends to monitor the power level of transmitted signals over the two channels simultaneously. If a line disconnection is detected, the control circuit automatically initiates a channel switching between the primary channel and secondary channel, and yet optical signals are transmitted and received transparently with high efficiency and reliability.