Abstract: 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 2×2 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.

Abstract: A wavelength-division multiplexing passive optical network (WDM-PON) comprising a central office for generating monitor light and multiplexed downstream optical signals to be out and detecting upstream optical signals, the central office including a signal monitoring unit monitoring based on fed-back monitor light if the wavelengths of the upstream optical signals and the wavelengths of the downstream optical signals change, a plurality of subscriber units for detecting corresponding downstream optical signals and generating upstream optical signals, a remote node for reflecting the monitor light to the central office, de-multiplexing multiplexed downstream optical signals so as to output the downstream optical signals to the corresponding subscriber units, and multiplexing the upstream optical signals so as to output the upstream optical signals to the central office, a first optical path for linking the central office to the remote node, and a plurality of second optical paths for linking the remote node to