Patent ID: 8655165

Claim:
A light transmission device, comprising: an optical switch that switches a reception path of an optical signal where a data signal corresponding to a signal to be transmitted and a subsignal having the wavelength different from the wavelength of the data signal are multiplexed; a subsignal determiner circuit that determines whether the subsignal is included in a received optical signal, when the data signal is not included in the received optical signal; a switch control processor that maintains a connection path of the optical switch without switching the connection path, when it is determined by the subsignal determiner circuit that the subsignal is included; an information storage unit that stores switching permission information and failure detection information in association with a combination of an input power level of the data signal and an input power level of the subsignal, the switching permission information indicating whether or not to permit switching of the optical switch of a downstream node irrespective of the existence of failure detection, the failure detection information urging, when the failure is detected, the switching of the optical switch of the downstream node; a subsignal generator circuit that specifies the switching permission information and the failure detection information based on the combination of the input power level of the data signal and the input power level of the subsignal which are included in the optical signal received from an upstream node, and generates the subsignal including the specified switching permission information and the specified failure detection information; and a signal transmitter that transmits the optical signal where the subsignal generated by the subsignal generator circuit and the data signal are multiplexed to the downstream node.