| 摘要 |
PROBLEM TO BE SOLVED: To obtain an add/drop circuit which does not make its operation unstable because of resonance, etc., by providing an optical isolator operationally connected between first and second fiber gratings. SOLUTION: The optical signals of wavelength λ10 and λ10 are inputted from a port 2 to the port 10A of an optical circulator 10. The inputted optical signal is given from a port 10B to a fiber grating 12. The optical signal of the wavelength λ10 is reflected by the fiber grating 12, passes through the ports 10B and 10C in this order, and is outputted from a port 4 as drop light. The optical signal of λ20 is transmitted through the fiber grating 12 and passes through an optical isolator 14 and a fiber grating 16 in this order to be supplied to the port 18A of an optical isolator 18. As the optical isolator 14 is inserted between the fiber gratings 12 and 16, there is no such fear that the resonance of light between the fiber gratings 12 and 16 occurs. |
