To obtain a device capable of mitigating the required condition of a BPF for removing spontaneously radiated noise light and sweeping a wide band and precise light frequency by using plural optical ring circuits and arranging the narrow band band-pass filters(BPF) in the respective optical ring circuits to provide a transmission central frequency with a difference.
Plural optical ring circuits are used and narrow band BPFs 5 are arranged in the respective optical ring circuits to provide a transmission central frequency with a difference. That is, in a k-th optical ring circuit, a light pulse of a light frequency f0+ΔF1+...+ΔFk frequency shifted to a high frequency side by ΔFk is inputted to a k+1-th optical ring circuit and that is repeated. The transmission central frequency of the BPF 5 of the k+1-th optical ring circuit is set so as to become higher by ΔFk than the transmission central frequency of the BPF 5 of the k-th optical ring circuit. A part of the energy of the light pulses circulating the respective optical ring circuits is taken out from frequency sweep light output ports 6 of light frequency shifters 7 and are multiplexed to be outputted as a wide band frequency sweep light.
YAMAMOTO FUMIHIKO
HORIGUCHI TSUNEO
