| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable optical attenuator capable of automatically setting an optimum attenuation. SOLUTION: The light intensity I<SB>n+1</SB>of emission light L2 after attaining a voltage V<SB>n+1</SB>is detected in an intensity detection means 20, and whether or not the increasing/decreasing direction of the voltage V<SB>n+1</SB>coincides with the attenuation direction of the light intensity I<SB>n+1</SB>is determined in an error determination means 40. In this case, whether or not the light intensity I<SB>n+1</SB>is larger than the light intensity I<SB>n</SB>(I<SB>n+1</SB>>I<SB>n</SB>) when V<SB>n+1</SB>(=V<SB>n</SB>-ΔV) is supplied, or whether or not the light intensity I<SB>n+1</SB>is smaller than the light intensity I<SB>n</SB>(I<SB>n+1</SB><I<SB>n</SB>) when V<SB>n+1</SB>(=V<SB>n</SB>+ΔV) is applied is determined. When the increasing/decreasing direction of the voltage V<SB>n+1</SB>coincides with the attenuation direction of the light intensity I<SB>n+1</SB>, it is determined that it is used in a using region TR2 and is normal. Meanwhile, when the increasing/decreasing direction of the voltage V<SB>n+1</SB>does not coincide with the light intensity I<SB>n+1</SB>, it is determined that normal attenuation by the variable optical attenuator 10 is not being performed and an alarm is outputted. COPYRIGHT: (C)2010,JPO&INPIT |
