| 摘要 |
PURPOSE:To take out a signal of the arbitrary wave length stably all the time even when a light input signal or the central wave length of a filter is changed by controlling the filter based on a beat signal of a direct current light emitted by the filter and a light signal which does not pass the filter. CONSTITUTION:An electric current source 2 is connected to a gain control terminal of a light wave length variable filter 1 and decides the gain. A separator 3-1 puts in a part of a light input signal to a combiner 4 and puts in the remainder to the light wave length variable filter 1. A separator 3-2 puts in a part of an output light of the light wave length variable filter 1 into the combiner 4 and takes out the remainder as a light output signal. The combiner 4 combines the light signals from the separators 3-1 and 3-2, and the output signal is put into an O-E converter 5 for converting this to an electric signal. Moreover, a beat detector 6 detects from the output signal of the O converter 5 a beat generated from a difference between the wave length of an arbitrary signal and the wave length of the output light of the filter 1. A voltage current converter 7 converts a wave length selection control signal and a voltage to which a beat detection output is added to an electric current and flows it to a wave length control terminal of the filter 1 as a wave length control current. |
