| 摘要 |
PURPOSE:To reduce the influence of a thermal light frequency modulation effect, etc., by keeping the long time mean value of a light frequency used in every route constant regardless of the route. CONSTITUTION:A light frequency allocator 114 is added newly on a light transmitter 11. The similar light frequency allocators are added newly on another light transmitters 12-14. In such a case, (n) pairs of 2n light frequency values (nun, nu-n) (n: natural number) which satisfy nun-nu0=nu0nu-n for a specific frequency nu0 are allocated to one route. At this time, the thermal state of a semiconductor laser can be decided by the mean value of 2n light frequencies without tracking the change of an input current by setting a period to allocate the 2n light frequencies at a sufficiently lower value. Meanwhile, the mean value of the 2n light frequencies can be kept constant at nu0 regardless of an output route. In other words, the mean value of the input currents can be kept constant even when the output route is switched. |
