OPTICAL TRANSMISSION LINE CHANGEOVER DEVICE

摘要

PURPOSE:To change over a 1st optical transmission line into a 2nd transmission line uninterruptibly without any bit error by attenuating the signal light of the 1st optical transmission line and amplifying a signal light of the 2nd optical transmission line. CONSTITUTION:Part of a signal light propagated through an optical fiber 2 is branched at a coupler 4 to an optical fiber 5, and a variable attenuator 10 attenuates a signal light propagated through the optical fiber 2 and amplifies the signal light propagated through an optical fiber 5 at an optical amplifier 9 simultaneously thereby interrupting the signal light propagated finally through the optical fiber 2. The optical amplifier 9 and the variable attenuator 10 have no polarized wave dependency and they are operated interlockingly. Thus, the signal light propagated through the optical fiber 5 is increased corresponding to the attenuation of the signal light propagated through the optical fiber 2 at the changeover. Moreover, since the state of a polarized wave is not changed due to the intensity of the signal light, the signal light intensity received by an optical receiver 3 is always constant.