PURPOSE: To provide a small sized/small loss/low cost depolarization circuit by which narrow line width light used in the present optical communication can be depolarized easily. ;CONSTITUTION: In a depolarization circuit to create signal light having a small degree of polarization, the circuit is provided with a polarization separating optical element 2 to separate input light L1 into the first polarized wave component P1 and the second polarized wave component S1 being orthogonal to each other, the first optical path 3 to propagate the first polarized wave component P1 while holding the polarized wave surface of the first polarized wave component P1 of the input light L1 from the polarization separating optical element 2, the second optical path 4 separated spatially from the first optical path 3 so as to propagate the second polarized wave component S1 while holding the polarized wave surface of the second polarized wave component S1 of the input light L1 from the polarization separating optical element 2, a polarization synthesizing optical element 7 to synthesize the first polarized wave component P1 and the second polarized wave component S1 propagated respectively through the first optical path 3 and the second optical path 4 and attenuation applying means 5 and 6 arranged at least in either of the first optical path 3 and the second optical path 4.;COPYRIGHT: (C)1993,JPO&Japio
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