| 摘要 |
PURPOSE: To produce a large number of devices having substantially same characteristics by taking the reducing correlation of the symmetric mode light passing through a central multimode optical waveguide with asymmetric mode light. CONSTITUTION: A central multimode optical waveguide 52 is planned so that the transmission time lag between the symetric mode light passing through the waveguide and asymmetric mode light becomes max. The symmetric mode signal and asymmetric mode signal within the waveguide 52 are correlated at a start point of time but, when both signals advance through a multimode part 54 through an integrated optical coupler (node) 22, one of them is delayed with respect to the other one of them and both signals do not interfere with each other when reach a multimode output terminal 58. Next, a taper part 66 reduces the loss of light into a substrate 51 to allow the light to pass through the substrate 51 without propagating the asymmetric mode signal. Since the asymmetric mode signal is reduced in correlation until it reaches the multimode output terminal 58, an phase error is not induced and the bias error within the output signal of the optical circuit of a detector 44 can be largely reduced. |
