All-fiber 3/spl times/3 acousto-optic switch

Summary form only given. We have previously made an all-fiber 2/spl times/2 acousto-optic switching element from a fused coupler. Here we describe a similar 3/spl times/3 switch. Two of three identical fibers are narrowed (pre-tapered) by different amounts, before all three are fused and elongated together to form the coupler. If the three diameters are sufficiently different, the result is a "null" coupler; light of any wavelength entering in a particular fiber will leave the coupler from the far end of the same fiber.