摘要 |
A pair of optical couplers are arranged in series with a pair of outputs from the first optical coupler supplying the pair of inputs to the second optical coupler. At least one of the optical fibers between the first and second couplers is arranged to have a variable length, said variation being at least one-half the wavelength of the light signal utilized within the system. When light is supplied to one input of the first coupler, this light can be switched selectively to either of the outputs of the second coupler by varying the length of one of the optical fibers between the couplers. Thus, a light signal supplied to either of the inputs of the first coupler can be selectively output at either of the outputs of the second coupler or can be made to alternate between these outputs in accordance with the length of the intervening optical fiber. |