Patent ID: 6795596
Filing Date: 2004-09-21
Classification: G02B,G02F,H04B

Abstract:
A variable optical signal delay line, comprising:at least a first input (16) and at least a first output, a first phase shifter stage coupled to said first input and having a first phase shifting element, a first delay stage that is connected to the first phase shifter stage and has a second phase-shifting element, and a second phase shifter stage, coupled to said first output, connected to the first delay stage, and having a third phase-shifting element, wherein the first phase shifter stage, the first delay stage and the second phase shifter stage are each constructed in the fashion of a Mach-Zehnder interferometer with a beam divider and a first and a second arm, wherein the first, second and third phase-shifting elements are tuned by means of a respective phase controller in the second arm of each said interferometer, so that the ratio of the optical power in the first arm to the sum of the optical powers in the first and second arms in each said interferometer is equal to a setpoint value R1, R2 and R3, respectively, wherein R1 for the first phase controller is set between 0 and 1, R2 for the second phase controller is set to about 0.5, and R3 for the third phase controller is set to about 0.99, and wherein only the setpoint value R1 of the first phase-shifting element is varied so that the signal delay lies between 0 and a delay produced by said first delay stage, and the setpoint values R2 and R3 of the second and third phase-shifting elements are fixed.