Variable optical delay lines and methods for making same
View Patent ↗In accordance with the invention, a high-resolution variable optical delay line comprises an optical switch, such as an optical micromechanical mirror switch, and an array of delay fiber paths. Each delay fiber path in the array comprises a region where the fiber is curved differently from the other fibers in the region and a reflector. Each fiber path advantageously comprises other regions where the fiber is essentially parallel to the other fibers in the region. Each fiber is curved differently from the others in order that the fiber paths each provide a different delay.
1. A variable optical delay line comprising:
a plurality of fibers disposed in a closely spaced array, the array comprising a first parallel region, a curved region, and a second parallel region; each fiber having a first end disposed in a first linear array and a second end disposed in a second linear array, the curved regions of the fibers differing in radii of curvature to provide a successive series of monotonically different path lengths, the path lengths differing by a few millimeters or less to provide small delay time increments;
separately switchable reflectors disposed in each of the fibers, the reflectors switchable between reflection and transmission to provide coarse delay increments.
2. The delay line of claim 1 further including a MEMs mirror optical switch optically coupled to the plurality of fibers for switching at least one optical input signal among the fibers of the plurality.
3. The delay line of claim 1 wherein includes a the separately switchable reflectors comprise reflective Bragg gratings.
4. The delay line of claim 3 wherein the reflective Bragg gratings are formed in the second parallel regions.
5. The delay line of claim 1 wherein the plurality of fibers are secured to a substrate of sheet material.
6. The delay line of 1 claim 2 wherein the at least one optical input signal is a single optical input signal and the optical switch comprises a 1×N MEMs mirror optical switch.
7. The delay line of claim 2 wherein the at least one optical input signal comprises a plurality of optical input signals and the optical switch comprises on N×N MEMs mirror optical switch.
8. The delay line of claim 2 wherein the at least one optical input signal comprises a plurality of optical input signals having respectively different wavelengths.