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What is A VODL?
(Variable Optical Delay Line)
A Variable Optical Delay Line (VODL) is an adjustable photonic component designed to precisely control the time-of-flight or phase shift of a light wave traveling through an optical system. Unlike fixed fiber optic patch cords that provide a static delay based strictly on their physical length, a VODL allows operators to dynamically alter the optical path length on the fly.
Its primary purpose is to synchronize the arrival times of multiple high-speed laser pulses, match optical path distances in interferometers, or fine-tune phase configurations in radar and sensing networks.
HOW Variable Optical Delay Line (VODL) Works
A VODL operates by manipulating the physical distance or refractive index that a light beam must traverse, running through three main structural phases:
Free-Space Beam Expansion
Light traveling through an input optical fiber is directed into the delay line module. It passes through a micro-lens (like a collimator) that transforms the expanding fiber output into a highly stable, parallel free-space laser beam.
Mechanical Distance Adjusting
The parallel free-space beam is directed toward a movable reflective element, such as a retroreflector prism or a high-precision mirror assembly mounted on a motorized translation stage. To increase the optical delay, an electronic command moves the stage further away from the input lens; to shorten the delay, the stage moves closer. Because light travels at a finite speed, changing this physical round-trip distance directly adjusts the arrival time of the light wavefronts.
Fiber Re-Injection
After traversing the extended free-space path and bouncing off the adjustable mirror assembly, the light beam is directed back into a focusing lens (output collimator). This lens focuses the parallel beam back into an output optical fiber core with minimal signal loss, delivering the precisely delayed optical signal to the rest of the network.
