We uniquely produce FSPO Series Fiber Optic Delay Lines featuring low loss, accurate length control, loss compensation, and zero dispersion. Multiple fiber coils are housed in a rack mount enclosure. The fiber is coiled using an advanced fiber winding machine that eliminates internal stress to achieve the lowest loss. The optical loss can be balanced among each fiber loop or compensated with built-in attenuators for short fibers or optical amplifiers for long fibers, respectively. Zero-loss fiber delay lines can be made. Moreover, chromatic dispersion compensation fiber can be used to achieve zero-dispersion fiber optic delay lines. The fiber length thus delays time, is precisely measured and controlled using a special optical interferometer system. The Chromatic dispersion is measured using an Agilent system. These fiber spools provide precise delay time references for radar calibration applications. They can also be used in site diversity applications when system timing is critical. These spools can be used to mimic existing fiber in the ground as a transparent switch between the local and diverse sites. The FSPO Series Fiber Optic Delay Lines are designed for ease of use to provide unmatched performance for radar testing, signal processing, phased array antennas, and phase noise testing.