Implementation of photonic true time delay using high-order-mode dispersion compensating fibers

We demonstrate the advantageous use of highly dispersive (>450 ps/nm·km), high-order-mode (HOM) fiber modules for true time delay applications. Along with their low insertion loss, very low phase ripple (root mean square <0.3° over 0-20 GHz), and high immunity to nonlinear effects, the high dispersion values facilitate the construction of devices with relatively short fibers, resulting in improved tolerance of the radio frequency delay to thermal changes. The implications of multiple path interference effects in HOM modules are also studied and shown to be very small.