Fiber optic dual delay line for a multi-mode radar test target simulator

A fiber-optic delay line has been designed for a multimode radar test target simulator. This delay line, operating between 3.0 and 3.6 GHz, has a fixed delay of 30 mu s. Low transmission loss has been achieved using reactive matching techniques and a GRIN lens for optical coupling of the laser to the fiber. The transmission gain of a link consisting of the transmitter and the receiver, connected with a short length of single-mode fiber, is -17 dB at 3.3 GHz with 1-dB variation across the band. It is estimated that the gain of the delay line will be -20 dB due to the additional loss of 3 dB from 6.2 km of optical fiber. These results show a significant improvement in transmission gain, and can improve the noise figure and dynamic range characteristics over commercially available wideband delay lines.<>