Studies On Tunable Multi-Wavelength Laser For Optical True Time Delay System

Optical true time delay(OTTD)is a principal technology in optically controlled phased array radar systems,which aims to provide radar systems with a wide range,high accuracy,and flexible time delay tuning.As the core component,light source determines the working principle and main parameters of the OTTD system.This paper studies the frequency spacing tunable multi-wavelength laser(FS-TMWL)for the OTTD system by external cavity modulation using a recirculating frequency-shifting loop(RFSL).Multi-wavelength output of the light source with precisely tunable frequency interval is realized by controlling the RF signal.Wide range and flexibly precise control of the time delay can also be realized by using this FS-TMWL.The main work of this article is as follows:1.Theoretical study of optical true time delay system based on FS-TMWLThe working principle of OTTD system based on FS-TMWL is theoretically studied.The influence of the frequency interval tuning range,tuning relationship with time,tuning accuracy and frequency components number of FS-TMWL on the tuning range,tuning relationship with time,tuning accuracy,and deviation of the time delay of the OTTD system are analyzed theoretically respectively.2.Research on RFSL-based tunable multi-wavelength light sourceThe working principle of FS-TMWL based on RFSL is studied theoretically.The FS-TMWL is constructed using RFSL loop,and the FS-TMWL frequency interval can be the tuned flexibly in the range from 10 MHz to 20 GHz with tuning accuracy increases up to the order of Hz.The effects of accumulated spontaneous emission noise on FS-TMWL are studied experimentally.And the factors affecting the number of FS-TMWL output frequencies are analyzed.3.Research on OTTD system based on FS-TMWLA tunable range from 61.84 ps to 119.71 ps of the time delay of the OTTD system is achieved by using the FS-TMWL.The frequency interval of FS-TMWL is tuned from 5GHz to 14 GHz in a sinusoidal form with time to achieve a sinusoidal tuning of time delay,thereby linear scanning of the radar beam pointing angle can be achieved.The time delay tuning accuracy of the OTTD system is measured and analyzed experimentally,which can be 5.11 ps.The main factors of jitter in the time delay of OTTD system are analyzed.