Research On High Precision Optical Delay Line Design Application

Optical delay technology has been applied in optical phase shifting network of Phased Array Radar. It solves the problem of aperture effect and beam deflection phenomenon existing in traditional phased array antenna. The application brokthrough the limitations in operating frequency and bandwidth caused by the electron beam forming system. The delay precision and the consistency of loss of optical delay technology, which determine the pointing accuracy and anti-jamming performance of the beam of an antenna, is the key technical specifications of optical delay technical solutions. Optical delay technical solutions based on fiber or high dispersion fiber or fiber grating, etc. can’t satisfy requirements in small size, light weight and other aspects brought about by the phased array antenna’s development with a higher frequency,more accuracy, larger bandwidth, etc. However, optical delay technical solution based on silicon waveguide is the most potential technology in development and application because the advantages of waveguide technology promise it more accuracy, small size,light weight as well as compact stable structure.And this paper has mainly researched the structural design of an optical delay technical solution based on silicon waveguide with small volume, low-loss and high-precision. And it provides some theoretical foundation, a design approach for reference and a feasible optical delay technology solution consist of spiral silicon optical waveguides and Y-branch waveguide.Specifically, this paper has analyzed the characteristics of several typical optical delay technical solutions in the background of optically controlled phased array radar,and has introduced some current situation of the silicon waveguide for the advantages of optical delay technology solutions based on silicon-based waveguide in aspects of precision, volume, cost, structure, etc. Then based on the beam-forming theory of phased array and statistical theory, this paper has analyzed the effect of delay precision and consistency of loss of optical delay technology on the pointing accuracy and electronic level performance of the beam of an antenna with different number of array elements and different operating frequency. Then based on the theory of equivalent index method, finite difference beam propagation method and transparent boundary conditions, this paper has analyzed the effect of the structure parameters of SOI,Si3N4 rib waveguide and silica channel waveguide and material parameters on bending radiation loss in detail with Rsoft and Matlab software, and has analyzed the effect of the structure parameters of rib waveguide on waveguide dispersion, and has analyzed the effect of the space between parallel SOI, Si3N4 rib waveguide and silica channel waveguide on coupling length.Finally, based on the simulation above, this paper has complete a design of 2bit high-precision passive optical delay technology solution consist of Si3N4-based spiral ridge waveguide delay lines and cascade Y-branch waveguide structure with specific structural parameters. The radius of Spiral waveguide center is 2mm, interval between the adjacent waveguide outside the spiral center is6μm.The bending loss of the spiral rib waveguide is 0.2dB, and the Y-branch 3dB. The dispersion at 1550 nm is 3.147 ps / nm.km. The loss consistency of each pathway is good and delay precision reaching subpicosecond taking the process advantages of waveguide.The of length 5ns’ delay line is 0.7571 m, footprint of which is only 98.5mm2, and 3m long delay line only 206.6mm2.