Research On Wavelength Selective Optical Switch Based On Digital Optical Phase Conjugation

Due to the invention of modern technologies such as low loss optical fibers,erbium doped fiber amplifiers,and dense wavelength division multiplexing(DWDM),the bottleneck of optical communication networks has shifted from transmission between nodes to switching at nodes.To overcome the latency caused by electro optical and opto electrical conversion and electrical switching at network nodes,optical switching is the key to breaking this bottleneck.In DWDM optical communication networks,multiplexing and demultiplexing must also be performed during optical switching.If traditional optical switches are used in combination with multiplexing and demultiplexing devices,the entire switching system will be very complex and costly.Therefore,a new type of composite optical switch that integrates demultiplexing,multiplexing and optical switching functions is crucial for achieving monolithic integration of the entire optical switching system.This paper proposes a novel wavelength selective optical switch based on digital optical phase conjugation(DOPC).It uses a Roland circle or multimode interferometer(MMI)to decompose the input light wave into multiple single mode waveguides.Then,using distributed Bragg grating(DBG),specific wavelength light waves in each single mode waveguide are selectively reflected,while phase modulation components are used to achieve optical phase conjugation.As a result,the conjugate reflected light wave can be switched to any output waveguide based on the principle of optical reciprocity,thereby achieving wavelength selective optical switching,which is equivalent to performing the functions of demultiplexing,multiplexing and optical switching at the same time.Since DBGs have very high wavelength resolution,compact size,and are easy to integrate,the proposed wavelength selective optical switch has the potential to achieve monolithic integration of the entire large-scale optical switching system.In order to complete the numerical simulation of the optical switch,this paper improves the traditional mode matching method by directly using the numerically absolutely stable Fresnel formula to solve the reflected and transmitted light fields in the longitudinal transmission,and constructing the longitudinal transmission matrix through the eigenmode expansion,avoiding solving the linear equation system for the transmission matrix,matrix inversion operation and numerical instability caused by ill conditioned equation.At the same time,an iterative algorithm is also designed to solve the eigenmode expansion coefficient of each waveguide for different input optical waves.This paper verifies the effectiveness of the improved algorithm through numerical programming simulation on the MATLAB platform.Finally,this paper designs a 16×16 wavelength selective optical switch based on digital optical phase conjugation,and solve the light field distribution during the switching process through numerical programming simulation on the MATLAB platform,as well as verifying the high wavelength resolution and wide spectral range of the designed DBG.In summary,the proposed new type of optical switch based on digital optical phase conjugation opens up a new way to achieve the monolithic integration of the entire optical switching system,and can be widely used in DWDM optical communication networks,bringing new hope for effectively solving the current "electronic bottleneck" of the network nodes.