Design And Realization Of Special Optical Fibers For Space Division Multiplexing Communication Systems

The capacity of the traditional single-mode optical fiber communication system is limited by the non-linear Shannon limit,which cannot meet the demand for the continuously increasing bandwidth of the communication network in the future.As a new breakthrough to alleviate the bandwidth crisis,space division multiplexing techniques are of significant research interests,as the basis of which high performance specialty fibers have become an international research hot spot in recent years.Under this background,this dissertation focuses on the research of multi-core optical fibers,few-mode optical fibers and disordered optical fibers used in space division multiplexing communication systems,with the achievements listed as follows:?1?The method and technology of fiber designing,manufacturing and testing for multi-core optical fibers are well studied.?a?Taking use of finite element method,the design of 7-core communication optical fiber with trench structure is studied,as well as the influence of trench structure on the core-to-core crosstalk is analyzed.?b?A 7-core communication optical fiber with deep trench is designed,yielding a core-to-core crosstalk of less than-45dB/100km.Explore the arts of manufacturing of multi-core optical fiber based on stacking method and drilling method,and finally realize the scale production of high performance 7-core communication fiber?with transmission loss,dispersion,cutoff wavelength and effective mode area comparable to single mode fiber?.?c?Propose a method to balance performance parameters such as additional loss of fiber and crosstalk between cores by flexible adjustment of the structural parameters of the fiber,in which way a high-quality 4-core imaging fiber has been successfully developed.?2?The design and preparation of three kinds of few-mode fibers are studied.?a?For the first time,a method of reducing the DMGD of a few-mode optical fiber by introducing a ring of hexagonal arranged air holes around the graded-index core is successfully proposed.And a four-mode optical fiber supporting four linear polarized modes with low DMGD,large effective mode area and low bending loss is successfully obtained.Specifically,The|DMGD|of the fiber is less than 35 ps/km over the whole C+L band,with the effective mode area of the LP₀₁ mode at the wavelength of 1550 nm being about 107?m² and the bending loss of the LP₀₂2 mode at the bending radius of 30 mm and at the wavelength of 1625 nm to be less than 0.1 dB/100 turns.Thus,the few-mode fiber can significantly reduce the complexity of MIMO-DSP and effectively improve the transmission distance of the MIMO system.?b?To meet the demand of short-range mode division multiplexing system,a method to increase the birefringence of optical fibers by adding a circular air hole in the elliptical ring core is proposed.A 10-mode and 14-mode weakly coupled few-mode optical fiber are successfully designed,which can relieve the receiver of additional MIMO-DSP technology,thus reducing the system complexity and cost.?c?To meet the demand of long range distributed Raman temperature sensors based on quasi-single-mode transmission,a 2-LP mode optical fiber with large mode area and low bending loss is designed and fabricated,which supports two transmission modes at both 1550 nm and 1310 nm,with the effective area of fundamental mode larger than 120 um² and bending loss less than 0.5 dB/100turns at the curvature radius of 30 mm.?3?Study a novel disordered optical fiber for spatial division multiplexing systems.The light-guide mechanism,classification,and main issues in design and preparation of disordered optical fiber are analyzed.The modeling,simulation method and crosstalk mechanism of disordered optical fiber are mainly studied.The influences of solving domain size,horizontal and vertical calculation steps on beam localization effect are analyzed.And a method to improve computational efficiency is proposed;Finally,the characteristics of two beams simultaneous transmission in a disordered fiber are studied,demonstrating the potential of disordered optical fibers in space-division multiplexing systems.