Analysis And Design Of Few-Mode Fiber For Mode-Division Multiplexing Technology

Since the birth of fiber optic transmission network, the optical transmission network has got exciting development in the transmission rate, coverage and use. Nowadays, with big data, internet banking, cloud computing and other Internet technology advancing, the demand for transmission capacity is showing explosive growth. In order to meet customer’s demands and improve system capacity, the researchers made a series of breakthroughs in the use of single-mode fiber optical transmission systems. Multiplexing technologies have made great advances in the past decades in the time-, frequency-, amplitude-and phase-domain. It greatly enhanced the capacity of single-mode fiber transmission systems. But after the development in recent years, the capacity of single-mode fiber transmission system is more and more close to the theoretical limit of capacity. It can hardly keep pace with today’s increasingly rapid development of information technology. The technology of mode-division multiplexing based on few-mode fiber (FMF) is a new multiplexing and has attracted more and more attention in recent years. It is likely to be the key factor to solve such a problem of single-mode fiber transmission system faced.Firstly, we mainly studied the mode-division multiplexing transmission based on few-mode fiber in this paper, and calculated a lot about the modes in few-mode fiber. Then we got the eigenvalue equation of the modes. The orthogonality between modes has also been proved. After that, we got the two-dimensional optical field distribution of the 30 modes which is the relatively common in few-mode fiber by the electric field simulation method. All of those cases have laid a theoretical foundation for follow-up study.Then the transmission experiment platform was established by applying the fundamental principles of the mode-division multiplexing transmission which has been explained in chapter 3. The established experiment platform is the transmission system with the transmission distance of 10km. The performance of mode-division transmission system based on few-mode fiber has been fully studied. At the same time, the influence of the loss and the difference mode delay in few-mode fiber has been analysed.After that, few-mode single core fiber for mode-division multiplexing technology has been designed in this paper, which has low difference mode delay characters within O-band. The ideas of designing these fibers start with the refractive index profile of typical single-mode fiber. Then we got what we want by changing the refractive index distribution of the core and cladding, so does the radial length of the cores. Not only designed scheme were proposed in ideal condition, but also designed scheme in non-ideal conditions. The designed few-mode single fibers have three types. One support two modes, LP01 and LP11; The other two support six modes, LP01,LP02, LP11, LP12,LP21 and LP31.At last, the few-mode multi-core fiber for mode-division multiplexing technology was designed, which has low difference mode delay character within O-band. The refractive index distribution of the boundary between cores and cladding was always non-ideal, because several cores share common cladding. So, not only designed scheme were proposed in ideal condition, but also designed scheme in non-ideal conditions. The few-mode multi-core fiber supports 3×2 modes.