Abstract
We propose a theoretical mode division multiplexing (MDM) transmission model in a few mode fibers and numerically simulate the effects of mode coupling and modal dispersion on the transmitted signal. An adaptive signal processing with multiple-input multiple-output equalizers based on recursive least squares constant modulus algorithm (CMA) is proposed and demonstrated. The simulation results show that the mode signals are equalized sufficiently with a faster convergent speed than regular CMA. The equalization algorithm presented is more adaptive to complicated channels and applicable to the MDM system.
Highlights
With the explosive development of Internet and personal data services in the past decade, our demand for network bandwidth is rapidly growing
Mode coupling occurs along the fiber link randomly, so we have to model it in a discrete way
The transmission channel of an N-mode system can be described by a 2N × 2N matrix shown as Eq (5), a 2N × 2N multiple-input multiple-output (MIMO) digital signal processing (DSP)
Summary
With the explosive development of Internet and personal data services in the past decade, our demand for network bandwidth is rapidly growing. Mode division multiplexing (MDM) in the few mode fiber (FMF) is a practical way to improve the capacity and solve the bandwidth crisis. MDM systems based on FMFs have been theoretically studied, and some experiments have been demonstrated.[1,2] Mode coupling and differential mode delay are two major challenges to the practicability of this promising technology. Along a practical fiber link, the imperfect parameters always exist, including micro bending, fiber twisting, and fluctuant refractive index distribution. All these factors damage the orthogonality of spatial modes and lead to random mode coupling.
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