Study On The Vector-mode-division-multiplexing Technology For Short-reach Optical Interconnect

The developments of bandwidth-hungry services in data center or super-computing center are leading to data explosion,so the capability of short-reach optical interconnection systems should be urgently improved to meet the ever-growing demand for data traffic.To break through the capacity bottleneck,multi-dimensional multiplexing techniques of optical signal in the domain of time,frequency,polarization and phase have been studied and applied to commercial systems successfully.However,since the low cost and power consumption are the most important concern for the short reach optical interconnection systems,traditional wavelength division multiplexing,polarization multiplexing techniques and coherent detection technique cannot be used in data center or super-computing center.To relieve bandwidth requirements and satisfy ultra-high capacity,mode division multiplexing(MDM)technique has been proposed to deal with this challenge.Due to their orthogonality,different spatial modes at the same wavelength can be treated as parallel and independent channels to achieve large-capacity transmission systems only based on low-cost and low power consumption direct detection(DD)technologies.Thus,the MDM-DD-based scheme in short-reach optical interconnects shows its potential in terms of cost,complexity and power consumption.Vector mode(VM)is also introduced lately as a new orthogonal multiplexing technique due to its good performance.In this paper,we experimentally demonstrate the vector-mode-division-multiplexing(VMDM)system with direct-detection orthogonal-frequency-division-multiplexing(DD-OFDM)signal over free space optical(FSO)link and few-mode fiber(FMF)link.The main work accomplished includes the following: 1.We introduce the main characteristics of CVBs and the high-order Poincaré sphere model to investigate the state of polarization conversion of vector mode.2.We experimentally demonstrate a 120-Gbit/s mode-division-multiplexing(MDM)system based on two typical vector modes of TE01 and TM01 with direct detection orthogonal frequency division multiplexing(DD-OFDM)and 32-quadrature-amplitude-modulation(32QAM)signal.3.We experimentally demonstrate a vector-mode-division-multiplexing(VMDM)system based on optical frequency comb(OFC)over 80 cm free space optical(FSO)link.The 228 Gbit/s data transmission has been achieved by using two basic vector modes over 20 wavelengths with direct detection orthogonal frequency division multiplexing(DD-OFDM)signal.4.We introduce a high-efficient CVBs conversion scheme by using Q-plate(QP)and half-waveplate(HWP).This scheme provides a simple and flexible method to realize conversion of arbitrary vector mode.Then,we apply this vector mode conversion to demonstrate 95.16Gbit/s 4-CVB-based VMDM transmission system.5.We demonstrate the VMDM transmission over few-mode fiber(FMF)with the 1st order vector mode.We use a modal decomposition scheme to analyze the mode intercoupling and the variation of spatial and polarization distribution when the CVBs propagate in the few mode fiber.