Research On Bidirectional Transmission And ROADM Technology In Optical Space Division Multiplexing System

With the rapid development of data services,the integration speed of IP networks is accelerating,so the expansion of the network is particularly important.Studies have shown that the capacity growth of wavelength division multiplexing?WDM?optical transmission has slowed significantly,and the system experiments are approaching the Shannon limit of nonlinear optical fiber transmission,which limits the development of all-optical communication.Therefore,the spatial mode dimension is introduced.Space-division multiplexing?SDM?technology based on spatial degrees of freedom is considered to be an important solution to further increase transmission capacity.Among them,the mode-division multiplexing?MDM?technology based on less-mode fiber is widely used.Because the modes in the fiber are orthogonal to each other,the MDM technology uses this orthogonality to load each mode as an independent channel,thereby effectively improving transmission capacity and spectral efficiency.At the same time,with the rapid growth of transmission capacity,it also brings pressure and power to the switching system.As the electronic switching technology reaches the bottleneck,people have introduced photonic technology,among which the reconfigurable optical add-drop multiplexing?ROADM?technology can Carrying out business dredging,routing and monitoring functions can significantly improve the transparency,throughput and survivability of the entire network and attract people's attention.Based on the research of optical switching technology,this thesis designs two structures as follows:One is a WDM-MDM bandwidth adjustable bidirectional transmission system.The six mode selective photonic lanterns are used as multiplexer?MUX?and demultiplexer?DEMUX?,LP₂₁mode and LP₀₁mode as the forward transmission channel,LP₀₂mode and LP₀₁mode as the reverse transmission channel.By controlling optical switches,two degenerate modes of LP₁₁are selected as optical forward and reverse transmission channels.It is realized that bidirectional bandwidth adjustable transmission of 12.5km.This structure bandwidth is adjusted by adjusting the number of transmission modes through the optical switching matrix.We also experimentally built the system structure and measured the transmission performance of the system on the C-band and L-band.The inter-mode intermodulation of the three modes was less than-24d B.Bit error rate and eye diagram performance,when the LP₀₁mode and LP_11amode receive power as low as-17d Bm and-16d Bm,the conclusion that the bit error rate of the two mode signals can reach 10^-3.The feasibility and reliability of the transmission system are verified,and it is suitable for low-cost and large-capacity communication scenarios.The other is a novel SDM-ROADM structure.The optical node is a simple two-layer architecture with all-optical multi-granularity switching,business grooming,channel add-drop,and online monitoring.We demonstrated multi-core fiber?MCF?and fiber-level switching,fiber-level granularity and wavelength-level granularity business dredging.By building an experimental system and measuring its transmission performance,the experimental results show that the average transmission loss of optical signals in this switching system-10.5d B,the average crosstalk is-40d B,and the average bit error rate?BER?is 10^-10,which proves that the structure has high feasibility and reliability.Finally,the optical signal transmission quality is monitored by the eye diagram test unit,and the obtained eye diagram can verify that the system has good communication quality.