Orbital Angular Momentum Multiplexing for High-capacity Intra-data Center Communication Links
Author: Mai Banawan
Publisher:
Published: 2023
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOKIn recent years, traffic volume inside data centers has increased significantly. As a result, we need scalable and efficient solutions appropriate for a data center infrastructure. Mode division multiplexing (MDM) is an excellent candidate to increase the capacity of such optical links. In this thesis, we examine ring-core fibers (RCFs) that support the propagation of orbital angular momentum (OAM) modes for multiplexing. We show the advantages of using OAM modes compared to other mode multiplexing solutions. In our first contribution, we introduced a numerical model to find coupling coefficients between OAM modes due to elliptical deformation in the fiber. Our model predicts experimental observations which cannot be seen with the classical perturbation models. We used the model to compare the performance of various fiber designs. In the second contribution, we fabricated a fiber design found to have low coupling using our numerical model. We characterized the mode-dependent loss (MDL) of the fiber experimentally. We minimize fiber destruction during MDL characterization with four fixed fiber lengths, probing each mode in a round-robin fashion. We used a re-programmable receiver to validate the purity of the modal excitation. We maximized launched mode purity and coupling by optimizing the free-space beam width and diameter using the perfect vortex excitation technique. We discuss several challenges we confronted, and demonstrate the advantages of our MDL technique over other techniques. Our fiber loss is acceptable for intra-data center links. In our third contribution, we examined data transmission performance in our fiber. We compared reception performance without multiple-input multiple-output (MIMO) processing (neither optical nor electronic) and reception with 2×2 MIMO. The two reception schemes overcome the complexity of 4×4 MIMO and the impracticality of optical MIMO. We discuss the hardware required at the demultiplexer to achieve the 2×2 MIMO. We demonstrate eight data channel transmissions over 600 m and 1.3 km of RCF across the C-band. In the last contribution, We examined the transmission of OAM modes and wavelength-division multiplexing (WDM) channels to increase the optical link capacity in data centers. We successfully transmitted data on twelve OAM modes and three wavelengths simultaneously in the fiber. We examined the performance when sweeping three WDM channels across the extended C-band, achieving the highest recorded net bit rate for OAM transmission, 65.5 Tb/s.
