MDM of Hybrid Modes in Multimode Fiber

This paper reports on MDM of a combination ofhelical-phased modes comprising ring modes and HG modes.44Gbps data transmission is achieved by a wavelength divisionmultiplexing (WDM) - MDM system of two center-launchedhelical-phased ring modes and two 3μm radially offset HG modeon wavelengths 1550.12nm and 1551.72nm for a 1500m-longmultimode fiber. The power coupling coefficients, degeneratemode group delays and bit error rates are analyzed for differentHG modes and radial offsets

Investigation of channel spacing for Hermite-Gaussian mode division multiplexing in multimode fiber

Mode division multiplexing (MDM) may be used to increase the capacity of multimode fiber interconnects for data centers.This paper demonstrates the importance of controlling the channel spacing of a MDM system capitalizing on Hermite-Gaussian (HG) modes in order to mitigate modal dispersion and minimize the average system bit-error rate.The effect of channel spacing of a 25-channel hybrid MDM-wavelength division multiplexing (WDM) system was examined through the x-index and y-index separations of Hermite polynomials of HG modes for different MMF lengths. Simulations prove that by controlling the index separations of the Hermite polynomials, acceptable BER was achieved for 25Gb/s data transmission for a distance of 800 meters for a 25-channel HG-based MDM-WDM system at a center wavelength of 1550.12nm.The optimal x-index and y-index Hermite polynomial separations for the HG modes are 2, 3 and 4

20 Gb/s mode-group-division multiplexing employing Hermite-Gaussian launches over worst-case multimode fiber links

For the first time, mode group division multiplexing is achieved in a multimode fiber link using a 2-D Hermite-Gaussian mode launch. 20 Gb/s error-free transmission is achieved over a 250 m worst-case OM1 multimode fiber link. © OSA 2014

Optical Fibers for Space-Division Multiplexed Transmission and Networking

Single-mode fiber transmission can no longer satisfy exponentially growing capacity demand. Space-division multiplexing (SDM) appears to be the only way able to dramatically improve the transmission capacity, for which, novel optical fiber is one of the key technologies. Such fibers must possess the following characteristics: 1) high mode density per cross-sectional area and 2) low crosstalk or low modal differential group delay (DMGD) to reduce complexity of digital signal processing. In this dissertation, we explore the design and characterization of three kinds of fibers for SDM: few-mode fiber (FMF), few-mode multi-core fiber (FM-MCF) and coupled multi-core fiber (CMCF) as well as their applications in transmission and networking. For the ultra-high density need of SDM, we have proposed the FMMCF. It combines advantages of both the FMF and MCF. The challenge is the inter-core crosstalk of the high-order modes. By applying a hole-assisted structure and careful fiber design, the LP11 crosstalk has been suppressed down to -40dB per km. This allows separate transmission on LP01 and LP11 modes without penalty. In fact, a robust SDM transmission up to 200Tb/s has been achieved using this fiber. To overcome distributed modal crosstalk in conjunction with DMGD, supermodes in CMCFs have been proposed. The properties of supermodes were investigated using the coupled-mode theory. The immediate benefits include high mode density and large effective area. In supermode structures, core-to-core coupling is exploited to reduce modal crosstalk or minimize DMGD. In addition, higher-order supermodes have been discovered in CMCFs with few-mode cores. We show that higher-order supermodes in different waveguide array configurations can be strongly affected by angle-dependent couplings, leading to different modal fields. Analytical solutions are provided for linear, rectangular and ring arrays. Higher-order modes have been observed for the first time using S2 imaging method. Finally, we introduce FMF to gigabit-capable passive optical networks (GPON). By replacing the conventional splitter with a photonic lantern, upstream combining loss can be eliminated. Low crosstalk has been achieved by a customized mode-selective photonic lantern carefully coupled to the FMF. We have demonstrated the first few-mode GPON system with error-free performance over 20-km 3-mode transmission using a commercial GPON system carrying live Ethernet traffic. We then scale the 3-mode GPON system to 5-mode, which resulted in a 4dB net gain in power budget in comparison with current commercial single-mode GPON systems