Qi Mo

Demonstration of Bidirectional PON Based on Mode Division Multiplexing

Recently, mode division multiplexing (MDM) has been introduced into optical transmission systems and networks for capacity enhancement. In this letter, we propose a bidirectional passive optical network (PON) architecture based on MDM. The bidirectional optical distribution network (ODN) of the MDM-PON consists of few-mode fiber, passive mode multiplexer/demultiplexer and few-mode circulators (FMCs), all of which are characterized by low modal-crosstalk. Signals in different modes are able to be transmitted and received independently for both downstream and upstream transmission. We experimentally demonstrate the bidirectional MDM-PON transmission over 10-km 2-mode optical fiber. 10-Gb/s on-off-keying (OOK) signals can be independently transmitted and directly detected without coherent receiver and multi-input-multiple-output (MIMO) processing. Moreover, nonlinear transmission impairments are experimentally investigated.

Cascaded Mode-Division-Multiplexing and Time-Division-Multiplexing Passive Optical Network Based on Low Mode-Crosstalk FMF and Mode MUX/DEMUX

We propose cascaded mode-division-multiplexing and time-division-multiplexing passive optical network (MDM-TDM-PON) based on low mode-crosstalk few-mode fiber (FMF) and all-fiber mode multiplexer/demultiplexer (MUX/DEMUX), in which optical network units communicate with the optical line terminal utilizing different time slots and specific optical linearly polarized spatial modes. An MDM optical distribution network (ODN) is cascaded with multiple conventional TDM ODNs to effectively extend a larger scale of current commercial PON systems based on TDM. The upgrade from TDM-PON to the cascaded MDM-TDM-PON is simple and cost-effective. No multiple-input-multiple-output (MIMO) digital signal processing is required to eliminate the mode crosstalk. The all-fiber mode MUX/DEMUXs are composed of mode selective couplers, which simultaneously multiplex or demultiplex multiple modes. We experimentally demonstrate MDM-PON transmission over 10 and 55 km two-mode FMFs and cascaded MDM-TDM-PON transmission over a 10-km two-mode FMF and a 10-km standard single-mode fiber with 10-Gb/s optical on-off keying (OOK) signal and direct detection.

Demonstration of all-optical MDM/WDM switching for short-reach networks

Mode division multiplexing (MDM) has been widely investigated in optical transmission systems and networks to improve network capacity. However, the MDM receiver is always expensive and complex because coherent detection and multiplex-input-and-multiplex-output (MIMO) digital signal processing (DSP) are required to demultiplex each spatial mode. In this paper, we investigate the application of MDM in short-reach scenarios such as datacenter networking. Two-dimensional MDM and wavelength division multiplexing node structure based on low modal-crosstalk few-mode fiber (FMF) and components is proposed, in which signal in each mode or wavelength can be independently switched. We experimentally demonstrate independent adding, dropping and switching functionalities with two linearly polarized modes and four wavelength channels over a total 11.8-km 2-mode low modal-crosstalk FMFs. The structure is simple without coherent detection or MIMO DSP. Only slight penalties of receiver sensitivity are observed for all switching operations. The influence of modal-crosstalk accumulation for cascaded switching nodes is also investigated.

Experimental Demonstration of Mode-Division-Multiplexing and Time-Division-Multiplexing Passive Optical Network

We propose and experimentally demonstrate for the first time mode-division-multiplexing and time-division-multiplexing passive optical network (MDM-TDM-PON). Both upstream and downstream transmissions with two individual linearly polarized (LP) spatial modes are investigated.

Experimental demonstration of ROADM functionalities for hybrid MDM-WDM optical networks

We propose a ROADM structure based on low-modal-crosstalk FMF and mode MUX/DEMUX, in which both mode and wavelength can be added/dropped independently without MIMO DSP. We experimentally demonstrate its feasibility over 11.8-km 2-mode FMF.

Experimental demonstration of 3-mode MDM-PON transmission over 7.4-km low-mode-crosstalk FMF

We demonstrate 3-mode mode-division-multiplexing passive optical network (MDM-PON) based on low-mode-crosstalk few-mode fiber and all-fiber mode multiplexer/demultiplexer. Error-free performance is achieved for 7.4-km low-mode-crosstalk three-individual-spatial-mode transmission with 10-Gb/s optical on-off keying signal and direct detection.

Experimental demonstration of bidirectional MDM-WDM-TDM-PON over low modal-crosstalk FMF

We propose a bidirectional MDM-WDM-TDM-PON architecture, in which mode is induced as independent multiplexing granularity and smooth evolution from conventional WDM-TDM-PON is achieved. Bidirectional transmission over 10-km 2-mode FMF and 10-km SSMF is experimental demonstrated.

Wavelength-interleaved MDM-WDM transmission over weakly-coupled FMF

Recently mode-division-multiplexing (MDM) has been widely investigated to enhance fiber optics capacity, in which modes or mode groups in few-mode fiber (FMF) or multi-mode fiber (MMF) are exploited as different spatial channels for data transmission. For short-reach applications, significantly reducing inter-spatial-channel crosstalk to avoid coherent detection and multiple-input-multiple-output (MIMO) equalization is preferred. Currently most studies focus on the design of weakly-coupled FMFs and mode (de)multiplexers. Alternatively, in this work, a wavelength-interleaved (WI) scheme is proposed to mitigate inter-spatial-channel crosstalk by optimizing the design of direct detection (DD) MDM and wavelength-division-multiplexing (WDM) system. In weakly-coupled MDM systems, crosstalk mainly comes from the adjacent spatial channels, and the signal-to-crosstalk beat interference (SCBI) constitutes main crosstalk impairment after square-law detection. The WI scheme interleaves the WDM grids in adjacent spatial channels by half WDM channel spacing and uses an electrical low-pass filtering (ELPF) to remove out-of-band SCBI. The effectiveness of SCBI suppression is theoretically analyzed. The feasibility of WI scheme is experimentally verified by 3-mode 3-wavelength MDM-WDM transmission over 500-m OM3 MMF. Enabled by WI scheme, record 120-km 10G-per-channel MDM-WDM transmission over 2-mode FMF without MIMO equalization is successfully demonstrated. The WI scheme is promising to enhance the performance of short reach or even metro MDM optics.

Experimental Demonstration of Time- and Mode-Division Multiplexed Passive Optical Network

We propose time- and mode-division multiplexed passive optical network (TMDM-PON), in which ONUs operate with both different time slots and switched modes. We experimentally demonstrate 10 km 2-mode TMDM-PON transmission without multi-input-multi-output (MIMO) processing.