Multi-core fibers, few-mode fibers and their hybrid combination, few-mode-multi-core fibers are promising transmission media for future high-capacity, space-division multiplexed optical fiber transmission systems. In this paper, we report on our latest short and long-haul transmission demonstrations, including record breaking 10.66 Pb/s transmission in a 38-core, three-mode fiber as well as 172 Tb/s over more than 2000 km coupled-core three core fiber, using more than 75 nm bandwidth in C- and L-bands. We further discuss key transmission channel parameters, such as the impulse response time spread and mode-dependent loss and their consequences on the transmission performance.
Integrated space-division multiplexed (SDM) erbium-doped fiber amplifiers (EDFAs) are not only inevitable for SDM systems, but can be an alternative solution to nowadays EDFA array for parallel amplification. SDM EDFAs are expected to provide substantial complexity and cost savings through spatial-integration compared to duplicating single-mode fiber amplifiers. High output power and low noise figure can be achieved by cladding-pumped SDM EDFAs. In this paper, different cladding pumping solutions, cladding-pumped single-mode and multimode multi-core EDFAs will be discussed.
The capacity of optical transmission systems has increased dramatically since their first deployments in the mid
1970s . However, studies show that the theoretical capacity limit of single-mode fiber is about to be reached, and
space-division multiplexing has been proposed to overcome this limit. With the high levels of integration needed
for economic deployment, space-division multiplexing may exhibit large crosstalk between the supported fiber
modes. We propose to use coherent multiple-input multiple-output (MIMO) digital signal processing (DSP), a
technique widely used in wireless communication, to compensate crosstalk present in spatial multiplexing over
fibers. According to MIMO theory, crosstalk in multi-mode transmission systems can be completely reversed
if the crosstalk is described by a unitary transformation. For optical fibers this is fulfilled if all available fiber
modes can be selectively excited and if all the modes are coherently detected at the end of the fiber, provided
that mode-dependent loss is negligible. We successfully applied the technique to demonstrate the transmission
of six independent mode-multiplexed 20-Gbaud QPSK signals over a single, optically amplified span of 137-km few-mode fiber (FMF). Further, in a multi-span experiment, we reach 1200 km by transmitting over a
3-core coupled-core fiber (CCF). Details for both experiments will be presented, including the description of the
supported polarization- and spatial modes of the fiber, the mode multiplexers used to launch and detect the
modes, and the MIMO DSP algorithm used to recover the channels.
We review physical layer challenges associated with the emerging class of optically-routed networks. We discuss the influence of reconfigurable optical add-drop multiplexers (ROADMs), advanced modulation formats, and electronic signal processing techniques at transmitters and receivers to increase optical transparency in optically-routed networks.
We show that mode-locking based on the formation of a fundamental soliton can be accomplished with a nonlinear twin-core fiber added to a homogeneously broadened gain medium within a laser cavity. The transient state towards equilibrium in such a device is characterized by an increase in the spectrum width of the pulse until a steady-state value is reached which is exceeding the gain bandwidth. At steady-state, the linear coupling properties of the twin-core fiber is continuously allowing for the radiated power from the perturbed soliton to exit the laser cavity. The corresponding energy gain per round trip eventually becomes a small perturbation to the soliton which recovers its shape and phase profile within each round trip.
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