Impact of mode coupling on the mode-dependent loss tolerance in few-mode fiber transmission

Abstract

Spatial-division multiplexing in the form of few-mode fibers has captured the attention of researchers since it is an attractive approach to significantly increase the channel capacity. However, the optical components employed in such systems introduce mode-dependent loss or gain (MDL) due to manufacturing imperfections, leading to significant system impairments. In this work the impact of MDL from optical amplifiers in few-mode fibers with either weak or strong mode coupling is analyzed for a 3x136-Gbit/s DP-QPSK mode-division multiplexed transmission system. It is shown that strong mode coupling reduces the impact of MDL in a similar manner as that polarization-dependent loss is reduced in single mode fibers by polarization-mode dispersion.

Reach Improvement of Mode Division Multiplexed Systems Using Fiber Splices

“…2. The transmitter is composed by 3 single mode transmitters (SMTX) generating 3 signals at the same wavelength carrying 136 Gbit/s each, from which 24 % are forward error correction and 10 % are training symbols, using coherently detected polarization multiplexed quadrature-phase-shift-keying (CP-QPSK) modulation modeled as in [9]. The 3 data signals are launched into the FMF using a mode multiplexer (MMUX).…”

“…A 6 × 6 MIMO DSP is used, since FMFs with 3 LP modes (each with 2 polarizations) are considered. The DSP used is the 6 × 6 data-based equalizer presented in [9], considering 1001 taps, allowing mitigation of the transmission effects contained within a time interval of 15 ns. The performance was measured considering: the required OSNR (rONSR) for a 10 -2 bit-error-ratio on the worst mode, and the available OSNR (aOSNR) on the worst mode (determined by the launch power, the SMEDFAs NF, the fiber losses, the MMUX/MDMUX losses, and the splice MDL).…”

Capacity Enhancement of Few-Mode Fiber Transmission Systems Impaired by Mode-Dependent Loss

“…To mitigate the MDL effect, different optical and digital signal processing (DSP) solutions were proposed [11,12]. The availability of information about the FMF channel at the transmitter known as channel state information (CSI) is an important factor that governs the capacity of FMF systems impaired by MDL.…”

“…However, with the availability of CSI at the transmitter, capacity can be improved by allocating optimal powers to spatial modes [12]. Additionally, strong mode coupling was reported to reduce the accumulated MDL and hence results in a better system capacity [11]. Moreover, modal coupling can be intentionally added at local points thanks to mode scramblers [13].…”

Mode-dependent loss measurement of a two-mode fiber using a conventional OTDR

“…When mode-division multiplexed (MDM) transmission is used, there is a potential to increase the per-core transmission capacity. The mode-dependent loss (MDL) of optical components, including two-mode fiber (TMF), degrades transmission characteristics such as transmission distance and capacity [4,5]. The MDL compensation technique is investigated to mitigate the MDL [6].…”