Kyung Jun Park

Mode division multiplexed optical transmission enabled by all–fiber mode multiplexer

Mode division multiplexed optical transmission enabled by all-fiber mode multiplexer is investigated. The proposed all-fiber mode multiplexer is composed of consecutive mode selective couplers. It multiplexes or demultiplexes LP01, LP11, LP21, and LP02 modes simultaneously. We demonstrate successful transmission of three spatial modes with 120 Gb/s PDM-QPSK signals over 15 km of four mode fiber by using 6x6 MIMO digital signal processing.

Ultrafast Pulsed All-Fiber Laser Based on Tapered Fiber Enclosed by Few-Layer WS 2 Nanosheets

We demonstrate all-fiber mode-locked laser based on a tapered optical fiber saturable absorber (SA) enclosed in tungsten disulfide (WS2) nanosheets. Tapered fibers were fabricated using the standard flame brushing method to an interaction length of 3 mm with waist diameters of 10 and 15 μm. WS2 nanosheets were prepared via a liquid phase exfoliation method to form a uniform dispersion. Subsequently, the WS2 nanosheets were optically deposited along the interaction length of the tapered fibers by evanescent field interactions. We built a ring laser including the fabricated mode-lockers. The SA with a 10-μm taper diameter delivers the pulses with a pulse duration of 369 fs and 3-dB spectral bandwidth of 7.5 nm; on the other hand, the output pulses using the mode-locker with 15-μm waist diameter were found to have 563-fs pulse duration and 5.2 nm of 3-dB bandwidth. It is shown that the smaller waist diameter of tapered fiber causes wider spectral bandwidth of the ultrafast pulses and narrower 3-dB bandwidth.

Broadband mode division multiplexer using all-fiber mode selective couplers.

We report an all-fiber mode division multiplexer formed with cascaded mode selective couplers with significantly broadened bandwidth potentially spanning S, C and L band. This was achieved by matching the effective refractive indices over a wide wavelength range for the few mode fiber and the single mode fiber used in the coupler. The multiplexer provides high coupling efficiency (>55% for the worst case) for the 4 spatial modes over the entire wavelength range of 1515-1590 nm. The all-fiber construction provides mechanical stability. Experimental results for the coupling efficiency and the mode extinction ratio for each spatial mode are presented along with the far field radiation patterns.

Mode- and wavelength-division multiplexed transmission using all-fiber mode multiplexer based on mode selective couplers.

We propose all-fiber mode multiplexer composed of two consecutive LP₁₁ mode selective couplers that allows for the multiplexing of LP₀₁ mode and two-fold degenerate LP₁₁ modes. We demonstrate WDM transmission of 32 wavelength channels with 100 GHz spacing, each carrying 3 modes of 120 Gb/s polarization division multiplexed quadrature phase shifted keying (PDM-QPSK) signal, over 560 km of few-mode fiber (FMF). Long distance transmission is achieved by 6×6 multiple-input multiple-output digital signal processing and modal differential group delay compensated link of FMF. The all-fiber mode multiplexer has considerable potential to be used in mode- and wavelength-division multiplexed transmission.

All-Fiber Mode Division Multiplexer optimized for C-band

We demonstrate the excitation of all of the higher-order modes in a few-mode fiber using mode-selective couplers made by taper-polish method. Each mode selective coupler provides exclusive mode coupling between the LP01 mode of a single-mode fiber and each of the LP11, the LP21, and the LP02 modes of a few-mode fiber, respectively. We also demonstrate the C-band optimized mode division multiplexer using cascaded mode selective couplers.

Passive Q-Switching of an All-Fiber Laser Using WS 2 -Deposited Optical Fiber Taper

We demonstrate the passive Q-switching operation of an erbium-doped fiber laser using a few-layer WS2-based saturable absorber with evanescent field interaction. WS2 flakes have been synthesized via a liquid-phase exfoliation method, and an optical fiber taper was selected as a light-material template that causes to achieve a long interaction length of the evanescent wave. Subsequently, the prepared solution was optically deposited around the 3-mm interaction length of the fabricated optical fiber taper with a 5-μm waist diameter. The proposed Q-switched fiber laser based on the WS2-deposited fiber taper saturable absorber could generate stable output pulses at 1565 nm, with a pulsewidth ranging from 1.3 to 3 μs and a repetition rate of 33-108 kHz.

All-fiber 6-mode multiplexers based on fiber mode selective couplers

All-fiber 6-mode multiplexer composed of two consecutive LP11-mode selective couplers (MSC), two LP21-MSCs and an LP02-MSC is fully characterized by wavelength-swept interferometer technique. The MSCs are fabricated by polished-type fiber couplers coupling LP01 mode of a single mode fiber into a higher-order mode of a few mode fiber. A pair of the mode multiplexers has minimum mode dependent loss of 4 dB and high mode group selectivity of over 15 dB. Mode division multiplexed transmission enabled by the all-fiber mode multiplexers is demonstrated over fiber spans of 117 km employing an in-line multi-mode optical amplifier. 6 modes of 120 Gb/s dual polarization quadrature phase shift keying signals combined with 30 wavelength channels are successfully transmitted.

All-fiber-based selective mode multiplexer and demultiplexer for six-mode multiplexed signals

We experimentally evaluate performance of selective six-mode multiplexer based on mode selective couplers. The mode-group coupling is suppressed by -20dB, maintaining OSNR penalty of 3dB due to mode multiplexing even with use of 6×6 MIMO.