- [Show abstract] [Hide abstract] ABSTRACT: We propose and demonstrate a novel mode analysis method that can provide a full set of amplitudes, phases, and polarization states of guided modes including degenerate modes in few-mode fibers. The method is based on the calculation of amplitude components and phase differences from the intensity profiles that passed through a polarizer with angles of 0, 45, and 90°. The accuracies of calculation formulas are shown by simulation to be less than 10−10 for amplitudes and 10−3 rad for phase differences. The method was applied to a graded-index three-mode fiber, and the off-axis mode excitation ratio characteristics were compared with theoretical ones.
- [Show abstract] [Hide abstract] ABSTRACT: A new design method for a high-order series-coupled microring filter using Chebyshev filter condition was proposed and its application to the design of a wavelength-selective switch (WSS) was discussed. In the proposed method, the propagation loss in a microring resonator, coupling loss at a coupler, and a free spectral ranges (FSR) in a microring resonator are considered for the first time. It was found that for high-order series coupled microring resonators, the WSS designed using Chebyshev condition has more boxlike filter responses and high extinction ratio, compared with that designed using Butterworth condition, in the case where the round-trip loss in a microring is relatively large. In addition, the fourth-order series-coupled microring WSS with boxlike responses was successfully designed, considering Vernier effect for a larger FSR and shift in resonant wavelength.
- [Show abstract] [Hide abstract] ABSTRACT: The evolution of electromagnetic field profile of LP modes along with the propagation owing to the difference of propagation constants between constituent true eigenmodes is accurately analyzed. It is shown that the mode demultiplexer can't accurately discriminate the LP mode at the output end and so the MIMO-DSP is inevitable for the mode division multiplexed transmission using LP modes. From the accurate analysis, a transform matrix between LP modes and constituent true eigenmodes is derived and a novel method to configure true eigenmode multi/demultiplexer is proposed to realize MIMO-free transmission.
- [Show abstract] [Hide abstract] ABSTRACT: We describe the design and characterization of a heterogeneous 36-core, three-mode fiber with three core types. Intercore crosstalk for LP11 modes is estimated to be below -31 dB for 5.5 km propagation at a core pitch of 34 μm. Feasibility of 108 space/mode division multiplexed transmission is investigated using free-space multiplexing/demultiplexing technologies, 40-wavelength division multiplexed, 25 GBd, 93.4-Gb/s dual-polarization QPSK signals, and coherent detection with a sparse 6 × 6 MIMO equalizer. The total transmission capacity amount to 403.7 Tb/s.
- [Show abstract] [Hide abstract] ABSTRACT: Mode-evolutional serial branching mode multi/demultiplexer (SBMM) for homogeneous coupled multi-core fiber was demonstrated. This multi/multiplexer has some advantages such as the high fabrication tolerance and small wavelength and polarization dependences owing to the principle of adiabatic mode-evolutional phenomenon. The SBMM was fabricated using polymer materials. The selective four mode excitation with the low crosstalk of less than -10dB and small wavelength dependence were realized within the CL-band.
- [Show abstract] [Hide abstract] ABSTRACT: Mode-evolutional multi/demultiplexer for few-mode fibers was demonstrated using stacked polymer waveguides. Owing to the stacked structure, TE00, TE10, and TE01 modes, which correspond to LP01, LPeven11 , and LPodd 11 modes, respectively, were selectively excited by the fabricated multiplexer. The mode excitation ratio was evaluated from the near-field patterns of excited modes using a mode analysis method called the averaged interference component method that we have developed. The evaluated mode excitation ratio was ranging from 6.4 to 9.7 dB for both transverse electric (TE) and transverse magnetic (TM) polarizations of first-order TE modes within the center and long wavelength (CL)-band.
- [Show abstract] [Hide abstract] ABSTRACT: A compact fan-in/fan-out waveguide device for 19-core uncoupled multi-core fibre (MCF) was demonstrated using laminated polymer waveguide. The core was made of poly-methyl-methacrylate and the cladding was made of ultra-violet (UV) cured epoxy resin which is solvent-free oligomer. Since the oligomer does not shrink after UV-curing, the surface of the cladding over the core ridge was flattened and the multiple layers can be laminated. The accurate core alignment in the vertical direction was realised by controlling the spin-coat condition of cladding material precisely. The insertion loss from a 19-core fibre to 19 single-core fibres was measured to be <20 dB and the sum of the cross-talk from all neighbouring cores was lower than -40 dB. The coupling loss which is caused by the offset of the core position and the spot size mismatch at the facet between the MCF core and the waveguide was <1.8 dB. It was shown that the coupling loss and the insertion loss can be improved by adopting a properly selected pair of polymer materials with appropriate value of index contrast and low absorption loss.
Conference Paper: Realizing a 36-core, 3-mode Fiber with 108 Spatial Channels[Show abstract] [Hide abstract] ABSTRACT: We describe the design and characterization of a 3-type heterogeneous 36-core, 3-mode fiber with record spatial channel count and density and perform transmission measurements in all 108 spatial channels using 40x100GHz spaced 25GBaud DP-QPSK signals.
- [Show abstract] [Hide abstract] ABSTRACT: The ultra large number of transmission channels, e.g. 389 channels in a fiber for space division multiplexing (SDM), is designed using an air-hole assisted double cladding few-mode multi-core fiber.
- [Show abstract] [Hide abstract] ABSTRACT: The ultimate number of transmission channels in a fiber for the space division multiplexing (SDM) is shown by designing an air-hole-assisted double-cladding few-mode multi-core fiber. The propagation characteristics such as the dispersion and the mode field diameter are almost equalized for all cores owing to the double cladding structure, and the crosstalk between adjacent cores is extremely suppressed by the heterogeneous arrangement of cores and the air holes surrounding the cores. Optimizing the structure of the air-hole-assisted double-cladding, ultra dense core arrangements, e.g. 129 cores in a core accommodated area with 200 μm diameter, can be realized with low crosstalk of less than -34.3 dB at 100km transmission. In this design, each core supports 3 modes i.e. LP<sub>01</sub>, LP<sub>11a</sub>, and LP<sub>11b</sub> as the transmission channels, so that the number of transmission channels can be 3-hold greater than the number of cores. Therefore, 387 transmission channels can be realized.
- [Show abstract] [Hide abstract] ABSTRACT: Low-power-consumption thermo-optically controlled silicon-microring-resonator loaded Mach-Zehnder modulators (MRR-loaded MZMs) are demonstrated. We experimentally characterized a single microring and cascaded-multiple-microring resonators coupled to one arm of a Mach-Zehnder interferometer (MZI). The driving power consumption of the proposed MZM is significantly reduced owing to the enhanced phase shift in the MRR. The device was fabricated on a silicon-on-insulator (SOI) waveguide structure, and each microring is equipped with TiN microheater for thermo-optic tuning. The coupling efficiency between the microring and a busline waveguide was regulated by varying the gap between two waveguides at a directional coupler. The power consumption of single microring and cascaded MRR-loaded MZMs was approximately 0.4 and 1 mW, respectively. The phase-shift enhancement factor of up to 19 with a maximum extinction ratio of 18 dB was obtained experimentally. Multiple-wavelength operation was also demonstrated in the cascaded MRR-loaded MZM. (C) 2014 The Japan Society of Applied Physics
- [Show abstract] [Hide abstract] ABSTRACT: Ultra-large number of transmission channels FM-MCF for SDM was designed by optimizing the air hole assisted double cladding structure. 387 (129cores×3modes) channels can be theoretically accommodated in 200um diameter area of a fiber.
- [Show abstract] [Hide abstract] ABSTRACT: We demonstrate a hitless wavelength-selective switch (WSS) based on InGaAs/InAlAs five-layer asymmetric coupled quantum well (FACQW) quadruple series-coupled microring resonators. The WSS is driven by the electric-field-induced change in refractive index in the FACQW core layer caused by the quantum-confined Stark effect (QCSE) for high-speed operation. The WSS with high-mesa waveguides is fabricated on a molecular beam epitaxy-grown wafer by dry etching. The fabricated WSS consists of four microrings, each with a round-trip length of 350 μm and five directional couplers with shallow grooves. A boxlike spectral response and hitless switching with higher extinction ratios than a double series-coupled microring resonator are successfully demonstrated. In addition, we propose the improvement of switching characteristics by controlling the coupling efficiencies at the directional couplers.
- [Show abstract] [Hide abstract] ABSTRACT: A compact 19-core fan-in/fan-out waveguide device for uncoupled multi-core fibers was demonstrated using laminated polymer waveguide. The coupling losses from a 19-core fiber to nineteen single-core fibers were less than 2.0 dB and the sum of crosstalk from all neighboring cores were lower than -40 dB.
- [Show abstract] [Hide abstract] ABSTRACT: Modulation characteristics of a novel InGaAs/InAlAs multiple quantum well (MQW) microring-enhanced Mach-Zehnder modulator (MRE-MZM) is investigated in detail and its low-voltage operation with high extinction ratio is demonstrated. The MZM has a single microring resonator in one arm and is driven by the change in electrorefractive index induced by the quantum-confined Stark effect in the MQW core layer. As the MQW, a multiple five-layer asymmetric coupled quantum well (FACQW) is used to obtain a large electrorefractive index change. The driving voltage of the proposed MZM is significantly reduced owing to the enhanced phase shift in the microring resonator. High-mesa waveguide structures are grown by solid-source molecular beam epitaxy and fabricated by inductively coupled plasma etching. A directional coupler with an asymmetric branching ratio is used as an input coupler to prevent the degradation of the extinction ratio of the MZM. The extinction ratio of the fabricated MRE-MZM is approximately 27 dB. The product of the half-wave voltage and phase shifter length, V<sub>π</sub>·L, is 1.7 Vmm in static modulation. This value is one-quarter that of a conventional MZM with the same waveguide structure.
- [Show abstract] [Hide abstract] ABSTRACT: We demonstrate a high-extinction-ratio hitless wavelength-selective switch with InGaAs/InAlAs multiple quantum well double-series-coupled microring resonators. It is also found that the change in coupling efficiency at couplers has a great effect on the switching characteristics.
- [Show abstract] [Hide abstract] ABSTRACT: A hitless wavelength-selective switch (WSS) based on InGaAs/InAlAs multiple quantum well (MQW) second-order series-coupled microring resonators is proposed and fabricated. In the core layer, a five-layer asymmetric coupled quantum well (FACQW) structure is employed. The WSS is driven by the electrorefractive index change in the FACQW core layer caused by the quantum-confined Stark effect (QCSE). The wafer for the WSS is grown by molecular beam epitaxy and waveguide structures are formed by dry etching. Boxlike spectrum responses and hitless switching characteristics of the WSS are successfully demonstrated for the first time. The change in coupling efficiency at a coupler between a ring and a busline and between rings and its effect on the switching characteristics are also discussed.
Yokohama National University
Yokohama, Kanagawa, Japan
- • Graduate School of Engineering
- • Department of Physics, Electrical and Computer Engineering
Kanagawa Academy of Science and TechnologyKawasaki Si, Kanagawa, Japan
Massachusetts Institute of Technology
Cambridge, Massachusetts, United States
- Research Laboratory of Electronics
Tokyo Institute of Technology
Edo, Tokyo, Japan
- Precision and Intelligence Laboratory