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Broadband Mode Multiplexer Formed with Non-planar Tapered Directional Couplers
摘要： We propose a broadband mode multiplexer based on the structure of cascaded planar and non-planar tapered directional couplers (DCs), which are designed for processing vertically symmetric and anti-symmetric modes. The DCs are tapered to widen the operating bandwidth, reduce the polarization dependence, and improve the fabrication tolerance. As an example, we design and fabricate a five-mode (de)multiplexer with polymer material to combine or separate the E11, E12, E21, E31, and E22 modes. Our typical fabricated device has a length of 2.1 cm and shows the mode coupling efficiency of almost larger than 94.5% for each DC over the C + L band with weak polarization dependence. The proposed structure is scalable and can be implemented with different material platforms.
关键词： mode multiplexer,Mode-division multiplexing,tapered waveguide,directional coupler,polymer waveguide
更新于2025-09-23 15:22:29
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Variable-Ratio Mode-Insensitive 1 × 2 Power Splitter Based on MMI Couplers and Phase Shifters
摘要： Mode-division multiplexing (MDM) has been considered as a low-cost and high-density means for high-bandwidth on-chip optical communications in a high-performance computer and a data center. However, simultaneously controlling the power of multiple modes in the MDM systems is dif?cult due to the complex mode coupling for high-order modes (HOMs). Here we propose a novel schematic structure of variable-ratio mode-insensitive 1 × 2 power splitter, which is based on multimode interference (MMI) couplers cascaded with phase shifters. We theoretically reveal the phase shifting relations between the fundamental mode and the HOMs for the phase shifter formed by two unequal-width waveguides. Then, the operating principles for the proposed structure are presented. Numerical simulations are carried out and it is found that the structure has the ability to realize variable-ratio dual-mode mode-insensitive 1 × 2 power splitter by designing the number and lengths of the phase shifters, which shows a good agreement with our theoretical analysis. The structural parameters of the MMI couplers and the phase shifters are optimized to minimize the transmittance losses and the differences of mode power splitting ratio. The simulation results also show that the optimized power splitters have the advantages of high tolerance to fabrication errors and wide operating bandwidths, which indicates that the proposed structure can operate on multiple modes and would be suited to potential applications in on-chip optical communications.
关键词： mode-insensitive power splitter.,mode-division multiplexing,Optical waveguide devices
更新于2025-09-23 15:21:01
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Polymer-Silica Hybrid On-Chip Amplifier with Vertical Pumping Method
摘要： This article demonstrates a multilayer polymer-silica hybrid on-chip amplifier combining mode division multiplexing method. The multilayer amplifier consists of a pumping silica waveguide and an amplifying polymer waveguide. The pumping waveguide possesses the stability and the high damage threshold. The amplifying waveguide takes the advantages of the high compatibility and the high doping rate. The vertical pump of mode division multiplexing method can introduce the pumping light into the amplifying waveguide at any desired position of the chip. By the isolation method between signal and pumping light, the pumping light can be coupled into the amplifying waveguide, while the signal light cannot be coupled into the pumping waveguide. The parameters of doping rates, waveguide lengths, overlap factors, coupling parameters are calculated to optimize the gain characteristics of the amplifier. The amplifier with three position-optimized pumping light was designed achieving a maximum gain of 33.89 dB/cm with a waveguide length of 6 cm, a signal power of 0.1 mW and a pumping power of 300 mW. This polymer-silica hybrid amplifier is promising for the on-chip loss compensation of the 3D photonic integrated circuits and all optical transistors.
关键词： vertical pumping method,on-chip amplifier,polymer-silica hybrid,mode division multiplexing,3D photonic integrated circuits
更新于2025-09-23 15:21:01
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Nonlinear Performance of Few-Mode Fiber Links with Intermediate Coupling
摘要： This paper reviews and extends the study of nonlinear performance of few-mode fiber links operating in all different linear coupling regimes for different mode delay maps. Nonlinear performance was estimated using the four-wave-mixing theory and the split-step Fourier method including semi-analytical solutions for linear mode coupling of arbitrary strength. The optimum link configurations minimizing the nonlinear penalty at practical levels of training sequence length are presented, including: the required coupling strength to give nonlinear distortion below that of the single-mode propagation without mode coupling, and the impact of mode delay maps. Finally, different approximate solution methods of the multimode nonlinear Schr?dinger equation are compared, highlighting the accuracy of a stochastic solution method including distributed linear mode coupling.
关键词： Mode-division multiplexing,few-mode fiber,linear mode coupling,fiber nonlinearity
更新于2025-09-19 17:15:36
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Mode Conversion Based on Lateral Misalignment between Two Multi-Ring Core Fibers for MDM System
摘要： In this report, mode conversion based on the lateral misalignment between two similar multi-ring core fibers (M-RCFs) is proposed. The conversion was achieved by varying the lateral height (y) and the distance (x) that separates the two M-RCFs. Based on the achieved coupled power of 94%, this technique may find application as a conversion device during multiplexing in mode-division multiplexed systems (MDM).
关键词： coupled power,multi-ring core,mode conversion,mode division multiplexing
更新于2025-09-19 17:15:36
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Numerical Investigation of the Equalization Enhanced Phase Noise Penalty for M-Quadrature Amplitude Modulation Formats in Short-Haul Few-Mode Fiber Transmission Systems with Time-Domain Equalization
摘要： The equalization enhanced phase noise (EEPN), caused by the interaction of the chromatic dispersion (CD) with the phase noise of the local oscillator (LO), has been extensively studied for single-mode optical communication systems. Few-mode fiber (FMF) transmission systems introduce a new channel impairment, the differential mode delay (DMD), which also creates EEPN and hence limits the maximum transmission distance of those systems. In this work, we numerically investigate the optical signal to noise ratio (OSNR) penalties caused by the EEPN in a 3-mode FMF transmission system at 25 GBd for quadrature phase-shift keying (QPSK), 16-quadrature amplitude modulation (QAM), 32-QAM and 64-QAM modulation formats when using the blind phase search (BPS) carrier phase recovery (CPR) algorithm, which has been demonstrated to be both robust and suitable for optical communication systems. Our numerical study assumes a short-span of FMF, modeled in the weakly-coupled regime, and includes two cases; the use of ideal mode-selective de/multiplexers at both ends of the FMF span (model A), and the use of ideal non-mode-selective de/multiplexers (model B). The results show that the EEPN has almost no effect in model A. However, EEPN produces a severe penalty in model B with the onset of the OSNR degradation starting for a DMD spread of the impulse response of about 100 symbols for all modulation formats investigated. The distribution ratio of the amount of phase noise between the transmitter and receiver lasers is also assessed for model B and we confirm that the degradation is mainly due to the phase noise of the LO.
关键词： equalization enhanced phase noise,mode-division multiplexing,few-mode fiber optical communication systems,time-domain MIMO equalization
更新于2025-09-19 17:15:36
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402.7-Tb/s MDM-WDM transmission over weakly coupled 10-mode fiber using rate-adaptive PS-16QAM signals
摘要： The mode-division-multiplexing (MDM) transmission technique using a few-mode fiber (FMF) has been investigated to overcome the theoretical limitation of the transmission capacity of a single-mode fiber. In MDM transmission, multiple-input multiple-output (MIMO) digital signal processing (DSP) is generally required on the receiver side to compensate for the modal crosstalk (XT) between the spatial modes. However, the computational cost is high, especially for high-order MDM systems that use many spatial modes. To reduce the MIMO matrix size, MDM transmission with partial MIMO-based DSP has been proposed using weakly coupled FMFs. The modal XT in such fibers can be suppressed by a special fiber design; however, the modal XT still remains and strongly limits the signal-to-noise-ratio (SNR) and capacity. To further increase the capacity for a given SNR, an optimization of the modulation format is significant. Recently, probabilistic shaping (PS) has received attention since it can gradually change the entropy of a modulation format and maximize the capacity for a given SNR. In this work, we demonstrate weakly coupled 10-mode-multiplexed transmission with four 4×4 MIMOs and two 2×2 MIMOs using rate-adaptive PS-16QAM signals over 48-km FMF, achieving a record transmission capacity of 402.7 Tb/s in 125-μm cladding single-core fiber transmission experiments. Furthermore, we also show the possibility of a further capacity increase by adjusting the entropies of the PS-16QAM signals depending on the spatial mode.
关键词： high-capacity transmission,probabilistic shaping,mode-division multiplexing (MDM),Few-mode-fiber (FMF),rate optimization,coded modulation
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Swift-Hohenberg Equation with Third Order Dispersion for Optical Resonators
摘要： A source-synchronous interconnect using mode-division multiplexing (MDM) for potential use in on-chip applications is experimentally demonstrated using a 3-mode 750 μm Silicon photonics structure. Results are presented for simultaneous transmission of two data channels on two separate modes (bit error rate < 10?12 at 10 Gb/s) sampled by an optically forwarded clock sent on a third separate mode. Performance assessment of the mode assignment for the clock is presented. The investigation shows that an optimum clock placement is important at wavelengths where modal crosstalk is higher. For example, at 1553 nm, the clock’s jitter decreases from 45 ps down to 2.7 ps where the clock is encoded on a mode with high crosstalk (?18.6 dB) to one that has less crosstalk (?28.6 dB). At 1560 nm where modal crosstalk is better, the clock’s jitter is 2.6 ps (?27.8 dB crosstalk) and 1.1 ps (?34 dB crosstalk) without and with optimum clock placement, respectively. With proper clock to mode assignment, the optical interconnect becomes functional across an optical bandwidth of 11 nm enabling MDM–wavelength-division multiplexing architectures.
关键词： source-synchronous links,mode-division multiplexing,Integrated optics,optical interconnects
更新于2025-09-19 17:13:59
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Mode Division Multiplexing Based on Supermodes in Densely Packed Uniform Waveguide Array (DPUWA)
摘要： A multimode bus structure consisting of densely packed uniform waveguide array (DPUWA) with a narrow gap of 150 nm is proposed. A compact and robust mode converter between DPUWA and a conventional wide multimode waveguide is designed with an insertion loss of <0.05 dB and crosstalk of <-20 dB in a wide wavelength range for three TE and three TM modes. Supermodes in the DPUWA can be routed and processed just like the mode in a single-mode waveguide by simply expanding the gap without any mode (de)multiplexer. Based on such ideas, compact DPUWA crossing/bending structures with losses of <0.2/0.09 dB and crosstalks of <-34/-30 dB for three TE modes are achieved.
关键词： mode division multiplexing,waveguide array,multimode bending,multimode crossing
更新于2025-09-19 17:13:59
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Design of weakly coupled ten-vector-mode elliptical-core Bragg fiber for short-haul communication across O+C+L band
摘要： We propose an all-solid weakly coupled elliptical-core Bragg ?ber supporting 10 vector modes (HE11a, HE11b, TM01, HE21a, HE21b, TE01, HE31a, HE31b, EH11a and EH11b) which works over a large range of wavelength across the O?C?L band. We investigate the mode neff, minDneff and con?nement loss of the ?ber under the in?uences of design parameters. The differential mode delay between adjacent propagation modes Aeff and bending loss are also evaluated. the designed ?ber can obtain large minDneff between adjacent vector modes Simulation results indicate that (*4 9 0.0001). Thus, the specially designed Bragg ?ber can be a promising candidate for short-haul MDM communication systems to simplify or eliminate MIMO-DSP.
关键词： Few-mode Bragg ?ber,Weakly coupled,Mode division multiplexing,Short-haul communication
更新于2025-09-16 10:30:52