Showing papers on "Mode scrambler published in 2022"
TL;DR: In this article , a multi-mode coupler composed of tapered few-mode fiber and silicon integrated multistage waveguide tapers is proposed, which allows direct coupling between high-order fiber modes and highorder waveguide modes with high coupling efficiency and low crosstalk.
Abstract: The mode-division multiplexing technology has been developing slowly in the field of fiber-chip-fiber optical interconnects, mainly limited by the inefficient mode coupling between few-mode fiber and multi-mode photonic chip. Here we propose and design a multi-mode coupler composed of tapered few-mode fiber and silicon integrated multistage waveguide tapers, which allows the direct coupling between high-order fiber modes and high-order waveguide modes with high coupling efficiency and low crosstalk. Based on the edge coupling scheme, the six linear polarization modes (LP01x/y, LP11a x/y, LP11bx/y) in few-mode fiber are firstly coupled into the integrated waveguide with low insertion loss, then the input modes are converted to the desired waveguide modes (TE0, TE1, TE2, TM0, TM1, TM2) with low mode crosstalk relying on the mode evolution principle. The obtained results show that the coupling efficiency is higher than 87%, while for the mode conversion process, the efficiency is higher than 99% and the mode crosstalk is lower than -25 dB. The favorable performance achieved may open new perspectives for diverse mode-division multiplexing applications, enabling efficient capacity scaling in fiber-chip-fiber optical interconnects and optical communication systems.
6 citations
TL;DR: In this paper , a few-mode fiber characterization system with the S2 imaging technique is built and used to obtain accurate mode dispersion of two-mode fibers of different lengths, and various filters are applied to extract the fundamental and high-order modes to acquire mode coupling components.
Abstract: With the widespread use of few-mode fibers, mode characteristics testing becomes essential. In this paper, current few-mode fiber testing techniques are discussed, and the S2 imaging technique is chosen and demonstrated to be capable of few-mode fiber characterization in principle. As a result, the few-mode fiber characterization system with the S2 imaging technique is built and used to obtain accurate mode dispersion of two-mode fibers (a commonly used few-mode fiber) of different lengths. Then, various filters are applied to extract the fundamental and high-order modes to acquire mode coupling components (discrete and distributed mode coupling). The proposed system spectrally characterizes the few-mode fiber by resolving the interference information from the superimposed optical field spatially and has a simple structure and easy operation, which will provide parameter guidance for FMF designing and the FMF sensing experiment optimizing.
2 citations
TL;DR: In this article , a short-distance analog-division multiplexing transmission system based on multimode fiber was designed and built using the VPI optical communication simulation platform, and the experimental results show that the mode coupling has great influence on the anti-noise performance and anti-inter-symbol interference performance of the multimode-based transmission system, and this effect is more obvious in high-order linear polarization mode fiber.
Abstract: The mode coupling and random loss between different modes have important effects on the reliability of the multimode fiber-based mode division multiplexing transmission system. Using the VPI optical communication simulation platform, a short-distance analog-division multiplexing transmission system based on multimode fiber was designed and built. By setting the relevant parameters of mode coupling and random loss caused by bending, the quality of the eye diagram of the received signal is analyzed by the photoelectric signal analyzer at the receiving end. The experimental results show that the mode coupling has great influence on the anti-noise performance and anti-inter-symbol interference performance of the multimode fiber-based transmission system, and the random loss has great influence on the anti-noise performance of the system, this effect is more obvious in high-order linear polarization mode fiber.
1 citations
TL;DR: In this article , an analytical method based on coupled local mode theory is introduced, which can analyze adiabatically tapered multimode fiber with different taper parameters, and the optimal design of tapered fibers is carried out from the perspective of fundamental mode conservation ability.
1 citations
TL;DR: In this paper , the authors demonstrate via simulation and measurement a new, to the best of our knowledge, approach for reconfigurable mode conversion using optical micro-electro-mechanical systems (MEMS) to locally modify the effective index in an asymmetric coupler.
Abstract: Mode-division multiplexing (MDM) enables a large increase in the information-carrying capacity of an optical network. Recently, chip-scale MDM devices that can switch different mode orders to different output waveguides have been demonstrated. However, an important milestone showing dynamically tunable mode-order conversion in a single compact device has so far not been reported. In this work, we demonstrate via simulation and measurement a new, to the best of our knowledge, approach for reconfigurable mode conversion using optical micro-electro-mechanical systems (MEMS) to locally modify the effective index in an asymmetric coupler. Modeling shows that dynamic tuning to increase or decrease the mode order is possible. Measurements on fabricated devices are consistent with simulations of reconfigurable mode conversion based on tunable phase matching. Our experimental results demonstrate reconfigurable TE0-TE2 to TE0-TE1 conversion and validate this new tunable phase-matching approach for mode-division multiplexing.
14 Oct 2022
TL;DR: In this paper , the authors proposed a method to measure the mode coefficient in a few-mode fiber with OAM modes, including LP modes and orbital angular momentum (OAM) modes.
Abstract: We propose a method to measure the mode coefficient in a few-mode fiber with OAM modes. In this method, the eigenmodes are calculated through the optical fiber parameters, including LP modes and orbital angular momentum (OAM) modes. Using a single spatial light modulator (SLM) to load multi-channel computer-generated hologram (CGH), multiple matched filters can be generated at the same time to realize the real-time and accurate measurement of each mode coefficient (mode content and relative phase) and reconstruct the optical field. We validate the method on multimode beams, and the accuracy of mode coefficients measurement is up to 99%. It can be used as adaptive control coefficient to provide solutions for the expansion of photon lantern and other technologies.
TL;DR: In this article , an all-optical fiber-based mode converter was created by mating a self-made 5-mode fiber with a single mode fiber using the fused tapering approach.
16 Dec 2022
TL;DR: In this article , a simple and effective approach for intra-cavity mode control based on optimizing the single-mode power factor, which represents the total power extracted by a single mode from the active medium, is presented.
Abstract: By utilizing customized intra-cavity optical elements including graded-phase mirrors, variable reflectivity mirrors, aspherical mirrors, diffractive optical elements and spatial light modulators, the mode discrimination of the cavity is enhanced and a pre-determined transverse mode, usually flat-top beams such as super-Gaussian beams or flattened- Gaussian beams, can be generated in the cavity. The design of such laser cavities oscillating in a predetermined transverse mode is commonly based on the concept of phase conjugation, whereby the desired phase profile of optical element is obtained by reversely propagating the predetermined transverse mode and creating a conjugate field to propagate back. However, this procedure is only accurate under the assumption that the mirror size is infinite and the propagation process is in a lossless manner. Moreover, the parameters of the pre-determined mode, such as beam size and amplitude distribution, must be carefully chosen or else non-negligible errors would occur due to finite-size apertures and associated truncation. Here, we report on a simple and effective approach for intra-cavity mode control based on optimizing the single-mode power factor, which represents the total power extracted by a single mode from the active medium. By optimizing the single-mode power factor of the desired mode, the cavity can be designed to operate in mono-mode, increasing the mode purity significantly. Our method is verified on a digital laser with a spatial light modulator as the rear mirror and the loaded phase profile is acquired by a simulated annealing algorithm. As a result, when the single-mode power factor of TEM00 mode is optimized, the resonator operates in a single fundamental mode. When the single-mode power factor of the vortex mode with a topological charge of 1 is optimized, the output mode purity is close to 100%.
TL;DR: In this article , the authors proposed a method to realize compact, scalable and flexible mode filters based on backward mode conversion gratings elaborately embedded in a multimode waveguide, which is highly scalable for realizing a higher-order mode-pass or band-mode-pass filter of any order.
Abstract: Mode filters are fundamental elements in a mode-division multiplexing (MDM) system for reducing modal cross-talk or realizing modal routing. However, the previously reported silicon mode filters can only filter one specific mode at a time and multiple modes filtering usually needs a cascade of several filters, which is adverse to highly integrated MDM systems. Here, we propose a unique concept to realize compact, scalable and flexible mode filters based on backward mode conversion gratings elaborately embedded in a multimode waveguide. Our proposed method is highly scalable for realizing a higher-order-mode-pass or band-mode-pass filter of any order and capable of flexibly filtering one or multiple modes simultaneously. We have demonstrated the concept through the design of four filters for different order of mode(s) and one mode demultiplexer based on such a filter, and the measurement of two fabricated 11μm length filters (TE1-pass/TE2-pass) show that an excellent performance of insertion loss <1.0dB/1.5dB and extinction ratio >29dB/28.5dB is achieved over a bandwidth of 51.2nm/48.3nm, which are competitive with the state-of-the-art.
TL;DR: In this paper , a reconfigurable and tunable few-mode fiber-based microwave photonic filter is proposed, which can be implemented by changing the number of excited modes and the length of the fewmode fiber.
TL;DR: In this article , a high-order mode fiber laser based on few-mode fiber gratings is proposed and experimentally demonstrated, which can be applied to optical communication systems based on WDM.
Abstract: We propose and experimentally demonstrate a high-order mode fiber laser based on few-mode fiber gratings. The fiber laser has the structure of three sub-ring-cavities. LP01 mode, LP11 mode and LP21 mode can be obtained by different few-mode long-period fiber gratings. The reflection of LP01 mode, LP11 mode and LP21 mode can be realized by different few-mode fiber Bragg gratings. Therefore, the simultaneous lasing of LP01 mode, LP11 mode and LP21 mode at the same wavelength can be achieved. A few-mode fiber Bragg grating functions as a discrete filter. By adjusting a polarization controller, switchable output among single-, dual- and triple-wavelength lasing can be realized, and three wavelengths correspond to LP01 mode, the mixing of LP01 mode and LP11 mode, and LP11 mode. Therefore, the simultaneous lasing of different modes at the same wavelength, and the simultaneous lasing of different modes at different wavelengths can be achieved in this fiber laser, which can be applied to optical communication systems based on mode-division multiplexing-wavelength-division multiplexing.
TL;DR: In this article , a programmable high-order mode control method that can be implemented in high-power fiber lasers is presented. And the mode patterns are stable and dynamically switchable, which is expected to possess good application value in optical tweezers, fiber communication, laser material processing and other research fields.
Abstract: We demonstrate a programmable high-order mode control method that can be implemented in high-power fiber lasers. 2 W average-power mode-locked pulses are obtained based on a mode-locked fiber laser working in dissipative soliton resonance regime. The fundamental mode (LP01) is fully or partially converted to the high-order modes (LP11a/b) via an acoustically-induced fiber grating. The mode-superposition fields are recorded using an optical 4f system, and mode components are subsequently analyzed by a mode decomposition algorithm. Our experiments suggest that the mode patterns are stable and dynamically switchable. The method is expected to possess good application value in optical tweezers, fiber communication, laser material processing and other research fields.
TL;DR: In this article , a reconfigurable structure of a higher-order mode pass filter consisting of two tunable mode converters and a directional coupler in a three-mode planar waveguide platform is proposed.
11 Aug 2022
TL;DR: In this paper , phase matching for four-wave mixing using one, two, three, and four waveguide modes is compared using numerical optimizations and an estimate of the generated idler power.
Abstract: We compare phase matching for four-wave mixing using one, two, three, and four waveguide modes. For the comparison, we use numerical optimizations and an estimate of the generated idler power. We present results for few-mode fibers and nano-rib waveguides and show that for both waveguide types, four-wave mixing bandwidths and idler powers are best for one- and two-mode operation and that four-mode four-wave mixing is not feasible at all. Some nano-rib waveguides support three-mode four-wave mixing, albeit with much reduced bandwidth and reduced idler power.
TL;DR: In this article , the modal energy flow of the femtosecond-pulsed beam self-cleaning on LP11 mode with the influence of different factors such as the initial fraction of LP 11 mode, initial peak power, distribution of high-order modes and the numerical aperture of the fiber was investigated.
Abstract: We investigate the modal energy flow of the femtosecond-pulsed beam self-cleaning on LP11 mode with the influence of different factors such as the initial fraction of LP11 mode, initial peak power, distribution of high-order modes and the numerical aperture of the fiber. It is interesting that there is a critical value of the initial peak power, Pcr, which is the watershed, not only in the quantitatively dominant transverse mode converting from LP11 mode to LP01 mode, but also in the behavior of HOMs of the transition from Attractor to chaos. Our simulation results may provide a novel perspective to understanding the beam self-cleaning on LP11 mode.
TL;DR: In this paper , the authors investigated the characteristics and optimization method of FDS for the FMF link under the dynamic spatial mode crosstalk cumulative effect, and proposed an optimization method based on high-order mode waveform reconstruction.
Abstract: Due to the cumulative effect of dynamic spatial mode crosstalk, it is difficult to obtain the amplitude distribution of backscattering with high purity. Hence, the fault detection sensitivity (FDS) of the few-mode fiber (FMF) link is deteriorated, and the fault location accuracy is limited. This work investigates the characteristics and optimization method of FDS for the FMF link under the dynamic spatial mode crosstalk cumulative effect. We establish a mathematical model and analyze the influence of dynamic spatial mode crosstalk on the FDS of LP01, LP11a, and LP11b modes. The crosstalk mentioned above is caused by different splice misalignments and rotation angles during FMF fusion splicing. The results show that the dynamic spatial mode crosstalk has a great influence on the detection sensitivity of the high-order spatial mode. To solve this problem, the FDS optimization method is proposed based on high-order mode waveform reconstruction. The coupling efficiency matrix at the fusion splice point is estimated by the Rayleigh backscattering waveform of each mode, and the Rayleigh backscattering waveform of high-order spatial modes is reconstructed. The simulation experiment is carried out based on the above theoretical model. The results show that the proposed method can effectively eliminate the influence of the cascading dynamic crosstalk accumulation on the fault loss of the high-order spatial mode, and then optimize the FDS of the FMF link. This study offers new opportunities to develop FMF fault detection devices with high detection sensitivity performance.
TL;DR: In this paper , a vector mode conversion approach based on tilted asymmetric fiber Bragg grating (TAFBG) written in vortex fiber is investigated, and the mode coupling properties of TAFBG are numerically analyzed.
21 Mar 2022