| 51. |
- Dai, Daoxin, et al.
(författare)
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Deeply etched SiO2 ridge waveguide for sharp bends
- 2006
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 24:12, s. 5019-5024
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Tidskriftsartikel (refereegranskat)abstract
- A deeply etched SiO2 ridge waveguide including the buffer, core, and cladding is presented for realizing sharp bends. The present SiO2 ridge waveguide has a strong confinement at the lateral direction, while it has a weak confinement at the vertical direction. Due to the strong confinement, a sharp bend (with a very small bending radius of about 10 mu m) is obtained for an acceptable bending loss. A detailed analysis of the loss in a bent waveguide is given by using a finite-difference method. In order to reduce the transition loss, a narrow bending section with an optimal lateral offset is used. A low leakage loss is obtained by using wide straight waveguides, and linear tapers are used to connect the wide straight section and narrow bent sections.
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| 52. |
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| 53. |
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| 54. |
- Dai, D. X., et al.
(författare)
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Ultrasmall thermally tunable microring resonator with a submicrometer heater on Si nanowires
- 2008
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 26:5-8, s. 704-709
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Tidskriftsartikel (refereegranskat)abstract
- An ultracompact widely tunable thermooptical (TO) microring resonator (MRR) filter based on Si nanowires is presented. The Si nanowire waveguide has a SiO2 insulator, Si core, a SiO2 up-cladding, and a thin metal film at the top. The metal circuit along the microring is used as a submicrometer heater which has the same width as the Si nanowire waveguide. The up-cladding is optimized to reduce the light absorption of the metal as well as to have a good heat-conduction from the heater to the Si core. Two pads used as the contact points for the probes connecting to the electrical power are perpendicularly connected to the microring by using optimized T-junctions (with a low excess loss of about 0.06 dB per T-junction). With such a design, the present thermally tunable microring resonator (MRR) can be fabricated by using a standard fabrication process with a single lithography process, which is much simpler than the fabrication with double lithography processes used for the conventional TO components. Finally, the simulation results show that the designed MRR has a wide tuning range of about 20 nm with a low heating power of 5 mW.
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| 55. |
- de Rossi, S., et al.
(författare)
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Longitudinal mode selection in constricted photonic crystal guides and electrically injected lasers
- 2005
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 23:3, s. 1363-1368
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Tidskriftsartikel (refereegranskat)abstract
- Locally reducing the width of a wide photonic crystal (PhC) waveguide generates a constriction which acts as an internal reflector. We have simulated and measured the spectral behavior of a wide PhC waveguide locally constricted to a narrower PhC waveguide and ended by two cleaved facets, thus generating two coupled cavities. Passive structures as well as electrically injected active structures have been investigated. The multimode behavior of wide PhC waveguides is evidenced to play a deciding role. Modal reflection and transmission at the constriction are simulated and measured on passive PhC waveguides, when varying the constrictions' hole size and length. The spectral behavior of full-PhC electrically pumped lasers including such a constriction is measured and analyzed according to the constriction geometry. Design rules are finally proposed to take advantage of this coupled-cavities behavior for high rejection and high external efficiency monomode laser operation.
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| 56. |
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| 57. |
- Deriushkina, Ekaterina, 1992, et al.
(författare)
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Dual-Comb Swept-Wavelength Interferometry : Theory and Experiment
- 2022
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers Inc.. - 0733-8724 .- 1558-2213. ; 40:19, s. 6508-6516
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Tidskriftsartikel (refereegranskat)abstract
- Much efforts have been put to elaborate and improve different high precision measurement schemes for characterization of advanced photonic devices and optical fibers with increasing bandwidth requirements. In light of this, swept-wavelength interferometry and dual-comb spectroscopy have been extensively applied in characterization procedures. In this paper we present in detail an experimental scheme that combines these two techniques and overcomes their limitations by using a tunable laser source in order to sweep over the frequency comb spacing and capture all intermediate frequencies. We demonstrate full-field broadband measurements over 1.25 THz comb bandwidth with increased frequency resolution, which can be performed in only 5 ms sweep. We also show that the nonlinearity of the laser sweep can be removed without an auxiliary interferometer in the setup.
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| 58. |
- Deriushkina, Ekaterina, 1992, et al.
(författare)
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Dynamic Model for Coupled-Core Fibers
- 2024
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Capacity trends in fiber optical communication systems are closely related to space-division multiplexing (SDM) solutions. A coupled-core fiber (CCF) is one of the most promising SDM candidates for a high data rate transmission because of its tolerance to nonlinear effects and reduced accumulation of group delay spread (GDS) with distance. As the modes of the cores in CCFs are strongly coupled, a communication link requires multiple-input multiple-output (MIMO) processing to recover the input signals. MIMO algorithms, in turn, operate with the different number of finite impulse response taps that represents the memory length of an equalizing filter. The calculation of the number of taps requires the knowledge of GDS, which can be estimated from the received data if a channel model is given. Moreover, if the model accounts for dynamic (time varying) effects it can be used to test the adaptive performance of MIMO equalizer. In this work we propose a straightforward dynamic random coupling model for CCFs. We investigate the dynamic behavior of group delays and impulse responses and also derive and analyze frequency and time autocorrelation functions.
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| 59. |
- Deriushkina, Ekaterina, 1992, et al.
(författare)
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Modeling of 3-Coupled-Core Fiber: Comparison Between Scalar and Vector Random Coupling Models
- 2024
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 42:2, s. 793-801
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Tidskriftsartikel (refereegranskat)abstract
- Simple, fast and accurate channel models can assist not only in a process of manufacturing of novel multi-core fibers, but also in a communication link design, providing a convenient way to investigate different properties of fibers that could be appealing for transmission. Models for coupled-core fibers are in a great demand since this type of the fiber provides advantages for data transmission, e.g. by reducing the effects of modal dispersion and fiber nonlinearity. In this work we present a comparative study of key features in a three coupled-core fiber (3CCF) for scalar and vector random coupling models. Supermodes and their group delays in an unperturbed 3CCF with polarization mode mixing are comprehensively analyzed for the first time. It is shown that birefringence does not impact significantly the group delay values but it may affect the mode mixing. The intensity impulse response and its RMS width were then investigated in a 3CCF with perturbations and compared for two types of models. The shape of the averaged intensity impulse response is found to be very similar for two models and retained for various input polarization states, while in the absence of averaging, the shape of the impulse response strongly depends on the input state of polarization. We show that the calculated RMS widths of the intensity impulse response agree well with theoretical values, as well as between scalar and vector cases.
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| 60. |
- Ding, Jiazheng, et al.
(författare)
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Intra-Channel Nonlinearity Mitigation in Optical Fiber Transmission Systems Using Perturbation-Based Neural Network
- 2022
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 40:21, s. 7106-7116
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a perturbation-based neural network (P-NN) scheme with an embedded bidirectional long short-term memory (biLSTM) layer is investigated to compensate for the Kerr fiber nonlinearity in optical fiber communication systems. Numerical simulations have been carried out in a 32-Gbaud dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) transmission system. It is shown that this P-NN equalizer can achieve signal-to-noise ratio improvements of similar to 1.37 dB and similar to 0.80 dB, compared to the use of a linear equalizer and a single step per span (StPS) digital back propagation (DBP) scheme, respectively. The P-NN equalizer requires lower computational complexity and can effectively compensate for intra-channel nonlinearity. Meanwhile, the performance of P-NN is more robust to the distortion caused by equalization enhanced phase noise (EEPN). Furthermore, it is also found that there exists a tradeoff between the choice of modulation format and the nonlinear equalization schemes for a given transmission distance.
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