| Mode-Diversity Multiplexing over Few-Mode Fibres (MDM-FMF) |
Mode-diversity multiplexing (MDM) over few-mode fibres (FMFs) has the potential to dramatically increase the transmission capacity per fibre, avoiding the impending capacity crunch of standard single-mode fibres. Two techniques to reduce the differential mode delay of FMFs are proposed, enabling the transmission of MDM signals over ultra-long haul distances.
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Mode field spatial distribution.
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| General motivation and objective of the project: |
The ever growing demand for higher data rate is rapidly exhausting the capacity available for single-mode fibres (SMFs). During the last years, only a marginal increase in the maximum bit rate distance product using SMFs was observed, since the nonlinear Shannon limit is being reached. Moreover, it has been demonstrated that even if significant improvements of standard SMFs (SSMFs) are achieved, the capacity increase per fibre is limited.
Mode-division multiplexing (MDM) over few-mode fibres (FMFs) is emerging as an attractive solution for the required capacity increase with potential cost, space, and energy savings. An N-fold capacity increase, with N equal to the number of independent modes of the FMF, is obtained using MDM. However, FMFs require the usage of multiple-input multiple-output (MIMO) equalization as it needs to compensate for the combined effect of differential mode delay (DMD) and modal crosstalk (XT), which originates a channel impulse response (CIR) spread over time. In order to reduce the equalizer complexity the fibre DMD has to be reduced.
In the literature, different schemes to reduce or compensate DMD have been proposed: the usage of inherently low DMD FMFs (ILD-FMFs); the usage of FMFs with positive DMD followed by FMFs with negative DMD, usually referred as DMD compensated FMFs (DC-FMFs); or the usage of mode permutation within the transmission fibre, which averages the modes group velocities, thereby reducing the CIR length. The reported ILD-FMFs and DC-FMFs are not suitable for ultra-long haul transmission due to high DMD variation within the C+L band. Regarding the mode permutation scheme, an increase of the maximum distance reach by a factor of 5 has been shown. However, a practical implementation of mode permutation is still missing.
The main objectives of this work are the proposal of design rules for FMFs with an arbitrary DMD flattened over the C+L band, and the investigation of schemes for the practical implementation of mode permutation.
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Figure 1. Refractive-index profile composed by a graded-index core and a cladding trench.
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| Main work description and achievements: |
The refractive index profile considered to obtain an arbitrary DMD flattened over the C+L band is composed by a graded core and a cladding trench (Figure 1). The proposed optimization process allows obtaining FMFs with negligible DMD over the C+L band (ILD-FMFs). Moreover, it has been shown that it is possible to obtain an arbitrary DMD (positive or negative) flattened over the C+L band (allowing the design of DC-FMFs), varying only the core grading exponent. This result allows establishing a simple design rule that eases the manufacturing process and the splicing of FMFs with different DMD levels. However, the existing manufacturing process does not have the required precision to guarantee the designed DMD.
In order to improve the distance reach of MDM transmission systems using ILD-FMFs or DC-FMFs with non-negligible levels of DMD, we propose the introduction of displaced core fibre splices along the transmission fibre as a practical scheme to implement discrete mode permutation. The fibre splices introduce modal XT which averages the modes group velocities, thereby reducing the CIR length. However, fibre splices also introduce mode dependent losses (MDL) degrading the receiver equalizer performance. The trade-off between splice XT and MDL was optimized. Figure 2 shows distance reach as a function of splice XT. The results show that the distance reach can be increased by a factor ranging from 1.6 to 1.9 for the ILD-FMFs and DC-FMFs transmission systems. The maximum distance reach achieved for the optimum configuration is higher than 5000 km.
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Figure 2. Distance reach as a function of splice XT.
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Coriant Portugal and Fundação para a Ciência e Tecnologia (FCT) under the PhD grant SFRH/BDE/51094/2010 and Strategic Project PEST-OE/EEI/LA0008/2013.
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Papers in Journals
- Ferreira, F. M.; Fonseca, D.F.; Silva, H. A.;
"Design of Few-Mode Fibers with M-modes and Low Differential Mode Delay", Journal of Lightwave Technology , Vol. 32, No. 3, pp. 353 - 360, February,2014.
- Ferreira, F. M.; Fonseca, D.F.; Silva, H. A.;
"Design of Few-Mode Fibers with Arbitrary and Flattened Differential Mode Delay", IEEE Photonics Technology Letters, Vol. 25, No. 5, pp. 438 - 441, March,2013.
Abstract
- A. Lobato; Ferreira, F. M.; B. Inan; A. Adhikari ; M. Kuschnerov;
"Maximum-Likelihood Detection in Few-Mode Fiber Transmission with Mode-Dependent Loss", IEEE Photonics Technology Letters, Vol. 25, No. 12, pp. 1095 - 1098, June,2013.
Abstract
- Ferreira, F. M.; Fonseca, D.F.; A. Lobato; B. Inan; Silva, H. A.;
"Reach Improvement of Mode Division Multiplexed Systems using Fiber Splices", IEEE Photonics Technology Letters, Vol. 25, No. 12, pp. 1091 - 1094, June,2013.
Abstract
- Ferreira, F. M.; S. L. Jansen; Monteiro, P.; Silva, H. A.;
"Nonlinear Semi-Analytical Model for Simulation of Few-Mode Fiber Transmission", IEEE Photonics Technology Letters, Vol. 24, No. 4, pp. 240 - 242, February,2012.
Abstract
- B. Inan; B. Spinnler; Ferreira, F. M.; D. B. van den Borne; A. Lobato;
"DSP complexity of mode-division multiplexed receivers", Optics Express, Vol. 20, No. 9, pp. 10859 - 10869, April,2012.
- A. Lobato; Ferreira, F. M.; M. Kuschnerov; D. B. van den Borne; S. L. Jansen;
"Impact of mode coupling on the mode-dependent loss tolerance in few-mode fiber transmission", Optics Express, Vol. 20, No. 28, pp. 29776 - 29783, December,2012.
Abstract
Papers in Conference Proceedings
- Ferreira, F. M.; D. Fonseca; Silva, H. A.;
"Design of Few-Mode Fibers with Low and Flattened Differential Modal Delay", Proc Conf. on Telecommunications - ConfTele, Castelo Branco, Portugal, Vol. -, pp. 1 - 4, May, 2013.
Abstract
- Ferreira, F. M.; Fonseca, D.F.; Silva, H. A.;
"On the Dependence of Differential Mode Delay in Few-Mode Fibers on the Number of Modes", Proc International Conf. on Transparent Optical Networks - ICTON, Cartagena, Spain, Vol. -, pp. 1 - 4, June, 2013.
Abstract
- A. Lobato; Ferreira, F. M.; J. Rabe; B. Inan; A. Adhikari ; M. Kuschnerov;
"On the Mode-Dependent Loss Compensation for Mode-Division Multiplexed Systems ", Proc International Conf. on Transparent Optical Networks - ICTON, Cartagena, Spain, Vol. -, pp. 1 - 4, June, 2013.
Abstract
- A. Lobato; Ferreira, F. M.; J. Rabe; B. Inan; A. Adhikari ; M. Kuschnerov;
"Mode-Dependent-Loss Mitigation for Mode-Division Multiplexed Systems", Proc OSA Signal Processing in Photonic Communications - SPPCom, Rio Grande, Puerto Rico, Vol. -, pp. 1 - 3, July, 2013.
Abstract
- A. Lobato; Ferreira, F. M.; J. Rabe; M. Kuschnerov; B. Spinnler; B. Lankl;
"Mode Scramblers and Reduced-Search Maximum-Likelihood Detection for Mode-Dependent-Loss-Impaired Transmission", Proc European Conf. on Optical Communications - ECOC, London, United Kingdom, Vol. Th.2.C.3, pp. - - -, September, 2013.
Abstract
- Ferreira, F. M.; D. B. van den Borne; Silva, H. A.; Monteiro, P.;
"Crosstalk Optimization of Phase Masks for Mode Multiplexing in Few Mode Fibers", Proc OSA Optical Fiber Communications - OFC, Los Angeles, United States, Vol. 1, pp. 1 - 3, March, 2012.
Abstract
- B. Inan; B. Spinnler; Ferreira, F. M.; A. Lobato;
"Equalizer Complexity of Mode Division Multiplexed Coherent Receivers", Proc OSA Optical Fiber Communications - OFC, Los Angeles, United States, Vol. 1, pp. 1 - 3, March, 2012.
Abstract
- B. Inan; B. Spinnler; Ferreira, F. M.; A. Lobato;
"Equalizer Complexity of Mode Division Multiplexed Coherent Receivers", Proc OSA Optical Fiber Communications - OFC, Los Angeles, United States, Vol. 1, pp. 1 - 3, March, 2012.
Abstract
- A. Lobato; Ferreira, F. M.; B. Inan;
"The Impact of Differential Mode Delay on Mode-Division Multiplexed Coherent Optical OFDM Transmission", Proc OSA Optical Fiber Communications - OFC, Los Angeles, United States, Vol. 1, pp. 1 - 3, March, 2012.
Abstract
- B. Inan; S. L. Jansen; B. Spinnler; Ferreira, F. M.; D. B. van den Borne; A. Lobato; A. Adhikari ; V. S. Sleiffer;
"DSP Requirements for MIMO Spatial Multiplexed Receivers", Proc Summer Topical Meetings - LEOS , Seatle, United States, Vol. -, pp. - - -, July, 2012.
- Ferreira, F. M.; Monteiro, P.; Silva, H. A.;
"Semi-Analytical Model for Linear Modal Coupling in Few-Mode Fiber Transmission", Proc International Conf. on Transparent Optical Networks - ICTON, Coventry , United Kingdom, Vol. -, pp. - - -, July, 2012.
Abstract
- B. Inan; B. Spinnler; Ferreira, F. M.; D. B. van den Borne; S. L. Jansen;
"Complexity Analysis for Higher Order Few Mode Fiber Equalizers", Proc European Conf. on Optical Communications - ECOC, Amsterdam, Netherlands, Vol. 0, pp. 0 - 0, September, 2012.
- A. Lobato; Ferreira, F. M.; M. Kuschnerov; D. B. van den Borne; S. L. Jansen; B. Spinnler;
"Impact of Mode Coupling on the Mode-Dependent Loss Tolerance in Few-Mode Fiber Transmission", Proc European Conf. on Optical Communications - ECOC, Amsterdam, Netherlands, Vol. 0, pp. 0 - 0, September, 2012.
- Ferreira, F. M.; S. L. Jansen; Monteiro, P.; Silva, H. A.;
"Nonlinear Model for Simulation of Two-Mode Fiber Transmission", Proc Symp. on Enabling Optical Networks - SEON, Aveiro, Portugal, Vol. 1, pp. 1 - 4, July, 2011.
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