Transporting Data on the Orbital Angular Momentum of Light. Leslie A. Rusch Canada Research Chair Communications Systems Enabling the Cloud

Transcription

1 Transporting Data on the Orbital Angular Momentum of Light Leslie A. Rusch Canada Research Chair Communications Systems Enabling the Cloud

2 FOR FURTHER READING 2

3 Outline Motivation overcoming the Shannon limit Space Division Multiplexing systems Fibers for SDM Background on fibers Eigenmodes & Few mode fibers Linearly polarized (LP) modes solution Multiple input, multiple output (MIMO) processing Orbital angular momentum modes (OAM) solution OAM fibers why we like them & how we design them OAM at UL OAM transmission experiments Conclusion 3

4 Squeezing Shannon Coaxial cable to fiber optics Increased distance & bandwidth

5 Squeezing Shannon Coaxial cable to fiber optics Increased distance & bandwidth Fast electronics A. Erik, et al., "Roadmap of optical communications," Journal of Optics, vol. 18, p , 2016.

6 Squeezing Shannon Coaxial cable to fiber optics Increased distance & bandwidth Fast electronics Wavelength Multiplexing A. Erik, et al., "Roadmap of optical communications," Journal of Optics, vol. 18, p , 2016.

7 Squeezing Shannon Coaxial cable to fiber optics Increased distance & bandwidth Fast electronics Wavelength Multiplexing Advanced modulation polarization and I/Q A. Erik, et al., "Roadmap of optical communications," Journal of Optics, vol. 18, p , 2016.

8 Squeezing Shannon Coaxial cable to fiber optics Increased distance & bandwidth Fast electronics Wavelength Multiplexing Advanced modulation polarization and I/Q capacity A. Erik, et al., "Roadmap of optical communications," Journal of Optics, vol. 18, p , 2016.

9 Nonlinear Effects Optical fibers are pretty thin 8 micron cores Many wavelengths means high power Megawatts per square centimeter Nonlinear effects Sending more power makes performance worse Not part of Shannon s limit A. D. Ellis, et al., "Performance limits in optical communications due to fiber nonlinearity," Advances in Optics and Photonics, vol. 9, pp , 2017/09/30. 9

10 Nonlinear Effects Optical fibers are pretty thin 8 micron cores Many wavelengths means high power Megawatts per square centimeter Nonlinear effects Sending more power makes performance worse Not part of Shannon s limit A. D. Ellis, et al., "Performance limits in optical communications due to fiber nonlinearity," Advances in Optics and Photonics, vol. 9, pp , 2017/09/30. 10

11 Bandwidth growth and demand Winzer, P.J., "Spatial Multiplexing in Fiber Optics: The 10X Scaling of Metro/Core Capacities," Bell Labs Tech. J., vol.19, pp.22-30,

12 Bandwidth growth and demand Global IP Forcast Winzer, P.J., "Spatial Multiplexing in Fiber Optics: The 10X Scaling of Metro/Core Capacities," Bell Labs Tech. J., vol.19, pp.22-30,

13 Next wave of capacity increase D. J. Richardson, J. M. Fini, and L. E. Nelson, "Space-division multiplexing in optical fibres," Nature Photonics, vol. 7, p. 354, 04/29/online.

14 Next wave of capacity increase D. J. Richardson, J. M. Fini, and L. E. Nelson, "Space-division multiplexing in optical fibres," Nature Photonics, vol. 7, p. 354, 04/29/online.

15 Next wave of capacity increase D. J. Richardson, J. M. Fini, and L. E. Nelson, "Space-division multiplexing in optical fibres," Nature Photonics, vol. 7, p. 354, 04/29/online.

16 Next wave of capacity increase D. J. Richardson, J. M. Fini, and L. E. Nelson, "Space-division multiplexing in optical fibres," Nature Photonics, vol. 7, p. 354, 04/29/online.

17 Next wave of capacity increase space division multiplexing D. J. Richardson, J. M. Fini, and L. E. Nelson, "Space-division multiplexing in optical fibres," Nature Photonics, vol. 7, p. 354, 04/29/online.

18 Outline Motivation overcoming the Shannon limit Space Division Multiplexing systems Fibers for SDM Background on fibers Eigenmodes & Few mode fibers Linearly polarized (LP) modes solution Multiple input, multiple output (MIMO) processing Orbital angular momentum modes (OAM) solution OAM fibers why we like them & how we design them OAM at UL OAM transmission experiments Conclusion 18

19 Fiber bundles? Instead of electronic regeneration Use parallel fiber systems 19

20 Fiber bundles? Instead of electronic regeneration Use parallel fiber systems Increased capacity, but not greener not cheaper Integration drives down price per bit 20

21 Fiber bundles vs. fiber w/multiple channels 21

22 Fiber bundles vs. fiber w/multiple channels Requirements Fiber with multiple channels 22

23 Fiber bundles vs. fiber w/multiple channels Requirements Fiber with multiple channels Integrate transceivers to higher capacity 23

24 Fiber bundles vs. fiber w/multiple channels Requirements Fiber with multiple channels Integrate transceivers to higher capacity Amplifiers 24

25 Fiber bundles vs. fiber w/multiple channels Requirements Fiber with multiple channels Integrate transceivers to higher capacity Amplifiers Switches 25

26 Fiber bundles vs. fiber w/multiple channels Requirements Fiber with multiple channels Integrate transceivers to higher capacity Amplifiers Switches SDM offers higher capacity path to lower cost and power per bit 26

27 Spatial Multiplexing in New Fibers a single core, a single mode 56 Gbaud, 80 λs, DP-16QAM 27

28 Spatial Multiplexing in New Fibers a single core, a single mode multiple cores, each a single mode 28

29 Spatial Multiplexing in New Fibers a single core, a single mode multiple cores, each a single mode a single core, multiple modes 29

30 Spatial Multiplexing in New Fibers a single core, a single mode multiple cores, each a single mode ring core fiber a single core, multiple modes 30

31 Spatial Multiplexing in New Fibers a single core, a single mode multiple cores, each a single mode ring core fiber a single core, multiple modes and eventually. multiple cores, multiple modes 31

32 Spatial Multiplexing in New Fibers What kind of fiber can support the most modes? a single core, multiple modes 32

33 Spatial Multiplexing in New Fibers What kind of fiber can support the most modes? a single core, multiple modes What kind of modes? 33

34 Outline Motivation overcoming the Shannon limit Space Division Multiplexing systems Fibers for SDM Background on fibers Eigenmodes & Few mode fibers Linearly polarized (LP) modes solution Multiple input, multiple output (MIMO) processing Orbital angular momentum modes (OAM) solution OAM fibers why we like them & how we design them OAM at UL OAM transmission experiments Conclusion 34

35 Single mode vs. multimode Fibers used to come in two types Small core (single mode) Large core (multimode) easy to couple, cheap high performance, long distance 35

36 Spatial division multiplexing A new kind of fiber Larger distances & bit rate of SMF Avoid the modal dispersion of MMF Modes as independent, separate channels Need to control the modal interactions Play with dimensions to limit the number of modes Few mode fiber not hundreds, not thousands 36

37 Few mode fibers Modes in fibers: solutions of Maxwell's equations Eigenmodes Building blocks of derivative modes Some solutions of Maxwell s equation flock together mode groups that are interrelated and that interact All depends on physical parameters of the fiber 37

38 SINGLE-MODE OPTICAL FIBER (SMF) Even in single mode fiber two polarizations Gaussian shaped intensity profile 38

39 SINGLE-MODE OPTICAL FIBER (SMF) Even in single mode fiber two polarizations Gaussian shaped intensity profile arrows are polarization 39

40 Few-mode-fiber (FMF) FEW-MODE 8 micron core Six spatial and polarization modes to place information. 40

41 Few-mode-fiber (FMF) FEW-MODE 8 micron core Six spatial and polarization modes to place information. Eigenmodes 41

42 Few mode fibers Modes in fibers Eigenmodes Building blocks of derivative modes Some solutions of Maxwell s equation flock together mode groups that are interrelated and that interact All depends on physical parameters of the fiber Typical fibers have solutions called scalar modes Solution of a simplified version of Maxwell s equation Called the weakly guiding solution Refractive index of cladding Refractive index of core 42

43 Linear-Polarized (LP) Modes Scalar approximation to vector modes Six spatial and polarization paths Boxes indicate near-degenerate modes expect strong coupling 43

44 Linear-Polarized (LP) Modes Scalar approximation to vector modes Six spatial and polarization paths Boxes indicate near-degenerate modes expect strong coupling 44

45 Linear-Polarized (LP) Modes LP 01 LP 11a LP 11b Scalar approximation to vector modes Six spatial and polarization paths Boxes indicate near-degenerate modes expect strong coupling 45

46 Linear-Polarized (LP) Modes LP 01 LP 11a LP 11b Scalar approximation to vector modes Y-pol Six spatial and polarization paths X-pol Boxes indicate near-degenerate modes expect strong coupling 46

47 Outline Motivation overcoming the Shannon limit Space Division Multiplexing systems Fibers for SDM Background on fibers Eigenmodes & Few mode fibers Linearly polarized (LP) modes solution Multiple input, multiple output (MIMO) processing Orbital angular momentum modes (OAM) solution OAM fibers why we like them & how we design them OAM at UL OAM transmission experiments Conclusion 47

48 LP modes or scalar modes Studied for a long time Intensity profiles of light for each mode Degenerate modes Same propagation speed in the fiber Similar geometry to intensity profiles 48

49 LP modes or scalar modes LP for Spatial division multiplexing Modal interactions mix transmitted signals Digital signal processing at RX can undo this Multiple input Multiple output (MIMO) processing 50

50 Electronic MIMO Demultiplexing 52

51 Electronic MIMO Demultiplexing I 1 = h 11 O 1 + h 12 O 2 + h 13 O 3 + h 14 O h 1N O N 53

52 Electronic MIMO Demultiplexing Need the complex filter (time varying amplitudes/phases) for each mode output I 1 = h 11 O 1 + h 12 O 2 + h 13 O 3 + h 14 O h 1N O N 54

53 Electronic MIMO Demultiplexing Number of filters scales with the square of number of modes 55

54 DSP requirements for LP mode multiplexing 57

55 DSP requirements for LP mode multiplexing 58

56 DSP requirements for LP mode multiplexing 59

57 Different markets Long haul Spectral efficiency being maxed out DSP complexity high for dispersion compensation MIMO complexity not significant Data centers MIMO complexity would dominate 60

58 Different markets Long haul Spectral efficiency being maxed out DSP complexity high for dispersion compensation MIMO complexity not significant Data centers MIMO complexity would dominate Opportunities for NEW version of spatial multiplexing 61

59 Outline Motivation overcoming the Shannon limit Space Division Multiplexing systems Fibers for SDM Background on fibers Eigenmodes & Few mode fibers Linearly polarized (LP) modes solution Multiple input, multiple output (MIMO) processing Orbital angular momentum modes (OAM) solution OAM fibers why we like them & how we design them OAM at UL OAM transmission experiments Conclusion 62

60 LP vs. OAM Linearly polarized modes (LP) Well known & studied First solution for SDM Perturbations cause coupling Orbital angular momentum modes (OAM) Recent subject of research New solution for SDM Robust to perturbations 63

61 Eigenmodes of a fiber 64

62 Linearly polarized (LP) Modes Linear combination of fiber eigenmodes LP 01 LP 11x LP 11y LP 21 65

63 Linearly polarized (LP) Modes Linear combination of fiber eigenmodes LP 01 LP 11x LP 11y LP 21 HE 11 TE 01 + HE 21 TM 01 + HE 21 EH 11 + HE 31 66

64 Linearly polarized (LP) Modes Linear combination of fiber eigenmodes crosstalk LP 01 LP 11x LP 11y LP 21 HE 11 TE 01 + HE 21 TM 01 + HE 21 EH 11 + HE 31 67

65 Linearly polarized (LP) Modes Different eigenmodes travel at different speeds LP 01 LP 11x LP 11y LP 21 β 1 β 2, β 3 β 4, β 3 β 5, β 6 HE 11 TE 01 + HE 21 TM 01 + HE 21 EH 11 + HE 31 68

66 Linearly polarized (LP) Modes Different eigenmodes travel at different speeds modal birefringence & crosstalk LP 01 LP 11x LP 11y LP 21 β 1 β 2, β 3 β 4, β 3 β 5, β 6 HE 11 TE 01 + HE 21 TM 01 + HE 21 EH 11 + HE 31 69

67 Linearly polarized (LP) Modes Eigenmodes combined differently for OAM LP 01 LP 11x LP 11y LP 21 β 1 β 2, β 3 β 4, β 3 β 5, β 6 HE 11 TE 01 + HE 21 TM 01 + HE 21 EH 11 + HE 31 OAM(0) OAM(1) OAM(-2) OAM(+2) 70

68 OAM Modes Eigenmodes combined differently for OAM LP 01 OAM 0 OAM 1 OAM -2 OAM 2 β 1 β 3 β 6 β 5 HE 11 HHHH eeeeeeee oooooo jjhhhh 2222 EEEE eeeeeeee jjeeee oooooo 1111 HHHH eeeeeeee oooooo jjhhhh 3333 OAM(0) OAM(1) OAM(-2) OAM(+2) 71

69 OAM Modes Instead of propagation constant, consider mode effective index LP OAM 01 0 LP OAM 11x 1 LPOAM 11y -2 LPOAM 21 2 n eff5 n eff1 n eff3 n eff6 HE 11 HHHH eeeeeeee oooooo jjhhhh 2222 EEEE eeeeeeee jjeeee oooooo 1111 HHHH eeeeeeee oooooo jjhhhh 3333 OAM(0) OAM(1) OAM(-2) OAM(+2) 72

70 Avoid LP modes and favor OAM modes Instead of propagation constant, consider mode effective index Fence off modes Keep effective index separation high to avoid coupling in the fiber n eff1 n eff3 n eff5 n eff6 HE 11 HHHH eeeeeeee oooooo jjhhhh 2222 EEEE eeeeeeee jjeeee oooooo 1111 HHHH eeeeeeee oooooo jjhhhh 3333 OAM(0) OAM(1) OAM(-2) OAM(+2) 73

71 Avoid LP modes and favor OAM modes Instead of group velocity, think of effective index for the mode Fence off modes Keep effective index separation high to avoid coupling in the fiber > n eff 10 4 n eff1 n eff3 n eff5 n eff6 HE 11 HHHH eeeeeeee oooooo jjhhhh 2222 EEEE eeeeeeee jjeeee oooooo 1111 HHHH eeeeeeee oooooo jjhhhh 3333 OAM(0) OAM(1) OAM(-2) OAM(+2) 74

72 FMF for LP modes cannot support OAM modes FMF designed for LP modes violate this condition > 10 n eff 4 75

73 Recap OAM modes can be fenced off from one another LP modes formed from overlapping eigenmodes effective index cannot be shaped to avoid coupling 76

74 OAM characteristics Phase varies in time along propagation axis Yao, Alison M., and Miles J. Padgett. "Orbital angular momentum: origins, behavior and applications." Advances in Optics and Photonics 3, no. 2 (2011):

75 OAM characteristics Phase varies in time along propagation axis Yao, Alison M., and Miles J. Padgett. "Orbital angular momentum: origins, behavior and applications." Advances in Optics and Photonics 3, no. 2 (2011):

76 OAM example 3 rd order mode Annular field intensity profile (m=1) Helical phase front ± il ϕ ( e ) Circular Polarization (±) OAM 3,1 79

77 Why do we call it OAM? 80

78 Why do we call it OAM? conservation of momentum effect 81

79 OAM fibers Index profile matches OAM mode field intensity profile (ring shaped) Vector modes with well separated effective indices avoid degeneracy into LP modes (i.e. at least 10 4 ) Effective index separation high refractive index contrast (violates the weakly guiding approximation) 82

80 Designing a fiber for OAM Ring shaped Large effective index separation 83

81 OAM fibers "Vortex fiber" (2 OAM states) n eff S. Ramanchandran et al., Generation and propagation of radially polarized beams in optical fiber, Optics Letters 34, p.2525 (2009) N. Bozinovic et al., Terabit-Scale Orbital Angular Momentum Mode Division multiplexing in Fibers, Science 340, p (2013) 84

82 Ring core fibers at UL ΔΔnn eeeeee > 10 4 Inverse Parabolic Graded Index Fiber (IPGIF) Smooth gradient profile Gradient varied to achieve Hollow core fiber Hollow core to maximize index contrast Probe maximum number of modes Ring core fiber Analytical tools for designing step index OAM fiber 85

83 Ring core fibers at UL 6µm IPGIF waveguide 2.4µm Hollow core 1.8µm Ring core 23.2µm 5.6µm

84 Inverse Parabolic Graded Index Fiber (IPGIF) N < 0 : curvature parameter 6µm IPGIF Ung, P. Vaity, L. Wang, Y. Messaddeq, L. A. Rusch and S. LaRochelle, Few-mode fiber with inverse-parabolic graded-index profile for transmission of OAMcarrying modes, Optics Express 22, no. 15, pp (July 2014). 87

85 Inverse Parabolic Graded Index Fiber (IPGIF) N: curvature a: core radius n max =n a -n 2 N < 0 : curvature parameter 6µm IPGIF a Ung, P. Vaity, L. Wang, Y. Messaddeq, L. A. Rusch and S. LaRochelle, Few-mode fiber with inverse-parabolic graded-index profile for transmission of OAMcarrying modes, Optics Express 22, no. 15, pp (July 2014). 88

86 IPGIF: Design n eff = (a=3 µm) 89

87 IPGIF: Design n eff = (a=3 µm) Average loss : 8.6 db/km LP 01 loss : 6.5 db/km 90

88 Ring core fibers at UL ΔΔnn eeeeee > 10 4 Inverse Parabolic Graded Index Fiber (IPGIF) Smooth gradient profile Gradient varied to achieve Hollow core fiber Hollow core to maximize index contrast Probe maximum number of modes Ring core fiber Analytical tools for designing step index OAM fiber 91

89 OAM fibers Air-core fiber (12 OAM states) n eff P. Gregg et al., Stable Transmission of 12 OAM States in an Air-Core Fiber, CLEO 2013, paper CTu2K2. 92

90 Hollow-Center Ring-Core Fiber: design Ring-core and trench indices dictated by material constraints highest possible index contrast Hollow core Optimize nn eff > 10 4 Number of supported modes ( 16 OAM states) 2.4µm 23.2µm C. Brunet, P. Vaity, Y. Messaddeq, S. LaRochelle, and L. A. Rusch, Design, fabrication and validation of an OAM fiber supporting 36 states, Optics Express 22, no 21, pp (2014). 93

91 Hollow-Center Ring-Core Fiber 94

92 Hollow-Center Ring-Core Fiber 95

93 Hollow-Center Ring-Core Fiber 96

94 Hollow-Center Ring-Core Fiber 9 OAM orders 17 OAM modes 36 information channels 97

95 Hollow-Center Ring-Core Fiber [ ] 4 = min n eff 98

96 Hollow-Center Ring-Core Fiber : 1 m transmission Right circular polarization Left circular polarization loss few db/m 99

97 Hollow-Center Ring-Core Fiber cut-off 100

98 Ring core fibers at UL ΔΔnn eeeeee > 10 4 Inverse Parabolic Graded Index Fiber (IPGIF) Smooth gradient profile Gradient varied to achieve Hollow core fiber Hollow core to maximize index contrast Probe maximum number of modes Ring core fiber Analytical tools for designing step index OAM fiber 101

99 Ring Core Fiber design tools Simple geometry refractive index fiber cross section 102

100 Ring Core Fiber design tools Simple geometry Analytical tools to choose dimensions 103

101 Ring Core Fiber design tools Simple geometry Analytical tools to choose dimensions OAM modes supported Type Number > 10 n eff 4 104

102 RCF Family analytical tools for cutoff 105

103 RCF Family analytical tools for cutoff scalar equations 106

104 RCF Family analytical tools for cutoff scalar equations vector equations 107

105 RCF Family analytical tools for cutoff scalar equations vector equations C. Brunet, B. Ung, P.-A. Bélanger, Y. Messaddeq, S. LaRochelle, and L. A. Rusch, "Vector mode analysis of ring-core fibers: design tools for spatial division multiplexing," Journal of Lightwave Technology (2014):

106 RCF Family modal maps Geometry Normalized propagation constant Normalized frequency 109

107 Modal map 110

108 Modal map SCF fiber ρ 0 111

109 Modal map LP mode group 112

110 Modal map OAM mode group 113

111 Predicting n eff C. Brunet, B. Ung, L. Wang, Y. Messaddeq, S. LaRochelle, and L. A. Rusch, "Design of a family of ring-core fibres for OAM transmission studies," Optics Express 23.8 (2015):

112 Predicting n eff SCF fiber ρ 0 no fence vector modes mix to form LP 115

113 RCF family 1.8µm Ring core 5.6µm 116

114 Outline Motivation overcoming the Shannon limit Space Division Multiplexing systems Fibers for SDM Background on fibers Eigenmodes & Few mode fibers Linearly polarized (LP) modes solution Multiple input, multiple output (MIMO) processing Orbital angular momentum modes (OAM) solution OAM fibers why we like them & how we design them OAM at UL OAM transmission experiments Conclusion 117

115 First proof of concept Optical control of polarization Mode separation facilitated by this control No MIMO processing required N. Bozinovic, et al., "Terabit-Scale Orbital Angular Momentum Mode Division Multiplexing in Fibers," Science, vol. 340, pp , June 28,

116 Electronic polarization demultiplexing Single port reception 1.4 km transmission Standard 2 2 MIMO No polarization tuning 1.8µm 5.6µm Ring core R. Mirzaei Nejad, et al., "Mode Division Multiplexing using Orbital Angular Momentum Modes over 1.4 km Ring Core Fiber," IEEE/OSA Journal of Lightwave Technology, vol. 34, pp , 15 Sep

117 Commercial Receivers & OAM Fiber Heterogeneous transmission (OOK/QPSK) OAM states separated by commercial 2x2 MIMO 5.6µm 1.8µm Ring core L. A. Rusch, M. M. Rad, K. Allahverdyan, I. Fazal, and E. Bernier, "Carrying data on the orbital angular momentum of light," IEEE Communications Magazine, vol. 56, pp , February

118 Second order OAM 6µm IPGIF OAM2 in IPGIF fiber J. Zhu, et al., "3.36-Tbit/s OAM and Wavelength Multiplexed Transmission over an Inverse-Parabolic Graded Index Fiber," in CLEO 2017, San Jose, p. SW4I.3, May

119 Higher order OAM G. Zhu, et al., "Scalable mode division multiplexed transmission over a 10-km ring-core fiber using high-order orbital angular momentum modes," Optics Express, vol. 26, pp , 2018/01/ MIMO over one OAM order 8 channels OAM 4 OAM 5 122

120 Higher order OAM L. Zhu, et al., "18 km low-crosstalk OAM+WDM transmission with 224 individual channels enabled by a ring-core fiber with large high-order mode group separation," Optics Letters, vol. 43, pp , 2018/04/

121 Higher order OAM L. Zhu, et al., "18 km low-crosstalk OAM+WDM transmission with 224 individual channels enabled by a ring-core fiber with large high-order mode group separation," Optics Letters, vol. 43, pp , 2018/04/15. no MIMO; but mode groups, ¼ of channels exploited 124

122 Higher order OAM L. Zhu, et al., "18 km low-crosstalk OAM+WDM transmission with 224 individual channels enabled by a ring-core fiber with large high-order mode group separation," Optics Letters, vol. 43, pp , 2018/04/15. K. Ingerslev, et al., "12 Mode, MIMO-Free OAM Transmission," in OFC 2017, Los Angeles, p. M2D.1, 2017/03/

123 Higher order OAM K. Ingerslev, et al., "12 Mode, MIMO-Free OAM Transmission," in OFC 2017, Los Angeles, p. M2D.1, 2017/03/ channels OAM 5 OAM 6 OAM 7 no MIMO; stability once modes adjusted for TX 126

124 LP vs. OAM Rich set of components coupling and muxing LP modes from eigenmodes that necessarily interact high crosstalk limited channel count Requires MIMO processing and multiplexed receivers Early stages of research coupling issues still open OAM modes from eigenmodes that can be designed to avoid interaction low crosstalk better channel count DSP & RX simpler No MIMO processing needed Standard

125 LP vs. OAM Rich set of components coupling and muxing LP modes from eigenmodes that necessarily interact high crosstalk limited channel count Requires MIMO processing and multiplexed receivers embrace strong fiber interactions to simplify components; exploit MIMO Different Strategies Early stages of research coupling issues still open OAM modes from eigenmodes that can be designed to avoid interaction low crosstalk better channel count DSP & RX simpler No MIMO processing needed Standard 2 2 target very low fiber interactions, but what about splices, etc.?; avoid MIMO 128

126 Some other promising directions a single core, a single mode ring core fiber a single core, multiple modes 129

127 Some other promising directions a single core, a single mode ring core fiber a single core, multiple modes elliptical core fibers linearly polarized VECTOR modes hold promise 130

128 Conclusion Transmission of OAM modes still very new Design and fabrication of optical fibers is challenging Need to better understand mode-coupling and cross-talk mechanisms - optimize designs - target most appropriate OAM modes Integrated components are needed as well as fibers 131

129 Acknowledgments Alessandro Corsi Dr. Charles Brunet Dr. Reza Nejad Dr. Karen Allahverdyan Dr. Pravin Vaity Dr. Lixian Wang Prof. Sophie LaRochelle Prof. Younès Messaddeq Prof. Bora Ung Irfan Fazal Mohammad Rad Eric Bernier Canada Research Chairs 132