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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 9 — Apr. 25, 2011
  • pp: 8808–8814
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Transmission of 107-Gb/s mode and polarization multiplexed CO-OFDM signal over a two-mode fiber

An Li, Abdullah Al Amin, Xi Chen, and William Shieh  »View Author Affiliations


Optics Express, Vol. 19, Issue 9, pp. 8808-8814 (2011)
http://dx.doi.org/10.1364/OE.19.008808


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Abstract

In addition to the dimensions of time, frequency, complex constellation, and polarization, spatial mode can be the fifth dimension to be explored for modulation and multiplexing in optical fiber communications. In this paper, we demonstrate successful transmission of 107-Gb/s dual-mode and dual-polarization coherent optical orthogonal frequency-division multiplexing (CO-OFDM) over a 4.5-km two-mode fiber. A mechanically-induced LP01/LP11 mode converter is used as the mode selective element in a spatial-mode multiplexed system.

© 2011 OSA

1. Introduction

The rapid growth of the bandwidth-rich internet applications has driven the research in maximizing the capacity of optical transport. Meanwhile, tremendous breakthrough in high-speed optical transmission networks has been made by utilizing polarization multiplexing, high-order modulation format and coherent optical detection, in both coherent single carrier and CO-OFDM formats [1

1. A. Sano, H. Masuda, T. Kobayashi, M. Fujiwara, K. Horikoshi, E. Yoshida, Y. Miyamoto, M. Matsui, M. Mizoguchi, H. Yamazaki, Y. Sakamaki, and H. Ishii, “69.1-Tb/s (432 x 171-Gb/s) C- and extended L-band transmission over 240 Km using PDM-16-QAM modulation and digital coherent detection,” in Optical Fiber Communication Conference (OFC, 2010), p. PDPB7.

,2

2. Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission with orthogonal-band multiplexing and subwavelength bandwidth access,” J. Lightwave Technol. 28(4), 308–315 (2010). [CrossRef]

]. As the spectral efficiency (SE) in single-mode fiber (SMF) is ultimately limited by the fiber nonlinearity [3

3. P. P. Mitra and J. B. Stark, “Nonlinear limits to the information capacity of optical fibre communications,” Nature 411(6841), 1027–1030 (2001). [CrossRef] [PubMed]

], the natural solution is to use large effective-area SMF [4

4. S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Peckham, “Transmission of a 1.2-Tb/s 24-carrier no-guard-interval coherent OFDM superchannel over 7200-km of ultra-large-area fiber,” in European Conference On Optical Communication, (ECOC 2009), PD2.6.

], or even multimode fiber (MMF) with center launch technique to excite only the fundamental (LP01) mode [5

5. F. Yaman, N. Bai, Y. K. Huang, M. F. Huang, B. Zhu, T. Wang, and G. Li, “10 x 112Gb/s PDM-QPSK transmission over 5032 km in few-mode fibers,” Opt. Express 18(20), 21342–21349 (2010), http://www.opticsinfobase.org/abstract.cfm?URI=oe-18-20-21342. [CrossRef] [PubMed]

,6

6. Y. Ma, Y. Tang, and W. Shieh, “107 Gbit/s transmission over multimode fibre with coherent optical OFDM using centre launching technique,” Electron. Lett. 45(16), 848–849 (2009). [CrossRef]

] to mitigate the nonlinearity penalty. Most importantly, MMF or few-mode fiber (FMF) supports many spatial modes, and therefore the fiber capacity can be increased in theory by taking advantage of this additional degree of freedom in the form of multiple-input multiple-output (MIMO) transmission [7

7. A. Tarighat, R. C. Hsu, A. Shah, A. H. Sayed, and B. Jalali, “Fundamentals and challenges of optical multiple-input multiple-output multimode fiber links,” IEEE Commun. Mag. 45(5), 57–63 (2007). [CrossRef]

]. So far a few proof-of-principle demonstrations have been reported such as 2x2 MIMO transmission over 2.8 kms of 62.5-µm MMF at 0.8 Gb/s in [8

8. H. R. Stuart, “Dispersive multiplexing in multimode optical fiber,” Science 289(5477), 281–283 (2000). [CrossRef] [PubMed]

], direct-detection MIMO 40-Gb/s transmission over 1.1 kms of 62.5 µm-core MMF in [9

9. B. C. Thomsen, “MIMO enabled 40 Gb/s transmission using mode division multiplexing in multimode fiber,” in Optical Fiber Communication (OFC 2010), OThM6.

], and 8-Gb/s transmission over 5 kms of GI-MMF (2x4 MIMO) in [10

10. B. Franz, D. Suikat, R. Dischler, F. Buchali, and H. Buelow, “High speed OFDM data transmission over 5 km GI-multimode fiber using spatial multiplexing with 2x4 MIMO processing,” in European Conference and Exhibition On Optical Communication (ECOC 2010), Tu3.C.4.

]. A laudable goal will be to demonstrate the use of all the degrees of freedom simultaneously.

2. Mode multiplexed transmission

3. Characteristics of the two-mode fiber and mode converter

3.1 Two-mode fiber

3.2 LP01-LP11 mode converter

The critical part of dual-mode transmission depends on excitation and selective detection of the LP01/LP11 mode in the TMF, and the proposed concept to achieve this is shown in Fig. 3
Fig. 3 (a) Mode converter 1 (MC1) with nominal 50% conversion ratio. (b) Mode converter 2 (MC2) with nominal 100% conversion ratio.
. The mode multiplexing and de-multiplexing are done with two mode converters (MC). The MCs are constructed by pressing the TMF against a metallic slab with a surface grating of 500 µm nominal pitch. The actual fiber deformation pitch is then adjusted to the modal beat length of TMF (~520 µm) by optimizing the orientation angle of the slab with reference to the TMF. In order to achieve this, the TMF is first pulled straight and fixed onto a 6cm x 1.9cm x 1.9cm aluminum slab. The TMF and grating together with slabs are then loaded onto two 3-axis translation stages. The effective grating length (interaction length) and force are controlled by moving the stages and/or slabs, eventually optimized for targeted efficiency. MC1 has a nominal conversion ratio of 50%, exciting both the LP01 and LP11 mode equally in the transmission fiber to emulate mode-multiplexing coupler, as shown in Fig. 3(a). Note that only one of the LP11 modes along the direction of the mechanical pressure is excited [12

12. R. C. Youngquist, J. L. Brooks, and H. J. Shaw, “Two-mode fiber modal coupler,” Opt. Lett. 9(5), 177–179 (1984). [CrossRef] [PubMed]

]. The MC2 converts LP01 mode into LP11 and vice versa with high conversion ratio and extinction ratio (ER). After an LP11 mode stripper (MS), only the LP01 component, which is in fact the LP11 during transmission, passes to the receiver. A simple MS eliminates the interference of LP11 component with a rejection ratio of ≥30 dB and allows detection of the transmitted LP01 mode. The MSs used in this experiment are made by wrapping 20 turns of the fiber around a 0.9-cm diameter post [14

14. B. Y. Kim, J. N. Blake, H. E. Engan, and H. J. Shaw, “All-fiber acousto-optic frequency shifter,” Opt. Lett. 11(6), 389–391 (1986). [CrossRef] [PubMed]

]. The excess losses of all the MSs are measured to be within 0.2~0.4 dB. The measured excess losses of MC1 and MC2 are 0.4 and 1.5 dB, respectively. For MC2, an ER (or rejection ratio if used at the receiver) of 22dB/17dB is achieved for the best/worst polarizations, respectively. The inset to the top of Fig. 3(b) shows far field pattern of LP01-to-LP11 conversion case, from which high ER of MC2 can be confirmed.

4. Mode and polarization multiplexed transmission experiment setup at 107 Gb/s

5. Results and discussion

6. Summary

We have demonstrated dual-mode and dual-polarization transmission on a two-mode fiber using an LP01/LP11 mode converter for mode selection. Transmission over a 4.5-km TMF fiber at 107 Gb/s using CO-OFDM is achieved at a spectral efficiency of 5.4 b/s/Hz using QPSK modulation. This is the first experimental demonstration of dual-mode and dual-polarization TMF transmission. Even though the performance is limited by the extinction ratio of the mode converter and the dynamic variation of the spatial modes, the proposed method has the potential to achieve double capacity than that of SMF. Our future work will be focused on using mode couplers/splitters and electronic DSP in place of mode converters, enabling dynamic tracking of the spatial mode variations.

References and links

1.

A. Sano, H. Masuda, T. Kobayashi, M. Fujiwara, K. Horikoshi, E. Yoshida, Y. Miyamoto, M. Matsui, M. Mizoguchi, H. Yamazaki, Y. Sakamaki, and H. Ishii, “69.1-Tb/s (432 x 171-Gb/s) C- and extended L-band transmission over 240 Km using PDM-16-QAM modulation and digital coherent detection,” in Optical Fiber Communication Conference (OFC, 2010), p. PDPB7.

2.

Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission with orthogonal-band multiplexing and subwavelength bandwidth access,” J. Lightwave Technol. 28(4), 308–315 (2010). [CrossRef]

3.

P. P. Mitra and J. B. Stark, “Nonlinear limits to the information capacity of optical fibre communications,” Nature 411(6841), 1027–1030 (2001). [CrossRef] [PubMed]

4.

S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Peckham, “Transmission of a 1.2-Tb/s 24-carrier no-guard-interval coherent OFDM superchannel over 7200-km of ultra-large-area fiber,” in European Conference On Optical Communication, (ECOC 2009), PD2.6.

5.

F. Yaman, N. Bai, Y. K. Huang, M. F. Huang, B. Zhu, T. Wang, and G. Li, “10 x 112Gb/s PDM-QPSK transmission over 5032 km in few-mode fibers,” Opt. Express 18(20), 21342–21349 (2010), http://www.opticsinfobase.org/abstract.cfm?URI=oe-18-20-21342. [CrossRef] [PubMed]

6.

Y. Ma, Y. Tang, and W. Shieh, “107 Gbit/s transmission over multimode fibre with coherent optical OFDM using centre launching technique,” Electron. Lett. 45(16), 848–849 (2009). [CrossRef]

7.

A. Tarighat, R. C. Hsu, A. Shah, A. H. Sayed, and B. Jalali, “Fundamentals and challenges of optical multiple-input multiple-output multimode fiber links,” IEEE Commun. Mag. 45(5), 57–63 (2007). [CrossRef]

8.

H. R. Stuart, “Dispersive multiplexing in multimode optical fiber,” Science 289(5477), 281–283 (2000). [CrossRef] [PubMed]

9.

B. C. Thomsen, “MIMO enabled 40 Gb/s transmission using mode division multiplexing in multimode fiber,” in Optical Fiber Communication (OFC 2010), OThM6.

10.

B. Franz, D. Suikat, R. Dischler, F. Buchali, and H. Buelow, “High speed OFDM data transmission over 5 km GI-multimode fiber using spatial multiplexing with 2x4 MIMO processing,” in European Conference and Exhibition On Optical Communication (ECOC 2010), Tu3.C.4.

11.

K. Y. Song, I. K. Hwang, S. H. Yun, and B. Y. Kim, “High performance fused-type mode-selective coupler using elliptical core two-mode fiber at 1550 nm,” IEEE Photon. Technol. Lett. 14(4), 501–503 (2002). [CrossRef]

12.

R. C. Youngquist, J. L. Brooks, and H. J. Shaw, “Two-mode fiber modal coupler,” Opt. Lett. 9(5), 177–179 (1984). [CrossRef] [PubMed]

13.

B. Y. Kim, J. N. Blake, S. Y. Huang, and H. J. Shaw, “Use of highly elliptical core fibers for two-mode fiber devices,” Opt. Lett. 12(9), 729–731 (1987). [CrossRef] [PubMed]

14.

B. Y. Kim, J. N. Blake, H. E. Engan, and H. J. Shaw, “All-fiber acousto-optic frequency shifter,” Opt. Lett. 11(6), 389–391 (1986). [CrossRef] [PubMed]

OCIS Codes
(060.2330) Fiber optics and optical communications : Fiber optics communications
(060.4080) Fiber optics and optical communications : Modulation

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: February 25, 2011
Revised Manuscript: March 31, 2011
Manuscript Accepted: April 4, 2011
Published: April 20, 2011

Citation
An Li, Abdullah Al Amin, Xi Chen, and William Shieh, "Transmission of 107-Gb/s mode and polarization multiplexed CO-OFDM signal over a two-mode fiber," Opt. Express 19, 8808-8814 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-9-8808


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References

  1. A. Sano, H. Masuda, T. Kobayashi, M. Fujiwara, K. Horikoshi, E. Yoshida, Y. Miyamoto, M. Matsui, M. Mizoguchi, H. Yamazaki, Y. Sakamaki, and H. Ishii, “69.1-Tb/s (432 x 171-Gb/s) C- and extended L-band transmission over 240 Km using PDM-16-QAM modulation and digital coherent detection,” in Optical Fiber Communication Conference (OFC, 2010), p. PDPB7.
  2. Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission with orthogonal-band multiplexing and subwavelength bandwidth access,” J. Lightwave Technol. 28(4), 308–315 (2010). [CrossRef]
  3. P. P. Mitra and J. B. Stark, “Nonlinear limits to the information capacity of optical fibre communications,” Nature 411(6841), 1027–1030 (2001). [CrossRef] [PubMed]
  4. S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Peckham, “Transmission of a 1.2-Tb/s 24-carrier no-guard-interval coherent OFDM superchannel over 7200-km of ultra-large-area fiber,” in European Conference On Optical Communication, (ECOC 2009), PD2.6.
  5. F. Yaman, N. Bai, Y. K. Huang, M. F. Huang, B. Zhu, T. Wang, and G. Li, “10 x 112Gb/s PDM-QPSK transmission over 5032 km in few-mode fibers,” Opt. Express 18(20), 21342–21349 (2010), http://www.opticsinfobase.org/abstract.cfm?URI=oe-18-20-21342 . [CrossRef] [PubMed]
  6. Y. Ma, Y. Tang, and W. Shieh, “107 Gbit/s transmission over multimode fibre with coherent optical OFDM using centre launching technique,” Electron. Lett. 45(16), 848–849 (2009). [CrossRef]
  7. A. Tarighat, R. C. Hsu, A. Shah, A. H. Sayed, and B. Jalali, “Fundamentals and challenges of optical multiple-input multiple-output multimode fiber links,” IEEE Commun. Mag. 45(5), 57–63 (2007). [CrossRef]
  8. H. R. Stuart, “Dispersive multiplexing in multimode optical fiber,” Science 289(5477), 281–283 (2000). [CrossRef] [PubMed]
  9. B. C. Thomsen, “MIMO enabled 40 Gb/s transmission using mode division multiplexing in multimode fiber,” in Optical Fiber Communication (OFC 2010), OThM6.
  10. B. Franz, D. Suikat, R. Dischler, F. Buchali, and H. Buelow, “High speed OFDM data transmission over 5 km GI-multimode fiber using spatial multiplexing with 2x4 MIMO processing,” in European Conference and Exhibition On Optical Communication (ECOC 2010), Tu3.C.4.
  11. K. Y. Song, I. K. Hwang, S. H. Yun, and B. Y. Kim, “High performance fused-type mode-selective coupler using elliptical core two-mode fiber at 1550 nm,” IEEE Photon. Technol. Lett. 14(4), 501–503 (2002). [CrossRef]
  12. R. C. Youngquist, J. L. Brooks, and H. J. Shaw, “Two-mode fiber modal coupler,” Opt. Lett. 9(5), 177–179 (1984). [CrossRef] [PubMed]
  13. B. Y. Kim, J. N. Blake, S. Y. Huang, and H. J. Shaw, “Use of highly elliptical core fibers for two-mode fiber devices,” Opt. Lett. 12(9), 729–731 (1987). [CrossRef] [PubMed]
  14. B. Y. Kim, J. N. Blake, H. E. Engan, and H. J. Shaw, “All-fiber acousto-optic frequency shifter,” Opt. Lett. 11(6), 389–391 (1986). [CrossRef] [PubMed]

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