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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 21 — Oct. 21, 2013
  • pp: 25113–25119
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Mode multi/demultiplexer based on cascaded asymmetric Y-junctions

Weiwei Chen, Pengjun Wang, and Jianyi Yang  »View Author Affiliations


Optics Express, Vol. 21, Issue 21, pp. 25113-25119 (2013)
http://dx.doi.org/10.1364/OE.21.025113


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Abstract

A mode-(de)multiplexer with low loss and large spectral bandwidth is proposed. The device is designed by utilizing a structure with cascaded asymmetric Y-junctions. By carefully controlling the widths of the wide and narrow arms of the Y-junctions, the fundamental mode of a narrow arm excites the higher-order mode of its stem in the multiplexing case, and a high-order mode of the stem separated from other lower-order modes evolves into the fundamental mode of the narrow arm in the demultiplexing case. As an example, a 1 × 4 mode-(de)multiplexer is analyzed by using the beam propagation method. Simulation results show the demultiplexed crosstalk is lower than –21.8 dB, under a common spectral bandwidth of 140 nm. The insertion loss is negligible.

© 2013 Optical Society of America

1. Introduction

As a key component in MDM transmission, mode (de)multiplexers have attracted significant attention in recent years. Previously, several mode (de)multiplexers have been reported based on Y-splitter, multimode interference (MMI), asymmetrical directional couplers (ADCs) and grating-assisted contra-directional couplers (GACCs). The mode (de)multiplexers based on Y-splitter and MMI only handle two optical modes with the same polarization [3

3. J. D. Love and N. Riesen, “Single-, Few-, and Multimode Y-Junctions,” J. Lightwave Technol. 30(3), 304–309 (2012). [CrossRef]

5

5. T. Uematsu, Y. Ishizaka, Y. Kawaguchi, K. Saitoh, and M. Koshiba, “Design of a Compact Two-Mode Multi/Demultiplexer Consisting of Multimode Interference Waveguides and a Wavelength-Insensitive Phase Shifter for Mode-Division Multiplexing Transmission,” J. Lightwave Technol. 30(15), 2421–2426 (2012). [CrossRef]

]. The mode (de)multiplexers based on ADCs and GACCs can achieve more than four channels. However, the mode (de)multiplexer based on ADCs requires accurate control of the coupling length and coupling strength [6

6. D. Dai, “Silicon mode-(de)multiplexer for a hybrid multiplexing system to achieve ultrahigh capacity photonic networks-on-chip with a single-wavelength-carrier light,” Asia Communications and Photonics Conference (2012). [CrossRef]

], and the one based on GACCs has a limited bandwidth [7

7. H. Y. Qiu, H. Yu, T. Hu, G. M. Jiang, H. F. Shao, P. Yu, J. Y. Yang, and X. Q. Jiang, “Silicon mode multi/demultiplexer based on multimode grating-assisted couplers,” Opt. Express 21(15), 17904–17911 (2013). [CrossRef] [PubMed]

].

Y-junctions are commonly used as broadband power dividers [8

8. M. Izutsu, Y. Nakai, and T. Sueta, “Operation mechanism of the single-mode optical-waveguide Y junction,” Opt. Lett. 7(3), 136–138 (1982). [CrossRef] [PubMed]

]. Asymmetric Y- junctions where each arm has a different effective index can be designed to act as polarization splitters, mode combiners, mode splitters, wavelength multiplexers and mode sorters [9

9. J. Vandertol and J. H. Laarhuis, “A polarization splitter on LINBO3 using only titanium diffusion,” J. Lightwave Technol. 9(7), 879–886 (1991). [CrossRef]

17

17. N. Riesen and J. D. Love, “Design of mode-sorting asymmetric Y-junctions,” Appl. Opt. 51(15), 2778–2783 (2012). [CrossRef] [PubMed]

]. For the case of a two-mode mode-sorting asymmetric Y-junction, an arm can adiabatically excite the first odd (even) mode of the Y-junction stem [4

4. J. B. Driscoll, R. R. Grote, B. Souhan, J. I. Dadap, M. Lu, and R. M. Osgood Jr., “Asymmetric Y junctions in silicon waveguides for on-chip mode-division multiplexing,” Opt. Lett. 38(11), 1854–1856 (2013). [CrossRef] [PubMed]

,16

16. W. K. Burns and F. Milton, “Mode conversion in planar-dielectric separating waveguides,” IEEE J. Quantum Electron. 11(1), 32–39 (1975). [CrossRef]

]. When the theory of mode-sorting is applied to multi-arm asymmetric Y-junctions with multiple modes in the stem, the separation of more than three or four modes is practically limited because of the restriction on insertion loss and the length of the Y-junction, which is approximately proportional to the fourth power of the number of modes [17

17. N. Riesen and J. D. Love, “Design of mode-sorting asymmetric Y-junctions,” Appl. Opt. 51(15), 2778–2783 (2012). [CrossRef] [PubMed]

,18

18. J. D. Love, R. W. C. Vance, and A. Joblin, “Asymmetric, adiabatic multipronged planar splitters,” Opt. Quantum Electron. 28(4), 353–369 (1996). [CrossRef]

].

2. Operation principle

3. Structure description and analysis

The width W1 and the length L0 dependence of the optical transmission of the first-stage asymmetric Y-junction for the cases of inputting the fundamental mode into ports Input1 and Input2 are shown in Fig. 3.
Fig. 3 Optical transmission of the first-stage asymmetric Y-junction, for the cases of inputting the fundamental mode into ports Input1 and Input2, when (a) L0 = 5000 μm, W1 changes (b) W1 = 13 μm, L0 changes. The dashed and solid curves are for the cases of putting the fundamental mode into ports Input1 and Input2, respectively.
Note that in Figs. 3(a) and 3(b), as the width W1 increases, the output power of the second mode excited by putting the fundamental mode into port Input2 is significantly increased. In addition, the output power of the non-target excited modes can be well suppressed with increasing length L0. When the width W1 and the length L0 are chosen to be 13 μm and 5000 μm, the output power of the second modes are effectively suppressed and the fundamental and first modes have good extinction ratios. Therefore, the width W1 and the length L0 are set to be 13 μm and 5000 μm in our simulation with an extinction ratio of 41.0 dB for the fundamental mode and an extinction ratio of 41.2 dB for the first mode at the wavelength of 1550 nm.

Fig. 4 Optical transmission of the second-stage asymmetric Y-junction, for the cases of inputting fundamental mode into ports Input1, Input2, and Input3, when (a) W1 = 13 μm, L1 = 5000μm, W2 changes (b) W1 = 13 μm, W2 = 22 μm, L1 changes. The solid, dash and dot curves represent the cases of putting the fundamental mode into ports Input1, Input2 and Input3 respectively.
Figure 4 shows the width W2 and the length L1 dependence of the optical transmission of the second-stage asymmetric Y-junction, for the cases of inputting the fundamental mode into ports Input1, Input2, and Input3. From Fig. 4(a), the output power of the third mode excited by putting the fundamental mode into the Input3 port increases rapidly with increasing width W2. In Fig. 4(b), as the length L1 increases, the extinction ratio of the second mode excited by putting the fundamental mode into the Input3 port is getting larger until the advent of the inflection point. Therefore, in order to reduce the mode coupling and improve the extinction ratio, the width W2 and the length L1 are respectively set to be 22 μm and 5000 μm with an extinction ratio of 33.2 dB for the second mode at the wavelength of 1550 nm.

Fig. 6 BPM simulation of the designed 1 × 4 CAYJs mode-(de)multiplexer for putting the fundamental mode into the access waveguides at the wavelength of 1550 nm. (a) Input1 port (b) Input2 port (c) Input3 port (d) Input4 port (e) all input ports.
From Fig. 6, one can see that the higher-order modes are excited when the fundamental mode is launched into the ports Input1, input2, input3 and input4 at the wavelength of 1550 nm. A three-dimensional BPM is used in the simulation.
Fig. 7 Wavelength dependence of the designed 1 × 4 CAYJs mode-(de)multiplexer, when the input port is (a) port Input1 (b) port Input2 (c) port Input3 and (d) port Input4. The rectangle, circle, diamond and triangle traces represent the transmission to ports Output1, Output2, Output3 and Output4, respectively.
Figure 7 shows the spectral responses of the designed 1 × 4 CAYJs mode-(de) multiplexer by putting fundamental modes into the access waveguides. The calculated dominant optical power at the Output1, Output2, Output3, and Output4 ports of the demultiplexer are denoted with rectangle, circle, diamond and triangle traces respectively. Figures 7(a)-7(d) represent the transmission spectra from ports Input1, Input2, Input3, and Input4. It can be found within a bandwidth from 1520 nm to 1660 nm, the best demultiplexed crosstalk of different modes is up to −57.0 dB, while in the worst case it is −21.8 dB. Simulation results show that the insertion loss of the designed mode-(de)multiplexer varies from 0.01 dB to 0.03 dB at a wavelength of 1550 nm, depending on I/O port.

4. Conclusion

Acknowledgments

References and links

1.

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

2.

S. Berdagué and P. Facq, “Mode division multiplexing in optical fibers,” Appl. Opt. 21(11), 1950–1955 (1982). [CrossRef] [PubMed]

3.

J. D. Love and N. Riesen, “Single-, Few-, and Multimode Y-Junctions,” J. Lightwave Technol. 30(3), 304–309 (2012). [CrossRef]

4.

J. B. Driscoll, R. R. Grote, B. Souhan, J. I. Dadap, M. Lu, and R. M. Osgood Jr., “Asymmetric Y junctions in silicon waveguides for on-chip mode-division multiplexing,” Opt. Lett. 38(11), 1854–1856 (2013). [CrossRef] [PubMed]

5.

T. Uematsu, Y. Ishizaka, Y. Kawaguchi, K. Saitoh, and M. Koshiba, “Design of a Compact Two-Mode Multi/Demultiplexer Consisting of Multimode Interference Waveguides and a Wavelength-Insensitive Phase Shifter for Mode-Division Multiplexing Transmission,” J. Lightwave Technol. 30(15), 2421–2426 (2012). [CrossRef]

6.

D. Dai, “Silicon mode-(de)multiplexer for a hybrid multiplexing system to achieve ultrahigh capacity photonic networks-on-chip with a single-wavelength-carrier light,” Asia Communications and Photonics Conference (2012). [CrossRef]

7.

H. Y. Qiu, H. Yu, T. Hu, G. M. Jiang, H. F. Shao, P. Yu, J. Y. Yang, and X. Q. Jiang, “Silicon mode multi/demultiplexer based on multimode grating-assisted couplers,” Opt. Express 21(15), 17904–17911 (2013). [CrossRef] [PubMed]

8.

M. Izutsu, Y. Nakai, and T. Sueta, “Operation mechanism of the single-mode optical-waveguide Y junction,” Opt. Lett. 7(3), 136–138 (1982). [CrossRef] [PubMed]

9.

J. Vandertol and J. H. Laarhuis, “A polarization splitter on LINBO3 using only titanium diffusion,” J. Lightwave Technol. 9(7), 879–886 (1991). [CrossRef]

10.

W. M. Henry and J. D. Love, “Asymmetric multimode Y-junction splitters,” Opt. Quantum Electron. 29(3), 379–392 (1997). [CrossRef]

11.

N. Goto and G. L. Yip, “A TE-TM mode splitter in LINBO3 by proton-exchange and TI diffusion,” J. Lightwave Technol. 7(10), 1567–1574 (1989). [CrossRef]

12.

J. M. Castro, D. F. Geraghty, B. R. West, and S. Honkanen, “Fabrication and comprehensive modeling of ion-exchanged Bragg optical add-drop multiplexers,” Appl. Opt. 43(33), 6166–6173 (2004). [CrossRef] [PubMed]

13.

J. M. Castro, D. F. Geraghty, S. Honkanen, C. M. Greiner, D. Iazikov, and T. W. Mossberg, “Optical add-drop multiplexers based on the antisymmetric waveguide Bragg grating,” Appl. Opt. 45(6), 1236–1243 (2006). [CrossRef] [PubMed]

14.

D. F. Geraghty, D. Provenzano, M. Morrell, S. Honkanen, A. Yariv, and N. Peyghambarian, “Ion-exchanged waveguide add/drop filter,” Electron. Lett. 37(13), 829–831 (2001). [CrossRef]

15.

J. D. Love and A. Ankiewicz, “Purely geometrical coarse wave-length multiplexer/demultiplexer,” Electron. Lett. 39(19), 1385–1386 (2003). [CrossRef]

16.

W. K. Burns and F. Milton, “Mode conversion in planar-dielectric separating waveguides,” IEEE J. Quantum Electron. 11(1), 32–39 (1975). [CrossRef]

17.

N. Riesen and J. D. Love, “Design of mode-sorting asymmetric Y-junctions,” Appl. Opt. 51(15), 2778–2783 (2012). [CrossRef] [PubMed]

18.

J. D. Love, R. W. C. Vance, and A. Joblin, “Asymmetric, adiabatic multipronged planar splitters,” Opt. Quantum Electron. 28(4), 353–369 (1996). [CrossRef]

OCIS Codes
(060.4230) Fiber optics and optical communications : Multiplexing
(130.0130) Integrated optics : Integrated optics
(230.7370) Optical devices : Waveguides

ToC Category:
Integrated Optics

History
Original Manuscript: September 3, 2013
Revised Manuscript: September 22, 2013
Manuscript Accepted: September 23, 2013
Published: October 14, 2013

Citation
Weiwei Chen, Pengjun Wang, and Jianyi Yang, "Mode multi/demultiplexer based on cascaded asymmetric Y-junctions," Opt. Express 21, 25113-25119 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-21-25113


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References

  1. H. R. Stuart, “Dispersive multiplexing in multimode optical fiber,” Science 289(5477), 281–283 (2000). [CrossRef] [PubMed]
  2. S. Berdagué, P. Facq, “Mode division multiplexing in optical fibers,” Appl. Opt. 21(11), 1950–1955 (1982). [CrossRef] [PubMed]
  3. J. D. Love, N. Riesen, “Single-, Few-, and Multimode Y-Junctions,” J. Lightwave Technol. 30(3), 304–309 (2012). [CrossRef]
  4. J. B. Driscoll, R. R. Grote, B. Souhan, J. I. Dadap, M. Lu, R. M. Osgood., “Asymmetric Y junctions in silicon waveguides for on-chip mode-division multiplexing,” Opt. Lett. 38(11), 1854–1856 (2013). [CrossRef] [PubMed]
  5. T. Uematsu, Y. Ishizaka, Y. Kawaguchi, K. Saitoh, M. Koshiba, “Design of a Compact Two-Mode Multi/Demultiplexer Consisting of Multimode Interference Waveguides and a Wavelength-Insensitive Phase Shifter for Mode-Division Multiplexing Transmission,” J. Lightwave Technol. 30(15), 2421–2426 (2012). [CrossRef]
  6. D. Dai, “Silicon mode-(de)multiplexer for a hybrid multiplexing system to achieve ultrahigh capacity photonic networks-on-chip with a single-wavelength-carrier light,” Asia Communications and Photonics Conference (2012). [CrossRef]
  7. H. Y. Qiu, H. Yu, T. Hu, G. M. Jiang, H. F. Shao, P. Yu, J. Y. Yang, X. Q. Jiang, “Silicon mode multi/demultiplexer based on multimode grating-assisted couplers,” Opt. Express 21(15), 17904–17911 (2013). [CrossRef] [PubMed]
  8. M. Izutsu, Y. Nakai, T. Sueta, “Operation mechanism of the single-mode optical-waveguide Y junction,” Opt. Lett. 7(3), 136–138 (1982). [CrossRef] [PubMed]
  9. J. Vandertol, J. H. Laarhuis, “A polarization splitter on LINBO3 using only titanium diffusion,” J. Lightwave Technol. 9(7), 879–886 (1991). [CrossRef]
  10. W. M. Henry, J. D. Love, “Asymmetric multimode Y-junction splitters,” Opt. Quantum Electron. 29(3), 379–392 (1997). [CrossRef]
  11. N. Goto, G. L. Yip, “A TE-TM mode splitter in LINBO3 by proton-exchange and TI diffusion,” J. Lightwave Technol. 7(10), 1567–1574 (1989). [CrossRef]
  12. J. M. Castro, D. F. Geraghty, B. R. West, S. Honkanen, “Fabrication and comprehensive modeling of ion-exchanged Bragg optical add-drop multiplexers,” Appl. Opt. 43(33), 6166–6173 (2004). [CrossRef] [PubMed]
  13. J. M. Castro, D. F. Geraghty, S. Honkanen, C. M. Greiner, D. Iazikov, T. W. Mossberg, “Optical add-drop multiplexers based on the antisymmetric waveguide Bragg grating,” Appl. Opt. 45(6), 1236–1243 (2006). [CrossRef] [PubMed]
  14. D. F. Geraghty, D. Provenzano, M. Morrell, S. Honkanen, A. Yariv, N. Peyghambarian, “Ion-exchanged waveguide add/drop filter,” Electron. Lett. 37(13), 829–831 (2001). [CrossRef]
  15. J. D. Love, A. Ankiewicz, “Purely geometrical coarse wave-length multiplexer/demultiplexer,” Electron. Lett. 39(19), 1385–1386 (2003). [CrossRef]
  16. W. K. Burns, F. Milton, “Mode conversion in planar-dielectric separating waveguides,” IEEE J. Quantum Electron. 11(1), 32–39 (1975). [CrossRef]
  17. N. Riesen, J. D. Love, “Design of mode-sorting asymmetric Y-junctions,” Appl. Opt. 51(15), 2778–2783 (2012). [CrossRef] [PubMed]
  18. J. D. Love, R. W. C. Vance, A. Joblin, “Asymmetric, adiabatic multipronged planar splitters,” Opt. Quantum Electron. 28(4), 353–369 (1996). [CrossRef]

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