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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 22 — Nov. 4, 2013
  • pp: 25727–25733
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Silicon based polarization insensitive filter for WDM-PDM signal processing

Yaguang Qin, Yu Yu, Jinghui Zou, Mengyuan Ye, Lei Xiang, and Xinliang Zhang  »View Author Affiliations


Optics Express, Vol. 21, Issue 22, pp. 25727-25733 (2013)
http://dx.doi.org/10.1364/OE.21.025727


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Abstract

We propose and fabricate a novel circuit that combines two two-dimensional (2D) grating couplers and a microring resonator (MRR). According to the polarization states, one 2D grating coupler first splits the input signals into two orthogonal paths, which co-propagate in the loop and share a common MRR, and then the two paths are combined together by the other 2D grating coupler. The proposed circuit is polarization insensitive and can be used as a polarization insensitive filter. For demonstration, the wavelength division and polarization division multiplexing (WDM-PDM) non return-to-zero differential-phase-shift-keying (NRZ-DPSK) signals can be demodulated successfully. The bit error ratio measurements show an error free operation, reflecting the good performance and the practicability.

© 2013 Optical Society of America

1. Introduction

2. Principle and device description

The principle of the proposed scheme is illustrated in Fig. 1
Fig. 1 Principle of the proposed circuit
. The PDM signals with two orthogonal polarizations (X- and Y-pol) are vertically coupled into the 2D grating coupler. By optimizing the input polarization states, the two orthogonal polarizations are coupled into the corresponding two orthogonal waveguides, both in TE mode. The two TE modes, which carry the information from X- and Y-pol, propagate in different paths in the circuit. A MRR is inserted to process the signals clockwise and counter clockwise independently. Since the two signals are both in TE modes and two polarizations share different port of the MRR, the MRR can process the PDM signals identically and simultaneously.

The layout of the circuit is shown in Fig. 4(a)
Fig. 4 The SEM top view of (a) the layout of the fabricated circuit, (b) the 2D grating coupler, (c) the zoom in image of the holes, (d) the MRR and (e) the coupling region of the MRR
. It was fabricated by the electron beam lithography (EBL) and inductively coupled plasma (ICP) etching. A SOI wafer with top silicon layer of 220 nm and SiO2 layer of 3 µm was used. The Figs. 4(b)-4(e) show the scanning electron micrograph (SEM) top view of the 2D grating coupler and the MRR. The grating coupler is a square array of round holes with an etch depth of 90 nm. The diameter of the holes are 270 nm and the lattice period is 580 nm. For the other parts, the top silicon layer has been etched until the oxide layer. As to the MRR, the free spectral range (FSR) is designed to be 100 GHz, so that the radius can be calculated as 100 µm. The gap between the straight and bended waveguides for the coupling region is 250 nm. In order to reduce the footprint of the circuit, four S-bends are designed to connect 2D grating coupler and MRR. For a better fiber coupling efficiency, the 2D grating coupler were designed to be with a large area (12µm by 12µm holes array), resulting in the large width of the waveguide connected to the 2D grating coupler. In contrast, the width of the SOI waveguide is about 450 nm to ensure a single TE mode condition. As a result, the waveguide should be tapered from 12 µm to 450 nm, and a relatively long waveguide is induced. On the other hand, the radius of the MRR is 100 µm, and cannot match the distance between the two output waveguides from the 2D grating coupler. Hence, the waveguide should be bent over to the MRR. Considering the path uniformity of the clockwise and counter clockwise signals and the bending loss, the four S-bends with such a shape were designed and utilized in our design. A broadband light source is applied to measure the transmission spectrum of the proposed filter. The transmission spectrum remains almost the same with three different input polarization states, which coincides with the results of simulation, as shown in Fig. 5
Fig. 5 Measured transmission spectra of the MRR
. Furthermore, multiple channels operation can be possible by properly choosing the input channel spacing, due to the periodic transmission characteristics of the MRR. To verify the performance of the fabricated circuit, the WDM-PDM NRZ-DPSK demodulation at a total rate of 100 Gb/s based on the available experimental facility is demonstrated in the following session.

3. Experimental setup and results

In order to evaluate the performance of the proposed circuit, the BER measurements are performed for the four demodulated signals respectively, by performing the polarization and wavelength demultiplexing. Results are plotted in Fig. 8(b). The error free operation can be obtained for all the signals.

4. Conclusion

In conclusion, we have proposed and fabricated a polarization insensitive circuit that can be used for all optical WDM-PDM signals processing. For demonstration, the WDM-PDM NRZ-DPSK signals demodulation had been successfully achieved with error free. Arising from this idea, many other polarization insensitive devices for various PDM signal processing functions can be achieved by replacing the MRR with other signal processors, and we believe that these devices can be advantageous in monolithic integrated circuit and the characteristics are sufficient for PDM signal processing in the future optical transport networks.

Acknowledgments

This work was supported by the National Basic Research Program of China (Grant No. 2011CB301704), National Natural Science Foundation of China (Grant No. 61007042, 61275072 and 61125501), and the Fundamental Research Funds for the Central Universities (Grant No. HUST2012QN104). The authors thank the Center of Micro-Fabrication and Characterization (CMFC) of WNLO for device fabrication.

References and links

1.

P. J. Winzer, “High-spectral-efficiency optical modulation formats,” J. Lightwave Technol. 30(24), 3824–3835 (2012). [CrossRef]

2.

A. Chraplyvy, “The coming capacity crunch,” in 35th European Conference on Optical Communication (ECOC 2009), pp. 20–24.

3.

C. R. Doerr and T. F. Taunay, “Silicon photonics core-, wavelength-, and polarization-diversity receiver,” IEEE Photon. Technol. Lett. 23(9), 597–599 (2011). [CrossRef]

4.

E. G. Stephen Jr, M. F. Linn, G. P. James, and B. S. Neal, “Polarization multiplexing with solitons,” J. Lightwave Technol. 10, 28–35 (1992).

5.

C. R. Doerr, L. Buhl, Y. Baeyens, R. Aroca, S. Chandrasekhar, X. Liu, L. Chen, and Y. K. Chen, “Packaged monolithic silicon 112-Gb/s coherent receiver,” IEEE Photon. Technol. Lett. 23(12), 762–764 (2011). [CrossRef]

6.

C. R. Doerr, L. Zhang, P. J. Winzer, N. Weimann, V. Houtsma, T.-C. Hu, N. J. Sauer, L. L. Buhl, D. T. Neilson, S. Chandrasekhar, and Y. K. Chen, “Monolithic InP dual-polarization and dual-quadrature coherent receiver,” IEEE Photon. Technol. Lett. 23(11), 694–696 (2011). [CrossRef]

7.

L. Xiang, Y. M. Xu, Y. Yu, and X. L. Zhang, “An ultracompact DP-QPSK demodulator based on multimode interference and photonic crystals,” J. Lightwave Technol. 30(11), 1595–1601 (2012). [CrossRef]

8.

S. Tsunashima, F. Nakajima, Y. Nasu, R. Kasahara, Y. Nakanishi, T. Saida, T. Yamada, K. Sano, T. Hashimoto, H. Fukuyama, H. Nosaka, and K. Murata, “Silica-based, compact and variable-optical-attenuator integrated coherent receiver with stable optoelectronic coupling system,” Opt. Express 20(24), 27174–27179 (2012). [CrossRef] [PubMed]

9.

W. H. Wu, Y. Yu, S. J. Hu, B. R. Zou, and X. L. Zhang, “All-optical format conversion for polarization and wavelength division multiplexed system,” IEEE Photon. Technol. Lett. 24(18), 1606–1609 (2012). [CrossRef]

10.

H. Y. Jiang, L. S. Yan, J. Ye, W. Pan, B. Luo, and X. S. Yao, “PDM RZ-to-NRZ and NRZ-to-PRZ format conversions using a variable DGD element inside a polarization-diversified loop,” Opt. Lett. 37(13), 2535–2537 (2012). [CrossRef] [PubMed]

11.

L. S. Yan, A. E. Willner, X. X. Wu, A. L. Yi, B. Antonella, Z. Y. Chen, and H. Y. Jiang, “All-optical signal processing for ultrahigh speed optical systems and networks,” J. Lightwave Technol. 30(24), 3760–3770 (2012). [CrossRef]

12.

H. Fukuda, K. Yamada, T. Tsuchizawa, T. Watanabe, H. Shinojima, and S. Itabashi, “Silicon photonic circuit with polarization diversity,” Opt. Express 16(7), 4872–4880 (2008). [CrossRef] [PubMed]

13.

D. X. Xu, S. Janz, and P. Cheben, “Design of polarization-insensitive ring resonators in silicon-on-insulator using MMI couplers and cladding stress engineering,” IEEE Photon. Technol. Lett. 18(2), 343–345 (2006). [CrossRef]

14.

Y. H. Ding, H. Y. Ou, and C. Peucheret, “Wideband polarization splitter and rotator with large fabrication tolerance and simple fabrication process,” Opt. Lett. 38(8), 1227–1229 (2013). [CrossRef] [PubMed]

15.

P. Dong, C. J. Xie, L. Chen, L. L. Buhl, and Y. K. Chen, “112-Gb/s monolithic PDM-QPSK modulator in silicon,” Opt. Express 20(26), B624–B629 (2012). [CrossRef] [PubMed]

16.

D. Po, X. Liu, C. Sethumadhavan, L. L. Buhl, R. Aroca, Y. Baeyens, and Y. K. Chen, “224-Gb/s PDM-16-QAM modulator and receiver based on silicon photonic integrated circuits,” in National Fiber Optic Engineers Conference, (Optical Society of America, 2013), paper PDP5C.

17.

T. Dirk, H. Chong, B. Peter, F. Lars, D. L. Rue, and B. Roel, “A compact two-dimensional grating coupler used as a polarization splitter,” IEEE Photon. Technol. Lett. 15(9), 1249–1251 (2003). [CrossRef]

18.

W. Bogaerts, D. Taillaert, P. Dumon, D. Van Thourhout, R. Baets, and E. Pluk, “A polarization-diversity wavelength duplexer circuit in silicon-on-insulator photonic wires,” Opt. Express 15(4), 1567–1578 (2007). [CrossRef] [PubMed]

19.

C. R. Doerr, L. Zhang, P. J. Winzer, N. Weimann, V. Houtsma, T. Hu, N. J. Sauer, L. L. Buhl, D. T. Neilson, and S. Chandrasekhar, “Monolithic polarization and phase diversity coherent receiver in silicon,” J. Lightwave Technol. 28(4), 520–525 (2010). [CrossRef]

20.

Y. H. Ding, C. Peucheret, M. H. Pu, B. Zsigri, J. Seoane, L. Liu, J. Xu, H. Y. Ou, X. L. Zhang, and D. X. Huang, “Multi-channel WDM RZ-to-NRZ format conversion at 50 Gbit/s based on single silicon microring resonator,” Opt. Express 18(20), 21121–21130 (2010). [CrossRef] [PubMed]

21.

F. Liu, T. Wang, Z. Zhang, M. Qiu, and Y. Su, “On-chip photonic generation of ultra-wideband monocycle pulses,” Electron. Lett. 45(24), 1247–1249 (2009). [CrossRef]

22.

Lumerical Solutions, Inc., http://www.lumerical.com/.

23.

A. Mekis, S. Gloeckner, G. Masini, A. Narasimha, T. Pinguet, S. Sahni, and P. De Dobbelaere, “A grating-coupler-enabled CMOS photonics platform,” IEEE J. Sel. Top. Quantum Electron. 17(3), 597–608 (2011). [CrossRef]

24.

Y. Yu, X. L. Zhang, and D. X. Huang, “All-optical clock recovery from NRZ-DPSK signal,” Photon. Technol. Lett. IEEE 18(22), 2356–2358 (2006). [CrossRef]

25.

L. Zhang, J. Y. Yang, M. P. Song, Y. C. Li, B. Zhang, R. G. Beausoleil, and A. E. Willner, “Microring-based modulation and demodulation of DPSK signal,” Opt. Express 15(18), 11564–11569 (2007). [CrossRef] [PubMed]

OCIS Codes
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
(070.4560) Fourier optics and signal processing : Data processing by optical means
(230.1150) Optical devices : All-optical devices

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: August 22, 2013
Revised Manuscript: October 10, 2013
Manuscript Accepted: October 10, 2013
Published: October 21, 2013

Citation
Yaguang Qin, Yu Yu, Jinghui Zou, Mengyuan Ye, Lei Xiang, and Xinliang Zhang, "Silicon based polarization insensitive filter for WDM-PDM signal processing," Opt. Express 21, 25727-25733 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-22-25727


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References

  1. P. J. Winzer, “High-spectral-efficiency optical modulation formats,” J. Lightwave Technol.30(24), 3824–3835 (2012). [CrossRef]
  2. A. Chraplyvy, “The coming capacity crunch,” in 35th European Conference on Optical Communication (ECOC 2009), pp. 20–24.
  3. C. R. Doerr and T. F. Taunay, “Silicon photonics core-, wavelength-, and polarization-diversity receiver,” IEEE Photon. Technol. Lett.23(9), 597–599 (2011). [CrossRef]
  4. E. G. Stephen, M. F. Linn, G. P. James, and B. S. Neal, “Polarization multiplexing with solitons,” J. Lightwave Technol.10, 28–35 (1992).
  5. C. R. Doerr, L. Buhl, Y. Baeyens, R. Aroca, S. Chandrasekhar, X. Liu, L. Chen, and Y. K. Chen, “Packaged monolithic silicon 112-Gb/s coherent receiver,” IEEE Photon. Technol. Lett.23(12), 762–764 (2011). [CrossRef]
  6. C. R. Doerr, L. Zhang, P. J. Winzer, N. Weimann, V. Houtsma, T.-C. Hu, N. J. Sauer, L. L. Buhl, D. T. Neilson, S. Chandrasekhar, and Y. K. Chen, “Monolithic InP dual-polarization and dual-quadrature coherent receiver,” IEEE Photon. Technol. Lett.23(11), 694–696 (2011). [CrossRef]
  7. L. Xiang, Y. M. Xu, Y. Yu, and X. L. Zhang, “An ultracompact DP-QPSK demodulator based on multimode interference and photonic crystals,” J. Lightwave Technol.30(11), 1595–1601 (2012). [CrossRef]
  8. S. Tsunashima, F. Nakajima, Y. Nasu, R. Kasahara, Y. Nakanishi, T. Saida, T. Yamada, K. Sano, T. Hashimoto, H. Fukuyama, H. Nosaka, and K. Murata, “Silica-based, compact and variable-optical-attenuator integrated coherent receiver with stable optoelectronic coupling system,” Opt. Express20(24), 27174–27179 (2012). [CrossRef] [PubMed]
  9. W. H. Wu, Y. Yu, S. J. Hu, B. R. Zou, and X. L. Zhang, “All-optical format conversion for polarization and wavelength division multiplexed system,” IEEE Photon. Technol. Lett.24(18), 1606–1609 (2012). [CrossRef]
  10. H. Y. Jiang, L. S. Yan, J. Ye, W. Pan, B. Luo, and X. S. Yao, “PDM RZ-to-NRZ and NRZ-to-PRZ format conversions using a variable DGD element inside a polarization-diversified loop,” Opt. Lett.37(13), 2535–2537 (2012). [CrossRef] [PubMed]
  11. L. S. Yan, A. E. Willner, X. X. Wu, A. L. Yi, B. Antonella, Z. Y. Chen, and H. Y. Jiang, “All-optical signal processing for ultrahigh speed optical systems and networks,” J. Lightwave Technol.30(24), 3760–3770 (2012). [CrossRef]
  12. H. Fukuda, K. Yamada, T. Tsuchizawa, T. Watanabe, H. Shinojima, and S. Itabashi, “Silicon photonic circuit with polarization diversity,” Opt. Express16(7), 4872–4880 (2008). [CrossRef] [PubMed]
  13. D. X. Xu, S. Janz, and P. Cheben, “Design of polarization-insensitive ring resonators in silicon-on-insulator using MMI couplers and cladding stress engineering,” IEEE Photon. Technol. Lett.18(2), 343–345 (2006). [CrossRef]
  14. Y. H. Ding, H. Y. Ou, and C. Peucheret, “Wideband polarization splitter and rotator with large fabrication tolerance and simple fabrication process,” Opt. Lett.38(8), 1227–1229 (2013). [CrossRef] [PubMed]
  15. P. Dong, C. J. Xie, L. Chen, L. L. Buhl, and Y. K. Chen, “112-Gb/s monolithic PDM-QPSK modulator in silicon,” Opt. Express20(26), B624–B629 (2012). [CrossRef] [PubMed]
  16. D. Po, X. Liu, C. Sethumadhavan, L. L. Buhl, R. Aroca, Y. Baeyens, and Y. K. Chen, “224-Gb/s PDM-16-QAM modulator and receiver based on silicon photonic integrated circuits,” in National Fiber Optic Engineers Conference, (Optical Society of America, 2013), paper PDP5C.
  17. T. Dirk, H. Chong, B. Peter, F. Lars, D. L. Rue, and B. Roel, “A compact two-dimensional grating coupler used as a polarization splitter,” IEEE Photon. Technol. Lett.15(9), 1249–1251 (2003). [CrossRef]
  18. W. Bogaerts, D. Taillaert, P. Dumon, D. Van Thourhout, R. Baets, and E. Pluk, “A polarization-diversity wavelength duplexer circuit in silicon-on-insulator photonic wires,” Opt. Express15(4), 1567–1578 (2007). [CrossRef] [PubMed]
  19. C. R. Doerr, L. Zhang, P. J. Winzer, N. Weimann, V. Houtsma, T. Hu, N. J. Sauer, L. L. Buhl, D. T. Neilson, and S. Chandrasekhar, “Monolithic polarization and phase diversity coherent receiver in silicon,” J. Lightwave Technol.28(4), 520–525 (2010). [CrossRef]
  20. Y. H. Ding, C. Peucheret, M. H. Pu, B. Zsigri, J. Seoane, L. Liu, J. Xu, H. Y. Ou, X. L. Zhang, and D. X. Huang, “Multi-channel WDM RZ-to-NRZ format conversion at 50 Gbit/s based on single silicon microring resonator,” Opt. Express18(20), 21121–21130 (2010). [CrossRef] [PubMed]
  21. F. Liu, T. Wang, Z. Zhang, M. Qiu, and Y. Su, “On-chip photonic generation of ultra-wideband monocycle pulses,” Electron. Lett.45(24), 1247–1249 (2009). [CrossRef]
  22. Lumerical Solutions, Inc., http://www.lumerical.com/ .
  23. A. Mekis, S. Gloeckner, G. Masini, A. Narasimha, T. Pinguet, S. Sahni, and P. De Dobbelaere, “A grating-coupler-enabled CMOS photonics platform,” IEEE J. Sel. Top. Quantum Electron.17(3), 597–608 (2011). [CrossRef]
  24. Y. Yu, X. L. Zhang, and D. X. Huang, “All-optical clock recovery from NRZ-DPSK signal,” Photon. Technol. Lett. IEEE18(22), 2356–2358 (2006). [CrossRef]
  25. L. Zhang, J. Y. Yang, M. P. Song, Y. C. Li, B. Zhang, R. G. Beausoleil, and A. E. Willner, “Microring-based modulation and demodulation of DPSK signal,” Opt. Express15(18), 11564–11569 (2007). [CrossRef] [PubMed]

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