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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 4 — Feb. 14, 2011
  • pp: 3332–3338
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Multi-channel 100-Gbit/s DQPSK data exchange using bidirectional degenerate four-wave mixing

Jian Wang, Hao Huang, Xue Wang, Jeng-Yuan Yang, and Alan E. Willner  »View Author Affiliations


Optics Express, Vol. 19, Issue 4, pp. 3332-3338 (2011)
http://dx.doi.org/10.1364/OE.19.003332


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Abstract

We propose a simple approach to performing simultaneous multi-channel data exchange using bidirectional degenerate four-wave mixing (FWM) in a single highly nonlinear fiber (HNLF) assisted by optical filtering. Data exchange between two-channel 100-Gbit/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) signals with a variable channel spacing is implemented with a power penalty of less than 4.2 dB at a bit-error rate (BER) of 10−9. Moreover, simultaneous ITU-grid-compatible four-channel 100-Gbit/s RZ-DQPSK data exchange is demonstrated with a power penalty of less than 4.7 dB at a BER of 10−9.

© 2011 OSA

1. Introduction

The rapid growth in network capacity and traffic rates raises the significance of data traffic grooming exchange, which is considered to be a promising technique for enhancing the efficiency and flexibility of networks [1

1. H. S. Hamza and J. S. Deogun, “Wavelength-exchanging cross connects (WEX) - A new class of photonic cross-connect architectures,” J. Lightwave Technol. 24(3), 1101–1111 (2006). [CrossRef]

]. In a wavelength-division-multiplexed (WDM) network, data exchange, which is also known as wavelength interchange or wavelength exchange, would require the swapping of data from one wavelength with the data from another wavelength. Typically, a WDM network has many data channels on different wavelengths. In this scenario, it would be advantageous and desirable to achieve simultaneous multi-channel data exchange.

In this paper, we propose a simple alternative approach to performing data exchange between multi-channel DQPSK signals using bidirectional degenerate FWM in a single HNLF accompanied by optical filtering [10

10. J. Wang, H. Huang, X. Wang, J.-Y. Yang, and A. E. Willner, “Optical phase-transparent data grooming exchange of multi-channel 100-Gbit/s RZ-DQPSK signals,” Proc. IEEE 23rd Photonics Society Annual Meeting 2010, Denver, Colorado, USA, paper WN2, 2010.

]. Single pump is employed and four-channel signals are symmetric with respect to the pump. Simultaneous four-channel 100-Gbit/s return-to-zero DQPSK (RZ-DQPSK) data exchange is demonstrated with a power penalty of less than 4.7 dB at a bit-error-rate (BER) of 10−9.

2. Concept and principle

Figure 1
Fig. 1 Concept and principle of simultaneous multi-channel DQPSK data exchange.
illustrates the concept and principle of multi-channel data exchange. Degenerate FWM with a single continuous-wave (CW) pump is utilized. Four-channel DQPSK signals (S1-S4) are symmetric with respect to the CW pump. Simultaneous data exchange between S1 and S4 as well as S2 and S3 is expected. In general, such exchange function is not applicable with the unidirectional degenerate FWM in a single HNLF since the newly converted signals cannot be separated from the original signals. A potential solution is to explore the bidirectional degenerate FWM in a single HNLF assisted by optical filtering. As shown in Fig. 1, for the input four-channel signals (S1-S4), the filtered S1, S2 and CW pump are sent to HNLF from the left side, yielding S4 and S3 via degenerate FWM. The newly generated S4 and S3 are selected at the right side of HNLF while the original S1, S2 and CW pump are blocked. Meanwhile, the filtered S3, S4 and CW pump are fed into HNLF from the right side, producing S2 and S1 by degenerate FWM. The newly converted S2 and S1 are selected at the left side of HNLF while the original S3, S4 and CW pump are removed. As a consequence, simultaneous four-channel data exchange (S1&S4, S2&S3) can be achieved using bidirectional FWM in a single HNLF assisted by optical filtering. The combined S1-S4 from both sides of HNLF are the output four-channel signals after data exchange. Note that the in-phase (Ch. I) and quadrature (Ch. Q) components of DQPSK signals are swapped after data exchange due to the phase-conjugation characteristic of degenerate FWM.

3. Experimental setup

Figure 2
Fig. 2 Experimental setup for multi-channel DQPSK data exchange. HNLF: highly nonlinear fiber; BPF: band-pass filter; PC: polarization controller; EDFA: erbium-doped fiber amplifier; ISO: isolator; OC: optical coupler; TDL: tunable delay line; MZM: Mach-Zehnder modulator; WSS: wavelength-selective switch; VOL: variable optical attenuator; DLI: delay line interferometer; Tx: transmitter; Rx: receiver.
depicts the experimental setup for multi-channel data exchange. Four-channel 100-Gbit/s 27-1 pseudo-random binary sequence (PRBS) RZ-DQPSK signals (S1-S4) are obtained by sending four tunable CW lasers to a 100-Gbit/s (50-Gsymbol/s) DQPSK transmitter (Tx) followed by a RZ pulse carver. The 100-Gbit/s DQPSK transmitter (SHF 46214A) is a thermally stable Lithium Niobate Mach-Zehnder modulator (MZM) with a nested Mach-Zehnder interferometer (MZI) structure. Four-channel RZ-DQPSK signals are then separated, relatively delayed by integral symbols, recombined, and sent to a fiber loop mirror incorporating a 460-m piece of HNLF, two band-pass filters (BPF1, BPF2), and optical couplers (OCs). The HNLF has a nonlinear coefficient of 20 W−1·km−1, a zero-dispersion wavelength (ZDW) of ~1556 nm, and a dispersion slope of ~0.026 ps/nm2/km. A CW pump is coupled into the fiber loop mirror from both sides of the HNLF to enable bidirectional degenerate FWM in a single HNLF. Four-channel signals are arranged symmetrically relative to the CW pump. Note that BPF1 (BPF2) passes S1 and S2 (S3 and S4) while blocks S3, S4 and pump (S1, S2 and pump), resulting in simultaneous multi-channel data exchange between S1 and S4 as well as S2 and S3 via bidirectional degenerate FWM. At the output of the fiber loop mirror, the collected four-channel signals after data exchange are sent to a pre-amplified receiver (Rx) for BER measurements. A 50-GHz delay line interferometer (DLI) is used to demodulate the in-phase and quadrature components of 100-Gbit/s DQPSK signals.

4. Experimental results and discussions

Compared to the non-degenerate FWM-based data exchange with two pumps [8

8. J. Wang, S. R. Nuccio, H. Huang, X. Wang, J.-Y. Yang, and A. E. Willner, “Optical data exchange of 100-Gbit/s DQPSK signals,” Opt. Express 18(23), 23740–23745 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-23-23740. [CrossRef] [PubMed]

], single pump with its wavelength (1554.94 nm) close to the ZDW of HNLF, is employed in the bidirectional degenerate FWM-based data exchange. The pump power fed into HNLF from left (clockwise) and right (counter-clockwise) sides is about 14.4 and 15.4 dBm, respectively.

We first demonstrate two-channel (SA, SB) data exchange. BPF1 and BPF2 as illustrated in Fig. 2 pass only SA and SB, respectively. Shown in Fig. 3
Fig. 3 Spectra for two-channel DQPSK data exchange with variable channel spacing of (a1)(b1) 9.67 nm (SA: 1550.12 nm, SB: 1559.79 nm), (a2)(b2) 4.84 nm (SA: 1552.52 nm, SB: 1557.36 nm), (a3)(b3) 14.51 nm (SA: 1547.72 nm, SB: 1562.23 nm). (a1)(a2)(a3) Input two-channel 100-Gbit/s RZ-DQPSK signals (point A in Fig. 2). (b1)(b2)(b3) Spectra measured at point B in Fig. 2 in the absence (dashed curve: Rayleigh scattering) / presence (solid curve: after data exchange) of CW pump.
(a1) is the spectrum of ITU-grid-compatible input two-channel 100-Gbit/s RZ-DQPSK signals (SA: 1550.12 nm, SB: 1559.79 nm) with a channel spacing of 9.67 nm, measured at point A in Fig. 2. The power of SA and SB coupled into HNLF from left and right sides is about 9 dBm. Figure 3(b1) shows the spectrum after two-channel data exchange in the presence of CW pump (solid curve), measured at point B in Fig. 2. Note that some residual signals are also observed in the absence of CW pump (dashed curve), which we believe mainly come from the Rayleigh scattering inside the HNLF [11

11. T. Tsuzaki, T. Miyamoto, T. Okuno, M. Kakui, M. Hirano, M. Onishi, and M. Shigematsu, “Impact of double Rayleigh backscattering in discrete fiber Raman amplifiers employing highly nonlinear fiber,” Proc. OSA/OAA 2002, Vancouver, Canada, paper OWA2, 2002.

]. The extinction ratio (ER) of the newly exchanged signal to the residual signal of SA and SB is measured to be 18.1 dB. Furthermore, data exchange between two variable channels is also applicable as long as SA and SB are arranged to be symmetric with respect to the CW pump. Figure 3(a2)(b2) and (a3)(b3) show two more examples of data exchange with variable channel spacing of 4.84 nm (SA: 1552.52 nm, SB: 1557.36 nm) and 14.51 nm (SA: 1547.72 nm, SB: 1562.23 nm). The extinction ratio of exchanged signals (SA, SB) is measured to be 17.9 and 17.9 dB in Fig. 3(b2) and 17.2 and 18.1 dB in Fig. 3(b3).

To further verify the 100-Gbit/s DQPSK data exchange, we observe temporal waveforms and balanced eyes of demodulated in-phase (Ch. I) and quadrature (Ch. Q) components of 100-Gbit/s RZ-DQPSK signals corresponding to Fig. 3(a1)(b1). As shown in Fig. 4
Fig. 4 Waveforms and balanced eyes of demodulated in-phase (Ch. I) and quadrature (Ch. Q) components for two-channel 100-Gbit/s DQPSK data exchange corresponding to Fig. 3(a1)(b1).
, it can be clearly seen that the data information carried by two-channel 100-Gbit/s RZ-DQPSK signals is mutually converted after the bidirectional degenerate FWM, resulting in the successful implementation of 100-Gbit/s DQPSK data exchange. In addition, the in-phase and quadrature components of DQPSK signals are swapped after data exchange, which we believe is due to the phase-conjugation characteristic of degenerate FWM.

Figure 5
Fig. 5 BER curves for two-channel 100-Gbit/s DQPSK data exchange. (a1)(b1), (a2)(b2), (a3)(b3) correspond to Fig. 3(b1), (b2) and (b3), respectively.
depicts BER curves for two-channel 100-Gbit/s RZ-DQPSK data exchange with variable channel spacing, which correspond to Fig. 3(b1), (b2) and (b3), respectively. Less than 4.2-dB power penalty at a BER of 10−9 is observed, which could be ascribed to the beating effect between the newly converted signal and the original residual signal.

We further demonstrate simultaneous multi-channel data exchange. ITU-grid-compatible four-channel 100-Gbit/s RZ-DQPSK signals (S1: 1546.12 nm, S2: 1547.72 nm, S3: 1562.23 nm, S4: 1563.86 nm) are employed for multi-channel data exchange. S1 and S2 pass through BPF1 while S3 and S4 go through BPF2 as shown in Fig. 2. Figure 6(a)
Fig. 6 Spectra for four-channel DQPSK data exchange. (a) Input four-channel 100-Gbit/s RZ-DQPSK signals (point A in Fig. 2). (b) Spectra measured at point B in Fig. 2 in the absence (dashed curve: Rayleigh scattering)/presence (solid curve: after data exchange) of CW pump.
depicts the spectrum of input four-channel 100-Gbit/s RZ-DQPSK signals (measured at point A in Fig. 2). S1(S2) and S4(S3) are symmetric with respect to the CW pump. The power of S1-S4 launched into the HNLF from left (S1, S2) and right (S3, S4) sides is about 9.9, 8.4, 8.3, and 10.0 dBm, respectively. Figure 6(b) shows the spectrum after four-channel data exchange (measured at point B in Fig. 2) in the presence of CW pump (solid curve). The spectrum of residual signals (i.e., resulting from Rayleigh scattering in HNLF) in the absence of CW pump (dashed curve) is also depicted in Fig. 6(b). The extinction ratio of the newly exchanged signals to the residual signals of S1-S4 is measured to be 18.4, 19.5, 17 and 17 dB, respectively.

Figure 7
Fig. 7 Waveforms and balanced eyes of demodulated in-phase (Ch. I) and quadrature (Ch. Q) components for four-channel 100-Gbit/s DQPSK data exchange.
further displays temporal waveforms and balanced eyes of demodulated in-phase (Ch. I) and quadrature (Ch. Q) components of 100-Gbit/s RZ-DQPSK signals before and after data exchange. It is verified that four-channel 100-Gbit/s RZ-DQPSK data exchange (S1&S4, S2&S3) is successfully implemented. Also, it is noted that Ch. I and Ch. Q of DQPSK signals are swapped after data exchange as a result of the phase-conjugated degenerate FWM.

Figure 8
Fig. 8 BER curves for simultaneous four-channel 100-Gbit/s DQPSK data exchange.
plots the BER curves for four-channel 100-Gbit/s RZ-DQPSK data exchange. Less than 4.7-dB power penalty is observed at a BER of 10−9, which could be caused by the beating effect between the newly exchanged signals and the original residual signals.

5. Conclusion

Acknowledgments

We acknowledge the generous support of the DARPA under the contract number FA8650-08-1-7820 and the NSF-funded Center for the Integrated Access Networks (CIAN).

References and links

1.

H. S. Hamza and J. S. Deogun, “Wavelength-exchanging cross connects (WEX) - A new class of photonic cross-connect architectures,” J. Lightwave Technol. 24(3), 1101–1111 (2006). [CrossRef]

2.

K. Mori, H. Takara, and M. Saruwatari, “Wavelength interchange with an optical parametric loop mirror,” Electron. Lett. 33(6), 520–522 (1997). [CrossRef]

3.

Y. Gao, Y. H. Dai, C. Shu, and S. L. He, “Wavelength interchange of phase-shift-keying signal,” IEEE Photon. Technol. Lett. 22(11), 838–840 (2010). [CrossRef]

4.

K. Uesaka, K. K.-Y. Wong, M. E. Marhic, and L. G. Kazovsky, “Wavelength exchange in a highly nonlinear dispersion-shifted fiber: Theory and experiments,” IEEE J. Sel. Top. Quantum Electron. 8(3), 560–568 (2002). [CrossRef]

5.

R. W. L. Fung, H. K. Y. Cheung, and K. K. Y. Wong, “Widely tunable wavelength exchange in anomalous-dispersion regime,” IEEE Photon. Technol. Lett. 19(22), 1846–1848 (2007). [CrossRef]

6.

M. Z. Shen, X. Xu, T. I. Yuk, and K. K. Y. Wong, “Byte-level parametric wavelength exchange for narrow pulsewidth return-to-zero signal,” IEEE Photon. Technol. Lett. 21(21), 1591–1593 (2009). [CrossRef]

7.

J. Wang, Z. Bakhtiari, S. R. Nuccio, O. F. Yilmaz, X. Wu, and A. E. Willner, “Phase-transparent optical data exchange of 40 Gbit/s differential phase-shift keying signals,” Opt. Lett. 35(17), 2979–2981 (2010). [CrossRef] [PubMed]

8.

J. Wang, S. R. Nuccio, H. Huang, X. Wang, J.-Y. Yang, and A. E. Willner, “Optical data exchange of 100-Gbit/s DQPSK signals,” Opt. Express 18(23), 23740–23745 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-23-23740. [CrossRef] [PubMed]

9.

J. Wang, S. R. Nuccio, X. Wu, O. F. Yilmaz, L. Zhang, I. Fazal, J.-Y. Yang, Y. Yue, and A. E. Willner, “40 Gbit/s optical data exchange between wavelength-division-multiplexed channels using a periodically poled lithium niobate waveguide,” Opt. Lett. 35(7), 1067–1069 (2010). [CrossRef] [PubMed]

10.

J. Wang, H. Huang, X. Wang, J.-Y. Yang, and A. E. Willner, “Optical phase-transparent data grooming exchange of multi-channel 100-Gbit/s RZ-DQPSK signals,” Proc. IEEE 23rd Photonics Society Annual Meeting 2010, Denver, Colorado, USA, paper WN2, 2010.

11.

T. Tsuzaki, T. Miyamoto, T. Okuno, M. Kakui, M. Hirano, M. Onishi, and M. Shigematsu, “Impact of double Rayleigh backscattering in discrete fiber Raman amplifiers employing highly nonlinear fiber,” Proc. OSA/OAA 2002, Vancouver, Canada, paper OWA2, 2002.

OCIS Codes
(060.2330) Fiber optics and optical communications : Fiber optics communications
(190.4370) Nonlinear optics : Nonlinear optics, fibers
(190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
(230.1150) Optical devices : All-optical devices

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: November 22, 2010
Revised Manuscript: January 17, 2011
Manuscript Accepted: January 18, 2011
Published: February 4, 2011

Citation
Jian Wang, Hao Huang, Xue Wang, Jeng-Yuan Yang, and Alan E. Willner, "Multi-channel 100-Gbit/s DQPSK data exchange using bidirectional degenerate four-wave mixing," Opt. Express 19, 3332-3338 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-4-3332


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References

  1. H. S. Hamza and J. S. Deogun, “Wavelength-exchanging cross connects (WEX) - A new class of photonic cross-connect architectures,” J. Lightwave Technol. 24(3), 1101–1111 (2006). [CrossRef]
  2. K. Mori, H. Takara, and M. Saruwatari, “Wavelength interchange with an optical parametric loop mirror,” Electron. Lett. 33(6), 520–522 (1997). [CrossRef]
  3. Y. Gao, Y. H. Dai, C. Shu, and S. L. He, “Wavelength interchange of phase-shift-keying signal,” IEEE Photon. Technol. Lett. 22(11), 838–840 (2010). [CrossRef]
  4. K. Uesaka, K. K.-Y. Wong, M. E. Marhic, and L. G. Kazovsky, “Wavelength exchange in a highly nonlinear dispersion-shifted fiber: Theory and experiments,” IEEE J. Sel. Top. Quantum Electron. 8(3), 560–568 (2002). [CrossRef]
  5. R. W. L. Fung, H. K. Y. Cheung, and K. K. Y. Wong, “Widely tunable wavelength exchange in anomalous-dispersion regime,” IEEE Photon. Technol. Lett. 19(22), 1846–1848 (2007). [CrossRef]
  6. M. Z. Shen, X. Xu, T. I. Yuk, and K. K. Y. Wong, “Byte-level parametric wavelength exchange for narrow pulsewidth return-to-zero signal,” IEEE Photon. Technol. Lett. 21(21), 1591–1593 (2009). [CrossRef]
  7. J. Wang, Z. Bakhtiari, S. R. Nuccio, O. F. Yilmaz, X. Wu, and A. E. Willner, “Phase-transparent optical data exchange of 40 Gbit/s differential phase-shift keying signals,” Opt. Lett. 35(17), 2979–2981 (2010). [CrossRef] [PubMed]
  8. J. Wang, S. R. Nuccio, H. Huang, X. Wang, J.-Y. Yang, and A. E. Willner, “Optical data exchange of 100-Gbit/s DQPSK signals,” Opt. Express 18(23), 23740–23745 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-23-23740 . [CrossRef] [PubMed]
  9. J. Wang, S. R. Nuccio, X. Wu, O. F. Yilmaz, L. Zhang, I. Fazal, J.-Y. Yang, Y. Yue, and A. E. Willner, “40 Gbit/s optical data exchange between wavelength-division-multiplexed channels using a periodically poled lithium niobate waveguide,” Opt. Lett. 35(7), 1067–1069 (2010). [CrossRef] [PubMed]
  10. J. Wang, H. Huang, X. Wang, J.-Y. Yang, and A. E. Willner, “Optical phase-transparent data grooming exchange of multi-channel 100-Gbit/s RZ-DQPSK signals,” Proc. IEEE 23rd Photonics Society Annual Meeting 2010, Denver, Colorado, USA, paper WN2, 2010.
  11. T. Tsuzaki, T. Miyamoto, T. Okuno, M. Kakui, M. Hirano, M. Onishi, and M. Shigematsu, “Impact of double Rayleigh backscattering in discrete fiber Raman amplifiers employing highly nonlinear fiber,” Proc. OSA/OAA 2002, Vancouver, Canada, paper OWA2, 2002.

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