## Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system |

Optics Express, Vol. 19, Issue 5, pp. 4501-4512 (2011)

http://dx.doi.org/10.1364/OE.19.004501

Acrobat PDF (1335 KB)

### Abstract

Arrayed waveguide gratings (AWG) are widely used as wavelength division multiplexers (MUX) and demultiplexers (DEMUX) in optical networks. Here we propose and demonstrate that conventional AWGs can also be used as integrated spectral filters to realize a Fast Fourier transform (FFT) and its inverse form (IFFT). More specifically, we point out that the wavelength selection conditions of AWGs when used as wavelength MUX/DEMUX also enable them to perform FFT/IFFT functions. Therefore, previous research on AWGs can now be applied to optical FFT/IFFT circuit design. Compared with other FFT/IFFT optical circuits, AWGs have less structural complexity, especially for a large number of inputs and outputs. As an important application, AWGs can be used in optical OFDM systems. We propose an all-optical OFDM system with AWGs and demonstrate the simulation results. Overall, the AWG provides a feasible solution for all-optical OFDM systems, especially with a large number of optical subcarriers.

© 2011 OSA

## 1. Introduction

3. A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express **14**(6), 2079–2084 (2006). [CrossRef] [PubMed]

4. W. Shieh, W. Chen, and R. S. Tucker, “Polarization mode dispersion mitigation in coherent optical orthogonal frequency division multiplexed systems,” Electron. Lett. **42**(17), 996–997 (2006). [CrossRef]

5. Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, D. Rangaraj, A. Cartolano, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing,” Opt. Express **17**(20), 17658–17668 (2009). [CrossRef] [PubMed]

9. D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Möller, M. Hübner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8Tb/s,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper PDPC1 (2010).

9. D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Möller, M. Hübner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8Tb/s,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper PDPC1 (2010).

13. S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express **17**(24), 21350–21361 (2009). [CrossRef] [PubMed]

9. D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Möller, M. Hübner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8Tb/s,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper PDPC1 (2010).

14. K. Lee, C. T. D. Thai, and J.-K. K. Rhee, “All optical discrete Fourier transform processor for 100 Gbps OFDM transmission,” Opt. Express **16**(6), 4023–4028 (2008). [CrossRef] [PubMed]

17. D. Hillerkuss, M. Winter, M. Teschke, A. Marculescu, J. Li, G. Sigurdsson, K. Worms, S. Ben Ezra, N. Narkiss, W. Freude, and J. Leuthold, “Simple all-optical FFT scheme enabling Tbit/s real-time signal processing,” Opt. Express **18**(9), 9324–9340 (2010). [CrossRef] [PubMed]

17. D. Hillerkuss, M. Winter, M. Teschke, A. Marculescu, J. Li, G. Sigurdsson, K. Worms, S. Ben Ezra, N. Narkiss, W. Freude, and J. Leuthold, “Simple all-optical FFT scheme enabling Tbit/s real-time signal processing,” Opt. Express **18**(9), 9324–9340 (2010). [CrossRef] [PubMed]

17. D. Hillerkuss, M. Winter, M. Teschke, A. Marculescu, J. Li, G. Sigurdsson, K. Worms, S. Ben Ezra, N. Narkiss, W. Freude, and J. Leuthold, “Simple all-optical FFT scheme enabling Tbit/s real-time signal processing,” Opt. Express **18**(9), 9324–9340 (2010). [CrossRef] [PubMed]

*N*becomes large. So far the implemented optical FFT circuits with

*N*up to 8 are reported [15,17

**18**(9), 9324–9340 (2010). [CrossRef] [PubMed]

18. A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express **18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

18. A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express **18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

*N*. Therefore our work provides a feasible way of implementing all-optical OFDM systems. The AWG as FFT/IFFT circuits is especially suitable for optical OFDM superchannel system consisting of a large number of optical subcarriers.

## 2. Operational principles of the AWG as FFT/IFFT filters and AWG parameter design

19. C. R. Doerr and K. Okamoto, “Advances in silica planar lightwave circuits,” J. Lightwave Technol. **24**(12), 4763–4789 (2006). [CrossRef]

20. M. K. Smit and C. Van Dam, “PHASAR-based WDM-devices: Principles, design and applications,” IEEE J. Sel. Top. Quantum Electron. **2**(2), 236–250 (1996). [CrossRef]

18. A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express **18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

**18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

*ΔL*between the channels. Usually the two slab regions are identical with the details shown in Fig. 2(b). Denote the AWG’s input/output waveguide separation as

*D*. Also denote the arrayed waveguide separation as

*d*(for input) and

*d*(for output), and the radius of the curvatures as

_{1}*f*(for input) and

*f*

_{1}(for output). Here

*d = d*and

_{1,}*f = f*

_{1}. Denote the number of waveguide channels as

*N*for the input/out waveguides and the arrayed waveguides.

*x*) is based on the constructive interference of the beams from the arrayed waveguides [19

19. C. R. Doerr and K. Okamoto, “Advances in silica planar lightwave circuits,” J. Lightwave Technol. **24**(12), 4763–4789 (2006). [CrossRef]

*m*is an integer, and

*n*and

_{s}*n*are the refractive index in the slab and arrayed waveguide region, respectively. Based on Eq. (1), a series of formulas are derived as following [19

_{c}19. C. R. Doerr and K. Okamoto, “Advances in silica planar lightwave circuits,” J. Lightwave Technol. **24**(12), 4763–4789 (2006). [CrossRef]

*λ*is the center wavelength,

_{0}*Δλ*is the channel spacing of the AWG transmission spectrum, and

*N*is the number of channels in a free spectral range (FSR).

_{ch}*N*represents the group index of the arrayed waveguide.

_{c}= n_{c}-λdn_{c}/dλ*Δλ*in frequency:

*τ is*the time difference of light traveling between adjacent channels in the arrayed waveguide. Also 1/

*τ*defines the FSR in frequency domain.

*i*th input and the

*k*th output as [21

21. G. Cincotti, N. Wada, and K. Kitayama, “Characterization of a full encoder/decoder in the AWG configuration for code-based photonic routers—part I: modeling and design,” J. Lightwave Technol. **24**(1), 103–112 (2006). [CrossRef]

*N*, and neglect the constant time delay terms, since they do not change the final transfer function form. A simplified formula of Eq. (4) can be obtained as:

_{ch}= N*N*means that the AWG transmission spectrum repeats after every

_{ch}= N*NΔλ*periods. In other words, the FSR of the AWG 1/

*τ*exactly matches the spacing between different frequency bands, each band containing

*N*channels. Such AWGs are called cyclic AWGs. Equation (6) is interpreted as follows: the

*N*arrayed waveguides provide temporal delays and the input/output slab regions produce phase shifts.

*j*in the arrayed waveguide to the output port

*k*), we have

**18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

*N*is critical and Eq. (2) and (3) are required.

_{ch}*i = N-1.*For an input signal

*s*(

_{i}*t*), take the observation period as

*Nτ*. The signal at the each output

*k*is

*t*= (

*N-1*)

*τ,*

*S*[(

_{k}*N-1*)

*τ*] is the FFT output of the signal series

*s*[(

_{i}’*N/2-n*)

*τ*],which is a cyclic shift of

*s*(

_{i}*mτ*) by

*N/2*within period

*Nτ,*in a reverse order. The extra term

*e*just provides an additional cyclic shift of the sequence

^{jπk/N}*s*[(

_{i}’*n + N/2*)

*τ*]. Both the cyclic shift and the extra phase term can be eliminated by a slight design modification in the AWG input/output waveguides and the proper selection of the phase reference.

*N*copies of

*s*(

_{i}*t*) overlap with different time delay. In other words, since we only observe

*s*(

_{i}*t*) at

*0≤ t<T*=

*Nτ*, there is only a time window with width

*τ*, during which the FFT is realized, as shown in Fig. 3(a) . Therefore a time gating device is usually required to sample the signal at that window.

*k = N-1*. For different inputs, the impulse response becomes

*S*(t) (

_{i}*i = 0,1,…N-1*) are present, and

*S*(t) is the time sample.

_{i}*0≤ t<T*=

*Nτ*. Then only

*S*(0) is significant, and the output signal is derived as:

_{i}*s*(

_{out}*t*) at

*t = mτ*(

*m = 0, 1,…, N-1*), we have

*s’*[(

_{out}*n + N/2*)

*τ*] is a cyclic shift of sequence

*s*by

_{out}(mτ)*N*/

*2*. Again, the term

*e*just adds an additional cyclic shift to

^{jπi/N}*s*(

_{out}*mτ*).

*τ*. Otherwise there will be interference from other symbols at some of the

*N*samples

*s*, because of the time delay in the arrayed waveguide. In practice, we can use

_{out}(mτ)*N*data sequences

*S*(

_{i}*m*) to individually modulate

*N*optical short-pulse sequences with repetition period

*T*=

*Nτ*. The IFFT result will be obtained at one AWG output at sampling points

*t = mτ*(

*m = 0, 1,…, N-1*).

*τ*= 1/160GHz = 6.25ps. The path increment

*ΔL*can be calculated accordingly from Eq. (3). Additionally, a 1 × N AWG is enough to realize the FFT/IFFT function, instead of an N × N AWG. Here We discuss N × N AWGs to provide configuration flexibility and also to enable it to be used in other applications [21

21. G. Cincotti, N. Wada, and K. Kitayama, “Characterization of a full encoder/decoder in the AWG configuration for code-based photonic routers—part I: modeling and design,” J. Lightwave Technol. **24**(1), 103–112 (2006). [CrossRef]

21. G. Cincotti, N. Wada, and K. Kitayama, “Characterization of a full encoder/decoder in the AWG configuration for code-based photonic routers—part I: modeling and design,” J. Lightwave Technol. **24**(1), 103–112 (2006). [CrossRef]

*τ*, and is orthogonal to all the other channels, because it vanishes at the peaks of all the other channels. For practical AWGs, the transmission spectral shape for each channel is usually a Gaussian function [19

**24**(12), 4763–4789 (2006). [CrossRef]

**24**(12), 4763–4789 (2006). [CrossRef]

20. M. K. Smit and C. Van Dam, “PHASAR-based WDM-devices: Principles, design and applications,” IEEE J. Sel. Top. Quantum Electron. **2**(2), 236–250 (1996). [CrossRef]

**24**(12), 4763–4789 (2006). [CrossRef]

**24**(12), 4763–4789 (2006). [CrossRef]

**18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

*N*increases. Ref. 17 simplifies the FFT circuit design and uses

*N*-1 cascaded delay interferometers to achieve a full functional N-point FFT/IFFT circuit. However, it stills consists of

*N*-1 interferometers and

*N*-1 phase stabilizers. By contrast, the AWG-based FFT/IFFT circuit here only requires the design of the arrayed waveguide and the two slab regions, for any size of N. Even for a transform order

*N*= 8, the fabrication of a AWG as an FFT/IFFT circuit can be easier than other approaches. Therefore our approach provides a feasible solution for an integrated optical FFT/IFFT circuit with a large N. For example, current AWGs having 128 and even 512 inputs/outputs have already been reported, with 10GHz channel spacing [22

22. K. Takada, M. Abe, and K. Okamoto, “Low-cross-talk polarization-insensitive 10-GHz-spaced 128-channel arrayed-waveguide grating multiplexer-demultiplexer achieved with photosensitive phase adjustment,” Opt. Lett. **26**(2), 64–65 (2001). [CrossRef]

23. K. Takada, M. Abe, M. Shibata, M. Ishii, and K. Okamoto, “Low-Crosstalk 10-GHz-spaced 512-channel arrayed-waveguide grating multi/demultiplexer fabricated on a 4-in wafer,” IEEE Photon. Technol. Lett. **13**(11), 1182–1184 (2001). [CrossRef]

## 3. All-optical OFDM systems with AWGs and simulation results

*N*= 4 and 16, respectively. As shown in Fig. 6, an open eye can be obtained for both

*N*= 4 and 16, which validates the operations of AWGs functioning as IFFT and FFT circuits, as discussed in Section 2. Therefore these AWGs can be utilized in the applications where optical FFT or IFFT process is needed. These applications are not restricted in optical OFDM systems but can be other areas, such as fast digital signal processing in which large order FFT/IFFT are required.

*t = mτ*(

*m = 0, 1,…, N-1*). As for the FFT operation, the FFT results are only valid during the interval

*T/N*. Figure 7 provides a better picture of explanation. After IFFT and FFT operations the transmitted data can only be retrieved at the right sampling point

*t*, as shown in Fig. 7. Therefore, this all-optical OFDM system works well only under rigorous experimental conditions and is sensitive to the signal distortions and AWG fabrication imperfections.

_{0}*T/N*, because only FFT operation is conducted in the system. The demultiplexed OFDM signal can be obtained after optical samplers.

*N*increases. If we assume that an ideal sampler is placed, with sampling window exactly matching

*T/N*, the sampled signal’s amplitude will decrease by 3dB when

*N*doubles. The signal-to-noise ratio (SNR) will also drop by 3dB, if the noise level keeps the same. In practical experiments, the sampler’s gate window does not necessarily match the sampling window width, and the imperfections of the FFT filter and the optical sampler will also degrade the SNR [15]. All of these practical factors will induce additional power penalty.

*N*= 16). Compared with Fig. 9 (b), the duration of the eye opening becomes much shorter, due to the limited modulator bandwidth. Figure 10(b) shows the demultiplexed eye diagram when the 16 modulated subcarriers are not symbol-aligned. The eye opening becomes much smaller compared to Fig. 9 (a), which indicates that the OFDM system requires symbol alignment for all subcarriers. The effects of symbol-alignment on optical OFDM system’s performance are discussed elaborately with more details in [13

13. S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express **17**(24), 21350–21361 (2009). [CrossRef] [PubMed]

24. G. Goldfarb, G. Li, and M. G. Taylor, “Orthogonal wavelength-division multiplexing using coherent detection,” IEEE Photon. Technol. Lett. **19**(24), 2015–2017 (2007). [CrossRef]

## 4. Conclusion

*N*. We propose two types of all-optical OFDM systems with AWGs. Our simulation results prove the AWG’s operation as both FFT and IFFT circuits.

## Acknowledgment

## References and links

1. | H. Sanjoh, E. Yamada, and Y. Yoshikuni, “Optical orthogonal frequency division multiplexing using frequency/time domain filtering for high spectral efficiency up to 1 bit/s/Hz,” in Conference on Optical Fiber Communication, OFC (Anaheim, CA, 2002), paper ThD1, 401–402 (2002). |

2. | W. Shieh and I. Djordjevic, |

3. | A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express |

4. | W. Shieh, W. Chen, and R. S. Tucker, “Polarization mode dispersion mitigation in coherent optical orthogonal frequency division multiplexed systems,” Electron. Lett. |

5. | Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, D. Rangaraj, A. Cartolano, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing,” Opt. Express |

6. | Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express |

7. | F. Buchali, R. Dischler, A. Klekamp, M. Bernhard, and Y. Ma, “Statistical Transmission Experiments Using a Real-Time 12.1 Gb/s OFDM Transmitter”, in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OMS3 (2010). |

8. | S. Chen, Y. Ma, and W. Shieh, 110-Gb/s Multi-Band Real-Time Coherent Optical OFDM Reception after 600-km Transmission over SSMF Fiber”, in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OMS2 (2010). |

9. | D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Möller, M. Hübner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8Tb/s,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper PDPC1 (2010). |

10. | H. Chen, M. Chen, and S. Xie, “All-optical sampling orthogonal frequency-division multiplexing scheme for high-speed transmission system,” J. Lightwave Technol. |

11. | F. C. Garcia Gunning, S. K. Ibrahim, P. Frascella, P. Gunning, and A. D. Ellis, “High symbol rate OFDM transmission technologies”,in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OThD1 (2010). |

12. | S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Peckham, “Transmission of a 1.2 Tb/s 24-carrier no-guad-interval coherent OFDM superchannel over 7200-km of Ultra-Large-Area Fiber,” in Proc. ECOC 2009 (Vienna, Austria), paper PD2.6 (2009). |

13. | S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express |

14. | K. Lee, C. T. D. Thai, and J.-K. K. Rhee, “All optical discrete Fourier transform processor for 100 Gbps OFDM transmission,” Opt. Express |

15. | K. Takiguchi, M. Oguma, H. Takahashi, and A. Mori, “PLC-based eight-channel OFDM demultiplexer and its demonstration with 160 Gbit/s signal reception,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OThB4 (2010). |

16. | Y. Huang, D. Qian, R. E. Saperstein, P. N. Ji, N. Cvijetic, L. Xu, and T. Wang, “Dual-polarization 2x2 IFFT/FFT optical signal processing for 100-Gb/s QPSK-PDM all-optical OFDM,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2009), paper OTuM4 (2009). |

17. | D. Hillerkuss, M. Winter, M. Teschke, A. Marculescu, J. Li, G. Sigurdsson, K. Worms, S. Ben Ezra, N. Narkiss, W. Freude, and J. Leuthold, “Simple all-optical FFT scheme enabling Tbit/s real-time signal processing,” Opt. Express |

18. | A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express |

19. | C. R. Doerr and K. Okamoto, “Advances in silica planar lightwave circuits,” J. Lightwave Technol. |

20. | M. K. Smit and C. Van Dam, “PHASAR-based WDM-devices: Principles, design and applications,” IEEE J. Sel. Top. Quantum Electron. |

21. | G. Cincotti, N. Wada, and K. Kitayama, “Characterization of a full encoder/decoder in the AWG configuration for code-based photonic routers—part I: modeling and design,” J. Lightwave Technol. |

22. | K. Takada, M. Abe, and K. Okamoto, “Low-cross-talk polarization-insensitive 10-GHz-spaced 128-channel arrayed-waveguide grating multiplexer-demultiplexer achieved with photosensitive phase adjustment,” Opt. Lett. |

23. | K. Takada, M. Abe, M. Shibata, M. Ishii, and K. Okamoto, “Low-Crosstalk 10-GHz-spaced 512-channel arrayed-waveguide grating multi/demultiplexer fabricated on a 4-in wafer,” IEEE Photon. Technol. Lett. |

24. | G. Goldfarb, G. Li, and M. G. Taylor, “Orthogonal wavelength-division multiplexing using coherent detection,” IEEE Photon. Technol. Lett. |

**OCIS Codes**

(060.2330) Fiber optics and optical communications : Fiber optics communications

(070.7145) Fourier optics and signal processing : Ultrafast processing

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: January 5, 2011

Revised Manuscript: February 6, 2011

Manuscript Accepted: February 6, 2011

Published: February 23, 2011

**Citation**

Zhenxing Wang, Konstantin S. Kravtsov, Yue-Kai Huang, and Paul R. Prucnal, "Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system," Opt. Express **19**, 4501-4512 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-5-4501

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### References

- H. Sanjoh, E. Yamada, and Y. Yoshikuni, “Optical orthogonal frequency division multiplexing using frequency/time domain filtering for high spectral efficiency up to 1 bit/s/Hz,” in Conference on Optical Fiber Communication, OFC (Anaheim, CA, 2002), paper ThD1, 401–402 (2002).
- W. Shieh and I. Djordjevic, OFDM for Optical Communications, Academic Press, 2009.
- A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express 14(6), 2079–2084 (2006). [CrossRef] [PubMed]
- W. Shieh, W. Chen, and R. S. Tucker, “Polarization mode dispersion mitigation in coherent optical orthogonal frequency division multiplexed systems,” Electron. Lett. 42(17), 996–997 (2006). [CrossRef]
- Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, D. Rangaraj, A. Cartolano, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing,” Opt. Express 17(20), 17658–17668 (2009). [CrossRef] [PubMed]
- Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express 17(10), 7985–7992 (2009). [CrossRef] [PubMed]
- F. Buchali, R. Dischler, A. Klekamp, M. Bernhard, and Y. Ma, “Statistical Transmission Experiments Using a Real-Time 12.1 Gb/s OFDM Transmitter”, in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OMS3 (2010).
- S. Chen, Y. Ma, and W. Shieh, 110-Gb/s Multi-Band Real-Time Coherent Optical OFDM Reception after 600-km Transmission over SSMF Fiber”, in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OMS2 (2010).
- D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Möller, M. Hübner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8Tb/s,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper PDPC1 (2010).
- H. Chen, M. Chen, and S. Xie, “All-optical sampling orthogonal frequency-division multiplexing scheme for high-speed transmission system,” J. Lightwave Technol. 27(21), 4848–4854 (2009). [CrossRef]
- F. C. Garcia Gunning, S. K. Ibrahim, P. Frascella, P. Gunning, and A. D. Ellis, “High symbol rate OFDM transmission technologies”,in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OThD1 (2010).
- S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Peckham, “Transmission of a 1.2 Tb/s 24-carrier no-guad-interval coherent OFDM superchannel over 7200-km of Ultra-Large-Area Fiber,” in Proc. ECOC 2009 (Vienna, Austria), paper PD2.6 (2009).
- S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express 17(24), 21350–21361 (2009). [CrossRef] [PubMed]
- K. Lee, C. T. D. Thai, and J.-K. K. Rhee, “All optical discrete Fourier transform processor for 100 Gbps OFDM transmission,” Opt. Express 16(6), 4023–4028 (2008). [CrossRef] [PubMed]
- K. Takiguchi, M. Oguma, H. Takahashi, and A. Mori, “PLC-based eight-channel OFDM demultiplexer and its demonstration with 160 Gbit/s signal reception,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2010), paper OThB4 (2010).
- Y. Huang, D. Qian, R. E. Saperstein, P. N. Ji, N. Cvijetic, L. Xu, and T. Wang, “Dual-polarization 2x2 IFFT/FFT optical signal processing for 100-Gb/s QPSK-PDM all-optical OFDM,” in Conference on Optical Fiber Communication, OFC (San Diego, CA, 2009), paper OTuM4 (2009).
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