## Electronic dispersion compensation in a 50 Gb/s optically unamplified direct-detection receiver enabled by vestigial-sideband orthogonal frequency division multiplexing |

Optics Express, Vol. 22, Issue 6, pp. 6984-6995 (2014)

http://dx.doi.org/10.1364/OE.22.006984

Acrobat PDF (1336 KB)

### Abstract

We present a novel method for dispersion compensation based on vestigial-sideband transmission of an orthogonal frequency division multiplexed signal through standard signal-mode fiber with a direct-detection receiver. This technique requires simpler optical components and can withstand greater link attenuation and splitting ratios than similar methods previously studied, making the method ideal for optically unamplified receivers, such as those in passive optical networks. We present simulations as well as experimental measurements to demonstrate its practicality.

© 2014 Optical Society of America

## 1. Introduction

4. X. Chen, A. Li, Q. Hu, J. He, Y. W. D. Che, and W. Shieh, “Demonstration of direct detected optical OFDM signals via block-wise phase switching,” J. Lightw. Technol. **32**, 722–728 (2014). [CrossRef]

8. J. L. Wei, X. Q. Jin, and J. M. Tang, “The influence of directly modulated DFB lasers on the transmission performance of carrier-suppressed single-sideband optical OFDM signals over IMDD SMF systems,” J. Lightw. Technol. **27**, 2412–2419 (2009). [CrossRef]

9. B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightw. Technol. **27**, 196–203 (2008). [CrossRef]

15. D. Y. Qian, N. Cvijetic, J. Q. Hu, and T. Wang, “108 Gb/s OFDMA-PON with polarization multiplexing and direct detection,” J. Lightw. Technol. **28**, 484–493 (2010). [CrossRef]

16. G. H. Smith, D. Novak, and Z. Ahmed, “Overcoming chromatic-dispersion effects in fiber-wireless systems incorporating external modulators,” IEEE Trans. Microw. Theory Techn. **45**, 1410–1415 (1997). [CrossRef]

17. M. Sieben, J. Conradi, and D. E. Dodds, “Optical single sideband transmission at 10 Gb/s using only electrical dispersion compensation,” J. Lightw. Technol. **17**, 1742–1749 (1999). [CrossRef]

10. W. R. Peng, X. X. Wu, V. R. Arbab, K. M. Feng, B. Shamee, L. C. Christen, J. Y. Yang, A. E. Willner, and S. Chi, “Theoretical and experimental investigations of direct-detected RF-tone-assisted optical OFDM systems,” J. Lightw. Technol. **27**, 1332–1339 (2009). [CrossRef]

14. B. J. C. Schmidt, Z. Zan, L. B. Du, and A. J. Lowery, “120 Gbit/s over 500-km using single-band polarization-multiplexed self-coherent optical OFDM,” J. Lightw. Technol. **28**, 328–335 (2010). [CrossRef]

15. D. Y. Qian, N. Cvijetic, J. Q. Hu, and T. Wang, “108 Gb/s OFDMA-PON with polarization multiplexing and direct detection,” J. Lightw. Technol. **28**, 484–493 (2010). [CrossRef]

18. N. Cvijetic, “OFDM for next-generation optical access networks,” J. Lightw. Technol. **30**, 384–398 (2012). [CrossRef]

## 2. Increasing transmission reach in optically unamplified links

9. B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightw. Technol. **27**, 196–203 (2008). [CrossRef]

10. W. R. Peng, X. X. Wu, V. R. Arbab, K. M. Feng, B. Shamee, L. C. Christen, J. Y. Yang, A. E. Willner, and S. Chi, “Theoretical and experimental investigations of direct-detected RF-tone-assisted optical OFDM systems,” J. Lightw. Technol. **27**, 1332–1339 (2009). [CrossRef]

10. W. R. Peng, X. X. Wu, V. R. Arbab, K. M. Feng, B. Shamee, L. C. Christen, J. Y. Yang, A. E. Willner, and S. Chi, “Theoretical and experimental investigations of direct-detected RF-tone-assisted optical OFDM systems,” J. Lightw. Technol. **27**, 1332–1339 (2009). [CrossRef]

*R*is the clipping ratio in linear units,

_{cl}*a*is a scaling corresponding to the MZM insertion loss, and

*m*is a scaling corresponding to using only the linear region of the MZM cosine transfer characteristic. We define

*R*=

_{cl}*x*

_{0}/

*σ*, where

*x*

_{0}is the clipping limit and

*σ*is the standard deviation of the MZM drive signal. For example, with 8 dB clipping, 6 dB insertion loss, and a use of

*m*= 1/2 of the MZM’s dynamic range,

*K*= 7.1, or 17 dB. Although, in principle, one could compensate for the attenuation of the modulator with a higher power laser, there are practical limits to the output power of semiconductor lasers.

## 3. Vestigial-sideband transmission

19. C. K. Madsen and J. H. Zhao, *Optical Filter Design and Analysis* (Wiley Interscience, 1999). [CrossRef]

*x*(

*t*) and the DC offset added to it be

*A*. Let the impulse responses of the optical filter and fiber be

*f*(

*t*) and

*g*(

*t*), respectively. Let their respective Fourier transforms be

*F*(

*ω*) and

*G*(

*ω*). Then the received E-field is where

***denotes convolution. Let

*B*=

*A**

*g*(

*t*) =

*AG*(0), a complex constant. Let

*h*(

*t*) =

*f*(

*t*) *

*g*(

*t*) be the composite channel

*x*(

*t*) traverses. Then the intensity at the receiver is The first term of (3) is at DC. The second term is intermodulation; it is largest at DC and decreases with increasing frequency. The final term

*y*(

*t*) = 2Re{

*B*

^{*}

*x*(

*t*) *

*h*(

*t*)} is the desired signal term. It can be equivalently be expressed as where The corresponding transfer function for this system is When the real OFDM signal

*x*(

*t*) is chosen such that it occupies the frequency bands (−2

*ω*, −

_{B}*ω*) and (

_{B}*ω*, 2

_{B}*ω*), the intermodulation term (caused by signal-signal beating) |

_{B}*x*(

*t*) *

*h*(

*t*)|

^{2}will occupy the band (−

*ω*,

_{B}*ω*). Thus after highpass filtering, the received signal becomes

_{B}*y*(

*t*), so the system between the transmitted OFDM signal and the received signal is linear. It is apparent that the magnitude of the received signal is proportional to |

*A*|, the magnitude of the transmitted carrier. Thus, adding the carrier through the parallel waveguide results in a much larger received signal than if the carrier (or virtual carrier) were generated through the modulator. If the carrier is sufficiently large compared to the signal, the linear signal term

*y*(

*t*) will become large compared to the intermodulation term |

*x*(

*t*) *

*h*(

*t*)|

^{2}, even if

*x*(

*t*) is allowed to occupy the entire band (0, 2

*ω*) rather than just (

_{B}*ω*, 2

_{B}*ω*). Depending on the relative magnitude of intermodulation compared to receiver thermal and shot noise, it may be advantageous to have a reduced guard band or no guard band at all.

_{B}*β*

_{2}is the group-velocity dispersion parameter, and

*L*is the fiber length. Suppose the optical filter is absent, or equivalently,

*F*(

*ω*) = 1 for all

*ω*. For simplicity of discussion, we will consider

*B*= 1, but this does not affect the results. Then by (6), Such a transfer function has many nulls and thus has low capacity. The origin of the nulls is the even symmetry in

*H*(

*ω*). One can ask whether insertion of an optical filter

*F*(

*ω*) can break this symmetry and prevent formation of nulls. One particular choice of

*F*(

*ω*) which achieves this is Note that such a choice of

*F*(

*ω*) is equivalent to using SSB modulation with an IQ-MZM and no optical filter present. However, such a sharp filter will be high in order; it would be preferable to use a low-order planar waveguide-based filter which can be integrated with the MZM. In this work, we study the two-branch MZI with a complex-envelope transfer function where

*ω*is the optical carrier frequency (rad/s) and

_{c}*t*is the time-delay difference between the two arms of the MZI. The delay

_{d}*t*can be tuned through temperature control. Such a filter has a periodic spectrum with period

_{d}*f*= 1/

_{FSR}*t*(Hz), the free spectral range (FSR). Figure 3(a) shows a schematic of the MZI and Fig. 3(b) shows a representative transfer function. In this work, we investigate the performance of a system based on such an MZI as the optical filter for preventing formation of nulls in the composite channel transfer function

_{d}*H*(

_{eq}*ω*). Since an MZI will not completely suppress one of the sidebands, we call this method of transmission vestigial-sideband (VSB) OFDM.

*ω*and

_{c}*t*. The FSR depends only on

_{d}*t*, but the frequency offset of the transfer function relative to the carrier depends on the product

_{d}*ω*. However, to tune the MZI to the desired operating point, one only needs to control

_{c}t_{d}*t*, because minute fractional changes in

_{d}*t*will change

_{d}*ω*by 2

_{c}t_{d}*π*. Thus, the frequency-center of the MZI transfer function can be controlled arbitrarily with negligible impact on the FSR. The FSR is essentially determined only by the fabricated length difference of the two waveguides.

*G*(

*ω*) being the dispersion transfer function. We can without loss of generality assume

*B*= 1. Then the equivalent channel transfer function is When the MZI is placed asymmetrically about the carrier frequency, so that its null is well within one of the sidebands, |

*F*(

*ω*)| ≠ |

*F*(−

*ω*)|.

*H*(

_{eq}*ω*) is the sum of two phasors;

*H*(

_{eq}*ω*) = 0 if and only if these two phasors have the same magnitude and opposite angle. However, since |

*F*(

*ω*)| ≠ |

*F*(−

*ω*)|, these two phasors will have different magnitudes. Thus, the MZI prevents formation of a channel null.

## 4. Simulations

*x*

_{0}/

*V*= 1/2 (where

_{π}*V*is the MZM switching voltage), fiber dispersion of 18 ps/nm/km and loss of 0.2 dB/km, photodiode responsivity of 0.8 A/W, and receiver thermal noise of

_{π}20. G. P. Agrawal, *Fiber-Optic Communication Systems* (John Wiley and Sons, 2002). [CrossRef]

^{−3}.

*b*is the number of bits/symbol transmitted by the

_{i}*i*

^{th}subcarrier,

*SNR*is the signal-to-noise ratio (SNR) of the

_{i}*i*

^{th}subchannel, and Γ is the gap constant determined by the desired BER [21

21. J. M. Cioffi, G. P. Dudevoir, M. V. Eyuboglu, and G. D. Forney, “MMSE decision-feedback equalizers and coding-part II: Coding results,” IEEE Trans. Commun. **43**, 2595–2604 (1995). [CrossRef]

^{−3}. To optimize the power and bit allocation among the subcarriers, we employed Campello’s bit-loading algorithm, which is the optimal discrete-bit-allocation algorithm [22]. The performance gained by bit loading is the result of the non-uniform SNR over frequency. A frequency-varying SNR is also present in systems with multi-mode dispersion, resulting in significant gains through bit loading [23].

24. D. J. F. Barros and J. M. Kahn, “Comparison of orthogonal frequency-division multiplexing and on-off keying in amplified direct-detection single-mode fiber systems,” J. Lightw. Technol. **28**, 1811–1820 (2010). [CrossRef]

## 5. Experimental measurements

^{−3}. This provides ample margin for meeting the standard rate of 50 Gb/s/wavelength. Additionally, its performance is insensitive to ±3 GHz drift of the MZI relative to the carrier frequency, as shown in Fig. 7(b). In Fig. 8(a), we show the SNR of the composite channel from the transmitter’s digital output to the receiver’s digital output. In Fig. 8(b), we show the corresponding optimal bit allocation for the case of 72 Gb/s transmission. The 256

^{th}subcarrier was zeroed due to strong DAC nonlinearity at that frequency.

## 6. Conclusions

## 7. Appendix

*x*

_{+}(

*t*) is produced by a summation of a DSB signal

*x*(

*t*) with its Hilbert transform

*x̂*(

*t*) [25]: The transmitted signal is combined with the virtual carrier

*C*exp(−

*jω*), where

_{B}t*C*is assumed real without loss of generality. To create this complex carrier, the MZM in the in-phase branch (I-MZM) is modulated with the real signal

*s*(

_{I}*t*) =

*x*(

*t*) +

*C*exp(−

*jω*) +

_{B}t*C*exp(

*jω*). Similarly the Q-MZM is modulated with the real signal

_{B}t*s*(

_{Q}*t*) =

*x̂*(

*t*) −

*jC*exp(−

*jω*) +

_{B}t*jC*exp(

*jω*). For any real system, the output of the DAC will be clipped to some extent; otherwise its dynamic range is wasted [26

_{B}t26. E. Vanin, “Performance evaluation of intensity modulated optical OFDM system with digital baseband distortion,” Opt. Express **19**, 4280–4293 (2011). [CrossRef] [PubMed]

*s*and

_{I}*s*do not explicitly include a term to represent the added clipping error, but for the following analysis, excluding this extra “noise” term in the expressions will not have much effect, as long as clipping is not extreme. However, it must be noted that clipping will limit

_{Q}*s*and

_{I}*s*to within ±

_{Q}*x*

_{0}, where ±

*x*

_{0}are the most positive and negative DAC output voltages. For convenience, we will choose

*x*

_{0}= 1.

*s*(or

_{I}*s*) and E-field output is a constant scaling factor. This scaling factor depends on the magnitude of

_{Q}*s*relative to

_{I}*V*, the switching voltage of the MZM. We will denote this scaling factor by

_{π}*m*. For example, if the MZM drive signal is at its maximum of

*x*

_{0}= 1, then the MZM output will be

*mE*, where

_{in}*E*is the input field into the MZM. However, this neglects the insertion loss of the MZM. We represent the insertion loss with a scaling constant

_{in}*a*. Thus, for the previous example, the MZM output is

*amE*when the drive

_{in}*s*is at its peak.

_{I}*A*be the amplitude of the CW source of the modulator. Since this source is split evenly between the I-MZM and Q-MZM, the output of the modulator, after summing I and Q branches, is

_{cw}*y*(

*t*) is a DSB signal and let

*E*[

*y*

^{2}(

*t*)] =

*E*[

*x*

^{2}(

*t*)]. In order to make a fair comparison with the virtual carrier transmitter, the MZM should be driven with a signal of the same power in both cases. Since no virtual carrier is present here, the MZM should be driven with

*y*(

*t*) is converted to the SSB signal

*y*

_{+}(

*t*).

*A*. It is split into two paths, one which passes through an MZM and the other unmodulated. It can be easily shown that the receiver’s signal is largest when the split is equal in both paths. Thus, the output of the unmodulated waveguide is

_{cw}*A*/2 (we can neglect the phase without changing the results) and the output of the modulated and filtered branch is

_{cw}## 8. Acknowledgments

## References and links

1. | W. Z. Yan, T. Tanaka, B. Liu, M. Nishihara, L. Li, T. Takahara, Z. Tao, J. C. Rasmussen, and T. Drenski, “100 Gb/s optical IM-DD transmission with 10G-class devices enabled by 65 GSamples/s CMOS DAC core,” “OFC/NFOEC 2013” (Anaheim, USA, 2013), p. OM3H.1. |

2. | I. Dedic, “56Gs/s ADC: Enabling 100GbE,” “OFC/NFOEC 2010,” (San Diego, USA, 2010), p. OThT6. |

3. | X. Chen, A. Li, D. Che, Q. Hu, Y. Wang, J. He, and W. Shieh, “High-speed fading-free direct detection for double-sideband OFDM signal via block-wise phase switching,” “OFC/NFOEC,” (2013), p. PDP5B.7. |

4. | X. Chen, A. Li, Q. Hu, J. He, Y. W. D. Che, and W. Shieh, “Demonstration of direct detected optical OFDM signals via block-wise phase switching,” J. Lightw. Technol. |

5. | D. F. Hewitt, “Orthogonal frequency division multiplexing using baseband optical single sideband for simpler adaptive dispersion compensation,” in “Proc. Eur. Conf. Opt. Commun.”, (2007), p. OME7. |

6. | M. Schuster, B. Spinnler, C. A. Bunge, and K. Petermann, “Spectrally efficient OFDM-transmission with compatible single-sideband modulation for direct detection,” in “ |

7. | M. Schuster, S. Randel, C. A. Bunge, S. C. J. Lee, F. Breyer, B. Spinnler, and K. Petermann, “Spectrally efficient compatible single-sideband modulation for OFDM transmission with direct detection,” IEEE Photon. Technol. Lett. |

8. | J. L. Wei, X. Q. Jin, and J. M. Tang, “The influence of directly modulated DFB lasers on the transmission performance of carrier-suppressed single-sideband optical OFDM signals over IMDD SMF systems,” J. Lightw. Technol. |

9. | B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightw. Technol. |

10. | W. R. Peng, X. X. Wu, V. R. Arbab, K. M. Feng, B. Shamee, L. C. Christen, J. Y. Yang, A. E. Willner, and S. Chi, “Theoretical and experimental investigations of direct-detected RF-tone-assisted optical OFDM systems,” J. Lightw. Technol. |

11. | W. R. Peng, B. Zhang, K. M. Feng, X. X. Wu, A. E. Willner, and S. Chi, “Spectrally efficient direct-detected OFDM transmission incorporating a tunable frequency gap and an iterative detection techniques,” J. Lightw. Technol. |

12. | W. R. Peng, I. Morita, and H. Tanaka, “Enabling high capacity direct-detection optical OFDM transmissions using beat interference cancellation receiver,” in “ |

13. | S. A. Nezamalhosseini, L. R. Chen, Q. B. Zhuge, M. Malekiha, F. Marvasti, and D. V. Plant, “Theoretical and experimental investigation of direct detection optical OFDM transmission using beat interference cancellation receiver,” Opt. Express |

14. | B. J. C. Schmidt, Z. Zan, L. B. Du, and A. J. Lowery, “120 Gbit/s over 500-km using single-band polarization-multiplexed self-coherent optical OFDM,” J. Lightw. Technol. |

15. | D. Y. Qian, N. Cvijetic, J. Q. Hu, and T. Wang, “108 Gb/s OFDMA-PON with polarization multiplexing and direct detection,” J. Lightw. Technol. |

16. | G. H. Smith, D. Novak, and Z. Ahmed, “Overcoming chromatic-dispersion effects in fiber-wireless systems incorporating external modulators,” IEEE Trans. Microw. Theory Techn. |

17. | M. Sieben, J. Conradi, and D. E. Dodds, “Optical single sideband transmission at 10 Gb/s using only electrical dispersion compensation,” J. Lightw. Technol. |

18. | N. Cvijetic, “OFDM for next-generation optical access networks,” J. Lightw. Technol. |

19. | C. K. Madsen and J. H. Zhao, |

20. | G. P. Agrawal, |

21. | J. M. Cioffi, G. P. Dudevoir, M. V. Eyuboglu, and G. D. Forney, “MMSE decision-feedback equalizers and coding-part II: Coding results,” IEEE Trans. Commun. |

22. | J. Campello, “Practical bit loading for DMT,” in “ |

23. | S. Lee, F. Breyer, S. Randel, M. Schuster, J. Zeng, F. Huijskens, H. van den Boom, A. Koonen, and N. Hanik, “24-Gb/s transmission over 730 m of multimode fiber by direct modulation of an 850-nm VCSEL using discrete multi-tone modulation,” “OFC/NFOEC,” (2007), p. PDP6. |

24. | D. J. F. Barros and J. M. Kahn, “Comparison of orthogonal frequency-division multiplexing and on-off keying in amplified direct-detection single-mode fiber systems,” J. Lightw. Technol. |

25. | J. G. Proakis and M. Salehi, |

26. | E. Vanin, “Performance evaluation of intensity modulated optical OFDM system with digital baseband distortion,” Opt. Express |

**OCIS Codes**

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

(060.4080) Fiber optics and optical communications : Modulation

(060.4510) Fiber optics and optical communications : Optical communications

**ToC Category:**

Optical Communications

**History**

Original Manuscript: December 27, 2013

Revised Manuscript: February 28, 2014

Manuscript Accepted: March 1, 2014

Published: March 18, 2014

**Citation**

William A. Ling and Ilya Lyubomirsky, "Electronic dispersion compensation in a 50 Gb/s optically unamplified direct-detection receiver enabled by vestigial-sideband orthogonal frequency division multiplexing," Opt. Express **22**, 6984-6995 (2014)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-6-6984

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### References

- W. Z. Yan, T. Tanaka, B. Liu, M. Nishihara, L. Li, T. Takahara, Z. Tao, J. C. Rasmussen, T. Drenski, “100 Gb/s optical IM-DD transmission with 10G-class devices enabled by 65 GSamples/s CMOS DAC core,” “OFC/NFOEC 2013” (Anaheim, USA, 2013), p. OM3H.1.
- I. Dedic, “56Gs/s ADC: Enabling 100GbE,” “OFC/NFOEC 2010,” (San Diego, USA, 2010), p. OThT6.
- X. Chen, A. Li, D. Che, Q. Hu, Y. Wang, J. He, W. Shieh, “High-speed fading-free direct detection for double-sideband OFDM signal via block-wise phase switching,” “OFC/NFOEC,” (2013), p. PDP5B.7.
- X. Chen, A. Li, Q. Hu, J. He, Y. W. D. Che, W. Shieh, “Demonstration of direct detected optical OFDM signals via block-wise phase switching,” J. Lightw. Technol. 32, 722–728 (2014). [CrossRef]
- D. F. Hewitt, “Orthogonal frequency division multiplexing using baseband optical single sideband for simpler adaptive dispersion compensation,” in “Proc. Eur. Conf. Opt. Commun.”, (2007), p. OME7.
- M. Schuster, B. Spinnler, C. A. Bunge, K. Petermann, “Spectrally efficient OFDM-transmission with compatible single-sideband modulation for direct detection,” in “Proc. Eur. Conf. Opt. Commun.”, (Berlin, Germany, 2007), pp. 1–2.
- M. Schuster, S. Randel, C. A. Bunge, S. C. J. Lee, F. Breyer, B. Spinnler, K. Petermann, “Spectrally efficient compatible single-sideband modulation for OFDM transmission with direct detection,” IEEE Photon. Technol. Lett. 20, 670–672 (2008). [CrossRef]
- J. L. Wei, X. Q. Jin, J. M. Tang, “The influence of directly modulated DFB lasers on the transmission performance of carrier-suppressed single-sideband optical OFDM signals over IMDD SMF systems,” J. Lightw. Technol. 27, 2412–2419 (2009). [CrossRef]
- B. J. C. Schmidt, A. J. Lowery, J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightw. Technol. 27, 196–203 (2008). [CrossRef]
- W. R. Peng, X. X. Wu, V. R. Arbab, K. M. Feng, B. Shamee, L. C. Christen, J. Y. Yang, A. E. Willner, S. Chi, “Theoretical and experimental investigations of direct-detected RF-tone-assisted optical OFDM systems,” J. Lightw. Technol. 27, 1332–1339 (2009). [CrossRef]
- W. R. Peng, B. Zhang, K. M. Feng, X. X. Wu, A. E. Willner, S. Chi, “Spectrally efficient direct-detected OFDM transmission incorporating a tunable frequency gap and an iterative detection techniques,” J. Lightw. Technol. 27, 5723–5735 (2009). [CrossRef]
- W. R. Peng, I. Morita, H. Tanaka, “Enabling high capacity direct-detection optical OFDM transmissions using beat interference cancellation receiver,” in “Proc. Eur. Conf. Opt. Commun.”, (Torino, Italy, 2010), p. Tu.4.A.2.
- S. A. Nezamalhosseini, L. R. Chen, Q. B. Zhuge, M. Malekiha, F. Marvasti, D. V. Plant, “Theoretical and experimental investigation of direct detection optical OFDM transmission using beat interference cancellation receiver,” Opt. Express 21, 15237–15246 (2013). [CrossRef] [PubMed]
- B. J. C. Schmidt, Z. Zan, L. B. Du, A. J. Lowery, “120 Gbit/s over 500-km using single-band polarization-multiplexed self-coherent optical OFDM,” J. Lightw. Technol. 28, 328–335 (2010). [CrossRef]
- D. Y. Qian, N. Cvijetic, J. Q. Hu, T. Wang, “108 Gb/s OFDMA-PON with polarization multiplexing and direct detection,” J. Lightw. Technol. 28, 484–493 (2010). [CrossRef]
- G. H. Smith, D. Novak, Z. Ahmed, “Overcoming chromatic-dispersion effects in fiber-wireless systems incorporating external modulators,” IEEE Trans. Microw. Theory Techn. 45, 1410–1415 (1997). [CrossRef]
- M. Sieben, J. Conradi, D. E. Dodds, “Optical single sideband transmission at 10 Gb/s using only electrical dispersion compensation,” J. Lightw. Technol. 17, 1742–1749 (1999). [CrossRef]
- N. Cvijetic, “OFDM for next-generation optical access networks,” J. Lightw. Technol. 30, 384–398 (2012). [CrossRef]
- C. K. Madsen, J. H. Zhao, Optical Filter Design and Analysis (Wiley Interscience, 1999). [CrossRef]
- G. P. Agrawal, Fiber-Optic Communication Systems (John Wiley and Sons, 2002). [CrossRef]
- J. M. Cioffi, G. P. Dudevoir, M. V. Eyuboglu, G. D. Forney, “MMSE decision-feedback equalizers and coding-part II: Coding results,” IEEE Trans. Commun. 43, 2595–2604 (1995). [CrossRef]
- J. Campello, “Practical bit loading for DMT,” in “Proc. Global Telecommun. Conf. (GLOBECOM ’99),” (Vancouver, Canada, 1999), pp. 801–805.
- S. Lee, F. Breyer, S. Randel, M. Schuster, J. Zeng, F. Huijskens, H. van den Boom, A. Koonen, N. Hanik, “24-Gb/s transmission over 730 m of multimode fiber by direct modulation of an 850-nm VCSEL using discrete multi-tone modulation,” “OFC/NFOEC,” (2007), p. PDP6.
- D. J. F. Barros, J. M. Kahn, “Comparison of orthogonal frequency-division multiplexing and on-off keying in amplified direct-detection single-mode fiber systems,” J. Lightw. Technol. 28, 1811–1820 (2010). [CrossRef]
- J. G. Proakis, M. Salehi, Digital Communications (McGraw-Hill, 2008), 5th ed.
- E. Vanin, “Performance evaluation of intensity modulated optical OFDM system with digital baseband distortion,” Opt. Express 19, 4280–4293 (2011). [CrossRef] [PubMed]

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