## Theoretical and experimental investigation of direct detection optical OFDM transmission using beat interference cancellation receiver |

Optics Express, Vol. 21, Issue 13, pp. 15237-15246 (2013)

http://dx.doi.org/10.1364/OE.21.015237

Acrobat PDF (772 KB)

### Abstract

We theoretically and experimentally evaluate a beat interference cancellation receiver (BICR) for direct detection optical orthogonal frequency-division multiplexing (DD-OFDM) systems that improves the spectral efficiency (SE) by reducing the guard band between the optical carrier and the optical OFDM signal while mitigating the impact of signal-signal mixing interference (SSMI). Experimental results show that the bit-error-rate (BER) is improved by about three orders of magnitude compared to the conventional receiver after 320 km single-mode fiber (SMF) transmission for 10 Gb/s data with a 4-QAM modulation using reduced guard band single-sideband OFDM (RSSB-OFDM) signal with 1.67 bits/s/Hz SE.

© 2013 osa

## 1. Introduction

1. N. Cvijetic, “OFDM for next-generation optical access networks,” IEEE J. Lightw. Technol. **30**(4), 384–398 (2012) [CrossRef] .

2. Peter J. Winzer, “High-spectral-efficiency optical modulation formats,” IEEE J. Lightw. Technol. **30**(24), 3824–3835 (2012) [CrossRef] .

3. J. Armstrong, “OFDM for optical communications,” IEEE J. Lightw. Technol. **27**(3), 189–204 (2009) [CrossRef] .

4. 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,” IEEE J. Lightw. Technol. **26**(1), 196–203 (2008) [CrossRef] .

5. W. Shieh, H. Bao, and Y. Tang, “Coherent optical OFDM: theory and design,” Opt. Express **16**(2), 841–859 (2008) [CrossRef] [PubMed] .

6. W. Shieh, X. Yi, Y. Ma, and Q. Yang, “Coherent optical OFDM: has its time come?,” J. Optical Networking **7**(3), 234–255 (2008) [CrossRef] .

4. 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,” IEEE J. Lightw. Technol. **26**(1), 196–203 (2008) [CrossRef] .

5. W. Shieh, H. Bao, and Y. Tang, “Coherent optical OFDM: theory and design,” Opt. Express **16**(2), 841–859 (2008) [CrossRef] [PubMed] .

7. Q. Zhuge, M. Morsy-Osman, M. E. Mousa-Pasandi, X. Xu, M. Chagnon, Z. A. El-Sahn, C. Chen, and D. V. Plant, “Single channel and WDM transmission of 28 Gbaud zero-guard-interval CO-OFDM,” Opt. Express **20**(26), 439–444 (2012) [CrossRef] .

9. T. Pollet, M. V. Blade, and M. Moeneclaey, “BER sensitivity of OFDM systems to carrier frequency offset and Wiener phase noise,”IEEE Tran. on Communiacation **43**(2/3/4), 191–193 (1995) [CrossRef] .

10. X. Yi, W. Shieh, and Y. Ma, “Phase noise effects on high spectral efficiency coherent optical OFDM transmission,” IEEE J. Lightw. Technol. **26**(10), 1309–1316 (2008) [CrossRef] .

3. J. Armstrong, “OFDM for optical communications,” IEEE J. Lightw. Technol. **27**(3), 189–204 (2009) [CrossRef] .

4. 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,” IEEE J. Lightw. Technol. **26**(1), 196–203 (2008) [CrossRef] .

12. 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] .

12. 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] .

13. I. V. Djordjevic and B. Vasic, “Orthogonal frequency division multiplexing for high-speed optical transmission,” Opt. Express **14**(9), 3767–3775 (2006) [CrossRef] [PubMed] .

15. Z. Cao, J. Yu, W. Wang, L. Chen, and Z. Dong, “Direct-detection optical OFDM transmission system without frequency guard band,”IEEE Photon. Technol. Lett. **22**(11), 736–738 (2010) [CrossRef] .

16. D. Qian, J. Yu, J. Hu, L. Zong, L. Xu, and T. Wang, “10 Gbit/s WDM-SSB-OFDM transmissions over 1000 km SSMF using conventional DFB lasers and direct-detection,” Electronic Letter **44**(3), 223–225 (2008) [CrossRef] .

17. W. Peng, I. Morita, and H. Tanaka, “Enabling high capacity direct-detection optical OFDM transmissions using beat interference cancellation receiver,” in *European Conference and Exhibition on Optical Communication*(ECOC2010), paper Tu.4.A.2 [CrossRef] .

## 2. System model

*H*(

_{CD}*f*)). Hence, the signal, and the added amplified spontaneous emission (ASE) noise by erbium-doped-fiber-amplifiers (EDFAs) can be assumed independent. Therefore, the received signal at the PD can be represented as [11

11. W. Peng, B. Zhang, K. Feng, X. Wu, A. E. Willner, and S. Chi, “Spectrally efficient direct-detected OFDM transmission incorporating a tunable frequency gap and an iterative detection techniques,” IEEE J. Lightw. Technol. **27**(24), 5723–5735 (2009) [CrossRef] .

*H*(

_{TF}*f*) =

*H*(

_{O}*f*)

*H*(

_{T}*f*)

*H*(

_{CD}*f*) denotes the overall transfer function from the transmitter to the receiver, and

*n*(

_{ASE}*t*) represents the ASE noise as complex circular AWGN. We denote the frequency responses of the optical fiber, and optical filters as

*H*(

_{CD}*f*), and

*H*(

_{O}*f*), respectively. At the receiver, the PD is modeled as an ideal square-law device [20] with quantum efficiency equal to one. Therefore, the resultant photocurrent after the PD can be expressed as follows

*Re*{x} denotes the real value of

*x*. In the rest of the paper, for simplicity,

*Ĥ*(

_{x}*n*,

*m*) is defined as

*n*(

_{SABN}*t*),

*n*(

_{AABN}*t*), and

*n*(

_{CABN}*t*) are the signal-ASE beat noise (SABN), the ASE-ASE beat noise (AABN), and the carrier-ASE beat noise (CABN), respectively. The power spectral density (PSD) of these noises has been studied in [19

19. W. Peng, K. Feng, A. E. Willner, and S. Chi, “Estimation of the bit error rate for direct-detected OFDM signals with optically preamplified receivers,” IEEE J. Lightw. Technol. **27**(10), 1340–1346 (2009) [CrossRef] .

*n*th subcarrier (0 ≤

*n*) can be expressed as follows This expression shows that the SBBI is distributed from the dc to the (

*N*− 1)th subcarrier. Moreover, the desired term at the

*n*th subcarrier (0 ≤

*n*) can be shown as

## 3. Theoretical model of BICR

*B*, the BICR was proposed in [17

17. W. Peng, I. Morita, and H. Tanaka, “Enabling high capacity direct-detection optical OFDM transmissions using beat interference cancellation receiver,” in *European Conference and Exhibition on Optical Communication*(ECOC2010), paper Tu.4.A.2 [CrossRef] .

*r*) and the photocurrent in the upper branch (

_{U}*q*) are given by Eqs. (2) and (3), respectively. The optical signal prior to a PD in the lower branch (

_{U}*r*) can be written as

_{L}*H*(

_{OF}*f*) represents the transfer function of the optical filter in the lower branch. Therefore, the photocurrent in the lower (

*q*) branch can be noted as follows

_{L}*q*(

_{U}*t*) from

*q*(

_{L}*t*), we have

*n*th subcarrier (0 ≤

*n*) can be expressed as And the desired term at the

*n*th subcarrier (0 ≤

*n*) can be shown as In the case of an ideal optical filter where the optical carrier can be removed completely without affecting the OOFDM signal, the transfer function,

*H*(

_{OF}*f*), is Thus, considering Eq. (11) in Eqs. (9) and (10), results in From Eq. (12), it is clear that the SSMI term is cancelled completely. In the case of a non-ideal filter, typically having a finite frequency roll-off around its cut-off frequency, there are two impairments that can degrade the system performance. First, the optical carrier in the lower branch would not be removed completely which leads to a mixing product between the carrier and signal. Therefore, the signal power decreases by 1 −

*Ĥ*(

_{OF}*n*, 0) as shown in (12). Second, the band-edge OOFDM subcarriers are attenuated by the non-ideal optical filter. As such, the SSBI term in the upper and lower branches would not be identical; hence the SSBI cannot be removed completely. It is worth noting that the mitigation of SSMI relies heavily on the common mode rejection ratio of a balanced PD. Moreover, in practical systems, the insertion loss and delay caused by the optical filter in the lower branch should be compensated before the photocurrent from the upper and lower branches are subtracted. In general, two approaches can be applied to address these issues: (1) using a balanced PD and then these impairments are compensated in the optical domain; and (2) using two PDs instead of a balanced PD, where these impairments are compensated in the digital domain. With the former approach it is not easy to estimate and compensate the impairments whereas the latter approach is more practical and adaptive. However, two analog-to-digital converters are needed in the second approach while only one analog-to-digital converter is required in the first approach. We have chosen the second approach for the experiment because it is more practical.

## 4. Results and discussion

### 4.1. Simulation results

*W*

^{−1}

*km*

^{−1}, respectively. The noise figure of the EDFAs used to compensate the loss of each span is 6 dB. The optical filter is modeled with a super-Gaussian response,

*f*,

_{c}*B*, and

*M*are the center frequency, 3dB bandwidth, and filter order, respectively. In the simulations, the center frequency and 3dB bandwidth are fixed at

*Q*-factor for both the BICR with different optical filter orders

*M*and the conventional receiver by varying the GB. As depicted in the figure, as GB decreases, the number of OFDM subcarriers that suffer from SSMI increases and therefore the

*Q*-factor gets worse. It can be seen that the BICR outperforms the conventional receiver in terms of

*Q*-factor. This is because most SSMI is eliminated using the BICR and a better signal quality is achieved. Moreover, the

*Q*-factor improves by increasing the optical filter order at a fixed GB (i.e., the optical filter becomes more ideal thereby reducing the impairments associated with a non-ideal filter response). Additionally, for the fixed system performance, a higher-order optical filter is required to remove the optical carrier without affecting the OOFDM signal as the GB decreases. In other words, to further improve the SE for a given

*Q*-factor, a higher-order optical filter should be used. For instance, at a

*Q*-factor of 16 dB, the GB can be reduced to 3.7, 3, 2.3, 1.8, and 1.3 GHz using optical filters with orders of 2, 4, 6, 8, and 10, respectively.

*Q*-factor as a function of launch power with different optical filter orders and for GBs of 2 GHz and 3 GHz. As depicted in these figures, at a fixed optical filter order, the

*Q*-factor is maximized at the same optical launch power for the two different GBs. Also, at lower input powers, the

*Q*-factor is limited by ASE noise while for high launch powers, the

*Q*-factor is limited by fiber nonlinearity. Furthermore, the optimum

*Q*-factor increases by increasing either the optical filter order or the GB.

### 4.2. Experimental setup

^{−5}cannot be measured. As depicted in this figure, the experimental results are in good agreement with the numerical simulations. Moreover, since the SSMI is reduced using the BICR, the BICR outperforms the conventional receiver. The results show that using the second-order optical filter, the measured BER improvement varies from one to two orders of magnitude depending on the GB compared to the conventional receiver. An even greater improvement in BER can be obtained using a higher-order optical filter: the fourth-order optical filter improves the BER by about three orders of magnitude compared to the conventional receiver. In other words, for a given BER, a better SE can be achieved using a higher-order optical filter.

## 5. Conclusion

## Acknowledgments

## References and links

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

2. | Peter J. Winzer, “High-spectral-efficiency optical modulation formats,” IEEE J. Lightw. Technol. |

3. | J. Armstrong, “OFDM for optical communications,” IEEE J. Lightw. Technol. |

4. | 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,” IEEE J. Lightw. Technol. |

5. | W. Shieh, H. Bao, and Y. Tang, “Coherent optical OFDM: theory and design,” Opt. Express |

6. | W. Shieh, X. Yi, Y. Ma, and Q. Yang, “Coherent optical OFDM: has its time come?,” J. Optical Networking |

7. | Q. Zhuge, M. Morsy-Osman, M. E. Mousa-Pasandi, X. Xu, M. Chagnon, Z. A. El-Sahn, C. Chen, and D. V. Plant, “Single channel and WDM transmission of 28 Gbaud zero-guard-interval CO-OFDM,” Opt. Express |

8. | S. L. Jansen, I. Morita, and H. Tanaka, “10 × 121.9-Gb/s PDM-OFDM transmission with 2-b/s/Hz spectral efficiency over 1 000 km of SSMF,” in |

9. | T. Pollet, M. V. Blade, and M. Moeneclaey, “BER sensitivity of OFDM systems to carrier frequency offset and Wiener phase noise,”IEEE Tran. on Communiacation |

10. | X. Yi, W. Shieh, and Y. Ma, “Phase noise effects on high spectral efficiency coherent optical OFDM transmission,” IEEE J. Lightw. Technol. |

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

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

13. | I. V. Djordjevic and B. Vasic, “Orthogonal frequency division multiplexing for high-speed optical transmission,” Opt. Express |

14. | W. Peng, X. Wu, V. R. Arbab, B. Shamee, J. Yang, L. C. Christen, K. Feng, A. E. Willner, and S. Chi, “Experimental demonstration of 340 km SSMF transmission using a virtual single sideband OFDM signal that employs carrier suppressed and iterative detection techniques,” in |

15. | Z. Cao, J. Yu, W. Wang, L. Chen, and Z. Dong, “Direct-detection optical OFDM transmission system without frequency guard band,”IEEE Photon. Technol. Lett. |

16. | D. Qian, J. Yu, J. Hu, L. Zong, L. Xu, and T. Wang, “10 Gbit/s WDM-SSB-OFDM transmissions over 1000 km SSMF using conventional DFB lasers and direct-detection,” Electronic Letter |

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

18. | W. Peng, X. Wu, V. R. Arbab, B. Shamee, L.C. Christen, J. Yang, K. Feng, A. E. Willner, and S. Chi, “Experimental demonstration of a coherently modulated and directly detected optical OFDM system using an RF-tone insertion,” in |

19. | W. Peng, K. Feng, A. E. Willner, and S. Chi, “Estimation of the bit error rate for direct-detected OFDM signals with optically preamplified receivers,” IEEE J. Lightw. Technol. |

20. | G. Einarsson, |

**OCIS Codes**

(060.0060) Fiber optics and optical communications : Fiber optics and optical communications

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

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: May 1, 2013

Revised Manuscript: May 30, 2013

Manuscript Accepted: June 7, 2013

Published: June 18, 2013

**Citation**

S. Alireza Nezamalhosseini, Lawrence R. Chen, Qunbi Zhuge, Mahdi Malekiha, Farokh Marvasti, and David V. Plant, "Theoretical and experimental investigation of direct detection optical OFDM transmission using beat interference cancellation receiver," Opt. Express **21**, 15237-15246 (2013)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-13-15237

Sort: Year | Journal | Reset

### References

- N. Cvijetic, “OFDM for next-generation optical access networks,” IEEE J. Lightw. Technol.30(4), 384–398 (2012). [CrossRef]
- Peter J. Winzer, “High-spectral-efficiency optical modulation formats,” IEEE J. Lightw. Technol.30(24), 3824–3835 (2012). [CrossRef]
- J. Armstrong, “OFDM for optical communications,” IEEE J. Lightw. Technol.27(3), 189–204 (2009). [CrossRef]
- 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,” IEEE J. Lightw. Technol.26(1), 196–203 (2008). [CrossRef]
- W. Shieh, H. Bao, and Y. Tang, “Coherent optical OFDM: theory and design,” Opt. Express16(2), 841–859 (2008). [CrossRef] [PubMed]
- W. Shieh, X. Yi, Y. Ma, and Q. Yang, “Coherent optical OFDM: has its time come?,” J. Optical Networking7(3), 234–255 (2008). [CrossRef]
- Q. Zhuge, M. Morsy-Osman, M. E. Mousa-Pasandi, X. Xu, M. Chagnon, Z. A. El-Sahn, C. Chen, and D. V. Plant, “Single channel and WDM transmission of 28 Gbaud zero-guard-interval CO-OFDM,” Opt. Express20(26), 439–444 (2012). [CrossRef]
- S. L. Jansen, I. Morita, and H. Tanaka, “10 × 121.9-Gb/s PDM-OFDM transmission with 2-b/s/Hz spectral efficiency over 1 000 km of SSMF,” in Optical Fiber Communication Conference, OSA Technical Digest Series (CD) (Optical Society of America, 2007), paper PDP2.
- T. Pollet, M. V. Blade, and M. Moeneclaey, “BER sensitivity of OFDM systems to carrier frequency offset and Wiener phase noise,”IEEE Tran. on Communiacation43(2/3/4), 191–193 (1995). [CrossRef]
- X. Yi, W. Shieh, and Y. Ma, “Phase noise effects on high spectral efficiency coherent optical OFDM transmission,” IEEE J. Lightw. Technol.26(10), 1309–1316 (2008). [CrossRef]
- W. Peng, B. Zhang, K. Feng, X. Wu, A. E. Willner, and S. Chi, “Spectrally efficient direct-detected OFDM transmission incorporating a tunable frequency gap and an iterative detection techniques,” IEEE J. Lightw. Technol.27(24), 5723–5735 (2009). [CrossRef]
- A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express14(6), 2079–2084 (2006). [CrossRef] [PubMed]
- I. V. Djordjevic and B. Vasic, “Orthogonal frequency division multiplexing for high-speed optical transmission,” Opt. Express14(9), 3767–3775 (2006). [CrossRef] [PubMed]
- W. Peng, X. Wu, V. R. Arbab, B. Shamee, J. Yang, L. C. Christen, K. Feng, A. E. Willner, and S. Chi, “Experimental demonstration of 340 km SSMF transmission using a virtual single sideband OFDM signal that employs carrier suppressed and iterative detection techniques,” in Optical Fiber Communication Conference, OSA Technical Digest Series (CD) (Optical Society of America, 2008), paper OMU1.
- Z. Cao, J. Yu, W. Wang, L. Chen, and Z. Dong, “Direct-detection optical OFDM transmission system without frequency guard band,”IEEE Photon. Technol. Lett.22(11), 736–738 (2010). [CrossRef]
- D. Qian, J. Yu, J. Hu, L. Zong, L. Xu, and T. Wang, “10 Gbit/s WDM-SSB-OFDM transmissions over 1000 km SSMF using conventional DFB lasers and direct-detection,” Electronic Letter44(3), 223–225 (2008). [CrossRef]
- W. Peng, I. Morita, and H. Tanaka, “Enabling high capacity direct-detection optical OFDM transmissions using beat interference cancellation receiver,” in European Conference and Exhibition on Optical Communication(ECOC2010), paper Tu.4.A.2. [CrossRef]
- W. Peng, X. Wu, V. R. Arbab, B. Shamee, L.C. Christen, J. Yang, K. Feng, A. E. Willner, and S. Chi, “Experimental demonstration of a coherently modulated and directly detected optical OFDM system using an RF-tone insertion,” in Optical Fiber Communication Conference, OSA Technical Digest Series (CD) (Optical Society of America, 2008), paper OMU2.
- W. Peng, K. Feng, A. E. Willner, and S. Chi, “Estimation of the bit error rate for direct-detected OFDM signals with optically preamplified receivers,” IEEE J. Lightw. Technol.27(10), 1340–1346 (2009). [CrossRef]
- G. Einarsson, Principles of Lightwave Communications.New York: McGraw-Hill, 1996.

## Cited By |
Alert me when this paper is cited |

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article | Next Article »

OSA is a member of CrossRef.