Abstract

The multipath interference (MPI) noise is one of the most important limiting factors on the performance of the mobile fronthaul network (MFN) based on the radio-over-fiber (RoF) technology. Recently, it has been proposed to suppress this MPI noise by using the Gaussian phase dither. However, it broadens the optical spectrum significantly and, as a result, increases its vulnerability to the chromatic dispersion. To overcome this problem, we propose to suppress the MPI noise by using the RF-chirp dither instead of the Gaussian dither. The results show that, due to the narrow optical spectrum achieved by the RF-chirp dither, we can increase the transmission distance of the RoF-based MFN operating in the 1.5-µm region by three times.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

1. Introduction

The 5G realization requires the support of the reliable high-capacity mobile fronthaul networks (MFNs). Although the commercial 5G services have already been started, it appears that there are still many challenges on these MFNs for the future developments [1]. For example, various functional split options have been proposed to mitigate the enormous capacity requirement of the 5G MFNs [2]. However, these options can result in some drawbacks including the increased complexity and reduced coordination capability [3,4]. On the other hand, the radio-over-fiber (RoF) technology can provide an alternative solution to this capacity bottleneck problem. Thus, there have been many efforts to utilize the RoF technology for the development of the 5G MFNs [59]. Nevertheless, there is some skepticism about its commercial viability primarily due to the reliability issue inherent in the analog transmission systems [10]. For example, it has been reported that the performance of the RoF-based MFN can be affected by the dispersion-induced RF power fading, composite second-order (CSO) distortions, and multipath interference (MPI) noises [11,12]. However, we can avoid/mitigate the dispersion-induced problems (i.e., RF power fading and CSO distortions) by operating the system in the 1.3-µm region or using the simple digital signal processing techniques [13,14]. Thus, the remaining problem is the MPI noises caused by the bad fiber connectors. Recently, it has been reported that we can effectively suppress the MPI noises (caused by even multiple number of bad fiber connectors) by utilizing the Gaussian phase dither technique [15,16]. In this technique, the optical signal is phase-modulated by a filtered Gaussian dither signal operating at the frequency much higher than the signal’s bandwidth. As a result, the MPI noises are spread out to outside of the signal’s bandwidth. However, the optical spectrum is significantly broadened by the large modulation depth of the Gaussian dither signal, which, in turn, causes the system to be more vulnerable to the chromatic dispersion (CD).

In this paper, we propose to utilize the RF-chirp dither instead of the Gaussian dither for the suppression of the MPI noises in the RoF-based MFNs. There is no significant difference in the effectiveness of suppressing the MPI noises between these two techniques. However, when we utilize the RF-chirp dither, the system becomes more robust against CD due to its narrower optical spectrum and, consequently, we can increase the transmission distance of the RoF-based MFNs. For example, we experimentally demonstrate that, by using the RF-chirp dither instead of the Gaussian dither, it is possible to increase the maximum transmission distance of the RoF-based MFN operating in the 1.5-µm region by about three times.

2. Performance of RF-chirp dither

In the Gaussian phase dither technique, a Gaussian dither signal centered at a high frequency (fd) is used to spread the MPI noises over a large frequency span with a spectral interval of fd [15]. It has been reported that the phase modulation depth (δd) and bandwidth of the Gaussian dither signal should be >3 and >100 MHz, respectively, for the effective suppression of the MPI noises [15]. However, the use of such a large δd could broaden the optical spectrum significantly. As a result, in the case of using the Gaussian dither technique in the RoF-based MFN operating in the 1.5-µm region, the network’s performance could be seriously deteriorated by CD. To verify this, we estimate the spectral width of the phase-modulated (PM) optical signal from the peak amplitude of the Gaussian dither signal [17]. The results indicate that its high peak amplitude is responsible for the excessive broadening of the optical spectrum. Thus, we attempt to overcome this problem by modifying the dither waveform to have a constant amplitude. For this purpose, we propose to utilize the RF-chirp signal (which sweeps from an initial frequency to a target frequency with a constant amplitude,) as a dither waveform. In principle, the operating mechanism of the RF-chirp phase dither technique is no different from that of the Gaussian phase dither technique (i.e., both techniques spread out the MPI noises to outside of the signal’s bandwidth). Figure 1 shows the estimated optical spectra of the PM signals obtained by using an RF-chirp dither and a Gaussian dither. In this numerical estimation, we assume that the RF-chirp dither is centered at 12.5 GHz and its frequency is swept from 12.45 GHz to 12.55 GHz within 17.8 µs (which is equivalent to one OFDM symbol duration used in this work). On the other hand, the center frequency and bandwidth of the Gaussian dither are assumed to be 12.5 GHz and 100 MHz, respectively. In both cases, we set δd to be 3.5 and the root-mean square amplitude of the dither signal to be 1. The results show that the spectral width of the PM optical signal obtained by the RF-chirp dither is much narrower than that obtained by the Gaussian dither. Thus, it is expected that the performance of the RoF-based MFN would be less affected by CD in the case of using the RF-chirp dither (instead of the Gaussian dither).

 

Fig. 1. Estimated optical spectra of the PM signals obtained by using the (a) RF-chirp dither and (b) Gaussian dither (centered at 12.5 GHz and having a bandwidth of 100 MHz). δd is set to be 3.5 in both cases.

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We first evaluate the effectiveness of the proposed RF-chirp dither for the suppression of the MPI noises in the RoF-based MFN by numerical simulations. For this purpose, we estimate the EVM performance of the 64-QAM OFDM signal (which is centered at 500 MHz and having a bandwidth of 100 MHz) in the presence of the MPI noises. In this evaluation, we assume that the MPI noises are caused by an interferer having a time delay of 5 ns (which corresponds to a path difference of 1 m for the interferer signal) [15]. In addition, we assume that the signal-to-interference ratio (SIR), fd, and δd are 20 dB, 12.5 GHz and 3.5, respectively. Figure 2 shows the EVM performances of the 100-MHz OFDM channel achieved by using the proposed RF-chirp dither with various bandwidths. From the results in this figure, we confirm that the effectiveness of the RF-chirp dither on the suppression of the MPI noises is independent of the dither bandwidth as long as it is larger than ∼100 MHz (which is identical to the case of using the Gaussian dither [15]). Thus, we set the sweeping range and sweeping time of the RF-chirp signal to be 100 MHz and 17.8 µs, respectively. We also note that such an RF-chirp signal can be easily generated by using a simple commercial synthesizer chip [18].

 

Fig. 2. Estimated EVM performances of the 100-MHz OFDM channel (@ 500 MHz) achieved by using the proposed RF-chirp dither with various bandwidths in the back-to-back condition. The horizontal axis indicates the deviation of the dither frequency from 12.5 GHz.

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We also evaluate the EVM performances of the six 100-MHz OFDM channels placed at {500 + (i-1)×1000} MHz, where i is the channel index. We intentionally set the channel spacing to be as large as 1 GHz to observe the effects of CD at the high-frequency channels. The RF spectrum of these OFDM channels is shown in the inset of Fig. 3. We assume that these OFDM channels are transported in the RoF-based MFN in the presence of the MPI noises caused by an interferer having a time delay of 2.5 µs. To show the effectiveness of the proposed RF-chirp dither on the suppression of the MPI noises, we estimate the EVM performances of channels 1 and 6 (i.e., the lowest- and highest-frequency channels) in the back-to-back condition with and without applying the proposed RF-chirp dither. In this numerical estimation, we assume that the RF-chirp dither is centered at 12.5 GHz (which is higher than two times of the highest-frequency component of the OFDM channels) and its bandwidth and δd are 100 MHz and 3.5, respectively. The sweep time for this RF-chirp dither (T) is set to be same with the duration of the OFDM symbol. For a comparison, we repeat this EVM estimation by using a 100-MHz Gaussian dither centered at 12.5 GHz. Figure 3 shows that there is no significant difference in the effectiveness of suppressing the MPI noises between the RF-chirp dither and Gaussian dither. For example, the EVM values of the OFDM channel 6 obtained by using the RF-chirp dither are almost identical to those obtained by using the Gaussian dither. However, in the case of the OFDM channel 1, it seems that the RF-chirp dither outperforms the Gaussian dither. For example, by using the RF-chirp dither, it is possible to satisfy the EVM requirement of the 64 QAM signal for the OFDM channel 1 even when the SIR is as low as 15 dB [19]. In comparison, in the case of using the Gaussian dither, the similar performance can be achieved only when the SIR is higher than 20 dB. This is because the performance of the low-frequency channel is affected by the significantly broadened linewidth of the optical signal (due to the Gaussian dither). Thus, if necessary, we can avoid this problem simply by operating the lowest-frequency channel at a slightly higher frequency.

 

Fig. 3. Estimated EVM performances of OFDM channels 1 and 6 in the presence of the MPI noises achieved by using the RF-chirp dither, Gaussian dither, and no dither in the back-to-back condition (i.e., no effect of CD).

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The phase dithering technique used for the suppression of the MPI noises could increase the CD-induced performance degradation and limit the maximum transmission distance since it inevitably broadens the optical spectrum. However, we expect that this effect is less severe for the proposed RF-chirp dither than the Gaussian dither due to its narrow spectrum. To verify this, we estimate the EVM performances of six 100-MHz OFDM channels as a function of the transmission distance (assuming that the SIR is 32 dB). For example, Fig. 4 compares the EVM performances of channels 1 and 6 achieved by using the RF-chirp dither and Gaussian dither. As expected, the high-frequency channel (i.e., channel 6 at 5.5 GHz) suffers from CD much more seriously than the low-frequency channel (i.e., channel 1 at 0.5 GHz). We also find that, in the case of using the RF-chirp dither, it is possible to satisfy the 8% EVM requirement of the 64QAM signal for all six OFDM channels even after the transmission over 4.2 km of SMF. In comparison, this distance is limited to be 1.4 km in the case of using the Gaussian dither.

 

Fig. 4. Estimated EVM performances of OFDM channels 1 and 6 as a function of the transmission distance achieved by using the RF-chirp dither, Gaussian dither, and no dither. In this numerical estimation, CD, fd, and δd are assumed to be 17 ps/km/nm, 12.5 GHz, and 3.5, respectively.

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3. Experiment and results

Figure 5 shows the experimental setup where we generated six 100-MHz OFDM channels, in the range of 0.5 ∼ 5.5 GHz, by using an arbitrary waveform generator (AWG). The output of this AWG was directed to an EML operating at 1539 nm. The output power and linewidth of this EML were measured to be 2 dBm and 4 MHz, respectively. The nonlinearity of this EML was compensated by applying an adaptive equalization technique at the receiver [20]. We sent the output of this EML to a LiNbO3 phase modulator (3-dB bandwidth: 20 GHz), which was driven by the dither signal (either RF-chirp or Gaussian dither) centered at 12.5 GHz and having a bandwidth of 100 MHz. In both cases, δd was set to be 3.5. On the other hand, the RF-chirp signal was set to be increasing from 12.45 GHz to 12.55 GHz. We amplified the output of the phase modulator (i.e., six OFDM signals and a dither signal) by using an erbium-doped fiber amplifier (EDFA) and transmitted it over 0 ∼ 5 km of the standard single-mode fiber (SSMF). The transmitted signal was then passed through the interferometry setup (used to emulate the MPI noises), which was consisted of a variable optical attenuator (VOA) and a 1.3-km long SSMF. A polarization controller (PC) was used to maximize the interference in this interferer. We detected the transmitted signal by using a PIN photodetector having a 3-dB bandwidth of 10 GHz. The detected signal was sampled at 40 GS/s by using a digital storage oscilloscope (DSO), and then processed offline for the EVM analysis.

 

Fig. 5. Experimental setup. We emulate the MPI noises by using the interferer setup shown in the dotted box (where we split the signal into two paths and recombined them after a certain delay).

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Figure 6 shows the measured optical spectra of the PM signal obtained by using the RF-chirp and Gaussian dither techniques. The results agreed well with the numerically obtained spectra shown in Fig. 1. The optical spectrum obtained by using the RF-chirp dither was measured to be about 30% narrower than that obtained by the Gaussian dither. Figure 7 shows the measured EVM performances of OFDM channels 1 and 6 in the back-to-back condition as a function of the SIR. The measured data shown in this figure also agreed well with the numerical results in Fig. 3. We confirmed that the EVM performance was not dependent on the path difference as long as it was longer than 100 m (as in the case of using the Gaussian dither [15]). Figure 8 shows the measured EVM performances as a function of the transmission distance. The SIR was set to be 32 dB in this measurement. In the case of using the RF-chirp dither, we could satisfy the EVM requirement of the 64QAM signal (i.e., 8%) even after the transmission over ∼4.0 km of SSMF (which agreed well with the numerically estimated value of 4.2 km). In comparison, in the case of using the Gaussian dither, the maximum transmission distance was limited to ∼1.6 km (which also agreed well with the numerical value of 1.4 km). Figure 9 shows the measured electrical spectra of the received signals (i.e., 6 channels of 100-MHz 64-QAM OFDM signals) obtained by using the RF-chirp dither and Gaussian dither techniques. From the results shown in this figure, we confirmed that the low-frequency channel was less affected by the broadened linewidth in the case of using the RF-chirp dither (instead of the Gaussian dither). The results also showed that, as expected, the high-frequency channels suffered more from CD than the low-frequency channels due to the effects of the nonlinear distortions and power fading. In particular, the high-frequency channels suffered more from nonlinear distortions in the case of using the Gaussian dither, while the effects of the power fading appeared to be almost the same in both cases.

 

Fig. 6. Measured optical spectra of the PM signals obtained by using the (a) RF-chirp dither and (b) Gaussian dither (centered at 12.5 GHz and having a bandwidth of 100 MHz). δd is set to be 3.5 in both cases. The optical spectra were measured at the input of SSMF.

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Fig. 7. Measured EVM performances of OFDM channels 1 and 6 as a function of the SIR in the back-to-back condition by using the RF-chirp dither, Gaussian dither, and no dither.

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Fig. 8. Measured EVM performances of OFDM channels 1 and 6 as a function of the transmission distance by using the RF-chirp dither and Gaussian dither.

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Fig. 9. Measured electrical spectra of the received signals (i.e., 6 channels of 100-MHz OFDM signals) by using the (a) RF-chirp dither and (b) Gaussian dither techniques.

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4. Summary

We have proposed to utilize the RF-chirp dither for the suppression of the MPI noises in the RoF-based MFNs. There is no significant difference in the effectiveness on the suppression of the MPI noises between this technique and the previously proposed Gaussian dither technique. However, by using the proposed RF-chirp dither, we can mitigate the effects of CD and increase the maximum transmission distance due to its narrower optical spectrum. We evaluated the performances of the RF-chirp dither in the RoF-based MFN implemented with six 100-MHz OFDM channels (operating at 0.5 ∼ 5.5 GHz) both numerically and experimentally. The results showed that, by using the proposed RF-chirp dither instead of the Gaussian dither, we could increase the transmission distance of this MFN by about three times (from ∼1.4 km to ∼4.2 km).

Funding

Institute for Information and Communications Technology Promotion (2017-0-00702).

Disclosures

The authors declare that there are no conflicts of interest related to this article.

References

1. I. Chih-Lin, H. Li, J. Korhonen, J. Huang, and L. Han, “RAN revolution with NGFI (xHaul) for 5G,” J. Lightwave Technol. 36(2), 541–550 (2018). [CrossRef]  

2. K. Miyamoto, S. Kuwano, J. Terada, and A. Otaka, “Analysis of mobile fronthaul bandwidth and wireless transmission performance in split-PHY processing architecture,” Opt. Express 24(2), 1261–1268 (2016). [CrossRef]  

3. N. J. Gomes, P. Chanclou, and P. Assimakopoulos, “Boosting 5G through Ethernet: How evolved fronthaul can take next-generation mobile to the next level,” IEEE Veh. Technol. Mag. 13(1), 74–84 (2018). [CrossRef]  

4. A. Marotta, D. Cassioli, K. Kondepu, C. Antonelli, and L. Valcarenghi, “Exploiting flexible functional split in converged software defined access networks,” J. Opt. Commun. Netw. 11(11), 536–546 (2019). [CrossRef]  

5. X. Liu, H. Zeng, N. Chand, and F. Effenberger, “Bandwidth-efficient mobile fronthaul transmission for future 5G wireless networks,” in Proc. ACP, Hong Kong, 2015, Paper ASu3E.4.

6. B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “Optical fronthaul technologies for next-generation mobile communications,” in Proc. ICTON, Trento, Italy, 2016, Paper We.D2.5

7. F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017). [CrossRef]  

8. S. Ishimura, A. Bekkali, K. Tanaka, K. Nishimura, and M. Suzuki, “1.032- Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links,” J. Lightwave Technol. 36(8), 1478–1484 (2018). [CrossRef]  

9. B. G. Kim, S. H. Bae, and Y. C. Chung, “RoF-based mobile fronthaul networks implemented by using DML and EML for 5G wireless communication systems,” J. Lightwave Technol. 36(14), 2874–2881 (2018). [CrossRef]  

10. B. G. Kim and Y. C. Chung, “Highly reliable RoF-based mobile fronthaul network 5G wireless communication systems,” in Proc. ACP, Chengdu, China, 2019, Paper S4E.4.

11. R. Chen, X. Zheng, and H. Zhang, “RF signal fluctuation induced by optical multipath interference in analog fiber system,” IEEE Photonics Technol. Lett. 18(7), 808–810 (2006). [CrossRef]  

12. B. G. Kim, H. Kim, and Y. C. Chung, “Impact of multipath interference on the performance of RoF-based mobile fronthaul network implemented by using DML,” J. Lightwave Technol. 35(2), 145–151 (2017). [CrossRef]  

13. M. Sung, S.-H. Cho, H. S. Chung, S. M. Kim, and J. H. Lee, “Investigation of transmission performance in multi-IFoF based mobile fronthaul with dispersion-induced intermixing noise mitigation,” Opt. Express 25(8), 9346–9357 (2017). [CrossRef]  

14. B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “DSP-based CSO cancellation technique for RoF transmission system implemented by using directly modulated laser,” Opt. Express 25(11), 12152–12160 (2017). [CrossRef]  

15. B. G. Kim, S. H. Bae, M. S. Kim, and Y. C. Chung, “Reflection-tolerant RoF-based mobile fronthaul network for 5G wireless systems,” J. Lightwave Technol. 37(24), 6105–6113 (2019). [CrossRef]  

16. B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

17. B. P. Lathi and Z. Ding, “Angle Modulation and Demodulation,” in Modern Digital and Analog Communication Systems, Oxford University Press, 4th Edition, 2009, pp. 211–215.

18. D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018). [CrossRef]  

19. . “Base station (BS) radio transmission and reception,” 3GPP TS 38.104 version 15.5.0, 2019.

20. B. G. Kim, S. H. Bae, and Y. C. Chung, “Blind compensation technique for nonlinear distortions in RoF-based mobile fronthaul implemented by using EML,” Opt. Fiber Technol. 47, 51–54 (2019). [CrossRef]  

References

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  1. I. Chih-Lin, H. Li, J. Korhonen, J. Huang, and L. Han, “RAN revolution with NGFI (xHaul) for 5G,” J. Lightwave Technol. 36(2), 541–550 (2018).
    [Crossref]
  2. K. Miyamoto, S. Kuwano, J. Terada, and A. Otaka, “Analysis of mobile fronthaul bandwidth and wireless transmission performance in split-PHY processing architecture,” Opt. Express 24(2), 1261–1268 (2016).
    [Crossref]
  3. N. J. Gomes, P. Chanclou, and P. Assimakopoulos, “Boosting 5G through Ethernet: How evolved fronthaul can take next-generation mobile to the next level,” IEEE Veh. Technol. Mag. 13(1), 74–84 (2018).
    [Crossref]
  4. A. Marotta, D. Cassioli, K. Kondepu, C. Antonelli, and L. Valcarenghi, “Exploiting flexible functional split in converged software defined access networks,” J. Opt. Commun. Netw. 11(11), 536–546 (2019).
    [Crossref]
  5. X. Liu, H. Zeng, N. Chand, and F. Effenberger, “Bandwidth-efficient mobile fronthaul transmission for future 5G wireless networks,” in Proc. ACP, Hong Kong, 2015, Paper ASu3E.4.
  6. B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “Optical fronthaul technologies for next-generation mobile communications,” in Proc. ICTON, Trento, Italy, 2016, Paper We.D2.5
  7. F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
    [Crossref]
  8. S. Ishimura, A. Bekkali, K. Tanaka, K. Nishimura, and M. Suzuki, “1.032- Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links,” J. Lightwave Technol. 36(8), 1478–1484 (2018).
    [Crossref]
  9. B. G. Kim, S. H. Bae, and Y. C. Chung, “RoF-based mobile fronthaul networks implemented by using DML and EML for 5G wireless communication systems,” J. Lightwave Technol. 36(14), 2874–2881 (2018).
    [Crossref]
  10. B. G. Kim and Y. C. Chung, “Highly reliable RoF-based mobile fronthaul network 5G wireless communication systems,” in Proc. ACP, Chengdu, China, 2019, Paper S4E.4.
  11. R. Chen, X. Zheng, and H. Zhang, “RF signal fluctuation induced by optical multipath interference in analog fiber system,” IEEE Photonics Technol. Lett. 18(7), 808–810 (2006).
    [Crossref]
  12. B. G. Kim, H. Kim, and Y. C. Chung, “Impact of multipath interference on the performance of RoF-based mobile fronthaul network implemented by using DML,” J. Lightwave Technol. 35(2), 145–151 (2017).
    [Crossref]
  13. M. Sung, S.-H. Cho, H. S. Chung, S. M. Kim, and J. H. Lee, “Investigation of transmission performance in multi-IFoF based mobile fronthaul with dispersion-induced intermixing noise mitigation,” Opt. Express 25(8), 9346–9357 (2017).
    [Crossref]
  14. B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “DSP-based CSO cancellation technique for RoF transmission system implemented by using directly modulated laser,” Opt. Express 25(11), 12152–12160 (2017).
    [Crossref]
  15. B. G. Kim, S. H. Bae, M. S. Kim, and Y. C. Chung, “Reflection-tolerant RoF-based mobile fronthaul network for 5G wireless systems,” J. Lightwave Technol. 37(24), 6105–6113 (2019).
    [Crossref]
  16. B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.
  17. B. P. Lathi and Z. Ding, “Angle Modulation and Demodulation,” in Modern Digital and Analog Communication Systems, Oxford University Press, 4th Edition, 2009, pp. 211–215.
  18. D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
    [Crossref]
  19. . “Base station (BS) radio transmission and reception,” 3GPP TS 38.104 version 15.5.0, 2019.
  20. B. G. Kim, S. H. Bae, and Y. C. Chung, “Blind compensation technique for nonlinear distortions in RoF-based mobile fronthaul implemented by using EML,” Opt. Fiber Technol. 47, 51–54 (2019).
    [Crossref]

2019 (3)

2018 (5)

N. J. Gomes, P. Chanclou, and P. Assimakopoulos, “Boosting 5G through Ethernet: How evolved fronthaul can take next-generation mobile to the next level,” IEEE Veh. Technol. Mag. 13(1), 74–84 (2018).
[Crossref]

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

I. Chih-Lin, H. Li, J. Korhonen, J. Huang, and L. Han, “RAN revolution with NGFI (xHaul) for 5G,” J. Lightwave Technol. 36(2), 541–550 (2018).
[Crossref]

S. Ishimura, A. Bekkali, K. Tanaka, K. Nishimura, and M. Suzuki, “1.032- Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links,” J. Lightwave Technol. 36(8), 1478–1484 (2018).
[Crossref]

B. G. Kim, S. H. Bae, and Y. C. Chung, “RoF-based mobile fronthaul networks implemented by using DML and EML for 5G wireless communication systems,” J. Lightwave Technol. 36(14), 2874–2881 (2018).
[Crossref]

2017 (4)

2016 (1)

2006 (1)

R. Chen, X. Zheng, and H. Zhang, “RF signal fluctuation induced by optical multipath interference in analog fiber system,” IEEE Photonics Technol. Lett. 18(7), 808–810 (2006).
[Crossref]

Antonelli, C.

Assimakopoulos, P.

N. J. Gomes, P. Chanclou, and P. Assimakopoulos, “Boosting 5G through Ethernet: How evolved fronthaul can take next-generation mobile to the next level,” IEEE Veh. Technol. Mag. 13(1), 74–84 (2018).
[Crossref]

Bae, S. H.

B. G. Kim, S. H. Bae, M. S. Kim, and Y. C. Chung, “Reflection-tolerant RoF-based mobile fronthaul network for 5G wireless systems,” J. Lightwave Technol. 37(24), 6105–6113 (2019).
[Crossref]

B. G. Kim, S. H. Bae, and Y. C. Chung, “Blind compensation technique for nonlinear distortions in RoF-based mobile fronthaul implemented by using EML,” Opt. Fiber Technol. 47, 51–54 (2019).
[Crossref]

B. G. Kim, S. H. Bae, and Y. C. Chung, “RoF-based mobile fronthaul networks implemented by using DML and EML for 5G wireless communication systems,” J. Lightwave Technol. 36(14), 2874–2881 (2018).
[Crossref]

B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “DSP-based CSO cancellation technique for RoF transmission system implemented by using directly modulated laser,” Opt. Express 25(11), 12152–12160 (2017).
[Crossref]

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “Optical fronthaul technologies for next-generation mobile communications,” in Proc. ICTON, Trento, Italy, 2016, Paper We.D2.5

Bekkali, A.

Bertulessi, L.

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

Cassioli, D.

Chanclou, P.

N. J. Gomes, P. Chanclou, and P. Assimakopoulos, “Boosting 5G through Ethernet: How evolved fronthaul can take next-generation mobile to the next level,” IEEE Veh. Technol. Mag. 13(1), 74–84 (2018).
[Crossref]

Chand, N.

X. Liu, H. Zeng, N. Chand, and F. Effenberger, “Bandwidth-efficient mobile fronthaul transmission for future 5G wireless networks,” in Proc. ACP, Hong Kong, 2015, Paper ASu3E.4.

Chang, G. K.

F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
[Crossref]

Chen, R.

R. Chen, X. Zheng, and H. Zhang, “RF signal fluctuation induced by optical multipath interference in analog fiber system,” IEEE Photonics Technol. Lett. 18(7), 808–810 (2006).
[Crossref]

Cherniak, D.

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

Chih-Lin, I.

Cho, S.-H.

Chung, H. S.

Chung, Y. C.

B. G. Kim, S. H. Bae, M. S. Kim, and Y. C. Chung, “Reflection-tolerant RoF-based mobile fronthaul network for 5G wireless systems,” J. Lightwave Technol. 37(24), 6105–6113 (2019).
[Crossref]

B. G. Kim, S. H. Bae, and Y. C. Chung, “Blind compensation technique for nonlinear distortions in RoF-based mobile fronthaul implemented by using EML,” Opt. Fiber Technol. 47, 51–54 (2019).
[Crossref]

B. G. Kim, S. H. Bae, and Y. C. Chung, “RoF-based mobile fronthaul networks implemented by using DML and EML for 5G wireless communication systems,” J. Lightwave Technol. 36(14), 2874–2881 (2018).
[Crossref]

B. G. Kim, H. Kim, and Y. C. Chung, “Impact of multipath interference on the performance of RoF-based mobile fronthaul network implemented by using DML,” J. Lightwave Technol. 35(2), 145–151 (2017).
[Crossref]

B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “DSP-based CSO cancellation technique for RoF transmission system implemented by using directly modulated laser,” Opt. Express 25(11), 12152–12160 (2017).
[Crossref]

B. G. Kim and Y. C. Chung, “Highly reliable RoF-based mobile fronthaul network 5G wireless communication systems,” in Proc. ACP, Chengdu, China, 2019, Paper S4E.4.

B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “Optical fronthaul technologies for next-generation mobile communications,” in Proc. ICTON, Trento, Italy, 2016, Paper We.D2.5

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

Ding, Z.

B. P. Lathi and Z. Ding, “Angle Modulation and Demodulation,” in Modern Digital and Analog Communication Systems, Oxford University Press, 4th Edition, 2009, pp. 211–215.

Effenberger, F.

X. Liu, H. Zeng, N. Chand, and F. Effenberger, “Bandwidth-efficient mobile fronthaul transmission for future 5G wireless networks,” in Proc. ACP, Hong Kong, 2015, Paper ASu3E.4.

Gomes, N. J.

N. J. Gomes, P. Chanclou, and P. Assimakopoulos, “Boosting 5G through Ethernet: How evolved fronthaul can take next-generation mobile to the next level,” IEEE Veh. Technol. Mag. 13(1), 74–84 (2018).
[Crossref]

Grimaldi, L.

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

Han, L.

Huang, J.

Ishimura, S.

S. Ishimura, A. Bekkali, K. Tanaka, K. Nishimura, and M. Suzuki, “1.032- Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links,” J. Lightwave Technol. 36(8), 1478–1484 (2018).
[Crossref]

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

Kim, B. G.

B. G. Kim, S. H. Bae, M. S. Kim, and Y. C. Chung, “Reflection-tolerant RoF-based mobile fronthaul network for 5G wireless systems,” J. Lightwave Technol. 37(24), 6105–6113 (2019).
[Crossref]

B. G. Kim, S. H. Bae, and Y. C. Chung, “Blind compensation technique for nonlinear distortions in RoF-based mobile fronthaul implemented by using EML,” Opt. Fiber Technol. 47, 51–54 (2019).
[Crossref]

B. G. Kim, S. H. Bae, and Y. C. Chung, “RoF-based mobile fronthaul networks implemented by using DML and EML for 5G wireless communication systems,” J. Lightwave Technol. 36(14), 2874–2881 (2018).
[Crossref]

B. G. Kim, H. Kim, and Y. C. Chung, “Impact of multipath interference on the performance of RoF-based mobile fronthaul network implemented by using DML,” J. Lightwave Technol. 35(2), 145–151 (2017).
[Crossref]

B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “DSP-based CSO cancellation technique for RoF transmission system implemented by using directly modulated laser,” Opt. Express 25(11), 12152–12160 (2017).
[Crossref]

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

B. G. Kim and Y. C. Chung, “Highly reliable RoF-based mobile fronthaul network 5G wireless communication systems,” in Proc. ACP, Chengdu, China, 2019, Paper S4E.4.

B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “Optical fronthaul technologies for next-generation mobile communications,” in Proc. ICTON, Trento, Italy, 2016, Paper We.D2.5

Kim, H.

Kim, M. S.

B. G. Kim, S. H. Bae, M. S. Kim, and Y. C. Chung, “Reflection-tolerant RoF-based mobile fronthaul network for 5G wireless systems,” J. Lightwave Technol. 37(24), 6105–6113 (2019).
[Crossref]

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

Kim, S. M.

Kondepu, K.

Korhonen, J.

Kuwano, S.

Lathi, B. P.

B. P. Lathi and Z. Ding, “Angle Modulation and Demodulation,” in Modern Digital and Analog Communication Systems, Oxford University Press, 4th Edition, 2009, pp. 211–215.

Lee, J. H.

Levantino, S.

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

Li, H.

Liu, X.

X. Liu, H. Zeng, N. Chand, and F. Effenberger, “Bandwidth-efficient mobile fronthaul transmission for future 5G wireless networks,” in Proc. ACP, Hong Kong, 2015, Paper ASu3E.4.

Lu, F.

F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
[Crossref]

Marotta, A.

Miyamoto, K.

Nishimura, K.

S. Ishimura, A. Bekkali, K. Tanaka, K. Nishimura, and M. Suzuki, “1.032- Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links,” J. Lightwave Technol. 36(8), 1478–1484 (2018).
[Crossref]

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

Nonis, R.

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

Otaka, A.

Samori, C.

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

Shen, S.

F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
[Crossref]

Sung, M.

Suzuki, M.

S. Ishimura, A. Bekkali, K. Tanaka, K. Nishimura, and M. Suzuki, “1.032- Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links,” J. Lightwave Technol. 36(8), 1478–1484 (2018).
[Crossref]

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

Tanaka, K.

S. Ishimura, A. Bekkali, K. Tanaka, K. Nishimura, and M. Suzuki, “1.032- Tb/s CPRI-equivalent rate IF-over-fiber transmission using a parallel IM/PM transmitter for high-capacity mobile fronthaul links,” J. Lightwave Technol. 36(8), 1478–1484 (2018).
[Crossref]

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

Terada, J.

Valcarenghi, L.

Wang, J.

F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
[Crossref]

Xu, M.

F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
[Crossref]

Zeng, H.

X. Liu, H. Zeng, N. Chand, and F. Effenberger, “Bandwidth-efficient mobile fronthaul transmission for future 5G wireless networks,” in Proc. ACP, Hong Kong, 2015, Paper ASu3E.4.

Zhang, H.

R. Chen, X. Zheng, and H. Zhang, “RF signal fluctuation induced by optical multipath interference in analog fiber system,” IEEE Photonics Technol. Lett. 18(7), 808–810 (2006).
[Crossref]

Zhang, J.

F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
[Crossref]

Zheng, X.

R. Chen, X. Zheng, and H. Zhang, “RF signal fluctuation induced by optical multipath interference in analog fiber system,” IEEE Photonics Technol. Lett. 18(7), 808–810 (2006).
[Crossref]

IEEE J. Solid-State Circuits (1)

D. Cherniak, L. Grimaldi, L. Bertulessi, R. Nonis, C. Samori, and S. Levantino, “A 23-GHz low-phase-noise digital bang-bang PLL for fast triangular and sawtooth chirp modulation,” IEEE J. Solid-State Circuits 53(12), 3565–3575 (2018).
[Crossref]

IEEE Photonics Technol. Lett. (2)

F. Lu, M. Xu, J. Wang, S. Shen, J. Zhang, and G. K. Chang, “Sub-band pre-distortion for PAPR reduction in spectral efficient 5G mobile fronthaul,” IEEE Photonics Technol. Lett. 29(1), 122–125 (2017).
[Crossref]

R. Chen, X. Zheng, and H. Zhang, “RF signal fluctuation induced by optical multipath interference in analog fiber system,” IEEE Photonics Technol. Lett. 18(7), 808–810 (2006).
[Crossref]

IEEE Veh. Technol. Mag. (1)

N. J. Gomes, P. Chanclou, and P. Assimakopoulos, “Boosting 5G through Ethernet: How evolved fronthaul can take next-generation mobile to the next level,” IEEE Veh. Technol. Mag. 13(1), 74–84 (2018).
[Crossref]

J. Lightwave Technol. (5)

J. Opt. Commun. Netw. (1)

Opt. Express (3)

Opt. Fiber Technol. (1)

B. G. Kim, S. H. Bae, and Y. C. Chung, “Blind compensation technique for nonlinear distortions in RoF-based mobile fronthaul implemented by using EML,” Opt. Fiber Technol. 47, 51–54 (2019).
[Crossref]

Other (6)

. “Base station (BS) radio transmission and reception,” 3GPP TS 38.104 version 15.5.0, 2019.

B. G. Kim, S. H. Bae, M. S. Kim, S. Ishimura, K. Tanaka, K. Nishimura, M. Suzuki, and Y. C. Chung, “Demonstration of reflection-tolerant RoF-based mobile fronthaul network for 5G wireless system,” in Proc. ECOC, Dublin, Ireland, 2019, Paper M.1.C.1.

B. P. Lathi and Z. Ding, “Angle Modulation and Demodulation,” in Modern Digital and Analog Communication Systems, Oxford University Press, 4th Edition, 2009, pp. 211–215.

X. Liu, H. Zeng, N. Chand, and F. Effenberger, “Bandwidth-efficient mobile fronthaul transmission for future 5G wireless networks,” in Proc. ACP, Hong Kong, 2015, Paper ASu3E.4.

B. G. Kim, S. H. Bae, H. Kim, and Y. C. Chung, “Optical fronthaul technologies for next-generation mobile communications,” in Proc. ICTON, Trento, Italy, 2016, Paper We.D2.5

B. G. Kim and Y. C. Chung, “Highly reliable RoF-based mobile fronthaul network 5G wireless communication systems,” in Proc. ACP, Chengdu, China, 2019, Paper S4E.4.

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Figures (9)

Fig. 1.
Fig. 1. Estimated optical spectra of the PM signals obtained by using the (a) RF-chirp dither and (b) Gaussian dither (centered at 12.5 GHz and having a bandwidth of 100 MHz). δd is set to be 3.5 in both cases.
Fig. 2.
Fig. 2. Estimated EVM performances of the 100-MHz OFDM channel (@ 500 MHz) achieved by using the proposed RF-chirp dither with various bandwidths in the back-to-back condition. The horizontal axis indicates the deviation of the dither frequency from 12.5 GHz.
Fig. 3.
Fig. 3. Estimated EVM performances of OFDM channels 1 and 6 in the presence of the MPI noises achieved by using the RF-chirp dither, Gaussian dither, and no dither in the back-to-back condition (i.e., no effect of CD).
Fig. 4.
Fig. 4. Estimated EVM performances of OFDM channels 1 and 6 as a function of the transmission distance achieved by using the RF-chirp dither, Gaussian dither, and no dither. In this numerical estimation, CD, fd, and δd are assumed to be 17 ps/km/nm, 12.5 GHz, and 3.5, respectively.
Fig. 5.
Fig. 5. Experimental setup. We emulate the MPI noises by using the interferer setup shown in the dotted box (where we split the signal into two paths and recombined them after a certain delay).
Fig. 6.
Fig. 6. Measured optical spectra of the PM signals obtained by using the (a) RF-chirp dither and (b) Gaussian dither (centered at 12.5 GHz and having a bandwidth of 100 MHz). δd is set to be 3.5 in both cases. The optical spectra were measured at the input of SSMF.
Fig. 7.
Fig. 7. Measured EVM performances of OFDM channels 1 and 6 as a function of the SIR in the back-to-back condition by using the RF-chirp dither, Gaussian dither, and no dither.
Fig. 8.
Fig. 8. Measured EVM performances of OFDM channels 1 and 6 as a function of the transmission distance by using the RF-chirp dither and Gaussian dither.
Fig. 9.
Fig. 9. Measured electrical spectra of the received signals (i.e., 6 channels of 100-MHz OFDM signals) by using the (a) RF-chirp dither and (b) Gaussian dither techniques.

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