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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 10 — May. 9, 2011
  • pp: 9575–9581
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Hybrid CATV/16-QAM OFDM in-building networks over SMF and GI-POF transport

Hsiao-Chun Peng, Heng-Sheng Su, Hai-Han Lu, Chung-Yi Li, Peng-Chun Peng, Shang-Hua Wu, and Ching-Hung Chang  »View Author Affiliations


Optics Express, Vol. 19, Issue 10, pp. 9575-9581 (2011)
http://dx.doi.org/10.1364/OE.19.009575


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Abstract

A hybrid CATV/16-QAM OFDM in-building network over a combination of single-mode fiber (SMF) and graded-index plastic optical fiber (GI-POF) transport is proposed and experimentally demonstrated with good qualities of service. In this system, a 1556 nm optical signal is directly transmitted along with two fiber spans (20-km SMF + 25-m GI-POF). Without using any wavelength conversion or bridge circuit between SMF and POF connection, error free transmissions with sufficient low bit error rate (BER) values are achieved for 2.5Gbps/2.5GHz and 5Gbps/2.5GHz OFDM signals; as well as good performances of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) are obtained for CATV one. This proposed network reveals an outstanding one with economy and convenience to be installed.

© 2011 OSA

1. Introduction

2. Experimental setup

And then, the optical signal is transmitted through two fiber spans: 20 km SMF (with an attenuation of 0.24 dB/km and a dispersion coefficient of 17ps/nm⋅km) and 25-m GI-POF (Chromis Fiberoptics GigaPOF50SR-PC-SM, with core diameter = 50 ± 5μm, numerical aperture = 0.185 ± 0.015, macro-band loss <0.25 dB for 10 turns on a 25-mm radium quarter circle, and long-term bend radium = 5.0 mm). The bandwidth-length product of the GI-POF has reached 1.1 GHz⋅km. Over a combination of 20-km SMF and 25-m GI-POF transmission, one half of the optical signal is received by a CATV receiver; as well as the other half is detected by a high-bandwidth photodiode (PD) (with a 3-dB bandwidth of 10 GHz), and passed through a BPF to remove the spurious. The CATV parameters of CNR, CSO and CTB are analyzed by an HP-8591C CATV analyzer. Subsequently, the 16-QAM OFDM signals are captured by a communications signal analyzer (Tektronix CSA7404B), and processed off-line with a MATLAB program to evaluate the BER performances and the corresponding constellation maps.

3. Experimental results and discussion

Figures 2(a)
Fig. 2 Electrical spectra of the combined CATV and 2.5Gbps/2.5GHz 16-QAM OFDM signals for (a) BTB case, (b) over a combination of 20-km SMF and 25-m GI-POF transmission case.
and 2(b) show the electrical spectral of the combined CATV and 2.5Gbps/2.5GHz 16-QAM OFDM signals for back-to-back (BTB) as well as over a combination of 20-km SMF and 25-m GI-POF transmission cases, respectively. Figures 3(a)
Fig. 3 Electrical spectra of the combined CATV and 5Gbps/2.5GHz 16-QAM OFDM signals for (a) BTB case, (b) over a combination of 20-km SMF and 25-m GI-POF transmission case.
and 3(b) present the electrical spectral of the combined CATV and 5Gbps/2.5GHz 16-QAM OFDM signals for the two cases. In order to provide suitable bandwidth utilization efficiency and to prevent signal interference between CATV and QAM OFDM signals, the central frequency of the employed OFDM signal is carefully selected at 2.5GHz. This is because that the required bandwidth of transmitting the 2.5Gbps/2.5GHz or 5Gbps/2.5GHz OFDM signals is 0.625 GHz or 1.25GHz. This means that the lowest frequencies of the 2.5Gbps/2.5GHz and 5Gbps/2.5GHz OFDM signal are 2.1875 GHz (2.5 – 0.625/2 = 2.1875) and 1.875 GHz (2.5 – 1.25/2 = 1.875), respectively. Both of them are far from the highest carrier frequency of CATV signal (550MHz) as well as are away from the highest 2nd harmonic distortion of the CATV signal (1.1GHz). If the central frequency of the transmitted OFDM signal is reduced to a lower value, such as 1.8 GHz, the frequency bands of these two OFDM signals will close to the highest 2nd harmonic distortion of the CATV signal. So they may be seriously interfered by the CATV signal. On the other hand, if the OFDM central frequency is increased to a higher level, such as 3 or 5 GHz, the entire CATV and OFDM signals will occupy a larger bandwidth and reduce the bandwidth utilization efficiency. As a result, the 2.5 GHz is a suitable central frequency for the employed OFDM signals. Although the 3rd and 4th harmonic distortions for 550 MHz are located at 1.65 and 2.2 GHz, in which they are close to the 1.875 and 2.1875 GHz. However, the amplitude of distortion decreases with the increasing of the order number. Thus, the 3rd and 4th harmonic distortions have very small amplitudes, so they will not induce distortions in QAM OFDM band [14

14. H. H. Lu, W. S. Tsai, C. Y. Chen, and H. C. Peng, “CATV/radio-on-fiber transport systems based on EAM and optical SSB modulation techniques,” IEEE Photon. Technol. Lett. 16(11), 2565–2567 (2004). [CrossRef]

]. In case the QAM OFDM signal is replaced by OOK format at the same central frequency, part of the 2.5Gbps/2.5GHz OOK signal will overlap with the CATV signal as the schematic diagram shown in the Fig. 4(a)
Fig. 4 Schematic spectrum diagram of (a) the 2.5Gbps/2.5GHz OOK signal and the CATV signal, and (b) the 2.5Gbps/3.05GHz OOK signal and the CATV signal.
. So the central frequency of the downstream wireless signal needs to be extended to at least 3.05GHz as shown in the Fig. 4(b). Comparing with 2.5Gbps/2.5GHz 16-QAM OFDM signal, it is expected that utilized such 2.5Gbps/3.05GHz OOK signal in the system not only has less spectrum efficiency but also has serious interference with the CATV signal.

To evaluate the transmitted OFDM signals performances, the measured BER curves and constellation maps are present in Figs. 5(a)
Fig. 5 The measured BER curves and constellation maps for (a) 2.5Gbps/2.5GHz OFDM signal and 2.5Gbps/3.05GHz OOK signal, (b) 5Gbps/2.5GHz OFDM signal and 5Gbps/5.55GHz OOK signal.
and 5(b), respectively. At a BER of 10−8, only a power penalty of 0.7 dB is presented in both 2.5Gbps/2.5GHz cases (Fig. 5(a)). And at a BER of 10−6, a small power penalty of 1 dB is presented in both 5Gbps/2.5GHz ones (Fig. 5(b)). It is obvious that the proposed in-building networks can provide good BER performances and constellation maps, even the OFDM data rate is increased from 2.5 Gbps to 5 Gbps, Error free transmissions are achieved to demonstrate the possibility of establishing a hybrid CATV/16-QAM OFDM in-building network over a combination of 20-km SMF and 25-m GI-POF links. Nevertheless, if the 2.5Gbps/2.5GHz and 5Gbps/2.5GHz OFDM signals are replaced by the 2.5Gbps/3.05GHz and 5Gbps/5.55GHz OOK signals, the relative BER performances are much worse.

Moreover, to find out the impact of 16-QAM OFDM signal and OOK signal on the CATV one, we also measure and evaluate the CATV parameters. The measured CNR, CSO and CTB values are presented in Fig. 6(a)
Fig. 6 The measured CNR, CSO and CTB values for transmitting signals of CATV and 2.5Gbps/2.5GHz 16-QAM OFDM ones as well as CATV and 2.5Gbps/3.05GHz OOK ones: (a) measured at point A of Fig. 1, (b) measured at point B of Fig. 1.
(measured at point A of Fig. 1) and Fig. 6(b) (measured at point B of Fig. 1); as well as Fig. 7(a)
Fig. 7 The measured CNR, CSO and CTB values for transmitting signals of CATV and 5Gbps/2.5GHz 16-QAM OFDM ones as well as CATV and 5Gbps/5.55GHz OOK ones: (a) measured at point A of Fig. 1, (b) measured at point B of Fig. 1.
(measured at point A of Fig. 1) and Fig. 7(b) (measured at point B of Fig. 1), respectively. For Figs. 6(a) and 6(b), the transmitted signals are CATV and 2.5Gbps/2.5GHz 16-QAM OFDM ones as well as CATV and 2.5Gbps/3.05GHz OOK ones. As to Figs. 7(a) and 7(b), the transmitted signals are CATV and 5Gbps/2.5GHz 16-QAM OFDM ones as well as CATV and 5Gbps/5.55GHz ones. It is clear that the CNR/CSO/CTB values always keep ≥43/53/53 dB under NTSC channel number when the CATV signal is transmitted with the OFDM signal. The measured CNR/CSO/CTB values are roughly 1.2/2/2 dB degraded by power degradations and nonlinear effects of the SMF and POF; however, the measured 43/53/53 dB still satisfies the CATV requirements. No effect of interaction is observed between these two signals due to large carrier frequency separation. Nevertheless, when the OFDM signal is replaced by OOK signal, the overall performance will not satisfy the NTSC standard requirements. In the system, the optical power level at the end of the GI-POF is roughly 0.2 dBm. According to the measured results in the Fig. 5, if a forward error correction (FEC) is employed, the minimum BER requirement for the OFDM signal can be reduced to roughly 10−3 [15

15. R. Hui and M. O’Sullivan, Fiber Optic Measurement Techniques (Elsevier Inc., 2009), pp. 483.

]. So a roughly 7 dB power budget is reserved for other applications. On the other hand, the core size of our optical CATV receiver is 9 μm which is much smaller than that in the GI-POF. When the optical signal is transmitting through the MMF to the CATV receiver, only a small portion of the optical signal can be received, so a serious 7.5 dB connection loss is presented between the GI-POF and CATV receiver. Fortunately, this loss can be eliminated by utilizing a bigger core receiver. The saved power budget can then be used to support additional two or three POF cables directed to different rooms.

4. Conclusions

References and links

1.

F. Grassi, J. Mora, B. Ortega, and J. Capmany, “Radio over fiber transceiver employing phase modulation of an optical broadband source,” Opt. Express 18(21), 21750–21756 (2010). [CrossRef] [PubMed]

2.

C. H. Chang, H. H. Lu, H. S. Su, C. L. Shih, and K. J. Chen, “A broadband ASE light source-based full-duplex FTTX/ROF transport system,” Opt. Express 17(24), 22246–22253 (2009). [CrossRef] [PubMed]

3.

C. W. Chow, C. H. Yeh, C. H. Wang, F. Y. Shih, C. L. Pan, and S. Chi, “WDM extended reach passive optical networks using OFDM-QAM,” Opt. Express 16(16), 12096–12101 (2008). [CrossRef] [PubMed]

4.

H.-H. Lu, C.-H. Chang, P.-C. Peng, H.-S. Su, and H.-W. Hu, “A radio-over-GI-POF transport system,” J. Lightwave Technol. 28(13), 1917–1921 (2010). [CrossRef]

5.

H. Yang, S. C. Lee, E. Tangdiongga, F. Breyer, S. Randel, and A. M. J. Koonen, “40-Gb/s transmission over 100m graded-index plastic optical fiber based on discrete multitone modulation,” in Conference on Optical Fiber Communications (OFC) (2009), paper PDPD8.

6.

J. Yu, D. Qian, M. Huang, Z. Jia, G. K. Chang, and T. Wang, “16Gbit/s radio OFDM signals over graded-index plastic optical fiber,” in European Conference on Optical Communications (ECOC) (2008), Vol. 5–237, p. 6.16.

7.

M. Asai, R. Hirose, A. Kondo, and Y. Koike, “High-bandwidth graded-index plastic optical fiber by the dopant diffusion coextrusion process,” J. Lightwave Technol. 25(10), 3062–3067 (2007). [CrossRef]

8.

C.-H. Chang, H.-S. Su, H.-H. Lu, P.-C. Peng, and H.-W. Hu, “Integrating fiber to the home and POF in-door routing CATV transport system,” J. Lightwave Technol. 28(12), 1864–1869 (2010). [CrossRef]

9.

W. Jian, C. Liu, H. C. Chien, S. H. Fan, J. Yu, J. Wang, C. Yu, Z. Dong, J. Yu, and G. K. Chang, “QPSK-OFDM radio over polymer optical fiber for broadband in-building 60GHz wireless access,” in Conference on Optical Fiber Communications (OFC) (2010), paper OTuF3.

10.

B. Liu, X. Xin, L. Zhang, K. Zhao, and C. Yu, “Broad convergence of 32QAM-OFDM ROF and WDM-OFDM-PON system using an integrated modulator for bidirectional access networks,” in Conference on Optical Fiber Communications (OFC) (2010), paper JThA26.

11.

E. Hugues-Salas, R. P. Giddings, X. Q. Jin, J. L. Wei, X. Zheng, Y. Hong, C. Shu, and J. M. Tang, “Real-time experimental demonstration of low-cost VCSEL intensity-modulated 11.25 Gb/s optical OFDM signal transmission over 25 km PON systems,” Opt. Express 19(4), 2979–2988 (2011). [CrossRef] [PubMed]

12.

H. J. R. Dutton, Understanding Optical Communications (Prentice Hall PTR, 1998), pp. 61–62.

13.

A. M. J. Koonen, A. Ng’oma, M. G. Larrode, F. M. Huijskens, I. T. Monroy, and G. D. Khoe, “Novel cost-efficient techniques for microwave signal delivery in fibre-wireless networks,” in European Conference on Optical Communications (ECOC) (2004), paper Th1.

14.

H. H. Lu, W. S. Tsai, C. Y. Chen, and H. C. Peng, “CATV/radio-on-fiber transport systems based on EAM and optical SSB modulation techniques,” IEEE Photon. Technol. Lett. 16(11), 2565–2567 (2004). [CrossRef]

15.

R. Hui and M. O’Sullivan, Fiber Optic Measurement Techniques (Elsevier Inc., 2009), pp. 483.

OCIS Codes
(060.0060) Fiber optics and optical communications : Fiber optics and optical communications
(060.2360) Fiber optics and optical communications : Fiber optics links and subsystems
(060.1155) Fiber optics and optical communications : All-optical networks

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: March 10, 2011
Revised Manuscript: April 25, 2011
Manuscript Accepted: April 28, 2011
Published: May 2, 2011

Citation
Hsiao-Chun Peng, Heng-Sheng Su, Hai-Han Lu, Chung-Yi Li, Peng-Chun Peng, Shang-Hua Wu, and Ching-Hung Chang, "Hybrid CATV/16-QAM OFDM in-building networks over SMF and GI-POF transport," Opt. Express 19, 9575-9581 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-10-9575


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References

  1. F. Grassi, J. Mora, B. Ortega, and J. Capmany, “Radio over fiber transceiver employing phase modulation of an optical broadband source,” Opt. Express 18(21), 21750–21756 (2010). [CrossRef] [PubMed]
  2. C. H. Chang, H. H. Lu, H. S. Su, C. L. Shih, and K. J. Chen, “A broadband ASE light source-based full-duplex FTTX/ROF transport system,” Opt. Express 17(24), 22246–22253 (2009). [CrossRef] [PubMed]
  3. C. W. Chow, C. H. Yeh, C. H. Wang, F. Y. Shih, C. L. Pan, and S. Chi, “WDM extended reach passive optical networks using OFDM-QAM,” Opt. Express 16(16), 12096–12101 (2008). [CrossRef] [PubMed]
  4. H.-H. Lu, C.-H. Chang, P.-C. Peng, H.-S. Su, and H.-W. Hu, “A radio-over-GI-POF transport system,” J. Lightwave Technol. 28(13), 1917–1921 (2010). [CrossRef]
  5. H. Yang, S. C. Lee, E. Tangdiongga, F. Breyer, S. Randel, and A. M. J. Koonen, “40-Gb/s transmission over 100m graded-index plastic optical fiber based on discrete multitone modulation,” in Conference on Optical Fiber Communications (OFC) (2009), paper PDPD8.
  6. J. Yu, D. Qian, M. Huang, Z. Jia, G. K. Chang, and T. Wang, “16Gbit/s radio OFDM signals over graded-index plastic optical fiber,” in European Conference on Optical Communications (ECOC) (2008), Vol. 5–237, p. 6.16.
  7. M. Asai, R. Hirose, A. Kondo, and Y. Koike, “High-bandwidth graded-index plastic optical fiber by the dopant diffusion coextrusion process,” J. Lightwave Technol. 25(10), 3062–3067 (2007). [CrossRef]
  8. C.-H. Chang, H.-S. Su, H.-H. Lu, P.-C. Peng, and H.-W. Hu, “Integrating fiber to the home and POF in-door routing CATV transport system,” J. Lightwave Technol. 28(12), 1864–1869 (2010). [CrossRef]
  9. W. Jian, C. Liu, H. C. Chien, S. H. Fan, J. Yu, J. Wang, C. Yu, Z. Dong, J. Yu, and G. K. Chang, “QPSK-OFDM radio over polymer optical fiber for broadband in-building 60GHz wireless access,” in Conference on Optical Fiber Communications (OFC) (2010), paper OTuF3.
  10. B. Liu, X. Xin, L. Zhang, K. Zhao, and C. Yu, “Broad convergence of 32QAM-OFDM ROF and WDM-OFDM-PON system using an integrated modulator for bidirectional access networks,” in Conference on Optical Fiber Communications (OFC) (2010), paper JThA26.
  11. E. Hugues-Salas, R. P. Giddings, X. Q. Jin, J. L. Wei, X. Zheng, Y. Hong, C. Shu, and J. M. Tang, “Real-time experimental demonstration of low-cost VCSEL intensity-modulated 11.25 Gb/s optical OFDM signal transmission over 25 km PON systems,” Opt. Express 19(4), 2979–2988 (2011). [CrossRef] [PubMed]
  12. H. J. R. Dutton, Understanding Optical Communications (Prentice Hall PTR, 1998), pp. 61–62.
  13. A. M. J. Koonen, A. Ng’oma, M. G. Larrode, F. M. Huijskens, I. T. Monroy, and G. D. Khoe, “Novel cost-efficient techniques for microwave signal delivery in fibre-wireless networks,” in European Conference on Optical Communications (ECOC) (2004), paper Th1.
  14. H. H. Lu, W. S. Tsai, C. Y. Chen, and H. C. Peng, “CATV/radio-on-fiber transport systems based on EAM and optical SSB modulation techniques,” IEEE Photon. Technol. Lett. 16(11), 2565–2567 (2004). [CrossRef]
  15. R. Hui and M. O’Sullivan, Fiber Optic Measurement Techniques (Elsevier Inc., 2009), pp. 483.

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