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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 24 — Nov. 23, 2009
  • pp: 22246–22253
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A broadband ASE light source-based full-duplex FTTX/ROF transport system

Ching-Hung Chang, Hai-Han Lu, Heng-Sheng Su, Chien-Liang Shih, and Kai-Jen Chen  »View Author Affiliations


Optics Express, Vol. 17, Issue 24, pp. 22246-22253 (2009)
http://dx.doi.org/10.1364/OE.17.022246


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Abstract

A full-duplex fiber-to-the-X (FTTX)/radio-over-fiber (ROF) transport system based on a broadband amplified spontaneous emission (ASE) light source is proposed and demonstrated for rural wide-spread villages. Combining the concepts of long-transmission transmission and ring topology, a long-haul single-mode fiber (SMF) trunk is sharing with multiple rural villages. Externally modulated baseband (BB) (1.25 Gbps) and radio-frequency (RF) (622Mbps/10GHz) signals are successfully transmitted simultaneously. Good bit error rate (BER) performance was achieved to demonstrate the practice of providing wire/wireless connections for long-haul wide-spread rural villages. Since our proposed system uses only a broadband ASE light source to achieve multi-wavelengths transmissions, it also reveals an outstanding one with simpler and more economic advantages.

© 2009 OSA

1. Introduction

In addition to develop a suitable network topology, the simplification of light source is also a key issue should be concerned in implementing successful full-duplex FTTX/ROF transport systems. Few techniques, such as utilizing spectrum-sliced light source [9

9. H. Kim, S. Kim, S. Hwang, and Y. Oh, “Impact of dispersion, PMD, and PDL on the performance of spectrum-sliced incoherent light sources using gain-saturated semiconductor optical amplifiers,” J. Lightwave Technol. 24(2), 775–785 ( 2006). [CrossRef]

11

11. J. S. Lee, Y. C. Chung, and D. J. DiGiovanni, “Spectrum-sliced fiber amplifier light source for multichannel WDM applications,” IEEE Photon. Technol. Lett. 5(12), 1458–1461 ( 1993). [CrossRef]

], have been developed to overcome the light source problem. The spectrum slicing is a feasible technique in which narrow wavelength is filtered from a broadband light source and externally modulated to transmit optical signal. Additionally, it is attractive because it avoids the need of multiple laser diodes (LDs) and reveals a prominent one with simpler and more economic advantages. The high power amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA) can be efficiently divided into many channels by using arrayed waveguide grating (AWG) demultiplexer (DEMUX).

2. Experimental setup

For the downstream transmissions, the optical signals are generated at the CS and then distributed through the SMF to relative remote base stations (BSs), BS1-BS4, by using cascaded EDFAs and OADMs. The full-duplex FTTX/ROF transport systems exploit the available bandwidth of 1530-1560 nm to address multiple BSs at different locations. In the experiment, the optical signal is transmitted through five SMF spans (30km × 5) with the help of five EDFAs. Each BS is connected to the fiber backbone by an OADM which deals with an individual wavelength. When the modulated signals reach a BS, the appropriate downstream wavelength and the relative upstream data are dropped and added by the OADM respectively.

As shown in Fig. 2
Fig. 2 The configurations of OADM and BS.
, the OADM, with >40 dB add/drop channel isolation, consists of one fiber Bragg grating (FBG) located between two optical circulators (OCs) to reflect the dedicated wavelength from the trunk. The reflected optical signal is then circuited to the BS by the first OC. To exam the downstream transmission, the dropped optical signal is adjusted by a variable optical attenuator (VOA), detected by a broadband photodiode (PD), separated off by a 1×3 RF splitter, and went through two separate RF filters (1.5GHz/low-pass filter (LPF) and 10GHz/band-pass filter (BPF)) and one microwave antenna. To analyze the downstream BER performance, the 1.25 Gbps data signal was directly fed into a BER tester and the 622Mbps/10GHz data stream was demodulated before fed into a BER tester.

3. Experiment results and discussions

The configuration of the broadband ASE light source is shown in Fig. 3
Fig. 3 The configuration of the broadband ASE light source.
. It is composed by a two-stage EDFA pumped with LDs at 980 nm. Two 980-nm pumping LDs with 180 mW pumping power were coupled into a 15-m EDF by two 980/1550 nm wavelength-division-multiplexing (WDM) couplers. Two optical isolators were used to prevent reflections from the output end. The optical spectrum of broadband ASE light source and the output of multiplexed signals are shown in Fig. 4(a)
Fig. 4 (a) The optical spectrum of broadband ASE light source and the output of multiplexed signals. (b) The optical spectrum for the four selected wavelengths.
. The bandwidth of the ASE spectrum is as wide as 80 nm, and the flatness from 1526 to 1606 nm is 1 dB. It also can be seen that the multiplexed signals have a free spectral range (FSR) of 15 nm. To guarantee successful design of a full-duplex FTTX/ROF transport system, system designers must minimize the crosstalk in system, so that we select the wavelengths of λ1, λ2, λ3 and λ4 from the odd channels of AWG DEMUX output to avoid the crosstalk that arises from the incomplete isolation of the adjacent channels at the AWG DEMUX output. The optical spectrum for the four selected wavelengths is illustrated in Fig. 4(b). The spectrum-sliced four wavelengths of λ1, λ2, λ3, and λ4 are 1549.96, 1550.76, 1551.56 and 1552.36 nm, with a channel spacing of 0.8 nm (100 GHz).

To further verify the process of sharing the spectrum-sliced ASE light source among BSs, the electrical spectrum of downstream (CS→BS3) BB and RF signals after PD detection is presented in Fig. 6
Fig. 6 The electrical spectrum of downstream (CS→BS3) BB and RF signals after PD detection.
. Since the 10 GHz RF carrier frequency is the integer multiple of the 1.25 GHz, the 8th order harmonic distortion of the 1.25 Gbps BB signal is overlapping with the RF signal. However, the amplitude of distortion decreases with the increasing of the order number. Thus, the 8th harmonic distortion has very small amplitude, so it will not induce distortion in ROF band. The eye diagrams of downstream BB and RF signals at the BS3 are demonstrated in Fig. 7(a) and (b)
Fig. 7 The eye diagrams of downstream (a) BB and (b) RF signals at the BS3.
, respectively. Although little and undesired jitter and amplitude fluctuations are introduced; nevertheless, clear and open eye diagrams for both BB and RF signals are still observed.

Table 1. The comparison of power penalty for RF signal (ROF) with respect to BB one (FTTX) at different BS.

table-icon
View This Table

When the ASE is utilized as the WDM light source, the signal-to-noise ratio (SNR) of ASE light at the receiver is given by [11

11. J. S. Lee, Y. C. Chung, and D. J. DiGiovanni, “Spectrum-sliced fiber amplifier light source for multichannel WDM applications,” IEEE Photon. Technol. Lett. 5(12), 1458–1461 ( 1993). [CrossRef]

]:
SNR=BoBe
(1)
where Bo is the optical bandwidth, and Be is the electrical bandwidth. It is clear that the SNR is proportional to the optical bandwidth and inverse proportional to the electrical bandwidth. Since the optical bandwidth (the spectrum-sliced ASE light source) of the system is larger than the carried electrical bandwidth (10 GHz), the SNR value is improved in which causing system with better BER performance, and lead to an improvement of receiver sensitivity.

From the serious discussions and the demonstrated experiment results, we can declare that the novel systems not only reveals simple and economic advantages by employing a single broadband ASE light source to replace multiple LDs, but also demonstrates an efficient and practical topology to serve wide-spread rural villages.

4. Conclusions

We have proposed a long-haul full-duplex FTTX/ROF transport system based on a single broadband ASE light source and ring topology to serve multiple rural villages. The configuration of the broadband ASE light source and the process of spectrum slicing the light source to serve long-distance multi-wavelengths transmission are seriously discussed. The feasibility of our proposed systems is demonstrated and accompanied with good BER performance over a long-haul fiber link. Since our proposed full-duplex FTTX/ROF transport system sharing the trunk fiber with multi-villages and do not use multiple LDs, it reveals a prominent alternative with advantages in simplicity and cost to provide triple play services for wide-spread rural area villages.

References and links

1.

H. H. Lu, W. Y. Lin, H. C. Peng, C. Y. Li, and H. S. Su, “Fiber-to-the-home integration with digital link on microwave subcarrier transport systems,” Prog. Electromagn. Res. C 7, 125–136 ( 2009). [CrossRef]

2.

H. H. Lu, C. Y. Li, C. H. Lee, Y. C. Hsiao, and H. W. Chen, “Radio-over-Fiber Transport Systems Based on DFB LD with Main and -1 Side Modes Injection-Locked Techniques,” Prog. Electromagn. Res. Lett. 7, 25–33 ( 2009). [CrossRef]

3.

V. M. Serdyuk, “Dielectric study of bound water in grain at radio and microwave frequencies,” Prog. Electromagn. Res. 84, 379–406 ( 2008). [CrossRef]

4.

R. Llorente, T. Alves, M. Morant, M. Beltran, J. Perez, A. Cartaxo, and J. Marti, “Ultra-wideband radio signals distribution in FTTH nettworks,” IEEE Photon. Technol. Lett. 20(11), 945–947 ( 2008). [CrossRef]

5.

C. T. Lin, J. Chen, P. C. Peng, C. F. Peng, W. R. Peng, B. S. Chiou, and S. Chi, “Hybrid optical access network integrating fiber-to-the-home and radio-over-fiber systems,” IEEE Photon. Technol. Lett. 19(8), 610–612 ( 2007). [CrossRef]

6.

K.-I. Kitayama, T. Kuri, H. Toda, and J. J. V. Olmos, “Radio over fiber: DWDM analog/digital access network and its enabling technologies,” in Proceedings of Lasers and Electro-Optics Society (LEOS), (Lake Buena Vista, Florida, 2007), pp.794–795.

7.

ITU-T Recommendation G.984.1, “Gigabit-capable Passive Optical Networks (GPON): General characteristics,”

8.

J. Li and G. Shen, “Cost Minimization Planning for Greenfield Passive Optical Networks,” IEEE/OSA J. Opt. Commun. Netw. 1(1), 17–29 ( 2009). [CrossRef]

9.

H. Kim, S. Kim, S. Hwang, and Y. Oh, “Impact of dispersion, PMD, and PDL on the performance of spectrum-sliced incoherent light sources using gain-saturated semiconductor optical amplifiers,” J. Lightwave Technol. 24(2), 775–785 ( 2006). [CrossRef]

10.

H. D. Kim, S. G. Kang, and C. H. Lee, “A low-cost WDM source with an ASE injected Fabry-Perot semiconductor laser,” IEEE Photon. Technol. Lett. 12(8), 1067–1069 ( 2000). [CrossRef]

11.

J. S. Lee, Y. C. Chung, and D. J. DiGiovanni, “Spectrum-sliced fiber amplifier light source for multichannel WDM applications,” IEEE Photon. Technol. Lett. 5(12), 1458–1461 ( 1993). [CrossRef]

OCIS Codes
(060.0060) Fiber optics and optical communications : Fiber optics and optical communications
(060.2330) Fiber optics and optical communications : Fiber optics communications
(350.4010) Other areas of optics : Microwaves

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: September 2, 2009
Revised Manuscript: October 30, 2009
Manuscript Accepted: November 12, 2009
Published: November 20, 2009

Citation
Ching-Hung Chang, Hai-Han Lu, Heng-Sheng Su, Chien-Liang Shih, and Kai-Jen Chen, "A broadband ASE light source-based full-duplex FTTX/ROF transport system," Opt. Express 17, 22246-22253 (2009)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-24-22246


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References

  1. H. H. Lu, W. Y. Lin, H. C. Peng, C. Y. Li, and H. S. Su, “Fiber-to-the-home integration with digital link on microwave subcarrier transport systems,” Prog. Electromagn. Res. C 7, 125–136 (2009). [CrossRef]
  2. H. H. Lu, C. Y. Li, C. H. Lee, Y. C. Hsiao, and H. W. Chen, “Radio-over-Fiber Transport Systems Based on DFB LD with Main and -1 Side Modes Injection-Locked Techniques,” Prog. Electromagn. Res. Lett. 7, 25–33 (2009). [CrossRef]
  3. V. M. Serdyuk, “Dielectric study of bound water in grain at radio and microwave frequencies,” Prog. Electromagn. Res. 84, 379–406 (2008). [CrossRef]
  4. R. Llorente, T. Alves, M. Morant, M. Beltran, J. Perez, A. Cartaxo, and J. Marti, “Ultra-wideband radio signals distribution in FTTH nettworks,” IEEE Photon. Technol. Lett. 20(11), 945–947 (2008). [CrossRef]
  5. C. T. Lin, J. Chen, P. C. Peng, C. F. Peng, W. R. Peng, B. S. Chiou, and S. Chi, “Hybrid optical access network integrating fiber-to-the-home and radio-over-fiber systems,” IEEE Photon. Technol. Lett. 19(8), 610–612 (2007). [CrossRef]
  6. K.-I. Kitayama, T. Kuri, H. Toda, and J. J. V. Olmos, “Radio over fiber: DWDM analog/digital access network and its enabling technologies,” in Proceedings of Lasers and Electro-Optics Society (LEOS), (Lake Buena Vista, Florida, 2007), pp.794–795.
  7. ITU-T Recommendation G.984.1, “Gigabit-capable Passive Optical Networks (GPON): General characteristics,”
  8. J. Li and G. Shen, “Cost Minimization Planning for Greenfield Passive Optical Networks,” IEEE/OSA J. Opt. Commun. Netw. 1(1), 17–29 (2009). [CrossRef]
  9. H. Kim, S. Kim, S. Hwang, and Y. Oh, “Impact of dispersion, PMD, and PDL on the performance of spectrum-sliced incoherent light sources using gain-saturated semiconductor optical amplifiers,” J. Lightwave Technol. 24(2), 775–785 (2006). [CrossRef]
  10. H. D. Kim, S. G. Kang, and C. H. Lee, “A low-cost WDM source with an ASE injected Fabry-Perot semiconductor laser,” IEEE Photon. Technol. Lett. 12(8), 1067–1069 (2000). [CrossRef]
  11. J. S. Lee, Y. C. Chung, and D. J. DiGiovanni, “Spectrum-sliced fiber amplifier light source for multichannel WDM applications,” IEEE Photon. Technol. Lett. 5(12), 1458–1461 (1993). [CrossRef]

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