OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 24 — Nov. 23, 2009
  • pp: 22246–22253

Optics InfoBase > Optics Express > Volume 17 > Issue 24 > Page 22246

« Show journal navigation

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


View Full Text Article

Acrobat PDF (351 KB)


Advanced Search

Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

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

Radio networks provide users an attractive feature of untethered connectivity for a range of applications including cellular communications, wireless local area networks, and broadband fixed wireless access. The applications of transmitting and distributing radio signals over optical fiber in those networks bring a lot of benefits, including high-performance remote links and reduced infrastructure costs. In recent years, much attention has been focused on the prospects of extending fiber optical networks over the last mile of the network to the subscribers’ premises. Integrating large capacity Fiber-to-the-X (FTTX) architectures with high mobility radio-over-fiber (ROF) transport systems presents a potential of supplying broadband wire services and flexible wireless connections concurrently. To achieve this objective, multiple FTTX/ROF transport systems have been proposed to provide a way to transmit baseband (BB) and radio-frequency (RF) signals simultaneously [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]

–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.

]. Nevertheless, most of the hybrid systems are developed as tree topology or point to point connection, which is suit to deploy in urban area or long-distance small-differential area respectively. For some rural areas where the villages are small and far from each other, a single tree topology network with limited differential connection length is not able to cover whole area [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]

]. Providing each rural village a single long-haul fiber connection in another hand is not economic enough to be accepted. This paper is therefore proposed a novel architecture to serve wide-spread villages with economic deploying cost. To overcome the limitation of differential physical fiber distance among villages, the entire rural villages in the novel proposal are serially connected as a ring topology by a set of long-haul single-mode fiber (SMF). The downstream signals will be distributed from the central station (CO) to the trunk and then drop by an optical add-drop multiplexer (OADM) in each village. Similarly, the upstream data from each village will be added to the trunk by the OADM and be transmitted back to the CO. The long-reach ring topology is then providing an economic way to share the trunk with multiple rural villages. Furthermore, if there is a fiber-link-broken happening, this proposal also potentially provides a self-healing functionality by delivering the blocked data stream from another direction.

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

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

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).

In this paper, a feasible long-distance full-duplex FTTX/ROF transport system based on broadband ASE light source is proposed and demonstrated to serve the clients in rural area. Externally modulated BB (1.25 Gbps) and RF (622Mbps/10GHz) signals are successfully transmitted simultaneously. Low bit error rate (BER) values were obtained over a long-haul SMF link in our proposed systems.

2. Experimental setup

The experimental configuration of our proposed long-haul full-duplex FTTX/ROF transport systems employing a single broadband ASE light source is shown in Fig. 1 . For down-link transmission, the CS is composed of a broadband ASE light source, two EDFAs, a Mach-Zehnder modulator (MZM), a pseudorandom binary sequence (PRBS) generator, a microwave signal generator, and a pair of AWG multiplexer (MUX)/DEMUX. Due to the limited number of MZM in our lab, the output of the ASE light source was firstly amplified by an EDFA and the entire downstream light source was externally modulated by a single MZM before spectrum-sliced. Since this experiment is to verify the transmission performance, the same downstream data in each channel will not affect the final outcome. The modulated optical carrier was then efficiently split into four optical channels by an AWG DEMUX, and multiplexed into other EDFA by an AWG MUX. Four wavelengths of λ1 (channel 1), λ2 (channel 3), λ3 (channel 5), and λ4 (channel 7) from the odd channels of AWG DEMUX output were selected for downstream light sources. 622 Mbps data signal was mixed with a 10 GHz microwave carrier to generate a RF data stream and a data signal of 1.25 Gbps, with a PRBS length of 215-1, was combined with the stream before externally modulated at the MZM.

Fig. 1 Experimental configuration of our proposed long-haul full-duplex FTTX/ROF transport systems.

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 , 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.

Fig. 2 The configurations of OADM and BS.

In parallel with the downstream transmission analysis, the up-link optical signal is added to the fiber backbone and transmitted to the CS, where upstream signals are separated using an optical tunable band-pass filter (TBPF) to select the desired wavelength. As shown in the lower part of the Fig. 1, the signal is adjusted by a VOA, detected by a PD, separated off by a 1×2 RF splitter, and went through two separate RF filters (1.5GHz/LPF and 10GHz/BPF). The 1.25 Gbps data signal was directly fed into a BER tester for BER analysis, and the 622Mbps/10GHz data stream was demodulated and fed into a BER tester for BER analysis.

3. Experiment results and discussions

The configuration of the broadband ASE light source is shown in Fig. 3 . 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) . 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).

Fig. 3 The configuration of the broadband ASE light source.
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 measured down/up-link BER curves for the FTTX (1.25 Gbps) and the ROF (622Mbps/10GHz) applications as a function of the received optical power level are plotted in the Fig. 5(a) and (b) , respectively. For down-link transmission (CS→BS3; 90 km) and at a BER of 10-9, the received optical power levels are -25 and -26.4 dBm for the FTTX (1.25 Gbps) and the ROF (622Mbps/10GHz) data signal transmission, respectively. For up-link transmission (BS2→CS; 90 km) and at a BER of 10-9, the received optical power levels are -25 and -26.6 dBm for the FTTX (1.25 Gbps) and the ROF (622Mbps/10GHz) data signal transmission, respectively. Good BER performances are achieved over a 90-km SMF transport for both down and up links. It verifies that wide-spread rural villages can be wire/wireless served by the long-haul full-duplex ring topology, and the proposed FTTX/ROF transport system can be constructed by employing an ASE light source. In addition, the back-to-back (BTB) BER curves are also given in Fig. 5(a) and (b), respectively. At a BER of 10-9; there exist large power penalties of 8.8 dB (FTTX) and 7.9 dB (ROF) between the BTB cases and over 90-km SMF transport ones for down-link transmission; and there exist large power penalties of 8.9 dB (FTTX) and 8.1 dB (ROF) between the BTB cases and over 90-km SMF transport ones for up-link transmission. These large power penalties are due to fiber dispersion-induced penalties. And further, the comparison of power penalty for RF signal (ROF) with respect to BB one (FTTX) at different BS is listed in Table 1. Consequently, the power penalty of down-link transmission is gradually increased from 1.1 dB (BS1) to 1.7 dB (BS4); as well as the up-link transmission is gradually increased from 1 dB (BS4) to 1.6 dB (BS1). It clearly denotes that the power penalty is proportional to the fiber length. Longer fiber length leads to larger fiber dispersion, in which resulting in larger power penalty.

Fig. 5 Measured BER curves for FTTX (1.25Gbps) and ROF (10GHz/622Mbps) applications (a) down-link, (b) up-link.

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 . 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) , 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.

Fig. 6 The electrical spectrum of downstream (CS→BS3) BB and RF signals after PD detection.
Fig. 7 The eye diagrams of downstream (a) BB and (b) RF signals at the BS3.
Table 1  The comparison of power penalty for RF signal (ROF) with respect to BB one (FTTX) at different BS.
BSsBS1BS2BS3BS4
Power penalty for RF signal (ROF) with respect to BB signal (FTTX) (down-link transmission)1.1 dB1.2 dB1.4 dB1.7 dB
Power penalty for RF signal (ROF) with respect to BB signal (FTTX) (up-link transmission)1.6 dB1.3 dB1.1 dB1 dB

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

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= Bo Be
(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.

In addition to the practical and economic advantages in the proposed structure, the combination of ring topology and long-haul fiber optical distribution also presents a potentially non-blocked functionality. If, for example, the one-directional full-duplex transmission characteristic in the experimental configuration is modified to bi-directional full-duplex structure, a single fiber-link broken can be logically re-healed by transmitting the blocked traffics from another direction. This advancement provides system maintainers enough time to fix the disconnected fiber without interrupting network services.

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


Sort:  Author  |  Year  |  Journal  |  Reset  

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]

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.

CrossCheck Deposited