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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 20 — Sep. 24, 2012
  • pp: 22523–22530
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System evaluation of economic 16/32chs 1.25Gbps WDM-PON with self-seeded RSOA

Yiran Ma, Dekun Liu, Jingwen Yu, and Xiaomu Wang  »View Author Affiliations


Optics Express, Vol. 20, Issue 20, pp. 22523-22530 (2012)
http://dx.doi.org/10.1364/OE.20.022523


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Abstract

We investigate a novel WDM-PON system by using self-seeded Reflective Semiconductor Optical Amplifier (RSOA) both in downstream and upstream. The transmission performance is evaluated and reported for the first time and meets carrier level requirements.

© 2012 OSA

1. Introduction

Passive optical network (PON) such as Ethernet PON (EPON) and Gigabit PON (GPON) has been widely used in fiber-to-the-home (FTTH) deployment nowadays. Many advantages have been shown for PON system, such as passive infrastructure all the way, no line interference, high bandwidth, and etc. However, as applications with high bandwidth draw customers’ attentions, EPON and GPON will be not sufficient to provide enough bandwidth for new services such as backhaul of Common Public Radio Interface (CPRI) protocol data of wireless distributed sites, high definition video, cloud computing, and etc [1

1. T. Koonen, “Fiber to the home/fiber to the premise: what, where, and when?” Proc. IEEE 94(5), 911–934 (2006). [CrossRef]

,2

2. G.-K. Chang, Z. Jia, J. Yu, and A. Chowdhury, “Super broadband optical wireless access technologies,” in Proc. OFC, paper OThD1, San Diego, USA, 2008.

]. To solve this problem, EPON and GPON are upgraded to 10G EPON and 10G GPON respectively [3

3. R. Davey, J. Kani, F. Bourgart, and K. McCammon, “Options for future optical access networks,” IEEE Commun. Mag. 44(10), 50–56 (2006). [CrossRef]

]. Since the downstream and upstream comply broadcast and TDMA, there are always security problems and bandwidth seizing problem among different end users. Wavelength division multiplexed (WDM) PON was proposed to provide high dedicated bandwidth [4

4. D. K. Jung, S. K. Shin, C.-H. Lee, and Y. C. Chung, “Wavelength-division-multiplexed passive optical network based on spectrum-slicing techniques,” IEEE Photon. Technol. Lett. 10(9), 1334–1336 (1998). [CrossRef]

7

7. Y. C. Chung, “Challenges toward practical WDM PON,” in Proc. OECC 2006, Kaohsiung, Taiwan, 2006.

]. Both security and bandwidth are guaranteed as different users are separated by different wavelengths. The key technology for WDM-PON is colorless transmitter to achieve convenience of installation and low inventory. Currently, some colorless transmitters are demonstrated using tunable lasers, modulation of sliced external broadband light source (BLS) or re-modulation of downstream signal light [8

8. 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]

14

14. F. Payox, P. Chanclou, and N. Genay, “WDM-PON with colorless ONUs,” in Proc. OFC, paper OTuG5, Anaheim, USA, 2007.

] These solutions encounters poor performance, large footprint of BLS components as well as relatively high cost. Other ideas like Self-seeding reflective semiconductor amplifier (RSOA) scheme were proposed later on [15

15. E. Wong, K. L. Lee, and T. Anderson, “Directly modulated self-seeding reflective SOAs as colorless transmitters for WDM passive optical networks,” in Proc. OFC, paper PDP49, Anaheim, USA, 2006.

17

17. L. Marazzi, P. Parolari, G. de Valicourt, and M. Martinelli, “Network-embedded self-tuning cavity for WDM-PON transmitter,” in Proc. ECOC, Geneva, Switzerland, 2011.

]. In this paper, a novel WDM-PON with self-seeded RSOAs both in downstream and upstream is demonstrated and system performance with 32 and 16 channels is evaluated, showing that it meets carrier level requirements for the first time.

2. Principle of self-seeded WDM-PON

The Faraday rotator mirror is a combination of a mirror and a Faraday rotator which rotates the polarization axis by π/4, and has been used to compensate for birefringence of fibers in fiber interferometers and fiber amplifiers. The Fabry–Perot cavity composed of FRMs is known as a unique configuration to stabilize the polarization by using non-PM fibers [18

18. Y. Takushima, S. Yamashita, K. Kikuchi, and K. Hotate, “Polarization-stable and single-frequency fiber lasers,” J. Lightwave Technol. 16(4), 661–669 (1998). [CrossRef]

]. By using the FRM as the common mirror of the self-seeded lasers, the polarization of the signal injected to the RSOA is always orthogonal to that of original output signal. Based on this principle, the FRM not only stabilizes the polarization of the injected signal, but also decreases the polarization dependent gain requirement.

3. Simulations

The self-seeded laser above can be considered as an external cavity laser, the operating principle can be analyzed using multimode rate equations [19

19. G. P. Agrawal and N. K. Dutta, Long-Wavelength Semiconductor Lasers (Van Nostrand Reinhold, 1986).

,20

20. S. Hansmann, H. Walter, H. Hillmer, and H. Burkhard, “Static and dynamic properties of InGaAsP-InP distributed feedback lasers-a detailed comparison between experiment and theory,” IEEE J. Quantum Electron. 30(11), 2477–2484 (1994). [CrossRef]

]:
dNdt=IqVNτei=MM(ΓeυgegieSie+ΓmυgmgimSim)+FN
(1)
dSiedt=ΓeυgegieSie+βNτeSieτp+αiυgκSim(tτ)+FSie
(2)
dSimdt=ΓmυgmgimSim+βNτsSimτp+αiυgκSie(tτ)+FSim
(3)
gi=[ag(NN0)/V(λiλ0)2/G02]/(1+εi=1p(Sie+Sim))
(4)
Here I denotes the injection current through the active volume, q the electron charge, V the volume of the active section, υg the group velocity ; githe power material gain of the mode i; N is the carrier density in active volume, Sie, Simare the TE and TM photon density of the ith mode, respectively; Γe,Γmare the optical confinement factors for TE and TM mode, respectively; τe is spontaneous carrier lifetime, τp is the photon lifetime ; agis the differential gain coefficient, εis the gain saturation factor, β is Spontaneous coupling factor.

τis the photon roundtrip time along the whole external cavity, αiis the cavity roundtrip loss for the ith mode, κis the photon emission factor in the front facet of RSOA. The fourth item in the right of Eq. (2) and (3) denotes the self injection effect. When the FRM is used in the common port of the AWG, due to the FRM always rotates the polarization axis of the reflected signal by π/2, the TE mode is partially injected into the TM mode by a time delayτ, similarly the TM mode is partially injected to the TE mode by the same time delay τ .

Figure 3
Fig. 3 Simulation of the optical spectrum evolution for Self-seeded laser.
shows the operating simulation of the self-seeded laser. The parameters used in the model are given in Table 1

Table 1. Parameters used in the model

table-icon
View This Table
. At first, the RSOA emits a broad band ASE spectrum, as Fig. 3(a) shows. When the RSOA is connected to one channel of the AWG, the modes in the pass band of the AWG channel will be partially reflected back to the RSOA. So after one roundtrip, the modes in the AWG pass band obtain more power than the modes outside. After five roundtrips, the modes in the AWG pass band increase dramatically while the modes outside the pass band are deeply suppressed. After 100 roundtrips, the spectrum is quite similar with that after five roundtrips, only the side mode suppression ratio (SMSR) increases a bit further. The AWG is in the system is a Gaussian AWG with 100 GHz spacing; the FRM has an 80% reflectivity and 20% transmission ratio. From Fig. 3, we can see that the self-seeded laser can reach the steady state after several roundtrips.

4. Experiments

In the test bed, the gain medium is RSOA with build-in modulation function. In the 32 channel WDM-PON system, an odd 100GHz AWG and an even 100 GHz AWG are combined with an interleaver to a “50 GHz” spacing AWG. Standard Gigabit Ethernet package is applied in the evaluation test bed. The operation wavelengths are set in C band from 1531 nm to 1560 nm. 32 ONUs are connected to the AWG ports in C + band, with the upstream wavelength from 1547.72 nm~1561.02 nm, while the downstream wavelengths are from 1531.5 nm~1543.73 nm in C- band. The test bed devices are shown in Fig. 4
Fig. 4 System devices of the test bed.
. In the OLT, two WDM-PON cards with 16 GE ports on each are used to communicate with the ONUs. The transmission distance is 20km normally without further notice. In the test bed, only 27 ONUs are activated for the 32 channel system, and the other 5 ONUs are activated for the 16 channel system with 200 GHz AWG. The physical bit rate is 1.25 Gbit/s and the payload data rate of all the channels is up to 1 Gbit/s.

Figure 5
Fig. 5 Combined B2B spectra for both upstream and downstream (yellow: OLT downstream transmission, green: ONU upstream transmission)
shows the back-to-back spectra coming out of FRM1 and FRM2 for upstream and downstream signal composing of all the 27 out of 32 channels in total. The total power at the output of FRM1 and FRM2 are both about 5 dBm. The space among the first several channels is left for the 5 channels of 16 channel system, so the mode spacing for the first 5 modes is 0.8 nm, while for the left 22 modes is 0.4 nm. Figure 6
Fig. 6 Combined spectra for both upstream and downstream after 20 km transmission: (a) ONU upstream transmission; (b) OLT downstream transmission
shows the spectra after 20 km transmission for upstream and downstream signal in which no obvious deterioration has been observed. The reason ONU’s transmission spectra is wider than OLT’s ones is that there is 1 km fiber cavity between each ONU and FRM2. Therefore, the oscillation between ONU and FRM2 will suffer more loss and have worse side mode suppression effect. This piece of 1 km fiber is used to simulate scenarios in real applications where certain distance may exist between users and AWG.

Figure 7(a)
Fig. 7 (a) RSOA output spectra of Channel 17 before and after self-seeded with 1km cavity (yellow: ASE, pink: after self-seeded); (b) Eye diagram after FRM2
shows the RSOA self-seeded performance of Channel 17 in 32 channel system and 7(b) shows the eye diagram after the FRM2. It is obvious that the broadband ASE turns into stimulated signal with wavelength aligned with AWG passband. The colorless technique is achieved in a very economic way and the whole oscillation process only takes several roundtrips’ time, which is usually no more than several hundred microseconds after the RSOA is powered on. From the eye diagram, the extinction ratio is roundabout 6dB. Due to the residual data noise in the reflected signal, the extinction ratio is always limited and hard to increase further. However, it’s sufficient already for a system level’s transmission when the FEC function is open.

The distance between ONU and FRM2 is also an important factor which affects the system performance. The gain medium in the ONU optical module, AWG channel and FRM2 constitute a self-seeded laser. Here we denote the distance between the ONU and the FRM2 as the “Cavity length”. Figure 11
Fig. 11 BER after 20km versus different cavity length
shows the performance variation at different cavity length after 20km for both 32/16 channel systems. All the BER is measured when the received power before APD is −28 dBm. The BER increases monotonically with the cavity length from several meters to 5 km. When the cavity length increases, the insertion loss becomes larger, the roundtrip time also increases consequently. Both these factors decrease the self-injection effect hence the spectrum becomes wider and BER becomes larger. When the cavity length increases to long enough, the gain of the RSOA can’t overcome the roundtrip insertion loss and the ASE noise of other modes. The whole system would fail to work. As shown in Fig. 11, both 32/16 channel systems can support at least 5 km cavity length after 20 km with the FEC function open. In practical application scenarios, the distance between the ONU and FRM is rarely over 5km. Therefore, no further test is done for cavity length longer than 5 km.

Moreover, throughput test is performed to further prove the performance for both 32 and 16 channel systems with 20 km fiber. 5 channels of 16 channel system and 27 channels of 32 channel system are tested together with maximum data rate allowed by the test instrument, in which the maximum payload data rate for a channel is 1 Gbit/s. The received power for every channel is about −25 dBm in 32 channel system, and −20 dBm in 16 channel system (No interleaver in 16 channel system). No packet loss has been observed during more than 14 hours with the FEC function open, indicating that the system works with error free.

5. Conclusion

This paper proposes an economic WDM-PON system using self-seeded colorless lasers both in OLT and ONU. And for the first time the system level performance of self-seeded WDM-PON is investigated and evaluated. The test result shows that self-seeded WDM-PON system can meet carrier level requirements.

References and links

1.

T. Koonen, “Fiber to the home/fiber to the premise: what, where, and when?” Proc. IEEE 94(5), 911–934 (2006). [CrossRef]

2.

G.-K. Chang, Z. Jia, J. Yu, and A. Chowdhury, “Super broadband optical wireless access technologies,” in Proc. OFC, paper OThD1, San Diego, USA, 2008.

3.

R. Davey, J. Kani, F. Bourgart, and K. McCammon, “Options for future optical access networks,” IEEE Commun. Mag. 44(10), 50–56 (2006). [CrossRef]

4.

D. K. Jung, S. K. Shin, C.-H. Lee, and Y. C. Chung, “Wavelength-division-multiplexed passive optical network based on spectrum-slicing techniques,” IEEE Photon. Technol. Lett. 10(9), 1334–1336 (1998). [CrossRef]

5.

G.-K. Chang, A. Chowdhury, Z. Jia, H.-C. Chien, M.-F. Huang, J. Yu, and G. Ellinas, “Key technologies of WDM-PON for future converged optical broadband access networks,” J. Opt. Commun. 1(4), C35–C50 (2009). [CrossRef]

6.

K. Y. Cho, S. P. Jung, A. Murakami, A. Agata, Y. Takushima, and Y. C. Chung, “Recent progresses in RSOA-based WDM PON,” in International Conference of Transparent Optical Networks, 2009.

7.

Y. C. Chung, “Challenges toward practical WDM PON,” in Proc. OECC 2006, Kaohsiung, Taiwan, 2006.

8.

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]

9.

A. Banerjee, Y. Park, F. Clarke, H. Song, S. Yang, G. Kramer, K. Kim, and B. Mukherjee, “Wavelength-division-multiplexed passive optical network (WDM-PON) technologies for broadband access: a review,” J. Opt. Netw. 4(11Issue 11), 737–758 (2005). [CrossRef]

10.

K. Y. Cho, Y. Takushima, K. R. Oh, and Y. C. Chung, “Operating wavelength range of 1.25-Gb/s WDM PON implemented by using RSOA’s,” in Proc. OFC, paper OTuH3, San Diego, USA, 2008.

11.

H. S. Shin, D. K. Jung, D. H. Shin, S. B. Park, J. S. Lee, I. K. Yun, S. W. Kim, Y. J. Oh, and C. S. Shin, “16 x 1.25 Gbit/s WDM-PON based on ASE-injected R-SOAs in 60 ° C temperature range,” in Proc. OFC, paper OTuC5, Anaheim, USA, 2006.

12.

S. Y. Kim, S. B. Jun, Y. Takushima, E. S. Son, and Y. C. Chung, “Enhanced performance of RSOA-based WDM PON by using Manchester coding,” J. Opt. Netw. 6(6), 624–630 (2007). [CrossRef]

13.

K. Y. Cho, Y. J. Lee, H. Y. Choi, A. Murakami, A. Agata, Y. Takushima, and Y. C. Chung, “Effects of reflection in RSOA-based WDM PON utilizing remodulation technique,” J. Lightwave Technol. 27(10), 1286–1295 (2009). [CrossRef]

14.

F. Payox, P. Chanclou, and N. Genay, “WDM-PON with colorless ONUs,” in Proc. OFC, paper OTuG5, Anaheim, USA, 2007.

15.

E. Wong, K. L. Lee, and T. Anderson, “Directly modulated self-seeding reflective SOAs as colorless transmitters for WDM passive optical networks,” in Proc. OFC, paper PDP49, Anaheim, USA, 2006.

16.

M. Presi and E. Ciaramella, “Stable self-seeding of Reflective-SOAs for WDM-PONs,” in Proc. OFC, paper OMP4, Los Angeles, USA, 2011.

17.

L. Marazzi, P. Parolari, G. de Valicourt, and M. Martinelli, “Network-embedded self-tuning cavity for WDM-PON transmitter,” in Proc. ECOC, Geneva, Switzerland, 2011.

18.

Y. Takushima, S. Yamashita, K. Kikuchi, and K. Hotate, “Polarization-stable and single-frequency fiber lasers,” J. Lightwave Technol. 16(4), 661–669 (1998). [CrossRef]

19.

G. P. Agrawal and N. K. Dutta, Long-Wavelength Semiconductor Lasers (Van Nostrand Reinhold, 1986).

20.

S. Hansmann, H. Walter, H. Hillmer, and H. Burkhard, “Static and dynamic properties of InGaAsP-InP distributed feedback lasers-a detailed comparison between experiment and theory,” IEEE J. Quantum Electron. 30(11), 2477–2484 (1994). [CrossRef]

OCIS Codes
(060.2330) Fiber optics and optical communications : Fiber optics communications
(060.4250) Fiber optics and optical communications : Networks

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: June 12, 2012
Revised Manuscript: August 9, 2012
Manuscript Accepted: August 12, 2012
Published: September 17, 2012

Citation
Yiran Ma, Dekun Liu, Jingwen Yu, and Xiaomu Wang, "System evaluation of economic 16/32chs 1.25Gbps WDM-PON with self-seeded RSOA," Opt. Express 20, 22523-22530 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-20-22523


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References

  1. T. Koonen, “Fiber to the home/fiber to the premise: what, where, and when?” Proc. IEEE94(5), 911–934 (2006). [CrossRef]
  2. G.-K. Chang, Z. Jia, J. Yu, and A. Chowdhury, “Super broadband optical wireless access technologies,” in Proc. OFC, paper OThD1, San Diego, USA, 2008.
  3. R. Davey, J. Kani, F. Bourgart, and K. McCammon, “Options for future optical access networks,” IEEE Commun. Mag.44(10), 50–56 (2006). [CrossRef]
  4. D. K. Jung, S. K. Shin, C.-H. Lee, and Y. C. Chung, “Wavelength-division-multiplexed passive optical network based on spectrum-slicing techniques,” IEEE Photon. Technol. Lett.10(9), 1334–1336 (1998). [CrossRef]
  5. G.-K. Chang, A. Chowdhury, Z. Jia, H.-C. Chien, M.-F. Huang, J. Yu, and G. Ellinas, “Key technologies of WDM-PON for future converged optical broadband access networks,” J. Opt. Commun.1(4), C35–C50 (2009). [CrossRef]
  6. K. Y. Cho, S. P. Jung, A. Murakami, A. Agata, Y. Takushima, and Y. C. Chung, “Recent progresses in RSOA-based WDM PON,” in International Conference of Transparent Optical Networks, 2009.
  7. Y. C. Chung, “Challenges toward practical WDM PON,” in Proc. OECC 2006, Kaohsiung, Taiwan, 2006.
  8. 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]
  9. A. Banerjee, Y. Park, F. Clarke, H. Song, S. Yang, G. Kramer, K. Kim, and B. Mukherjee, “Wavelength-division-multiplexed passive optical network (WDM-PON) technologies for broadband access: a review,” J. Opt. Netw.4(11Issue 11), 737–758 (2005). [CrossRef]
  10. K. Y. Cho, Y. Takushima, K. R. Oh, and Y. C. Chung, “Operating wavelength range of 1.25-Gb/s WDM PON implemented by using RSOA’s,” in Proc. OFC, paper OTuH3, San Diego, USA, 2008.
  11. H. S. Shin, D. K. Jung, D. H. Shin, S. B. Park, J. S. Lee, I. K. Yun, S. W. Kim, Y. J. Oh, and C. S. Shin, “16 x 1.25 Gbit/s WDM-PON based on ASE-injected R-SOAs in 60 ° C temperature range,” in Proc. OFC, paper OTuC5, Anaheim, USA, 2006.
  12. S. Y. Kim, S. B. Jun, Y. Takushima, E. S. Son, and Y. C. Chung, “Enhanced performance of RSOA-based WDM PON by using Manchester coding,” J. Opt. Netw.6(6), 624–630 (2007). [CrossRef]
  13. K. Y. Cho, Y. J. Lee, H. Y. Choi, A. Murakami, A. Agata, Y. Takushima, and Y. C. Chung, “Effects of reflection in RSOA-based WDM PON utilizing remodulation technique,” J. Lightwave Technol.27(10), 1286–1295 (2009). [CrossRef]
  14. F. Payox, P. Chanclou, and N. Genay, “WDM-PON with colorless ONUs,” in Proc. OFC, paper OTuG5, Anaheim, USA, 2007.
  15. E. Wong, K. L. Lee, and T. Anderson, “Directly modulated self-seeding reflective SOAs as colorless transmitters for WDM passive optical networks,” in Proc. OFC, paper PDP49, Anaheim, USA, 2006.
  16. M. Presi and E. Ciaramella, “Stable self-seeding of Reflective-SOAs for WDM-PONs,” in Proc. OFC, paper OMP4, Los Angeles, USA, 2011.
  17. L. Marazzi, P. Parolari, G. de Valicourt, and M. Martinelli, “Network-embedded self-tuning cavity for WDM-PON transmitter,” in Proc. ECOC, Geneva, Switzerland, 2011.
  18. Y. Takushima, S. Yamashita, K. Kikuchi, and K. Hotate, “Polarization-stable and single-frequency fiber lasers,” J. Lightwave Technol.16(4), 661–669 (1998). [CrossRef]
  19. G. P. Agrawal and N. K. Dutta, Long-Wavelength Semiconductor Lasers (Van Nostrand Reinhold, 1986).
  20. S. Hansmann, H. Walter, H. Hillmer, and H. Burkhard, “Static and dynamic properties of InGaAsP-InP distributed feedback lasers-a detailed comparison between experiment and theory,” IEEE J. Quantum Electron.30(11), 2477–2484 (1994). [CrossRef]

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