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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 11 — May. 23, 2011
  • pp: 10973–10978
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Analysis of the carrier-suppressed single-sideband modulators used to mitigate Rayleigh backscattering in carrier-distributed PON

C. W. Chow, C. H. Wang, C. H. Yeh, and S. Chi  »View Author Affiliations


Optics Express, Vol. 19, Issue 11, pp. 10973-10978 (2011)
http://dx.doi.org/10.1364/OE.19.010973


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Abstract

By using the carrier-suppressed single-sideband (CS-SSB) modulation, the Rayleigh backscattering (RB) experienced by the uplink signal can be effectively mitigated due to the reduction of the spectral overlap between the uplink signal and the distributed optical carrier. In this work, we first introduce the theoretical analysis of the CS-SSB generation using the dual-drive MZM (DD-MZM)-based and a dual-parallel MZM (DP-MZM)-based optical networking units (ONUs). Due to the different modulation mechanisms of the two CS-SSB modulations, the frequency components of the generated CS-SSB signals are also different. The transmission performance and the dispersion tolerance of the uplink signals generated by the two CS-SSB modulators are also analyzed and discussed.

© 2011 OSA

1. Introduction

2. Theoretical analysis and experiments of CS-SSB modulations

Figure 1
Fig. 1 The architectures of the CS-SSB generations using (a) DD-MZM: dual-drive MZM (b) DP-MZM: dual-paralleled MZM. Insets: vector diagrams of (i) DD-MZM; (ii) DP-MZM.
shows the architectures of the CS-SSB signals generated by the (a) DD-MZM-based and the (b) DP-MZM-based ONUs. For the architecture of the DD-MZM as shown in Fig. 1(a), the electric field at the upper arm is given by (1):
EDDMZM_upper(t)=Re{12E0ej(ω0t+Δφ(t))}=12E0cos(ω0t+Δφ(t))=12E0{cosω0tcosΔφ(t)sinω0tsinΔφ(t)},
(1)
where E0 and ω0 denote the amplitude and angular frequency of the input optical carrier respectively. Δϕ(t) = mcos(ωRFt), where m and ωRF denote the modulation depth and the angular frequency of the electrical driving signal. Then we replaceΔϕ(t)by mcos(ωRFt) and solve the Eq. (1) by using the Bessel functions. The higher orders (≧ 4th) Bessel terms can be neglected because the coefficients are small. The electric field at the output of upper arm can be simply as (2):

EDDMZM_upper(t)12E0{J0(m)cosω0tJ2(m)[cos(ω0t+2ωRFt)+cos(ω0t2ωRFt)]+J1(m)[sin(ω0t+ωRFt)+sin(ω0tωRFt)]J3(m)[sin(ω0t+3ωRFt)+sin(ω0t3ωRFt)]}.
(2)

For the lower arm of DD-MZM, the phase shift is negative because of the electric field is opposite to that of the upper arm, as well as the phase is shifted by a 90° due to the phase shifter. SoΔϕ(t)should be expressed as mcos(ωRFt + π/2) = -msin(ωRFt). Because of the same concept mentioned in upper arm, the electric field at the lower arm can be written as (3):

EDDMZM_lower(t)12E0{J0(m)cosω0t+J2(m)[cos(ω0t+2ωRFt)+cos(ω0t2ωRFt)]J1(m)[cos(ω0t+ωRFt)cos(ω0tωRFt)]J3(m)[cos(ω0t+3ωRFt)cos(ω0t3ωRFt)]}.
(3)

The phase of the lower arm should be shifted by another 90° because of the Vπ/2 DC Bias. Hence, we can see that the + ωRF electric field components can be cancelled at the output port of the DD-MZM as shown in the inset (i) of Fig. 1. Then, we chose a modulation depth (m) to suppress the central electrical component, i.e. the zero-order of the Bessel function J0(m) = 0. Hence, the CS-SSB signal can be successfully generated when m ≈2.4.

For the DP-MZM (Fig. 1(b)), it consists of three single-arm MZMs, and we named them as MZM1, MZM2 and MZM3. We applied driving voltage of Vπ to MZM1 and MZM2 and based on the same concept as used in the DD-MZM analysis. The electric field at MZM1 output is given by (4):

EMZM1(t)12E0{2J1(m)[sin(ω0t+ωRFt)+sin(ω0tωRFt)]2J3(m)[sin(ω0t+3ωRFt)+sin(ω0t3ωRFt)]}.
(4)

For MZM2, the phase is shifted by a 90° phase shifter and then the electric field at MZM2 output is given by (5):

EMZM2(t)12E0{2J1(m)[cos(ω0t+ωRFt)cos(ω0tωRFt)]2J3(m)[cos(ω0t+3ωRFt)cos(ω0t3ωRFt)]}.
(5)

Similarly, the phase at the MZM2 output should be shifted by another 90° because of the Vπ/2 DC Bias. The electric field components at the output port of the DP-MZM are shown inset (ii) of Fig. 1. We can observe that the + ωRF frequency component generated by the DP-MZM is the dominant, and it is independent of the driving modulation index. This also implies that we do not need to over-drive the modulator in order to achieve carrier wavelength suppression as in the case of the DD-MZM.

All the modulators used in the studies are commercially available. The modulation bandwidths and insertion losses of MODa and MODb are 9 GHz and 12 GHz; and 5 dB and 3.5 dB, respectively. The Vpi of MODa and MODb are 2.6 V at complementary driving and 5 V respectively. The DP-MZM is also called differential quadrature phase shift keying (DQPSK) modulator. The modulation bandwidth and the insertion loss of the DP-MZM are 12 GHz and 7 dB respectively. The Vpi of the DP-MZM is 5.5 V. For the case of CS-SSB MOD1, a shared DD-MZM (MODa) could be located at the remote node [12

12. C. W. Chow, C. H. Yeh, L. Xu, and H. K. Tsang, “Rayleigh backscattering mitigation using wavelength splitting for heterogeneous optical wired and wireless access,” IEEE Photon. Technol. Lett. 22(17), 1294–1296 (2010). [CrossRef]

] to simplify each ONU; however active components, such as electrical power supply and high speed (~10 GHz) diving circuit are required at the remote node.

3. Results and discussion

4. Conclusion

Acknowledgements

This work was supported by the National Science Council, Taiwan under Contracts NSC-98-2221-E-009-017-MY3 and NSC-99-2622-E-009-013-CC2.

References and links

1.

L. Y. Chan, C. K. Chan, D. T. K. Tong, F. Tong, and L. K. Chen, “Upstream traffic transmitter using injection-locked Fabry-Perot laser diode as modulator for WDM access networks,” Electron. Lett. 38(1), 43–45 (2002). [CrossRef]

2.

W. Hung, C. K. Chan, L. K. Chen, and F. Tong, “An optical network unit for WDM access networks with downstream DPSK and upstream remodulated OOK data using injection-locked FP laser,” IEEE Photon. Technol. Lett. 15(10), 1476–1478 (2003). [CrossRef]

3.

C. W. Chow, “Wavelength remodulation using DPSK down-and-upstream with high extinction ratio for 10-Gb/s DWDM-passive optical networks,” IEEE Photon. Technol. Lett. 20(1), 12–14 (2008). [CrossRef]

4.

G. Talli, C. W. Chow, E. K. MacHale, and P. D. Townsend, “Rayleigh noise mitigation in long-reach hybrid DWDM-TDM PONs,” J. Opt. Netw. 6, 765–776 (2007). [CrossRef]

5.

S.-K. Liaw, S.-L. Tzeng, and Y.-J. Hung, “Power penalty induced by Rayleigh backscattering in a bidirectional wavelength-reuse lightwave system,” Proc. CLEO (2001) CThL54.

6.

G. Talli, D. Cotter, and P. D. Townsend, “Rayleigh backscattering impairments in access networks with centralised light source,” Electron. Lett. 42(15), 877–878 (2006). [CrossRef]

7.

C. W. Chow, G. Talli, and P. D. Townsend, “Rayleigh noise reduction in 10-Gb/s DWDM-PONs by wavelength detuning and phase-modulation-induced spectral broadening,” IEEE Photon. Technol. Lett. 19(6), 423–425 (2007). [CrossRef]

8.

C. W. Chow, G. Talli, A. D. Ellis, and P. D. Townsend, “Rayleigh noise mitigation in DWDM LR-PONs using carrier suppressed subcarrier-amplitude modulated phase shift keying,” Opt. Express 16(3), 1860–1866 (2008). [CrossRef] [PubMed]

9.

J. Prat, M. Omella, and V. Polo, “Wavelength shifting for colorless ONUs in single-fiber WDM-PONs,” Proc. OFC (2007), Anaheim, CA, OFE1.

10.

C. H. Wang, C. W. Chow, C. H. Yeh, C. L. Wu, S. Chi, and C. Lin, “Rayleigh noise mitigation using single sideband modulation generated by a dual-parallel MZM for carrier distributed PON,” IEEE Photon. Technol. Lett. 22(11), 820–822 (2010). [CrossRef]

11.

C. W. Chow and C. H. Yeh, “Mitigation of Rayleigh backscattering in 10-Gb/s downstream and 2.5-Gb/s upstream DWDM 100-km long-reach PONs,” Opt. Express 19(6), 4970–4976 (2011). [CrossRef] [PubMed]

12.

C. W. Chow, C. H. Yeh, L. Xu, and H. K. Tsang, “Rayleigh backscattering mitigation using wavelength splitting for heterogeneous optical wired and wireless access,” IEEE Photon. Technol. Lett. 22(17), 1294–1296 (2010). [CrossRef]

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

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: February 25, 2011
Revised Manuscript: April 4, 2011
Manuscript Accepted: April 8, 2011
Published: May 20, 2011

Citation
C. W. Chow, C. H. Wang, C. H. Yeh, and S. Chi, "Analysis of the carrier-suppressed single-sideband modulators used to mitigate Rayleigh backscattering in carrier-distributed PON," Opt. Express 19, 10973-10978 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-11-10973


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References

  1. L. Y. Chan, C. K. Chan, D. T. K. Tong, F. Tong, and L. K. Chen, “Upstream traffic transmitter using injection-locked Fabry-Perot laser diode as modulator for WDM access networks,” Electron. Lett. 38(1), 43–45 (2002). [CrossRef]
  2. W. Hung, C. K. Chan, L. K. Chen, and F. Tong, “An optical network unit for WDM access networks with downstream DPSK and upstream remodulated OOK data using injection-locked FP laser,” IEEE Photon. Technol. Lett. 15(10), 1476–1478 (2003). [CrossRef]
  3. C. W. Chow, “Wavelength remodulation using DPSK down-and-upstream with high extinction ratio for 10-Gb/s DWDM-passive optical networks,” IEEE Photon. Technol. Lett. 20(1), 12–14 (2008). [CrossRef]
  4. G. Talli, C. W. Chow, E. K. MacHale, and P. D. Townsend, “Rayleigh noise mitigation in long-reach hybrid DWDM-TDM PONs,” J. Opt. Netw. 6, 765–776 (2007). [CrossRef]
  5. S.-K. Liaw, S.-L. Tzeng, and Y.-J. Hung, “Power penalty induced by Rayleigh backscattering in a bidirectional wavelength-reuse lightwave system,” Proc. CLEO (2001) CThL54.
  6. G. Talli, D. Cotter, and P. D. Townsend, “Rayleigh backscattering impairments in access networks with centralised light source,” Electron. Lett. 42(15), 877–878 (2006). [CrossRef]
  7. C. W. Chow, G. Talli, and P. D. Townsend, “Rayleigh noise reduction in 10-Gb/s DWDM-PONs by wavelength detuning and phase-modulation-induced spectral broadening,” IEEE Photon. Technol. Lett. 19(6), 423–425 (2007). [CrossRef]
  8. C. W. Chow, G. Talli, A. D. Ellis, and P. D. Townsend, “Rayleigh noise mitigation in DWDM LR-PONs using carrier suppressed subcarrier-amplitude modulated phase shift keying,” Opt. Express 16(3), 1860–1866 (2008). [CrossRef] [PubMed]
  9. J. Prat, M. Omella, and V. Polo, “Wavelength shifting for colorless ONUs in single-fiber WDM-PONs,” Proc. OFC (2007), Anaheim, CA, OFE1.
  10. C. H. Wang, C. W. Chow, C. H. Yeh, C. L. Wu, S. Chi, and C. Lin, “Rayleigh noise mitigation using single sideband modulation generated by a dual-parallel MZM for carrier distributed PON,” IEEE Photon. Technol. Lett. 22(11), 820–822 (2010). [CrossRef]
  11. C. W. Chow and C. H. Yeh, “Mitigation of Rayleigh backscattering in 10-Gb/s downstream and 2.5-Gb/s upstream DWDM 100-km long-reach PONs,” Opt. Express 19(6), 4970–4976 (2011). [CrossRef] [PubMed]
  12. C. W. Chow, C. H. Yeh, L. Xu, and H. K. Tsang, “Rayleigh backscattering mitigation using wavelength splitting for heterogeneous optical wired and wireless access,” IEEE Photon. Technol. Lett. 22(17), 1294–1296 (2010). [CrossRef]

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