Abstract

This paper discusses a method of reducing the polarization dependence of gain (PDG) of a distributed Raman amplifier. Reducing its PDG is important for a Raman amplifier because it is higher than that of an erbium-doped fiber amplifier and can degrade transmission performance. Raman PDG is determined primarily by two factors, namely 1) polarization-mode dispersion (PMD) of the transmission fiber and 2) degree of polarization (DOP) of the pump source. The authors propose a simple analytical model to show the required pump light DOP for a given transmission fiber's PMD and the allowable PDG. For instance, a low pump DOP of 5% produces a low PDG of 0.2 dB under typical fiber PMD conditions, in which the analytical model agrees well with experiment. Subsequently, to achieve the required DOP, the pump source configuration is investigated in detail. The authors used one length of polarization-maintaining fiber (PMF) as an efficient pump depolarizer and evaluated its performance for various pump light spectra. It has been shown that the DOP following the depolarizer is determined simply by Fourier transformation of the pump light spectrum. The analysis in this paper has led to the important result that a Fabry–Pérot laser diode pump with a short piece of PMF is effective in achieving a low pump DOP due to its multimode spectrum when the length of the PMF is properly adjusted for the longitudinal-mode spacing frequency. It has been verified that a Raman amplifier's PDG can be reduced by the proposed efficient depolarizer sufficiently for a PDG-reduced Raman amplifier repeater to be applicable to long-haul transmission systems.

© 2006 IEEE

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  1. G. Charlet, J. C. Antona, S. Lanne, P. Tran, W. Idler, M. Gorlier, S. Bome, A. Klekamp, C. Simonneau, L. Pierre, Y. Frignac, M. Molina, F. Beaumont, P. Hamaide, S. Bigo, "6.4 Tb/s (159 x 42.7 Gb/s) capacity over 21 x 100 km using bandwidth-limited phase-shaped binary transmission," Europe Conf. Optical Communication (ECOC), Copenhagen, Denmark, 2002, PD4.1.
  2. T. Tsuritani, K. Ishida, A. Agata, K. Shimomura, I. Morita, T. Tokura, H. Taga, T. Mizuochi, N. Edagawa, "70 GHz-spaced 40 x 42.7 Gb/s transmission over 8700 km using CS-RZ DPSK signal, all-Raman repeaters and symmetrically dispersion-managed fiber span," Optical Fiber Communication (OFC) Conf., Atlanta, GA, 2003, PD23.
  3. B. Zhu, C. R. Doerr, P. Gaarde, L. E. Nelson, S. Stulz, L. Stulz, L. Gruner-Nielsen, "72-nm continuous single-band transmission of 3.56 Tb/s (89 x 42.7 Gb/s) over 4000 km of NZDF fiber," Europe Conf. Optical Communication (ECOC), Rimini, Italy, 2003, Tu 4.6.2.
  4. H. Masuda, M. Tomizawa, Y. Miyamoto, "High-performance distributed Raman amplification systems: practical aspects and field trial results," Optical Fiber Communication (OFC) Conf., Anaheim, CA, 2005, OThF5.
  5. H. H. Kee, C. R. S. Fludger, V. Handerek, "Statistical properties of polarisation dependent gain in fibre Raman amplifiers," Optical Fiber Communication (OFC) Conf., Anaheim, CA, WB2.
  6. R. H. Stolen, "Polarization effects in fiber Raman and Brillouin lasers," IEEE J. Quantum Electron. QE-15, 1157-1160 (1979).
  7. J. Zhang, V. Dominic, M. Missey, S. Sanders, D. Mehuys, "Dependence of Raman polarization dependent gain on pump degree of polarization at high gain levels," Optical Amplifiers Applications Conf., QC, Canada, 2000, OMB4.
  8. K. Takada, K. Okamoto, J. Noda, "New fiber-optic depolarizer," J. Lightw. Technol. LT-4, 213-219 (1986).
  9. D. R. Lutz, "A passive fiber-optic depolarizer," IEEE Photon. Technol. Lett. 4, 463-465 (1993).
  10. J. S. Wang, J. R. Costelloe, R. H. Stolen, "Reduction of the degree of polarization of a laser diode with a fiber Lyot depolarizer," IEEE Photon. Technol. Lett. 11, 1449-1451 (1999).
  11. D. Flannery, A. Karakasidis, O. Moteau, "Depolarisation techniques for distributed Raman pump units using semiconductor Bragg grating stabilised laser sources," Proc. NFOEC Tech. (2001) pp. 1251-1258.
  12. H. Kidorf, K. Rottwitt, M. Nissov, M. Ma, E. Rabarijaona, "Pump interactions in a 100-nm bandwidth Raman amplifier," IEEE Photon. Technol. Lett. 11, 530-532 (1999).
  13. S. Kado, Y. Emori, S. Namiki, "Gain and noise tilt control in multi-wavelength bi-directionally pumped Raman amplifier," Proc. OFC (2002) pp. 62-63.
  14. T. Mizuochi, K. Kinjo, S. Kajiya, T. Tokura, K. Motoshima, "Bidirectional unrepeatered 43 Gb/s WDM transmission with C/L band-separated Raman amplification," J. Lightw. Technol. 20, 2079-2085 (2002).
  15. Q. Lin, G. Agrawal, "PMD effects in fiber-based Raman amplifiers," Optical Fiber Communication (OFC) Conf., Atlanta, GA, 2003, TuC4.
  16. E. Son, J. Lee, Y. Chung, "Gain variation of Raman amplifier in birefringent fiber," Optical Fiber Communication (OFC) Conf., Atlanta, CA, 2003, TuC5.
  17. T. Tokura, T. Mizuochi, "On the mitigation of polarization dependency of distributed Raman amplifier gain by transmission fiber PMD," OptoElectronics Communication Conf. (OECC), Shanghai, China, 2003, 16E4-6.
  18. T. Tokura, T. Kogure, T. Sugihara, K. Shimizu, T. Mizuochi, K. Motoshima, "Pump light depolarization method for low PDG Raman amplification," Optical Fiber Communication (OFC) Conf., Anaheim, CA, 2002, ThGG24.
  19. T. Tokura, T. Kogure, T. Sugihara, T. Mizuochi, K. Motoshima, "A depolarized methodology for PDG mitigation of multi-longitudinal laser-pumped fiber Raman amplifier," OptoElectronics Communications Conf. (OECC), Yokohama, Japan, 2002, 10D2-4.
  20. C. Brosseau, Fundamentals of Polarized Light: A Statistical Optics Approach (Wiley-Interscience, 1998) pp. 102-105.

IEEE J. Quantum Electron.

R. H. Stolen, "Polarization effects in fiber Raman and Brillouin lasers," IEEE J. Quantum Electron. QE-15, 1157-1160 (1979).

IEEE Photon. Technol. Lett.

D. R. Lutz, "A passive fiber-optic depolarizer," IEEE Photon. Technol. Lett. 4, 463-465 (1993).

J. S. Wang, J. R. Costelloe, R. H. Stolen, "Reduction of the degree of polarization of a laser diode with a fiber Lyot depolarizer," IEEE Photon. Technol. Lett. 11, 1449-1451 (1999).

H. Kidorf, K. Rottwitt, M. Nissov, M. Ma, E. Rabarijaona, "Pump interactions in a 100-nm bandwidth Raman amplifier," IEEE Photon. Technol. Lett. 11, 530-532 (1999).

J. Lightw. Technol.

K. Takada, K. Okamoto, J. Noda, "New fiber-optic depolarizer," J. Lightw. Technol. LT-4, 213-219 (1986).

T. Mizuochi, K. Kinjo, S. Kajiya, T. Tokura, K. Motoshima, "Bidirectional unrepeatered 43 Gb/s WDM transmission with C/L band-separated Raman amplification," J. Lightw. Technol. 20, 2079-2085 (2002).

Other

Q. Lin, G. Agrawal, "PMD effects in fiber-based Raman amplifiers," Optical Fiber Communication (OFC) Conf., Atlanta, GA, 2003, TuC4.

E. Son, J. Lee, Y. Chung, "Gain variation of Raman amplifier in birefringent fiber," Optical Fiber Communication (OFC) Conf., Atlanta, CA, 2003, TuC5.

T. Tokura, T. Mizuochi, "On the mitigation of polarization dependency of distributed Raman amplifier gain by transmission fiber PMD," OptoElectronics Communication Conf. (OECC), Shanghai, China, 2003, 16E4-6.

T. Tokura, T. Kogure, T. Sugihara, K. Shimizu, T. Mizuochi, K. Motoshima, "Pump light depolarization method for low PDG Raman amplification," Optical Fiber Communication (OFC) Conf., Anaheim, CA, 2002, ThGG24.

T. Tokura, T. Kogure, T. Sugihara, T. Mizuochi, K. Motoshima, "A depolarized methodology for PDG mitigation of multi-longitudinal laser-pumped fiber Raman amplifier," OptoElectronics Communications Conf. (OECC), Yokohama, Japan, 2002, 10D2-4.

C. Brosseau, Fundamentals of Polarized Light: A Statistical Optics Approach (Wiley-Interscience, 1998) pp. 102-105.

S. Kado, Y. Emori, S. Namiki, "Gain and noise tilt control in multi-wavelength bi-directionally pumped Raman amplifier," Proc. OFC (2002) pp. 62-63.

D. Flannery, A. Karakasidis, O. Moteau, "Depolarisation techniques for distributed Raman pump units using semiconductor Bragg grating stabilised laser sources," Proc. NFOEC Tech. (2001) pp. 1251-1258.

J. Zhang, V. Dominic, M. Missey, S. Sanders, D. Mehuys, "Dependence of Raman polarization dependent gain on pump degree of polarization at high gain levels," Optical Amplifiers Applications Conf., QC, Canada, 2000, OMB4.

G. Charlet, J. C. Antona, S. Lanne, P. Tran, W. Idler, M. Gorlier, S. Bome, A. Klekamp, C. Simonneau, L. Pierre, Y. Frignac, M. Molina, F. Beaumont, P. Hamaide, S. Bigo, "6.4 Tb/s (159 x 42.7 Gb/s) capacity over 21 x 100 km using bandwidth-limited phase-shaped binary transmission," Europe Conf. Optical Communication (ECOC), Copenhagen, Denmark, 2002, PD4.1.

T. Tsuritani, K. Ishida, A. Agata, K. Shimomura, I. Morita, T. Tokura, H. Taga, T. Mizuochi, N. Edagawa, "70 GHz-spaced 40 x 42.7 Gb/s transmission over 8700 km using CS-RZ DPSK signal, all-Raman repeaters and symmetrically dispersion-managed fiber span," Optical Fiber Communication (OFC) Conf., Atlanta, GA, 2003, PD23.

B. Zhu, C. R. Doerr, P. Gaarde, L. E. Nelson, S. Stulz, L. Stulz, L. Gruner-Nielsen, "72-nm continuous single-band transmission of 3.56 Tb/s (89 x 42.7 Gb/s) over 4000 km of NZDF fiber," Europe Conf. Optical Communication (ECOC), Rimini, Italy, 2003, Tu 4.6.2.

H. Masuda, M. Tomizawa, Y. Miyamoto, "High-performance distributed Raman amplification systems: practical aspects and field trial results," Optical Fiber Communication (OFC) Conf., Anaheim, CA, 2005, OThF5.

H. H. Kee, C. R. S. Fludger, V. Handerek, "Statistical properties of polarisation dependent gain in fibre Raman amplifiers," Optical Fiber Communication (OFC) Conf., Anaheim, CA, WB2.

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