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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 4 — Feb. 19, 2007
  • pp: 1454–1460
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Double-pass high-gain low-noise EDFA over Sand C+L-bands by tunable fundamental-mode leakage loss

Chi-Ming Hung, Nan-Kuang Chen, Yinchieh Lai, and Sien Chi  »View Author Affiliations


Optics Express, Vol. 15, Issue 4, pp. 1454-1460 (2007)
http://dx.doi.org/10.1364/OE.15.001454


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Abstract

We demonstrate a high-gain low-noise double-pass tunable EDFA over S- and C+L-bands by discretely introducing fundamental-mode leakage loss in a 16-m-long standard C-band Er3+-doped fiber. The amplified spontaneous emission at the wavelengths of longer than 1530 nm can be substantially attenuated by the ASE suppressing filters to maintain high population inversion and to squeeze out the optical gain for S-band signals. When the filters are disabled, the gain bandwidth immediately returns back to the C+L-bands. Under S-band operation, a 37 dB small signal gain and a minimum 4.84 dB noise figure at 1486.9 nm are achieved with a 980 nm pump power of 154 mW.

© 2007 Optical Society of America

1. Introduction

In contrast, a high cutoff efficiency fundamental-mode leakage loss filter can be achieved based on material dispersion discrepancy between core and cladding [16

16. N. K. Chen, S. Chi, and S. M. Tseng, “Wideband tunable fiber short-pass filter based on side-polished fiber with dispersive polymer overlay,” Opt. Lett. 29,2219–2221 (2004). [CrossRef] [PubMed]

]. The filters had been utilized in an EDFA to realize amplification over S- and C + L-bands [17

17. N. K. Chen, K. C. Hsu, S. Chi, and Y. Lai, “Tunable Er3+-doped fiber amplifiers covering S- and C + L-bands over 1490-1610 nm based on discrete fundamental-mode cutoff filters,” Opt. Lett. 31,2842–2844 (2006). [CrossRef] [PubMed]

]. The filters can significantly suppress the C+L-band ASE to accomplish a high population inversion in S-band. When the filters are temperature-tuned to be disabled, the filters play as all-pass filters and thus the amplification immediately returns back to the C+L-band. In this paper, we employ the high-cutoff-efficiency fundamental-mode leakage-loss filters in standard C-band silica-based EDF with a double-pass EDFA configuration to achieve a high-gain low-noise S-band EDFA. A 37 dB small signal gain and a 4.84 dB NF are achieved at 1486.9 nm (S-band). In addition, the gain spectra can be extended to the C+L-band based on this tunable double-pass EDFA consisting of a 16-m-long standard silica-based C-band EDF under a 980 nm pump power of 154 mW.

Fig. 1. Experimental set-up of the double-pass EDFA spanning S- and C+L-bands.

2. Fabrication and experiments

Fig. 2. (a). Spectral responses of the tapered fiber fundamental-mode cutoff filters using Cargille liquid (nD = 1.456) at 28.1°C (RES: 1 nm). (b) Evolution of the gain spectra under S-band operation from the output of the different stage of the filters and EDFs (RES: 0.1 nm).

In this double-pass EDFA, there are some unavoidable optical losses to degrade the gain efficiency of the amplification. First, the splicing loss between the SMF-28 (Corning) and the EDF (POFC) is about 0.35 dB for each splicing point due to the mismatch of the numerical aperture (NA) between SMF-28 (NA = 0.13) and EDF (NA = 0.2). Thus, there are 16 points to cause total 5.6 dB loss for double-pass configuration. Second, the 980/1550 WDM coupler and the ARM can respectively induce 0.4 dB and 0.9 dB loss while the S-band signal (1486.9 nm) passing through/reflecting from them for each time. Finally, the OC is designed for C-band operation and thus the induced loss at 1486.9 nm is measured to be 4.1 dB for the signal traveling from port 1 to port 3. In order to investigate the influences of C+L-band ASE suppression on the variations of S-band gain, the evolution of gain spectra is investigated by each gain stage as shown in Fig. 2(b) based on the single-pass and forward-pumping scheme. First of all, the input signal is recorded and a 4-m-long EDF is then added to achieve 4.75 dB gain, measured by an OSA under the resolution bandwidth (RES) of 0.1 nm, for the S-band signal. Second, a short-pass filter is added and then temperature-tuned to suppress of the C+L-band ASE shown in Fig. 2(b). Again, this filtered signal enters another 4-m-long EDF to acquire 6.04 dB gain for S-band signal. Following the steps repeatedly until two gain stages are connected, the S-band signal is found to grow up gradually. Thus, a high-gain low-noise S-band amplification should be achievable for this double-pass EDFA and the final measured results will be presented below.

3. Results of measurements

To investigate the amplification characteristics in S- and C+L-bands, a 980 nm pump laser with 154 mW fiber-pigtailed output power is launched into the EDF through a 980/1550 WDM coupler in a forward pumping scheme. Subsequently, the input signals in S-, C-, and L-bands are respectively launched into the EDF with an output power of -33 dBm. The high cutoff efficiency fundamental-mode leakage loss filters in the 16-m-long EDF can discretely suppress the unwanted ASE in the C+L-bands and pass the S-band signal and 980 nm pump wavelength. The input signal spectra (Pi) and amplified output signal spectra (Po) in S-bands at 30.9°C and in C+L-band at 40°C are shown in Fig. 3(a) under 0.1 nm RES. In S-band, the small signal gain at 1486.9 nm is measured to be around 32 dB while in C+L-bands the maximal signal gains at 1549.6 and 1589.4 nm were measured to be 43 dB and 17.8 dB, respectively. At 30.9°C, the S-band output signal power gradually increased with increasing pump power, similar to the evolution of gain spectra in Fig. 2(b), because the C+L-band ASE is discretely and substantially suppressed every 4-m-long EDF. Actually, the small gain at 1486.9 nm can reach 37 dB or more when the 5.6 dB splicing losses are neglected since in principle the splicing losses can be avoided by directly tapering the EDFs as the short-pass filters. The optical losses coming from the 980/1550 WDM coupler, ARM, and OC can be further avoided by using the suitable fiber components designed for S-band wavelengths operation. By doing so, the S-band gain at 1486.9 nm could probably be greater than 43 dB for this double-pass EDFA.

At 30.9°C, the input power of 1486.9 nm signal is varied to measure the gain and NF, as shown in Fig. 3(b). With the 980 nm pump power of 154 mW, the S-band gain changes from 32 dB to 4 dB as the signal input power varying from -33 dBm to -2.5 dBm. The gain compression of 3 dB small signal gain value determines the saturation signal power. Thus, the saturation signal power was about -19 dBm while the saturation output power was +9.91 dBm, which corresponds to a 6.36% power-conversion efficiency and is mainly limited by the absorption of 16-m-long EDF. In Fig. 3(b), the NF varies from 4.84 dB to 8.7 dB with increasing signal input power. By estimation, under the -25 dBm signal input power, the NF is about 5.3 dB and the signal gain is about 31.2 dB at 1486.9 nm wavelength. Obviously, our double-pass EDFA can achieve not only a higher signal gain than other S-band EDFAs [5–10

5. M. A. Arbore, Y. Zhou, H. Thiele, J. Bromage, and L. Nelson, “S-band erbium-doped fiber amplifiers for WDM transmission between 1488 and 1508 nm,” in Proc. of OFC 2003, WK2 (2003).

] but also have a lower NF than theirs. For the S-band EDFAs using depressed cladding EDF, the cutoff efficiency is not as high as our fundamental-mode cutoff filters so that the C+L-band ASE can not be efficiently attenuated to make the S-band wavelengths obtain high gain efficiency and low NF. In contrast, in small signal regime, the low-noise S-band amplification in our EDFA is ascribed to the strong suppression of the forward and backward C+L-band ASE by the high cutoff efficiency fundamental-mode leakage loss filters to achieve the high population inversion in S-band. Nevertheless, under the fixed 980-nm pump power of 154 mW, the high population inversion in S-band may be easy to be deteriorated in the EDF when the signal input power gradually grows up. As previously mentioned, the 980-nm pump power can be significantly absorbed over short fiber distance to achieve a low NF [19

19. P. C. Becker, N. A. Olsson, and J. R. Simpson, Erbium-Doped Fiber Amplifiers: Fundamentals and Technology (Academic Press, New York, 1998), Chap. 6.

]. The 154 mW 980 nm pump power is enough to achieve high population inversion through the entire EDF in small signal regime. However, when the input signal power gradually grows up, the pump power is substantially depleted in the beginning of EDF due to the larger stimulated emission rate of signals. Thus, the population inversion is quickly deteriorated in the rest of EDF and which will decrease the net cross section in S-band much faster than in C-band [19

19. P. C. Becker, N. A. Olsson, and J. R. Simpson, Erbium-Doped Fiber Amplifiers: Fundamentals and Technology (Academic Press, New York, 1998), Chap. 6.

]. Consequently, the gain will be strongly robbed by the C+L-band ASE generated in the EDF between two adjacent filters and which makes the population inversion in S-band become even worse. Hence, the available optical gain is not sufficient to support the S-band signal to keep going amplified when the signal power gradually increase to beyond a certain value, say -10 dBm, where the gain is reduced to be around 15 dB while the NF goes up to 7 dB or so. Since a higher signal power can easily lowers the population inversion by increased stimulated emission, our double-pass EDFA is easier to saturate in contrast to the C-band EDFA [20

20. E. Desurvire, C. R. Giles, J. R. Simpson, and J. L. Zyskind, “Efficient erbium-doped fiber amplifier at a 1.53-μm wavelength with a high output saturation power,” Opt. Lett. 14,1266–1268 (1989). [CrossRef] [PubMed]

]. In order to achieve a higher saturation output power and a smaller NF for S-band signals, it is advantageous to uniformly distribute optical pump power over the entire EDF with distributed high-cutoff-efficiency fundamental-mode leakage loss by a bidirectional pumping scheme. For this EDFA under C+L-band operation at 40°C, the NF for 1549.6 nm is 16.59 dB which is much higher than that in single-pass configuration since the backward ASE can not be blocked and thus the NF is seriously downgraded.

Fig. 3(a) Amplification characteristics of the signals in S-band at 30.9°C and in C+L-bands at 40°C (RES: 0.1 nm). Pi and Po are input and output signal spectra, respectively.
Fig. 3(b) Gain and noise figure spectra under S-band operation at 1486.9 nm wavelength.

4. Conclusion

We have demonstrated a high-gain low-noise tunable double-pass EDFA over S- and C+L-bands by using high cutoff efficiency fundamental-mode leakage loss filters discretely located in a 16-m-long standard silica-based C-band EDF. These tunable filters can substantially suppress the C+L-band ASE to achieve S-band gain and thus the gain bandwidth of our EDFA can be temperature-tuned to cover S- and C+L-bands over 1490 ∼ 1610 nm. With a 980 nm pump power of 154 mW, the small signal gain at 1486.9 nm (S-band) can be above 37 dB whereas the noise figure can be as low as 4.84 dB. The highest gain in C- and L-bands can be greater than 40 dB and 17 dB, respectively. The saturation gain and saturation output power in S-band can be further improved by uniformly distributing optical pump power over the entire EDF with distributed high-cutoff-efficiency fundamental-mode leakage loss via a bidirectional pumping scheme. A high-bandwidth EDFA simultaneously covering S+C+L-band can be achieved based on a parallel EDF structure.

Acknowledgments

N. K. Chen acknowledges Prime Optical Fiber Corporation for the complimentary Er3+-doped fiber. This work was funded by grants from the Republic of China National Science Council (NSC 95-2752-E-009-009-PAE & NSC 95-2221-E-155-072) and National Chiao Tung University (MOE ATU Program).

References and links

1.

T. Kasamatsu, Y. Yano, and H. Sekita, “1.50-μm-band gain-shifted thulium-doped fiber amplifier with 1.05- and 1.56-μm dual wavelength pumping,” Opt. Lett. 24,1684–1686 (1999). [CrossRef]

2.

S. S. H. Yam, M. E. Marhic, Y. Akasaka, and L. G. Kazovsky, “Gain-clamped S-band discrete Raman amplifier,” Opt. Lett. 29,757–759 (2004). [CrossRef] [PubMed]

3.

S. K. Varshney, T. Fujisawa, K. Saitoh, and M. Koshiba, “Design and analysis of a broadband dispersion compensating photonic crystal fiber Raman amplifier operating in S-band,” Opt. Express 14,3528–3540 (2006). [CrossRef] [PubMed]

4.

M. A. Arbore, “Application of fundamental-mode cutoff for novel amplifiers and lasers,” in Proc. of OFC 2005, OFB4 (2005).

5.

M. A. Arbore, Y. Zhou, H. Thiele, J. Bromage, and L. Nelson, “S-band erbium-doped fiber amplifiers for WDM transmission between 1488 and 1508 nm,” in Proc. of OFC 2003, WK2 (2003).

6.

H. Ono, M. Yamada, and M. Shimizu, “S-band erbium,-doped fiber amplifiers with a multistage configuration-design, characterization, and gain tilt compensation,” J. Lightwave Technol. 21,2240–2246 (2003). [CrossRef]

7.

J. B. Rosolem, A. A. Juriollo, R. Arradi, A. D. Coral, J. C. R. F. Oliveira, and M. A. Romere, “All silica S-band double-pass erbium-doped fiber amplifier,” IEEE Photon. Technol. Lett. 17,1399–1401 (2005). [CrossRef]

8.

K. Thyagarajan and C. Kakkar, “S-band single-stage EDFA with 25-dB gain using distributed ASE suppression,” IEEE Photon. Technol. Lett. 16,2448–2450 (2004). [CrossRef]

9.

M. Foroni, F. Poli, A. Cucinotta, and S. Selleri, “S-band depressed-cladding erbium-doped fiber amplifier with double-pass configuration,” Opt. Lett. 31,3228–3230 (2006). [CrossRef] [PubMed]

10.

H. Ahmad, N. K. Saat, and S. W. Harun, “Effect of doped-fiber’s spooling on performance of S-band EDFA,” Laser Phys. Lett. 2,412–414 (2005). [CrossRef]

11.

S. Yoo, Y. Jung, J. Kim, J. W. Lee, and K. Oh, “W-type fiber design for application in U- and S-band amplifiers by controlling the LP01 mode long wavelength cut-off,” Opt. Commun. 11,332–345 (2005).

12.

S. Sudo, Optical Fiber Amplifiers: Materials, Devices, and Applications (Artech House, Boston, 1997), Chap. 2.

13.

T. Haruna, J. Iihara, K. Yamaguchi, Y. Saito, S. Ishikawa, M. Onishi, and T. Murata, “Local structure analyses around Er3+ in Er-doped fiber with Al-codoping,” Opt. Express 14,11036–11042 (2006). [CrossRef] [PubMed]

14.

M. Monerie, “Propagation in doubly clad single-mode fibers,” IEEE J. Quantum Electron. QE–18,535–542 (1982). [CrossRef]

15.

J. Kim, P. Dupriez, C. Codemard, J. Nilsson, and J. K. Sahu, “Suppression of stimulated Raman scattering in a high power Yb-doped fiber amplifier using a W-type core with fundamental mode cut-off,” Opt. Express 14,5103–5113 (2006). [CrossRef] [PubMed]

16.

N. K. Chen, S. Chi, and S. M. Tseng, “Wideband tunable fiber short-pass filter based on side-polished fiber with dispersive polymer overlay,” Opt. Lett. 29,2219–2221 (2004). [CrossRef] [PubMed]

17.

N. K. Chen, K. C. Hsu, S. Chi, and Y. Lai, “Tunable Er3+-doped fiber amplifiers covering S- and C + L-bands over 1490-1610 nm based on discrete fundamental-mode cutoff filters,” Opt. Lett. 31,2842–2844 (2006). [CrossRef] [PubMed]

18.

J. Villatoro, D. Monzon-Hernandez, and D. Luna-Moreno, “In-line tunable band-edge filter based on a single-mode tapered fiber coated with a dispersive material,” IEEE Photon. Technol. Lett.17,1665–1667 (2005). [CrossRef]

19.

P. C. Becker, N. A. Olsson, and J. R. Simpson, Erbium-Doped Fiber Amplifiers: Fundamentals and Technology (Academic Press, New York, 1998), Chap. 6.

20.

E. Desurvire, C. R. Giles, J. R. Simpson, and J. L. Zyskind, “Efficient erbium-doped fiber amplifier at a 1.53-μm wavelength with a high output saturation power,” Opt. Lett. 14,1266–1268 (1989). [CrossRef] [PubMed]

OCIS Codes
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
(060.2410) Fiber optics and optical communications : Fibers, erbium
(260.2030) Physical optics : Dispersion

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: January 4, 2007
Revised Manuscript: February 8, 2007
Manuscript Accepted: February 8, 2007
Published: February 19, 2007

Citation
Chi-Ming Hung, Nan-Kuang Chen, Yinchieh Lai, and Sien Chi, "Double-pass high-gain low-noise EDFA over S- and C+L-bands by tunable fundamental-mode leakage loss," Opt. Express 15, 1454-1460 (2007)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-4-1454


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References

  1. T. Kasamatsu, Y. Yano, and H. Sekita, "1.50-μm-band gain-shifted thulium-doped fiber amplifier with 1.05- and 1.56-μm dual wavelength pumping," Opt. Lett. 24, 1684-1686 (1999). [CrossRef]
  2. S. S. H. Yam, M. E. Marhic, Y. Akasaka, and L. G. Kazovsky, "Gain-clamped S-band discrete Raman amplifier," Opt. Lett. 29, 757-759 (2004). [CrossRef] [PubMed]
  3. S. K. Varshney, T. Fujisawa, K. Saitoh, and M. Koshiba, "Design and analysis of a broadband dispersion compensating photonic crystal fiber Raman amplifier operating in S-band," Opt. Express 14, 3528-3540 (2006). [CrossRef] [PubMed]
  4. M. A. Arbore, "Application of fundamental-mode cutoff for novel amplifiers and lasers," in Proc. of OFC 2005, OFB4 (2005).
  5. M. A. Arbore, Y. Zhou, H. Thiele, J. Bromage, and L. Nelson, "S-band erbium-doped fiber amplifiers for WDM transmission between 1488 and 1508 nm," in Proc. of OFC 2003, WK2 (2003).
  6. H. Ono, M. Yamada, and M. Shimizu, "S-band erbium,-doped fiber amplifiers with a multistage configuration−design, characterization, and gain tilt compensation," J. Lightwave Technol. 21, 2240-2246 (2003). [CrossRef]
  7. J. B. Rosolem, A. A. Juriollo, R. Arradi, A. D. Coral, J. C. R. F. Oliveira, and M. A. Romere, "All silica S-band double-pass erbium-doped fiber amplifier," IEEE Photon. Technol. Lett. 17, 1399-1401 (2005). [CrossRef]
  8. K. Thyagarajan and C. Kakkar, "S-band single-stage EDFA with 25-dB gain using distributed ASE suppression," IEEE Photon. Technol. Lett. 16, 2448-2450 (2004). [CrossRef]
  9. M. Foroni, F. Poli, A. Cucinotta, and S. Selleri, "S-band depressed-cladding erbium-doped fiber amplifier with double-pass configuration," Opt. Lett. 31, 3228-3230 (2006). [CrossRef] [PubMed]
  10. H. Ahmad, N. K. Saat, and S. W. Harun, "Effect of doped-fiber’s spooling on performance of S-band EDFA," Laser Phys. Lett. 2, 412-414 (2005). [CrossRef]
  11. S. Yoo, Y. Jung, J. Kim, J. W. Lee and K. Oh, "W-type fiber design for application in U- and S-band amplifiers by controlling the LP01 mode long wavelength cut-off," Opt. Commun. 11, 332-345 (2005).
  12. S. Sudo, Optical Fiber Amplifiers: Materials, Devices, and Applications (Artech House, Boston, 1997), Chap. 2.
  13. T. Haruna, J. Iihara, K. Yamaguchi, Y. Saito, S. Ishikawa, M. Onishi, and T. Murata, "Local structure analyses around Er3+ in Er-doped fiber with Al-codoping," Opt. Express 14, 11036-11042 (2006). [CrossRef] [PubMed]
  14. M. Monerie, "Propagation in doubly clad single-mode fibers," IEEE J. Quantum Electron. QE-18, 535-542 (1982). [CrossRef]
  15. J. Kim, P. Dupriez, C. Codemard, J. Nilsson, and J. K. Sahu, "Suppression of stimulated Raman scattering in a high power Yb-doped fiber amplifier using a W-type core with fundamental mode cut-off," Opt. Express 14, 5103-5113 (2006). [CrossRef] [PubMed]
  16. N. K. Chen, S. Chi, and S. M. Tseng, "Wideband tunable fiber short-pass filter based on side-polished fiber with dispersive polymer overlay," Opt. Lett. 29, 2219-2221 (2004). [CrossRef] [PubMed]
  17. N. K. Chen, K. C. Hsu, S. Chi, and Y. Lai, "Tunable Er3+-doped fiber amplifiers covering S- and C + L-bands over 1490-1610 nm based on discrete fundamental-mode cutoff filters," Opt. Lett. 31, 2842-2844 (2006). [CrossRef] [PubMed]
  18. J. Villatoro, D. Monzon-Hernandez, and D. Luna-Moreno, "In-line tunable band-edge filter based on a single-mode tapered fiber coated with a dispersive material," IEEE Photon. Technol. Lett. 17, 1665-1667 (2005). [CrossRef]
  19. P. C. Becker, N. A. Olsson, and J. R. Simpson, Erbium-Doped Fiber Amplifiers: Fundamentals and Technology (Academic Press, New York, 1998), Chap. 6.
  20. E. Desurvire. C. R. Giles, J. R. Simpson, and J. L. Zyskind, "Efficient erbium-doped fiber amplifier at a 1.53-μm wavelength with a high output saturation power," Opt. Lett. 14, 1266-1268 (1989). [CrossRef] [PubMed]

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