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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 14, Iss. 3 — Feb. 6, 2006
  • pp: 1113–1118
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Multiwavelength erbium-doped fiber laser based on inhomogeneous loss mechanism by use of a highly nonlinear fiber and a Fabry-Perot filter

Shilong Pan, Caiyun Lou, and Yizi Gao  »View Author Affiliations


Optics Express, Vol. 14, Issue 3, pp. 1113-1118 (2006)
http://dx.doi.org/10.1364/OE.14.001113


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Abstract

We demonstrated a simple technique to obtain stable room temperature multiwavelength lasing in an erbium-doped fiber laser by the inhomogeneous loss mechanism. Successful reduction of the cross-gain saturation in erbium-doped fiber was achieved by incorporating a section of highly nonlinear fiber (HNLF) and a narrowband Fabry-Perot filter (FPF) in the laser cavity. More than 70 wavelengths simultaneous lasing were observed with the same frequency space of 25GHz. The laser had a total output power of ∼3.2dBm, a bandwidth of 0.012nm (∼1.5GHz) and a signal-to-spontaneous-noise ratio of ∼44dB. The total output power can be further increased to more than 190mW by moving the output port right after the EDFA.

© 2006 Optical Society of America

1. Introduction

Multiwavelength fiber lasers are of great interest for their potential applications in optical communications, fiber-optic sensors, optical instrumentation, and microwave photonic systems. Both semiconductor optical amplifiers (SOA) [1

1. H. Chen, “Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier,” Opt. Lett. 30, 619–621 (2005). [CrossRef] [PubMed]

] and erbium-doped fiber amplifiers (EDFA) [2–6

2. N. Park and P. F. Wysocki, “24-line multiwavelength operation of erbium-doped fiber-ring laser,” IEEE Photon. Technol. Lett. 8, 1459–1461 (1996). [CrossRef]

] have been used for generation of multiwavelength fiber laser. Compared to SOA-based multiwavelength fiber lasers, multiwavelength lasers with EDFA have advantages in their higher saturated power, lower polarization-dependent gain (PDG) and flatter gain spectrum. The main challenges for erbium-doped fiber (EDF) ring lasers to achieve stable multiwavelength lasing at room temperature are the strong homogeneous line broadening and the cross-gain saturation. Previously, several approaches have been proposed. Cooling the EDF to 77K by liquid nitrogen can suppress the homogenous line broadening and the cross-gain saturation [2

2. N. Park and P. F. Wysocki, “24-line multiwavelength operation of erbium-doped fiber-ring laser,” IEEE Photon. Technol. Lett. 8, 1459–1461 (1996). [CrossRef]

], but this technique is impractical in many applications. To obtain room temperature multiwavelength lasing, a specially designed erbium-doped two core fiber has been used to provide inhomogeneous gain through macroscopic spatial hole-burning [3

3. O. Graydon, W. H. Loh, R. I. Laming, and L. Dong, “Triple-frequency operation of an Er-doped twincore fiber loop laser,” IEEE Photon. Technol. Lett. 8, 63–65 (1996). [CrossRef]

]. Recently, multiwavelength lasing has been demonstrated by use of a frequency shifter or a phase modulator [4–6

4. A. Bellemare, M. Karasek, M. Rochette, S. Larochelle, and M. Tetu, “Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid,” J. Lightwave Technol. 18, 825–831 (2000). [CrossRef]

]. Other methods, such as optical feedback and nonlinear gain in optical fiber have also been exploited [7–8

7. Y. Zhao, C. Shu, S. P. Li, H. Ding, and K. T. Chiang, “Multiple wavelength operation of a unidirectional Er-doped fiber ring laser with optical feedback,” in Proc. Tech. Dig. Conf. Laser and Electro-Optics (CLEO’97), Paper CThL65, p. 396 (1997).

]. However, some of these designs require many optical components and some are unstable. More recently, multiwavelength lasing was reported by incorporating a highly nonlinear fiber (HNLF) in the ring cavity [9

9. S. Yamashita and Y. Inoue, “Multiwavelength Er-Doped Fiber Ring Laser Incorporating Highly Nonlinear Fiber,” Jpn. J. Appl. Phys. , Part 2 44, L1080–L1081 (2005) [CrossRef]

]. Based on the self-phase modulation and the four-wave mixing (FWM) in the HNLF, 488 channels with a wavelength spacing of 10GHz were obtained. However, the signal-to-spontaneous-noise ratio of the laser was below 20dB, which was not suitable for some applications. Meanwhile, X. Liu et al. [10

10. X. Liu, X. Yang, F. Lu, J. Ng, X. Zhou, and C. Lu, “Stable and uniform dual-wavelength erbium-doped fiber laser based on fiber Bragg gratings and photonic crystal fiber,” Opt. Express 13, 142–147 (2005) http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-1-142 [CrossRef] [PubMed]

] and A. Zhang et al. [11

11. A. Zhang, H. Liu, M. Demokan, and H. Tam, “Stable and broad bandwidth multiwavelength fiber ring laser incorporating a highly nonlinear photonic crystal fiber,” IEEE Photon. Technol. Lett. 17, 2535–2537 (2005). [CrossRef]

] proposed multiwavelength fiber ring lasers by adding a length of highly nonlinear photonic crystal fiber (HN-PCF) into the ring cavity. The HN-PCF has a flat and low dispersion profile over a wide bandwidth, and therefore generates an FWM-induced dynamic gain flattening mechanism in the ring cavity, which further enables the multiwavelength operation.

2. Experiment setup

A schematic of the experimental setup is shown in Fig. 1(a). The gain of the fiber laser was provided by an erbium-doped fiber amplifier (EDFA), whose maximum output power was ∼33dBm. A polarization independent isolator was used to ensure the unidirectional cavity. A FPF with a wavelength space of 0.2nm (25GHz) and a linewidth of 0.02nm served as a wavelength selector. Fig. 1(b) depicts the transmission spectrum of the FPF, which was obtained by an ASE source and an optical spectrum analyzer (ANDO AQ6317, resolution 0.01nm). A section of 1km commercial HNLF was inserted in the laser cavity. The zero-dispersion wavelength of the HNLF was ∼1555.5nm, and the dispersion slope, nonlinear coefficient were 0.018ps/(nm2∙km) and 10/(W∙km), respectively. The laser output was extracted from the cavity by a 10/90 fiber coupler, with which 90% power was fed back into the EDFA.

Fig. 1. (a) Setup for the multiwavelength fiber laser. C, 10/90 coupler; I, optical isolator; OSA, optical spectrum analyzer; BPF, optical bandpass filter. (b) Transmission spectrum of the FPF

3. Results and discussion

Fig. 2. Linewidth (FWHM) as a function of the optical power that injected into the HNLF.
Fig. 3. Three-dimensional plot of measured spectral evolution of the optical output versus the power that injected into the HNLF. OSA Resolution: 0.2nm.

Setting the pump power of the EDFA at its maximum value, the optical power that injected into the HNLF was estimated to be 1.9 W. The flat area of the spectrum is over 14nm, as shown in Fig. 4. Different from Fig. 3, Fig. 4 is captured by setting the resolution of the OSA at 0.01nm. From Fig. 4(a), over 70 wavelengths simultaneous lasing was observed. They had the same frequency separation space as that of the FPF (25GHz). The laser had a linewidth of ∼0.012nm (1.5GHz) and a signal-to-spontaneous-noise ratio of ∼44dB. The total output power was 3.2dBm. It should be emphasized that the output power can be increased to more than 190mW by moving the 90/10 coupler right after the EDFA. For a clear understanding of the fine structure of the laser output spectrum, Fig. 4(b) gives the expanded laser spectrum of Fig. 4(a). As shown, almost no power variation appears between these lasing wavelengths.

To figure out the role of the HNLF and FPF, we performed the same measurement for the laser configuration without incorporating the HNLF or FPF. For the configuration without the HNLF, multiple wavelengths (less than 10) lasing could also be obtained by careful gain equalization. However, when we slightly dither the fiber, some lasing wavelengths would fade due to their failure in the gain competition. For the configuration without the FPF, the result was the same with that in a recent work by J. H. Lee et al. [16

16. J. H. Lee, Y. Takushima, and K. Kikuchi, “Continuous-wave supercontinuum laser based on an erbium-doped fiber ring cavity incorporating a highly nonlinear optical fiber,” Opt. Lett. 30, 619–621 (2005). [CrossRef]

]. We confirmed the continuous-wave supercontinuum generation in an erbium-doped fiber laser that incorporating a HNLF in the ring cavity. The modulation instability and stimulated Raman scattering mechanism for the generation of the continuous-wave supercontinuum may also help to the generation of the multiwavelength laser in our experimental setup.

Fig. 4. (a) Laser spectrum with a span of 20nm. (b) Expanded laser spectrum. OSA Resolution: 0.01nm.

Finally, we quantitatively investigated the long–term stability of the output spectrum. We observed the output spectrum every 10 min for 2 hour while the pump power was set to a maximum value of the EDFA. The repeated scans are shown in Fig. 5. No significant spectral fluctuations were observed. The wavelengths shifted within 0.003 nm and the relative change of amplitudes was smaller than 0.05dB, which were at the resolution limit of our OSA.

Fig. 5. Repeated scans of the output optical spectrum. The time interval of each scan was 10 min.

4. Conclusion

In conclusion, we have experimentally demonstrated a multiwavelength erbium-doped fiber laser based on inhomogeneous loss mechanism by incorporating a section of commercial HNLF and a narrowband FPF in the ring cavity. The proposed scheme can successfully reduce the cross-gain saturation in erbium-doped fiber laser and enable the multiwavelength operation. Using the method, over 70 wavelengths simultaneous lasing with a frequency space of 25GHz was achieved. The laser had a total output power of ∼3.2dBm, a bandwidth of 0.012nm (∼1.5GHz) and a signal-to-spontaneous-noise ratio of ∼44dB. The lasing states were observed to be very stable. The total output power can be further increased to more than 190mW. We believe this simple multiwavelength fiber laser is practical for a lot of applications, such as the optical communications, optical testing and measurement and microwave photonic systems.

Acknowledgments

The authors gratefully acknowledge support from the National Natural Science Foundation of China (60444008904010247, 60577033)

Reference

1.

H. Chen, “Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier,” Opt. Lett. 30, 619–621 (2005). [CrossRef] [PubMed]

2.

N. Park and P. F. Wysocki, “24-line multiwavelength operation of erbium-doped fiber-ring laser,” IEEE Photon. Technol. Lett. 8, 1459–1461 (1996). [CrossRef]

3.

O. Graydon, W. H. Loh, R. I. Laming, and L. Dong, “Triple-frequency operation of an Er-doped twincore fiber loop laser,” IEEE Photon. Technol. Lett. 8, 63–65 (1996). [CrossRef]

4.

A. Bellemare, M. Karasek, M. Rochette, S. Larochelle, and M. Tetu, “Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid,” J. Lightwave Technol. 18, 825–831 (2000). [CrossRef]

5.

K. Zhou, D. Zhou, F. Dong, and N. Q. Ngo, “Room-temperature multi-wavelength erbium-doped fiber ring laser employing sinusoidal phase-modulation feedback,” Opt. Lett. 28, 893–895 (2003). [CrossRef] [PubMed]

6.

J. Yao, J. P. Yao, Z. Deng, and J. Liu, “Investigation of Room-Temperature Multiwavelength Fiber-Ring Laser That Incorporates an SOA-Based Phase Modulator in the Laser Cavity,” J. Lightwave Technol. 23, 2484–2489 (2005). [CrossRef]

7.

Y. Zhao, C. Shu, S. P. Li, H. Ding, and K. T. Chiang, “Multiple wavelength operation of a unidirectional Er-doped fiber ring laser with optical feedback,” in Proc. Tech. Dig. Conf. Laser and Electro-Optics (CLEO’97), Paper CThL65, p. 396 (1997).

8.

G. J. Cowle and D. Y. Stepanov, “Multiple wavelength generation with Brillouin/erbium fiber lasers,” IEEE Photon. Technol. Lett. 8, 1465–1467 (1996). [CrossRef]

9.

S. Yamashita and Y. Inoue, “Multiwavelength Er-Doped Fiber Ring Laser Incorporating Highly Nonlinear Fiber,” Jpn. J. Appl. Phys. , Part 2 44, L1080–L1081 (2005) [CrossRef]

10.

X. Liu, X. Yang, F. Lu, J. Ng, X. Zhou, and C. Lu, “Stable and uniform dual-wavelength erbium-doped fiber laser based on fiber Bragg gratings and photonic crystal fiber,” Opt. Express 13, 142–147 (2005) http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-1-142 [CrossRef] [PubMed]

11.

A. Zhang, H. Liu, M. Demokan, and H. Tam, “Stable and broad bandwidth multiwavelength fiber ring laser incorporating a highly nonlinear photonic crystal fiber,” IEEE Photon. Technol. Lett. 17, 2535–2537 (2005). [CrossRef]

12.

Q. Wang, Y. Wang, W. Zhang, X. Feng, X. Liu, and B. Zhou, “Inhomogeneous loss mechanism in multiwavelength fiber Raman ring lasers”, Opt. Lett. 30, 952–954 (2005). [CrossRef] [PubMed]

13.

M. J. F. Digonnet (Ed.), Rare-Earth Doped Fiber Lasers and Amplifiers, 2nd ed. (Marcel Dekker, New York, 2001).

14.

N. Park, J. W. Dawson, K. J. Vahala, and C. Miller, “All fiber, low threshold, widely tunable single-frequency, erbium-doped fiber ring laser with a tandem fiber Fabry-Perot filter,” Appl. Phys. Lett. 59, 2369–2371 (1991). [CrossRef]

15.

V. Roy, M. Piché, F. Babin, and G. Schinn, “Nonlinear wave mixing in a multilongitudinal-mode erbium-doped fiber laser,” Opt. Express 13, 6791–6797 (2005) http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-18-6791 [CrossRef] [PubMed]

16.

J. H. Lee, Y. Takushima, and K. Kikuchi, “Continuous-wave supercontinuum laser based on an erbium-doped fiber ring cavity incorporating a highly nonlinear optical fiber,” Opt. Lett. 30, 619–621 (2005). [CrossRef]

OCIS Codes
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
(140.3510) Lasers and laser optics : Lasers, fiber
(190.4370) Nonlinear optics : Nonlinear optics, fibers

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: December 5, 2005
Revised Manuscript: January 20, 2006
Manuscript Accepted: January 20, 2006
Published: February 6, 2006

Citation
Shilong Pan, Caiyun Lou, and Yizi Gao, "Multiwavelength erbium-doped fiber laser based on inhomogeneous loss mechanism by use of a highly nonlinear fiber and a Fabry-Perot filter," Opt. Express 14, 1113-1118 (2006)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-3-1113


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References

  1. H. Chen, "Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier," Opt. Lett. 30, 619-621 (2005). [CrossRef] [PubMed]
  2. N. Park and P. F. Wysocki, "24-line multiwavelength operation of erbium-doped fiber-ring laser," IEEE Photon. Technol. Lett. 8, 1459-1461 (1996). [CrossRef]
  3. O. Graydon, W. H. Loh, R. I. Laming, and L. Dong, "Triple-frequency operation of an Er-doped twincore fiber loop laser," IEEE Photon. Technol. Lett. 8, 63-65 (1996). [CrossRef]
  4. A. Bellemare, M. Karasek, M. Rochette, S. Larochelle, and M. Tetu,"Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid," J. Lightwave Technol. 18, 825-831 (2000). [CrossRef]
  5. K. Zhou, D. Zhou, F. Dong, and N. Q. Ngo, "Room-temperature multi-wavelength erbium-doped fiber ring laser employing sinusoidal phase-modulation feedback," Opt. Lett. 28, 893-895 (2003). [CrossRef] [PubMed]
  6. J. Yao, J. P. Yao, Z. Deng, and J. Liu, "Investigation of Room-Temperature Multiwavelength Fiber-Ring Laser That Incorporates an SOA-Based Phase Modulator in the Laser Cavity," J. Lightwave Technol. 23, 2484-2489 (2005). [CrossRef]
  7. Y. Zhao, C. Shu, S. P. Li, H. Ding, and K. T. Chiang, "Multiple wavelength operation of a unidirectional Er-doped fiber ring laser with optical feedback," in Proc. Tech. Dig. Conf. Laser and Electro-Optics (CLEO’97), Paper CThL65, p. 396 (1997).
  8. G. J. Cowle and D. Y. Stepanov, "Multiple wavelength generation with Brillouin/erbium fiber lasers," IEEE Photon. Technol. Lett. 8, 1465-1467 (1996). [CrossRef]
  9. S. Yamashita and Y. Inoue, "Multiwavelength Er-Doped Fiber Ring Laser Incorporating Highly Nonlinear Fiber," Jpn. J. Appl. Phys., Part 2 44, L1080-L1081 (2005) [CrossRef]
  10. X. Liu, X. Yang, F. Lu, J. Ng, X. Zhou, and C. Lu, "Stable and uniform dual-wavelength erbium-doped fiber laser based on fiber Bragg gratings and photonic crystal fiber," Opt. Express 13, 142-147 (2005) http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-1-142 [CrossRef] [PubMed]
  11. A. Zhang, H. Liu, M. Demokan, and H. Tam, "Stable and broad bandwidth multiwavelength fiber ring laser incorporating a highly nonlinear photonic crystal fiber," IEEE Photon. Technol. Lett. 17, 2535-2537 (2005). [CrossRef]
  12. Q. Wang, Y. Wang, W. Zhang, X. Feng, X. Liu, and B. Zhou, "Inhomogeneous loss mechanism in multiwavelength fiber Raman ring lasers," Opt. Lett. 30, 952-954 (2005). [CrossRef] [PubMed]
  13. M. J. F. Digonnet (Ed.), Rare-Earth Doped Fiber Lasers and Amplifiers, 2nd ed. (Marcel Dekker, New York, 2001).
  14. N. Park, J. W. Dawson, K. J. Vahala, and C. Miller, "All fiber, low threshold, widely tunable single-frequency, erbium-doped fiber ring laser with a tandem fiber Fabry-Perot filter," Appl. Phys. Lett. 59, 2369-2371 (1991). [CrossRef]
  15. V. Roy, M. Piché, F. Babin, and G. Schinn, "Nonlinear wave mixing in a multilongitudinal-mode erbium-doped fiber laser," Opt. Express 13, 6791-6797 (2005) http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-18-6791 [CrossRef] [PubMed]
  16. J. H. Lee, Y. Takushima, and K. Kikuchi, "Continuous-wave supercontinuum laser based on an erbium-doped fiber ring cavity incorporating a highly nonlinear optical fiber," Opt. Lett. 30, 619-621 (2005). [CrossRef]

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