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Multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain
Optics Communications 338 (2015) 336–339
Contents lists available at ScienceDirect
Optics Communications journal homepage: www.elsevier.com/locate/optcom
Multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain Yiyang Luo, Li Xia n, Qizhen Sun, Wei Li, Yanli Ran, Deming Liu Wuhan National Laboratory for Optoelectronics, National Engineering Laboratory for Next Generation Internet Access System, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
art ic l e i nf o
a b s t r a c t
Article history: Received 28 September 2014 Accepted 30 October 2014 Available online 6 November 2014
In this paper, a multi-wavelength fiber laser based on self-seed light amplification and wavelengthdependent gain is proposed and demonstrated. A pumped erbium-doped fiber (EDF) in the linear cavity acts as the seed light source, which is also conducive to the gain equalization. A high power erbiumdoped fiber amplifier (EDFA) is deployed for self-seed amplification, and a highly nonlinear fiber (HNLF) is incorporated in the ring cavity to alleviate the mode competition induced by the homogeneous gain broadening of EDF. In the experiments, 25-wavelength operation within 0.5 dB uniformity is achieved with the extinction ratio of 42 dB using 500 m HNLF, and 38-wavelength operation within 3 dB uniformity is obtained with the extinction ratio of 35 dB using 1000 m HNLF. Our proposed laser has more lasing wavelengths with a better uniformity and stability. & Elsevier B.V. All rights reserved.
Keywords: Multi-wavelength fiber laser Erbium-doped fiber High nonlinear effect Wavelength-dependent gain
1. Introduction Multi-wavelength erbium-doped fiber laser (EDFL) has been extensively investigated for its versatile applications in dense wavelength-division-multiplexing (DWDM) communication system, fiber sensing, optical signal processing, and optical instrumentation. However, EDFL suffers from strong mode competition owing to the homogeneous gain broadening of the EDF at room temperature. In order to achieve stable multi-wavelength operation, various technologies have been applied to overcome the mode competition. To my best knowledge, these include the use of semiconductor optical amplification (SOA) [1–3], the introduction of fiber Raman or Brillouin amplification [4–6], cooling EDF in liquid-nitrogen temperature [7], inducing a frequency shifter [8– 10], and the utilization of nonlinear effect induced by the HNLF [11–13]. Yang et al. proposed a multi-wavelength ring fiber laser incorporated with a section of HNLF to alleviate the mode competition [14]. A stabilized multi-wavelength operation was obtained, but the envelope of the spectrum was not smooth, and the uniformity between adjacent wavelengths can be optimized further.
n
Corresponding author. E-mail address: [email protected] (L. Xia).
http://dx.doi.org/10.1016/j.optcom.2014.10.066 0030-4018/& Elsevier B.V. All rights reserved.
Zhang et al. presented a two Fabry–Perot laser diodes (FP-LDs) based multi-wavelength fiber laser [15]. Only 20-wavelength operation and non-uniformity of the spectrum impeded its applications. Moreover, the power fluctuation of 0.4 dB needed to be improved. In this letter, a multi-wavelength fiber laser with a pumped EDF and a section of HNLF is proposed and demonstrated. A linear cavity consisting of a pumped EDF and a broadband reflecting mirror is ingeniously incorporated with a conventional ring cavity. The operation principle is elucidated in detail on account of these two factors: self-seed light amplification and wavelength-dependent gain. Experimental verification is implemented to demonstrate this scheme and evaluate the performance of proposed multi-wavelength fiber laser.
2. Experimental setup and operation principle The schematic configuration of experimental setup is shown in Fig. 1. The optical gain are provided by a high power EDFA, and a 3.5 m-long EDF pumped by the 980 nm laser diode (LD), which is coupled into the EDF by a 980/1550 nm wavelength division multiplexing (WDM). In the ring cavity, a FFPF (Micron Optics International) with a free spectrum range (FSR) of 25 GHz is utilized as a narrow band comb filter, and an isolator is used for unidirectional operation. A section of HNLF induces the nonlinear effect of four wave mixing (FWM) to alleviate the mode
Y. Luo et al. / Optics Communications 338 (2015) 336–339
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Fig. 3. Multi-wavelength laser output spectrum with 500 m HNLF.
Fig. 1. Schematic configuration of the experimental setup.
Fig. 4. Multi-wavelength laser output spectrum with 1000 m HNLF.
Fig. 2. Transmission spectrum of the FFPF.
competition, and a polarization controller (PC) ensures appropriate polarization. A 3-ports optical circulator guides the light to propagate in right circular direction. A 3 dB optical coupler acts as an output port, which is also the connection between the ring cavity and the linear cavity. In the other end of the linear cavity, a Faraday rotator mirror (FRM) is utilized as a broadband reflecting mirror with 0.45 dB insertion loss. An optical spectrum analyzer (OSA, YOKOGAWA AQ6370, resolution of 0.02 nm) is engaged to observe the output optical spectrum. As shown in Fig. 2, the transmission spectrum of the FFPF utilized in our experiment is observed via a broadband light source and an OSA. The extinction ratio is about 20 dB with the wavelength spacing of 0.2 nm. The operation principle of the proposed fiber laser is shown as follows. The seed light generated by the 3.5 m-long pumped EDF is injected into the ring cavity consisting of a high power EDFA and HNLF, which is regarded as a traditional multi-wavelength oscillator. The seed light is amplified by this oscillating system.
Meanwhile, the mode competition is alleviated by the nonlinear effect of FWM in HNLF. This process is described as self-seed light amplification. Then, through adjusting the PC to appropriate polarization, the output light from the ring cavity can experience wavelength-dependent optical amplification introduced by the pumped EDF. It is defined as wavelength-dependent gain. Moreover, the amplifying capability of the pumped EDF is weaker than EDFA. Therefore, it primarily plays roles in gain equalization for each lasing wavelength also is an auxiliary for the boosted EDFA to slightly enhance the nonlinear effect.
3. Experimental results and discussion To start with, the experiment is conducted with a section of 500 m HNLF. As shown in Fig. 3, through adjusting the PC and the pump power of 980 nm LD, the output spectrum of 25 wavelengths within 0.5 dB uniformity is achieved from port A. The extinction ratio and line width of each wavelength are measured to be 42 dB and 0.016 nm, respectively. The wavelength spacing is 0.2 nm, which is in accordance with the transmission spectrum of the FFPF. It should be noted that the alleviation of the
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Y. Luo et al. / Optics Communications 338 (2015) 336–339
Fig. 5. Multi-wavelength laser output spectrum with 1000 m HNLF corresponding to (a) unpumped EDF, and (b) pumped EDF.
mode competition and the broadening of the spectrum are induced by the HNLF, while the uniform power distribution of the wavelengths principally results from the pumped EDF and the adjustment of the PC, which provide the wavelength-dependent gain. Afterwards, a section of 1000 m HNLF is inserted in the ring cavity instead of the 500 m HNLF to reveal the influence of the nonlinear effect on operation performance of the multi-wavelength fiber laser. As shown in Fig. 4, the output spectrum with 38 wavelengths within 3 dB uniformity is achieved. The extinction ratio is a little more than 35 dB with the wavelength spacing of 0.2 nm. Compared with the output spectrum shown in Fig. 3, the spectrum is broadened in the experiment with 1000 m HNLF. The reason is related to the stronger nonlinear effect induced by the longer HNLF. More oscillating wavelengths can be generated due to the FWM between adjacent wavelengths. Lower extinction ratio of each wavelength may be the consequence of the high output power of the EDFA, which gives rise to the stronger nonlinear effect and a powerful amplified spontaneous emission (ASE) background noise, simultaneously. Thus it can be seen that it is a tradeoff between the broadening of the multi-wavelength spectrum and the extinction ratio in our experiment. For comparison, the output spectrum corresponding to the unpumped EDF is shown in Fig. 5(a), which is in contrast to the experiment with pumped EDF shown in Fig. 5(b). The experiment is conducted with 1000 m HNLF. In this case, the unpumped EDF just acts as a saturable absorber instead of the wavelength-dependent gain medium. Meanwhile, its auxiliary function of nonlinear effect enhancement loses. Consequently, non-uniform power distribution of the wavelengths is obtained. It is evident that the proposed scheme optimizes the uniformity of the lasing wavelengths. For practical applications, the stability of the multi-wavelength fiber laser is a crucial factor. On account of the well packaged FFPF and temperature control, the wavelength drift can be neglected to some extent. Accordingly, the output power fluctuation is investigated through the laser spectrum. As shown in Figs. 6(a) and (b), 5 lasing wavelengths are chosen to estimate the power fluctuations corresponding to the two cases of 500 m and 1000 m
Fig. 6. Power fluctuations of 5 lasing wavelengths with (a) 500 m HNLF, (b) 1000 m HNLF.
Y. Luo et al. / Optics Communications 338 (2015) 336–339
HNLFs, respectively. It is measured with the time interval of 5 min during an hour. The fiber laser with 500 m HNLF possesses a power fluctuation of less than 0.3 dB. Moreover, the case of 1000 m HNLF exhibits an outstanding stability with the power fluctuation of less than 0.08 dB. The longer HNLF contributes to the optimization of the stability, due to stronger nonlinear effect of FWM, which enhances the alleviation of the mode competition induced by the homogeneous gain broadening. At the same time, the mode hopping can be suppressed further. Consequently, a more stable multiwavelength operation is achieved with longer HNLF. Finally, it should be noted that the utilization of the pumped EDF is worthy in consideration of the operation performance optimization. Compared to the previous work mentioned in [14,15], the multi-wavelength fiber laser proposed in this letter possesses better uniformity of lasing wavelengths and more stable output optical power due to the mechanism of self-seed light amplification and wavelength-dependent gain.
4. Conclusions In conclusion, a stable multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain is presented. The pumped EDF not only acts as the seed light source, but also provides the wavelength-dependent gain to optimize the multi-wavelength uniformity. The HNLF is utilized to alleviate the mode competition induced by the homogeneous gain broadening of the EDF and the FFPF is inserted in the ring cavity as the wavelength selection component. In the experiment, multi-wavelength operations are achieved with the wavelength spacing of 0.2 nm using different lengths of HNLFs. The influences of the nonlinear effect on the spectral broadening and stability of the multi-wavelength operation are analyzed. In consideration of the good operation performance of the proposed multi-wavelength fiber laser, we believe that it would attract great attentions in potential applications.
Acknowledgments This work is supported by sub-Project of the Major Program of the National Natural Science Foundation of China (No. 61290315), the National Natural Science Foundation of China (No. 61275004), and the National High Technology Research and Development Program of China (863 Program) (No. 2012AA041203).
339
References [1] H. Chen, Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier, Opt. Lett. 30 (2005) 619–621. [2] K. Lee, S.D. Lim, C.H. Kim, J.H. Lee, Y.-G. Han, S.B. Lee, Noise reduction in multiwavelength SOA-based ring laser by coupled dual cavities for WDM applications, J. Lightwave Technol. 28 (2010) 739–745. [3] Z. Luo, W.-D. Zhong, Z. Cai, C. Ye, Y. Wen, High-performance SOA-based multiwavelength fiber lasers incorporating a novel double-pass waveguide-based MZI, Appl. Phys. B 96 (2009) 29–38. [4] S. Qin, D. Chen, Y. Tang, S. He, Stable and uniform multi-wavelength fiber laser based on hybrid Raman and erbium-doped fiber gains, Opt. Express 14 (2006) 10522–10527. [5] Y. Shee, M. Al-Mansoori, A. Ismail, S. Hitam, M. Mahdi, Multiwavelength Brillouin-erbium fiber laser with double-brillouin-frequency spacing, Opt. Express 19 (2011) 1699–1706. [6] A. Pinto, O. Frazão, J. Santos, M. Lopez-Amo, Multiwavelength fiber laser based on a photonic crystal fiber loop mirror with cooperative Rayleigh scattering, Appl. Phys. B 99 (2010) 391–395. [7] R. Hayashi, S. Yamashita, T. Saida, 16-wavelength 10-GHz actively mode-locked fiber laser with demultiplexed outputs anchored on the ITU-T grid,, Photon. Technol. Lett. IEEE 15 (2003) 1692–1694. [8] K. Zhou, D. Zhou, F. Dong, N.Q. Ngo, Room-temperature multiwavelength erbium-doped fiber ring laser employing sinusoidal phase-modulation feedback, Opt. Lett. 28 (2003) 893–895. [9] S.K. Kim, M.J. Chu, J.H. Lee, Wideband multiwavelength erbium-doped fiber ring laser with frequency shifted feedback, Opt. Commun. 190 (2001) 291–302. [10] J. Yao, J. Yao, Z. Deng, J. Liu, Multiwavelength erbium-doped fiber ring laser incorporating an SOA-based phase modulator,, Photon. Technol. Lett. IEEE 17 (2005) 756–758. [11] A. Zhang, H. Liu, M. Demokan, H. Tam, Stable and broad bandwidth multiwavelength fiber ring laser incorporating a highly nonlinear photonic crystal fiber,, Photon. Technol. Lett. IEEE 17 (2005) 2535–2537. [12] S. Yamashita, Y. Inoue, Multiwavelength Er-doped fiber ring laser incorporating highly nonlinear fiber, Jpn. J. Appl. Phys. 44 (2005) L1080. [13] H. Ahmad, R. Parvizi, K. Dimyati, M. Tamjis, S. Harun, FWM-based multi-wavelength erbium-doped fiber laser using Bi-EDF, Laser Phys. 20 (2010) 1414–1417. [14] C. Yang, L. Xia, Y. Wang, D. Liu, Stabilized 51-wavelength erbium-doped fiber ring laser based on high nonlinear fiber, Opt. Commun. (2014). [15] A. Zhang, Y. Jin, X. Feng, J. Zhou, Z. Li, B.-O. Guan, Multiwavelength narrow linewidth erbium-doped fiber laser based on FP-LDs, Opt. Express 21 (2013) 16928–16933.
Contents lists available at ScienceDirect
Optics Communications journal homepage: www.elsevier.com/locate/optcom
Multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain Yiyang Luo, Li Xia n, Qizhen Sun, Wei Li, Yanli Ran, Deming Liu Wuhan National Laboratory for Optoelectronics, National Engineering Laboratory for Next Generation Internet Access System, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
art ic l e i nf o
a b s t r a c t
Article history: Received 28 September 2014 Accepted 30 October 2014 Available online 6 November 2014
In this paper, a multi-wavelength fiber laser based on self-seed light amplification and wavelengthdependent gain is proposed and demonstrated. A pumped erbium-doped fiber (EDF) in the linear cavity acts as the seed light source, which is also conducive to the gain equalization. A high power erbiumdoped fiber amplifier (EDFA) is deployed for self-seed amplification, and a highly nonlinear fiber (HNLF) is incorporated in the ring cavity to alleviate the mode competition induced by the homogeneous gain broadening of EDF. In the experiments, 25-wavelength operation within 0.5 dB uniformity is achieved with the extinction ratio of 42 dB using 500 m HNLF, and 38-wavelength operation within 3 dB uniformity is obtained with the extinction ratio of 35 dB using 1000 m HNLF. Our proposed laser has more lasing wavelengths with a better uniformity and stability. & Elsevier B.V. All rights reserved.
Keywords: Multi-wavelength fiber laser Erbium-doped fiber High nonlinear effect Wavelength-dependent gain
1. Introduction Multi-wavelength erbium-doped fiber laser (EDFL) has been extensively investigated for its versatile applications in dense wavelength-division-multiplexing (DWDM) communication system, fiber sensing, optical signal processing, and optical instrumentation. However, EDFL suffers from strong mode competition owing to the homogeneous gain broadening of the EDF at room temperature. In order to achieve stable multi-wavelength operation, various technologies have been applied to overcome the mode competition. To my best knowledge, these include the use of semiconductor optical amplification (SOA) [1–3], the introduction of fiber Raman or Brillouin amplification [4–6], cooling EDF in liquid-nitrogen temperature [7], inducing a frequency shifter [8– 10], and the utilization of nonlinear effect induced by the HNLF [11–13]. Yang et al. proposed a multi-wavelength ring fiber laser incorporated with a section of HNLF to alleviate the mode competition [14]. A stabilized multi-wavelength operation was obtained, but the envelope of the spectrum was not smooth, and the uniformity between adjacent wavelengths can be optimized further.
n
Corresponding author. E-mail address: [email protected] (L. Xia).
http://dx.doi.org/10.1016/j.optcom.2014.10.066 0030-4018/& Elsevier B.V. All rights reserved.
Zhang et al. presented a two Fabry–Perot laser diodes (FP-LDs) based multi-wavelength fiber laser [15]. Only 20-wavelength operation and non-uniformity of the spectrum impeded its applications. Moreover, the power fluctuation of 0.4 dB needed to be improved. In this letter, a multi-wavelength fiber laser with a pumped EDF and a section of HNLF is proposed and demonstrated. A linear cavity consisting of a pumped EDF and a broadband reflecting mirror is ingeniously incorporated with a conventional ring cavity. The operation principle is elucidated in detail on account of these two factors: self-seed light amplification and wavelength-dependent gain. Experimental verification is implemented to demonstrate this scheme and evaluate the performance of proposed multi-wavelength fiber laser.
2. Experimental setup and operation principle The schematic configuration of experimental setup is shown in Fig. 1. The optical gain are provided by a high power EDFA, and a 3.5 m-long EDF pumped by the 980 nm laser diode (LD), which is coupled into the EDF by a 980/1550 nm wavelength division multiplexing (WDM). In the ring cavity, a FFPF (Micron Optics International) with a free spectrum range (FSR) of 25 GHz is utilized as a narrow band comb filter, and an isolator is used for unidirectional operation. A section of HNLF induces the nonlinear effect of four wave mixing (FWM) to alleviate the mode
Y. Luo et al. / Optics Communications 338 (2015) 336–339
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Fig. 3. Multi-wavelength laser output spectrum with 500 m HNLF.
Fig. 1. Schematic configuration of the experimental setup.
Fig. 4. Multi-wavelength laser output spectrum with 1000 m HNLF.
Fig. 2. Transmission spectrum of the FFPF.
competition, and a polarization controller (PC) ensures appropriate polarization. A 3-ports optical circulator guides the light to propagate in right circular direction. A 3 dB optical coupler acts as an output port, which is also the connection between the ring cavity and the linear cavity. In the other end of the linear cavity, a Faraday rotator mirror (FRM) is utilized as a broadband reflecting mirror with 0.45 dB insertion loss. An optical spectrum analyzer (OSA, YOKOGAWA AQ6370, resolution of 0.02 nm) is engaged to observe the output optical spectrum. As shown in Fig. 2, the transmission spectrum of the FFPF utilized in our experiment is observed via a broadband light source and an OSA. The extinction ratio is about 20 dB with the wavelength spacing of 0.2 nm. The operation principle of the proposed fiber laser is shown as follows. The seed light generated by the 3.5 m-long pumped EDF is injected into the ring cavity consisting of a high power EDFA and HNLF, which is regarded as a traditional multi-wavelength oscillator. The seed light is amplified by this oscillating system.
Meanwhile, the mode competition is alleviated by the nonlinear effect of FWM in HNLF. This process is described as self-seed light amplification. Then, through adjusting the PC to appropriate polarization, the output light from the ring cavity can experience wavelength-dependent optical amplification introduced by the pumped EDF. It is defined as wavelength-dependent gain. Moreover, the amplifying capability of the pumped EDF is weaker than EDFA. Therefore, it primarily plays roles in gain equalization for each lasing wavelength also is an auxiliary for the boosted EDFA to slightly enhance the nonlinear effect.
3. Experimental results and discussion To start with, the experiment is conducted with a section of 500 m HNLF. As shown in Fig. 3, through adjusting the PC and the pump power of 980 nm LD, the output spectrum of 25 wavelengths within 0.5 dB uniformity is achieved from port A. The extinction ratio and line width of each wavelength are measured to be 42 dB and 0.016 nm, respectively. The wavelength spacing is 0.2 nm, which is in accordance with the transmission spectrum of the FFPF. It should be noted that the alleviation of the
338
Y. Luo et al. / Optics Communications 338 (2015) 336–339
Fig. 5. Multi-wavelength laser output spectrum with 1000 m HNLF corresponding to (a) unpumped EDF, and (b) pumped EDF.
mode competition and the broadening of the spectrum are induced by the HNLF, while the uniform power distribution of the wavelengths principally results from the pumped EDF and the adjustment of the PC, which provide the wavelength-dependent gain. Afterwards, a section of 1000 m HNLF is inserted in the ring cavity instead of the 500 m HNLF to reveal the influence of the nonlinear effect on operation performance of the multi-wavelength fiber laser. As shown in Fig. 4, the output spectrum with 38 wavelengths within 3 dB uniformity is achieved. The extinction ratio is a little more than 35 dB with the wavelength spacing of 0.2 nm. Compared with the output spectrum shown in Fig. 3, the spectrum is broadened in the experiment with 1000 m HNLF. The reason is related to the stronger nonlinear effect induced by the longer HNLF. More oscillating wavelengths can be generated due to the FWM between adjacent wavelengths. Lower extinction ratio of each wavelength may be the consequence of the high output power of the EDFA, which gives rise to the stronger nonlinear effect and a powerful amplified spontaneous emission (ASE) background noise, simultaneously. Thus it can be seen that it is a tradeoff between the broadening of the multi-wavelength spectrum and the extinction ratio in our experiment. For comparison, the output spectrum corresponding to the unpumped EDF is shown in Fig. 5(a), which is in contrast to the experiment with pumped EDF shown in Fig. 5(b). The experiment is conducted with 1000 m HNLF. In this case, the unpumped EDF just acts as a saturable absorber instead of the wavelength-dependent gain medium. Meanwhile, its auxiliary function of nonlinear effect enhancement loses. Consequently, non-uniform power distribution of the wavelengths is obtained. It is evident that the proposed scheme optimizes the uniformity of the lasing wavelengths. For practical applications, the stability of the multi-wavelength fiber laser is a crucial factor. On account of the well packaged FFPF and temperature control, the wavelength drift can be neglected to some extent. Accordingly, the output power fluctuation is investigated through the laser spectrum. As shown in Figs. 6(a) and (b), 5 lasing wavelengths are chosen to estimate the power fluctuations corresponding to the two cases of 500 m and 1000 m
Fig. 6. Power fluctuations of 5 lasing wavelengths with (a) 500 m HNLF, (b) 1000 m HNLF.
Y. Luo et al. / Optics Communications 338 (2015) 336–339
HNLFs, respectively. It is measured with the time interval of 5 min during an hour. The fiber laser with 500 m HNLF possesses a power fluctuation of less than 0.3 dB. Moreover, the case of 1000 m HNLF exhibits an outstanding stability with the power fluctuation of less than 0.08 dB. The longer HNLF contributes to the optimization of the stability, due to stronger nonlinear effect of FWM, which enhances the alleviation of the mode competition induced by the homogeneous gain broadening. At the same time, the mode hopping can be suppressed further. Consequently, a more stable multiwavelength operation is achieved with longer HNLF. Finally, it should be noted that the utilization of the pumped EDF is worthy in consideration of the operation performance optimization. Compared to the previous work mentioned in [14,15], the multi-wavelength fiber laser proposed in this letter possesses better uniformity of lasing wavelengths and more stable output optical power due to the mechanism of self-seed light amplification and wavelength-dependent gain.
4. Conclusions In conclusion, a stable multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain is presented. The pumped EDF not only acts as the seed light source, but also provides the wavelength-dependent gain to optimize the multi-wavelength uniformity. The HNLF is utilized to alleviate the mode competition induced by the homogeneous gain broadening of the EDF and the FFPF is inserted in the ring cavity as the wavelength selection component. In the experiment, multi-wavelength operations are achieved with the wavelength spacing of 0.2 nm using different lengths of HNLFs. The influences of the nonlinear effect on the spectral broadening and stability of the multi-wavelength operation are analyzed. In consideration of the good operation performance of the proposed multi-wavelength fiber laser, we believe that it would attract great attentions in potential applications.
Acknowledgments This work is supported by sub-Project of the Major Program of the National Natural Science Foundation of China (No. 61290315), the National Natural Science Foundation of China (No. 61275004), and the National High Technology Research and Development Program of China (863 Program) (No. 2012AA041203).
339
References [1] H. Chen, Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier, Opt. Lett. 30 (2005) 619–621. [2] K. Lee, S.D. Lim, C.H. Kim, J.H. Lee, Y.-G. Han, S.B. Lee, Noise reduction in multiwavelength SOA-based ring laser by coupled dual cavities for WDM applications, J. Lightwave Technol. 28 (2010) 739–745. [3] Z. Luo, W.-D. Zhong, Z. Cai, C. Ye, Y. Wen, High-performance SOA-based multiwavelength fiber lasers incorporating a novel double-pass waveguide-based MZI, Appl. Phys. B 96 (2009) 29–38. [4] S. Qin, D. Chen, Y. Tang, S. He, Stable and uniform multi-wavelength fiber laser based on hybrid Raman and erbium-doped fiber gains, Opt. Express 14 (2006) 10522–10527. [5] Y. Shee, M. Al-Mansoori, A. Ismail, S. Hitam, M. Mahdi, Multiwavelength Brillouin-erbium fiber laser with double-brillouin-frequency spacing, Opt. Express 19 (2011) 1699–1706. [6] A. Pinto, O. Frazão, J. Santos, M. Lopez-Amo, Multiwavelength fiber laser based on a photonic crystal fiber loop mirror with cooperative Rayleigh scattering, Appl. Phys. B 99 (2010) 391–395. [7] R. Hayashi, S. Yamashita, T. Saida, 16-wavelength 10-GHz actively mode-locked fiber laser with demultiplexed outputs anchored on the ITU-T grid,, Photon. Technol. Lett. IEEE 15 (2003) 1692–1694. [8] K. Zhou, D. Zhou, F. Dong, N.Q. Ngo, Room-temperature multiwavelength erbium-doped fiber ring laser employing sinusoidal phase-modulation feedback, Opt. Lett. 28 (2003) 893–895. [9] S.K. Kim, M.J. Chu, J.H. Lee, Wideband multiwavelength erbium-doped fiber ring laser with frequency shifted feedback, Opt. Commun. 190 (2001) 291–302. [10] J. Yao, J. Yao, Z. Deng, J. Liu, Multiwavelength erbium-doped fiber ring laser incorporating an SOA-based phase modulator,, Photon. Technol. Lett. IEEE 17 (2005) 756–758. [11] A. Zhang, H. Liu, M. Demokan, H. Tam, Stable and broad bandwidth multiwavelength fiber ring laser incorporating a highly nonlinear photonic crystal fiber,, Photon. Technol. Lett. IEEE 17 (2005) 2535–2537. [12] S. Yamashita, Y. Inoue, Multiwavelength Er-doped fiber ring laser incorporating highly nonlinear fiber, Jpn. J. Appl. Phys. 44 (2005) L1080. [13] H. Ahmad, R. Parvizi, K. Dimyati, M. Tamjis, S. Harun, FWM-based multi-wavelength erbium-doped fiber laser using Bi-EDF, Laser Phys. 20 (2010) 1414–1417. [14] C. Yang, L. Xia, Y. Wang, D. Liu, Stabilized 51-wavelength erbium-doped fiber ring laser based on high nonlinear fiber, Opt. Commun. (2014). [15] A. Zhang, Y. Jin, X. Feng, J. Zhou, Z. Li, B.-O. Guan, Multiwavelength narrow linewidth erbium-doped fiber laser based on FP-LDs, Opt. Express 21 (2013) 16928–16933.