Open Access
Add to BibSonomyAbstract
We propose a novel multi-wavelength fiber optical parametric oscillator (MW-FOPO) based on a ring cavity. A highly nonlinear fiber and a Mach-Zehnder interferometer formed by two 3-dB optical couplers are used as the gain medium and the comb filter, respectively. Multi-wavelength lasing of the MW-FOPO with an ultra-narrow wavelength spacing of about 0.08 nm is achieved. The output spectrum of the MW-FOPO covers a wavelength regime from 1510 nm to 1615 nm (for lasing wavelengths with the power that exceeds −60 dBm). The stability of the MW-FOPO is discussed and experimentally demonstrated. A comparison of the output spectra between the MW-FOPO and the multi-wavelength Erbium-doped fiber laser is also presented.
©2010 Optical Society of America
1. Introduction
In the past several years, a great variety of multi-wavelength fiber lasers (MWFLs) based on various optical amplifiers including Erbium-doped fiber amplifiers (EDFAs) [1–5], fiber Raman amplifiers (FRAs) [6–8] and semiconductor optical amplifiers (SOAs) [9,10] have been proposed and demonstrated, which have attracted considerable attention because of their huge potential in applications such as WDM systems [11,12], optical fiber sensors [13,14], microwave photonics [15–17] and spectroscopy [18,19]. Thereinto, multi-wavelength Erbium-doped fiber lasers (MW-EDFLs) have been widely investigated due to their advantages such as low cost, low threshold, high power conversion efficiency and compatibility with the fiber optical communication. However, MW-EDFLs are not stable at room temperature due to the strong homogenous line broadening and cross-saturation gain of an Erbium-doped fiber (EDF) [20]. Multi-wavelength Raman fiber laser has not been considered as a promising MWFL due to the limited Raman gain bandwidth. MWFLs based on SOAs usually suffer from the low power level. Besides the above-mentioned optical amplifiers, fiber optical parametric amplifiers (FOPAs) [21–27] with excellent performances such as high gain, large gain bandwidth, arbitrary center wavelength, low noise figure and compatibility with high power have been well developed, which results in a fast rise of the research on fiber optical parametric oscillators [28–34] recently. Multi-wavelength fiber optical parametric oscillator (MW-FOPO) should be one of the most promising MWFLs in the near future due to the advantages of FOPAs.
More recently, an MW-FOPO based on a dual-pump FOPA and a superimposed chirped fiber Bragg grating [35] and an MW-FOPO based on a transmission grating filter (TGF, formed by superimposing two linearly chirped fiber Bragg gratings) and a programmable filter (Peleton, QTM) [36] have been demonstrated, which, however, suffer from the complex structure with high cost. In this paper, a simple-structure MW-FOPO based on a segment of highly nonlinear fiber (HNLF) and a Mach-Zehnder interferometer (MZI) formed by two 3-dB optical couplers is proposed and demonstrated. Multi-wavelength lasing with an ultra-narrow wavelength spacing of about 0.08 nm in a wide wavelength regime from 1510 nm to 1615 nm (for lasing wavelengths with the power that exceeds −60 dBm) is achieved, which is very stable against environmental conditions.
2. Experimental setup and results
The experimental setup of the proposed MW-FOPO is shown in Fig. 1 . A tunable laser (TL, Agilent 81940A, with a tunable wavelength regime from 1520 nm to 1630 nm) provides a pump seed light. We use a phase modulation method to broaden the linewidth of the pump seed light by employing a phase modulator (PM) driven by a RF signal of a 3.5-Gb/s-(231-1) pseudorandom bit sequence (PRBS), which can successfully suppress the stimulated Brillouin scattering (SBS) when the high power pump light is injected into the HNLF. A high power Erbium-doped fiber amplifier (HPEDFA) with a maximal output power of 2 W is used to achieve a high-power pump source. An optical isolator (ISO1) is used after the HPEDFA. By way of a broadband wavelength division multiplexer (BWDM), the pump light is injected into the HNLF, which is used as the gain medium of the proposed MW-FOPO. The length, the loss, the zero-dispersion wavelength, the dispersion slope at the zero-dispersion wavelength and the nonlinear coefficient (at 1550 nm) of the HNLF are about 520 m, 0.92 dB/m, 1553.35 nm, 0.016 ps/(nm2km) and 15 W−1km−1, respectively. An MZI which consists of two 3-dB (50:50) optical couplers is used as a comb filter in the ring cavity of the MW-FOPO. The wavelength spacing of the comb filter (which is about 0.08 nm in our experiment) depends on the phase difference (i.e., fiber length difference) between the two arms of the MZI. An optical isolator (ISO2) ensures a clockwise ring cavity and two polarization controllers (PC1 and PC2) are used for the adjustment of the state of polarization (SOP). An arm (with 10% power ratio) of the optical coupler (OC) is used as the output port of the MW-FOPO.
Fig. 1 Schematic configuration of the proposed MW-FOPO. TL: tunable laser; PC: polarization controller; PM: phase modulator; HPEDFA: high power Erbium-doped fiber amplifier; ISO: isolator; BWDM: broadband wavelength division multiplexer; HNLF: highly nonlinear fiber; OC: optical coupler; MZI: Mach-Zehnder interferometer.
In our experiment, the wavelength and the output power of the TL are set to 1555.8 nm and 6 dBm, respectively. The pump power after the optical isolater (ISO1) is about 1.53 W when the HPEDFA reaches its maximal power. By carefully adjusting the two polarization controllers, stable multi-wavelength lasing of the MW-FOPO is achieved. Figure 2 shows output spectrum (black solid curve) of the proposed MW-FOPO, which covers a wide wavelength regime from 1510 nm to 1615 nm (for lasing wavelengths with the power that exceeds −60 dBm). Inset shows a local enlargement of the spectrum around 1558 nm and one can find the wavelength spacing of the MW-FOPO is about 0.08 nm, which is the same as the recently reported MWFL based on an SOA and a fiber Sagnac loop filter [10]. Note that we use an optical spectrum analyzer (OSA) (Ando AQ6317) with a resolution of 0.01 nm in our experiment. The broadband lasing wavelength regime of the proposed MW-FOPO is mainly due to the large gain bandwidth of the FOPA based on the HNLF, which can be further enlarged by employing a pump laser with higher power. The red dotted curve in Fig. 2 shows the amplified spontaneous emission (ASE) spectrum when the pump light is injected into the HNLF, where one can find the envelope profile of the output spectrum of the MW-FOPO is similar to the ASE spectrum profile of an FOPA based on the HNLF.
Fig. 2 Spectra of the proposed MW-FOPO (black solid curve) and the ASE of the FOPA (red dotted curve). Inset shows a local enlargement of the spectrum around 1558 nm.
Stability is one of the most important properties of the MWFLs. Unlike the EDFA which suffers from the strong homogenous line broadening and the cross-saturation gain for signals with different wavelengths, the FOPA exhibits the inhomogenous line broadening at room temperature and the cross-saturation gain appears only when the signal power is comparable with the pump power. In addition, the four-wave-mixing (FWM) effect in the cavity of the MW-FOPO ensures the self-stability of multi-wavelength lasing, which has been well demonstrated in some MW-EDFLs [3–5]. Besides the property of the gain medium, the comb filter plays an important role in the stability (particularly the wavelength stability) of the MWFL. We use UV-curing epoxy acrylate adhesive to attach the MZI to a metal substrate (which is under the temperature control) to ensure MZI’s stability against environmental conditions in our experiment. The stability of the proposed MW-FOPO is experimentally demonstrated. We use the OSA to repeatly scan the optical spectrum of the MW-FOPO per 3 minutes within 30 minutes for the 12 lasing wavelengths (the ones shown in the inset of Fig. 2). Figure 3 shows the peak power fluctuation of the 12 lasing wavelengths of the MW-FOPO within 30 minutes and the maximal peak power fluctuation is less than 0.18 dB, which shows that the proposed MW-FOPO is quite stable at room temperature.
Fig. 3 Peak power fluctuation within 30 minutes for the 12 lasing wavelengths of the proposed MW-FOPO.
The FWM effect in the cavity of the MW-FOPO will also contribute to the power uniformity of each lasing wavelength. Figure 4(a) shows the output spectra of the proposed MW-FOPO when the pump powers are 0.478 W, 0.495 W, 0.620 W, 1.02 W, 1.20W and 1.53 W, respectively. The envelope profile of the output spectrum of the MW-FOPO becomes flattened when the pump power increases. For a comparison of the MW-FOPO and the MW-EDFL, we introduce an EDFA in the ring cavity of the MW-FOPO (between the MZI and the ISO2) and remove the pump source of the MW-FOPO. Thus, an MW-EDFL is built and the output spectrum of the MW-EDFL is shown in Fig. 4(b) (blue dotted curve), where we can find the limited lasing wavelength regime from 1558 nm to 1568 nm. Compared with the MW-EDFL, the advantage of the MW-FOPO with a broadband lasing wavelength regime is apparently presented.
Fig. 4 (a) Output spectra of the proposed MWFOPO when the pump powers are 0.478 W, 0.495 W, 0.620 W, 1.02 W, 1.20W and 1.53 W, respectively. (b) Spectra of the proposed MW-FOPO (black solid curve) and the MW-EDFL (blue dotted curve).
3. Discussion and conclusion
Two of the most important components of the MWFL are the gain medium and the comb filter. On the one hand, thanks to the recent development of the HPEDFAs and the HNLFs (which also include the highly nonlinear photonic crystal fibers), FOPAs have exhibited excellent performances such as high gain, large gain bandwidth, arbitrary center wavelength, low noise figure and compatibility with high power, which are very appreciated for applications in MWFLs. As we have mentioned above, lasing wavelengths of the proposed MW-FOPO covers a large wavelength regime which is much larger then the MW-EDFL. In our experiments, the spectra of the proposed MW-FOPO and the MW-EDFL have been shown in Fig. 4(b) as a comparison. On the other hand, a comb filter with fiber compatibility is expected in MWFLs. The previous work has shown that an MZI [37,38] or a fiber Sagnac loop filter [39,40] is suitable for applications in FWFLs. Thus, the MW-FOPO with a comb filter such as an MZI or a fiber Sagnac loop filter could be one of the most promising MWFLs.
In conclusion, we have demonstrated a ring-cavity MW-FOPO based on an HNLF and an MZI. Multi-wavelength lasing of the MW-FOPO with an ultra-narrow wavelength spacing of about 0.08 nm has been achieved. The output spectrum of the MW-FOPO covers a wavelength regime from 1510 nm to 1615 nm, which is much larger than that of an MW-EDFL. Good stability of the MW-FOPO has been partially demonstrated by measuring the peak power fluctuations of the 12 lasing wavelengths.
Acknowledgments
Authors should thank Dr. Kenneth K. Y. Wong for his helpful discussions. This work is supported partially by Program for Science and Technology Innovative Research Team in Zhejiang Normal University, Natural Science Foundation of China under projects (NO. 60907020 and NO. 60977066).
References and links
1. A. A. M. Staring, L. H. Spiekman, J. J. M. Binsma, E. J. Jansen, T. van Dongen, P. J. A. Thijs, M. K. Smit, and B. H. Verbeek, “A compact nine-channel multiwavelength laser,” IEEE Photon. Technol. Lett. 8(9), 1139–1141 (1996). [CrossRef]
2. D. S. Moon, U.-C. Paek, and Y. Chung, “Multi-wavelength lasing oscillations in an erbium-doped fiber laser using few-mode fiber Bragg grating,” Opt. Express 12(25), 6147–6152 (2004). [CrossRef] [PubMed]
3. 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(1), 142–147 (2005). [CrossRef] [PubMed]
4. Y Y.-G. Han, T. Van Anh Tran, and S. B. Lee, “Wavelength-spacing tunable multiwavelength erbium-doped fiber laser based on four-wave mixing of dispersion-shifted fiber,” Opt. Lett. 31(6), 697–699 (2006). [CrossRef] [PubMed]
5. D. Chen, “Stable multi-wavelength erbium-doped fiber laser based on a photonic crystal fiber Sagnac loop filter,” Laser Phys. Lett. 4(6), 437–439 (2007). [CrossRef]
6. C. J. S. de Matos, D. A. Chestnut, P. C. Reeves-Hall, F. Koch, and J. R. Taylor, “Multi-wavelength, continuous wave fibre Raman ring laser operating at 1.55 μm,” Electron. Lett. 37(13), 825–826 (2001). [CrossRef]
7. Y.-G. Han, C.-S. Kim, J. U. Kand, U.-C. Paek, and Y. Chung, “Multiwavelength raman fiber-ring laser based on tunable cascaded long-period fiber gratings,” IEEE Photon. Technol. Lett. 15(3), 383–385 (2003). [CrossRef]
8. X. Y. Dong, P. Shum, N. Q. Ngo, and C. C. Chan, “Multiwavelength Raman fiber laser with a continuously-tunable spacing,” Opt. Express 14(8), 3288–3293 (2006). [CrossRef] [PubMed]
9. K. K. Qureshi, H. Y. Tam, W. H. Chung, and P. K. A. Wai, “Multiwavelength laser source using linear optical amplifier,” IEEE Photon. Technol. Lett. 17(8), 1611–1613 (2005). [CrossRef]
10. Z. Zhang, J. Wu, K. Xu, X. Hong, and J. Lin, “Tunable multiwavelength SOA fiber laser with ultra-narrow wavelength spacing based on nonlinear polarization rotation,” Opt. Express 17(19), 17200–17205 (2009). [CrossRef] [PubMed]
11. S. H. Oh, J. U. Shin, Y. J. Park, S. B. Kim, S. Park, H. K. Sung, Y. S. Baek, and K. R. Oh, “Multiwavelength lasers for WDM-PON optical line terminal source by silica planar lightwave circuit hybrid integration,” IEEE Photon. Technol. Lett. 19(20), 1622–1624 (2007). [CrossRef]
12. K. Lee, S. B. Lee, J. H. Lee, C. H. Kim, and Y. Han, “Side-mode suppressed multiwavelength fiber laser and broadcast transmission,” in Optical Fiber Communication Conference and Exposition and The National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2008), paper OThF1.
13. L. Talaverano, S. Abad, S. Jarabo, and M. López-Amo, “Multiwavelength fiber laser sources with Bragg-grating sensor multiplexing capability,” J. Lightwave Technol. 19(4), 553–558 (2001). [CrossRef]
14. Y. G. Han, T. V. A. Tran, S. H. Kim, and S. B. Lee, “Multiwavelength Raman-fiber-laser-based long-distance remote sensor for simultaneous measurement of strain and temperature,” Opt. Lett. 30(11), 1282–1284 (2005). [CrossRef] [PubMed]
15. H. Ou, H. Fu, D. Chen, and S. He, “A tunable and reconfigurable microwave photonic filter based on a Raman fiber laser,” Opt. Commun. 278(1), 48–51 (2007). [CrossRef]
16. X. Feng, C. Lu, H. Y. Tam, and P. K. A. Wai, “Reconfigurable microwave photonic filter using multiwavelength erbium-doped fiber laser,” IEEE Photon. Technol. Lett. 19(17), 1334–1336 (2007). [CrossRef]
17. G. F. Shen, X. M. Zhang, H. Chi, and X. F. Jin, “Microwave/millimeter-wave generation using multi-wavelength photonic crystal fiber Brillouin laser,” Prog. Electromagn. Res. 80, 307–320 (2008). [CrossRef]
18. Y. He and B. J. Orr, “Rapidly swept, continuous-wave cavity ringdown spectroscopy with optical heterodyne detection: single- and multi-wavelength sensing of gases,” Appl. Phys. B 75(2-3), 267–280 (2002). [CrossRef]
19. J. Marshall, G. Stewart, and G. Whitenett, “Design of a tunable L-band multi-wavelength laser system for application to gas spectroscopy,” Meas. Sci. Technol. 17(5), 1023–1031 (2006). [CrossRef]
20. S. L. Pan, C. Y. Lou, and Y. Z. 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(3), 1113–1118 (2006). [CrossRef] [PubMed]
21. M. E. Marhid, K. K.-Y. Wong, G. Kalogerakis and L. G. Kazovsky, “Toward practical fiber optical parametric amplifiers and oscillators,” Optics & Photonics News, 21–25 (2004).
22. M. Ho, K. Uesaka, Y. Akasaka, and L. G. Kazovsky, “200-nm-bandwidth fiber optical amplifier combing parametric and Raman gain,” J. Lightwave Technol. 19(7), 977–981 (2001). [CrossRef]
23. K. K.-Y. Wong, K. Shimizu, K. Uesaka, G. Kalogerakis, M. E. Marhic, and L. G. Kazovsky, “Continuous-wave fiber optical parametric amplifier with 60-dB gain using a novel two segment design,” IEEE Photon. Technol. Lett. 15(12), 1707–1709 (2003). [CrossRef]
24. M. Gao, C. Jiang, W. Hu, and J. Wang, “Optimized design of two-pump fiber optical parametric amplifier with two-section nonlinear fibers using genetic algorithm,” Opt. Express 12(23), 5603–5613 (2004). [CrossRef] [PubMed]
25. D. Dahan and G. Eisenstein, “Tunable all optical delay via slow and fast light propagation in a Raman assisted fiber optical parametric amplifier: a route to all optical buffering,” Opt. Express 13(16), 6234–6249 (2005). [CrossRef] [PubMed]
26. T. Torounidis, P. A. Andrekson, and B. Olsson, “Fiber-optical parametric amplifier with 70-dB gain,” IEEE Photon. Technol. Lett. 18(10), 1194–1196 (2006). [CrossRef]
27. K. K. Y. Wong, G. W. Lu, and L. K. Chen, “Polarization-interleaved WDM signals in a fiber optical parametric amplifier with orthogonal pumps,” Opt. Express 15(1), 56–61 (2007). [CrossRef] [PubMed]
28. J. Lasri, P. Devgan, J. E. Renyong Tang, Sharping, and P. Kumar, “A microstructure-fiber-based 10-GHz synchronized tunable optical parametric oscillator in the 1550-nm regime,” IEEE Photon. Technol. Lett. 15(8), 1058–1060 (2003). [CrossRef]
29. C. J. S. de Matos, J. R. Taylor, and K. P. Hansen, “Continuous-wave, totally fiber integrated optical parametric oscillator using holey fiber,” Opt. Lett. 29(9), 983–985 (2004). [CrossRef] [PubMed]
30. G. K. L. Wong, S. G. Murdoch, R. Leonhardt, J. D. Harvey, and V. Marie, “High-conversion-efficiency widely-tunable all-fiber optical parametric oscillator,” Opt. Express 15(6), 2947–2952 (2007). [CrossRef] [PubMed]
31. J. E. Sharping, J. R. Sanborn, M. A. Foster, D. Broaddus, and A. L. Gaeta, “Generation of sub-100-fs pulses from a microstructure-fiber-based optical parametric oscillator,” Opt. Express 16(22), 18050–18056 (2008). [CrossRef] [PubMed]
32. Y. Q. Xu, S. G. Murdoch, R. Leonhardt, and J. D. Harvey, “Widely tunable photonic crystal fiber Fabry-Perot optical parametric oscillator,” Opt. Lett. 33(12), 1351–1353 (2008). [CrossRef] [PubMed]
33. W. Z. Zhuang, W. C. Huang, Y. P. Huang, K. W. Su, and Y. F. Chen, “Passively Q-switched photonic crystal fiber laser and intracavity optical parametric oscillator,” Opt. Express 18(9), 8969–8975 (2010). [CrossRef] [PubMed]
34. J. E. Sharping, C. Pailo, C. Gu, L. Kiani, and J. R. Sanborn, “Microstructure fiber optical parametric oscillator with femtosecond output in the 1200 to 1350 nm wavelength range,” Opt. Express 18(4), 3911–3916 (2010). [CrossRef] [PubMed]
35. Z. Luo, W. D. Zhong, Z. Cai, C. Ye, H. Xu, X. Dong, and L. Xia, “Multiwavelength fiber optical parametric oscillator,” IEEE Photon. Technol. Lett. 21(21), 1609–1611 (2009). [CrossRef]
36. J. Li and L. R. Chen, “Tunable and reconfigurable multiwavelength fiber optical parametric oscillator with 25 GHz spacing,” Opt. Lett. 35(11), 1872–1874 (2010). [CrossRef] [PubMed]
37. H. L. An, X. Z. Lin, E. Y. B. Pun, and H. D. Liu, “Multi-wavelength operation of an Erbium-doped fiber ring laser using a dual-pass Mach-Zehnder comb filter,” Opt. Commun. 169(1-6), 159–165 (1999). [CrossRef]
38. D. Chen, S. Qin, and S. He, “Channel-spacing-tunable multi-wavelength fiber ring laser with hybrid Raman and Erbium-doped fiber gains,” Opt. Express 15(3), 930–935 (2007). [CrossRef] [PubMed]
39. X. P. Dong, S. Li, K. S. Chiang, M. N. Ng, and B. C. B. Chu, “Multiwavelength Erbium-doped fibre laser based on a high-birefringence fibre loop mirror,” Electron. Lett. 36(19), 1609–1610 (2000). [CrossRef]
40. Y. Gao, D. Chen, and S. Gao, “Stable multi-wavelength erbium-doped fiber laser based on dispersion-shifted fiber and Sagnac loop filter,” Chin. Opt. Lett. 5, 519–521 (2007).
