ISSN 1054660X, Laser Physics, 2012, Vol. 22, No. 11, pp. 1717–1720. © Pleiades Publishing, Ltd., 2012.
Original Text © Astro, Ltd., 2012.
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1 1. INTRODUCTION
Erbiumdoped fiber (EDF) ring lasers with single and multiwavelength output simultaneously have considerable interest in the wavelength division multi plexing (WDM) communications and optics sensor applications [1–3]. And so, the long cavity fiber ring laser with ultra high energy pulsed and low repetition rates can be widely applied in micromachining, mate rial processing, remote sensing and light detecting sys tem [4–7]. Furthermore, to achieve the singlelongi tudinalmode (SLM) and stable output performances in fiberbased ring lasers, the cavity loss design, dou blepass scheme, and modelocked pulse design have been also investigated and discussed [8–12].
Here, in order to achieve the fiber ring laser with longer cavity, the Raman amplifier (RA)based, hybrid RA and erbiumdoped fiber amplifier (EDFA) based or hybrid EDFA and semiconductor optical amplifier (SOA)based fiber lasers have been proposed and investigated [13–15]. However, these proposed amplifierbased fiber lasers have the higher cost and energy consumption in longcavity laser area.
In this paper, we propose and demonstrate experi mentally a Sagnac loop based SOA fiber ring laser con figuration, which has a long cavity length for wave length lasing; together with energyefficient. Here, ten fiber Bragg gratings (FBGs) are employed serving as reflected element in remote site for wavelength lasing and remote sensing simultaneously, in the operating range of 1530 to 1560 nm. In the experiment, the dif ferent cavity lengths of a few ten m to 25 km long are also used in the proposed laser scheme for lasing and tuning due to the Sagnac loop structure. Therefore, 1The article is published in the original.
this proposed fiber laser scheme not only can use a 25 km long fiber cavity, but also has the energyeffi cient via the Saganc design.
2. EXPERIMENT AND RESULTS
Figure 1 presents the experimental setup of pro posed Sagnac loop fiber laser configuration with the cavity lengths of a few ten to 25 km for wavelength las ing and sensor detecting simultaneously. This pro posed laser constructed by an semiconductor optical amplifier (SOA), a 2 × 2 and 50 : 50 optical coupler (CP), a tunable bandpass filter (TBF), a length of sin glemode fiber (SMF), a polarization controller (PC) and ten fiber Bragg gratings (FBGs). As seen in Fig. 1, the 2 × 2 CP could be produced a Sagnac loop laser scheme, and the SOA, TBF, and PC were used inside Sagnac loop. The cavity length of Sagnac loop (L1) is nearly 8 m long and the external cavity length (L2) of singlemode fiber (SMF) is among 0 to 25 km long, as illustrated in Fig. 1. Here, the Cband SOA is only operated at 150 mA pumping current. In the measure ment, the output wavelength and power are measured by the optical spectrum analyzer (OSA) with a 0.05 nm resolution and power meter (PM), respec tively.
In this experiment, the reflected Bragg wavelengths and peak reflectivities of ten FBGs used are 1531.80, 1535.93, 1537.33, 1538.33, 1542.35, 1543.40, 1544.38, 1547.98, 1554.48, and 1559.55 nm, and 81.7, 86.8, 87.3, 87.3, 88.1, 88.5, 87.4, 86.73, 88.4, and 87.8%, respectively. The ten FBGs are cascaded in remote site to connect to Sagnac loop as seen in Fig. 1. And the interval of each FBG is nearly 2 m long. Fur thermore, the tuning range and 3 dB bandwidth of
Semiconductor Optical AmplifierBased Laser with 25 km Long
Cavity Length Utilizing Sagnac Fiber Ring Structure
1C. H. Yeha, * and C. W. Chowb
a Information and Communications Research Laboratories, Industrial Technology Research Institute (ITRI),
Hsinchu 31040, Taiwan
b Department of Photonics and Institute of ElectroOptical Engineering, National Chiao Tung University,
Hsinchu 30010, Taiwan
*email: [email protected]; [email protected]
Received December 18, 2011; in final form, December 27, 2011; published online October 1, 2012
Abstract—In the investigation, we propose and demonstrate a Sagnac ring based fiber laser structure using a
semiconductor optical amplifier (SOA) to act as a gain medium with short to long fiber cavity lengths for wavelength lasing and tuning. Here, ten fiber Bragg gratings (FBGs) with different reflected Bragg wave lengths are used serving as the reflected element in the proposed laser configuration for wavelength lasing and remote sensing simultaneously. Furthermore, the different cavity fiber lengths of a few ten m to 25 km, which are used in the proposed laser scheme, has been analyzed and discussed.
DOI: 10.1134/S1054660X12110175
FIBER OPTICS AND FIBER LASERS
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YEH, CHOW
TBF are 30 nm (1530–1560 nm) and 0.4 nm respec tively. And the TBF is tuned to align and match the corresponding reflected Bragg wavelength of each FBG used for wavelength lasing. Here, the PC is used
to adjust the polarization status and maintain the max imum output power for this Sagnac loop laser.
In the measurement, first we set the SMF length L2 is 25 km long in the proposed fiber laser configuration. Figure 2 shows the output spectra of ten lasing wave lengths via the FBGs in the proposed Sagnac loop fiber laser structure. And, we can observe the higher amplified spontaneous emission (ASE) spectrum of the proposed laser is around in the shorter wavelength range. Besides, the ASE noise can be suppressed are better, when the lasing wavelength is tuned in the higher wavelength gradually, as also shown in Fig. 2. The different peak power can be observed in Fig. 2 due to the various reflected Bragg wavelength of each FBG and gain distribution of SOA.
Hence, Fig. 3 presents the output powers and sig nalto noise ratios (SNRs) of the ten lasing wave lengths in the proposed laser scheme. The measured powers and SNRs of ten lasing wavelengths are –12.9, –10.7, –12.7, –12.7, –11.0, –8.8, –12.3, –8.3, ⎯10.0, and –9.8 dBm and 29.10, 29.90, 27.42, 27.20, 28.50, 31.50, 28.40, 27.10, 30.62, and 32.72 dB, FBG10 FBG2 FBG3 FBG1 5, 10,..., 25 km L2 SMF Output CP: 2 × 2 Optical coupler PC: Polarization controller FBG: Fiber bragg grating SMF: Singlemode fiber
SOA: Semiconductor optical amplifier TBF: Tunable bandpass filter
CP L1 = 8 m SOA
TBF P
C
Fig. 1. Experimental setup of proposed Sagnac loop fiber laser configuration with the cavity lengths of a few ten to 25 km for wave
length lasing and sensor detecting simultaneously.
1565 0 −50 −10 −20 −30 −40 Power, dBm @25 km SMF 1560 1555 1550 1545 1540 1535 1530 1525 Wavelength, nm
Fig. 2. Output spectra of ten lasing wavelengths via the FBGs in the proposed Sagnac loop fiber laser structure.
1565 1560 1555 1550 1545 1540 1535 1530 1525 −7 −9 −11 −13 −15 Power, dBm 40 35 30 25 20 Signaltonoise ratio, dB Wavelength, nm Power SNR
Fig. 3. Output powers and signalto noise ratios (SNRs) of
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SEMICONDUCTOR OPTICAL AMPLIFIERBASED LASER 1719
respectively, at the wavelengths of 1531.80, 1535.91, 1537.31, 1538.30, 1542.32, 1543.38, 1544.35, 1547.95, 1554.46, and 1559.52 nm. Moreover, the maximum output power difference and SNR variation of 4.6 and 5.6 dB are observed in this measurement.
Then, we set the SMF length L2 to 10 km long in the proposed laser scheme as seen in Fig. 1. So, Fig. 4 shows the output spectra of ten lasing wavelengths via the corresponding reflected wavelength of FBGs in the proposed fiber laser structure. The ASE background noise of the proposed laser, which can be more sup pressed, is better when the lasing wavelength is tuned at the higher wavelength, as also shown in Fig. 4. Moreover, the different output power is also observed in Fig. 4 because of the various reflected Bragg wave length of each FBG and gain distribution. Hence, the measured powers and SNRs of ten lasing wavelengths are –10.2, –8.7, –9.2, –11.8, –6.9, –6.1, –4.7, –5.9, –4.9, and –3.2 dBm and 32.32, 35.71, 34.21, 31.74,
38.64, 39.53, 40.92, 40.54, 42.6, and 45.43, respec tively, at the wavelengths of 1531.80, 1535.91, 1537.31, 1538.30, 1542.32, 1543.38, 1544.35, 1547.95, 1554.46, and 1559.52 nm. Moreover, the maximum output power difference and SNR variation of 8.6 and 13.1 dB are observed in this measurement. As a result, the measured output powers and SNRs of Fig. 4 are larger and better than that of Fig. 2, due to the smaller cavity loss in the proposed fiber laser scheme.
Next, Fig. 5 shows the measured output powers and SNRs versus the different cavity fiber lengths L2 of 0, 5, 10, 15, 20, and 25 km long using in the proposed laser structure, respectively, at the lasing wavelength of 1559.52 nm. While the L2 is 0 and 25 km long, the obtained output powers and SNRs are –1.1 dBm and 51.2 dB, and –9.8 dBm and 32.72 dB, respectively. As illustrated in Fig. 5, with the fiber length L2 is increase gradually, the obtained output power and SNR are also increase. However, when the lengths of L2 are 10, 15, and 20 km long, respectively, the observed SNRs are almost the same.
As we know, the FBG can be used to act as a sensor for the temperature and strain sensing due to its high sensitivity [16–19]. In our proposed laser scheme, each FBG would be also employed to serve as remote sensor in the remote site. To verify and ensure the FBG sensor in the proposed laser, a strain is applied on the FBG10, which reflected wavelength is 1559.52 initially. When we apply the strain of 2000 με in FBG10, the corresponding wavelength shift is measured around 2.8 nm, as shown in Fig. 6. As a result, the ten FBGs also can be employed to sense the temperature and strain changes in remote site for the proposed fiber laser. 1565 0 −50 −10 −20 −30 −40 Power, dBm @10 km SMF 1560 1555 1550 1545 1540 1535 1530 1525 Wavelength, nm
Fig. 4. Output spectra of ten lasing wavelengths via the corresponding reflected wavelength of FBGs in the proposed fiber laser
structure. 30 0 −12 Power, dBm 55 35 45 30
Signal noise ratio, dB
Fiber length, km Power SNR −2 −4 −6 −8 −10 25 20 15 10 5 0 50 40
Fig. 5. Measured output powers and SNRs versus the dif
ferent cavity fiber lengths L2 of 0, 5, 10, 15, 20, and 25 km long using in the proposed laser structure, respectively, at the lasing wavelength of 1559.52 nm.
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3. CONCLUSIONS
In summary, we have proposed and demonstrated a Saganc ring based fiber laser structure using a SOA to act as a gain medium with short to long fiber cavity lengths for wavelength lasing and tuning. Here, ten FBGs with different reflected Bragg wavelengths are used serving as the reflected element in the proposed laser configuration for wavelength lasing and remote sensing simultaneously. Besides, the different cavity fiber lengths of a few ten m to 25 km, which are used in the proposed laser scheme, has been analyzed and discussed. Here, we don’t require the nonlinear effect and high power consumption to achieve the long cav ity length of fiber ring laser scheme. We just use the simple Sagnac architecture design to accomplish the 25 km cavity length. Therefore, this proposed fiber laser scheme not only can use a 25 km long fiber cavity, but also has the energyefficient via the Sagnac design.
ACKNOWLEDGMENTS
Author would like to thank Mr. S. S. Lu and Y. F. Wu for the help with experiment.
REFERENCES
1. C. H. Yeh and C. W. Chow, Laser Phys. Lett. 7, 158 (2010).
2. M. R. A. Moghaddam, S. W. Harun, S. Shahi, K. S. Lim, and H. Ahmad, Laser Phys. 20, 516 (2010).
3. C.H. Yeh and S. Chi, Opt. Express 13, 5494 (2005). 4. B. N. Nyushkov, V. I. Denisov, S. M. Kobtsev, V. S. Piv
tsov, N. A. Kolyada, A. V. Ivanenko, and S. K. Turitsyn, Laser Phys. Lett. 7, 661 (2010).
5. C.H. Yeh, C.C. Lee, C.Y. Chen, and S. Chi, IEEE Photon. Technol. Lett. 16, 765 (2004).
6. M. Zhang, L. L. Chen, C. Zhou, Y. Cai, L. Ren, and Z. G. Zhang, Laser Phys. Lett. 6, 657 (2009).
7. R. Sonee Shargh, M. H. AlMansoori, S. B. A. Anas, R. K. Z. Sahbudin, and M. A. Mahdi, Laser Phys. Lett.
8, 139 (2011).
8. C. H. Yeh, C. W. Chow, Y. F. Wu, Y. H. Lin, B. C. Cheng, and J. H. Chen, Laser Phys. Lett. 8, 672 (2011). 9. L. R. Wang, X. M. Liu, Y. K. Gong, D. Mao, and
H. Feng, Laser Phys. Lett. 8, 376 (2011).
10. D. Luo, S. Y. Yan, X. P. Xie, and W. Zhao, Laser Phys.
21, 1909 (2011).
11. G. Sun, Y. Zhou, L. Cui, and Y. Chung, Laser Phys. 21, 1899 (2011).
12. H. Ahmad, M. Z. Zulkifli, N. A. Hassan, A. A. Latif, and S. W. Harun, Laser Phys. 21, 1208 (2011).
13. P.C. Peng, H.Y. Tseng, and S. Chi, IEEE Photon. Technol. Lett. 16, 575 (2004).
14. A. Ahmad, M. A. Mahdi, M. I. Md Ali, and A. K. Zam zuri, Laser Phys. Lett. 5, 202 (2008).
15. P.C. Peng, K.M. Feng, W.R. Peng, H.Y. Chiou, C.C. Chang, and S. Chi, Opt. Commun. 252, 127 (2005).
16. H. ArellanoSotelo, Yu. O. Barmenkov, and A. V. Kir’ya nov, Laser Phys. Lett. 5, 825 (2008).
17. C.H. Yeh, C.W. Chow, P.C. Wu, and F.C. Tseng, Sensors 11, 1375 (2011).
18. P. Hajireza, S. D. Emami, C. L. Cham, D. Kumar, S. W. Harun, and H. A. AbdulRashid, Laser Phys. Lett. 7, 739 (2010).
19. C. H. Yeh, C. W. Chow, C. H. Wang, F. Y. Shih, Y. F. Wu, and S. Chi, Measure. Sci. Technol. 20, 043001 (2009). 1566 1564 1562 1560 1558 1556 Wavelength, nm 0 −50 −10 −20 −30 −40 Power, dBm @1559.52 nm 2.8 nm @ 2000 με
Fig. 6. Output spectrum of the proposed laser scheme,
