Frontiers in Guided Wave Optics and Optoelectronics Part 2 docx

Application Specific Optical Fibers 25 Fig. 21. a) Optical micrograph of the cross section of a solid core Bragg fiber fabricated through MCVD technology; b) Nonlinear spectral broadening in 3 cm of this Bragg fiber showing the input spectrum and for 19 kW, 59 kW, and 82 kW of launched peak powers from an optical parametric amplifier (OPA). OPA was tuned to 1067 nm and FWHM of the launched pulse was 120 fs (After Bookey et al, 2009; ©2009 OSA). 6. Conclusion In this chapter we have attempted to provide a unified summary description of the most important propagation characteristics of an optical fiber followed by discussion on several variety of special fibers for realizing fiber amplifiers, dispersion compensating fibers, microstructured optical fibers, and so on. Even though huge progress has been made on development of optical fibers for telecom application, a need for developing special fibers, not necessarily for telecom alone, has arisen. This chapter was an effort to describe some of these special fibers. Detailed discussions are given on our own work related to inherently gain-flattened EDFA, DCFs of large mode effective area, index-guided MOF and Bragg fibers for realizing dispersion compensation, for metro network centric applications, and for generating super continuum light. 7. Acknowledgement The author acknowledges many interesting discussions and exchange of ideas in the course of gathering cumulative knowledge in this field with his colleagues Ajoy Ghatak, M. R. Shenoy, K. Thyagarajan, and Ravi Varshney. He is also grateful to his graduate students namely, Sonali Dasgupta, B. Nagaraju, and Kamna Pande, for many fruitful discussions during their thesis work, which led to several publications with them on specialty fibers, which are referred to in this chapter. Manu Mehta carried out and executed many of the design calculations as part of her M.Tech. Dissertation at our Institute on application specific index guided holey fiber structures, which were based on use of the CUDOS software, made available to us by B. Eggleton and Boris Kuhlmey from University of Sydney. This work was partially supported by our ongoing Indo-UK collaboration project on Application Specific Microstructured Optical Fibers under the UKIERI scheme sponsored by the UK Government and the Indo-French Network collaboration project on Specialty Optical Fibers and Amplifiers sponsored by DST (Govt. of India) and French Ministry of Research. Frontiers in Guided Wave Optics and Optoelectronics 26 8. References Agrawal, G. P. (2007), Nonlinear Fiber Optics, Fourth edition, Academic Press, San Diego. Agrawal, G. P. (2006a), Fiber optic Raman amplifiers in Guided Wave Optical Components and Devices: basics, Technology, and Applications, B. P. Pal (Ed.), pp. 1-25, Elsevier Academic Press, Burlington & San Diego. Argyros, A., Eijkelenborg, M. V., Large, M. and Basset, I. 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(2000), Single-mode propagation in to depressed-core-index photonic bandgap fiber designed for zero-dispersion propagation at short wavelength, Electron. Lett., Vol. 36, pp. 514-515. Bromage, J. (2004), Raman amplification for fiber communication systems, IEEE J. lightwave Tech., Vol. 22, pp. 79-93. Cox, F.M., Argyros, A. and Large, M .C. J. (2006), Liquid-filled hollow core microstructured polymer optical fiber, Opt. Exp., Vol. 14, pp. 4135-4140. Dasgupta, S., Pal, B. P. and Shenoy, M. R. (2005), Design of dispersion compensating Bragg fiber with ultrahigh figure of merit, Opt. Lett., Vol. 30, pp. 1917-1919. Dasgupta, S. (2006), Personal Communication. Dasgupta, S., Pal, B. P. and Shenoy, M. R. (2006), Photonic bandgap guided Bragg fibers in Guided Wave Optical Components and Devices: basics, Technology, and Applications, B. P. Pal (Ed.), pp. 1-25, Elsevier Academic Press, Burlington & San Diego. Dasgupta, S., Pal, B. P. and Shenoy, M. R. 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C., 2002, Multipole method for microstructured optical fibers,.II. Formulation, J. Opt. Soc. Am. B, Vol.19, pp. 2331-2340. Kumar, N., Shenoy, M.R., Pal, B.P. (2005), A standard fiber-based loop mirror as a gain- flattening filter for erbium-doped fiber amplifiers, IEEE Photon. Tech. Lett., Vol. 17, pp. 2056-2058. Li, S., Chiang, K. S., Gambling, W. A. (2001), Gain flattening of an erbium-dped fiber amplifier using a high-birefringence loop mirror, IEEE Photon. Technol. Lett., Vol. 13, pp. 942-944. Li, T. (1995), The impact of optical amplifiers on long-distance lightwave communications, Proc. IEEE, Vol. 81, pp. 1568-1579. Mehta, M. (2009), M.Tech. (Optoelectronics and Optical Communication) dissertation Studies on Microstructured Optical Fibers, IIT Delhi. Mears, R.J., Reekie, L., Poole, S. B. and Payne, D. N. (1986), Low-threshold tunable cw and Q-switched fiber laser operating at 1.55 μm, Electron. Lett., Vol. 22, pp. 159-160. Mears, R. J., Reekie, L., Jauncy, I. M. and Payne, D. N., (1987), Low-noise fiber amplifier operating at 1.54 μm, Electron. Lett., Vol. 23, pp. 1026-1027. Miya, T., Terunume, Y., Hosaka, T. and Miyashita, T. (1979), An ultimate low-loss single- mode fiber at 1.55 μm, Electron. Lett., Vol. 5, pp. 106-108. Monro, T. M. (2006), Microstructured Optical fibers in Guided Wave Optical Components and Devices: basics, Technology, and Applications], B. P. Pal (Ed.), pp. 1-25 Elsevier Academic Press, Burlington & San Diego. Nagaraju, B., Paul, M. C., Pal, M., Pal, A., Varsheny, R. K., Pal, B. P., Bhadra, S. K., Monnom, G. and Bernard, D. (2009), Design and fabrication of an intrinsically gain flattened Erbium doped fiber amplifier, Opt. Comm., Vol. 282, pp. 2335-2338. Okuno, T., Onishi, M., Kashiwada, T., Ishikawa, S. and Nishimura, M. (1999), Silica-based functional fibers with enhanced nonlinearity and confinement loss trade-offs, IEEE J. Select. Top. Quantum Electron., Vol. 5, pp. 1385-1391. Pal, B. P. (1995), Optical transmission in Perspective in Optoelectronics, S. S. Jha (Ed.), pp. 195- 297, World Scientific, Singapore. Pal, B. P. (2006), Optical fibers for broadband lightwave communication: evolutionary trends in designs in Guided Wave Optical Components and Devices: basics, Technology, and Applications, B. P. Pal (Ed.), pp. 1-25, Elsevier Academic Press, Burlington & San Diego. Pal, B. P. and Pande, K. (2002), Optimization of a dual-core dispersion slope compensating fiber for DWDM transmission in the 1480-1610 nm band through G.652 single- mode fibers, Opt. Comm., Vol. 201, pp. 335-344. Pal, B. P., Dasgupta, S. and Shenoy, M. R. (2005), Bragg fiber designs for transparent metro networks, Opt. Exp., Vol. 13, pp. 621-626. Pal, B.P., Dasgupta, S. and Shenoy, M. R. (2006), Supercontinuum generation in a Bragg fiber: a novel proposal, Optoelectron. Letts., Vol. 5, pp. 342-344. Frontiers in Guided Wave Optics and Optoelectronics 28 Pan, J.Y., Ali, M. A., Elrefaie, A. F., and Wagner, R. E. (1995), Multi-wavelength fiber amplifier cascades with equalization employing Mach-Zehnder optical filter, IEEE Photon. Technol. Lett., Vol. 7, pp. 1501-1503. Pande, K. and Pal, B. P. (2003), Design optimization of a dual-core dispersion compensating fiber with high figure of merit and a large mode effective area for dense wavelength division multiplexed transmission through standard G.655 fibers, App. Opt., Vol. 42, pp. 3785-3791. Payne, D. N. and Gambling, W. A. (1975), Zero material dispersion in optical fibers, Electron. Lett., Vol. 11, pp. 176-178. Pone, P., Dubois, C., Guo, N., Gao, Y., Dupuis, A., Boismenu, F., Lacroix, S. and Skorobogatiy, M. (2006), Drawing of the hollow all-polymer Bragg fibers, Opt. Exp., Vol. 14, pp. 5838-5852. Ramachandran, S. (Ed.) (2007), Fiber-based Dispersion Compensation, Springer-Verlag, Berlin. Ramachandran, S. (2006), Dispersion-tailored higher order mode fibers for in-fiber photonic devices in Guided Wave Optical Components and Devices: Basics, Technology, and Applications], B. P. Pal (Ed.), pp. 291-310, Elsevier Academic Press, Burlington & San Diego. Ryan, J. (2002), Fiber considerations for metropolitan networks, Alcatel Telecom. Rev., Vol. 1, pp. 52-56. Skorobogatiy, M. (2005), Efficient ant-guiding of TE and TM polarizations in low index core waveguides without the need of omnidirectional refelector, Opt. Lett., Vol. 30, pp. 2991-2993. Sun, Y, Sulhoff, J. W., Srivastava, A., Zysking, J. L., Srasser, T. A., Pedrazzani, J. R., Wolf, C., Zhou, J., Judkins, J. B., Espindola, R. P., and Vengsarkar, A. M. (1997), 80 nm ultra wideband erbium doped silica fiber amplifier, Electron. Lett., Vol. 33, pp. 1965-1967. Srivastava, A. and Sun, Y. (2006), Erbium-doped fiber amplifiers for dynamic optical networks in Guided Wave Optical Components and Devices: Basics, Technology, and Applications], B. P. Pal (Ed.), pp. 181-204, Elsevier Academic Press, Burlington & San Diego. Thyagarajan, K., Diggavi, S., Taneja, A. and Ghatak, A. K. (1991), A simple numerical technique for the analysis of cylindrically symmetric refractive index profile optical fiber, Appl. Opt., Vol. 30, pp. 3877-3879. Thyagarajan, K. and Pal, B. P. (2007), Modeling dispersion in optical fibers: applications to dispersion tailoring and dispersion compensation in Optical Fiber Communication Reports, Ramachandran, S. (Ed.), Vol. 4, pp. 173–213, Springer-Verlag, Berlin. Urquhart, W. P. and Laybourn, P. J. (1985), Effective core area for stimulated Raman scattering in single-mode optical fibers, Proc. Inst. Elect. Eng., Vol. 132, pp. 201–204. Xu, Y., Yariv, A., Fleming, J. G. and Lin S. Y. (2003), Asymptotic analysis of silicon based Bragg fibers, Opt. Exp., Vol. 11, pp. 1039-1049. Varshney, R. K., Nagaraju, B., Singh, A., Pal, B. P., and Kar, A. K. (2007), Design and Realization of an All-Fiber Broadband Tunable Gain Equalization Filter for DWDM Signals, Opt. Exp., Vol. 15, pp. 13519-13530. Vengsarkar, A. M., Lemaire, P.J., Judkins, J. B., Bhatia, V., Erdogan, T., Sipe, J. E. (1996), Long period fiber gratings as band rejection filters, IEEE J. Lightwave Tech., Vol. 14, pp. 58-65. Yablonovitch, E. (1987), Inhibited spontaneous emission in solid-state physics and electronics, Phys. Rev. Letts., Vol. 58, pp. 2059-2062. Yeh, P., Yariv, A. and Marom, E. (1978), Theory of Bragg fiber, J. Opt. Soc. Am., Vol. 68, pp. 1196-1201. 2 Nonlinear Properties of Chalcogenide Glass Fibers Jas S. Sanghera, L. Brandon Shaw, C. M. Florea, P. Pureza, V. Q. Nguyen, F. Kung, Dan Gibson and I. D. Aggarwal Naval Research Laboratory USA 1. Introduction Chalcogenide glasses are based on the chalcogen elements S, Se and Te with the addition of other elements such as Ge, As and Sb to form of stable glasses (Borisova, 1981). Due to their large IR transparency, fibers fabricated from these glasses are ideal for transmission of high power IR light. Several applications of chalcogenide fibers for IR transmission have been documented (Sanghera et al., 2005a). Also of interest is the high nonlinearity of these glass compositions. The high χ (3) nonlinearities of chalcogenide glasses make them excellent candidates for applications such as all optical processing, Raman amplification, parametric amplifiers and supercontinuum generation. 2. Glass preparation Chalcogenide glasses are melted directly in quartz ampoules using chemicals purified via distillation/sublimation (Sanghera et al., 1994a). Typical melt temperatures range from 600 o C to 900 o C, depending upon composition. The liquids are quenched and the glass rods annealed at temperatures around the appropriate softening temperatures. The optical fibers are obtained by the double crucible (DC) process (Sanghera et al., 1995). The DC process enables adjustments to be made in the core/clad diameter ratio during fiber drawing by independent pressure control above each melt. Therefore both multimode and single mode fibers can be drawn with relatively few processing steps. 3. Fiber properties Figure 1 compares the losses routinely obtained for a couple of chalcogenide glasses along with the lowest (“champion”) losses reported in the literature (Sanghera et al., 1994b; Churbanov, 1992). Depending upon composition, the sulfide, selenide and telluride based fibers transmit between about 0.8-7 μm, 1-10 μm, and 2-12 μm, respectively. Therefore, the practical applications dictate the type of fiber to be used. As-S fibers loss routinely achieved is about 0.1-0.2 dB/m in fiber lengths of about 500 meters. Losses for As-Se fibers typically range from 0.5 to 1 dB/m in the near IR around 1.5 µm. Frontiers in Guided Wave Optics and Optoelectronics 30 Wavelength (µm) 0123456789101112 Loss (dB/km) 10 1 10 2 10 3 10 4 (a) (b) (c) (d) Fig. 1. Transmission loss spectra of (a) lowest loss sulfide fiber, (b) typical sulfide fiber, (c) lowest loss telluride fiber, and (d) typical telluride fiber. 4. Nonlinear properties It is well established that the values of χ (3 ) for chalcogenide glasses are about two orders of magnitude larger than silica (Nasu et al, 1989; Richardson et al, 1998). More recently, glasses have been reported with non-linearities approaching 1000 times silica (Lenz et al., 2000; Harbold et al., 2002). These large nonlinearities would allow small compact low power devices for telecommunications. The subpicosecond response of these nonlinearities is ideal for high data rate telecommunication devices. For efficient nonlinear devices utilizing the optical Kerr effect, the nonlinearity must be high and the nonlinear absorption must be low. A figure of merit FOM = n 2 /(βλ) can be defined as a useful metric to determine optimum compositions, where n 2 is the nonlinear index and β is the nonlinear absorption. For isotropic medium, one and two photon resonant processes dominate the third-order susceptibility. For frequencies approximately half of the material resonance, two photon processes resonantly enhance the nonlinear index n 2 . Normally, however, the two photon resonance enhancement is accompanied by two photon absorption which competes with the nonlinear index n 2 . In the case of amorphous materials such as chalcogenide glass, an exponential Urbach tail exists and its absorption edge extends below the half gap. This edge leads to two photon absorption (TPA) below the half gap and thus n 2 may increase faster than TPA absorption in this region. Consequently, the best performance in terms of nonlinear index strength vs. TPA (FOM) will occur just below the gap. Figure 2 shows the bandgap of the As-S-Se system vs. Se concentration. Here, the bandgap is defined at the point of 10 3 cm -1 absorption. In the graph, Se content of 0 at. % corresponds to pure As 40 S 60 while Se content of 60 at. % corresponds to pure As 40 Se 60 . The bandgap of the glass system decreases with Se content. For operation at 1.55 µm (0.8 eV), we would expect an optimum composition of As 40 Se 60 where E g /hν ~ 0.45. This is borne out by experimental data. Spectrally resolved two beam coupling measurements of As-S-Se system have been performed to determine the magnitude of the nonlinear index n 2 and the two photon Nonlinear Properties of Chalcogenide Glass Fibers 31 Se content (at%) 0 10203040506070 Band Gap (eV) 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 Fig. 2. Bandgap of As-S-Se glass system (defined at the point of 10 3 cm -1 absorption). absorption coefficient. Details of these measurements can be found in (Harbold et al., 2002). Figure 3 shows the results of these measurements. Values for As-S were found to be ~220 times higher than for silica at 1.55 µm and increased with Se substitution of S to a value of ~930 times higher than silica for As-Se. Likewise, two photon absorption also increases with increasing Se content. This data can be used to calculate the FOM for the As-Se system (Figure 4). As expected, the glasses with the largest FOM for operation at 1550 nm occurs for E g /hν at ~0.45 which is the As-Se composition (Slusher et al., 2004). Normalized Photon Energy (hυ/E gap ) 0.30 0.35 0.40 0.45 0.50 0.55 0.60 n 2 / (n 2 silica) 200 400 600 800 1000 1200 1400 TPA (cm/GW) 0 1 2 3 1550 nm 1250 nm [Se] Normalized Photon Energy (hυ/E gap ) 0.30 0.35 0.40 0.45 0.50 0.55 0.60 n 2 / (n 2 silica) 200 400 600 800 1000 1200 1400 TPA (cm/GW) 0 1 2 3 1550 nm 1250 nm [Se] Fig. 3. n 2 and TPA absorption of As-S-Se glass system. High speed optical processing has been demonstrated by exploiting these high nonlinearities in chalcogenide glass fiber and waveguides. Earlier work on all optical switching in chalcogenide fiber was performed by Asboe (Asobe et. al. 1993) who demonstrated switching of an 80-GHz pulse train in a 2 meter length of As 2 S 3 based fiber using an optical kerr shutter configuration. More recently, 640 Gb/s demultiplexing has been demonstrated in a 5 cm long chalcogenide rib waveguide on silicon by utilizing FWM (Galili et. al. 2009). 40 Gb/s all optical wavelength conversion has also been demonstrated in chalcogenide tapered fibers (Pelusi, et. al. 2008). Here, a CW laser at the conversion wavelength was modulated by XPM with the co-propagating 40 Gb/s signal. Frontiers in Guided Wave Optics and Optoelectronics 32 Normalized Photon Energy (hυ/Egap) 0.30 0.35 0.40 0.45 0.50 0.55 0.60 FOM 1 10 1550 nm 1250 nm Normalized Photon Energy (hυ/Egap) 0.30 0.35 0.40 0.45 0.50 0.55 0.60 FOM 1 10 1550 nm 1250 nm Fig. 4. FOM for As-S-Se glass system. 5. Raman amplification Figure 5 shows the normalized Raman spectra of As 40 S 60 , As 40 Se 60 , and silica. As 40 Se 60 glass has a much narrower Raman line (~60 cm -1 ) than silica glass (~250 cm -1 ). In addition, the Raman shift for As 40 Se 60 glass is much smaller (~240 cm -1 ) than the Raman shift of silica glass (~440 cm -1 ) due to the heavier atoms present in the chalcogenide glass. Previous studies have looked at stimulated Raman scattering in As 40 S 60 glass, a very similar glass system to As 40 Se 60 (Asobe et al., 1995). These studies found the Raman gain coefficient of As 40 S 60 to be almost two orders of magnitude higher than that of silica. It was also found that this enhancement in the Raman gain roughly corresponded to the enhancement in the nonlinear index, n 2 . Consequently, one might expect to see an even larger Raman gain coefficient in As 40 Se 60 since the selenide glass has shown an even larger nonlinearity and also a narrower Raman spectrum. 0 0.2 0.4 0.6 0.8 1 1.2 0 100 200 300 400 500 600 700 800 Raman Shift (cm -1 ) Raman Intensity (normalized) Silica glass Δν ~ 250 cm -1 As-S Δν ~85 cm -1 As-Se Δν ~60cm -1 Fig. 5. Raman spectra of As 2 S 3 and As 2 Se 3 glass. Silica glass is shown for reference. Nonlinear Properties of Chalcogenide Glass Fibers 33 Raman amplification at 1.55 µm has been demonstrated in small core As-Se fiber (Thielen et al., 2003a). The results of the Raman amplification experiment are shown in shown in Figure 6. Over ~23 dB of gain was achieved in a 1.1-meter length of fiber pumped by a nanosecond pulse of ~10.8 W peak power at 1.50 µm. The peak of the Raman gain was shifted by ~230 cm -1 to 1.56 µm. The Raman gain coefficient was estimated to be ~300 times silica in this experiment. More recent measurements of the Raman gain coefficient show a value of about 780x greater than that of silica (Slusher et al. 2004). 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1470 1490 1510 1530 1550 1570 1590 1610 1630 Wavelength (nm) Signal (V) 0 0.002 0.004 0.006 0.008 0.01 0.012 Signal (V) ~230 cm -1 Signal with pump Pump w/o signal Signal only Pump Fig. 6. Raman amplification in As-Se fiber. Shown is amplifier output with signal and no pump, pump and no signal (showing background stimulated Raman scattering (SRS) resulting from pump), and amplified signal with pump. The large Raman gain coefficient of chalcogenide glass coupled with its large IR transparency show promise for lasers and amplifiers in the near and mid-IR. The potential for Raman lasers and amplifiers can be assessed by defining a figure of merit (FOM). The expression for single pass gain, G A , in a Raman fiber laser is given by [1]: 0 exp Reff A eff gPL G A ⎛⎞ = ⎜⎟ ⎜⎟ ⎝⎠ (1) Where g R is the Raman gain coefficient, P 0 is the pump power, A eff is the fiber effective area and L eff is the fiber effective length. The fiber effective length is given by () 11 1 L eff Le α α α −⋅ = −≈ (2) Where α is the fiber loss. For long lengths, L eff is approx 1/ α . From these equations, the gain is proportional to exp (-g R / α ) for long fiber lengths. Thus, the value g R / α can be used as a rough FOM for Raman amplification. Table 1 compares the performance of an As-Se Raman fiber laser or amplifier operating at 4 µm to a silica Raman fiber laser or amplifier operating in the telecommunications band at 1.5 µm. Here, the Raman gain coefficient of As-Se, g R , which is measured to be 780x silica at 1.5 µm is extrapolated to it value in the mid-IR since Frontiers in Guided Wave Optics and Optoelectronics 34 the Raman gain coefficient scales inversely with wavelength. α is the fiber loss. For silica, a loss of 0.2 to 0.3 dB/km is typical of telecommunication grade fiber. For As-Se, two losses are given. The loss of 200 dB/km is typical of “champion losses” achieved at NRL for As-Se fiber while the loss of 3 dB/km is theoretical loss for As-Se fiber (Devyatykh et al., 1992). For the loss of 200 dB/km, g R / α for an As-Se fiber Raman amplifier operating at 4 µm is about 0.38 compared to 1.1 for a silica fiber Raman amplifier. For the theoretical loss of 3 dB/km, g R / α for As-Se fiber operating at 4 µm is 23 times that of silica fiber operating at 1.5-µm. 237.5 x 10 -6 3 0.345 x 10 -4 200 1.7 x 10 -10 4As-Se Fiber 1.1~6 x 10 -7 0.2-0.30.65 x 10 -12 1.5Silica Fiber FOM ( 10 -6 W -1 ) α (cm -1 ) Loss (dB/km) g R (cm/W) λ (µm) 237.5 x 10 -6 3 0.345 x 10 -4 200 1.7 x 10 -10 4As-Se Fiber 1.1~6 x 10 -7 0.2-0.30.65 x 10 -12 1.5Silica Fiber FOM ( 10 -6 W -1 ) α (cm -1 ) Loss (dB/km) g R (cm/W) λ (µm) Table 1. Figure of merit for Raman amplification in As-Se fiber at 4-µm compared Raman amplification in silica fiber at 1.5-µm. The loss value of 200 dB/km (a) for As-Se is typical of a “champion” loss value. The loss value of 3 dB/km (b) is theoretical loss. A Raman laser has been demonstrated in As-Se fiber by Jackson (Jackson et. al. 2000). They generated 0.64 W of first Stokes at 2062 nm with a slope efficiency of 66% under 2051 nm pumping in a 1 meter length 6 µm core, 0.19 NA fiber. Reflection off the endface of the fiber (~22% at normal incidence) was used for feedback at the output end of the fiber while a broadband Au-coated mirror was used as a back reflector. Note that the braodband nature of the cavity reflectors allowed the Raman laser to oscillate on a number of vibrations. The line at 2062 nm was attributed to interlayer vibrations of As 2 Se 3 . Raman output at 2102 from bond bending vibrations and at 2166 nm for bond stretching vibrations were also observed. Stimulated Raman scattering (SRS) has been observed in the mid- IR. Figure 7 shows the SRS in a ~ 1m length of As-Se fiber under CW CO laser pumping at ~ 5.4 µm. The SRS is seen at ~ 6.1 µm. Raman laser operating in the wavelength range of from 6.1 to 6.4 µm would have applications in laser surgery. These wavelengths correspond to amide bands in 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 5000 5200 5400 5600 5800 6000 6200 6400 6600 6800 7000 Wavelength (nm) Signal (V) 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 Signal (V) CO Pump Laser Raman Signal Fig. 7. SRS signal observed at 6.1 µm under ~5.4 µm CO laser pumping. [...]... America 48 Frontiers in Guided Wave Optics and Optoelectronics Slusher, R.; Hodelin, J.; Sanghera, J.; Shaw, L and Aggarwal, I (20 04) JOSA-B, Vol 21 , pp 1146 Song, K.; Herráez, M and Thévenaz, L (20 05) Observation of pulse delaying and advancement in optical fibers using stimulated Brillouin scattering Opt Expr 13, pp 82- 88 Song, K.; Abedin, K.; Hotate, K.; Herráez, M and Thévenaz, L (20 06) Highly... mode was launched Using the NA and V-number values, the Mode Field Diameter (MFD), d1/e2, for the fundamental mode will be given by Eq 4 and is listed in Table 2: 38 Frontiers in Guided Wave Optics and Optoelectronics 0 -10 21 mW 23 mW -20 -30 -40 -50 -60 -70 0 -10 27 mW 30 mW -20 -30 -40 -50 Wavelength (nm) -60 -70 1548 .25 1548.35 1548.45 1548.55 1548.65 1548.75 Fig 12 Typical spectra of the reflected... prior to being coupled into the fiber, is modulated (sine wave at 25 MHz) with a LiNbO3 modulator and a DS345 signal generator The output is then passed through a variable optical attenuator (VOA) and detected with a fast photodiode and an amplifier on an oscilloscope The VOA allowed us to control the signal on the detector such 42 Frontiers in Guided Wave Optics and Optoelectronics that we maintained the... make such devices feasible in the near term 11 References Abedin, K (20 06) Observation of strong stimulated Brillouin scattering in single-mode As2Se3 chalcogenide fiber Opt Express 13, pp 1 026 6-1 027 1 Abedin, K.; Lu, G and Miyazaki, T (20 08) Electron Lett 44 , pp 16 Asobe, M.; Kanamori, T.; Naganuma, K.; Itoh, H and Kaino, T (1995) Third-order nonlinear spectroscopy in As2S3 chalcogenide glass fibers... into optically inactive species A short review of the main intrinsic absorption bands occurring in the UV spectral range will be given in the following The ubiquitous and most easily induced absorption features in the UV range is the band at about 21 3 nm (5.8 eV), attributed to the E’ centers (Pacchioni et al., 20 00; Skuja, 1998) This band is characterized by an oscillator strength, f, of about 0 .2, ... (20 06) Stimulated Brillouin scattering in single-mode As2S3 and As2Se3 chalcogenide fibers Opt Express, 14, 120 63- 120 70 Galili, M; Xu, J; Mulvad, H; Oxenlowe, L;, Clausen, A; Jeppesen, P; Luther-Davies, B; Madden, S; Rode, A; Choi, D; Pelusi, M; Luan, F; and Eggleton, B (20 09) Breakthrough switching speed with an all-optical chalcogenide glass chip: 640 Gbit/s demultiplexing, Opt Exp, 17, pp 21 82- 2187... Aggarwal, I., (20 08) Raman response function and supercontinuum generation in chalcogenide fiber, Proc Conference on Lasers and Electro -Optics (CLEO) 20 08, Optical Society of America Ippen, E and Stolen, R (19 72) Stimulated Brillouin scattering in optical fibers Appl Phys Lett., 21 , pp 539-541 Jackson, S; and Anzueto-Sanchez, G; (20 06) Chalcogenide glass Raman fiber laser, Appl Phys Lett., 88, p 22 1106 Jáuregui,... stimulated Brillouin scattering (SBS) in optical fibers has attracted interest as it allows a very simple and robust implementation of tunable optical pulse delays, using mostly standard telecom components Especially important are nonsilica-based fibers with higher nonlinearity since these require lower powers and shorter lengths for practical implementations 40 Frontiers in Guided Wave Optics and Optoelectronics. .. Fibers 1National Sporea Dan1, Agnello Simonpietro2 and Gelardi Franco Mario2 Institute for Lasers, Plasma and Radiation Physic, Laser Metrology Laboratory, 2University of Palermo, Department of Physical and Astronomical Sciences 1Romania, 2Italy 1 Introduction Intrinsic and extrinsic optical fiber-based sensors are promising devices to be used in very different and complex environments, by their very nature:... (9) It is important to keep in mind that this FOM essentially determines what length and power are needed in a system to achieve a certain gain, and hence a certain time delay The FOM as defined above in Eq 9 tends to be a quantity which obscures the physical meaning contained in Eq 8 Actually, the theoretical gain (Gth), expressed in dB, as given by Eq 10, could be used instead to compare different . 3400 320 0300 028 00 26 0 024 0 022 0 020 00 Wavelength (nm) AsSe AsS Laser Sulfide fiber PCF selenide fiber Selenide fiber Laser Normalized Power () Frontiers in Guided Wave Optics and Optoelectronics. value in the mid-IR since Frontiers in Guided Wave Optics and Optoelectronics 34 the Raman gain coefficient scales inversely with wavelength. α is the fiber loss. For silica, a loss of 0 .2. Using the NA and V-number values, the Mode Field Diameter (MFD), d 1/e 2 , for the fundamental mode will be given by Eq. 4 and is listed in Table 2: Frontiers in Guided Wave Optics and Optoelectronics