Effect of Pump Wavelength on Gain Spectra for Single-pumped
Fiber Optical Parametric Amplifiers
Weiwei Fan, Pramod R. Watekar, Won-Taek Han*
Department of Information and Communications, School of Photon Science and Technology, Gwangju Institute of Science and Technology (GIST),Republic of Korea.
Tel: 062-970-2215, Fax: 062-970-2204, E-mail: [email protected]
Abstract Pump wavelength dependence of the gain spectra was investigated by simulating the model of single-pumped
fiber optical parametric amplifiers (FOPAs). Conditions for the single-pumped FOPAs having broad bandwidths with relatively large gains were optimized and the gain bandwidth was found to be as large as 146.4 nm when signal power and pump power were 316 nW and 7 W, respectively.
1. Introduction
Recently, fiber optical parametric amplifiers (FOPAs) have drawn much attention because they exhibited bandwidths of several hundred nanometers compared with the Erbium-doped fiber amplifiers (EDFAs) and the Raman amplifiers (RAs) [1]. Another advantage for the FOPAs is that FOPAs rely not on the properties of doping ions but on the third-order optical nonlinearity of the fiber material. Hence FOPAs can be operated at an arbitrary center wavelength (corresponding to the zero-dispersion wavelength 0 of the fiber), which provides the opportunities for increasing OPA bandwidths that are not available with the EDFAs or the RAs [2, 3].
In this study, we simulated the conditions for the single-pumped FOPAs to find the effect of dispersion on the gain spectra. The zero dispersion wavelength (ZDWL) of the fiber, fiber length, nonlinear coefficient, signal power and pump power used for the simulation were 1550 nm, 200 m, 2 W-1 /Km, 316 nW and 7 W, respectively.
2. Simulation and results
Based on the degenerate FWM process, the signal power at the end of a fiber of length L can be expressed as [4]
)], ( ) 4 / 1 ( 1 [ ) 0 ( ) ( 3 2 2 2 3 L P g Sinh gL P
(1) where the parametric gain coefficient g and the phase mismatch
are given by( ) ( /2) , 2 1. 2 2 1 P P g
(2) To simulate the conditions efficiently,
was expanded in power series up to fourth-order expansion4 3 1 4 2 3 1 2 1 0 4 1 0 3 ( ) 12 1 ) )( ) ( 2 1 ) ( ( (3)
Fig.1 Signal gain spectra versus the signal wavelength for: (a)
p
00.55 nm and (b) different pump wavelengths equal to or longer than
0.By shifting only the pump wavelength parameter, the results were studied in detail. Fig. 1(a) shows the gain spectra at pump wavelengths
p
00.55nm and the bandwidth was found to decrease when the pump wavelength was tuned toward the shorter-wavelength side. The pump wavelength should be longer than the ZDWL of the fiber to have a broad bandwidth because 3 and 4 are positive (1.2×10-40
S3 m-1 and 2.5×10-55 S4 m-1 are used here) for most of silicate fibers. In Fig. 1(b), the bandwidths were enhanced by tuning the pump wavelength toward the longer-wavelength side though the gain spectra were not smooth. When the signal wavelength moved to the longer-wavelength side, the linear mismatch might be negative, and this could compensate the nonlinear phase mismatch to achieve a broad gain bandwidth.
The maximum signal gain was 9.46 dB when the pump wavelength coincided with the ZDWL of the fiber. The gain bandwidth with gain larger than 9.46 dB was plotted with respect to pump wavelength in Fig. 2(a) and the optimized pump wavelength was around 1550.726 nm. The broadest gain bandwidth was 146.4 nm with the optimized pump wavelength. The same result was confirmed when the gain bandwidth was plotted with respect to signal wavelength as shown in Fig. 2(b), and the maximum bandwidth was found to be about 146.4 nm.
3. Conclusion
In summary, we investigated the effect of pump wavelength on the gain spectra of single-pumped FOPAs on the basis of the FWM theory. The gain spectra were found to be very sensitive to the pump wavelength. For every specified FOPA, the optimized pump wavelength can be found when the bandwidth requirement dominates the gain flatness.
Acknowledgments
This research work was partially supported by KOSEF through the National Core Research Center program (No. R15-2006-022-02001-0), by the Top Brand Project (Photonics 2020), and the Brain Korea-21 project, Ministry of Education, Science and Technology, Korea.
References
1. M. E. Marhic, "Fiber Optical Parametric Amplifiers, Oscillators and Related Devices," (2007).
2. M. E. Marhic, N. Kagi, T. K. Chiang, and L. G. Kazovsky, "Broadband fiber optical parametric amplifiers," Opt. Lett.
21, 573-575 (1996).
3. F. Yaman, Q. Lin, S. Radic, and G. P. Agrawal, "Impact of dispersion fluctuations on dual-pump fiber-optic parametric amplifiers," Photonics Technology Letters, IEEE 16, 1292-1294 (2004).
4. G. P. Agrawal, Nonlinear Fiber Optics, 3rd ed. (Academic Press, San Diego, 2001).
Fig.2. (a) Signal gain bandwidth versus pump wavelength ; (b) Signal gain versus signal wavelength when pump
wavelength was equal to 1550.726 nm (red color) and the straight line was at 9.46 dB gain (blue color)
