**9. Conclusion**

Wavelength multiplexing (WDM) technology along with optical amplifiers is used for optical communication systems in S-band, C-band and L-band. To improve the overall system performance Hybrid amplifiers consisting of cascaded TDFA and EDFA with different gain bandwidths are preferred for long haul wavelength multiplexed optical communication systems. It has found that calculated value of F ratio is very much different from the tabulated value, so the difference between parameters is considered as significant and we reject the null hypothesis. Here, we are able to conclude that for WDM systems, TDFA-EDFA hybrid fiber doped amplifier has higher gain and lower noise figure. So, this configuration gives better performance in WDM systems as compared with the EDFA-TDFA hybrid configuration. With this design it has also been found that when TDFA with EDFA are cascaded in series then gain spectrum is broadened. The gain variation is less than ± 2.5% in the wavelength region of 1460-1560 nm. The TF filter is so designed that transmission loss occurs around the maximum gain of hybrid amplifier i.e. at 1531nm. The transmission loss is about 9dB.The simulation process can be represented by a flowchart as shown in figure 13.

Fig. 11. Schematic Diagram of the dielectric multi-layer Interference Filter (TFF)

Fig. 12. Broadened and Flattened Gain Spectrum of Hybrid Amplifier

Wavelength multiplexing (WDM) technology along with optical amplifiers is used for optical communication systems in S-band, C-band and L-band. To improve the overall system performance Hybrid amplifiers consisting of cascaded TDFA and EDFA with different gain bandwidths are preferred for long haul wavelength multiplexed optical communication systems. It has found that calculated value of F ratio is very much different from the tabulated value, so the difference between parameters is considered as significant and we reject the null hypothesis. Here, we are able to conclude that for WDM systems, TDFA-EDFA hybrid fiber doped amplifier has higher gain and lower noise figure. So, this configuration gives better performance in WDM systems as compared with the EDFA-TDFA hybrid configuration. With this design it has also been found that when TDFA with EDFA are cascaded in series then gain spectrum is broadened. The gain variation is less than ± 2.5% in the wavelength region of 1460-1560 nm. The TF filter is so designed that transmission loss occurs around the maximum gain of hybrid amplifier i.e. at 1531nm. The transmission loss is about 9dB.The simulation process can be represented by a flowchart as

**9. Conclusion** 

shown in figure 13.

Fig. 13. Flowchart Showing Simulation Process

Hybrid Fiber Amplifier 121

Komukai T., Yamamoto T., Sugawa T andMiyajima Y, "Upconversion Pumped Thulium-

Lee Y.W, Nilsson J, Hwang S.T. and Kim S.J., "Experimental Characterization of a

Lobo Audrey Elisa, Besley James A. and C.Martijin De Sterke, " Gain Flattening Filter

Lu Yi Bin and Chu P.L., "Gain Flattening by Using Dual-Core Fiber in Erbium Doped Fiber

Mynbaev D.K, L.L.Schiner' *"Fiber Optics Communications Technology*", Pearson Education,

Oliveira J.C. .Silva R.F., Rossi S.M, Rosolem J.B. and .Bordonalli A.C, "An EDFA Hybrid

Suppressed Transients", *IMOC 2007,* pp. 683-687, 2007 SBMO/IEEE MTT-S. Olsson N.A., "*Lightwave Systems with Optical Amplifiers",* Journal of Lightwave Tech. Vol. 7,

Ono Hirotaka, Yamada Makoto and Ohishi Yasutake, "Broadband and Gain Flattened Amplifier

Parallel Configuration", *Electronics Letters*, Vol. 33, No. 8, pp. 710-711, May 1997. Park Seo Yeon, Kim Hyang Kyun, Lyu Gap Yeol, Sun Mo Kang and Sang Yung Shin,

Pasquale F. D. and Federighi M., "Modeling of Uniform and Pair –Induced Up Conversion

Percival R.M. and Williams J.R, "Highly Efficient 1.064µm Upconversion Pumped 1.47µm

Qiao Lijie and Vella Paul J., "ASE Analysis and Correction for EDFA Automatic Control,"

Roy F., Sauze A., Baniel P. and Bayart D., "0.8-µm +1.4µm Pumping for Gain Shifted TDFA

Sakamoto Tadashi, Aozasa Shin- ichi, Yamada Makoto and Shimizu Makoto, "Hybrid Fiber

Sohn Ik-Bu, Baek Jang Gi, Lee Nam Kwon, Kwon Hyung Woo and Song Jae Won, "Gain

Sun .Y, Judkins J.B., Srivastava A.K., Garrett L.,J.L.Zyskind, Sulhoff J.W, Wolf C., Derosier R.M.,

*Photonics Technology Letters,* Vol. 10, No. 6, pp. 787-789, June1998.

*Lightwave Technology,* Vol.13, pp. 1858-1864, 1995.

*Journal of Lightwave Te*ch. Vol. 25, No.3, May 2007.

*Electronics Letters,* Vol.38, No. 22, pp. 1324-1325, Oct. 2002.

*Photonics Technology Letters*, Vol. 9,No. 3, pp. 386-388, March 1997.

*Appl.* Vancouver, BC, Canada, Jul.2002, PD4.

*Lightwave Tech.* Vol. 24 No.6 , June 2006.

*Quantum Electronics*, Vol. 31, pp. 1880-1889, Nov. 1995.

12, pp. 1612-1614, Dec.1996.

2000.

July 1989.

1684-1685, June 1994.

Vol. 21, No. 9, pp. 2084-2088, 2003.

Delhi, Inc.,2003, ISBN 81-7808-317-5.

Doped Fluoride Fiber Amplifier and Laser Operating at 1.47µm," *Journal of* 

Dynamically Gain –Flattened EDFA", *IEEE Photonics Technology Letters*, Vol. 8, No.

Design Using Rotationally Symmetric Crossed Gratings*", Journal of Lightwave Tech*.

Amplifier*",IEEE Photonics Technology Letters*, Vol. 12, No. 12, pp. 1616-1617, Dec.

Gain Control Technique for Extended Input Power and Dynamic Gain Ranges with

Composed of a 1.55µm- Band and a 1.58 µm- Band Er3+- Doped Fiber Amplifier in a

" Dynamic Gain and Output Power Control in a Gain-Flattened EDFA", *IEEE* 

Mechanisms in High-Concentration Erbium Doped Silica Waveguides*," Journal of* 

Thulium Doped Fluoride Fiber Amplifier," Electron Letters, Vol. 30, No. 20, pp.

With Power Conversion Efficiency Exceeding 50%," Presented at *the Opt. Amplifiers* 

Amplifier Consisting Of Cascaded TDFA and EDFA for WDM Signals*", Journal of* 

Flattened and Improved EDFA Using Microbending Long-Period Fiber Gratings",

Gnauck A.H., R.W.Tkach, J.Zhou, Espindola R.P., Vengsarkar A.M and Chraplvy A.R., "EDFA Transmission Response to Channel Loss in WDM Transmission System*", IEEE* 

#### **10. References**


Agarwal Govid P., "*Fiber Optic Communication Systems*", John Wiley & sons, Inc. Publication,

Aozasa S., H.Masuda, T. Sakamoto, K.Shikano and M.Shimizu, "Gain-Shifted TDFA

Arbore .M.A., Y. Zhou, G.Keaton and T.Kane, "34 dB Gain at 1500nm in S- Band with

Bakshi B., M.Vaa, E.A.Golovchenko, H.Li and G.T. Harvey, " Impact of Gain Flattening

Becker P.C, Olsson N.A. and. Simpson J.R, "*Erbium Doped Fiber Amplifiers*". New York:

Desurvire Emmanuel, "*Erbium Doped Fiber Amplifiers- Principles and Application*", Hoboken,

Hwang B. C. et al., "Cooperative Up- Conversion and Energy Transfer of New High Er+3

Kasamatsu T., Yano Y. and Ono T., "Gain-Shifted Dual –Wavelength- Pumped Thulium-

Kaur Inderpreet, Gupta Neena, "Statistical Analysis of Different Configurations of Hybrid

Kaur Inderpreet, Gupta Neena, "Enhancing the Performance of WDM Systems By Using

Kaur Inderpreet, Gupta Neena,, "Increasing the Amplification Bandwidth of Erbium Doped

Kawai Shingo, Masuda Hiroji, Suzuki Ken Ichi, Aida Kazuo, "Wide Bandwidth and Long

Keiser Gerd, "*Optical Fiber Communications*", 4th Edition, Tata McGraw-Hill Education Pvt.

Kemtchou J., M. l, Chatton F. and Lecoy T. G., "Comparision of Temperature Dependences

Kim Hyo Sang, Yun Seok Hyun, Hyang Kyun, Kim Namkyoo Park and Kim Byoung Yoon,

NJ: John Wiley & Sons, Inc. ISBN 0-471-58977-2,2002 Chapter 5.

*IEEE Photonics Technology Letters,* Vol. 13, No. 1, pp.31-33,2001.

*Photonics Technology Letters*, Vol. 11, pp. 886-888, July 1999.

Ltd., New Delhi, Inc. 2009, ISBN-13: 978-0-07-064810-4.

*Opt. Amplifiers Appl*., 1996, pp. 126-129, Paper FD2.

*Communication 2001* Vol. 3, pp. 448-449, Sept. 2001.

*Conference*, Patiala, India, pp 106- 109, Feb 2010.

*2008,* P.284, Dec. 2008 at IIT, Delhi.

Employing High Concentration Doping Technique with High Internal Power Conversion Efficiency of 70%,"*Electron. Letters*, Vol. 38, No. 8, pp. 361-363,2002. Aozasa S, Hiroji Masuda, Makoto Shimizu and Makoto Yamada, "Novel Gain Spectrum

Control Method Employing Gain Clamping and Pump Power Adjustment in Thulium- Doped Fiber Amplifier*" Journal of Lightwave Tech*. Vol. 26, No.10, May

Distributed ASE Suppression," presented at Eur. Conf. Opt. Commun., Denmark,

Filter Ripple in long Haul WDM Systems*", Proc. 27th Eur. Conference on Optical* 

and Er+3 – Yb+3 Doped Phosphate Glasses," *Journal of Optical Society of America*, Vol.

Doped Fiber Amplifier for WDM Signals in the 1.48-1.51-µm Wavelength Region*,"* 

Doped FiberAmplifiers*", International Journal of Electrical and Electronics Engineering*

TFF in Hybrid Amplifiers", 2010 *IEEE 2nd International Advance Computing* 

Fiber Amplifiers by Using a Cascaded Raman-EDFA Configuration*", Photonics* 

Distance WDM Transmission Using Highly Gain Flattened Hybrid Amplifier*, IEEE* 

of Absorption and Emission Cross – Section in Different Hosts of EDFAS," *Proc.* 

" Actively Gain-Flattened EDFA Over 35nm by Using All-Fiber Acousto-Optic Tunable Filters", *IEEE Photonics Technology Letters*, Vol. 10, pp. 790-792, June1998.

**10. References** 

2003.

2008.

Sept. 2002.

Academic, 1999, Chapter 7.

17, No. 5, pp. 833-839, 2000.

3:8 2009 pp 515-520.


**5** 

**Physical-Layer Attacks in** 

Marija Furdek and Nina Skorin-Kapov

*University of Zagreb* 

*Croatia* 

**Transparent Optical Networks** 

For the past decades, network traffic has been showing immense growth trends, as we are witnessing the rapid development of network applications such as Internet Protocol TV (IPTV), peer-to-peer traffic, grid computing, multi-player gaming etc. Optical fiber, with its huge capacity of up to 50 THz, low bit error rate of 10-12, low loss of 0.2 dB/km and low noise and interference characteristics has been widely accepted as a viable future-proof solution to meet the ever-increasing network bandwidth demands. In comparison with the available fiber capacity, the speed of edge electronic equipment of only a few Gb/s creates a bottleneck, so fiber bandwidth is divided into independent wavelength sets, each capable of carrying traffic between a pair of nodes at different speeds. This is the underlying principle of Wavelength Division Multiplexing (WDM), where different wavelengths supporting communication between different end users are multiplexed and carried simultaneously over the same physical fiber. Under normal operating conditions, carried wavelengths do not significantly interfere with each other inside the fiber. At the receiver's side, they are demultiplexed or filtered to ensure that every receiver receives the intended wavelength. An

In Transparent Optical Networks (TONs), signals do not undergo optical-electronical-optical (OEO) conversion at the intermediate nodes they traverse. Communication takes place entirely in the optical domain, via all-optical channels called lightpaths. The process of establishing lightpaths consists of finding a physical route and assigning a wavelength to

**1. Introduction** 

illustration of WDM principle is shown in figure 1.

Fig. 1. Example of a simple WDM system.

