View of OPTICAL FIBER COMMUNICATION USING EDFA

(1)

Vol.03, Issue 08, August 2018, Available Online: www.ajeee.co.in/index.php/AJEEE

1

OPTICAL FIBER COMMUNICATION USING EDFA

NIDHI SINGHAI, M.Tech Scholar, BTIRT Sagar

RITU DUBEY, Asst. Prof. BTIRT Sagar

Abstract - Generally, Amplifiers are used to amplify the signals in communication systems.

Chances of loss of a signal reduces when a signal is amplified by some means. Here EDFA is used to amplify the signal in optical communication system. Optical fiber communication is revolutionary trending in the field of communication system now days. Erbium Doped Fiber Amplifier’s (EDFA’s) have revolutionized the optical communications world by expanding the applications for which optical fiber is a solution. Today it is possible to have links greater than 10,000 km with EDFA’s cascaded with 50 km spacing as opposed to repeaters being used every few kilometers. EDFA’s allow for a complete optical link whereas repeaters required for electro-optic conversions and more components. Wavelength division multiplexing (WDM) has become very popular with the development of EDFA’s. EDFA’s have been a vital component in optical communications for the past decade and should continue to evolve. The many advantages and few disadvantages of the EDFA, make it the best technology has to offer today. In this research work some aspects of EDFA are analyzed and simulated in MATLAB. Pump wavelength of 980nm and 1550nm are employed to judge the Gain power and ASE noise power along the length of the fiber. It has been concluded that the pump wavelengths of 980 nm is widely used because it commercially available with high power and give the best noise figure and gain numbers. As for the wavelength vs. noise figure, wavelengths above 1.52 µm give a noise figure close to 3 dB which is the theoretical limit. Wavelengths in the range of 1520 to 1560 nm are typically used for EDFA’s.All amplifiers have an upper limit on their output power, increasing the input power further will not produce any change in the output beyond this point.

1. INTRODUCTION

As signals travel in optical communication systems, they are attenuated by optical fiber. Eventually, after some distance they can become too weak to be detected. One possible way to avoid this situation is to use optical amplifiers to increase the amplitude of the signal [12]. Doping a part of the optical fiber core by (Er3+) ions in presence of external pumping power will lead to form the EDFA.The performance of this optical amplifier depends on (the power and the wavelength of the pumping laser, the power and wavelength of the input signal, amplifier length, ion concentration). These parameters will affect the characteristics of EDFA such as amplifier gain, gain saturation, noise figure and output power [12, 13].The gain is provided by pumping a medium, which undergoes population inversion when stimulated by an optical signal. Thus, an optical amplifier functions in much the same way as a laser. These devices are characterized by their gain efficiency, or the gain as a function of input power (dB/mW). Only a certain range of optical frequencies, called the gain bandwidth,

can be amplified by a particular device.

All amplifiers have an upper limit on their output power, increasing the input power further will not produce any change in the output beyond this point. This effect is called gain saturation. There are various types of noise sources that affect optical amplifiers; in particular, these devices are sensitive to the polarization of the input light. Polarization sensitivity refers to the variations in amplifier gain with changes in the signal polarization.In this chapter, the EDFA properties are examined using the rate equations and the propagation equations. The propagation equations are solved analytically using a novel method which are coincided the numerically methods. The graded order is very important factor that may be influenced the EDFA characteristics.The proposed analytical solution may be found for any graded order, while the well-known solutions presented only for the step index fibre.

1.1 Importance Of EDFAS in WDM Systems

(2)

2 Wavelength division multiplexing (WDM) technology was developed in order to increase the capacity of single channel optic communications employed at the time. By allocating a different wavelength to each channel and then multiplexing them into a single fiber, WDM is able to exploit the large bandwidth offered by optical fibers, dramatically increasing the capacity of a link.

WDM solutions, either DWDM or CWDM, became extensively used in long haul transmission systems. Originally the architecture of WDM systems used electronic devices called repeaters, periodically placed along the link.

Repeaters reconstruct and retransmit optical signals through optical-electrical- optical (OEO) conversion, a process that converts optical signals into the electrical domain, regenerates them using a 3R scheme (Retiming, Reshaping and Rescaling) before converting them back into the optical domain for transmission (see Figure 3.1) [19]. One of the main advantages of repeaters is that they ensure that network impairments such as noise, attenuation, dispersion and nonlinearities are compensated at each network node.

Figure 2.1 - Block diagram of a Repeater

However, using repeaters presents two main issues:

- First, the OEO conversion is a complex process and increases the overall cost of the system;

- Second, the system is not transparent because of the OEO conversion, and so it cannot be used for parallel transmission of different data format on different wavelength (WDM).

A way of overcoming these disadvantages would be to avoid the OEO conversion and develop a purely optical device. EDFAs are transparent devices

insensitive to bit rates or signal formats.

Their low intrinsic losses, long fluorescence times and high gain over a large bandwidth means they can accommodate and amplify numerous WDM signals simultaneously.

Additionally, EDFAs are not only cheaper to produce, but also easier to upgrade once implemented. Their inclusion in WDM links increased the distance between repeaters, allowing for optical signals to the transmitted over distances of more than a 1000 kilometres.

1.2 Single-Stage EDFA

In its most basic form EDFA consist of an EDF spool (typically ranging from 10 to 30 meters), a semiconductor laser diode (either a 980 𝑛𝑚 or a 1480 𝑛𝑚 pump) and a WDM coupler, a device that separates or combines optical signals at a certain operating wavelength. WDM couplers show high isolation between two determined wavelengths with low excess loss making them extensively used in EDFA architecture, as a way of efficiently combining the pump input with signals in the third transmission window. A manageable amplifier however, has additional devices in its structure as shown in Figure 3.3:

Tap coupler: device which function is to divert a small percentage of the signals power, usually about 1%, to a photodetector connecter to the EDFA’s control unit. The exact number of tap couplers depends on the size and complexity of the amplifier in question, but at least two are inserted so as to monitor the signals’ power at the input and output of the amplifier.

Isolator: optical component capable of allowing light to propagate in a favoured direction, severely attenuating light travelling in directions opposite to it.

Figure 3.1 - Architecture of a typical Single-Stage EDFA

(3)

3 2. METHODOLOGY

The proposed is based on simulation of EDFA with Pumping wavelength of 980nm and 1550nm using Forward Pumping Scheme. The proposed methodology consist of either the single input Source (1550nm) or the Multiple Wavelength source with different channels (1520nm- 1610nm) whose output is given to the isolator. An isolator is a device which allows the propagation of light in only one direction with zero reflections. By using forward pumping scheme, the output of an isolator is combined with the pump signal in a WDM Coupler. Wavelength Division Multiplexing (WDM) coupler used is the one that combines the input signal and the pump signal and it passes this combined signal to the EDFA.Firstly, the pump power is kept constant and input signal power is varied and secondly the input power is kept constant and Pump power is varied.An isolator is a device which allows the propagation of light in only one direction with zero reflections. By using Co-directional or forward pumping scheme, the output of an isolator is combined with the pump signal in a WDM Coupler. Wavelength Division Multiplexing (WDM) coupler used is the one that combines the input signal and the pump signal and it passes this combined signal to the EDFA design software utilizes this model with all the components shown in the blocks.

Parameters for the pump source (here used as 980nm), input signal source (single/multi wavelength) are varied so as to obtain optimized results. Graphs can be seen in the software itself for each changed value of parameters such as pump power and input signal power. The observations for required parameters such as gain, Noise figure and ASE can be carried out. Probe is used here between input and output to check overall gain and noise figure of the EDFA system. For the whole operation, amplifying process of the EDFA is same and it is very important to know the amplifying process of the EDFA. Flow chart of EDFA amplifying process is shown below.

3. RESULTS

(4)

4

3. CONCLUSION

The work proposed and simulated the EDFA model with single and multi- wavelength sources using pumping source of 980 nm and 1550nm wavelength. The various results were also compared. It is important to understand the desired range of wavelength used in EDFA which provides efficient results.

Along with source wavelength if other parameters like length, pump power, signal power are changed, then optimized values of gain and noise figure are obtained. Thus, it is shown that the proposed model of an EDFA utilizing both single and multi-wavelength sources were successfully simulated using WDM. For each pump power signal power is changed and we observed the changes in gain and noise figure. The impact of change on ASE i.e. the major noise component in EDFA systems is also shown. Any of the desired condition of maximum gain and low noise or minimum ASE can be achieved using the values shown in the proposed results and also without changing each and every component. It may be observed that the Gain is optimized and Noise Figure initially decreases with increase in Pump Power and then attains the same value.

REFERENCES

1. Vishal Srivastava, Munish Singh, “Gain Analysis of EDF Amplifier Based WDM System Using Different Pumping Wavelength”, IOSR Journal of Electronics and Communication Engineering (IOSR- JECE) e-ISSN: 2278-2834, p- ISSN: 2278- 8735.Volume 10, Issue 6, Ver. II (Nov - Dec .2015), PP 114-120.

2. G. Ivanovs, V. Bobrovs, S. Olonkins, A.

Alsevska, L. Gegere, R. Parts, P. Gavars and G. Lauks, “Application of the erbium- doped fiber amplifier (EDFA) in wavelength division multiplexing (WDM) transmission systems”, International Journal of Physical

(5)

5

Sciences, Vol. 9(5), pp. 91-101, 16 March, 2014DOI: 10.5897/IJPS2013.4066Article Number: 770DF9D46836ISSN 1992 - 1950

3. Ming Xia, , Massimo Tornatore, Yi Zhang, Pulak Chowdhury, Charles U. Martel, and Biswanath Mukherjee, “Green Provisioning for Optical WDM Networks”, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 17, NO. 2, MARCH/APRIL 2011.

4. Jyoti Gujral, Vishu Goel, “Analysis of Augmented Gain EDFA Systems using Single and Multi-wavelength Sources”, International Journal of Computer Applications (0975 – 888) Vol. 47– No.4, June 2012.

5. A. Temmar, H. Ould Saadi and A. Boutaleb,

“Simulation based Analysis of Erbium doped Fiber amplifier”, Journal of Applied Science 6(4): 789-794, 2006, ISSN 1812- 5654.

6. Mohammed A. Elaydi, Fady I. El-Nahal,

“Symmetric 80 Gbps Next Generation Passive Optical Network Stage Two NG- PON2, IUG Journal of Natural Studies”

Peer-reviewed Journal of Islamic University-Gaza, ISSN 2409-4587 IUGNESVol. 25, No 2, 2017, pp 135-140.

7. Anuja Dhokar, S.D.Deshmukh, “Overview Of EDFA for the Efficient Performance Analysis”, IOSR Journal of Engineering (IOSRJEN) ISSN (e): 2250-3021, ISSN (p):

2278-8719 Vol. 04, Issue 03 (March. 2014),

||V4|| PP 01-08.

8. A. Cem COKRAK Ahmet ALTUNCU, “Gain and Noise Figure Performance of Erbium Doped Fiber Amplifiers (EDFA)”JOURNAL OF ELECTRICAL & ELECTRONICS ENGINEERING, Vol. 4, 2004.

9. Prince Jain, Neena Gupta, “Comparative study of all Optical Amplifiers”, International Journal of Scientific &

Engineering Research, Volume 5, Issue 11, November-2014 ISSN 2229-5518.

10. Haruki Ogoshi, Seiji Ichino and Katsuya Kurotori, “Broadband Optical Amplifiers for DWDM Systems”, Optical Sub-systems Dept., FITEL Products Div.

11. Shivani Radha Sharma, Tanvi Sood, “Gain Flattening of EDFA using Hybrid EDFA/Raman Amplifier with Reduced Channel Spacing”, IJEDR Volume 3, Issue 3 ISSN: 2321-9939, 2015.

12. Giridhar Kumar R*, Iman Sadhu**, Sangeetha N, “Gain and Noise Figure Analysisof Erbium Doped Fiber Amplifier by Four Stage Enhancement andAnalysis”, International Journal of Scientific and Research Publications, Volume 4, Issue 4, April 2014 1 ISSN 2250-3153.

13. Farah Diana Binti Mahad, Abu Sahmah Bin Mohd Supa’at, “EDFA Gain Optimization for WDM System”, ELEKTRIKA, Vol. 11, NO. 1, 2009, 34-37.