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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 12, December 2017, pp. 1075–1082, Article ID: IJMET_08_12_116

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=12

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

ANALYZING DISPERSION COMPENSATION

USING UFBG AT 100GBPS OVER 120KM USING

SINGLE MODE FIBER

Ashwani Sharma, Shalini Sharma

School of Electrical and Computer Sciences, Shoolini University, Solan (H.P)-173229

Ashwani Sharma, Inder Singh

School of Computer Science Engineering, UPES, Dehradun (U.K)-248007

Suman Bhattacharya

Product Evangelist, TATA Consultancy Services

ABSTRACT

The origin of erbium doped fiber amplifiers (EDFA’s) is making the transmission

in optical fiber communication more irresistible. But already installed standard non

dispersion shifted fibers causing the transmission of data at higher rates to be

confined by the immense dispersion unless different compensation technologies are

utilized. A number of methodologies have been introduced to resolve this issue, for

example, DCF (Dispersion Compensating Fiber), FBG(Fiber Bragg Grating),

Electronic Equalizers etc. but an approach to decrease the chromatic dispersion by

using FBG can altogether intensify the performance of the system. This paper is

demonstrating the use of uniform FBG for compensating dispersion at 100Gbps over a

SMF of 120Km by using it in distinct schemes and then on the basis of Q-factor and

BER, it has been analyzed that Post dispersion compensation is reducing the effects of

dispersion at longer distances with high data transmission rates much better than the

remaining schemes.

Keywords: Optisystem 7.0; Single mode fiber (SMF) Quality-factor; Bit error rate;

Chromatic Dispersion; Uniform Fiber Bragg Grating(UFBG); Inter-symbol interference

Cite this Article: Ashwani Sharma, Inder Singh, Suman Bhattacharya and Shalini

Sharma, Analyzing Dispersion Compensation using UFBG at 100Gbps over 120km

using single mode fiber, International Journal of Mechanical Engineering and

Technology 8(12), 2017, pp. 1072–1082.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=12

Analyzing Dispersion Compensation using UFBG at 100Gbps over 120km using single mode fiber


1. INTRODUCTION

With the brisk growth in the communication industry all over the world, the optical fiber

communication networks with high data rate and high capacity is becoming a vital part in

present day communication systems. For the most part, there are three key issues related with

the optical fiber systems i.e that is, loss during transmission, nonlinear effects and dispersion.

The development of EDFA has reduced the effects caused by transmission loss which was a

major problem earlier. But dispersion is a matter of concern when high data rate transmission

over long distances is considered [1].

1.1. Dispersion:

Pulses while propagating inside the optical fiber propagates at different velocities and lost

their original shape. Due to distinct propagation speeds, they arrive at receiver at distinct time

intervals, thereby, causing the pulses to be broadened and overlap with each other. This pulse

broadening is called dispersion. Dispersion is a common term related with it and effect is

known as inter-symbol interference (ISI). The relation of β� with Dispersion parameter (D) is

given below in equation (1):-

D � �2πc

λ�β��1

When wavelength λ� λ� then the fiber is said to have normal dispersion (β� � positive . In this dispersion, components having low frequency propagate at a rate faster than

components having high frequency. The opposite concept takes place when β� �

negative[2].

1.2. Dispersion Types:

Dispersion can be divided into three types- Intermodal dispersion, Intramodal dispersion

(chromatic dispersion) and Polarization mode dispersion.

1.2.1. Intermodal Dispersion

Due to occurrence of delay between higher order and low order modes causes the pulse

widening at the receiver and this effect is intermodal dispersion. It is shown in Figure 1.

Figure 1 Intermodal Dispersion representation Figure 2 Chromatic Dispersion (CD)

1.2.2 Chromatic Dispersion:

In single mode fibers, the light pulses comprises of distinct frequency elements and these

elements travels inside the optical fiber core with different velocity, thereby, causing pulse

widening at the receiver. This phenomenon of pulse widening is called chromatic dispersion.

The detailed diagram is shown in Figure 2.

1.2.3 Polarization Mode Dispersion:

In case of single mode fiber, there are generally two polarization modes exists, which are

perpendicular to each other. This is because of the results of birefringence. Every mode has

their own speed of propagation which is greater or less than the other causing dispersion,

popularly known as polarization mode dispersion as shown in Figure 3.

Ashwani Sharma, Inder Singh, Suman Bhattacharya and Shalini Sharma


Figure 3 PMD

1.3. Techniques for Dispersion Compensation:

There are different techniques which are available for the compensation of dispersion. Fiber

Bragg Gratings (FBG) and Dispersion Compensating Fibers (DCF) are the most popular

techniques for dispersion compensation.

1.3.1 Dispersion compensation using DCF:

By changing the structure of the fiber, A fiber with negative dispersion value can be designed.

And the resultant fiber is termed as Dispersion compensating fibers, [3]. Figure 4 is showing

the principle operation of DCF.

Figure 4 DCF Technique

1.3.2 Dispersion compensation by FBG:

It is the most popular technique for dispersion compensation. Fiber Bragg Grating (FBG)

allows some of the wavelengths to travel in the forward direction, and reflects others hence,

behaving like mirror as shown in Figure 5. Different types of FBG are there like uniform FBG

and Chirped FBG. A Grating is called Uniform Grating, if it has constant refractive index

modulation period, whereas Chirped FBG contains the variation of the refractive index period

with respect to the length [5].

Figure 5 Uniform FBG

Fiber Bragg grating provides the dynamic compensation of dispersion. This feature of

dynamic compensation is not provided by DCF [6].There are so many advantages of FBG

merits over other dispersion compensation techniques like less insertion loss and increased

capacity of the optical fiber. [7].

2. SIMULATION SETUP

This paper focuses on the simulations of the Uniform Fiber Bragg Grating in three distinct

configurations i.e. Pre compensation, Post compensation and Mix compensation. Eventually,

the results are compared in terms of the Q-factor and BER to determine the best configuration

among the three. FBG parameters and the Simulation parameters are explained in the tabular



form in the Table-3 and Table-4, respectively. Further the simulation models of three distinct

configurations of uniform FBG i.e. Pre, Post and Mix compensation are shown in the Figures-

6, 7 and 8, respectively.

This section of the paper shows the execution of Dispersion compensation by utilizing

uniform Fiber Bragg Grating as a Dispersion compensator with the help of software naming

Optisystem 7.0. This work has been shown for the single channel. Simulation setups are been

executed both at the transmitter end and the receiver end. In the transmitter segment, setup is

started with a PRBS generator which creates irregular grouping of bits consistently. Then a

modulator called Mach-Zehnder modulator, in which one input from non-return to zero

(NRZ) modulation format and another input from CW laser, which is behaving as light

source, is provided. The modulated optical signals are then transmitted over the optical

channel at a rate equivalent to 100Gbps with input power extending from 1dBm to 10dBm.

Simulations are completed at a frequency of 193.1THz. Received signals are encounters by

pin detector which behaves as transducer i.e. converting the optical signals into the electrical

signals. The position of UFBG has been changed to see its effect on the data transmission

pulses and bandwidth. The adjustment in the position of UFBG in three unique plans i.e. Pre

Compensation, Post Compensation and Mix Compensation. EDFA is likewise utilized as a

part of model to reduce attenuation and subsequently utilized after every component of

Uniform Fiber Bragg Grating. This paper concentrates on the simulation of the Uniform Fiber

Bragg Grating in three different designs i.e. Pre Compensation, Post Compensation and Mix

Compensation. Inevitably, the outcomes are looked at as far as the Q-factor and BER to

decide the best design among the three. Parameters for UFBG and the parameters for

simulation are clarified in the Table-1 and Table-2, separately. Further the simulation models

of three particular setups of uniform FBG i.e. Pre, Post and Mix compensation are appeared in

the Figures-6, 7 and 8, individually.

Table 1 Parameters used for UFBG

Sr. No. Parameter Value

1 Length of Fiber 120 Km

2 Noise Threshold -100 dB

3 Reflectivity 0.99

4 Sample Rate 500 GHz

Table 2 General parameters used in Simulation

Sr. No. Parameter Value

1 Bit Rate(Gbps) 100

2 Bandwidth(THz) 1

3 Extinction Ratio(dB) 30

4 Sample Rate(THz) 6.4

5 Power(dBm) 1-10

6 Gain(dB) 20

7 Noise(dB) 2

8 Frequency(THz) 193.1



Figure 6 Pre compensation using Uniform Fiber Bragg Grating simulation model

Figure 7 Post compensation model Figure 8 Mix compensation model

3. SIMULATIONS RESULTS AND DISCUSSION

This part of the paper contains the examination of the results acquired after studying and

analyzing the Uniform Fiber Bragg Grating as a Dispersion compensator in three particular

setups that are Pre compensation, Post Compensation and Mix compensation. The results are

analyzed as per the BER, Q-Factor, Eye height and received power. Figures-9,10 and 11

demonstrating the eye charts of Pre, Post and Mix Dispersion compensation utilizing uniform

Fiber Bragg Grating, resp. The indicated eye diagrams are at input power =10dBm as at this

power level different schemes of uniform FBG exhibiting the maximum Q-Factor and

minimum BER when compared with other power levels from 1dBm to 10dBm. Table-3,4 and

5 is containing the Q-Factor, BER, received power and eye heights of three schemes at

different power levels.

Figure 9 UFBG Post comp. Figure 10 UFBG Post comp. Figure 9 UFBG Mix comp.



Table 3 Results for Pre Compensation of Uniform FBG at inputs from 1dbm to 10dbm

Input

Power

Max Q

factor Min BER Eye Height Threshold

Received

Power(dBm)

1 7.86135 1.78E-12 0.000301 0.000291 1.26E-07

2 9.13437 3.02E-20 0.000412 0.000319 1.89E-07

3 10.5549 2.18E-26 0.000555 0.000354 2.90E-07

4 12.1228 3.56E-34 0.000737 0.000398 4.49E-07

5 13.8473 5.75E-44 0.000969 0.000441 7.01E-07

6 15.7283 4.15E-56 0.001263 0.000504 1.10E-06

7 17.7594 6.10E-71 0.001637 0.000561 1.74E-06

8 19.9478 6.47E-89 0.002112 0.00065 2.74E-06

9 22.2657 3.25E-11 0.002714 0.000763 4.33E-06

10 24.7116 3.18E-13 0.003477 0.000838 6.86E-06

Table 4 Results for Post Compensation of Uniform FBG at inputs from 1dbm to 10dbm

Input

Power

Max Q


Received

Power(dBm)

1 10.5753 1.56E-26 0.00036 0.0001132 1.09E-07

2 11.913 4.04E-33 0.0004752 0.0001343 1.73E-07

3 13.369 3.55E-41 0.0006205 0.0001531 2.73E-07

4 14.9508 5.97E-51 0.0008056 0.00018449 4.32E-07

5 16.663 9.12E-63 0.00104 0.0002099 6.85E-07

6 18.512 6.11E-77 0.00133935 0.00023831 1.09E-06

7 20.5079 6.61E-94 0.001718 0.0002698 1.72E-06

8 22.6786 2.55E-11 0.002197 0.0002909 2.72E-06

9 25.028 1.04E-13 0.002805 0.00033431 4.31E-06

10 27.54 1.95E-16 0.00357 0.0003932 6.84E-06

Table 5 Results for mix Compensation of Uniform FBG at inputs from 1dbm to 10dbm

Input

Power

Max Q


Received

Power(dBm)

1 7.86036 1.79E-15 0.000301 0.000291 1.75E-07

2 9.13275 3.07E-20 0.000413 0.000319 2.52E-07

3 10.5523 2.24E-26 0.000555 0.000354 3.72E-07

4 12.1191 3.72E-34 0.000737 0.000397 5.58E-07

5 13.8391 6.43E-44 0.000969 0.000441 8.49E-07

6 15.7154 5.08E-56 0.001263 0.000502 1.30E-06

7 17.7315 1.02E-70 0.001638 0.000581 2.02E-06

8 19.8949 1.86E-88 0.002112 0.000644 3.15E-06

9 22.1653 3.02E-10 0.002715 0.000752 4.93E-06

10 24.5084 4.73E-13 0.003477 0.000819 7.75E-06

It is observed that Post dispersion compensation is having highest Quality factor and

lowest BER (bit error rate) which is the desired condition for the best compensation

technique.



Figure 12 Input Power Vs Q- Factor Plot Figure 13 Power Vs BER Plot

Figure 14 Power Vs Eye Height Plot Figure 15 Input Power Vs Received Power Plot

By analyzing all the graphs, it is clear that post compensation of uniform FBG Performing

batter at 100 Gbps. for 120 Km.

4. CONCLUSION

This paper is completely revolved around executing Dispersion Compensation procedure

using uniform FBG remembering the true objective to compensate for the dispersion occurs

while the transmission of signal over a separation of 120 Km at 100 Gbps. Uniform FBG is

used in three particular setups i.e. Pre, Post and Mix Dispersion compensation. Results from

the particular courses of action are then analyzed as far as the BER and Q-Factor so as to

acquire the best compensation method among them. The diagrams appeared in Fig-12, 13, 14

and 15 are analyzed and it is discovered that the Post Dispersion compensation have

predominant Quality Factor and minimum BER when compared with the Pre and Mix

compensation of uniform FBG. However, complete removal of dispersion at higher

transmission rates is not possible but using Post compensation in uniform FBG can reduced

dispersion up to some extent at 100Gbps over 120Km using SMF.

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