Abstract: In this paper dispersion compensating fiber and their performance in optical communication system has been analyzed. Dispersion compensating fibers are under fast rapid development to achieve the effective dispersion compensation, wavelength stability, good coupling to fibers. Dispersion compensating fiber is a fiber that is used to reduce the pulse spreading. In this paper the overall communication length is taken as 120km. In that single mode fiber is 100km and dispersion compensating fiber is 20km. Three compensation
approaches are proposed (pre-compensation,
post-compensation, symmetrical-compensation). This proposed idea is implemented using OptSim simulation software at 10Gbps. The performance evaluated from the output parameters like Q-factor, BER.
IndexTerms-- Dispersion compensation, BER, Q-factor, DCF, SMF.
I. INTRODUCTION
The field of optical communication offers very high speed data transmission over the long distance. However this performance is reduced by some parameters like dispersion, attenuation. Attenuation is generated by bending of fiber and scattering of optical signal. It is reduced by repeaters and amplifiers. Dispersion is a main parameter to reduce the transmission distance. Dispersion is mainly classified into two types. That is intermodal dispersion and intramodal dispersion. Intermodal dispersion is happen in multimode fiber and intramodal dispersion (i.e.) chromatic dispersion is happen in single mode fiber. Single mode fiber dispersion is further classified into material dispersion, waveguide dispersion and polarization mode dispersion. Material dispersion and waveguide dispersion involves in group delay and group velocity. So, in order to avoid the dispersion, dispersion compensating fiber is used.
Manuscript received April, 2016
R. Sumathy, Assistant Professor, ECE Department, Kalasalingam University, Virudhunagar, Tamilnadu, India
A. Muthu Kumar, Associate Professor, ECE Department, Kalasalingam University, Virudhunagar, Tamilnadu, India
M. Sundara Moorthi, UG Student, ECE Department, Kalasalingam University, Virudhunagar, Tamilnadu, India
S. Maha Suresh, UG Student, ECE Department, Kalasalingam University, Virudhunagar, Tamilnadu, India
B. Suresh Kumar, UG Student, ECE Department, Kalasalingam University, Virudhunagar, Tamilnadu, India
In section II present the spreading of pulses. In section III, present the dispersion compensation techniques. In section IV present the dispersion compensating fiber. In section V present proposed approaches using DCF. In section VI, present the result and analysis. In section VII, present the conclusion of the paper.
II. SPREADING OF PULSES
Dispersion is nothing but spreading of input pulse due to chromatic dispersion. There will be an expansion in time duration. From the fig.1 input signal peak power is narrow beam width after travel along the fiber the output signal peak power is wider in beam width. Pulse spreading due to different wavelengths of light propagates at different velocities through the fiber because of refractive index of the fiber.
Fig.1
Chromatic dispersion consists of material dispersion and waveguide dispersion [4]. Material dispersion is due to the wavelength depends on the refractive index of the fiber (i.e.) refractive index of the core varies as a function of wavelength.
σ
mat= L |D
mat(λ) | σ
λ ────→ (1)Where,
σ
mat-
r.m.s value of pulse broadening,L
- Length of the fiber,σ
λ-
r.m.s value of spectral width,D
mat – dispersion parameter.Reducing the Pulse Spreading At 10Gbps in
Optical Communication System Using
Dispersion Compensating Fiber
the remaining 20% of the light signal is refracted out towards the cladding. This is happening for shorter wavelength light signal but for the longer wavelength light signal is very difficult to confine the light within the core.
σ
wg= L |D
wg(λ) | σ
λ ────→ (2) Where,σ
wg-
r.m.s value of pulse broadening,σ
λ-
r.m.s value of spectral width,
D
wg – dispersion parameter.Due to this dispersion all the pulses are getting broadening in output side these pulses are overlapping to the other pulse this is known as ISI (i.e.) inter symbol interference [3].
Fig.2 overlapping output pulses
III. DISPERSION COMPENSATION TECHNIQUES
In order to improve the performance of optical communication system dispersion compensation techniques is implemented. Dispersion compensation techniques are classified as dispersion compensating fiber, fiber Bragg gratings, higher order mode fiber and digital filters [3]. Among these in this paper dispersion compensating fiber is used, because of advantages complication is less. Dispersion compensating fiber has low insertion loss, no need to external appliance of any other devices. In this paper dispersion compensating fiber is fabricated from single mode fiber by changing the dispersion parameters of the fiber.
IV. DISPERSION COMPENSATING FIBER
Dispersion compensating fiber is a more effective method for dispersion compensation. Single mode fiber has second order, third order positive dispersions. Negative dispersion is created in the dispersion compensating fiber. Fiber and dispersion compensating fiber mixing in the ratio of 5:1i.e 100 km fibers and 20km dispersion compensating fiber [2]. In this project positive dispersion value of the single mode fiber is considered as 16, 18, 20, 22, etc. Dispersion compensating fibers are created with the negative dispersion values are -70, -80, -90, etc. In order to compensate the positive dispersion of the single mode fiber combined with the dispersion compensating fiber. So, the overall average dispersion values nearly close to zero [2]. Three different dispersion compensation approaches are based on the placement of dispersion compensating fiber in an optical link
(pre-compensation, post-compensation, and
symmetrical-compensation). In first approach dispersion compensating fiber is placed before the single mode fiber. In
second approach dispersion compensating fiber is placed after the single mode fiber. In third approach dispersion compensating fiber is placed both the end of the single mode fiber or mixing of other two approaches [7]. All these approaches are analyzed better one is selected for the further consideration. The range of positive dispersion value and negative dispersion value is analyzed.
V. PROPOSED APPROACHES USING DCF
OptSim simulation software is used to implement the optical communication system. OptSim is nothing but optical simulation. It is a trial and error method. It is a block based simulation tool. OptSim features are nearly 600-700 components, fast learning curve, user-friendly. In simulation parts for transmitter side the input data is generated by pseudo code random number generator. It will generate the sequence randomly at 10Gbps, the output data is given to NRZ driver. CW laser source frequency range is193.1THz. NRZ output code and laser source given to the optical modulator. For channel side 100 km single mode fiber and 20km dispersion compensating fiber is present. For receiver side optical signal detected by PIN photo detector. It will convert the optical signal into electrical signal. That electrical signal has some amount of noise it is recovered by the Bessel electrical filter. The scope is used to analyze the output of electrical signal. It will show the eye diagram. Typical three compensation approach is shown in below figures.
Fig.3 pre-compensation
Fig.5 symmetrical-compensation
VI. RESULT AND DISCUSSION
The specific range of the positive dispersion is 18 in a single mode fiber and the negative dispersion is -90 in a dispersion compensating fiber are the new approaches in this paper. Eye diagram for the three approaches are analyzed and the output parameters like Q-factor and BER values are tabulated. Table.1 shows the pre-compensation techniques. Table.2 shows the post-compensation techniques. Table.3 shows the symmetrical-compensation.
Dispersio n at a Fiber of
100km
Dispersion at a DCF of
20km
Pre-compensation
Q-factor BER
16
-70 24.24 1e-40
-80 27.29 1e-40
-90 24.53 1e-40
18
-70 22.83 1e-40
-80 24.09 1e-40
-90 26.04 1e-40
20
-70 20.33 1.40e-25
-80 22.73 1e-40
-90 25.39 1e-40
22
-70 18.60 2.22e-17
-80 19.73 1.13e-21
-90 22.66 1.6e-40
Table.1performance of pre-compensation
From this table.1 shows the Q-factor and BER values in the range of positive dispersion values varies from 16 to 22 and the negative dispersion values varies from -70 to -90. From this range positive dispersion value 16 and the negative dispersion value -80 gives the better Q-factor and BER corresponding eye diagram is shown below.
Fig.6 eye diagram for pre-compensation
Dispersion at a Fiber of
100km
Dispersion at a DCF of
20km
Post-compensation
Q-factor BER
16
-70 24.53 1e-40
-80 27.25 1e-40
-90 24.70 1e-40
18
-70 22.39 5.1e-39
-80 23.50 1e-40
-90 27.10 1e-40
20
-70 20.05 8.8e-24
-80 22.63 1.3e-40
-90 24.52 1e-40
22
-70 17.65 1.21e-14
-80 20.08 5.38e-24
-90 22.41 5.78e-39
Table.2 performance of Post-compensation
From this table.2 positive dispersion value 18 and the negative dispersion value -90 gives the better Q-factor and BER corresponding eye diagram is shown below.
Dispersion at a Fiber of
100km
Dispersion at a DCF of
20km
Symmetrical-compensation
Q-factor BER
16
-70 24.75 1e-40
-80 26.67 1e-40
-90 25.05 1e-40
18
-70 22.85 1e-40
-80 24.31 1e-40
-90 27.28 1e-40
20
-70 19.88 2.8e-24
-80 23.12 1e-40
-90 24.91 1e-40
22
-70 18.81 1.37e-18
-80 20.08 9.70e-24
-90 22.63 1e-40
Table.3 performance of Symmetrical-compensation
From this table.3 positive dispersion value 18 and the negative dispersion value -90 gives the better Q-factor and BER corresponding eye diagram is shown below.
Fig.8 eye diagram for symmetrical-compensation
The better Q-factor and BER obtained in symmetrical compensation approach in the range of 18, -90. So, we chose the in this range and shows the three approach Q-factor values in graphically.
In these range three compensation techniques having the same minimum bit error rate is 1e-40.
VII. CONCLUSION
Dispersion compensation with dispersion compensating fiber at 10Gbps for 100km single mode fiber and 20km dispersion compensating fiber has been analyzed. In this analysis three approaches of dispersion compensation with dispersion compensating fiber are proposed in this paper. Found this analysis symmetrical-compensation is better than other two approaches. Also concluded that positive dispersion value is 18 in a single mode fiber and negative dispersion value is -90 in a dispersion compensating fiber will provide the better compensation at 10Gbps.
VIII. REFERENCES
[1] Anil Kumar and Mahipal Singh “A fabrication study on DCF compensated SMF using OptSim simulation software” IJARCCE Aug 2015.
[2] Manpreet Kaur, Himali Sarangal, Parveen Bagga “Dispersion compensation with dispersion compensating fibers (DCF)” IJARCCE Feb 2015.
[3] Manpreet Kaur, Himali Sarangal, “Analysis on Dispersion compensation with dispersion compensating fibers (DCF)” International Journal of Electronics and Communication Engineering (SSRG-IJECE)-Volume 2 issue 2 Feb 2015.
[4] Ranjith Rout, Subhrajith Pradhan, Srikanth Patnaik “Role of dispersion compensating fiber technique for enhancing optical fiber communication system utility” international research journal of engineering and technology since ISSN:2395-0056 volume: 02 Issue: 07, Oct 2015.
[5] Gurpreet Kaur, Navdeep Kaur, Use of Dispersion Compensating Fiber in Optical Transmission Network for NRZ Modulation Format, International Journal Of Engineering And Computer Science ISSN: 2319-7242 Volume 3 Issue 5, May 2014.
[6] Ajeet Singh Verma, A. K. Jaiswal, Mukesh Kumar, An Improved Methodology for Dispersion Compensation and Synchronization in Optical Fiber Communication Networks, International Journal of Emerging Technology and Advanced Engineering, ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 5.
