Improvement of the Performance of Advanced Local Area Optical Communication Networks by Reduction the Effects of the Propagation Problems

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Improvement of the Performance of Advanced Local Area Optical Communication Networks by Reduction the Effects of the Propagation Problems Powered By Docstoc
					                                                       (IJCSIS) International Journal of Computer Science and Information Security,
                                                       Vol. 8, No. 4, July 2010




                 Improvement of the Performance of Advanced Local Area
                Optical Communication Networks by Reduction the Effects
                                          of the Propagation Problems
                                                                                *
               Mahmoud I. Abd-Alla                                                  Fatma M. Aref M. Houssien
           Electronics & Communication Department, Faculty of Engineering, Zagazig University, EGYPT
                            Email: mabdalla@gmail.com, *E-mail: fatma_shahin2010@yahoo.com


Abstract
In the present paper, the improvement of transmission distance           when the light traveling down a fiber optic cable
and bit rates of Advanced Local Area Optical Communication               “spreads out,” becomes longer in wavelength and
Networks (ALAOCN) are investigated by reducing the effects               eventually dissipates. Attenuation, a reduction in the
of propagation problems over wide range of the affecting
                                                                         transmitted power, has long been a problem for the fiber
parameters. Dispersion characteristics in high-speed optical
transmission systems are deeply analyzed over a span of
                                                                         optics community. However, researchers have
optical wavelengths from 1.2 μm up to 1.65 μm. Two different             established three main sources of this loss: absorption,
fiber structures for dispersion management are investigated.             scattering, and dispersion [2, 3]. Fiber to the Home
Two types of fabrication material link of single mode fiber              (FTTH) technology is one of the main research
made of Germania doped Silica and plastic fibers are                     objectives of the lasts years in optical fiber
suggested. Two successive segments of single mode fiber                  communication. The increasing development of data
made of Germania doped Silica are suggested to be employed               communications and the emerging of applications
periodically in the long-haul systems. The two successive                demand a redesign of the access networks in order to
segments are: i) of different chemical structures (x), or ii) of         accomplish new bandwidth and latency requirements.
different relative refractive index differences (Δn). As well as         Wireless communications are a good alternative for
the total spectral losses of both fabrication materials and total
insertion losses of connectors and splices of these fabrication
                                                                         quick deployments and low cost implementations but
materials are presented under the thermal effect of to be                this technology cannot compete against optical
processed to handle both transmission lengths and bit rates per          communications in terms of available bandwidth,
channel for cables of multi links over wide range of the                 latency and robustness. Since 1980, several techniques
affecting parameters. Within soliton and maximum time                    have been proposed and applied to reduce such
division multiplexing (MTDM) transmission techniques, both               phenomenon which severely reduces the transmitted bit-
the transmission bit rate and capacity-distance product per              rate [4, 5]. The rapid increase of transmission capacity
channels for both of silica doped and plastic fabrication                need is requiring higher speed optical communication
materials are estimated. The bit rates are studied within                system. However, the upgrade of most installed system
thermal sensitivity effects, loss and dispersion sensitivity
effects of the refractive index of the fabrication core materials
                                                                         at third window to multi-Giga-bit rate is limited by the
are taken into account to present the effects on the                     high linear chromatic dispersion of the optical standard
performance of optical fiber cable links. Dispersion                     fiber deployed worldwide [6, 7]. To upgrade existing
characteristics and dispersion management are deeply studied             networks based on standard single-mode 1310 nm
where two types of optical fiber cable core materials are used.          optimized optical fibers, several all-optical dispersion
A chromatic dispersion management technique in optical                   compensation techniques have been proposed [6].Recent
single mode fiber is introduced which is suitable for                    progress in optical fiber amplifier technology makes
(ALAOCN) to facilitate the design of the highest and the best            fiber dispersion the ultimate limiting factor for high-
transmission performance of bit rates in optical networks.               speed long-distance optical fiber transmission. Low-
Keywords: Propagation problems, Single mode fiber (SMF),                 chirp, high-speed optical sources are indispensable for
Fiber losses, Dispersion types, Dispersion management,                   long-haul     multi    Giga     bit-per-second      optical
Soliton Bit rate thermal sensitivity, optical link design,               communication systems [7].Traffic demand has been
Thermal effects, Advanced-optical networks.                              increasing steadily in the last few years. In order to
                                                                         support this increasing traffic demand the optical links
1. Introduction                                                          between the main cities, which are typically terrestrial
                                                                         links with hundreds of kilometers operating at 10
        Fiber optic transmission and communication
                                                                         Gbit/sec per channel, have to be upgraded. A solution
are technologies that are constantly growing and
                                                                         for the upgrading of these links is to increase the bit rate
becoming more modernized and increasingly being used
                                                                         per channel to 40, 80 or even to 160 Gbit/s. Access
in the modern day industries [1]. Dispersion occurs
                                                                         optical networks are capable of solving those



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                                                                                                      ISSN 1947-5500
                                                   (IJCSIS) International Journal of Computer Science and Information Security,
                                                   Vol. 8, No. 4, July 2010




requirements for present and future applications. The               α S ≡ Rayleigh scattering
                                                                                                     ⎛ 0 . 75 + 66 Δ n ⎞ ⎛ T
                                                                                                    =⎜                 ⎟ ⎜
                                                                                                                               ⎞
                                                                                                                               ⎟    dB/km             (3)
                                                                                                     ⎜                 ⎟ ⎜T    ⎟
recent explosive growth of the internet has triggered the                                            ⎝        λ4       ⎠ ⎝ 0   ⎠
introduction of broadband access network based on                   Where we have assumed that the scattering loss is
FTTH. To deal with various demands [6], access and                  linearity is related to the ambient temperature (Τ) and
metro networks require scalability in terms of capacity             (T0) is a reference temperature (300 °K), (Δn) and (λ)
and accommodation and flexibility with regard to                    are the relative refractive index difference and optical
physical topology [7]. Therefore, new specific                      signal wavelength respectively. The absorption losses (α
components are required. The advanced high speed                    UV: Ultra-violet losses) and (α IR: Infra-red losses) are
technology of core networks is expected to provide cost             given as in reference [14]:
effective migration of the component solutions towards                       αUV = 1.1×10−4 ω ge 0 0 e 4.9λ dB/km        (4)
access applications; however, improvements in terms of                                                        2
                                                                                   ⎛               − 24 ⎞
the integration of functions and low cost packaging have                     α IR = ⎜ 7 × 10−5 e         λ⎟         dB/km                         (5)
                                                                                    ⎜                     ⎟
                                                                                   ⎝                      ⎠
to be made. Dense wavelength division multiplexing
(DWDM) is widely becoming accepted as a technology                  Where (ωge %) is the weight percentage of Germania,
for meeting growing bandwidth, and WDM systems                      GeO2 added to optical silica fibers to improve its optical
beginning      to     be     deployed       in    undersea          transmission characteristics.
telecommunications links [8, 9].                                    2.1.2. Plastic fibers attenuation model
          As complexity of optical dense wavelength                      Plastics PMMA Polymethyl Methacrylate, as all
division multiplexing (DWDM) networks increases due                 any organic materials, absorb light in the ultraviolet
to the large number of channels involved, managing the              spectrum region. The mechanism for the absorption
large spectral variations in the dispersion and gain                depends on the electronic transitions between energy
becomes more difficult as the desired spectral bandwidth            levels in molecular bonds of the material. Generally the
increases. Dispersion managed soliton, now being                    electronic transition absorption peaks appear at
developed by a number of different groups, can resolve              wavelengths in the ultraviolet region, and their
the technical problems that in the past have prevented              absorption tails have an influence on the plastic optical
the use of the soliton transmission format in optical fiber         fiber (POF) transmission loss [15]. According to
communication systems [10-12]. Optical solitons are                 urbach’s rule, the attenuation coefficient αe due to
stable nonlinear pulses formed in optical fibers when the           electronic transitions in POF is given by the following
nonlinearity induced by the optical intensity is sufficient         expression [15]:
                                                                              α e (PMMA) = 1.10 × 10 − 5 exp⎜ ⎟ dB/km (6)
                                                                                                            ⎛8⎞
to balance the dispersion of the fiber. In an ideal lossless                                                ⎜ ⎟
                                                                                                                   ⎝λ⎠
fiber, solitons would not distort in either the time or
                                                                    Where: (λ) is the optical signal wavelength of light in
frequency domains, regardless of the distance over
                                                                    (μm). In addition, there is another type of intrinsic loss,
which they propagated. A dispersion managed fiber is
                                                                    caused by fluctuations in the density, and composition
made by alternating sections of positive and negative
                                                                    of the material, which is known as Rayleigh scattering.
dispersion fiber to create a transmission line with high
                                                                    This phenomenon gives the rise to scattering coefficient
local dispersion and low total dispersion [13].
                                                                    (αR) that is inversely proportional to the fourth power of
2. Modeling Basics and Analysis                                     the wavelength, i.e., the shorter is (λ) the higher the
      Special emphasis is given to the propagation                  losses are. For POF, it is shown that (αR) is [16]:
problems in silica-doped and plastic fibers as promise                                        ⎛ 0.633 ⎞
                                                                              α R (PMMA) = 13 ⎜       ⎟
                                                                                                        4
                                                                                                          dB/km    (7)
                                                                                                ⎝    λ    ⎠
links in long and short–distance advanced optical                   Then the total losses of plastic optical fibers are given:
communication networks. Silica-doped and plastic fibers                                                                                   4
                                                                                                                   ⎛8⎞       ⎛ 0 .633 ⎞
characteristics (spectral loss and chromatic dispersion)            α total (PMMA ) = 1 .10 × 10 − 5 exp ⎜            ⎟ + 13 ⎜        ⎟       dB/km
are thermal dependent, thus, these two variables must be                                                           ⎝ λ⎠      ⎝ λ ⎠
taken into account when studying the transmission                                                                                         (8)
capacity of the fibers. The processed propagation
                                                                    2.1.3. Connector and splice attenuation model
problems in this study will deeply defined, analyzed,
                                                                          There are many types of connectors developed for
investigated parametrically and treated over wide range
                                                                    fiber cable. A connector is used to join a fiber cable to a
of the affecting parameters.
                                                                    transmitter or receiver, or is used to join together strands
2.1. Simplified attenuation model                                   of fiber. A connector for fiber is similar in concept to a
2.1.1. Silica-doped fibers attenuation model                        traditional electrical connector, but the fiber connector is
   Based on the models are given in reference [14], the             actually more delicate, as it must precisely align the
   spectral losses of silica-doped fibers are cast as:              internal fibers to insure a proper flow of data through the
   α = α I + α S + α UV + α IR dB/km                   (1)          cables. Before connecting one fiber with the other fiber
Where α I ≡ the intrinsic loss ≅ 0.003 dB/km, and      (2)          in the fiber optic communication link, one must decide
                                                                    whether the joint should be permanent or demountable.



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                                                                                                                  ISSN 1947-5500
                                                                    (IJCSIS) International Journal of Computer Science and Information Security,
                                                                    Vol. 8, No. 4, July 2010




Based on this, two types of joints are presented. A                                pulse spreading) arises from the use of sources with a
permanent joint is done by splice and a demountable                                finite spectral spread, since signals impressed on a fiber
joint is done by connector. The insertion loss of any                              at different wavelengths will have different group
connector can be expressed as given by [17]:                                       velocities. The transit time τ(λ) of a mode at a
                                       ⎛ P ⎞ dB/km (9)                             wavelength (λ) may be related to that at the mean source
          IL( Insertion Loss) = 10 log ⎜ i ⎟
                                      ⎜P ⎟
                                      ⎝ t⎠
                                                                                   wavelength (λo) by expanding as a Taylor series about
Where (Pi) is the incident power in (mWatt) and (Pt) is                            (λo) as given in [19-21]:
the transmitted power in (mwatt). For single mode fibers
(SMF), the Fresnel reflection loss caused by the                                                                      dτ     1            d 2τ
                                                                                       τ (λ ) = τ (λo ) + (λ − λo )         + (λ − λo ) 2
differences between the refractive indices of the silica-                                                             dλ λ   2            dλ2 λ
                                                                                                                          o                    o
doped, (n=n1) and plastic fibers, (n=n2) and the material
separation are given as the following [18]:                                            1            d 3τ
                                                                                   +     (λ − λo )3                                                      (23)
                           ⎛ 4n n          ⎞                                           6            dλ3    λo
            Loss = 20 log ⎜      1 clad ⎟ dB/km                  (10)
                           ⎝ 1 clad ) ⎠
                           ⎜ (n + n     2⎟
                                                                                                dτ     1        d 2τ     1       d 3τ
                         ⎛ 4n n          ⎞                                         Δτ = Δλ            + (Δλ ) 2         + (Δλ )3                         (24)
           Loss = 20 log ⎜      2 clad ⎟ dB/km                   (11)                           dλ λ   2        dλ2      6       dλ3
                         ⎜ (n + n     )2 ⎟                                                          o                λo               λo
                         ⎝ 2 clad ⎠
                                                                                                            Lm
Where (n1) is the refractive-index of silica-doped core                            Noting that: τ =                                                      (25)
                                                                                                            C
material, and (n2) is the refractive-index of plastic core
material. The cladding refractive-index can be expressed                           Where (L), (C), and (m) are the fiber length, the velocity
as a function of both silica-doped and plastic core                                of light in vacuum, and the group index for the mode
refractive-indices               and          relative     refractive-index        respectively, (m) is given by assuming good
                                                                                                                                      dn1
difference as the following:                                                       confinement in [20]:               m = n1 − λ                         (26)
                                                                                                                                      dλ
             nclad = (1 − Δn ) n1                              (12)
                                                                                   We can deduce that
             nclad = (1 − Δn ) n2                              (13)
                                                                                                      L   ⎡       dn1 ⎤
Then by substituting with equations (12, 13) into                                                τ=       ⎢n1 − λ dλ ⎥                                   (27)
                                                                                                      C   ⎣           ⎦
equations (10, 11), we can obtain:                                                 The use of Eq. (27) into Eq. (24) yields per unit length:
                                     ⎛ 4 (1 − Δn ) n 2 ⎞
     Loss (silica − doped ) = 20 log ⎜              1 ⎟ dB/km    (14)                                                                        ⎡ d 3n           ⎤
                                    ⎜ (2 n − Δn ⋅ n )2 ⎟                                                  Δλ d 2 n1                (Δλ ) 2   ⎢λ
                                                                                                                                                        2
                                                                                                                                                   1 + d n1   ⎥
                                    ⎝ 1            1 ⎠                                            Δτ =      .λ                 −
                                    ⎛ 4 (1 − Δn ) n 2 ⎞
                                                                                                          C    dλ2                  2C       ⎢ dλ3
                                                                                                                                             ⎣         dλ2    ⎥
                                                                                                                                                              ⎦ λo
                                                           dB/km (15)                                                     λo
          Loss ( plastic ) = 20 log ⎜              2 ⎟
                                    ⎜ (2 n − Δn ⋅ n )2 ⎟
                                    ⎝     2        2 ⎠

2.2. Simplified dispersion model analysis                                              (Δλ )3 ⎡ d 4 n1
                                                                                              ⎢λ          d 3n1       ⎤
                                                                                                                      ⎥                                  (28)
                                                                                   −                   +2
2.2.1. Silica-doped fiber dispersion model                                              6C ⎢ dλ     4
                                                                                                          dλ3         ⎥
                                                                                              ⎣                       ⎦ λo
     We have employed Germania-doped Silica fiber as
a communication channel, where (x) is the mole fraction                            Where higher-order dispersion modes are considered,
of Germania added to silica material. The refractive                               following the same spirit of Refs. [20, 21], in separating
index of silica-doped material may be evaluated                                    the various contributions to the total chromatic
following the three terms Sellmeier equation [19]:                                 dispersion in single mode fibers of radius (a), we have:

             2          3    Ai λ2                                                          (Δτch/Δλ.L) = Dt = total chromatic dispersion
            n1 = 1 + ∑                                           (16)
                             2
                       i =1 λ − λi 2                                               coefficient= (Mmd + Mwd + Mpd),             (29)
                                                                                   Where: Mmd = material dispersion coefficient
Where (n1), (λ), (Ai), and (λi) are the core refractive
                                                                                                                      ⎡                          ⎤
index, the oscillator strength and the oscillator wave                                          λ d 2 n1      Δλ ⎢ d 3n1 d 2 n1 ⎥
                                                                                            =               +      λ    +
length respectively. For GeO2-SiO2 fibers of x % GeO2                                           C dλ2         2C ⎢ dλ3    dλ2 λ ⎥
                                                                                                                                 ⎥
                                                                                                         λo      ⎢
                                                                                                                 ⎣              o⎦
(mole), the two sets (Ai) and (λi) are given [19]:
          A1 = (0.6961663 + 0.11070010 x) fT 1 ,  (17)                                         ⎡                   ⎤
                                                                                       (Δλ ) 2 ⎢ d 4 n1    d 3n1 ⎥
          A2 = (0.4079426 + 0.31021588 x) f T 1 , (18)                             −             λ      +2                                               (30)
                                                                                        6C ⎢ dλ4           dλ3
                                                                                                                   ⎥
                                                                                               ⎢
                                                                                               ⎣                λo ⎥
                                                                                                                   ⎦
          A3 = (0.8974794 − 0.04331091x) f T 1 ,  (19)
                                                                                             Mwd = waveguide dispersion coefficient
          λ1 = (0.0684043 + 0.00568306 x) f T 2 , (20)                                                            2
          λ 2 = (0.1162414 + 0.03772465x) f T 2 , (21)                                             n Δn ⎛ m ⎞
                                                                                                  = 1.  ⎜ ⎟ M (V )                                       (31)
                                                                                                    C λ ⎜ n1 ⎟
                                                                                                        ⎝ ⎠
         And λ3 = (9.896161 + 1.94577 x) f T 2 .  (22)
Where fT1=0.93721+2.0857x10-4T, fT2=T0/T, (T0) is a                                          Mpd = profile dispersion coefficient
reference temperature and T is the medium (fiber                                                   n Δn \   ⎛ λ Δn \ m ⎞
                                                                                                  = 1       ⎜       − ⎟ M (V )                           (32)
temperature) [19-21]. Chromatic dispersion (a cause of                                               C      ⎜ 4 Δn n1 ⎟
                                                                                                            ⎝          ⎠




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                   (n1 − nclad )                                                                                                                      1
           Δn =                                                             (33)                                 ⎛ ⎛ N Δn ⎞2 ⎛ α − 2 − ε ⎞ 2 2α ⎞
                                                                                                                                                          2
                        n1                                                                                   P = ⎜⎜ 1 ⎟ ⎜                ⎟ ×    ⎟             (46)
                                                                                                                 ⎜ ⎝ cλ ⎠ ⎝ α + 2 ⎠ 3α + 2 ⎟
               \dΔn                                                                                              ⎝                              ⎠
           Δn =                                                             (34)
                dλ                                                                                 Where the group index for the mode is given by:
                                                                                                                           dn2
           V = 2π             2
                     a n12 − nclad / λ              , and                   (35)                             N1 = n2 − λ                                      (47)
                                                                                                                           dλ
                                                                 2                                 Where: (Δτ) is the total pulse spreading due to chromatic
           M (V ) = 0.08 + 0.549(2.834 − V )                                (36)
                                                                                                   dispersion in nsec, (Wmd) is the material dispersion
Equation (30), in our suggested basic model, accounts                                              coefficient in nsec/nm.km, (P) is the profile dispersion
for the material dispersion (the first, the second, and the                                        coefficient in nsec/nm.km, and (Δn) is the relative
third -order dispersion effects simultaneously). Then the                                          refractive index difference defined as:
use of Eq. (16) yields:
                                                                                                                   n2 − ncladding
                                                                                                                    2    2
                                                                                                                                                              (48)
                             2
                    3 − Ai λi λ                                                                             Δn =
           n1n1\ = ∑                                                        (37)                                          2
                                                                                                                       2 n2
                           (
                  i =1 λ2 − λ2 2
                             i          )                                                          Where (n2) is the cable core refractive index, (ncladding) is
                                    3 A λ2 (3λ3 + λi )
                                                     2                                             the core cladding refractive index, and (C1) is a constant
             n1n1\ \ + n1\ 2 = ∑ i i                    , and (38)
                                  i =1      (
                                          λ2 − λi2 3
                                                         )                                         and is given by the following expression:
                                                                                                                  α − 2−ε
                                                                                                             C1 =                                (49)
                                              2         2
                                  3 − 12 Ai λi λ (λ2 + λi )
     n1n1\ \ \ + 3n1\ n1\ \ = ∑                                    (39)                                             α +2
                                i =1            (
                                           λ2 − λi2 4
                                                             )                                     Where (α) is the index exponent, (ε) is the profile
                                        2               2             2       2
                                              3 12 AiT λiT (5λ4 + 10λiT λ2 + λiT )
                                                                                                   dispersion parameter, and is given by the following:
     n1n1\ \ \ \ + 4n1\ n1\ \ \ + 3n1\ \ = ∑                                                                       2 n λ dΔn
                                            i =1             λ2 − λiT
                                                                    2
                                                                      (
                                                                      5
                                                                               )                             ε =− 2
                                                                                                                   N1 Δn dλ
                                                                                                                                                 (50)
                                                                            (40)

2.2.2. Plastic fiber dispersion model                                                              3.   Transmission Techniques for                           Reducing
     The plastic cable core material which the                                                              Propagation Problems
investigation of the spectral variations of the refractive-                                                 The need of communication is an all time need
index (n2) requires Sellemeier equation given in [22]:                                             of human beings. For communication some channel is
                                                                                                   needed. Fiber is one channel among many other
            2          3    Bi λ2
           n2 = 1 + ∑                                                       (41)                   channels for communication. The dispersion
                            2
                      i =1 λ − λi 2
                                                                                                   phenomenon is a problem for high bit rate and long haul
     For the plastic fiber material, the coefficients of the                                       optical communication systems. An easy solution of this
Sellmeier equation and refractive-index variation with                                             problem is optical solitons pulses that preserve their
ambient temperature are [22]: B1= 0.4963, λ1= 0.6965                                               shape over long distances. Soliton based optical
(T/T0), B2= 0.3223, λ2= 0.718 (T/T0), B3= 0.1174, and                                              communication systems can be used over distances of
λ3= 9.237. Then the first and second differentiation of                                            several thousands of kilometers with huge information
Eq. (41) with respect to (λ) yields:                                                               carrying capacity by using optical amplifiers. Soliton
                                      2                                                            communication systems are a leading candidate for
                      3         − Bi λi λ
           n2 n2 \ = ∑                                                        (42)                 long-haul light wave transmission links because they
                     i =1      (λ2 − λi2 )2                                                        offer the possibility of dynamic balance between group
                                  3 Bi λi (3λ3 + λi )
                                        2         2                                                velocity dispersion (GVD) and self-phase modulation
       n2 n2 \ \ + n2 \ 2 = ∑                                                (43)
                                i =1   (λ2 − λi23
                                                     )                                             (SPM), the two effects that severely limit the
                                                                                                   performance of non soliton systems. Most system
The total chromatic dispersion ( Dt ) of the output pulse                                          experiments employ the technique of lumped
width in single mode fibers of (POF) is given by [22]:                                             amplification and place fiber amplifiers periodically
           Δτ                                                                                      along the transmission line for compensating the fiber
   Dt =          = ( W md + P ) nsec/nm.km (44)                                                    loss. However, lumped amplification introduces large
         Δλ ⋅ L
                                                                                                   peak-power variations, which limit the amplifier spacing
The output pulse width from single mode plastic optical                                            to a fraction of the dispersion length. Soliton
fiber (POF) was taken into account both material and                                               propagation is employed where the controlling
profile dispersions, and thus modal dispersion is equal to                                         parameters lead to a balance between the pulse
zero for single mode fibers [23]:                                                                  spreading due to dispersion and the pulse shrinking due
                                                                                        1
                 ⎛ λ3 dn  2λ ⎛ d 2 n2                            ⎞                      ⎞ 2        to nonlinearity. The balance between the non-linearity
           Wmd = ⎜ −    2    ⎜                                   ⎟ (N Δn ) × C ⎛ 2α ⎞ ⎟
                 ⎜ c dλ − c ⎜
                 ⎜                 2                             ⎟   1        1⎜       ⎟⎟
                                                                               ⎝ α + 2 ⎠⎟
                                                                                                   effects from one side and the dispersion effects from the
                 ⎝           ⎝ dλ                                ⎠                      ⎠          other side creates a solitary wave [24]. The dispersion of
                                                                            (45)                   a medium (in the absence of non-linearity) makes the



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                                                                                                                                    ISSN 1947-5500
                                                                                                               (IJCSIS) International Journal of Computer Science and Information Security,
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various frequency components propagate at different                                                                          Where: (nnl) is the nonlinear Kerr coefficient in m2/watt,
velocities; while the non-linearity (in the absence of                                                                             (Aeff) is the effective area in µm2/Watt,
dispersion) causes the pulse energy to be continually                                                                              (Pso) is the optical signal power in Watt,
injected, via harmonic generation, into higher frequency                                                                           (λs) is the optical signal wavelength in µm,
modes. That is to say, the dispersion effect results in                                                                      and (Dt) is the total chromatic dispersion coefficient in
broadening the pulse while the non-linearity tends to                                                                        nsec/nm.km. Ref. [27] derived the condition for MTDM
sharpen it. Analysis given in references [25, 26], the                                                                       where the bit rate Brm is given by:
soliton bit rate per channel (Brs) is given by:                                                                                              0.25
                                                                                                                                     Brm =           Gbit / sec                                (52)
                  −            − λ      Aeff 3.2 x10 −20                                                                                     τ min
                 Brs2 = 59.7 Pso1( s )(     )(           ) Dt x106 (51)
                                         1.54              20               nnl
Where: (τmin) is the minimum pulse broadening in nsec.                                                                           B
                                                                                                                               S Drm =
                                                                                                                                          D dBrm
                                                                                                                                            .    .       =       .
                                                                                                                                                                       2
                                                                                                                                                                               (
                                                                                                                                                                               2 2 3     4 3 3 2
                                                                                                                                                              D 14.7 λs Aeff B1 A1 λs + T B2 A1 λs   )2
The spectral and thermal sensitivities are the guide of                                                                                  Brm dD              Brm
                                                                                                                                                                           (
                                                                                                                                                                   nnl Pso T B1 A2 λs − A2 B1 λ4
                                                                                                                                                                             2    3 2     2 4
                                                                                                                                                                                                )3

the measurement the relative variations of the outputs
                                                                                                                                                                                               s


and the relative variations of the inputs. The soliton and                                                                                                                                     (58)
MTDM bit rate within thermal, loss, dispersion                                                                                   Using the series of the set of equations analysis
sensitivity coefficients, and parameters as ( ST ),   Brs
                                                                                                                             from Eq. (1) to Eq. (59), the transmission bit rates per
( Sα ), ( S D ), ( ST ), ( Sα ), and ( S D ) are taken
   Brs      Brs     Brm     Brm           Brm                                                                                channel for both silica-doped and plastic materials are
                                                                                                                             investigated under wide optical ranges which give the
into account as criteria of a complete comparison
                                                                                                                             minimum values of both total losses and total
between silica doped and plastic materials and are given:
                                                                                                                             dispersion. The calculations are based on the values:
             T dBrs    T    A1 B1 3λ3 B1 + Dt λ1
                              2        2
                                         (     2
                                                                )                                        (53)
                                                                                                                             Central optical signal wavelength (λ0) is selected to be
                                (                                       )
   B
  ST rs =      .    =    .
            Brs dT    Brs λ3 − A2 B 2 + Dt2λ2 A2 B 3
                                                                                                                             (1.2 μm ≤ λ0 ≤ 1.65μm), relative refractive index
                                1 2               2



    B
  Sα rs =
             α
                  .
                      dBrs
                           =
                             α 0.633 B1 α t 2λs A1B3 T + λs A2 B1 T
                                 .
                                      2       2
                                                   (
                                                   2 2     4 3 4 3
                                                                                                     )
                                                                                                     2
                                                                                                         (54)                difference for silica-doped material (Δn) is chosen to be
            Brs        dα    Brs           2
                                              (  3    3 2 33
                                         A1 λs T + α t B2 λs                 )                                               ( 0.006 ≤ Δn ≤ 0.008 ), source spectral line width (Δλ) is
                                                                                                                             selected to be (0.1 nm ≤ Δλ ≤ 0.5 nm), GeO2 mole
    B
  S Drs =
             D dBrs
               .    =     .
                                2      2 2 3 3
                                                   (3 3 2
                       D 14.7 λs Aeff A1 B1 T λs + A2 B1 λs                              )
                                                                                         3
                                                                                                         (55)                fraction (x) is chosen to be ( 0.0 ≤ x ≤ 0.2 ), relative
            Brs dD    Brs               3 2
                                              (2 2 4 42
                            nnl Pso A1B2 λs − T B2 A1 λs                         )                                           refractive index difference for plastic material (Δn) is
                                                                                                                             determined where ( 0.05 ≤ Δn ≤ 0.07 ), and fiber
    B
  ST rm =
              T dBrm
                .    =
                             2      2 3     2    3 3
                        T B1 A2 4 λ A1 + Dt λ1 A2 B2
                           .
                                                       (                                     )           (56)                temperature (T) is chosen to be (290°K ≤ T ≤ 330°K).
             Brm dT    Brm    2   2 2
                                         (3 2 4 2
                             λ + B2 A3 − Dt λB2 A2                                   )
    B
   Sα rm =
                  α
                         .
                             dBrm
                                    =
                                        α
                                                         2
                                                                 s  (
                                                  0.633 A1 α t 2λ2 B1 A3 T 5 + λ4 B2 A1
                                                                       2
                                                                                s
                                                                                   3 4                    )2
                              dα              .
                 Brm                    Brm
                                                            (2                2 3
                                                            B1 λs α t5 + T 2 A2 λ3
                                                                                 s               )
                                                                                                         (57)


4. Results and Discussions
         We have analyzed the propagation problems of                                                                        ambient temperature (T0 ), and relative refractive-index
these materials in the interval of 1.2 µm to 1.65 µm                                                                         difference (Δn)}, both the effective performance of
under the set of affecting parameters at temperature                                                                         plastic, and Germania-doped silica fibers are processed
range varies from 290 °K to 330 °K. The following                                                                            based on the transmission bit rate or capacity-distance
numerical sets of data are used to obtain transmission bit                                                                   product per channel: Transmitted bit-rate x transmission
rate and capacity-distance product per channel as                                                                            distance (L) is given by:
follows: (1.2 μm ≤ λ0 ≤ 1.65 μm); (λ0): central optical                                                                              Pr = B r × L , Gbit.km/sec             (59)
signal wavelength, (0.1 nm ≤ Δλ ≤ 0.5 nm); (Δλ):                                                                             The transmitted bit-rate per optical channel is also a
spectral line width of the optical source, effective area;                                                                   special criterion for comparison for different fiber cable
Aefff= 85 µm2, (2 Km ≤ L ≤ 10 Km); (L): transmission                                                                         materials of plastic and silica-doped fibers. Based on the
distance, (0.0 ≤ x ≤ 0.2); (x): percentage of Germania                                                                       clarified variations in figures (1- 20), the facts are
doped in silica fibers, (0.05 ≤ ΔnPMMA ≤ 0.07);                                                                              assured:
(ΔnPMMA): relative refractive-index difference, (0.006 ≤
Δnsilica-doped ≤ 0.008), (Δnsilica-doped): relative refractive-
index difference for silica-doped, (4 mwatt ≤ Ps ≤ 30
mwatt); (Ps): optical signal power. At the set of
affecting parameters {optical signal wavelength ( λs),




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i- Figs. (1, 2) prove that as λ0 increases, the total spectral          T increases, total dispersion coefficient also increases
   losses decrease at constant both T, and Δn for silica-               at constant λ0.
   doped fibers. But as Δn, and T increase, the total                 vi- Figs. (11, 12) indicate that as the Pt increases, the
   spectral losses also increase at constant λ0.                        total insertion loss decreases for both silica-doped and
ii- Figs. (3-4) indicate that as L increases, the                       plastic fibers at constant Δn. As well as Δn increases,
     transmission bit rate per channel decreases for both               the total insertion loss also increases at constant Pt.
     silica-doped and plastic fibers at constant T. As well           vii- Figs. (13, 14) demonstrate that as L increases, the
     as T increases, the transmission bit rate per channel                 transmission bit rate per channel decreases for both
     decreases at the constant L.                                          silica-doped and plastic fibers at constant Δn. But
iii- Figs. (5-6) assure that as T increases, the capacity-                 as Δn increases, the transmission bit rate per
     distance product per channel decreases for both                       channel decreases at constant L.
     silica-doped and plastic fibers at constant L.                   viii- Figs. (15, 16) assure that as Dt increases, the soliton
     Moreover as L increases, the capacity-distance                        and MTDM bit rates decrease for both silica-doped
     product per channel also increases at constant both                   and plastic materials, but with silica-doped presents
     T.                                                                    higher bit rates than plastic materials at minimum
iv- Figs. (7, 8) demonstrate that as λ0 increases, total                   losses.
   dispersion coefficient also increases for both silica-               x- Figs. (17, 18) indicate that as T increases, Soliton
   doped and plastic fibers at the constant Δn. As well as                 bit rate thermal sensitivity also increases at constant
   Δn increases, total dispersion coefficient also                         Dt, but with increasing Dt, we have observed that
   increases at constant λ0.                                               soliton bit rate thermal sensitivity deceases at
v- Figs. (9, 10) prove that as λ0 increases, total                         constant T for both silica-doped and plastic
   dispersion coefficient also increases for both silica-                  materials.
   doped and plastic fibers at the constant T. As well as



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xi- Figs. (19, 20) prove that as T increases, MTDM bit              technique and offers the best conditions for the
     rate thermal sensitivity also increases at constant Dt,        performance of transmission bit rates and capacity-
     but with increasing Dt, we have observed that                  distance products of silica-doped and plastic materials
     MTDM bit rate thermal sensitivity increases at                 for different transmission distances in advanced local
     constant T for both silica-doped and plastic                   area optical communication networks for suitable
     materials.                                                     operating conditions as shown in Table 1.
      Therefore we can summarize reduction of the
propagation problems within soliton transmission

    Table 1: Transmission bit rates and capacity-distance product for both silica-doped and plastic core materials.

                                                           Fiber cable core materials
                                   Silica-doped material                                   Plastic material
                               Best conditions of operation                         Best conditions of operation

       Transmission            at Δn = 0.006 and T = 290 ºK                          at Δn = 0.05 and T = 290 ºK

        Distance                                  Capacity-distance                                      Capacity-distance
                          Transmission bit         product/channel             Transmission bit           product/channel
                       rate/channel (Gbit/sec)      (Gbit.km/sec)           rate/channel (Gbit/sec)        (Gbit.km/sec)

        L = 2 Km              8 Gbit/sec            30 Gbit.km/sec                0.5 Gbit/sec                1.5 Gbit.km/sec

        L = 5 Km              5 Gbit/sec            45 Gbit.km/sec                0.3 Gbit/sec                2 Gbit.km/sec


        L = 8 Km              2 Gbit/sec            60 Gbit.km/sec                0.1 Gbit/sec                2.5 Gbit.km/sec


5. Conclusions                                                      fibers will be increased. Therefore we can say that the
      The characteristics of both of silica doped and               lowest total dispersion and total losses of silica-doped
plastic fibers are investigated under the different                 fibers make these fibers as the best candidate media for
affecting parameters. soliton and MTDM high                         long haul optical transmission in advanced optical
transmission techniques are employed for reducing the               communication networks.
propagation problems as limiting factors such as total
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