Mesuarement of the attenuatuion of the optical fiber ieee format

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Mesuarement of the attenuatuion of the optical fiber ieee format

  1. 1. Measurement of Attenuation of the Optical Fiber ‘Abdulrahman Suratman1, Ong Sin Yee2, Nurul Shafikah Mohd Zain3, Mohamud Mire4 Radar Communication Laboratory, Faculty of Electrical Engineering Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia 1abdurrahman3@live.utm.my 2ongsinyee@hotmail.com 3nshafikah91@yahoo.com 3mohamudmire@yahoo.com Abstract— Attenuation varies depending on the fiber type and the operating wavelength. There are several causes of optical loss that will be investigate through this experiment. There are including the length of the optical fiber, the losses between the gap and the bending of the fiber. Using presenting method, in which Module KL-95001 is used to run several test on the fiber optic. Also, this method can be easily applied to measure the attenuation and investigate the characteristic of the fiber optic. Keywords— Characteristic optical fiber, attenuation factor of optical fiber, attenuation of length, gap and bending of optical fiber. I. INTRODUCTION The use and demand for optical fiber has grown tremendously and optical-fiber applications are numerous. These involve the transmission of voice, data, or video over distances of less than a meter to hundreds of kilometers, using one of a few standard fiber designs in one of several cable designs. A fiber-optic cable is composed of two concentric layers, called the core and the cladding. The core and cladding have different refractive indices, with the core having a refractive index of n1, and the cladding having a refractive index of n2. The index of refraction is a way of measuring the speed of light in a material. Light travels fastest in a vacuum. The actual speed of light in a vacuum is 300,000 kilometers per second, or 186,000 miles per second. Attenuation is the reduction or loss of optical power as light travels through an optical fiber. The longer the fiber is and the farther the light has to travel, the more the optical signal is attenuated. Consequently, attenuation is measured and reported in decibels per kilometer (dB/km), also known as the attenuation coefficient or attenuation rate. structure of an optical fiber is shown in Fig. 1. The core is a cylindrical rod of dielectric material. Dielectric material conducts no electricity. Light propagates mainly along the core of the fiber. The core is generally made of glass. The core is described as having a radius and an index of refraction. The core is surrounded by a layer of material called the cladding. Even though light will propagate along the fiber core without the layer of cladding material, the cladding does perform some necessary functions. Fig. 1 Basic structure of an optical fiber The cladding layer is made of a dielectric material with an index of refraction n2. The index of refraction of the cladding material is less than that of the core material. The cladding is generally made of glass or plastic. The cladding performs the following functions: A. Objective  Reduces loss of light from the core into the surrounding 1) To investigate the main characteristics and the factors air causing attenuation in optical fiber system.  Reduces scattering loss at the surface of the core 2) To study the effect of attenuation using different lengths  Protects the fiber from absorbing surface contaminants of optical fiber cable.  Adds mechanical strength 3) To study the effect of attenuation using different bending diameters of optical fiber cable. For extra protection, the cladding is enclosed in an additional layer called the coating or buffer. B. Structure of Optical Fiber The coating or buffer is a layer of material used to protect an The basic structure of an optical fiber consists of three parts; optical fiber from physical damage. The material used for a the core, the cladding, and the coating or buffer. The basic buffer is a type of plastic. The buffer is elastic in nature and
  2. 2. prevents abrasions. The buffer also prevents the optical fiber from scattering losses caused by microbends. Microbends occur when an optical fiber is placed on a rough and distorted surface. C. How Fiber Optics Works Light travels down a fiber-optic cable by bouncing repeatedly off the walls. Each tiny photon (particle of light) bounces down the pipe .guided down the length of an optical fiber. Now you might expect a beam of light, traveling in a clear glass pipe, simply to leak out of the edges. But if light hits glass at a really shallow angle (less than 42 degrees), it reflects back in again as though the glass were really a mirror. This phenomenon is called total internal reflection. It's one of the things that keeps light inside the pipe as shown in Fig. 2. making it suitable for long-distance multichannel television broadcast systems. telephony and 1)Multimode Fiber: Multimode fiber, the first to be manufactured and commercialized, simply refers to the fact that numerous modes or light rays are carried simultaneously through the waveguide. Modes result from the fact that light will only propagate in the fiber core at discrete angles within the cone of acceptance. This fiber type has a much larger core diameter, compared to single-mode fiber, allowing for the larger number of modes, and multimode fiber is easier to couple than single-mode optical fiber. Multimode fiber may be categorized as step-index or graded-index fiber. Multimode Step-index Fiber Fig. 3 shows how the principle of total internal reflection applies to multimode step-index fiber. Because the core’s index of refraction is higher than the cladding’s index of refraction, the light that enters at less than the critical angle is guided along the fiber. Fig. 2 How fiber optics works Fig. 3 Total Internal Reflection in Multimode Step-index fiber The other thing that keeps light in the pipe is the structure of the cable, which is made up of two separate parts. The main part of the cable in the middle is called the core and that's the bit the light travels through. Wrapped around the outside of the core is another layer of glass called the cladding. The cladding's job is to keep the light signals inside the core. It can do this because it is made of a different type of glass to the core. The cladding has a higher refractive index than the core. Light travels slower in the cladding than in the core. Any light that tries to leak into the cladding tends to bend back inside the core. D. Core Characteristics 1) The diameter of the light carrying region of the fiber is the "core diameter." 2) The larger the core, the more rays of light that travel in the core. 3) The larger the core, the more optical power that can be transmitted. 4) The core has a higher index of refraction than the cladding. 5) The difference in the refractive index of the core and the cladding is known as delta E. Types of Optical Fiber There are two basic types of fiber: multimode fiber optic cable and single-mode fiber optic cable. Multimode fiber is best designed for short transmission distances, and is suited for use in LAN systems and video surveillance. Single-mode fiber is best designed for longer transmission distances, Multimode Graded-index Fiber Graded-index refers to the fact that the refractive index of the core gradually decreases farther from the center of the core. The increased refraction in the center of the core slows the speed of some light rays, allowing all the light rays to reach the receiving end at approximately the same time, reducing dispersion. Fig. 4 shows the principle of multimode graded-index fiber. Fig. 4 Multimode Graded-index Fiber 2)Single-mode Fiber: Single-mode fiber allows for a higher capacity to transmit information because it can retain the fidelity of each light pulse over longer distances, and it exhibits no dispersion caused by multiple modes. Single-mode fiber also enjoys lower fiber attenuation than multimode fiber. Thus, more information can be transmitted per unit of time. Like multimode fiber, early single-mode fiber was generally characterized as step-index fiber meaning the refractive index of the fiber core is a step above that of the cladding rather than graduated as it is in graded-index fiber. Modern single-mode fibers have evolved into more complex designs such as matched clad, depressed clad and other exotic structures. Single-mode fiber has disadvantages. The smaller core diameter makes coupling light into the core more difficult. The tolerances for single-mode connectors and splices are also
  3. 3. much more demanding. Single-mode fiber has gone through a continuing evolution for several decades now. Fig. 5 Single-mode Fiber F. Advantages of Fiber Optic 1)Immunity to Electromagnetic Interference: Fiber optic cables are immune to electromagnetic interference. It can also be run in electrically noisy environments without concern as electrical noise will not affect fiber. Electromagnetic Interference is a common type of noise that originates with one of the basic properties of electromagnetism. Magnetic field lines generate an electrical current as they cut across conductors. The flow of electrons in a conductor generates a magnetic field that changes with the current flow. Electromagnetic Interference does occur in coaxial cables, since current does cut across the conductor. Fiber optics are immune to this EMI since signals are transmitted as light instead of current. Thus, they can carry signals through places where EMI would block transmission. 2)Data Security: Magnetic fields and current induction work in two ways. They don't just generate noise in signal carrying conductors; they also let the information on the conductor to be leaked out. Fluctuations in the induced magnetic field outside a conductor carry the same information as the current passing through the conductor. Optical fibers are difficult to tap. As they do not radiate electromagnetic energy, emissions cannot be intercepted. As physically tapping the fiber takes great skill to do undetected, fiber is the most secure medium available for carrying sensitive data. 3)Non Conductive Cables: Fiber optic cables can be made non-conductive by avoiding metal in their design. These kinds of cables are economical and standard for many indoor applications. Outdoor versions are more expensive since they require special strength members, but they can still be valuable in eliminating ground loops and protecting electronic equipment from surge damage. 4)Eliminating Spark Hazards: Because no electricity is passed through optical fibers, there is no fire hazard. In some cases, transmitting signals electrically can be extremely dangerous. Most electric potentials create small sparks. The sparks ordinarily pose no danger, but can be really bad in a chemical plant or oil refinery where the air is contaminated with potentially explosive vapours. One tiny spark can create a big explosion. Potential spark hazards seriously hinder data and communication in such facilities. 5)Ease of Installation: Fiber cables are easier to install since they are smaller and more flexible. They can also run along the same routes as electric cables without picking up excessive noise. Increasing transmission capacity of wire cables generally makes them thicker and more rigid. Such thick cables can be difficult to install in existing buildings where they must go through walls and cable ducts. Fiber optic cables are much thinner and lighter than metal wires. They also occupy less space with cables of the same information capacity. Lighter weight makes fiber easier to install. 6)High Bandwidth over Long Distances: Fiber optic cables have a much greater bandwidth than metal cables. The amount of information that can be transmitted per unit time of fiber over other transmission media is its most significant advantage. Fiber optics have a large capacity to carry high speed signals over longer distances without repeaters than other types of cables. The information carrying capacity increases with frequency. Generally, coaxial cables have a bandwidth parameter of a few MHz/km, where else the fiber optic cable has a bandwidth of 400MHz/km. G. Attenuation Attenuation is the reduction or loss of optical power as light travels through an optical fiber. The longer the fiber is and the farther the light has to travel, the more the optical signal is attenuated. Consequently, attenuation is measured and reported in decibels per kilometre (dB/km), also known as the attenuation coefficient or attenuation rate. Signal attenuation is defined as the ratio of optical input power (Pi) to the optical output power (Po). Optical input power is the power injected into the fiber from an optical source. Optical output power is the power received at the fiber end or optical detector. It can be expressed in dB: The following equation defines signal attenuation as a unit of length: Attenuation varies depending on the fiber type and the operating wavelength. For silica-based optical fibers, singlemode fibers have lower attenuation than multimode fibers. The higher the wavelength, the lower the attenuation. Singlemode fibers usually operate in the 1310 nm or 1550 nm regions, where attenuation is lowest. This makes single-mode fibers the best choice for long distance communications. Multimode fibers operate primarily at 850 nm and sometimes at 1300 nm. Multimode fibers are designed for short distance use; the higher attenuation at 850 nm is offset by the use of more affordable optical sources. H. Causes of Attenuation Fiber attenuation is caused by scattering, absorption and bending. 1)Absorption: Absorption is a major cause of signal loss in an optical fiber. Absorption occurs when impurities, such as metal particles or moisture, are trapped in the glass. These cause attenuation at specific wavelengths by absorbing the light at that wavelength and dissipating it in the form of heat energy. Absorption is defined as the portion of attenuation
  4. 4. resulting from the conversion of optical power into another energy form, such as heat. Imperfections in the atomic structure induce absorption by the presence of missing molecules or oxygen defects. Absorption is also induced by the diffusion of hydrogen molecules into the glass fiber. Since intrinsic and extrinsic material properties are the main cause of absorption, they are discussed further. Intrinsic absorption is caused by basic fiber-material properties. If an optical fiber were absolutely pure, with no imperfections or impurities, then all absorption would be intrinsic. Intrinsic absorption sets the minimal level of absorption. Extrinsic absorption is caused by impurities introduced into the fiber material. Trace metal impurities, such as iron, nickel, and chromium, are introduced into the fiber during fabrication. Extrinsic absorption is caused by the electronic transition of these metal ions from one energy level to another. 2)Scattering: Scattering losses are caused by the interaction of light with density fluctuations within a fiber. Scattering losses is the reflection of small amounts of light in all directions as it travels down the fiber. Some of this light escapes out of the core, while some travels back toward the source. Some scattering is caused by miniscule variations in the composition and density of the optical glass material itself; this represents the theoretical lower limit of attenuation. Additional variations in density and concentration - and therefore, more scattering - are caused by the dopants used in the core glass to change the refractive index of different types of fiber. Fibers with increased dopant concentration exhibit more scattering and greater attenuation than fibers with less dopant in the core. That is why multimode fibers, with their higher level of dopant in the core, have higher attenuation than single-mode fibers. During manufacturing, regions of higher and lower molecular density areas, relative to the average density of the fiber, are created. Light traveling through the fiber interacts with the density areas as shown in Fig. 6. Light is then partially scattered in all directions. incidence decreases at the points with a too small curvature radius and the condition of total reflection is not achieved shown in Fig. 7. It is therefore necessary to maintain a sufficiently large curvature radius of a fiber when installing the cable nets. Bending loss is classified according to the bend radius of curvature: microbend loss or macrobend loss. Fig. 7 The losses caused by a bent fiber. Microbends are small microscopic bends of the fiber axis that occur mainly when a fiber is cabled. Macrobends are bends having a large radius of curvature relative to the fiber diameter. Microbend and macrobend losses are very important loss mechanisms. Fiber loss caused by microbending can still occur even if the fiber is cabled correctly. During installation, if fibers are bent too sharply, macrobend losses will occur. Microbend losses are caused by small discontinuities or imperfections in the fiber. Uneven coating applications and improper cabling procedures increase microbend loss. External forces are also a source of microbends. Macrobending occurs when a fiber is bent in a tight radius. The bend curvature creates an angle that is too sharp for the light to be reflected back into the core, and some of it escapes through the fiber cladding, causing attenuation. This optical power loss increases rapidly as the radius is decreased to an inch or less. Fibers with a high numerical aperture and low core/clad ratio are least susceptible to macrobend losses. Microbends change the path that propagating modes take, as shown in Fig. 8. Microbend loss increases attenuation because low-order modes become coupled with high-order modes that are naturally lossy. Fig. 8 Microbend loss Fig. 6 Light scattering 3)Bending Loss: When bending a fiber, the incidence angles of beams at the boundary between the core and the cladding of a fiber changes, consequently some beams get emitted from the fiber. A bent fiber results in losses caused by emittance and an increase in attenuation, because the angle of Macrobend losses are observed when a fiber bend's radius of curvature is large compared to the fiber diameter.
  5. 5. II. PROCEDURE All of our experiments are conducted using optical fibers with single mode characteristic. A. List of Main Equipments 1) Module KL-95001 Fiber Optic Lab Equipment (Fig. 9) 2) Tektronix TDS 2014 Four Channel Digital Storage Oscilloscope (Fig. 10) 3) Optical Fiber In Different Length of 1m, 3m, 5m, 10m (Fig. 11) Fig. 9 Module KL-95001 (CH1) input (red) and ground (black) was connected to the output of signal generator. 3) The oscilloscope of channel 2 (CH2) input (red) and ground (black) was connected to the Analog1 at the Receiver output. 4) The DC power supply was connected to the power jack of Module KL-95001 through the AC to DC Power Adapter. 5) The signal Generator’s Frequency and Amplitude knobs were set to have a 500Hz, 5Vp-p signal on the Analog output. The Receiver Gain know was adjusted to low level of gain. 6) The cinch nut of TX1 was loosened. One end of 1meter optical fiber cable is inserted into the TX1 until the tip of the fiber makes contact with the interior back wall of the photo detector. Tightened thecinch. The other end of optical fiber cable was inserted into RX1. The fiber optic must in straight condition (Fig. 12). 7) The Vp-p value of Receiver Analog1 output was measure from the oscilloscope CH2 and recorded in Table 1. The total attenuation was calculated using attenuation formula and recorded in Table 1. 𝑉𝑖 Attenuation = 20 log10 . 𝑉𝑜 8) Step 6 to 8 was repeated using different cable length of 3meter, 5meter (duplex) and 10meter (duplex) optical fiber. 9) The graph of attenuation against optical fiber length was plotted for 1meter, 3meter, 5meter (duplex) and 10meter (duplex) cable. Fig. 10 Tektronix TDS 2014 Four Channel Digital Storage Oscilloscope Fig. 11 Optical Fiber Fig. 12 The fiber optic must in straight condition B. Experiment 1: Attenuation due to Different Length of Optical Fiber Cable. Objective: 2) To study the effect of attenuation using different lengths of optical fiber cable. Equipment: 1) Module KL-95001 2) Optical fiber of length 1m, 3m, 5m and 10m 3) AC to DC power adapter 4) Oscilloscope 5) Connecting leads Procedure: 1) The Module KL-95001 was used to set up the circuit connections. 2) The Signal Generator Analogue output was connected to the Transmitter input. The oscilloscope of channel 1 C. Experiment 2: Attenuation due to Different Gap of Optical Fiber Cable. Objective: 3) To study the effect of attenuation using different gap of optical fiber cable. Equipment: 1) Module KL-95001 2) Optical fiber of length 1m, 3m, 5m and 10m 3) AC to DC power adapter 4) Oscilloscope 5) Ruler 6) Connecting leads Procedure: 1) The Module KL-95001 was used to set up the circuit connections. 2) The Signal Generator Analogue output was connected to the Transmitter input. The oscilloscope of channel 1
  6. 6. (CH1) input (red) and ground (black) was connected to the output of signal generator. 3) The oscilloscope of channel 2 (CH2) input (red) and ground (black) was connected to the Analog1 at the Receiver output. 4) The DC power supply was connected to the power jack of Module KL-95001 through the AC to DC Power Adapter. 5) The signal Generator’s Frequency and Amplitude knobs were set to have a 500Hz, 5Vp-p signal on the Analog output. The Receiver Gain know was adjusted to low level of gain. 6) The cinch nut of TX1 was loosened. One end of 1meter optical fiber cable is inserted into the TX1 until the tip of the fiber makes contact with the interior back wall of the photo detector. Tightened thecinch. The end of another 1meter optical fiber cable was inserted into RX1. The fiber optic must in straight condition (Figure 12). 7) The cable gap width of both another ends of 1meter optical fiber cable was measured by using ruler at 0mm shown in Fig. 13. 8) The Vp-p value of Receiver Analog1 output was measure from the oscilloscope CH2 and recorded in Table 2. The total attenuation was calculated using attenuation formula and recorded in Table 2. 𝑉𝑖 Attenuation = 20 log10 . 𝑉𝑜 9) Step 6 to 8 was repeated using different cable gap of 1mm, 2mm, 3mm and 4mm optical fiber. 10) Step 6 to 9 was repeated using different cable length of 3meter, 5meter (duplex) and 10meter (duplex) optical fiber. 11) The graphs of total attenuation (TA) of gap against optical fiber cable gap of 1meter, 3meter, 5meter (duplex) and 10meter (duplex) cable length was plotted on the same graph. 12) The attenuation of gap was calculated using attenuation of gap formula and recorded in Table 3. 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 (𝐴) 𝑜𝑓 𝑔𝑎𝑝 = 𝑇𝑜𝑡𝑎𝑙 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 (𝑇𝐴) 𝑜𝑓 𝑔𝑎𝑝 −𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑓𝑖𝑏𝑒𝑟 𝑙𝑒𝑛𝑔𝑡ℎ 13) The graphs of attenuation (A) of gap against optical fiber cable gap of 1meter, 3meter, 5meter (duplex) and 10meter (duplex) cable length was plotted on the same graph. Fig 13 Experiment attenuation of gap D. Experiment 3: Attenuation due to Different Bendding of Optical Fiber Cable Objective: 3) To study the effect of attenuation using different bending of optical fiber cable. Equipment: 1. Module KL-95001 2. Optical fiber of length 1m, 3m, 5m and 10m 3. AC to DC power adapter 4. Oscilloscope 5. Ruler 6. Connecting leads 1) Procedure: 2) The Module KL-95001 was used to set up the circuit connections. 3) The Signal Generator Analogue output was connected to the Transmitter input. The oscilloscope of channel 1 (CH1) input (red) and ground (black) was connected to the output of signal generator. 4) The oscilloscope of channel 2 (CH2) input (red) and ground (black) was connected to the Analog1 at the Receiver output. 5) The DC power supply was connected to the power jack of Module KL-95001 through the AC to DC Power Adapter. 6) The signal Generator’s Frequency and Amplitude knobs were set to have a 500Hz, 5Vp-p signal on the Analog output. The Receiver Gain know was adjusted to low level of gain. 7) The cinch nut of TX1 was loosened. One end of 1meter optical fiber cable is inserted into the TX1 until the tip of the fiber makes contact with the interior back wall of the photo detector. Tightened thecinch. The other end of 1meter optical fiber cable was inserted into RX1. The fiber optic must in straight condition (Figure 12). 8) The optical fiber cable was bent of 3 loop to have a bend diameter of 10mm as shown in Figure 14. 9) The Vp-p value of Receiver Analog1 output was measure from the oscilloscope CH2 and recorded in Table 4. The total attenuation was calculated using attenuation formula and recorded in Table 4. 𝑉𝑖 Attenuation = 20 log10 . 𝑉𝑜 10) Step 6 to 8 was repeated using different bending diameter of 20mm, 30mm and 40mm optical fiber. 11) Step 6 to 9 was repeated using different cable length of 3meter, 5meter (duplex) and 10meter (duplex) optical fiber. 12) The graphs of total attenuation (TA) of bending against optical fiber bending diameter of 1meter, 3meter, 5meter (duplex) and 10meter (duplex) cable length was plotted on the same graph. 13) The attenuation of gap was calculated using attenuation of bending formula and recorded in Table 5. 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛(𝐴) 𝑜𝑓 𝑏𝑒𝑛𝑑𝑖𝑛𝑔 = 𝑇𝑜𝑡𝑎𝑙 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛(𝑇𝐴) 𝑜𝑓 𝑏𝑒𝑛𝑑𝑖𝑛𝑔 − 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑓𝑖𝑏𝑒𝑟 𝑙𝑒𝑛𝑔𝑡ℎ
  7. 7. 14) The graphs of attenuation (A) of bending against optical fiber bending diameter of 1meter, 3meter, 5meter (duplex) and 10meter (duplex) cable length was plotted on the same graph. 3 4 0 1 2 3 4 0 1 2 3 4 5 10 25 A. Experiment 1: Attenuation due to Different Length of Optical Fiber Cable TABLE 1 THE ATTENUATION OF DIFFERENT LENGTH OF OPTICAL FIBER Output Voltage (Vpp) 2.6 2.2 1.8 1.2 Attenuation (dB) Attenuation (dB) III. RESULT 20 15 10 5 0 5.86 7.13 8.87 12.40 0 1 Attenuation (dB) The Attenuation against Different Length of Optical Fiber 15 5.86 8.87 Attenuation of Fiber Length (dB) Optical Fiber Length (m) 3m 5m 10m 1 5.86 3 7.13 5 8.87 10 12.40 Graph 1 The Attenuation against Different Length of Optical Fiber B. Experiment 2: Attenuation due to Different Gap of Optical Fiber Cable TABLE 2 THE TOTAL ATTENUATION (TA) OF DIFFERENT GAP OF OPTICAL FIBER Fiber Length (m) 1 3 3m 5m Cable Gap Width (mm) 0 1m Cable Gap Width (mm) 0 1 2 3 4 0 1 2 Output Voltage (Vpp) 1.6 1.4 1.2 0.8 0.6 1.2 1.0 0.8 Total Attenuation (TA) of Gap (dB) 9.90 11.06 12.40 15.92 18.42 12.40 13.98 15.92 4 10m TABLE 3 THE ATTENUATION (A) OF DIFFERENT GAP OF OPTICAL FIBER Optical Fiber Length (m) 5 3 Graph 2 The Total Attenuation (TA) of Gap against Different Gap of Optical Fiber 12.4 7.13 2 Cable Gap Width of Optical Fiber (mm) 1m 10 18.42 21.94 13.92 15.92 18.42 18.42 21.94 15.92 18.42 18.42 18.42 21.96 The Total Attenuation (TA) of Gap against Different Gap of Optical Fiber Fig. 14 Experiment attenuation of bending Optical Fiber Length (m) 1 3 5 10 0.6 0.4 1.0 0.8 0.6 0.6 0.4 0.8 0.6 0.6 0.6 0.4 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 Total Attenuati on (TA) of Gap (dB) 9.90 11.06 12.40 15.92 18.42 12.40 13.98 15.92 18.42 21.94 13.92 15.92 18.42 18.42 21.94 15.92 18.42 18.42 18.42 21.96 Attenuation (A) of Gap(dB) -1.82 -0.66 0.68 4.2 6.7 -1.86 -0.28 1.66 4.16 7.68 -3.82 -1.82 0.68 0.68 4.2 -8.88 -6.38 -6.38 -6.38 -2.84
  8. 8. Graph 4 The Total Attenuation (TA) of Bending against Different Bending of Optical Fiber The Attenuation (A) of Gap against Different Gap of Optical Fiber Attenuation (dB) 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛(𝐴)𝑜𝑓 𝑔𝑎𝑝 = 𝑇𝑜𝑡𝑎𝑙 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛(𝑇𝐴) 𝑜𝑓 𝑔𝑎𝑝 − 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 𝑑𝑢𝑒 𝑡𝑜 𝑓𝑖𝑏𝑒𝑟 𝑙𝑒𝑛𝑔𝑡ℎ TABLE 5 THE ATTENUATION (A) OF DIFFERENT BENDING OF OPTICAL FIBER Optical Fiber Length (m) 10 5 0 -5 -10 0 1 2 3 3m 5m 1 5.86 3 7.13 5 8.87 10 12.40 4 Cable Gap Width of Optical Fiber (mm) 1m Attenuati on of Fiber Length (dB) 10m Graph 3 The Attenuation (A) of Gap against Different Gap of Optical Fiber C. Experiment 3: Attenuation due to Different Bending of Optical Fiber Cable TABLE 4 THE TOTAL ATTENUATION (TA) OF DIFFERENT BENDING OF OPTICAL FIBER Bending Diameter (mm) Output Voltage (Vpp) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 1.60 2.00 2.20 2.40 1.60 1.80 2.00 2.20 1.20 1.60 1.80 2.00 1.00 1.20 1.40 1.60 1 3 5 10 Total Attenuation (TA) of Bending (dB) 9.90 7.96 7.13 6.38 9.90 8.87 8.00 7.13 12.4 9.90 8.87 8.00 13.98 12.39 11.06 9.90 The Total Attenuation (TA) of Bending against Different Bending of Optical Fiber Attenuation (dB) 15 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 Total Attenuation (TA) of Bending (dB) 9.90 7.96 7.13 6.38 9.90 8.87 8.00 7.13 12.4 9.90 8.87 8.00 13.98 12.39 11.06 9.90 Attenuation (A) of Bending (dB) -1.82 -3.76 -4.59 -5.34 -4.36 -5.39 -6.26 -7.13 -5.34 -7.84 -8.87 -9.74 -10.82 -12.41 -13.74 -14.9 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛(𝐴)𝑜𝑓 𝑏𝑒𝑛𝑑𝑖𝑛𝑔 = 𝑇𝑜𝑡𝑎𝑙 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛(𝑇𝐴) 𝑜𝑓 𝑏𝑒𝑛𝑑𝑖𝑛𝑔 − 𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 𝑑𝑢𝑒 𝑡𝑜 𝑓𝑖𝑏𝑒𝑟 𝑙𝑒𝑛𝑔𝑡ℎ The Attenuation (A) of Bending against Different Bending of Optical Fiber 0 10 Attenuation (dB) Optical Fiber Length (m) Bending Diameter (mm) 20 30 40 -5 -10 -15 -20 Bending Diameter of Optical Fiber (mm) 1m 3m 5m 10m Graph 5 The Attenuation (A) of Bending against Different Bending of Optical Fiber IV. DISCUSSION 10 5 0 10 20 30 40 Bending Radius of Optical Fiber (mm) 1m 3m 5m 10m A. Experiment 1: Attenuation due to Different Length of Optical Fiber Cable This experiment was done to study the effect of attenuation using different lengths of optical fiber cable. The result of experiment using 1meter optical fiber cable shown that the output voltage is lower than input voltage. This means it effect will voltage gain at the receiver analog input. From our experiment we were used lower gain and fixed the gain for all experiment. The procedure for experiment 1 is repeated with
  9. 9. different lengths of 1meter, 3meter, 5meter (duplex) and 10meter (duplex) optical fiber cable. In this experiment, as the length of the fiber optic increases, the output voltage drops and the attenuation increases. This is due to more power loss in the fiber optic over the length. This power loss is due to scattering and absorption. Scattering losses are caused by the interaction of light with density fluctuations within a fiber. Scattering losses is the reflection of small amounts of light in all directions as it travels down the fiber. Some of this light escapes out of the core, while some travels back toward the source. Absorption occurs when impurities, such as metal particles or moisture, are trapped in the glass. These cause attenuation at specific wavelengths by absorbing the light at that wavelength and dissipating it in the form of heat energy. B. Experiment 2: Attenuation due to Different Gap of Optical Fiber Cable Gap loss is a type of signal strength loss that occurs in fiber optic transmission when the signal is transferred from one section of fiber or cable to another. Specifically, gap loss happens when the signal from one end of a piece of cable is transferred to another, but there is a space, breakage, or gap between them. Since fiber optics transmit data via light the light can cross this gap, but spreads out and is weakened and diffused when it does so. In this experiment, as the length of the gap increase, larger amount of the transmitted power loss at the receiving core. As a result of signal strength and cohesion being lost (due to the scattering of the light), a fiber optic signal suffering from gap loss is degraded in both quality and throughput. C. Experiment 3: Attenuation due to Different Bending of Optical Fiber Cable In this experiment, as the radius for bending of the fiber increase, the attenuation will decrease. When bending a fibre, the incidence angles of beams at the boundary between the core and the cladding of a fibre changes, consequently some beams get emitted from the fibre. A bent fibre results in losses caused by emittance and an increase in attenuation, because the angle of incidence decreases at the points with a too small curvature radius and the condition of total reflection is not achieved. It is therefore necessary to maintain a sufficiently large curvature radius of a fibre when installing the cable nets. V. CONCLUSIONS In conclusion, the objective of this report was met. Experiments were carried out as you can see from the result section. In this experiment, as the length and the gap of the fiber optic increases, the output voltage drops and the attenuation increases. As the radius for bending of the fiber increase, the attenuation will decrease. The results obtained were acceptable. From our experiment, we use lower gain to our circuit at the receiver. This will make the output voltage lower than input voltage but it will make difficulties to get the reading of output voltage. The reading is slightly different. To improve the result we need to use higher gain so that we can get result with better and can more clearly to compare the different. ACKNOWLEDGMENT We would like to express our deepest gratitude and appreciation to our laboratory instructor Dr Yusri bin Md Yunus for his excellent guidance, caring, patience, suggestions and encouragement who helped usto coordinate our project especially to design the link. We would also like to acknowledge with much appreciation to all those who gave us the possibility to complete this project. A special thanks goes to the crucial role of the staff of the Optic Communication Laboratory. Last but not least, again we would like to say many thanks go to our laboratory instructor, Dr Yusri bin Md Yunus who are given as full effort guiding in our team to make the goal as well as the panels especially in our project presentation that has improved our presentation skills by their comment and tips. REFERENCES [1] [2] [3] [4] [5] (2013, 5/11/2013). How Fiber Optic Work. Available: http://computer.howstuffworks.com/fiber-optic1.htm (2013, 5/11/2013). How Fiber Optic Communication System. Available: http://www.itblogs.in/communication/technology/fiberoptic-communication-sytem/ (2013, 5/11/2013). Attenuation of Optical Fiber. Available: http://www.thefoa.org/tech/ref/testing/test/loss.html (2013, 5/11/2013). halit eren. "optical loss." copyright 2000 crc press llc <http://www.engnetbase.com> (2013, 5/11/2013). Optical Fiber Loss and Attenuation. Available: http://www.fiberoptics4sale.com/wordpress/optical-fiber-loss-andattenuation/

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