polymer optical fibers
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POLYMER OPTICAL FIBERS
TOPICS TO BE DISCUSSED Introduction Principle Of Optical Fiber Communication History Of Polymer Optical Fiber Comparison of Polymer and Glass Optical Fiber Classification Of Pofs Materials Used In Pofs Application Of Pofs Fabrication Of Pofs Fabrication Of Si- Pofs Fabrication Of GI- Pofs Polymer Optical Fiber Plastic Optical Fiber Passive Devices Future Aspects Of Pofs Potential Of Pofs
INTRODUCTIONAn optical fiber (or optical fiber) is
a flexible, transparent fiber made by drawing glass or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths
Plastic optical fiber (POF)is an optical fiber that is made out of polymer. Similar to glass optical fiber, POF transmits light (for illumination or data) through the core of the fiber.
PRINCIPLE OF OPTICAL FIBER COMMUNICATIONPrinciple of operation- Total Internal
HISTORY First introduced in 1960 by Dupont at nearly the same time
Glass optical fibers were introduced. Faced problems of very high attenuation of the order of 1000
dB/km. Application in communication almost impossible. Mitsubishi Rayon, Japan improved Dupont’s technology to
reduce attenuation to 300dB/ km but still quite high value. In 1980 Graded Index POFs were introduced. New processing techniques such as swollen Gel
Polymerization helped reduced attenuation problem considerably.
In mid 1990s the use of POFs for short distance high speed communication were introduced.
COMPARISON B/W POFs & GOFsPOLYMER OPTICAL FIBER
Plastic optical fiber, polymer optical fiber is an optical fiber which is made out of plastic. It comprises of PMMA as the core that facilitates the transmission of light, and fluorinated polymers as the cladding material.
Simpler and less expensive components.
Greater flexibility and light weight.
Bit rate upto 10Gbps.
GLASS OPTICAL FIBERS
Glass optical fiber, just as its name shows, is an optical fiber made of glass. Being a delicate type of optical fiber, it cannot be cut, spliced or repaired.
Difficult handling and delicate. Less resistant to flexibility and
accidental breakage. Higher information
transmission capacity & lower losses.
Used in low speed and short distance applications (upto 100 m).
Generally in car networks, home networks, industrial networks etc.
Used in longer distance transmissions at higher speeds.
Under ground data transmission systems etc.
TYPES OF POLYMER OPTICAL FIBERS
PLASTIC OPTICAL FIBRES
STEP INDEXED PLASTIC
GRADED INDEXED PLASTIC
STEP INDEX POLYMER OPTICAL FIBERS
A step index plastic optical fibre has a simple structure of a concentric core and cladding. Consequently rather simple methods can be used for its fabrication
GRADED INDEX POLYMER OPTICAL FIBERS
GI POFs has drawn considerable interest recently as a high band width data transmission medium for short distance application .
MATERIALS USED IN POFsPMMA
PMMA are used as the core, with refractive indices of 1.49.
Generally, fiber cladding is made of silicone resin (refractive index ~1.46).
High refractive index difference is maintained between core and cladding.
High numerical aperture. Have high mechanical flexibility and
low cost. Industry-standard step-index fiber has
a core diameter of 1mm. Attenuation loss is
about 1 dB/m @ 650 nm. Bandwidth is ~5 MHz-km @ 650 nm.
FLUORINATED POLYMERS Fluorine (F) has a greater
mass than both H and D, allowing for lower attenuation, theoretically approaching that of silica glass fiber.
Fluorinated polymers such a s poly tetra fluoro ethylene or Teflon) typically form the crystalline structures.
Random copolymers result in the least amount of crystallization.
APPLICATIONSCurrently the application of POFs can be
divided into four major categories:LightingCommunications.Sensors.Automobiles.
LIGHTINGDecorations- lamps and
mechanical welds in pipes and engines (airlanes, rockets and automobiles).
Medical applications- Endiscopes, Bronchoscpoes, Laproscopes
COMMUNICATION•Research is being conducted to reduce attenuation and increase bandwidth to increase usage in long distance communication.•Ideal for short distance network cabing - New standard for LAN cabling. -Material cost fall between copper and glass. -Ease of installation.•Gigabit Ethernet- Transport of 1.25Gbit/s Ethernet traffic over 900 m has been demonstrated successfully.
SENSORS Optical measurement of flow, biofilm growth, toxicity, rotation, humidity,
fluoroscence. Humidity measurement - POG with PVA film. -Oil insulated power equipment. Toxicity biosensors. - The fluoroscence produced by biological reaction is collected and transmitted
AUTOMOBILES•The number of electronic devices in a car increases year by year, primarily due to an increase in the entertainment equipment desired for modern passenger cars.
•This ubiquitous connection need is a huge problem in networking system designs for automotive fiber from the viewpoint of both physical space and system load. Consequently, POF is specified in the MOST standard to achieve the lowest overall system weight and easiest connectivity
FABRICATION OF POFsSTEP INDEXED
POLYMER OPTICAL FIBRES
Continous Extrusion Method
GRADED INDEXED POLYMER
OPTICAL FIBRES Photo-
Swollen Gel Polymerisation
Closed Co-Extrusion Method
FABRICATION OF STEP INDEX POFs
A step Indexed plastic optical fiber has a simple structure of a concentric core aand cladding. Consequently rather simple fabrication techniques can be applied for its fabrication, these techniques are described as under.
1. Continous Extrusion Technique.2. Preform Method
CONTINOUS EXTRUSION METHODThe polymer which becomes the core of SI- POF is then fed into a extruder by a gear pump. The extruder is capable of devolatalisation, which removes monomer residue and returns them to the reactor. The core material and the cladding material, which are fed by separate extruders, proceed into a extrusion die where concentric core - cladding structure of an SI- POF is formed.
PREFORM METHOD (SI POFs)Method involves
two stages:1. A cylindrical
preform 1-5 cm in diameter and upto 1 m in length is made.
2. The preform is drawn into a fiber by heat drawing process.
FABRICATION OF GI- POFsGI- POF has drawn considerable attention in the recent past as a high
bandwidth data transmission medium. The bandwidth of the POF is maximized by optimizing the Distribution of Refractive Index. Thus in manufacturing of GI- POF, the obtainable bandwidth of a GI POF is directly related to the ability to control profile. To date several methods have been proposed to for the manufacture of GI POF. These methods are described in the upcoming sections.
Photo copolymrization. Swollen Gel Polymerization. Closed Extrusion Method. Centrifugal Method.
PHOTO COPOLYMERISATION (GI POFs)
• A 2.9 mm diameter glass tube was was filled with a monomer mixture methyl methacrylate and vinyl benzoate and an initiator benzoyl per oxide. the glass tube reactor was then positioned vertically in a constant temperature chamber and rotated about its vertical axis• It is irradiated by UV. the UV radiation was applied locally by using a shade while the UV lamp transversed from the bottom of the tubular reactor to the top at a constant speed.
SWOLLEN GEL COPOLYMERIZATION (GI POFs)
A two stage process:1. The monomer mixture is filled in the polymer tube to form gel at a lower
temperature to form a gel without significant copolymerization.2. The temperature is raised to polymerization temperature to polymerize the
monomer, hence a rod is formed, which can be drawn into graded index polymer optical fibre.
CLOSED CO EXTRUSION METHOD (GI POFs)
• Versatile technology for making GI POFs.•The figure shows a schematic diagram of the a N layer internal diffusion and surface evaporation co extrusion process.•The tanks labeled 1- N are filled with polymer melts.•They are arranged so that when fed to the concentric die the materials are in decreasing order of the refractive index of the polymers. •It is thed passed through a hardening zone H and is then receives by rolls.
CENTRIFUGAL METHOD (GI POFs)
The centrifugal method is regarded as a potential method for the preparation of the GI polymer rods because of the ability to form large diameter GI rods. The figure here shows the schematic representation of the preparation of the GI polymeric rods by centrifugal method. Many aspects of this method are still being studied
POLYMER OPTICAL FIBER GRATINGS
Fiber Bragg Grating is characterised by a periodic index change induced by ultraviolet irradiation in the core along the fiber. Light propagating along the fiber grating is periodically and partially reflected in accordance with the pattern of the index change. When theses reflections are in phase, they can produce an enhanced near 100% reflection.
FABRICATION OF POF GRATINGS ABLATION: This involves melting and burning the polymer surface.
CHAIN SCISSION: This involves breaking the polymer chains, thus decreasing the chain density, which in turns reduces the refractive index.
CROSS LINKING: This involves inducing free radicals and then
giving rise to the combination of polymer chains. This has the effect of increasing the density of chains, thus increasing the refractive index of the polymer.
PHOTO POLYMERISATION: The incident light generates free
radicals , thus causing the polymerization of unreacted monomer within the polymer. As a result, the polymerization density increases and the refractive index increases accordingly.
POF PASSIVE DEVICES OPTICAL COUPLERSIn applications of POF such as signalising, lighting, and decoration systems, where it is necessary to distribute or redirect incoming light to other outgoing fibers, to split or combine optical signals into two or more fibers
FILTERSLarge core optical fiber have as in polymer optical fiber have a large number of propogation node which can cause to noise in communication hence filters are employed. Obtained by wrapping a pof in a small diameter cylinder.
TAPERSFor some applications such as light emitting diode to POF coupling, step index to GI POF coupling, collimation , it is necessary to reduce the fiber diameter.
LENSESFor many applications it is necessary to use a Fiber Integrated Lens, which is a device that fits the fiber size and is used to focus or collimate the the fiber output light beam
FUTURE ASPECTS Polymer Optic
Fibers Polymer optical fibers offer many benefits when compared to other data communication solutions such as copper cables, wireless communication systems, and glass fiber.
•In comparison with glass optical fibers, polymer optical fibers provide an easy and less expensive processing of optical signals, and are more flexible for plug interconnections .• The use of polymer optical fibers as the transmission media for aircrafts is presently under research by different Research and Development groups due to its benefits. The German Aerospace Center have concluded that “the use of Polymer Optical Fibers multimedia fibers appears to be possible for future aircraft applications. •In the future, polymer optical fibers will likely displace copper cables for the last mile connection from the telecommunication company’s last distribution box and the served end consumer.
REFERENCES Hari Singh Nalwa.(Ed.).(2004). Polymer Optical
Fibers. American Scientific Publishers.• Chang-Won Park. Fabrication Techniques for Plastic Optical Fibers. USA• Wen-Chang Chen,
Jui-Hsiang Liu, Yung Chang, Ming-Hsin Wei, and Hong-Wen Su. Gradient-Index Polymer Optical Fibers: Analysis of Fabrication Techniques. Taiwan.
• Giok-Djan Khoe, Henrie van den Boom, and Idelfonso Tafur Monroy. High Capacity Transmission System. The Netherlands
• G. D. Peng and P. L. Chu. Polymer Optical Fiber Gratings, Australia.• Liliana R. Kawase. Plastic Optical Fiber Passive Device. Brazil.
An overview on fabrication method for polymer optical fibers. Christian -Alexander Bunge. www.academia.edu
Plastic optical fiber Vs Glass optical Fiber. Retrieved from www.fiberopticsshare.com.
Polymer optical fiber (n.d). Retrieved February 5, 2016, from en.wikipedia.org/wiki/Plastic_optical_fiber.