Fiber Materials

Fiber Materials Freeda Yesudas Requirements.It must be possible to make long, thin and flexible fibers from materials.Material must be transparent at a particular optical wavelength.Physically compatible materials that have slightly different r.i for the core and cladding must be availableMaterials GlassesSilica or silicate High loss glass fibers with large core used for short transmission distance Low loss fibers employed in long haul applications.Plastics ( less widely used high attenuation than glass fibers).Short distance applications and in abusive environment (100s of meters).

Glass fibers Made by fusing selenide, sulfides, or oxides- randomly connected moleculesGlass do no have a well defined melting point.When glass is heated up from room temp-it remains solid-several 100s of degree centigrade.Melting temperature- extended temperature range in which the glass become fluidGlass fibers Properties Resistance to deformation at temp as high as 1000 degree C,High resistance to breakage from thermal shock because of its low thermal expansion, good chemical durability and high transparency in both ir and visible region.

Halide glass fiberLow transmission loss at mid infrared region (0.2-0.8microm)Anions are from group VII of the periodic table-fluorine, chlorine, bromine and iodine.ZBLAN fluoride glass(Zr, Ba, La Al, Na)- core lower refractive ZHBLAN- partially replaces Zr by Ha index glassAlthough it gives min loss-(0.01-0.001dB/km) fabricating long length is difficult.Cont.Ultrapure materials must be used to reach this low loss level.Fluoride glass is prone to devitrificationActive glass fiber Incorporating rare earth elements (atomic numbers 57 - 71) converts normal passive glass fiber into new materials with new optical and magnetic properties.The new materials perform amplification, attenuation and phase retardation on the passing lightDoping can be carried out for silica, tellurite and halide glassesCommonly used materials are Erbium and Neodymium Plastic material

Plastic fiber has poor optical qualities as compared to glass.Plastic fibers are more economical over short distances for slower speedsPlastic-Clad Silica Fiber.The above fiber uses a high quality glass core, clad with a low cost plastic sheathing.The cost and performance of plastic-clad Silica fiber is a compromise between the all-glass and all plastic fibers.

Plastic optical fiberHigh demand for delivering high speed services to the work station require high bandwidth graded index polymer (plastic) optical fibers (POF).POFs are used within the premises of user.Fiber with core of polymethylmethacrylate referred as (PMMA POF) Fiber with core of perfluorinated polymer is referred as PF POFPOFs have greater attenuation as compared to glass fibers.POFs are tough and durable as compared to glass fibersModulus is two order of magnitude smaller than the glass fiber so flexible to install.Compared with glass fiber the core diameter is 10 20 times largerInexpensive plastic injection moulding technologies can be used to fabricate connectors, splices and transceivers

References Gerd keiser third edition- Optical Fiber Communications.Thank you