1 Fiber Optics: An Introduction Carey Williamson University of Calgary

2 Introduction u Optical fiber makes possible the transmission of digital data at several gigabits per second (Gbps) over long distances with very low error rates

3 Optical Fiber u Manufactured from refined glass u Very few impurities u Very thin (e.g., 8-12 microns for core) u Core is surrounded by cladding Cladding Core

4 Fiber-based Transmission u Bits are represented as pulses of light u Transmitted using lasers u Light pulses, once transmitted into the core, continue to travel down the fiber, according to the physical principle of total internal reflection u Very little signal attenuation (loss)

5 Fiber Optic Transmission u Transmission performed using laser u Usually a fixed wavelength u Some are tunable to different wavelengths u Receiver uses photo-electric diode to detect incoming signals u Usually a fixed wavelength u Some are tunable to different wavelengths u Optical-electrical conversions required

6 Fiber Optic Transmission u Can transmit using several different wavelengths on the same fiber (monomode versus multimode fiber) u Called Wavelength Division Multiplexing (WDM) u Same principle as Frequency Division Multiplexing (FDM)

7 Fiber Optics: Facts u Optical fiber works best with wavelengths of light around either 0.85, 1.3, or 1.5 microns u Each band has a theoretical bandwidth of approximately 25 TeraHz u Current laser technology can achieve several Gbps

8 Fiber Optic Transmission u Various physical layer phenomena serve to constrain the current achievable bandwidth on optical fiber u Dispersion: modal, chromatic, material u Absorption u Attenuation u Repeaters or amplifiers are needed to facilitate long range transmission

9 Summary u Optical fiber offers immense bandwidth u B-ISDN/ATM assumes fiber optic based transmission at the physical layer u International standard for fiber-based transmission: SONET (Synchronous Optical Network)