Copyright 2003 Fiber-Optic Transmission System All communication systems have three things in common: –A signal source –A medium for the signal to travel through –A receiver
Copyright 2003 Optical Transmitter An optical transmitter is simply a source of light, like a light bulb. The optical receiver is a semiconductor that changes light into a corresponding electrical signal. –It is generically called an optical-to-electrical converter.
Copyright 2003 Optical Transmission In fiber optics, information is carried by modulating the light power, not the wavelength or frequency of the light. Wavelength-division multiplexing (WDM), allows more than one wavelength to be sent over a single fiber, thereby increasing the capacity of the fiber.
Copyright 2003 Reflection and Refraction Reflection is a light ray that bounces off the interface of two materials at the same angle it hits. Refraction is the bending of the light ray as it changes speed going from one material to another.
Copyright 2003 IOR IOR is the ratio of the speed of light in a vacuum to the speed of light in a fiber. IOR is a measure of the density of a fiber because denser materials (higher IOR) cause light to travel more slowly.
Copyright 2003 Fiber Types A fiber-optic cable has three components: –Protective outer coating Also known as buffer coating. –Inner cladding The cladding is of a different density than the core, so the light bounces against it. –Fiber core The core is doped with chemicals that enhance its transmission properties.
Copyright 2003 Multimode Multimode fiber is used to transmit many signals per fiber. Multimode allows many paths or modes for the light.
Copyright 2003 Single Mode Single-mode fiber is used to transmit one signal per fiber. Single-mode fiber allows only one path for the signal to travel down the middle of the fiber. The entire signal travels the length of the fiber at the same rate, allowing for much higher data rates.
Copyright 2003 Loss Factors Connector loss Macrobending Microbending Absorption
Copyright 2003 Attenuation Attenuation refers to the decrease in the strength of a signal during transmission. Attenuation is a natural consequence of signal transmission over long distance. Two primary factors affect attenuation in optical fibers: –Length of the fiber –Wavelength of the light
Copyright 2003 Optical Filters Optical filters are used to identify different wavelengths or lambdas. Fiber bragg grating and the dielectric filter are examples of optical filters.
Copyright 2003 Optical Amplifier The optical amplifier (OA) is a device that amplifies an input optical signal terahertz (THz) of optical bandwidth near 1550 nm.
Copyright 2003 Optical Transmission and Multiplexing
Copyright 2003 SONET SONET is the standard for synchronous data transmission on optical media used in North America. SDH is the international equivalent of SONET. Service providers who are using a ring topology primarily deploy SONET. The two prevalent types of rings in networks today are unidirectional path-switched rings (UPSRs) and bidirectional line-switch rings (BLSRs).
Copyright 2003 DWDM DWDM is a technology that transmits multiple signals simultaneously at different wavelengths, allowing a single fiber to operate as if it were multiple fibers. DWDM works in conjunction with optical networks to make data transmission fast and cost effective.