Outside Plant Fiber Optics Module 2 Lesson 2 Transmission Systems This is a basic fiber optic training program outside plant communication for Transmission Systems.

Fiber Optic Data Links Transmit over two fibers for full duplex Transceivers convert to/from electrical signals Photodetectors receive signals from fiber Fiber optic transmission systems all consist of a transmitter which takes an electrical input and converts it to an optical output . The light from the transmitter is coupled into the fiber with a connector and is transmitted through the fiber optic cable plant. The light is ultimately coupled to a receiver where a detector converts the light into an electrical signal which is then conditioned properly for use by the receiving equipment. Most links use two fibers transmitting in opposite directions for full duplex operation. FTTx PON systems use one fiber bidirectionally, using wavelength division multiplexing. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Optics Links Use Infrared Light Jargon to remember: Wavelength is a measure of the "color" of light Light at these wavelengths is called "infrared" light Infrared light is invisible to your eye, so potentially harmful light can be present in a fiber but you can't see it! Check with a power meter. Here is some fiber optic jargon to remember: Wavelength is a measure of the "color" of light. Visible light is about 500-600 nm wavelength. Beyond that we call it "infrared" light. At longer(infrared) wavelengths, fiber has lower attenuation, so most systems transmit in that region. Safety note: Infrared light is invisible to your eye, so potentially harmful light can be present in a fiber but you can't see it! Check with a power meter. FOA Fiber Optic Curriculum ©2012 The FOA

Optical Fiber Technology Light travels in the core Light is trapped in the core by the optical cladding Buffer or primary coating protects fiber from moisture or damage Most fibers are all glass, but glass core/plastic clad (PCS/HCS) and all plastic (POF) are made Optical fiber is comprised of a light carrying core surrounded by a cladding which traps the light in the core by the principle of total internal reflection. Most optical fibers are made of glass, although some are made of plastic. The core and cladding are usually fused silica glass which is covered by a plastic coating called the buffer which protects the glass fiber from physical damage and moisture. Most fibers are all glass, but glass core/plastic clad (PCS - plastic clad silica and HCS - hard clad silica) and all plastic (POF - plastic optical fiber) are made. Glass optical fibers are the most common type used in communication applications. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Optic Link Power Budget Power budget determines if link will work over loss of cable plant Determined by analysis during design After a fiber optic cable plant is installed, it may be used with a number of different types of fiber optic networks. Every fiber optic link has a maximum loss of a cable plant over which it can work. That loss is determined by the output power of the transmitter coupled into the fiber and the sensitivity of the receiver, all expressed in dB.. The loss of the fiber optic cable it uses must be less than 1that maximum loss for proper operation. The drawings here illustrate the example. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Optic Link Power Budget But look at the diagram closely. The power goes down as the light goes down the fiber, reduced by the attenuation of the fiber and the losses in connectors and splices. The power level starts at the transmitter output, coupled into the fiber, shown at the top of the X-axis of the graph. After the loss of the cable plant, it is reduced by the amount of the loss. In order for the link to work properly, the power at the receiver must be higher than the receiver sensitivity, shown at the bottom of the X-axis of the graph. The amount by which the receiver power exceeds the receiver sensitivity is the margin of the link. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Optic Components Fiber Cable Connectors Splices Hardware Test equipment Fiber transmits the signal as light Cable protects fibers in the application environment Connectors join fibers or connect to active devices so they can be disconnected for rerouting, testing, etc. Splices join two fibers permanently Hardware provides the mounting, protection, etc. for connectors or splices Test equipment checks performance Now let’s take a look at the components of a fiber optic system. We’ll examine each of these in detail and look at their installation. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Types Defined by core size and material composition Multimode has large core that transmits multiple modes or rays of light Singlemode has small core that transmits only one modes of light Step index fibers have core of same index of refraction so modes travel in straight lines Graded index fiber has core that guides modes to reduce dispersion Optical fiber has two basic types, multimode and singlemode. Multimode fiber means that light can travel many different paths (called modes) through the core of the fiber, which enter and leave the fiber at various angles. In graded index multimode fiber, the core is composed of many different layers of glass, chosen with indices of refraction to produce an index profile approximating a parabola. Since the light travels faster in lower index of refraction glass, the light will travel faster as it approaches the outside of the core. Likewise, the light traveling closest to the core center will travel the slowest. Singlemode fiber just shrinks the core size to a dimension about 6 times the wavelength of the fiber, causing all the light to travel in only one mode. Thus modal dispersion disappears and the bandwidth of the fiber increases by at least another factor of 1000 over graded index fiber. FOA Fiber Optic Curriculum ©2012 The FOA

Protecting The Fiber: Cable First layer of protection is the primary buffer coating of 250 µm diameter on the glass fiber Tight buffer fibers have secondary buffer coating of 900 µm diameter Cable provides strength members and jacket for protection Because of the wide variety of conditions to which they are exposed, optical fibers have to be encased in several layers of protection. The first of these layers is the primary buffer coating, a thin protective coating made of ultraviolet curable acrylate ( a plastic), which is applied to the glass fiber as it is being manufactured. This thin coating provides moisture and mechanical protection. The next layer of protection is a buffer, that is typically extruded over this coating to further increase the strength of the single fibers. This buffer can be either a loose tube or a tight tube.The next layer is a strength member, usually an aramid fiber, that can be used for pulling the cable. Finally, the entire cable is covered by a jacket designed to withstand the environment into which the cable is going to be installed. FOA Fiber Optic Curriculum ©2012 The FOA

Outside Plant Cables By Cable Design By Installation Method Loose tube Underground in conduit Direct Buried Aerial Submarine By Cable Design Loose tube Armored Aerial Submarine/underwater Outside plant cables can be characterized by installation method or by cable design. Installations include underground with cables pulled into ducts, direct buried cables in trenches or plowed-in, aerial cables (lashed to a messenger or self-supporting) and cables installed underwater (submarine.) FOA Fiber Optic Curriculum ©2012 The FOA

Premises Cable Inside building Short runs for less that 1,000 feet Multimode Fiber Operates at 4 Gigabit speed What cable type do you choose? If you need only two fibers and the length is short, you can use zipcord. Breakout cable is larger and more expensive, but for short distances it offers more ruggedness and the ability to be terminated without the need for patch panels or termination boxes, saving that cost. For most backbone cables, distribution cables have a smaller size for the number of fibers, easing pulling of the cable, and are terminated in patch panels or boxes to protect the fibers.

OSP vs Premises Cables Premises Cables Tight buffer Designed for direct termination Requires flame retardance for indoor use - general, riser or plenum ratings Armor may be used for placement with other cables, e.g. underfloor OSP Cables: Loose tube or ribbon High tension rating for pulling or aerial placement Protection against moisture and other environmental factors Armor may be used for ruggedness and protection against rodents OSP vs Premises Cables Requirements for OSP and premises cables are quite different. For OSP cables, ruggedness and protection against environmental factors is top priority. Premises cables are designed first for fire regulations that require flame retardance or low smoke emission. Different cable types are used for specific applications. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Optic Installations -Premises Premises installers need only a termination kit for attaching connectors and a simple test kit for their installations. Working in crowded telecom closets or communications rooms is the norm. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Optic Installations -Premises Premises applications usually mean lots of cables - both copper and fiber - run inside the building in conduit, cable trays or proper hangers and terminated in telecom rooms. FOA Fiber Optic Curriculum ©2012 The FOA

Fiber Optic Installations - Outside Plant Outside plant installations require more hardware (and more investment in the tools and test equipment.) Pullers, splicers, OTDRs and even splicing vans are the tools of the trade for OSP contractors. FOA Fiber Optic Curriculum ©2012 The FOA

evaluation OSP Cables: Loose tube or ribbon High tension rating for pulling or aerial placement Protection against moisture and other environmental factors Armor may be used for ruggedness and protection against rodents

Premises Cables Tight buffer Designed for direct termination Requires flame retardance for indoor use - general, riser or plenum ratings Armor may be used for placement with other cables, e.g. underfloor

By Installation Method Underground in conduit Direct Buried Aerial Submarine

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