optical fiber communication-presented by kiran devkota

Lumbini Net Pvt. Ltd.

Optical Fiber CommunicationKiran DevkotaApril 2nd 2014


Overview

• Fiber optics is a medium for carrying information from one point to another in the form of light.

• Unlike the copper form of transmission, fiber

optics is not electrical in nature.

• A basic fiber optic system consists of a transmitting device that converts an electrical signal into a light signal


Fiber Optic Materials

Silica Fibers• Both core and cladding are of glass.• Very pure SiO2 or fused quartz.• Any other remaining impurities causes attenuation and scatteringPlastic Fibers•Plastic core and plastic cladding. •Flexible and Light.•Widely used in short distance applicationsPlastic-clad Fibers•Glass as core and plastic as cladding


Basic Construction of a Fiber Optic Cable

CoreThis is the physical medium that transports optical signals from an attached light

source to a receiving device. The core is a single continuous strand of high-purity glass or plastic whose diameter is measured in microns

CladdingThis is a thin layer that is extruded over the core and serves as the boundary that contains the light waves (more on this later), enabling data to travel through the length of the fiber.refraction index less than core


Basic Construction of a Fiber Optic Cable

Coating:This is a plastic coating over the cladding to reinforce the

fiber core, help absorb shocks, and provide extra protection against excessive cable bends. It does not have any effect on the optical waveguide properties, though.

Strengthening fibers:These components help protect the core against crushing

forces and excessive tension during installation.Cable jacket:This is the outer layer, or sheathing, of the cable


Total internal reflection

• phenomenon that happens when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface


Advantage and Disadvantage

Advantage• Enormous potential bandwidth• Small size and weight• Electrical Isolation• Signal security• Low transmission loss• Potential low cost

Disadvantage• It requires a higher initial cost in installation• the connector and interfacing between the fiber optic costs a lot• requires specialized and sophisticated tools for maintenance and

repairing


Types of Optical Fiber Single Mode /Multimode

Single-mode fiber• has a small core(8 to 9 microns)

• Keeps the light signals going farther before they need to be beefed up, or amplified

• Used for long distance communication

• Transmit infrared laser light (wave length = 1310-

1650nm)


Types of Optical Fiber

Multimode fiber• Much larger core (50 or 62.5 microns )than

single-mode fiber.• gives light waves more room to bounce around

inside as they travel down the pathused for short distance communication• Transited infrared light (wave length = 850 –

1310nm ) from light emiting diodes (LEDs).


Types of Optical Fiber


Single/Multi Mode Fiber


Attenuation

• The decrease in signal strength along a fiber optic waveguide caused by absorption and scattering is known as attenuation. Attenuation is usually expressed in dB/km.

• Due to attenuation, the power output (Pout) at the end of 1km of optical fiber drops to some fraction (k) of the input power (Pin) i.e. Pout = k.Pin (kless than 1).


Attenuation


Types of connector

LC

Lucent Connector, Little Connector, orLocal Connector


Types of connector

• FC

• Ferrule Connector or Fiber Channel

SC Subscriber Connector [3] orsquare connector [3] orStandard Connector


Types of connector

Angle-polished connectors (APC) and Ultra-polished connetors (UPC)• Insertion Loss

Insertion loss is defined as measurement for the amount of optical power lost through a mated connector pair.

• UPC APC0.2 dB max. 0.35 dB max.

0.09 dB typical 0.15 dB typical

• Return LossReturn loss is a measurement of the light reflected back to the source

at anoptical interfaceUPC APC

- 57 dB min -65 dB min.


Adaptor


SFP

The small form-factor pluggable (SFP) is a compact, hot-pluggable transceiver


SFP

Part No. Package Data Rate

(bps/Hz) Tx(nm)

Pout(dBm)

Sensitivity (dBm)

Temp °C

Reach

APS55123xxLB2 1.25G SFP 1.25G 1550nm DFB

0~5 <-32 0~70℃ 120km

APS55123xxL80 1.25G SFP 1.25G 1550nm DFB

0~5 <-25 0~70℃ 80km

APS31123xxL40 1.25G SFP 1.25G 1310nm FP

-5~0 <-25 0~70℃ 40km


-9~-3 <-25 0~70℃ 20km


-15~-8 <-24 0~70℃ 2km

APS85123xxL05 1.25G SFP 1.25G 850nm VCSEL

-9~-4 <-18 0~70℃ 550 meters


SFP

Transceiver Type: 100_BASE_LX_SFP

Connector Type: LC

Wavelength(nm): 1310

Vendor Name: Raisecom

Vendor Part Number: 03/SS135-D-R

Vendor Serial Number: 112130500711

Fiber Type: Single-Mode

Transfer Distance(meter): 15000

Transceiver Type: 1000_BASE_LX_SFP

Connector Type: SC

Wavelength(nm): 1550

Vendor Name: OEM

Vendor Part Number: APSB53123CDL40

Vendor Serial Number: SG53431400010

Fiber Type: Single-Mode

Transfer Distance(meter): 40000


SFP

Optical High Alarm High Warn Low Warn Low AlarmRx Power Threshold Threshold T hreshold T hreshold

Port (dBm) (dBm) (dBm) (dBm) (dBm)----------------------------------------------------------------------------------------------------------------------------------------------------------25 - 19.3 - 2.9 - 4.9 - 31.5 - 33.926 - 16.9 1.0 0.0 - 23.9 - 26.927 - 3.9 1.0 0.0 - 23.9 - 26.928 - 11.6 1.0 0.0 - 23.9 - 26.9

Optical High Alarm High Warn Low Warn Low AlarmTx Power Threshold Threshold Threshold Threshold

Port (dBm) (dBm) (dBm) (dBm) (dBm)----------------------------------------------------------------------------------25 - 11.8 - 4.9 - 7.9 - 14.9 - 17.926 - 5.2 - 0.9 - 1.9 - 10.0 - 10.927 0.5 5.0 4.0 - 2.9 - 3.928 0.6 5.0 4.0 - 2.9 - 3.9


Types of Optical Fiber Cable

• Distribution cables

• Loose tube cables


Types of Optical Fiber Cable

• Armored Cable:

• Aerial Cables


Loss in 0ptical Fiber Communication

• Loss Inherent to FiberLight loss in a fiber that cannot be eliminated during the fabrication process is due to impurities in the glass and the absorption of light at the molecular level

Splice Loss:• Poor cleave • Misaligned fiber cores • Air gap • Contamination • Index-of-refraction mismatch • Core diameter mismatch


Loss in 0ptical Fiber Communication

Connector Loss:• Dirt or contaminants on the connector (very common) • Improper connector installation • Damaged connector faces • Poor cleave • Misaligned fiber cores • Index-of-refraction mismatch solved by index matching gelBend Loss:• Sharp curves of the fiber core • Displacements of a few millimeters or less, caused by buffer or jacket

imperfections • Poor installation practice Fresnel Reflection:

if the end of a fiber has any kind of air gap, then some of the light traveling from the air to the core, about 4%, is reflected back into the air instead of transmitting/refracting into the core


Loss Calculation

• Fiber loss at the operating wavelengthWavelength (nm) 850 1300 1310 1550Fiber Atten. dB/km 3.5 1 0.3 0.25

• Connector Loss0.3 dB• Splice LossMechanical connection 0.2Fusion splicing 0.1


OTDR (Optical Time Domain Reflectmeter)

• OTDR is a measurement instrument for identifying optic fiber transmission features.

• OTDR sends out a light pulse into connected optic fiber, and receive reflections of events and backward scattering power of pulse in time.

Events• Events refer to any abnormal points causing

attenuation or sudden change of scattering power besides the normal scattering of optic fiber, which include all kinds of losses like bending, connections and ruptures.


OTDR (Optical Time Domain Reflectmeter)

Reflection Events

Reflection is primarily a problem with connectors but may also affect mechanical splice

Properly made fusion splices will have no reflection; a reflection peak indicates incomplete fusion or inclusion of an air bubble or other impurity in the splice


OTDR (Optical Time Domain Reflectmeter

• Non-reflection Events

• Non-reflection events happen at certain points where there is some optic loss but no light

scattering.

• When non-reflection event occurs, a power decline shows on trace.


OTDR

OTDR setup

• Range Length of optic fiber relevant to the trace• Pulse Width of laser pulse sending out from OTDR to optic fiber. With

narrow pulse width, there will be higher resolution and smaller dead zone, however, the dynamic range will be decreased

•

•• Average Time To select suitable testing time. in case of measurement of long-

distance optic fiber, long average time should be selected in order to review events at long-distance end

• Wave length To select laser wave length for measurement• Measurement Mode To select mode for measurement. Averaging and Real time

mode• VFL Power on or off visible• Length Units To select length units


Tools

• Optical power meter (OPM) used to measure the power in an optical signal. The term usually refers

to a device for testing average power in fiber optic systemsFiber Optic Fault Locator• used to locate the broken points of optical fiber, connector

inspection and tracing of fibers.Optical fiber identifierdesigned to detect optical signals without disrupting traffic

Optical Fiber cleaning


THANK YOU

optical fiber communication-presented by kiran devkota

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