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OTDR Working Principle
The OTDR’s operating principle is based on the measurement of the Raleigh Backscattering Signal, generated by
sending a high power optical pulse from the OTDR through the optical fiber. Light
is reflected back to the OTDR.
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This backscattered light is measured by the sensitive optic receiver, converted to digital form and averaged to improve the signal to noise
ratio
The resulting signal forms a graph called a TRACE. The trace is a visual representation of the backscattering coefficient created by the OTDR to determine the “events.” The trace
shows the “events” on the fiber optic link such as breaks, splice loss, bends,
attenuation and distance
OTDR MACHINE WINDOW MENU
5 Basic menu every OTDR must have•Trace title•Menu bar•Button toolbar•Information Panel•Trace window
,
TRACE TITLE
TRACE WINDOW
BUTTON TOOLBARMENU BAR
INFORMATION PANEL
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GENERAL OTDR FEATURES
OTDRS CAN BE CATEGORIZED BY
•Their operating wavelength, •Their dynamic range (the length of optical fiber link over which they will operate),•Their sensitivity or resolution. OTDR sensitivity is its ability to differentiate between closely spaced events.
OTDR OPERATIONAL TOOL BAR
THESE ARE THE TOOLS FOUND ON THE BUTTON TOOL BARS FOR THE
SMOOTH OPERATION AND ANALYSIS OF THE OTDR TRACE
Attenuation measurement by straight-line trace approximation [D]
Restores all trace scales [ALT+BKSP]
Opens up the measurement parameters window
Starts the measurement process in real time
mode [ENTER]
Vertical zoom out control [CTRL+V]
Automatic trace analysis [A]
Deletes all the marks between markers [ALT+DEL]
Horizontal zoom out control [CTRL+H]
Applies a template to current trace [CTRL+T
Inserts trace from clipboard onto host trace [SHIFT+INS]
Trace information [I]
Reflection coefficient measurement [R]
OF refractive index adjustment [N]
Inserts a mark for the current mode and marker position [CTRL+ENTER
Opens a table of the current trace marks [Т]
Copies current trace to clipboard [CTRL+INS]
Deletes inserted trace [CTRL+DEL]
Horizontal zoom in control [H]
Vertical zoom in control [V]
Attenuation measurement in OF junctions [S]
Attenuation measurement between two points mode [P]
Starts the measurement process in Normal mode
Saves a current trace [CTRL + S]
Prints a current trace
Opens a previously saved trace [CTRL + O]
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OTDR Operations
In addition to the trace analysis, the OTDR will determine the following Distance of the fiber linkAttenuation of the fiber linkThe fibers ORLSplice lossConnector loss
WHAT TO OPERATE ON OTDR
Every OTDR user must know how toadjust the distance to be displayed on the screenadjust the dB for vertical scale representationsselect various wavelengthsadjust the transmission pulse widthsselect a vertical position on the screen using the curserprint, save, and execute other file commands
OTDR ACCEPTANCE TEST
Acceptance testing provides a quality assurance notification to the installation crew that the cable meets the manufacturing standards, and is not damaged. It ensures that:•the cable meets the manufacturer's specifications for optical attenuation requirements•the footage of the reel is correct•the cable remains undamaged from shipment and handling