OTR 700 User's Guide Rev02 11/2016
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Least Squares Approximation (LSA)
Least Squares Approximation (LSA) Splice loss method gives the user a visual aid in setting splice loss areas.
This method can be more accurate by affording the ability to see the slope of the splice loss areas, however:
it can also supply a reading with greater error if not used properly. The splice loss lines must be set to overlay
the backscatter of a trace without over lapping any other events. Unlike basic splice lose, LSA measurement
areas are drawn as straight lines without regard to the undulations of the back scatter
8.11 Loss Measurement Settings
Optical Return Loss
This Optical Return Loss (ORL) is separate from the event ORL (Reflectance) that is displayed in the event
analysis under the TYPE header for an individual event. The measurement displayed in the loss measurement
area of the main OTDR screen and in the L (Linki) row in the TYPE column is an optical return loss based on
the entire link. It is the total accumulated light reflected back to the source along the fiber optic link.
Basic Splice Loss
Splice Loss method is meant to be used in noisy environments when it is difficult to attain an LSA area that
lays flat on the back scatter before and after the cursor. This method takes an average of the selected points
before and after the active cursor and uses this average to make a good estimation of the event loss. This is an
estimation but this method may be more accurate than LSA Splice Loss method in noisy environments.
When using the splice loss It is necessary to set the splice loss areas in clear backscatter. (areas that do not
consist of other events) For accurate splice loss measurements, set a cursor at the beginning of an event
and set splice loss measurement areas as shown in Fig. 8.6. Splice loss measurement areas will follow the
undulations of the back scatter line unlike LSA areas.
Chapter 8 OTDR Operation
Touch Screen Tip
The loss measurement/LSA areas may only be set with the key pad. Use the touchscreen menu to
enter the LSA settings function, but once there, use the key pay to adjust the areas as described. It is
necessary to be zoomed in on an event to set the loss measurement areas.
Setting Splice Loss Measurement Areas
To set the basic splice loss measurement/ LSA ares, the OTDR must be in Splice AVG or Splice LSA mode.
To adjust the splice loss areas around the cursors, press the menu button, highlight the LSA icon and press
select. The splice lose position indicator will be displayed at splice loss position number 1 as indicated in Fig.
8.6. Use the left and right buttons to adjust the loss measurement area. Press the select button to move the
splice lose position indicator to the position number 2, set the area and continue with positions 3 and 4 in the
same manner. Press select when done with position number 4 to hide the splice lose position indicator and
reset the focus of the keyboard back to the cursors. Press the menu button at any time to escape the splice
lose settings sequence.
Note
It is necessary to set these areas in clear backscatter to acquire the most accurate measurements, they
must not include other events.
