User`s guide

C Specifications Definition of Terms / Measurement Conditions

196 E6000C Mini-OTDR User’s Guide, E0302

Measurement: Select Optimize Resolution for best

accuracy. Since the precise location of the front panel

connector is usually not directly accessible, use a short

reference fiber (for example, 100 m, to exclude any

influence from distance scale error) with known length L

and open end to create a reflective event. Then measure

the length of the fiber by determining the location of the

reflective event L

OTDR

as shown in Figure 4. Then

calculate the distance offset error

∆L

by subtracting the

measured length from the known length, L.

and:

L = known length of the fiber = (c T)/N.

c = speed of light in vacuum

T = time of flight between the two locations on the

reference fiber, measured at the wavelength of the OTDR

N = group index of the fiber (use the OTDR’s

→group

index setting)

OTDR

= the distance measured with the OTDR, at the

given

→group index setting

where

OTDR

ref

LLL −=∆

L =