2.7 Precautions at Measurement
2-17
2
Using Multimode (MM) fiber (50 µm core diameter)
There are two insertion methods for multimode fiber: 1. Steady state
mode excitation when light from an LED or VCSEL is propagated, and 2.
Fixed mode excitation when using an excited fiber (GSGG) for measuring
optical loss of an LD. To measure light in these excitation states, press
F1
Measure Mode
and set
f5 MM Mode
to “On”.
When setting
f5 MM Mode
to On for the following measurements:
●
When measuring faceted light sources such as LEDs, VCSELs, etc.
●
When measuring in the recommended launch mode using a dummy
fiber patch cord (GSGG)
When setting
f5 MM Mode
to Off:
To measure light in the limited excitation states, press
F1 Measure Mode
and set
f5 MM Mode
to “Off”.
●
When measuring optical output of LD modules without normal
distribution (excitation) using dummy fiber patch cord for optical loss
measurement (GSGG etc.)
Note:
The GSGG is a device with a fixed multimode fiber excitation
condition. It is configured using a combination of different
multimode fibers.
The 14 dB loss when connecting 50
µ
m/125
µ
m multimode optical fiber
degrades the light reception sensitivity.
The MS9740B has an MM mode function to correct loss when connecting
50
µ
m/125
µ
m multimode optical fiber and to display the level.
The optical loss level is corrected when the MM mode is On. It corrects the
level by 14 dB (sum).
However, level display errors occur if loss is not 14 dB according to the
excitation conditions of multimode fiber.
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