Anritsu MT9812B, Руководство по эксплуатации, Страница: 124 / 144

Section 6 Performance Test
6-6
.
6.2.3 Return Loss
Optical isolator
Optical sensor and Power meter
Total-reflection
optical fiber
Optical directional
coupler MN9604C
Light source
MU952501A
Device Under Test (DUT)
Fig. 6-5
Step Operation
1 Set up a measurement system like that shown in figure, above.
2 Input the light of about –20 dBm with the total-reflection opti-
cal fiber attached to the measuring system.
3 Set the power meter to Relative measurement.
4 Connect the optical directional coupler to the DUT, detaching
the total-reflection optical fiber, and perform measurement us-
ing the power meter.
5 The absolute value of the power meter display becomes the re-
turn loss.
6.2.4 Noise Level
Variable optical attenuator
MN9625A
×
2
Light source
MU952501A
Device under test (DUT)
Optical fiber Optical fiber
Fig. 6-6
Step Operation
1 Set up a measurement system like that shown in figure, above.
2 Set the bandwidth and number of averagings of the DUT to 1
Hz and 10, respectively.
3 Insulate the DUT from the light for performing the zero-level
calibration.
4 Adjust the optical attenuator so that the indicator of the DUT
shows –80 dBm.
5 Set the DUT for P-P measurement (% display), and perform the
measurement for about 30 minutes.
6 Noise level can be calculated using the P-P value after the
completion of the measurement, using the following formula;
Formula: Noise level (dBm)
= –80+log
10
([100 - Measured value]/100)